vi
i

Materials Science and

Engineering Laboratory

FY 2005 Programs and

Accomplishments

Ceramics, Materials

Reliability, Metallurgy,

NIST Center for

Neutron Research, and

Polymers Divisions

Richard F. Kayser, Director

Stephen W. Freiman, Deputy Director

NISTIR 7248

December 2005

National Institute of

Standards and Technology

William Jeffrey

Director

Technology

Administration

Michelle O’Neill

Acting Under Secretary of

Commerce for Technology

U.S. Department

of Commerce

Carlos M. Gutierrez

Secretary
ii

Certain commercial entities, equipment, or materials may be identified in this document in order to

describe an experimental procedure or concept adequately. Such identification is not intended to imply

recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended

to imply that the entities, materials, or equipment are necessarily the best available for the purpose.
iii

Table of Contents

Table of Contents

Director’s Message ...................................................................................................................1

Materials Science and Engineering Laboratory Organization Chart .........................................2

Year in Review

Ceramics Division ...............................................................................................................3

Materials Reliability Division ...............................................................................................5

Metallurgy Division .............................................................................................................7

Polymers Division ...............................................................................................................9

NIST Center for Neutron Research ................................................................................. 11

Nanometrology ........................................................................................................................13

Mechanical Metrology for Small-Scale Structures ...........................................................14

Nanomechanics: Atomistics in Modeling and Experiments ............................................. 15

Modulus Mapping at the Nanoscale ..................................................................................16

Reference Specimens for SPM Nanometrology ..............................................................17

Nanotribology and Surface Properties.............................................................................. 18

Chemistry and Structure of Nanomaterials ......................................................................19

Nanotube Processing and Characterization ......................................................................20

Carbon Nanotube Applications: The Role of Nanotube Alignment ................................. 21

Combinatorial Adhesion and Mechanical Properties ........................................................ 22

Soft Nanomanufacturing ...................................................................................................23

Defects in Polymer Nanostructures..................................................................................24

Critical Dimension Small Angle X-Ray Scattering ...........................................................25

Nanoimprint Lithography ..................................................................................................26

Nanomagnetodynamics .....................................................................................................27

Materials for Ultra-Low-Field Magnetic Sensors.............................................................28

A New Type of Antisymmetric Magnetoresistance

in Materials with Perpendicular Anisotropy ......................................................................29

Nanostructure Fabrication Processes:

Surface & Growth Stress During Thin Film Electrodeposition ........................................30

Multiscale Modeling of Quantum Dots in Semiconductors ...............................................31

Brillouin Light Scattering:

Dynamic Elastic and Magnetic Properties of Nanostructures .........................................32
iv

Table of Contents

Materials for Electronics ......................................................................................................... 33

Multifunctional Electronic Ceramics................................................................................. 34

Spectroscopy, Diffraction, and Imaging of Electronic Materials ......................................35

Theory and Modeling of Electronic Materials .................................................................. 36

Advanced Materials for Energy Applications................................................................... 37

Polymer Photoresists for Nanolithography .......................................................................38

Organic Electronics...........................................................................................................39

Nanoporous Low-k Dielectric Constant Thin Films ......................................................... 40

Electrical Methods for Mechanical Testing ......................................................................41

Thermochemical Metrology of Interfacial Stabilities ........................................................ 42

Combinatorial Metal Selection for Catalytic Growth

of ZnO Semiconductor Nanowires ...................................................................................43

Advanced Processes and Materials for On-Chip Interconnects ......................................44

Pb-free Surface Finishes: Sn Whisker Growth................................................................45

Materials for Advanced Si CMOS ....................................................................................46

Metrology and Standards for Electronic and

Optoelectronic Materials...................................................................................................47

Nano-Structured Materials for Sensors and

Ultra-high Density Data Storage ......................................................................................48

Advanced Manufacturing Processes ......................................................................................49

Mechanisms for Delivery of Thermodynamic and Kinetic Data .....................................51

FiPy: An Adaptable Framework for Phase Field

and Level Set Modeling ....................................................................................................52

Metrology Tools to Accelerate Industrial Development

of Solid State Hydrogen Storage Materials ......................................................................53

Fundamental Nature of Crack Tips in Glass..................................................................... 54

Hardness Standardization: Rockwell, Vickers, Knoop .....................................................55

NIST Combinatorial Methods Center

Pioneer and Partner in Accelerated Materials Research ........................................... 56

Polymer Formulations:

Materials Processing and Characterization on a Chip ...................................................... 57

Quantitative Polymer Mass Spectrometry ........................................................................58

Standard Tests and Data for Sheet Metal Formability .....................................................59

Microstructural Origins of Surface Roughening

and Strain Localizations ....................................................................................................60

Underlying Processes of Plastic Deformation in Metal Alloys ........................................61

Evaluation of Friction Behavior During Metal Forming ....................................................62
v

Biomaterials .............................................................................................................................63

Combinatorial Methods for Rapid Characterization

of Cell-Surface Interactions..............................................................................................64

Cellular Level Measurements ........................................................................................... 65

Cell Response to Tissue Scaffold Morphology .................................................................66

3-Dimensional In Situ Imaging for Tissue Engineering:

Exploring Cell/Scaffold Interaction in Real Time .............................................................67

Broadband CARS Microscopy for Cellular/Tissue Imaging ............................................ 68

Response of Tissues and Tissue-Engineered Constructs

to Mechanical Stimulation .................................................................................................69

Mechanical Behavior of Tissue .........................................................................................70

Materials Design for Biomechanical Structures ...............................................................71

Molecular Design and Combinatorial Characterization

of Polymeric Dental Materials .......................................................................................... 72

Safety and Reliability ...............................................................................................................73

Analysis of Structural Steel from the World Trade Center ...............................................74

Infrastructure Reliability: Charpy Impact Machine Verification ......................................75

Standard Test Methods for Fire-Resistive Steel ...............................................................76

Frangible Bullets and Soft Body Armor ............................................................................77

Pipeline Safety: Corrosion, Fracture, and Fatigue ...........................................................78

Polymer Reliability and Threat Mitigation.........................................................................79

Facilities and Capabilities

Databases..........................................................................................................................91

Recommended Practice Guides ..............................................................................................92

Table of Contents
vi

DIRECTOR’S MESSAGE

MSEL works with industry, standards bodies,

universities, and other government laboratories

to improve the nation’s measurements and

standards infrastructure for materials.

Welcome to the Materials Science and

Engineering Laboratory (MSEL).

MSEL provides technical leadership

for the nation’s materials measurement and standards

infrastructure, using expertise in ceramics, polymers,

metallurgy, neutron characterization, and materials

reliability to anticipate and respond to industry and national

needs in areas such as microelectronics, automotive, and

health care. The Laboratory also houses the Nation’s only

fully equipped cold neutron research facility, the NIST

Center for Neutron Research.

This document provides a summary of accomplishments

that we hope will communicate our commitment to the

needs of our customers. Our projects fall into five broad

technology focus areas: Nanometrology; Materials

for Electronics; Advanced Manufacturing Processes;

Biomaterials; and Safety and Reliability. The sections

on each of these areas begins with a brief program

summary.

Richard F. Kayser

Director

Materials Science and Engineering Laboratory

1
National Institute of Standards and Technology

Materials Science and Engineering Laboratory

2
Year in Review

Ceramics Division

I

t has been an exciting year in the Ceramics

 Division for forging new partnerships with industry

and other national laboratories, initiating research

efforts relevant to emerging nanomaterial systems, and

strengthening our ongoing core metrology, data, and

standards activities closely aligned with the mission

of NIST. Our accomplishments predominately relate

to Nanometrology and Materials for Electronics, two

of the five program areas in the Materials Science and

Engineering Laboratory (MSEL). To crown these

achievements, our excellent technical staff members

have been honored with a host of prestigious NIST

and external awards.

A concerted effort to partner directly with Sematech

has led to research activities in advanced metrology to

address pressing needs in next-generation semiconductor

products. One project is aimed at developing metrology

for accurate thin film characterization using x-ray

reflectometry, while the other is focused on applying

novel combinatorial and synchrotron methods to

optimize the interfaces in advanced high-k dielectric

CMOS gate stacks critical to the semiconductor

industry’s 21st century technology roadmap.

A partnership with the National Cancer Institute

(NCI) was initiated this year. NCI has awarded NIST

a three-year research grant to collaborate with NCI’s

new Nanotechnology Characterization Laboratory in

the development and application of nanoparticle-based

systems for cancer prevention, detection, and therapeutics.

The Ceramics Division is contributing its long-standing

expertise in nanoparticle metrology to this effort by

developing measurement methods and protocols for

characterizing the size, size distribution, and dispersion

of inorganic and organic nanoparticles in aqueous

solutions compatible with body fluids.

The Ceramics Division has maintained its strong

commitment to two outstanding long-term partnerships

aimed at providing the reliable, high-quality data that is

fundamentally essential for advanced technology research

and development: the celebrated NIST–American

Ceramic Society collaboration on phase equilibria

diagrams and the collaboration with FIZ Karlsruhe

(Germany) on the renowned FIZ–NIST Inorganic

Crystal Structure Database.

Ongoing partnerships at DOE synchrotron user

facilities have continued to provide high-quality, unique

capabilities for structural and chemical characterization

of advanced materials. In a joint effort with Sandia National

Laboratory, considerable progress has been made to

establish a synchrotron-based variable kinetic energy XPS

facility at the National Synchrotron Light Source (NSLS),

Brookhaven National Laboratory (BNL), the first of its

kind in the U.S. For the fifth consecutive year, the

soft x-ray beamline jointly developed by NIST and

Dow Chemical Co. was the most productive soft x-ray

facility at NSLS, yielding over 25 publications. Our

long-term partnership in UNICAT, a collaborative access

team at the Advanced Photon Source (APS), Argonne

National Laboratory, has continued to support and improve

numerous scattering and diffraction techniques. This

partnership will undergo a transition next year as operation

and management of the beamline will be assumed by

the APS.

The Ceramics Division has continued to support

the upgrade and expansion of its unique measurement

capabilities. Instruments in the high-resolution x-ray

metrology and nanotribology facilities in the NIST

Advanced Measurements Laboratory (AML) became fully

operational this year and have already yielded results with

unprecedented resolution. With the recent modernization

of two beamlines at NSLS dedicated to extended x-ray

absorption fine structure (EXAFS) and x-ray photoelectron

spectroscopy (XPS), the Ceramics Division and its

partners have established the capability to perform

x-ray absorption spectroscopy spanning all elements in

the periodic table. A three-year SBIR project has led to

the development of a state-of-the-art multi-element detector

at the NSLS soft x-ray beamline, providing an order

of magnitude increase in data collection rates.

We represent MSEL in the AML, the world’s premiere metrology

laboratory.

There have been numerous notable scientific

achievements across the Division this year; following

are several representative research highlights. Ten

international leaders worked together to create the

IUPAC–NIST Crystal Phase Identifier standard to uniquely

identify any chemical compound appearing in an electronic

database. This landmark standard is a major step forward

towards the worldwide interoperability of crystal structure

databases. In collaboration with BNL scientists, our unique

near-edge x-ray absorption fine structure metrology facility

at the NSLS has been employed to characterize the surface

order and structure of carbon and boron nitride nanotubes,

3
resulting in four refereed journal publications. A feature

article reviewing the state-of-the-art in characterizing

ceramic materials by x-ray and neutron small-angle

scattering was published in the Journal of the American

Ceramic Society (A. Allen, J. Am. Ceram. Soc., 88,

1367, 2005). The first computational model to correlate

nanoscale chemical ordering, defects and properties

in relaxor ferroelectrics, materials of choice for sonar

and medical imaging transducers, was constructed,

coupling first principles calculations and molecular

dynamics simulations. Devices for calibrating force in

commercial nanoindentors, instruments for measuring

mechanical properties at the nanoscale used by thousands

of researchers worldwide, have been developed jointly

with scientists in the NIST Manufacturing Engineering

Laboratory. These force calibration cells will be produced

in collaboration with the major nanoindentor instrument

manufacturers.

In a far-reaching effort to respond to the anticipated

metrology and standards needs for next-generation

advanced materials, particularly for nanotechnology

applications, several new research efforts were initiated

this year. In the area of CMOS technology, measurement

methods are being developed and applied to evaluate

thermal and electrical stability at interfaces in high-k

dielectric gate stack structures and to characterize the

electronic structure and chemical bonding in these

structures at nanometer depth sensitivity. Metrology based

on Raman spectroscopy and x-ray topography is under

development to evaluate the stress state and defect

structures in strained silicon layers for high-performance

MOSFET devices.

Multifunctional oxide materials, wherein the

functional response of one constituent phase/subsystem

is generated by the response of another phase/subsystem

to an external field, offer the potential for integrating

electronic, magnetic and optical devices on a single chip.

A combined experimental/theoretical modeling effort is

underway to analyze the formation of self-assembled

epitaxial nanostructures of multifunctional oxides,

measure the functional properties at the nanoscale, and

ultimately correlate the responses to the nanostructural

architectures. Foundational pre-standards research on

theoretical structural models for extracting film properties

from x-ray reflectometry measurements and on reference

cantilevers for calibrating AFM force measurements

has begun. A multi-year project was initiated to develop

an in situ nanocalorimetry technique with adequate

sensitivity to detect hydrogen desorption in hydrogen

storage materials and interfacial reactions in multilayer

structures in collaboration with world leaders in

nanocalorimetry from the University of Illinois.

It is a pleasure to acknowledge the numerous

prestigious honors bestowed upon the staff this year.

Dr. Daniel Fischer was one of only twelve individuals

to receive the coveted Arthur S. Flemming Award

honoring outstanding Federal Government employees.

Dr. Fischer was cited for his pioneering work in

developing and utilizing a first-in-the-world facility for

soft x-ray absorption spectroscopy that has enabled key

scientific and technological advances in cutting-edge

and emerging technologies of paramount importance

to the Nation. For these exemplary achievements,

Dr. Fischer was also awarded the Department of

Commerce Gold Medal, the highest honorary award

granted by the Secretary of Commerce.

Dr. Daniel Fischer

received the Arthur S.

Flemming Award and

the Department of

Commerce Gold

Medal award.

The Silver Medal, the second highest Department

of Commerce honorary award, was given to a NIST team,

including Dr. Douglas Smith, for their technical innovation

that revolutionized the realization of the unit of force

at the micro- and nanoscales. Dr. Vicky Karen and

Dr. Alec Belsky (Technology Services) received the

Bronze Award, the highest honorary recognition presented

by the NIST Director, for their development and

application of scientific algorithms and functional software

embodied in the Inorganic Crystal Structure Database

used for phase identification in commercial SEMs.

The esteemed NIST Edward Uhler Condon Award

recognizing distinguished achievement in scientific and

technical writing was awarded to Dr. Ronald Munro for

his eloquent and systematic exposition of data evaluation

as a scientific discipline. Nearly 1500 printed and 40,000

electronic copies of NIST Recommended Practice Guide

“Data Evaluation Theory and Practice for Materials

Properties” have been requested across the world, attesting

to the broad appeal and applicability of the work.

We remain committed to providing high-quality

metrology tools, standards, and data to support the

development and implementation of advanced ceramic

materials, components, and devices in the electronics,

photonics, energy, and healthcare technology sectors.

Debra L. Kaiser

Chief, Ceramics Division

Year in Review

4
Year in Review

Materials Reliability Division

on Measurement Issues in Single Wall Carbon Nanotubes

(SWCNTs) in January 2005. Over 80 leading researchers

attended from industry, academia, and other government

agencies to discuss two significant measurement

problems: how to determine nanotube purity and how

to ensure nanotubes are well dispersed for device

processing. Based on information provided from

attendees, we are currently drafting a NIST Recommended

Practice Guide to help industry with these problems.

The collected data will also serve as the basis for an

upcoming IEEE nanotube measurement standard.

Recognition

Dr. Vinod K. Tewary was presented the Eric Reissner

Medal at the annual International Conference on

Computational and Experimental Engineering and Sciences

meeting held July 2004 in Portugal. He received this

award for sustained and significant contributions

to mechanics at small-length scales.

Dr. Donna C. Hurley was named a Fellow of the

Institute of Physics (U.K.) in recognition of her status

in the physics community and her contribution to the

Institute as a member of the Editorial Board of the

Journal of Measurement Science & Technology.

Division Highlights by Focus Area

Materials for Micro- and Optoelectronics

The International Technology Roadmap for

Semiconductors recognizes the importance of

metrology to the advancement of the industry and

calls specifically for solutions to the near-term

challenge (through 2009) of achieving necessary

reliability. Our project in this area focuses on

development of test and detection methodologies for

mechanical reliability of dimensionally-constrained

materials, as well as on learning more of the science

behind the observed mechanical behavior.

Highlight

This year a key advance was made in the

first known demonstration of time- and spatiallyresolved measurements of Joule heating in patterned

metal interconnects, using alternating currents. The

measurement is made with an atomic force microscope

(AFM) that uses the probe tip as both a point-source heater

and a resistive element in a Wheatstone bridge circuit.

The left figure shows a thermal AFM image

depicting temperature differences measured at the

surface of a non-passivated Al interconnect carrying

an rms AC current density of 7 MA/cm2. A rapid

decrease in temperature with distance away from

the interconnect is apparent. The right figure shows

The Materials Reliability Division focuses

on reliability issues in microelectronics,

nanocharacterization, biomaterials metrology,

and infrastructure reliability. Because we do

not concentrate on a specific class of material,

the division takes advantage of the specific

expertise and complementary skills in the other

MSEL Divisions by running many joint projects.

The Materials Reliability Division’s mission is to

develop and disseminate measurement methods

and standards enhancing the quality and reliability of

materials for industry. Our work spans a wide range

of materials, with a dimension span that extends from

nanometer scale devices, carbon nanotubes, and single

cells — to tall buildings, gas pipelines, and bridges.

Recent Workshops

Pipeline Coatings

The proceedings of

the 2004 workshop

Coatings for Corrosion

Protection: Offshore

Oil and Gas Operations

Facilities, Marine Pipeline,

and Ship Structures has

been mailed to the 150

participants and to key

libraries around the country.

This report is an important component of our support

for the pipeline industry under the Pipeline Safety and

Improvement Act of 2002 (HR 3609). Cosponsorship of

the workshop (along with the Office of Pipeline Safety in

DoT, DoI, and various academic and industry groups)

helps drive improvements in safety in the pipeline industry.

Acoustic Propagation

With NIST’s Center for Theoretical and Computational

Materials Science (CTCMS), we sponsored a workshop

on Computational Tools for Modeling Acoustic

Propagation in Real-World Materials (CTAP) in

August 2004. Researchers came together to discuss

modeling requirements for non-destructive evaluation,

medical ultrasound, underwater acoustics, geophysics,

and atmospheric acoustics. Despite these very different

uses of acoustics, the attendees faced similar modeling

challenges and were interested in pursuing collaborative

solutions with NIST’s support.

Carbon Nanotubes

Along with other researchers in MSEL and CSTL,

we co-organized the 2nd Joint NASA–NIST Workshop

5
Year in Review

the temperature variation at one position of the AFM

probe, over 0.2 s, for a 10 Hz current; the oscillation is

approximately 15 °C. These temperature measurements

are used to quantify cyclic thermal strains applied to

interconnects for the purpose of conducting quantitative

thermal fatigue tests.

Key Paper

R.R. Keller, D.T. Read, and R. Mahajan, “Report of

the Workshop on Reliability Issues in Nanomaterials,”

NIST Special Publication, in BERB (June 2005).

This report establishes us as a leader in the field of

reliability issues in nanomaterials.

Nanocharacterization

New measurement techniques play a key role in the

development and commercialization of nanotechnology.

Reliable manufacturing of nanoscale products demands

vast improvements in our ability to measure material

dimensions, characteristics, and structures. In particular,

measurement of mechanical properties on the nanoscale

is critical for fabricating structures with high-aspectratio features and ultra-thin and/or multilayer films.

used BLS to detect low-frequency vibrational modes

in nanoimprinted polymeric lines, demonstrating the

ability to measure elasticity of sub-100 nm features.

Key papers on these subjects have been published in

Nanotechnology, Advanced Engineering Materials,

and Applied Physics Letters.

Mechanical Behavior of Biological Materials

The medical research community recognizes a need

to understand the role that the mechanical behavior

of biological materials play in normal and diseased

tissues. We use a multi-scale approach to elucidate

the mechanical behavior of individual cells and

constructs of a single type of cell, and different cells

in concert. We define mechanical behavior as the

mechanical properties (e.g., stress, strain, modulus)

and the measured response to mechanical stimulus

(e.g., change in phenotype, proliferation, signaling

production). At present, our focus is on measuring

cell response by developing specialized bio-MEMS

devices or with an optical trap, designing and

developing specialized bioreactors for tissue-engineered

constructs, and measuring mechanical properties of

membrane-like tissue.

Infrastructure

The nation’s

infrastructure

continues to age

and is becoming

more vulnerable

to catastrophic

failures, both

intentional and

unintentional.

In response, we

develop better

measurement

technology for

determining a

material’s

characteristics or

for assessing the

sensitivity to failure. In FY05 we expanded our efforts

on pipeline safety by developing fatigue data on new

and field-damaged pipe, advancing the procedures for

crack-tip opening angle (CTOA — a measure of the

resistance to crack extension) testing, and holding

workshops. The Charpy SRM program had over

850 customers in FY05, and we organized and

contributed to an international workshop on Charpy

test procedures. We finished measuring properties of

steels used in the World Trade Center as part of the

NIST-led study (reports released Summer 2005),

and are looking at the issues that impede the use

of fire-resistant steel.

Thomas A. Siewert

Acting Chief, Materials Reliability Division

To investigate elasticity at the nanoscale, we are

pursuing two techniques, atomic force acoustic

microscopy (AFAM) and Brillouin light scattering

(BLS), to measure Young’s modulus and Poisson’s

ratio. This year, we successfully transitioned the

AFAM technique from quantitative measurements at a

single point to elastic modulus maps for an entire film

(see figure for contact stiffness images of a composite

and a microelectronic test structure). In addition, we

6
Year in Review

Metallurgy Division

now taken an academic position at Purdue University.

Frank Gayle has assumed the position of Acting Chief.

This year we reorganized into four technical groups,

each consisting of about 10 staff members and a like

number of guest researchers.

■ The Thin Film and Nanostructure Fabrication

Group performs cutting edge research in fabrication

techniques that range from electrochemical processing

to vapor–liquid–solid growth of nanowires.

■ The Thermodynamics and Kinetics Group develops

new theory, simulation methods, and data for

predicting and controlling phase transformations

during materials fabrication processes.

■ The Magnetic Materials Group develops new

materials and metrology that allow magnetic devices

and sensors to be created at smaller size scales and

with greater sensitivities.

■ The Materials Performance Group develops new

theory and measurements for characterizing the

mechanical behavior of materials, with applications

as varied as sheet metal forming and critical

infrastructure protection.

Division Highlights

By virtue of the interdisciplinary nature of materials

problems, teams are formed across the Division,

MSEL, and NIST, and, in most cases, with external

partners in order to meet our project goals. A few

highlights of the past year are presented here, grouped

by focus areas.

Safety and Reliability

The nation’s infrastructure continues to age and

is ever more vulnerable to catastrophic failures,

whether accidental, intentional, or due to forces of

nature. To address infrastructure vulnerability issues,

we have started a number of projects, several in

close collaboration with the Materials Reliability

Division (MRD).

This year, NIST completed the three-year

Investigation of the World Trade Center Disaster.

A critical aspect of the investigation was the

metallurgical analysis of the recovered structural

steel performed by the Metallurgy Division with MRD.

We issued six reports totaling 1500 pages, and we

continue to work on issues impeding the use of

fire-resistant steel.

In FY05 we expanded our efforts on pipeline safety

in a project working with DoT’s Office of Pipeline

The Metallurgy Division mission is to provide critical

leadership in the development of measurement

methods, standards, and fundamental understanding

of materials behavior needed by U.S. industry.

In extensive collaborations with industry and other

agencies, this year we have focused on complex

metallurgical issues in microelectronics, magnetics,

automotive, and civil infrastructure areas.

I

n this summary, we describe highlights of the past

 year, as well as demonstrate how the capabilities of

the NIST Metallurgy Division are being used to solve

problems important to the national economy and the

materials metrology infrastructure.

Establishing Priorities

We examine a wide range of possible research

topics and make choices for our research portfolio

based on well-tested criteria: the match to the NIST and

Division missions, the magnitude and immediacy of the

need, whether our contribution is critical for success,

the anticipated impact relative to our investment, our

ability to respond in a timely fashion with high-quality

output, and the opportunity to advance mission science,

particularly in areas we believe are important for the future.

We establish our research priorities through extensive

interaction with U.S. industry and other federal agencies,

using a variety of methods, including roadmapping

activities, workshops, technical meetings, standards

committee participation, and consultation with scientific

and technical leaders. A key aspect is translating our

fundamental science into a form useful to our partners,

integrating measurements, standards, software tools,

and evaluated data as needed to solve industry needs.

We prefer to work in rapidly evolving technologies,

where advances in measurement science are needed

to understand the limitations on system behavior and,

therefore, where our contributions are likely to have

an impact on the course of technology. For NIST as

a whole and the Metallurgy Division in particular, we

are committed to having an impact on nanotechnology,

homeland security, health care, and the materials

infrastructure required for advances in information

technology. Over the last two years, we have shifted

substantial resources into the areas of nanomagnetics,

nanomechanics, nanostructure fabrication, and critical

infrastructure protection.

Division Organization

Carol Handwerker led the Division as Chief for the

past nine years. Unfortunately for the division, she has

7
Year in Review

Safety and DoE, with MRD focusing on crack arrest

behavior, and Metallurgy addressing corrosion issues,

including topics arising at a Metallurgy-organized

Pipeline Coatings Workshop held at NIST.

Advanced Manufacturing Methods

A software tool, FiPy, for simulating phase

transformations was released to the public. FiPy

gives materials scientists, physicists, and chemists

the ability to simulate phase transformations using

state-of-the-art, sophisticated numerical techniques

for partial differential equations that allow dramatically

faster solutions to be found over larger physical

domains and for longer elapsed simulation times.

NUMISHEET, a triennial international conference on

simulation techniques for sheet metal forming, was held

in Detroit in August 2005. Division scientists served on

two organizing committees, gave a plenary lecture, and

several additional invited talks. An integral part of this

conference is a round-robin simulation exercise where

modeling groups try to predict the final sample shape

from a prototypical forming operation. MSEL played

the key role in providing new benchmark data using

its unique capabilities for in situ and ex situ stress

measurement. Through thickness residual stresses

were measured at the NCNR, and surface stresses in a

sheet under load in a die were measured using a newly

developed X-ray stress measurement system integrated

into our metal forming machine.

Nanometrology

A new magnetoresistance (MR) effect discovered

this year by scientists in the Metallurgy Division is

antisymmetric with respect to magnetic field. This new

MR effect is due to the presence of circulating currents

created around domain walls when the magnetization

vector, current direction, and domain wall are mutually

perpendicular. This effect may provide device

designers with much more flexibility in designing

magnetic switches and memory.

A new strategy for selecting appropriate catalytic

metals for vapor–liquid–solid growth of ZnO

nanowires with specific semiconducting properties was

developed by combining thermodynamic information

from phase diagrams with a high-throughput

(combinatorial) approach recently demonstrated by

the MSEL Metallurgy Division for metallizations to

wide-band-gap semiconductors.

Materials for Microelectronics

Spontaneous formation of tin whiskers on thin films

of lead-free solder is an enormous reliability issue in the

conversion of microelectronics to lead-free solders.

The mechanism responsible for the nucleation and

growth of Sn whiskers is a matter of considerable

debate. Our research this year has eliminated several

of the possible mechanisms and points to critical

experiments needed to distinguish among some of

the remaining possible mechanisms. Knowing the

mechanism for whisker formation will be key to the

control and hopefully suppression of Sn whisker

formation.

Our past work provided tools to chip manufacturers

for on-chip copper interconnect development for next

generation chips. We have moved successfully into

several new and exciting areas: we have included the

impact of leveling additives in our Curvature Enhanced

Accelerator Coverage (CEAC) model — these are

used industrially to control overfill bump formation;

we have demonstrated gold superfill; we have

completed a thorough assessment of the issues

relevant to successful wetting and superfill of copper

on ruthenium barriers that is already being requested by

industry and will be key to successful implementation

in industry, should it occur; we have achieved seedless

superfill on osmium barriers, potentially superior to

ruthenium as a diffusion barrier, a key issue for barriers

for seedless superfill; we have started new projects

on seedless superfill and experimental studies of

leveling agents.

Recognition

Bill Egelhoff became a NIST Fellow, the highest

scientific and technical position at NIST.

Lyle Levine and Richard Fields (retired) were part

of a team of scientists that won the Allen V. Astin

Measurement Science Award for outstanding

achievement in the advancement of measurement

science. This award recognized the development of

techniques to measure stress–strain relationships of

materials under high heating-rate, high strain-rate

conditions.

The Metallurgy Division was recognized by Science

News “News of the Year” in December 2004 for two

breakthrough developments:

■ Bob Shull led a team which found that a small amount

of iron added to Gd5Ge2Si2 resulted in a significantly

improved refrigerant, pointing the way to potential

commonplace magnetic refrigeration.

■ Jim Warren (Metallurgy) and Jack Douglas

(Polymers) were recognized for showing a duality

between kinetic and static effects controlling

microstructure during solidification.

Frank W. Gayle

Acting Chief, Metallurgy Division

8
Year in Review

Polymers Division

This report marks an excellent year for the Polymers

Division in terms of impacts not only in technical areas,

but also in professional impact for our staff. This year,

Joseph Antonucci of our Biomaterials Group was awarded

the FLC Technology Transfer Award for his research,

patenting, and technology transfer activities resulting

in commercialization of restorative dental resins; Michael

Fasolka of our Multivariant Measurement Methods Group

received the Presidential Early Career Award for Scientists

and Engineers (PECASE) for his work in nanostructured

polymer films and scanned probe techniques; and

Wen-li Wu was named a NIST Fellow for his high-impact

advances in measurement methods to assist industry,

developments in the fundamentals of scattering, and

significant scientific insights in polymer physics.

This year, we are pleased to present highlights in

areas ranging from nanomanufacturing and nanofabrication

to organic electronics to combinatorial methods to

standards test methods. Further information on these

technical highlights is available on the Polymers

Division’s website at www.nist.gov/polymers.

Chaotic Mixing in

Microfluidic Channel Flows

Realization of nanomanufacturing requires the

ability to efficiently mix disparate liquids, which is

difficult to achieve in small-scale microfluidic devices.

This requires the development and use of new mixing

technologies. A promising candidate for enhancing

mixing is chaotic flow, where the flow-streamlines

repeatedly cross themselves resulting in mixing that

is orders of magnitude more efficient than diffusion.

We determined precisely how to generate a chaotic flow

and developed metrics to assess the degree of chaos.

The “crossing-streamline” principle was used to

study the generation of chaotic mixing in intersecting

channels driven by oscillatory flow boundary conditions,

which serve as the source of the necessary temporal

variations. Our advances represent new paradigms

in nanomanufacturing.

Metrology for Nanoimprint Lithography

Nanoimprint lithography (NIL) is an exciting

technology for cost-effective routine fabrication of

polymers and other soft materials into 3D nanoscale

structures by physically molding them with a hard

master. Nanoimprinted structures with dimensions

< 10 nm have been achieved without the expensive,

complex infrastructure required of next generation

photolithography. Future advancements in NIL,

however, require new measurements of dimensions

with sub-nm precision, the characterization of

structures with complex shapes, and investigations

of the properties of new and unique nanostructured

materials. The importance of these metrology needs

were established through a panel discussion consisting

of 7 experts and 300 audience participants, led by

Christopher Soles from the Polymers Division, at

the 2005 SPIE Microlithography Conference in

Santa Clara, CA. The panel featured representatives

from leading nanoimprint vendors, universities,

semiconductor companies, and nanotechnology

industries.

Influence of Interfacial Structure

of Organic Semiconductors on

Device Performance

Organic electronic devices are increasingly

incorporated into electronics packaging and are projected

to revolutionize integrated circuits through new

applications taking advantage of low-cost, high-volume

manufacturing, nontraditional substrates, and designed

functionality. Adoption of these devices will be advanced

by developing an integrated and interdisciplinary suite of

measurement methods correlating device performance

with structure, properties, and chemistry of critical

materials and interfaces.

Near-edge x-ray absorption fine structure

(NEXAFS) spectroscopy was used for investigating

the electronic structure, chemistry, and orientation of

several organic electronic molecules near a supporting

substrate. In collaboration with the University of

California–Berkeley, NEXAFS spectroscopy was applied

to successfully quantify the simultaneous chemical

conversion, molecular ordering and defect formation

9
Year in Review

of soluble oligothiophene precursor films for application

in organic field effect transistors (OFETs). Variations

in field-effect hole mobility on thermal processing

correlated directly with the orientation and distribution

of molecules within (3 to 20) nm thick films.

Gradient Libraries of

Surface-Grafted Polymers

Layers of grafted polymers provide the means for

the physically robust, chemically versatile surface

functionalization required for advanced applications,

such as friction management in MEMS, adhesion

promotion for coatings, protein adsorption control in

biomaterials, and environmentally responsive surfaces

for sensors. However, while recent advances in controlled

polymerization enable grafted polymers that exhibit

many types of architecture and composition, identifying

the optimal grafted system for a given application can

be difficult, time consuming, and expensive.

In response, the NIST Combinatorial Methods Center

has developed tools for probing the optimal molecularto micro-scale properties of grafted polymer systems.

These methods employ microfluidic technology to deliver

tailored mixtures and sequences of monomers to an

initiator-functionalized surface. The resulting grafted

polymer libraries exhibit gradual, systematic changes in

composition, chain length, and architecture. Gradients

of grafted block copolymers prepared via these techniques

reveal composition regimes that “switch” their surface

properties in response to solvent exposure. Fabrication

of layers, e.g., of grafted tapered copolymers exhibiting a

gradual change in composition along the polymer chain,

have also been demonstrated. Moreover, our unique ability

to prepare statistical copolymer composition gradients

provides comprehensive maps of complex surface

chemistry, which were previously impossible.

Polymer Grafting Density, Protein

Adsorption, and Cellular Response

A combinatorial library consisting of a cell-adhesive

protein-coated poly(2-hydroxyethyl methacrylate)

(poly(HEMA)) gradient with variable grafting densities

was developed to investigate cell adhesion. Fibronectin

(FN), a well-characterized extracellular matrix protein,

was selected as a model protein to study the effect of

poly(HEMA) grafting density on cell adhesion, protein

adsorption, and cellular response. The 2D conformational

gradient varied from low- to high-graft density with the

polymer chain structure changing from mushroom- to

brush-like regimes, respectively, with the FN positioned

between poly(HEMA) chains. By varying the chemistry,

morphology, and functionality of this film, the number

of adherent cells and their corresponding shapes varied

significantly. Cell adhesion and spreading were used

to evaluate the effect of poly(HEMA) grafting density

on cellular response. A maximized cell adhesion

and spreading response was found at low grafting

density/high FN density, and little cell adhesion and

spreading was found at high grafting density/low FN

density. The experimental results of protein adsorption,

cell adhesion, and spreading were consistent between

gradient samples and uniform samples, strongly indicating

that gradient preparation technology can be used for

combinatorial studies of surface-protein-cells interactions.

ASTM Test Method for Mass

Spectrometry of Polymers

Charles Guttman of the Polymers Division initiated

and led Technical Working Activity 28 of the Versailles

Project on Advanced Materials and Standards (VAMAS)

to developed an ASTM Standard Test Method to

determine the molecular mass distribution of polystyrene

using matrix-assisted laser desorption/ionization mass

spectrometry (MALDI MS). The method uses data and

protocols developed in a NIST-sponsored interlaboratory

comparison organized with the help of the American

Society for Mass Spectrometry, a complete description

of which has been published in Analytical Chemistry.

This method covers the determination of molecular

mass averages and the distribution of molecular masses

for linear atactic polystyrene of narrow molecular mass

distribution ranging in molecular masses from (2,000

to 35,000) g/mol, and it provides detailed procedures

for instrument calibration and sample preparation,

as well as details for measuring the

samples on a mass spectrometer.

Eric J. Amis

Chief, Polymers Division

10
Year in Review

NIST Center for Neutron Research

membranes. The centerpiece of CNBT, funded by the

National Institutes of Health, is the Advanced Neutron

Diffractometer/Reflectometer (AND/R).

The ExxonMobil Research and Engineering

Company continued its long-standing partnership with

the NCNR through their participation in the operation,

maintenance, and research at the NG-7 30 m SANS

instrument. They use neutron scattering techniques to

deepen their understanding of ExxonMobil’s products

and processes, so as to improve customer service and

the return on shareholders’ investment.

The Department of Energy (DOE) maintains

several programs at the NCNR. Brookhaven National

Laboratory directly partners with NIST through the

BNL–NIST Scientific Alliance. In the last year, the

NCNR joined the Metal-Hydride and Carbon-Based

Materials Centers of Excellence, sponsored by

DOE’s Office of Energy Efficiency and Renewable

Energy, to develop materials for hydrogen storage.

The Center for Food Safety and Applied Nutrition,

U.S. Food and Drug Administration (FDA) maintains a

neutron activation analysis (NAA) facility at the NCNR

that provides analytical support for FDA programs.

The Smithsonian Institution’s Nuclear Laboratory

for Archeological Research has had a productive

28-year partnership with NCNR, during which time

it has analyzed over 30,000 archaeological artifacts

by NAA.

The NCNR has continued to upgrade and expand

its measurement capabilities. These instrument

developments remain a priority since improvements

in capabilities lead directly to the long-term scientific

success of the facility. The NCNR is in the advanced

stages of manufacturing and installation of two

new crystal spectrometers that will bring enormous

improvements in capability for inelastic neutron

measurements to the NCNR and open up new research

opportunities. The new BT-7 thermal triple-axis

spectrometer will be ready for users in the next year.

The other new instrument, the Multi-Analyzer Crystal

Spectrometer (MACS), is a partnership between NIST,

the National Science Foundation, and The Johns Hopkins

University. It will also begin commissioning in the next

year. Substantial progress has also been achieved on

an additional thermal triple-axis spectrometer to be

installed at BT-9 and on the new time-resolved SANS

capability that will allow researchers to access kinetic

phenomena on time scales of 50 ms to 100 ms using

stroboscopic techniques.

The more than 300 publications resulting from

work done at the NCNR during the past year include

The NIST Center for Neutron Research (NCNR)

is the nation’s leading neutron facility. This year

more than 2000 research participants from all areas of

the country, from industry, academia, and government

used the facility for measurements. These researchers

primarily gain access through a peer-reviewed proposal

system with beam time allocated by a Program

Advisory Committee twice a year. The NCNR also

supports important NIST research programs in

nanotechnology, materials science, chemistry,

physics, and biotechnology.

The NCNR source provides intense beams of

neutrons to nearly thirty experimental stations.

In addition to a thermal neutron D2O moderator, the

NCNR has a large area liquid hydrogen moderator,

or cold source, that provides intense neutron beams

to the only cold neutron facility operating in the U.S.

The operation of the facility over the past twelve

months has been outstanding. This year, the NCNR

ran as scheduled, completing nearly 200 beam days

of operation and a major outage for maintenance and

upgrade of the source and to install new instruments.

The cold source and beam delivery systems also

continue to provide highly reliable service.

Partnerships are integral to the success of the

NCNR. The Center for High Resolution Neutron

Scattering (CHRNS), a partnership with the National

Science Foundation that funds the operation of

six world-class neutron scattering instruments, was

renewed for another five years. CHRNS serves more

than 500 users who produce nearly 100 publications

annually.

The Cold Neutrons for Biology and Technology

(CNBT) consortium is dedicated to studies of biological

11
Year in Review

numerous notable scientific achievements. The

following are two representative research highlights.

Developing safe, cost-effective, and practical

means of storing hydrogen is crucial for the

advancement of fuel-cell technologies. The NCNR’s

Taner Yildirim, in collaboration with Prof. Salim Ciraci,

has used first-principles calculations to show that

carbon nanotubes “decorated” with titanium or

other transition metals can bond to up to four

hydrogen molecules per Ti. This corresponds to

nearly 8 percent of the weight of “decorated” carbon

nanotubes, one-third better than the 6 percent minimum

storage-capacity requirement set by the Freedom

Car Research Partnership involving the DOE and the

nation’s “Big 3” automakers. These bound hydrogen

molecules are readily relinquished when the system is

gently heated. Such reversible desorption is another

requirement for practical hydrogen storage. Thus,

these findings suggest a method of engineering new

nanostructures for efficient, high-capacity hydrogen

storage. This work, which appeared in Physical

Review Letters, has been featured in a wide variety of

forums including Materials Today, Fuel Cell Review,

and C&E News.

This year, several

prestigious honors were

bestowed upon the users

and staff of the NCNR.

Charles F. Majkrzak was

named the recipient of

the 2006 Warren Award

for Diffraction Physics.

Dr. Majkrzak was

cited “for his seminal

contributions to the

development of neutron

reflectivity and for his

pioneering work in the

exploration of many issues

in interface science using this technique.” An NCNR

team including Charles Majkrzak, Susan Krueger,

Joseph Dura, and Donald Pierce was awarded a

Department of Commerce Silver Medal for their

scientific and engineering leadership in establishing

CNBT at the NCNR.

Taner Yildirim received a Bronze Award for

theoretical research which showed how the physical

and chemical properties of carbon nanotubes can be

tuned with pressure. Paul Brand and Henry Prask

of the NCNR, along with Richard J. Fields of the

Metallurgy Division, were awarded the NIST

Jacob Rabinow Applied Research Award for developing

the nation’s best capabilities for measuring residual

stress depth profiles and texture in metals, ceramics,

and composites. Brian Toby was elected Fellow of

the International Centre for Diffraction Data (ICDD)

for his contributions to the standardization of data

formats and the creation of tools to use these formats

efficiently. Vanessa Peterson received the 2005

Brunauer Award from the Cements Division of the

American Ceramic Society for the best paper on the

topic of cements published by the American Ceramic

Society during the previous year.

Two long-time NCNR users won awards for work

in which neutron scattering results played a major part.

Dr. Frank Bates, Distinguished McKnight University

Professor and Head of Chemical Engineering and

Materials Science at the University of Minnesota, was

presented the Turnbull Lecturer Award “for pioneering

contributions to the fundamental understanding of

structure and properties of complex polymeric materials,

particularly block copolymers and polymeric vesicles,

coupled with outstanding lecturing, writing, teaching,

and educational leadership.” Dr. Thomas Russell,

Distinguished Professor of the Polymer Science

& Engineering Department of the University of

Massachusetts Amherst was awarded the 2005

Polymer Physics Prize “for his pioneering research

and fundamental elucidation of the surface and

interfacial behavior of polymers.”

Patrick D. Gallagher

Director, NIST Center for Neutron Research

Wormlike micellar solutions formed by self-assembled

surfactants exhibit rheological properties such as shear

thinning and suppression of turbulent flow that are

related to the flow-induced changes in their structural

conformations or orientations. These flow properties

are important in applications such as thickeners,

drag reducers and flow improvers in the food and

cosmetics industries. A collaboration between the

University of Delaware and the NCNR combined SANS

with a novel shear cell to measure the microstructure

of a shear-induced phase separating wormlike micellar

solution. The results show that both concentration

fluctuations and gradients in segmental alignment

occur, and they link shear banding in wormlike micellar

solutions to a shear-induced phase separation.

Dr. Charles F. Majkrzak

12
Program Overview

Nanometrology

Nanotechnology will revolutionize and possibly

revitalize many industries, leading to new and improved

products based on materials having at least one dimension

less than 100 nm. The federal government’s role in

realizing the full potential of nanotechnology is coordinated

through the National Nanotechnology Initiative (NNI),

a multi-agency, multi-disciplinary program that supports

research and development, invests in a balanced

infrastructure, and promotes education, knowledge

diffusion, and commercialization in all aspects of

nanoscale science, engineering, and technology.

NIST’s unique and critical contribution to the NNI is

nanometrology, defined as the science of measurement

and/or a system of measures for nanoscale structures

and systems. NIST nanometrology efforts focus

on developing the measurement infrastructure —

measurements, data, and standards — essential to

advancing nanotechnology commercialization.

This work provides the requisite metrology tools

and techniques and transfers enabling measurement

capabilities to the appropriate communities.

MSEL plays a vital role in nanometrology work at

NIST with efforts in four of the seven NNI Program

Component Areas — Instrumentation Research,

Metrology and Standards for Nanotechnology;

Nanomaterials; Nanomanufacturing; and Fundamental

Nanoscale Phenomena and Processes. Innovative

projects across MSEL are defining and addressing

the forefront research issues in these areas.

Instrumentation Research, Metrology

and Standards for Nanotechnology

R&D pertaining to the tools needed to advance

nanotechnology research and commercialization.

The design, development, and fabrication of nanodevices

will require nanomechanical measurements that are rapid,

accurate, predictive, well-understood and representative

of a device or system’s environment in real time. MSEL

is addressing this need by developing instrumentation,

methodology, reference specimens and multi-scale

modeling approaches to quantitatively measure mechanical

properties such as modulus, strength, adhesion, and

friction at nanometer-length scales. This year, novel

instruments for measuring adhesion and friction forces

between surfaces and nanoparticles were developed jointly

with industrial partners. Quantitative maps of elastic

modulus were obtained by innovative methodologies based

on atomic force microscopy and strain-induced elastic

buckling instability. To address the need for quantifying

measurements made with widely-used commercial

nanoindentors and scanned probe microscopy

instruments, MSEL is developing reference specimens

and SI-traceable force calibration methodology.

Nanomaterials

Research aimed at discovery of novel nanoscale

and nanostructured materials and at a comprehensive

understanding of the properties of nanomaterials.

Among the many classes of nanomaterials, nanotubes

have received great attention due to their remarkable

physical properties relevant to many applications.

In response to needs expressed by industry and other

federal agencies, MSEL has embarked on a new effort

to develop a suite of metrologies and standards aimed at

characterizing key structural features and processing

variables of carbon nanotubes. These include dispersion,

fractionation, orientation, alignment, and manipulation

of individual single-walled nanotubes, all critical to

establishing efficient bulk processing schemes to meet

the imminent high demand for carbon nanotubes.

Nanomanufacturing

R&D aimed at enabling scaled-up, reliable,

cost-effective manufacture of nanoscale materials,

structures, devices, and systems. Nanoimprint lithography

(NIL) is rapidly emerging as a viable high-throughput

technique for producing robust structures with a

patterning resolution better than 10 nm. MSEL is

developing metrologies that are crucial to advancing

NIL as an industrial patterning technology for the

electronics, optics, and biotechnology industries.

The current focus is on characterizing shape and

the fidelity of pattern transfer, two key factors in

achieving widespread commercial application of NIL.

Fundamental Nanoscale

Phenomena and Processes

Discovery and development of fundamental knowledge

pertaining to new phenomena in the physical, biological,

and engineering sciences that occur at the nanoscale.

The magnetic data storage industry needs the ability to

measure and control magnetization on nanometer length

scales and nanosecond time scales to meet increasing

demands for reduced size and increased speed of devices.

MSEL is developing measurement techniques to elucidate

the fundamental mechanisms of spin dynamics and

damping in magnetic thin films. Work this year has

focused on measurements of the effects of interfaces

and interface roughness on magnetization dynamics and

magnetic characterization of edges in magnetic devices.

Through these and other research activities,

MSEL is maintaining its committed leadership in

developing the measurement infrastructure for

current and future nanotechnology-based applications.

Contact: Debra L. Kaiser (Ceramics Division)

13
Mechanical Metrology for Small-Scale Structures

Significant progress has been made in the design

of a compressively loaded test configuration with a

well-defined, tensile gage section. The inset of Figure 1

shows one such specimen fabricated by James Beall using

deep reactive ion etching (DRIE) of a silicon wafer. When

a load is applied to the top of this theta-like geometry, a

uniform uniaxial tensile stress develops in the middle gauge

section. Finite element analysis gives (horizontal) gauge

section stress and strain as functions of the applied load

and load-point displacement, respectively. Dimensionless

calibration factors have been obtained for several specimen

and fillet geometries, and as a function of the gauge width.

Industrial trends toward miniaturization require

quantitative mechanical property data for

design, development, and fabrication of modern

small-scale devices. Developments in disruptive

technologies require engineering materials data

for structures and architectures at multiple (nano

to macro) length scales. Accordingly, we are

designing and developing mechanical testing

configurations from small-scale in-situ structures

for localized measurements of fracture and

deformation behavior of materials and interfaces.

Edwin R. Fuller, Jr. and Douglas T. Smith

This project aims to: (i) measure mechanical

properties of microstructures for myriad industrial

and biological systems that cannot be fabricated in bulk

samples; (ii) study small-scale phenomena, which may

be controlled by surface effects (e.g., the influence of

surface stresses on crack nucleation and extension);

and (iii) obtain quantitative mechanical property data of

materials and interfaces for designing small-scale structures

and components and for assessing their mechanical

reliability. Well-characterized testing configurations

are being designed and developed for measurements of

strength and crack extension of small-scale structures and

interfaces. We are pursuing four tasks: (i) configuration

design, optimization, and characterization via finite-element

analyses; (ii) specimen fabrication; (iii) mechanical testing

and fracture analysis (fractography); and (iv) length and

force metrology. In addition to work in the Ceramics

Division (tasks i, iii, and iv), two collaborations were

established in the fabrication task (ii): one with James A.

Beall of the Quantum Electrical Metrology Division in NIST

Boulder, and one with Northwestern University.

Specimens are tested using a depth-sensing nanoindenter

as a universal testing machine, thereby giving a continuous

record of applied load and load-point displacement.

Repeatability is illustrated in Figure 1. Strength data

for DRIE silicon, Figure 2, suggest that differences

for round and hexagonal specimen configurations are

not significant.

To extend this technique to a wider variety of

material systems, focused-ion-beam (FIB) milling is

being explored in collaboration with Northwestern

University. Hexagonal theta specimens fabricated

from a lamellar directionally solidified eutectic of

Ni0.5Co0.5O and ZrO2 are approximately 1/15 the

size of the silicon specimens.

Contributors and Collaborators

D. Xiang, G.D. Quinn, D.L. Henann (Ceramics

Division, NIST); J.A. Beall (Quantum Electrical

Metrology Division, NIST); N. Alem, V.P. Dravid

(Northwestern University)

Nanometrology

Figure 1: Repeatability for multiple loading of a single specimen.

Figure 2: Weibull plots for round and hexagonal configurations.

14
Nanomechanics: Atomistics in Modeling and Experiments

Nanoscale mechanical behavior (including

failure) is inherently difficult to measure

accurately, and existing modeling tools are only

qualitative at best. We are developing modeling

techniques that provide quantitative predictions

and validating these results experimentally.

Lyle E. Levine, Douglas T. Smith, and

Anne M. Chaka (838)

Mechanics at the nanoscale is inherently difficult

to model accurately. Finite element models

(FEM) can effectively capture the elastic behavior of

macroscopic structures but include no accurate failure

criteria, since this depends upon atomic-scale behavior.

Classical atomistic simulations can handle millions to

billions of atoms, enough to model such events, but these

potentials become inaccurate for large strains and cannot

effectively handle chemistry. Quantum-mechanics-based

simulations using density functional theory (DFT) are

extremely accurate and handle the chemistry exactly,

but such simulations are so CPU-intensive that they can

handle only a few hundred atoms. A combination of all

three modeling techniques is required to accurately

model device behavior at the nanoscale.

Over the past year, we have been developing

quantitative multiscale modeling techniques for

quasistatic applications. At the macroscale, FEM is

used to simulate the elastic behavior of a nanomechanical

system. Figure 1 shows an example in which a <111>

Al crystal is indented by a nanoindenter. The shape of

the nanoindenter was obtained using an atomic force

microscope with closed-loop displacement control.

The fine central mesh has nodes on fcc atom positions.

The figure shows the resulting von Mises stress

distribution (in cross-section) after indenting 1.5 nm.

The use of classical potentials in a large simulation

cell allows us to propagate long-range stresses to the

critical regions where bond distortions are large or where

chemistry effects need to be explored. In these critical

regions, we embed a DFT simulation. The critical region

is relaxed iteratively using DFT, and the classical cell is

relaxed using a molecular dynamics algorithm.

Figure 1: FEM model of a rigid nanoindenter indenting a <111>

aluminum single crystal to a depth of 1.5 nm.

Figure 2 shows a classical atomistic simulation

using the embedded atom method (EAM). Initial atom

positions and boundary conditions came from a FEM

simulation. The subsurface structure is composed

of dislocations that nucleated from a single event.

After an initial dislocation nucleation event,

nanoindentation progresses through the complex evolution

of dislocation structures. For example, the raised lip

around an indent is produced by large numbers of

dislocations exiting the surface. We are modeling the early

stages of this process using 3D dislocation dynamics,

assuming a random distribution of dislocation sources.

Finally, connection to experimental measurements

requires careful force calibration of the indenter and

calibrated atomic force microscopy measurements

of the indenter tip. We are setting up to grow bulk

single-crystal copper samples, which will be cut

and polished using non-contact chemical methods

to minimize the dislocation density. We are also

developing SI-traceable calibration methodology

for nanoindenters and atomic force microscopes.

Contributors and Collaborators

S.M. Khan, L. Ma, F. Tavazza, F. Biancaniello

(Metallurgy Division, NIST); H. Burdette, B. Hockey,

R. Wagner (Ceramics Division, NIST)

Figure 2: EAM simulation showing dislocations produced by

nanoindentation of <111> Al to a depth of 4.5 nm.

Nanometrology

15
Nanometrology

Modulus Mapping at the Nanoscale

We are developing metrology for rapid,

quantitative assessment of elastic properties

with nanoscale spatial resolution. Atomic force

acoustic microscopy (AFAM) methods enable

modulus measurements either at a single point

or as a map of local property variations.

The information obtained furthers our

understanding of nanopatterned surfaces,

thin films, and nanoscale structures.

Donna C. Hurley

As critical dimensions shrink well below 1 μm, new

 tools are required to investigate materials properties

on commensurate scales. Not only is higher spatial

resolution needed, but it is also increasingly important

to assess not just the “average” properties from a single

sample position, but to visualize the spatial distribution

in properties. To meet these needs, we are developing

methods to measure and image elastic properties based

on the atomic force microscope (AFM). Atomic force

acoustic microscopy (AFAM) involves the vibrational

modes of an AFM cantilever when its tip is in contact

with a sample. With AFAM, the indentation modulus M

of the sample can be determined. The small tip radius

(~5–50 nm) enables nanoscale spatial resolution.

In FY05, we combined single-point AFAM methods

with scanning to achieve quantitative nanomechanical

mapping. We developed a frequency-tracking circuit to

pinpoint the contact-resonance frequencies at each image

pixel. A digital signal processor architecture enables

rapid data acquisition (~20 min. per 256 x 256 image).

Figure 1 shows an example of a modulus map calculated

from resonant-frequency images. The calculations use

a Hertzian model for the tip-sample contact. The values

of M agree with both single-point AFAM measurements

on the same sample and literature values for the

constituent materials in bulk form. This mapping

capability greatly expands our ability to evaluate the

properties of multicomponent nanostructures.

Accurate AFAM measurements depend on a detailed

knowledge of the contact mechanics between the tip and

the sample. In FY05, we continued tandem AFAM and

high-resolution scanning electron microscope (SEM)

experiments to better understand the contact mechanics.

We found that the actual behavior varies from tip to tip

and is best described by a mixture of Hertzian and

flat-punch models. We are now working to integrate

these results into our measurement and analysis procedures

in order to improve accuracy and precision.

Another aspect of measurement accuracy involves

the static forces applied by a tip. The magnitude of the

force is determined by the stiffness of the cantilever, but

this quantity is often poorly known. We began work on

this issue in FY05 using NIST’s electronic force balance

(EFB). The EFB provides SI-traceable force calibration

at the nano- to micronewton scale. With the EFB, we

obtained the voltage-versus-force relationship for several

piezoresistive cantilevers. These cantilevers will serve as

force transfer standards to calibrate the cantilevers of

unknown stiffness used in our experiments.

We also continued experiments on relative humidity

(RH) effects using self-assembled monolayers (SAMs)

of n-octyldimethylchlorosilane on silicon. The calculated

contact stiffness did not depend on RH for a hydrophobic

SAM, but increased strongly with RH for a hydrophilic

SAM. Because the contact stiffness represents the elastic

tip-sample interaction, it should not depend on humidity.

The data can be explained by capillary forces that cause

a viscoelastic interaction. To include capillary forces, a

humidity-dependent damping term was added to the data

analysis model. The contact stiffness calculated with this

model was constant with RH, and the damping behavior

was similar to that observed for AFM pull-off forces.

Such results enhance our measurement capabilities for

a range of materials and environmental conditions.

FY05 project results were described in 6 contributed

and 2 invited journal articles, 5 conference presentations

(3 proceedings), and 2 invited workshop presentations.

Contributors and Collaborators

M. Fasolka, R. Geiss, D. Julthongpiput,

M. Kopycinska-Müller, P. Rice, D. Smith (MSEL,

NIST); A. Kos (EEEL, NIST); J. Pratt (MEL, NIST);

M. Prasad (Colorado School of Mines); J. Turner

(University of Nebraska); W. Arnold, U. Rabe

(Fraunhofer Institute, Germany)

Figure 1: AFM topography (L) and AFAM modulus map (R)

images of a thin-film sample containing a niobium (Nb) stripe

~200 nm thick on top of a silica (SiO2 ) blanket film ~350 nm thick.

16
Engineering of nanomaterials, biomaterials, and

organic electronic devices hinges on techniques

for imaging complex nanoscale features. In this

respect, new Scanned Probe Microscopy (SPM)

methods promise mapping of chemical, mechanical,

and electro-optical properties, but these techniques

generally offer only qualitative information.

Our reference specimens, fabricated with a

combinatorial design, calibrate image data from

emerging SPM methods, thereby advancing these

nanometrology tools.

Michael J. Fasolka

Anew generation of SPM techniques intend to

 measure chemical, mechanical, and electro/optical

properties on the nanoscale. However, contrast in new

SPM images is difficult to quantify since probe fabrication

can be inconsistent, and probe/sample interactions are not

understood. Our research at the NIST Combinatorial

Methods Center (NCMC) provides reference specimens

for the quantification of next-generation SPM data.

Using a gradient combinatorial design, our specimens

gauge the quality of custom-made SPM probes and

calibrate SPM image contrast through “traditional” surface

measurements (e.g., spectroscopy and contact angle).

Nanometrology

Reference Specimens for SPM Nanometrology

Figure 2: Demonstration of ∇μp specimen. SPM friction

contrast (κ) vs. surface energy (γ) differences obtained with

probes of different chemical quality. The red arrow marks the

γ-difference sensitivity of a UV-ozone cleaned probe.

Figure 1: Schematic illustration of the ∇μp for calibration of

chemically sensitive SPM techniques. Blue “droplets” illustrate

water contact angle measurement along the calibration strips.

of the matrix. Accordingly, traditional measurements,

e.g., water contact angle, along these fields relate

the chemical contrast in the ∇μp to known quantities,

e.g., surface energy differences.

Figure 2 demonstrates the utility of the ∇μp specimen

for SPM data calibration. This plot was generated from a

series of SPM friction images acquired along the graded

pattern. A frictional contrast parameter, κ, which reflects

measured friction force differences between the lines and

matrix, was extracted from each image. To create a

contrast calibration curve, κ is plotted against surface

energy data derived from water contact measurements

along calibration fields. As shown in Figure 2, the

combinatorial ∇μp provides, in a single specimen, a fullspectrum relationship between SPM friction force and

surface energy. As shown through the three curves, the

specimen also enables direct comparison between different

probe functionalization strategies. Moreover, the curves

illuminate the minimum γ-difference detectable by a given

probe (where κ → 0), i.e., its chemical sensitivity.

Our fabrication route for the ∇μp, and its use as

a reference specimen for emerging SPM techniques,

is the subject of an article published in Nanoletters

(2005, ASAP).

Contributors and Collaborators

K.L. Beers, D. Julthongpiput (Polymers Division,

NIST); D. Hurley (Materials Reliability Division, NIST);

T. Nguyen (Materials and Construction Research Division,

NIST); S. Magonov (Veeco/Digital Instruments)

This year, we demonstrated the fabrication and use of

a reference substrate that combines patterning of a

self-assembled monolayer (SAM) with a surface energy

gradient. Our gradient micropattern (∇μp) specimens

incorporate a series of micron-scale lines that continuously

change in their surface energy compared to a constant

matrix. Patterning is achieved via a new vapor-mediated

soft lithography of a hydrophobic chlorosilane SAM on

SiO2 (matrix). A subsequent graded UV-Ozone exposure

gradually changes the chemistry of the patterned SAM

along the specimen from hydrophobic to hydrophilic

species. As shown in Figure 1, the specimen design

includes two calibration fields, which reflect the changing

chemistry of the SAM lines and the constant chemistry

17
Nanometrology

Nanotribology and Surface Properties

Accurate determination of adhesive and frictional

forces between surfaces and particles is critical

for efficient and effective design and development

of nanoscale devices and manufacturing processes.

Working with diverse industrial partners (instrument,

device, and magnetic storage industries), we

are addressing this critical need by developing

metrology tools and methods for nanomechanical

property measurements.

Stephen M. Hsu and Richard S. Gates

One of the major conclusions from the

National Nanotechnology Initiative workshop

on instrumentation and metrology (held at NIST in

January 2004) was need for improved tools, methods,

and calibration procedures for nanoscale measurements.

Several advances in measuring friction and adhesion

and controlling surface lubrication and texturing

were achieved this year.

Advances in Instrumentation

Existing atomic force microscopy (AFM) and

multiscale friction testing instruments were upgraded to

improve measurement accuracy and extend applicability

of the methods. The AFM was extensively modified to

increase the signal-to-noise ratio. A joint effort with

Hysitron resulted in a new 3-D force sensor to conduct

friction and scratch tests with much higher accuracy.

Sample stage modulation is being implemented across

several platforms to increase sensitivity and expand

measurement capability. In-house cantilever and tip

fabrication capability and collaborations with numerous

specialty tip fabricators were established.

Figure 1: Surface features on colloidal probes.

 In adhesion and friction measurements, surface forces

are critical parameters that depend upon the real area of

contact. Figure 1 illustrates typical colloidal probes showing

random surface features. A computational procedure was

developed to estimate the bearing area for this type of

probe enabling better determination of contact areas.

The first nanoscale probe using an ultra-thin sheet of

mica glued on a colloidal probe was successfully developed

to measure surface forces on extremely small areas

(Figure 2). To avoid snap-on of the probe tip during

approach, the cantilever stiffness and signal-to-noise ratio

were increased.

Surface Control

Advances were made in the organization of mixed

molecules on surfaces for hydrophobicity, anti-adhesion,

and friction control properties. Ultra-durable hydrophobic

films and friction control films were demonstrated last

year. Collaboration with Dan Fischer at the NIST beam

line at the National Synchrotron Light Source continues

to be vital in characterizing these complex molecular

mixtures.

Surface textures are increasingly being used to

control surface energy, polarity, adhesion, and friction.

In work supported by other agencies and industries, the

surface properties of materials were controlled by use

of specific surface features such as dimples, triangles,

and ellipses at micro- and nanoscale dimensions.

Interactions

Ongoing interactions with domestic and international

partners included a cantilever force calibration study

with other National Measurement Institutes and

Jon Pratt (NIST, MEL), and surface texture research

with seven other countries.

Contributors and Collaborators

C. Ying, S. Yang, M. Reitsma, D.-I. Kim, Y. Liang,

X. Wang, J. Grobelny, D. Fischer, Y.T. Hsia (Seagate);

W. Gerberich (University of Minnesota); O. Warren

(Hysitron); C. Su (Veeco); D. Mendel (NPL);

E. Santner (BAM)

Figure 2: Surface force measurement down to 1 nm. The inset

shows a schematic of a typical force curve from the AFM.

18
Nanometrology

Chemistry and Structure of Nanomaterials

Successful nanoscale materials fabrication is

empowered by a detailed knowledge of the

chemistry and structure of surface bound

molecules; e.g., the optimization of SAMs,

molecular templates, MEMs lubricants, and

functionallized nanotubes. We develop,

demonstrate, and advance cutting-edge

synchrotron metrologies to bring nanoscale

materials phenomena to practical applications.

Daniel A. Fischer, Vincent A. Hackley,

and Andrew J. Allen

I

n potential MEMs lubricants, we have found that

 the degree of surface ordering in self-assembled

monolayers (SAMs) governs the friction properties of

the film. n-Alkyltricholorosilanes films with different

chain lengths (Cn films where n=5–30) were

characterized by near-edge x-ray absorption fine

structure (NEXAFS), Fourier transform infrared

spectroscopy (FTIR), and atomic force microscopy

(AFM). The chain lengths having 12, 16 and 18

carbon atoms were found to be highly oriented with a

preferential molecular orientation of the polymeric C-C

chains perpendicular to the surface. C5 and C30 SAMs

did not exhibit preferential orientation of the alkyl chain

and C10 showed partial ordering. Complementary FTIR

tudies were done to estimate order qualitatively by

peak positions of asymmetric CH2 and the symmetric

CH2 stretches. The molecular order information

from FTIR followed similar trends as determined by

NEXAFS. The frictional properties of the organic

monolayers were determined through the simultaneous

measurement of normal (load) and lateral (friction)

interfacial forces with AFM. Friction measurements

on different chain lengths follow inverse trends with

surface order from NEXAFS as shown in Figure 1.

The flow-cell developed by NIST for in situ

ultra-small-angle x-ray scattering (USAXS) studies

of solution-mediated nanoscale materials has been

applied to the technologically important case of a

homogeneously precipitating solution of nanosize

ceria (n-CeO2). n-CeO2 has multiple applications in

catalysis, as a solid oxide fuel cell electrolyte material,

and in a number of other areas.

Figure 1: SAM order and friction versus chain length.

Modeling of in situ USAXS data taken during

reaction at 25 oC indicates a co-precipitation of solid

principal particles (see Figure 2) and a population

of fine particles with a core-shell morphology.

The principal population grows in size and volume

fraction, V, but the fine secondary features grow only

in volume fraction. It has been postulated that the

fine features constitute a step in the formation of the

principal particle population, a theory currently being

tested with additional experiments in conjunction

with Columbia University collaborators.

A strong temperature affect is seen: at 35 °C,

the volume fraction of principal particles increases

with a growth rate roughly twice that at 25 °C.

The activation energy for the n-CeO2 precipitation was

estimated from USAXS data to be about 46 kJ mol–1.

Additional studies with the flow-cell focus on

dispersion and flow-induced alignment of carbon

nanotubes in various solvent/dispersant systems.

Contributors and Collaborators

S. Sambasivan, S. Hsieh, S. Hsu (Ceramics Division,

NIST); P.R. Jemian (University of Illinois); J. Ilavsky

(APS XOR); S.-W. Chan (University of Columbia);

J. Randall, M. Banesh (Zyvex Inc.); H. Wang

(Michigan Tech.)

Figure 2: Homogeneous precipitation of n-CeO2.

19
Nanometrology

Nanotube Processing and Characterization

Single-wall carbon nanotubes (SWNTs) exhibit

remarkable physical properties, and there is

considerable interest in using them as nanoscale

building blocks for a new generation of

applications. Despite this promise, fundamental

issues related to the dispersion, fractionation,

orientation, and manipulation of individual

single-walled carbon nanotubes remain

unresolved, and efficient bulk processing schemes

do not exist. We are working at the scientific front

of this rapidly emerging field to establish research

protocols that will help ensure that this new

technology progresses as quickly and efficiently

as possible, but with uniformly high standards.

Barry J. Bauer, Kalman Migler, and Erik K. Hobbie

Upon their discovery in 1991, carbon nanotubes

were recognized as ideal materials for nanotechnology

applications. Properties of carbon nanotubes differ

vastly depending on their diameter and chirality, and

interest in these materials stems from their extraordinary

combination of properties: superior thermal conductivity,

electrical conductivity, and mechanical strength.

Nanotubes are thus attracting great attention for

emerging technologies such as bio-chemical sensors,

next generation displays, and nano-electronics.

Regardless of the ultimate applications, nanotubes

clearly represent the most important new class of

materials in the past 15 years.

However, application development is plagued by

inconsistent sample quality, compounded by a lack of

consensus on material characterization methods and by

poor measurement reproducibility. The quality

problems plaguing the nanotube community were

described in a recent news article in Nature which

stated, “the situation will not improve until an external

body introduces standards that suppliers can follow.”

Few people were surprised by the conclusion of the

recent workshop: NIST must take the lead in a

quantitative nanotube metrology that will allow

suppliers and customers to develop standards for

the developing industry.

The Nanotube Processing and Characterization

Project within the Polymers Division is actively engaged

in this effort. As a starting point, we are currently using

small-angle neutron scattering (SANS) to quantify the

degree of SWNT dispersion using a variety of dispersion

chemistries (Figure 1) and, in doing so, have identified

DNA wrapping as desirable for the purpose of fractionating

SWNTs by length, diameter, chirality, and band structure.

Figure 2: Refractive index and viscosity as a function of elution

time in a size-exclusion chromatograph from DNA wrapped

SWNTs, showing clear separation by length.

Figure 1: Measured SANS profiles obtained for two different

SWNT dispersion chemistries, showing how DNA wrapping

provides superior dispersion to other methods, such as chemical

functionalization.

Taking this one step further, we have begun using

size-exclusion and ion-exchange chromatography to sort

SWNTs by length and chirality (Figure 2). Following

the protocol pioneered by DuPont researchers, we are

producing ultra clean SWNT fractions that will be

characterized with a broad suite of NIST metrologies.

These results will in turn be used to establish universal

scientific standards for SWNT purity and dispersion.

Contributors and Collaborators

W. Blair (Polymers Division, NIST); A. Hight

Walker (Optical Technology Division, NIST);

T. Yildirim (NIST Center for Neutron Research);

M. Pasquali (Rice University); M. Zheng (DuPont)

20
Carbon Nanotube Applications: The Role of Nanotube Alignment

Carbon nanotubes are currently being produced

by over 50 companies worldwide, with scale-up

progressing at a rapid rate. Of particular importance

for many potential applications is nanotube

alignment, which can affect thermal, mechanical,

and electrical properties. We are developing

methods to deposit and grow aligned nanotubes

on a variety of measurement platforms, as well

as to measure the degree of alignment achieved.

Stephanie A. Hooker

Carbon nanotubes are truly revolutionary materials,

exhibiting properties vastly different than any

other bulk form of carbon. Their unique combination

properties make them valuable for electronics, advanced

structures, biotechnology, and thermal management.

However, reliable property measurement continues to

prove difficult due to supplier variability, difficulties

manipulating materials at this small scale, and physical

and chemical interactions (e.g., with substrates, contacts,

other nanotubes, and the surrounding environment).

Alignment of the individual nanotubes also plays a

significant role in dictating ultimate performance.

One potential application for which alignment

is particularly critical is absorptive coatings for infrared

detectors. Many such detectors are based on pyroelectric

crystals that become electrically polarized with temperature

changes. To enhance response, coatings are applied

to improve heat transfer. Carbon nanotubes are an

excellent choice for such coatings due to their high

thermal transport, which can be tailored by varying

diameter and orientation (i.e., alignment). Alignment

in such coatings is often achieved using chemical

vapor deposition (CVD). Unfortunately, however,

pyroelectric crystals present new challenges for CVD

growth, as high temperatures, reducing atmospheres,

and metal catalysts are required. When these are

combined, undesirable (and irreversible) changes in the

pyroelectric crystal are observed. Recently, however, we

demonstrated a new combination of catalyst, barrier layer,

growth temperature, and processing gas mixture that

permits direct synthesis of vertically aligned nanotube

arrays on lithium niobate (LiNbO3) and lithium

tantalate (LiTaO3) pyroelectric crystals (Figure 1).

Figure 1: SEM image of vertically aligned nanotubes grown on

LiNbO3 at 725 °C. Critical to the process is a thin silicon nitride

(Si3N4 ) barrier layer, preventing catalyst diffusion into the crystal.

The graph shows the associated spectral response of the crystal

after application of the coating.

Nanotube alignment is also important for many

other applications, including those in electronics and

advanced structures. One measurement technique with

promising sensitivity to tube alignment is Brillouin Light

Scattering (BLS). In FY05, we used BLS to evaluate a

highly-aligned single-wall nanotube rope. The resulting

spectra showed a distinct peak associated with the

rope, much different than the broader pattern previously

reported for a more randomly aligned nanotube

network. BLS is also being explored in conjunction

with nanotube separation techniques to provide an

indication of size exclusion.

In FY05, we also helped organize a 2nd joint

NASA–NIST workshop on Measurement Issues in

Single-Wall Carbon Nanotubes. This meeting, held

January 26–28, 2005, addressed challenges in measuring

purity and dispersion quality. Over 75 technical and

business leaders participated, debating a wide portfolio

of characterization tools including Raman spectroscopy,

near-IR spectroscopy, thermogravimetric analysis, and

electron microscopy. These techniques are currently

being drafted into a Recommended Practice Guide,

which will then be adapted by IEEE into a Purity

Standard for Carbon Nanotubes.

Contributors and Collaborators

W. Johnson, S. Kim, T. Oreskovic, P. Rice, V. Tewary,

N. Varaksa (Materials Reliability Division, NIST); K. Migler

(Polymers Division, NIST); S. Freiman (MSEL);

S. Arepalli, L. Yowell (NASA-JSC); R. Mahajan

(University of Colorado); R. Hauge (Rice University)

Figure 2: TEM image of a single-wall carbon nanotube rope

(courtesy of Rice University). The high degree of alignment in the

rope was observed in the BLS spectrum to the right.

Nanometrology

21
Combinatorial Adhesion and Mechanical Properties

Traditional methods for evaluating the engineering

properties of polymers are time-consuming and

inherently single specimen tests. Current market

drivers increasingly demand rapid measurement

platforms in order to keep pace with competition

in the global marketplace. In this project, we are

delivering innovative combinatorial and highthroughput (C&HT) tools for the physical testing

of materials, built around measurement platforms in

the NIST Combinatorial Methods Center (NCMC).

Christopher M. Stafford

Our current C&HT efforts in this project are

concentrated in two main areas: buckling mechanics

for thin film mechanical measurements and adhesion

testing platforms for probing interfacial adhesion and

fracture. Here, we highlight: (1) the inversion of our

buckling-based metrology to study the mechanical

response of soft polymer gels, (2) application of finite

element analysis to study buckling in multilayer geometries,

and (3) the implementation of our combinatorial edge

delamination test to study the interfacial adhesion

strength of epoxy films.

of our buckling-based technique is that a “modulus map”

can be constructed by measuring the buckling wavelength

as a function of spatial position.

Figure 1: Elastic modulus of model PDMS gels measured via

buckling (■ — gradient modulus specimen, ▲ — single specimens)

and via tensile test (● ).

In addition to our experimental efforts, we are also

utilizing finite element analysis (FEA) to help guide

experimental design in our buckling-based metrology

by verifying the validity of available analytical solutions

when applied to more complex specimen geometries.

For example, we examine a composite film consisting

of a soft layer confined between two stiff layers. In

Figure 2, FEA reveals a critical modulus ratio below

which shear deformation becomes significant, thus the

standard analytical solution can no longer be applied to

measurements in this regime.

As part of the NCMC, we have launched a Focus

Project aimed at developing a C&HT measurement

platform for testing interfacial adhesion and fracture in

thermally cured epoxy materials. This method is based

on the modified edge-liftoff test.[2] In this Focus Project,

we are building capabilities to evaluate the governing

parameters for interfacial delamination and reliability

by fabricating suitable gradient libraries in composition,

thickness, temperature, and applied stress. Industrial

sponsors for this Focus Project are ICI National Starch

and Intel Corporation.

1. C.M. Stafford, et al. Nature Materials 3, 545 (2004).

2. M.Y.M. Chiang, et al. Thin Solid Films 476, 379 (2005).

Contributors and Collaborators

M.Y.M. Chiang, S. Guo, J.H. Kim, E.A. Wilder,

W. Zhang (Polymers Division, NIST); Daisuke Kawaguchi

(Nagoya University); Gareth Royston (University of

Sheffield)

Figure 2: Normalized wavelength versus modulus ratio of a

tri-layer thin film. E2 and E1 are the moduli of the soft and stiff

layer, respectively. The solid line is the analytical solution.

Nanometrology

This year, we applied our buckling-based metrology[1]

to measure the elastic modulus of soft-polymer gels. Elastic

modulus is an important design criterion in soft polymer

gels for biomedical applications since it impacts critical

properties such as adhesion, swelling, and cell proliferation

and growth. Leveraging our C&HT buckling-based

metrology, we can rapidly assess the elastic modulus of

polymer gels by inverting the experimental design: the

buckling of a sensor film of known modulus and thickness

reports the elastic modulus of the substrate, Es. Figure 1

illustrates the accuracy of our approach as compared to

traditional tensile tests on the same material. One advantage

22
Soft Nanomanufacturing

assembly applications, image analysis was replaced by

embedded electronic sensors that detect the presence of

a particle and its size (Figure 1). This electronic signal

activates a valve to isolate a set of particles. Electronic

detection is further advantageous because it is readily

scalable to smaller particles. In comparison to previous

systems, the valves we have developed are also

advantageous, since they are not limited to shallow

channel profiles.

Figure 1: Inline particle characterization and counting. In the

image, a polystyrene particle is seen passing electrodes (dark).

At right is shown a bimodal size distribution of liquid drops

produced at a T-junction upstream.

Figure 2: Tubular structures (right) arise from the simulated

organization of triangular arrangements of dipole particles,

shown schematically at left.

High-throughput sensing and processing methods

require precision flow design and control, such as we

demonstrated and reported previously by a microfluidic

analog of the four-roll mill. Advancing beyond, we

developed a framework for generating chaotic flow

in microchannels (described in a separate highlight).

Theoretical simulations probe the organization of

geometrically and electrostatically asymmetric target

particle arrangements (Figure 2). These demonstrate

the relationship between particle symmetry and

organized structure. Depending on this symmetry,

the assemblies exhibit filaments, sheets, tubes and

icosahedra. Whereas ordinary phase separation

is driven by attractive and repulsive interactions,

self-assembly of more complex and finite-sized

structures requires directional interactions.

Of consequence for sensor applications, organization

kinetics were also investigated. In particular, nucleating

agents were found to control the kinetics of assembly

and, in polymorphic systems, to specify unique

structure.

Contributors and Collaborators

F. Phelan, Jr., J. Douglas, K. Migler, H. Hu, P. Stone,

J. Taboas, K. VanWorkum (Polymers Division, NIST);

Y. Dar, S. Gibbon (ICI/National Starch); M. McDonald

(Procter & Gamble); D. Discher, V. Percec (University

of Pennsylvania); R. Tuan (NIH)

Nanomanufacturing is widely noted as a central

challenge of nanotechnology. In the realm of soft

materials and suspended particles, it is necessary

to design particle interactions, manipulate

self-assembly processes, and measure what is

produced. Guided by theoretical simulations,

we are therefore developing high-throughput

microfluidic methods for particle characterization,

processing, assembly, and on-chip quality control.

Steven D. Hudson

The intricacy of biological systems inspires the

design of artificial systems that also function

through dynamic self-assembly and in-situ monitoring

and self-correction.

Our industrial partners identified measurement of

interfacial tension as a first hurdle for high-throughput

microfluidic fluids analysis. Particle processing and

assembly methods represent the next hurdle. In this

project, high-throughput tools are developed for

these purposes, and theoretical simulations identify

particle arrangements whose dynamic assembly and

disassembly is promising for sensor applications.

High-throughput measurement of drop shape

by image analysis represents the cornerstone of an

instrument, developed in collaboration with industrial

sponsors, that determines interfacial tension between

fluids. The measurement principle is simple and

robust — drops are stretched by known viscous

forces as they traverse a constriction in the channel.

The computer controlled system tracks drop position

and deformation more than one hundred times a second.

However, systems that count, isolate, and direct the

assembly of particles must operate more efficiently to

enable internal feedback mechanisms. Therefore, for

Nanometrology

23
Defects in Polymer Nanostructures

Nanostructured materials create new and unique

functionality through the accurate placement,

precise shaping, and chemical modification of

nanometer scale patterns. Such materials are to

be the basis of a wide range of emerging nanotechnologies that span optics, data storage, and

biomembranes. In each of these applications,

defects in pattern placement, shape, and chemical

composition can compromise device functionality.

The rapid development of these technologies

is currently offset by a lack of quantitative

characterizations of critical defects. We have

initiated this project to develop metrologies for

characterizing critical defects, such as loss of

long-range order, in nanostructured materials.

Ronald L. Jones and Alamgir Karim

The optical, magnetic, and electronic properties of a

film or surface are dramatically changed by the

inclusion and placement of nanometer-scale patterns.

The capability to adjust material properties in this

manner is central to the development of sub-wavelength

optics, high selectivity biomembranes, nanoparticle

synthesis, and ultrahigh capacity data storage. In each

of these applications, variations in pattern shape and

placement can drastically alter functionality and device

viability.

Fabrication of nanostructured surfaces is performed

through a wide range of patterning platforms. While

photolithographic techniques are traditional routes

toward precise patterning, the high cost and complexity

of patterning at nanometer length scales has spawned

a variety of alternative techniques such as nanoimprint

lithography (NIL), self-assembly, and templated

self-assembly. Each fabrication technique strives

against a common set of critical defects such as

variation in pattern placement, chemical uniformity

across the pattern cross section, and precision in

pattern shape.

To address the needs of this emerging technological

area, we have initiated a new program to develop

metrologies for long-range order, a critical parameter

in optical and data storage applications. Currently,

long-range order is quantified from Fourier transforms

of real-space microscopy images. However, the

disparity in the pattern length scale (~ 10 nm) and the

length scale of ordering (~ 100 μm) challenges the

measurement range of existing techniques based on

scanning electron and scanning probe microscopies.

Visible light probes are often complicated by complex

interactions with nanometer scale features.

Using small angle x-ray scattering (SAXS), we are

developing quantitative descriptions of long-range order,

grain size, and pattern shape in hexagonally arrayed

cylinders produced on silicon substrates using both

nanoimprint lithography (NIL) and self-assembled

block copolymers (BCP).

Figure 1: Scanning electron

microscopy image showing

a regular array of hexagonally

packed columns formed in

silicon oxide.

Figure 2: SAXS data from arrays of hexagonally packed columns

formed by NIL (left) and self assembly (right).

For each method of pattern formation, long-range

order results in a characteristic diffraction pattern.

However, the occurrence of a hexagonal diffraction pattern

from the NIL pattern indicates a single crystal spanning

the entire 150 x 150 μm beam spot, while the BCP film

consists of multiple, randomly oriented crystals. In both

cases, systematic errors in the placement of the patterns

on the lattice create a characteristic decay in the intensity

as a function of the distance from the beam center.

In addition to developing metrologies for long-range

order, we continue to develop a suite of metrologies that

address critical needs in a wide range of nanostructured

materials applications. These include nanostructured

surfaces for adhesion and wettability, as well as

nanostructured materials designed for unique

electro-optical and magnetic properties.

Contributors and Collaborators

J.F. Douglas (Polymers Division, NIST);

S. Satija (NIST Center for Neutron Research);

R. Briber (University of Maryland); H.-C. Kim (IBM)

Nanometrology

24
Critical Dimension Small Angle X-Ray Scattering

The feature size in microelectronic circuitry is

ever decreasing and now approaches the scale

of nanometers. This creates a need for new

metrologies capable of non-destructive

measurements of small features with sub-nm

precision. NIST has led the effort in developing

small angle x-ray scattering to address this need.

This x-ray based metrology has been included in

the ITRS roadmap as a potential metrological

solution for future generation microelectronics

fabrication. Other applications of this

technique in areas such as nano-rheology

and nanofabrication are being explored.

Wen-li Wu and Ronald L. Jones

The demand for increasing computer speed and

decreasing power consumption continues to shrink

the dimensions of individual circuitry components

toward the scale of nanometers. When the smallest,

or “critical”, dimensions are < 40 nm, the acceptable

tolerance will be < 1 nm. This creates significant

challenges for measurements based on electron

microscopy and light scatterometry. Device viability

also requires the measurement be non-destructive.

In addition, the continuing development of new materials

for extreme ultraviolet photoresists, nanoporous low-k

dielectrics, and metallic interconnects all require

high-precision dimensional measurements for process

development and optimization.

To address industrial needs, we are developing a

high-precision x-ray based metrology termed Critical

Dimension Small Angle X-ray Scattering (CD-SAXS).

This technique is capable of non-destructive

measurements of test patterns routinely used by

microelectronic industries to monitor their fabrication

process. A collimated monochromatic x-ray beam

of sub-Å wavelength is used to measure the pattern

dimensions on a substrate in transmission mode.

CD-SAXS has previously demonstrated a capability

for sub-nm precision for periodicity and line width

measurements.

This year, we have extended the capabilities to

provide more detailed quantifications of the pattern

cross section. This includes both basic dimensions,

such as pattern height and sidewall angle, as well as the

depth profile of the sidewall damage of nano-patterned

low-k dielectrics. The capability to provide basic

dimensions is complementary to existing analyses

provided by SEM, however CD-SAXS offers significant

advantages in its non-destructive capability. In contrast

to visible light scatterometry, detailed information on

refractive indices and composition of the pattern are not

required for data reduction. These capabilities and the

ability to measure patterns approaching dimensions of

10 nm have led to the inclusion of CD-SAXS on the

International Technology Roadmap for Semiconductors

(ITRS) as a potential metrology for the 45 nm

technology node and beyond.

So far, all CD-SAXS measurements have been

carried out at the Advanced Photon Source of

Argonne National Laboratory. As an important step

in demonstrating the potential of technology transfer,

we are constructing the world’s first laboratory

based CD-SAXS instrument. When completed, this

instrument will serve as a prototype for lab-based tool

development as well as a world-class metrology tool

for nanotechnology research.

Future efforts will develop capabilities for

quantifying defects and features with complex shapes

such as vias or contact holes. In addition, we will

continue to expand efforts in supporting other

nanofabrication technologies such as those based

on nanoimprint and self assembly.

Contributors and Collaborators

C. Soles, H. Lee, H. Ro, E. Lin (Polymers Division,

NIST); K. Choi (Intel); D. Casa, S. Weigand, D. Keane

(Argonne National Laboratory); Q. Lin (IBM)

Figure 1: Diffraction patterns collected over a range of sample

rotation angles. The distance between the pronounced horizontal

ridges provides the sidewall angles β, while the relative intensity

and placement of the other diffraction spots provide periodicity,

line width, and line height. [qx = 4 π sin(θ /2)/λ, where θ is the

angle relative to the diffraction axis and λ is the wavelength of

the radiation.]

Nanometrology

25
Nanoimprint Lithography

Nanoimprint lithography (NIL) is emerging as a

viable next generation lithography with a high

throughput and a patterning resolution better than

10 nm. However, wide-spread availability of such

small nanoscale patterns introduces new metrology

challenges as the ability to pattern now surpasses

the capability to measure, quantify, or evaluate the

material properties in these nanoscale features.

We develop high-resolution metrologies to augment

and advance NIL technology, with current focus

on characterizing shape and the fidelity of

pattern transfer.

Christopher L. Soles and Ronald L. Jones

Nanoimprint Lithography (NIL) is a conceptually

simple process whereby nanoscale patterns are

written once into a master, typically Si, quartz, or some

other hard material, using a high resolution but slow

patterning technology such as e-beam lithography.

This master can be rapidly and repeatedly replicated

by stamping it into a softer resist film. This imprint

replication technique is a cost-effective way to combine

the high-resolution patterning of e-beam lithography

with the high throughput of a stamping process.

cross-section (height, width, side-wall angle) with

nm resolution. Likewise, specular x-ray reflectivity

(SXR) was introduced to quantify the pattern

cross-section and the residual layer thickness with nm

resolution. In turn, these accurate shape metrologies

enable quantitative studies of imprint resolution and

the stability of nanoscale imprinted patterns.

Using CD-SAXS, we demonstrated the fidelity of

pattern transfer concept. The pattern cross-sections

in the master and the imprint were independently

characterized and then compared, to quantify how well

the resist material fills and replicates the features of

the master. Varying the imprint temperature, pressure,

time, and the molecular mass of the imprint material

impacts the fidelity of pattern transfer process. We

also tracked the in-situ evolution of the cross-section

while the patterns were annealed close to their glass

transition. Rather than a viscous decay, the patterns

decreased in height much faster than they broadened in

width, owing to the residual stresses in the structures

induced by the imprinting procedure. These residual

stresses appear to increase with molecular mass,

leading to faster rates of pattern decay in higher

molecular mass resists.

NIL holds great promise in semiconductor

fabrication. The high resolution and low cost of

ownership make NIL attractive in comparison to

expensive next-generation optical lithography tools.

However, over the past few years, the interest in NIL

has dramatically expanded beyond the realm of

traditional CMOS applications. NIL-based solutions

are being implemented for optical communications,

memory, displays, and biotechnology. Because of these

emerging niche applications, NIL is quickly becoming

a widely used and versatile nanofabrication tool.

Our objective is to develop metrologies that are

crucial to advancing NIL as an industrially viable

patterning technology. Initial efforts have focused on

developing and applying very accurate pattern-shape

measurements. Critical dimension small angle x-ray

scattering (CD-SAXS) is a transmission x-ray scattering

technique that can quantify the pattern pitch and

SXR was used to quantify the residual layer

thickness, pattern height, and the relative line shape

cross-section. The residual layer is the thin layer of

resist that the master is unable to fully displace as it is

pressed into the resist film. Precise knowledge of the

residual thickness is critical for subsequent etching

processes. The key to this measurement is that the

x-rays average density over length scales larger than

the sub-μm dimensions of the patterns. This leads to

the bilayer equivalency model shown above where the

patterns can be modeled as a uniform layer of reduced

density to extract pattern height and residual layer

thickness with nm precision. Like CD-SAXS, SXR

quantitatively compares the imprint and the mold to

evaluate the fidelity of pattern transfer.

Contributors and Collaborators

H.W. Ro, H.-J. Lee, A. Karim, E.K. Lin, J.F. Douglas

(Polymers Division, NIST); W. Wu (MSEL Office,

NIST); S.W. Pang (University of Michigan); D.R. Hines

(University of Maryland); C.G. Willson (University of

Texas–Austin); L. Koecher (Nanonex); D. Resnick

(Molecular Imprints)

Nanometrology

26
Nanomagnetodynamics

In order to pursue the rapid development path

set out for hard drives and magnetic memory,

industry needs the ability to measure and control

magnetization on nanometer length scales and

nanosecond time scales. This project focuses on

the metrology of spin dynamics and damping in

magnetic thin films, especially on the properties of

lithographically prepared edges of magnetic films.

Robert D. McMichael

We develop measurement techniques to determine

the static and dynamic properties of both

continuous and patterned thin films of technologically

important ferromagnetic metals and their interfaces

with normal metals. The primary results this year

include measurements of the affects of interfaces and

interface roughness on magnetization dynamics and

proof-of-concept experiments for measurements of

lithographically prepared magnetic edges. These results

have been communicated to the magnetic data storage

industry through conference presentations, journal

articles, and site visits.

Although the edge metrology aspect of the

project has just started, we have already performed

proof-of-concept magnetometry of edge saturation

fields and ferromagnetic resonance measurements of

localized edge modes (see Figure 2). These measurements

are interpreted through corresponding micromagnetic

modeling of the static and dynamic behavior of spins

near edges. The stage is also set for magnetoresistive

measurements that would be more suitable for

wafer-level probing of the lithography process.

Contributors and Collaborators

J. Rantschler, B. Maranville, J. Mallett, T. Moffatt,

W. Egelhoff, Jr., A. Chen (Metallurgy Division, NIST);

C. Ross, J. Cheng (MIT)

Figure 1: Damping as a function of roughness in Permalloy

films on thick Cu substrates. The quadratic behavior is explained

by a model featuring eddy currents that are excited by the

roughness-induced stray magnetic fields in the copper.

Figure 2: Image composed of 180 FMR spectra measured on an

array of Permalloy stripes. An AFM image of the stripes is shown

in the inset. At 90 ° the applied field is perpendicular to the

stripes, and the peak is the resonance of the edge modes.

It is well known that surface affects and interfacial

affects are important in nanostuctured materials.

This is especially true for magnetic materials, where

long-range interactions couple the surface magnetism

to the bulk. Figure 1 shows a set of measurement

results that show how interfacial properties affect

damping in Ni80Fe20, (Permalloy) on a copper substrate.

The increased damping is due to the excitation of

eddy currents by magnetostatic fields associated with

the roughness. We have also measured an additional

component of interfacial damping that exists for

smooth interfaces.

We have started a new effort within this project to

develop measurement techniques for characterization

of magnetic edges. The edge properties of a magnetic

device are critical because they affect the shape

anisotropy of a patterned device and the nucleation

of vortices in the critical stage for switching.

While accepted techniques exist for characterizing

bulk materials and interfaces, there are no such

techniques available for characterizing the edges

of thin film devices.

Nanometrology

27
Materials for Ultra-Low-Field Magnetic Sensors

Magnetic sensors play a central role in many

important technologies ranging from health care to

homeland security. A common need among these

technologies is greater sensitivity and smaller size.

A NIST competence program initiated in 2004 is

focusing on developing the metrology that will enable

new generations of magnetic sensors to be produced.

William F. Egelhoff, Jr.

I

n the past decade, small inexpensive magnetic

 sensors have gained important footholds in a wide

variety of technologies. Sales of small inexpensive

magnetic sensors have been soaring. However, one

relatively neglected aspect of these magnetic sensors

has been their sensitivity to very small magnetic fields.

We are focusing on small inexpensive thin-film

magnetic sensors to avoid the disadvantages of SQUIDs.

Existing precedents suggest that such sensors could be

mass produced at a cost of a few cents each, will have

a size measured in microns, and will operate at room

temperature. These characteristics make them ideal

for the applications indicated in Figure 1.

To achieve our goal we will need magnetic thin

films of great sensitivity. The best thin films previously

known had susceptibilities of a few thousand. In our

first year of work, we have already achieved values

above 100 thousand.

One of the prime applications that we may impact

is magneto-cardiography, or imaging the beating heart

in real time. In principle, magneto-cardiography could

give very high quality 3-D images. However, at present,

SQUID-based magneto-cardiography is hugely expensive,

has poor resolution, and is practiced only at a few research

institutions. If small, inexpensive sensors could make

high-resolution magneto-cardiography generally available,

it would change the practice of cardiology. The following

quote arose in a discussion of our plans.

Figure 1 indicates, for particular applications, the

range of fields that the sensor must be able to detect

and the range of frequencies at which the fields appear.

For comparison, the Earth’s magnetic field is about 104

times larger than the top value of Figure 1. The plots

of “Present technology” and “Our sensitivity goal” in

Figure 1 indicate that deep inroads can potentially be made

into important technologies if we can reach our goal.

It should be pointed out that the technique of

superconducting quantum interference devices (SQUIDs)

can already reach sensitivities corresponding to the

bottom values of Figure 1. Unfortunately, SQUIDs are

expensive, bulky, and require cryogenic cooling. These

factors rule out SQUIDs for all applications except

those for which size and cost are not a factor and for

which cryogenic cooling is not prohibitively inconvenient.

Figure 1: A plot of the sensitivity to very small magnetic fields

that is required for various applications as a function of the

frequency of the signal to be detected. Also indicated are the limits

of present technology for small inexpensive solid-state sensors

and the goals of the Competence Program.

Nanometrology

“Real-time magneto-cardiography with 1 cm resolution

would have revolutionary diagnostic impact.”

Bob Balaban, Director

National Heart, Lung, and Blood Institute

National Institutes of Health

As Figure 1 would suggest, magneto-encephalography

may be too demanding an application for the magnetic

sensors we envision. However, it is always difficult to

forecast the limits on new technologies. The one thing

that is very clear is that we have very little competition

in this field of research. The companies that currently

produce the small, inexpensive magnetic sensors do not

have active research and development programs in the

area of ultra-low fields. The narrow profit margins

for existing products will not support such programs.

This situation puts NIST in an ideal position to take

the lead and perform a high-risk/high-payoff research

program that would not otherwise be undertaken.

Contributors and Collaborators

R. McMichael, C. Dennis, F. Johnson, B. Maranville,

J. Rantschler, A. Shapiro (Metallurgy Division, NIST);

J. Unguris (Physics Lab, NIST); D. Pappas, S. Russek

(EEEL, NIST)

28
A New Type of Antisymmetric Magnetoresistance

in Materials with Perpendicular Anisotropy

When the magnetization reverses direction in a

ferro-magnet upon the application of a reversed

magnetic field, it usually occurs by the nucleation

of local domains with a reversed magnetization

vector which subsequently grows to envelop the

whole material. The ease (or difficulty) by which

such a process occurs is key to determining

how useful that material will be for its intended

application. The metrology for detecting, measuring,

and imaging the process in various classes of

materials is being developed in this project. This

knowledge is necessary for quick implementation

of new magnetic materials for the recording,

refrigeration, theft control, and power industries.

Robert D. Shull, Valerian I. Nikitenko,

and Alexander J. Shapiro

The simplest way to detect the magnetic state of a

material is to sense the magnetic field that surrounds

it. However, as magnetic devices are reduced in size,

the magnitude and spatial extent of these fields are also

reduced. Recently, very sensitive field sensors (e.g., giant

(GMR), tunneling (TMR), and colossal (CMR) magnetoresistance detectors) have been developed which are

based upon measuring the resistance changes caused by

the presence of small magnetic fields. In all these devices,

the resistance changes are all symmetric with respect to

the sign of the magnetic field. We report here the discovery

of a new magnetoresistance effect in a multilayer which

changes sign with changes in the direction of the magnetic

field. Furthermore, the phenomenon is found to be caused

by the presence of domain walls running perpendicular

to the current direction.

Figure 1 shows the antisymmetric Hall resistance

(RH) and in-line resistance (R) for a [Co(0.6 nm)/

Pt(1 nm)]4 multilayer as the magnetic field (H) is

cycled between positive and negative fields. Note that

∆R(H) = –∆R(–H) in (b), indicating the magnetoresistance

(MR) is negative when switching from negative fields

to positive fields while it is positive when switching

from positive fields to negative fields, is similar to the

Hall effect but quite different from normal MR phenomena.

Figure 1: Arrows denote the sequence of measurements; inset

shows the domain patterns correlated with magnetization reversal

at the MR and RH peaks.

Figure 2: Wedge sample showing: (a) leads for measuring

current, I, and voltage, V; (b) domain positions as a function of

field.

By the controlled creation of a single domain wall

running perpendicular to the current direction (shown

in Figure 2), the antisymmetric magnetoresistance has

been shown to be due to the presence of such a domain

wall. This configuration was created by preparing a

trilayer containing a wedge-shaped Co layer (varying in

thickness from 0.3 nm–0.6 nm) sandwiched by 3 nm

thick Pt layers. We had earlier found in such a trilayer

that one could create such a single domain wall running

perpendicular to the wedge at a position along the

wedge determined by the magnitude of the reversed

field applied, as shown in Figure 2(b).

The unusual magnetoresistance effect is due to

circulating currents created at the domain wall due to

the opposite Hall voltages on either side of the wall.

The results, which were published in Phys. Rev. Letters

94, 17203 (2005), provide much more flexibility to the

circuit designers and may point the way to creating

double pole magnetic switches.

Contributors and Collaborators

X. Cheng, S. Urazhdin, O. Tchernyshyov, C. Chien

(Johns Hopkins University)

Nanometrology

29
Nanostructure Fabrication Processes:

Surface & Growth Stress During Thin Film Electrodeposition

The adsorption of species onto a surface alters

the surface stress since the local interaction of

each adsorbate alters the bond strength between

neighboring atoms on the surface. Our immediate

focus is to use surface stress to examine substrateadsorbate interactions of various molecules for

self-assembled monolayers (SAM). A natural

extension of this work is to examine the surface

stress associated with adsorbate-adsorbate lateral

interactions. This could lead to a general in situ

metrology for control of surfactants and adsorbatebased surface modification for a variety of

molecular electronics and sensor applications.

Gery R. Stafford and Carlos Beauchamp

Surface stresses arise because the atomic

configuration of atoms at a surface is different

from the bulk. Interior atoms exert a stress on the

surface atoms, i.e., the surface stress, which moves

them out of the positions they would occupy in a bulk

crystal configuration. The adsorption of species onto

the surface can be expected to alter the surface stress

since the local interaction of each adsorbate will alter

the bond strength between neighboring atoms on

the surface. An understanding of adsorbate-induced

surface stress is critical to emerging technologies such

as molecular electronics, nanostructure fabrication,

and chemical/biological sensors.

We have established a Class II (1 mW) HeNe optical

bench dedicated to in situ measurement of surface and

growth stress during electrochemical processing using

the wafer curvature method. Measurements are made on

a borosilicate glass cantilever onto which 250 nm of Au is

evaporated. The curvature of the substrate is monitored

while in solution and under potential control by reflecting

a HeNe laser off the glass/metal interface, through a series

of mirrors, and onto a position-sensitive detector. The

relationship between force exerted onto the cantilever by

the electrochemical processes occurring at the Au-solution

interface and the radius of curvature of the cantilever

is given by Stoney’s equation. Forces on the order of

0.008 N/m (23 km radius of curvature) can be resolved.

This is sufficient to study the adsorption of molecular

monolayers onto the electrode surface. As a demonstration,

we have measured the surface stress associated with

reversible monolayer adsorption of both sulfate and chloride

ions onto the Au surface from aqueous solutions.

Figure 1 shows the linear sweep voltammetry (three

consecutive transients taken 5 minutes apart) as well

as the associated surface stress of a (111)-textured Au

electrode in 1.0 mol/L H2SO4. As the electrode potential

is swept in the positive direction from 0.2 V, a positive

current is measured as the result of sulfate ion adsorption

onto the Au surface. As negative charge is removed from

the electrode with potential increase, the surface stress

moves in the negative (compressive) direction, consistent

with charge redistribution models that appear in the

literature. The adsorption of electronegative species such

as sulfate ion increases the compressive trend in the surface

stress by removing additional charge from the Au surface.

Figure 2 is a plot of the surface stress vs. charge density

for the sulfate adsorption/desorption process. The data

suggest that the slope of the stress-charge curve provides

a measure of adsorbate strength that can be used to

quantify adsorbate-substrate interactions.

Contributors and Collaborators

U. Bertocci (Metallurgy Division, NIST);

C. Zangmeister (Process Measurements Division, NIST)

Figure 1: Linear sweep voltammetry and surface stress associated

with sulfate adsorption on (111)-textured Au in 1.0 mol/L H2SO4.

Figure 2: Surface stress vs. charge density associated with

sulfate adsorption on (111)-textured Au in 1.0 mol/L H2SO4.

Nanometrology

30
Multiscale Modeling of Quantum Dots in Semiconductors

A computationally efficient multiscale model has been

developed for a quantum dot in a semiconductor.

The model links the subnano, nano, and macro length

scales by integrating the powerful techniques of

molecular dynamics, lattice-statics, and continuum

Green’s functions. The model is applied to Ge

quantum dots of realistic sizes up to 8 nm in Si.

The topography of a free surface of Si, containing

a buried quantum dot, is calculated. This surface

can be measured and used to characterize the QD.

The model can also predict the formation of arrays

of quantum dots and can be a useful tool for

strain engineering of quantum dots.

Vinod K. Tewary and David T. Read

Technical Description

Currently there is a strong interest in modeling the

mechanical characteristics of quantum dots (QDs)

in semiconductors because of their potential application

in powerful new devices like huge memory systems,

ultra low threshold lasers, and quantum computers.

A QD has to be modeled at the following scales:

(i) the core region (sub-nanometer) where the nonlinear

effects may be significant; (ii) the region of the host

solid around the QD (nanometer); and (iii) free surfaces

and interfaces in the host solid (macro). Modeling is

needed for interpreting measurements and design of

new devices. A multiscale model is especially useful

for strain engineering of QDs and their arrays.

A QD causes lattice distortion in the host solid

which is manifested as strain and a displacement field

throughout the solid. Strains and a displacement field at

a free surface can be measured and used to characterize

the QD. A strain field determines the elastic energy of

the system and is mainly responsible for the formation

of arrays of QDs. The strain and displacement field are

essentially a continuum-model parameter whereas the

lattice distortions are discrete variables that must be

calculated by using a discrete lattice theory. Hence one

needs a multiscale model that relates the discrete lattice

distortions at the microscopic scale to a macroscopic

parameter such as strain.

We have developed a computationally efficient

multiscale model that links the length scales from

sub-nano to macro and can be used on an ordinary

desktop computer. The model integrates classical

molecular dynamics (MD) with Green’s functions

(GF). We use MD at the core of the QD to account

for the nonlinear effects and the lattice-statics GF, G,

near the quantum dots which reduces asymptotically to

the continuum GF near a free surface. The displacement

field in this model containing N atoms is given by:

u(l) = (1/N) ΣkG(k) F(k) exp(ik.l)

where l is a lattice site, k is a reciprocal space vector,

and F(k) is the Kanzaki force which is calculated by

using MD. For large l, the above equation reduces

asymptotically to the macroscopic continuum while the

discrete lattice effects are retained in F(k). Thus, our

model is truly multiscale as it seamlessly links the discrete

atomistic effects in F(k) to macroscopic scales through

the GF and directly relates microscopic lattice distortion

at nanoscale to measurable macroscale parameters.

Accomplishments

Figure 1: Topography of a free surface in Si due to a buried

1.1 nm Ge QD in Si.

We are now able to model quantum dots of realistic

sizes, up to about 8 nanometers, on a desktop computer.

To model such a large QD, it is necessary to include at

least a million atoms in the host lattice. An attempt to

model such a large system using only MD would require

a huge computational effort and involve somewhat

arbitrary assumptions for relating discrete lattice

distortion to continuum parameters. We have calculated

surface strains and surface topography (Figure 1)

which can be measured and used to characterize the

QDs. Note the local minimum at (0,0). A similar

minimum occurs in the strain energy for certain QDs.

The position of the minimum is a possible favorable

location for the nucleation of a new QD.

Contributors and Collaborators

R.R. Keller (Materials Reliability Division, NIST);

B. Yang (Florida Tech); R. Pandey (Michigan Tech

University)

Nanometrology

31
Brillouin Light Scattering:

Dynamic Elastic and Magnetic Properties of Nanostructures

Brillouin light scattering can be used to provide

information on acoustic waves and spin waves

at gigahertz frequencies in nanometric thin-film

materials and devices. During FY05, we focused

on developing the metrology and models for

characterizing waves in several material systems,

including nanoimprinted polymers and ferromagnetic thin films with nanoscale edge effects.

Ward Johnson, Sudook Kim, and

Colm Flannery

Brillouin light scattering (BLS) is an experimental

technique that measures the intensity of spectral

components of light that is inelastically scattered by

vibrational waves (acoustic phonons) or spin waves

(magnons) in a material. Fabry–Perot interferometric

techniques are used to acquire accumulated spectra

through repeated mechanical sweeping of the etalon

spacing.

In the Materials Reliability Division, BLS is being

pursued as a technique for characterizing dynamic

elastic and magnetic properties of a variety of materials

and devices with nanoscale dimensions. During FY05,

research on elastic waves focused on nanoimprinted

polymeric lines (highlighted below), carbon nanotubes,

and polymeric membranes. Research on spin waves

focused on magnon–magnon interactions in Ni81Fe19,

modes localized near edges of ferromagnetic thin-film

structures, and modes excited in spin-momentumtransfer devices.

Research on nanoimprinted polymers was pursued

in collaboration with the NIST Polymers Division,

Colorado State University, and the University of Akron.

The goal of this work is to develop experimental and

analytical methods for characterizing elastic properties,

which are expected to deviate from bulk properties

when one or more dimensions of a nanoline are less

than a few tens of nanometers. Figure 1 shows a

typical BLS spectrum from an array of imprinted

polymethyl-methacrylate (PMMA) nanolines and plots

of dispersion curves from a series of spectra obtained

at various scattering angles. The general character

of the observed modes, except for the lowest, is

determined through Fresnel–Adler calculations (black

lines) for a uniform film with a thickness equal to the

height of the nanolines plus the thickness of a residual

PMMA layer beneath the lines. The lowest-frequency

set of points arises from transverse flexural modes

of the lines. The identification of these modes is

based partly on the correspondence of the data

with calculations of the lowest order flexural modes

(antisymmetric Lamb waves) of a plate with thickness

equal to the width of the nanolines (blue curve in

Figure 1). Finite-element calculations* have been

employed to provide detailed information on the

vibrational displacements, such as those of the

flexural mode shown in Figure 2.

Contributors and Collaborators

C. Soles, C. Stafford (Polymers Division, NIST);

R. McMichael (Metallurgy Division, NIST); P. Kabos,

W. Rippard, S. Russek (Electromagnetics Division,

NIST); P. Heyliger, P. Krivosik (Colorado State University);

R. Hartschuh, A. Sokolov (University of Akron)

Figure 1: (a) BLS spectrum for PMMA nanolines; (b) Measured

dispersion curves (blue circles), calculations for a uniform film

(black curves), and Lamb-wave calculations (blue curve).

Figure 2: Finite-element calculation of displacements of a flexural

mode of a PMMA nanoline.

Nanometrology

Counts (s)

Wave number (μm–1)

32
Program Overview

Materials for Electronics

The U.S. electronics industry faces strong

international competition in the manufacture of smaller,

faster, more functional, and more reliable products.

Many critical challenges facing the industry require

the continual development of advanced materials

and processes. The NIST Materials Science and

Engineering Laboratory (MSEL) works closely with

U.S. industry, covering a broad spectrum of sectors

including semiconductor manufacturing, device

components, packaging, data storage, and assembly,

as well as complementary and emerging areas such as

optoelectronics and organic electronics. MSEL has a

multidivisional approach, committed to addressing the

most critical materials measurement and standards

issues for electronic materials. Our vision is to be

the key resource within the Federal Government for

materials metrology development and will be realized

through the following objectives:

■ Develop and deliver standard measurements and data

for thin film and nanoscale structures;

■ Develop advanced measurement methods needed by

industry to address new problems that arise with the

development of new materials;

■ Develop and apply in situ as well as real-time, factory

floor measurements for materials and devices having

micrometer to nanometer scale dimensions;

■ Develop combinatorial material methodologies for

the rapid optimization of industrially important

electronic and photonic materials;

■ Provide fundamental understanding of the divergence

of thin film and nanoscale material properties from

their bulk values;

■ Provide fundamental understanding, including first

principles modeling, of materials needed for future

nanoelectronic devices.

The NIST/MSEL program consists of projects led

by the Metallurgy, Polymers, Materials Reliability, and

Ceramics Divisions. These projects are conducted in

collaboration with partners from industrial consortia

(e.g., SEMATECH), individual companies, academia,

and other government agencies. The program is

strongly coupled with other microelectronics programs

within the government such as the National Semiconductor

Metrology Program (NSMP). Materials metrology

needs are also identified through the International

Technology Roadmap for Semiconductors (ITRS), the

International Packaging Consortium (IPC) Roadmap,

the IPC Lead-free Solder Roadmap, the National

Electronics Manufacturing Initiative (NEMI) Roadmap,

the Optoelectronics Industry Development Association

(OIDA) Roadmap, and the National Magnetic Data Storage

Industry Consortium (NSIC) Roadmap.

MSEL researchers from each division have made

substantial contributions to the most pressing technical

challenges facing industry, from new fabrication

methods and advanced materials in the semiconductor

industry, to low-cost organic electronics, and to novel

classes of electronic ceramics. Below are just a few

examples of MSEL contributions over the past year.

Advanced Gate Dielectrics

To enable further device scaling, the capacitive

equivalent thickness (CET) of the gate stack thickness

must be 0.5 nm to 1.0 nm. This is not achievable with

existing SiO2/polcrystalline Si gate stacks. High dielectric

constant gate insulators are needed to replace SiO2, and

metal gate electrodes are needed to replace polycrystalline

Si. Given the large number of possible materials choices

for the gate dielectric/substrate and gate dielectric/metal

gate electrode interfaces, the MSEL Ceramics Division

is establishing a dedicated combinatorial film deposition

facility to study the complex interfacial interactions.

This same methodology is applicable to a wide variety

of problems in the electronic materials field.

Advanced Lithography

Lithography is the key enabling technology for the

fabrication of advanced integrated circuits. As feature

sizes decrease to sub-65 nm length scales, challenges arise

because the image resolution and the thickness of the

imaging layer approach the dimensions of the polymers

used in the photoresist film. Unique high-spatial

resolution measurements are developed to identify the

limits of materials and processes for the development

of photoresists for next-generation lithography.

Advanced Metallization

As the dimensions of copper metallization

interconnects on microelectronic chips decrease below

100 nm, control of electrical resistivity becomes critical.

The MSEL Metallurgy Division is developing seedless

deposition methods that will simplify thin-film processing

and result in film growth modes that increase trench

filling, thus lowering interconnect resistivity.

Mechanical Reliability of Microchips

One of the important ITRS challenges is to achieve

effective control of the failure mechanisms affecting

chip reliability. Detection and characterization methods

for dimensionally constrained materials will be critical to

the attainment of this objective. Scientists in the MSEL

Materials Reliability Division are addressing this issue by

focusing on electrical methods capable of determining

the thermal fatigue lifetime and mechanical strength of

patterned metal film interconnects essential to microchips.

Contact: Martin L. Green (Ceramics Division),

Eric K. Lin (Polymers Division)

33
Materials for Electronics

Multifunctional Electronic Ceramics

Materials which exhibit exploitable and coupled

responses to multiple external fields (electric,

magnetic, etc.) present entirely new design

opportunities for multifunctional, miniaturized

devices such as sensors or actuators. The goal of

this project is to establish transferable engineering

principles for multi- and single-phase electronic

ceramics which exhibit a functional response by

one constituent phase/subsystem that is generated

by the response of another phase/subsystem to an

external field.

Igor Levin, Julia Slutsker, and Terrell A. Vanderah

The development of next-generation multifunctional

devices now includes a search for materials exhibiting

simultaneous magnetic, electronic, and/or photonic

responses (e.g., magnetic semiconductors, magnetic

superconductors, multiferroics, etc.). Multiferroic

materials display a coexistence of ferroelectric and

ferromagnetic responses and have attracted particular

interest for several novel device applications including

memories, sensors, and actuators. Self-assembled,

epitaxial heterophase nanostructures consisting of

both ferromagnetic and ferroelectric phases represent

one promising class of multiferroics. The strong

magnetoelectric coupling obtained in these materials is

attributed to the nanoscale distribution of the phases, which

facilitates highly efficient elastic interactions and a strong

magnetic response to an electric field (or vice versa) via

magnetostriction and the piezoelectric effect. The same

elastic interactions also control the self-assembly of the

component phases, so that the architecture and the scale

of the nanostructures can be predicted and controlled

by manipulating the stress state of the film.

We analyzed the affect of stress conditions on the

morphologies of epitaxial, self-assembled nanostructures

using PbTiO3-CoFe2O4 thin films. The two-phase

nanostructures were grown on single-crystal SrTiO3;

the strain conditions were varied by deposition on

differently oriented substrates. Regardless of orientation,

the nanostructures consisted of vertical columns of

ferromagnetic CoFe2O4 dispersed in a ferroelectric

PbTiO3 matrix, or vice versa (Figure 1). However,

the morphologies of these columns and their spatial

arrangements exhibited a marked dependence on substrate

orientation. Phase field modeling of these nanostructures,

which assumed an equilibrium corresponding to the

minimum of elastic and interfacial energies at a given phase

fraction, succeeded in reproducing the morphological

differences (Figure 2). The modeling confirmed that these

differences are related to elastic anisotropy in the film.

Our results, which demonstrate that the architecture of

self-assembled multiferroic nanostructures can indeed be

controlled by a careful choice of the stress conditions,

open a tantalizing opportunity for the rational design

of self-assembled, multifunctional nanostructures.

Research on bulk single-phase materials included

phase equilibria studies of the Bi2O3-Fe2O3-Nb2O5

and Bi2O3-Mn2O3-Nb2O5 systems. Surprisingly,

both systems feature extensive pyrochlore-type phase

fields at compositions requiring mixing of the magnetic

ions with far larger Bi3+ ions on the A-sites, in

apparent violation of traditional substitutional rules.

The pyrochlore phases exhibited relative permittivities

~150, and were readily deposited on Si as crystalline

thin films using pulsed laser deposition. Although the

multiferroic phase BiFeO3 was found to participate in

ambient-pressure phase assemblages, BiMnO3 did not,

and was not stabilized by the presence of Nb5+.

Contributors and Collaborators

P.K. Schenck (Ceramics Division, NIST);

V. Provenzano (Metallurgy Division, NIST);

J. Li, A.L. Roytburd (University of Maryland)

Figure 1: Plane view and cross-sectional images of the

0.33CoFe2O4-0.67PbTiO3 nanostructures grown epitaxially on

(001) and (110) SrTiO3.

Figure 2: Plane view of CoFe2O4-PbTiO3 nanostructures grown

epitaxially on (001), (110), and (111) SrTiO3. For each composition

and orientation, the experimentally observed structure is shown on

the left and the simulation is shown on the right.

34
Spectroscopy, Diffraction, and Imaging of Electronic Materials

We are working to develop, establish, and

provide synchrotron-based metrology, including

instrumentation and technical expertise, for

spectroscopy, diffraction, and imaging techniques

applicable to the study of nanoscale and other

phenomena that are important in the design,

application, and performance of electronic

materials.

Joseph C. Woicik

The epitaxial growth of oxides on silicon opened the

possibility of incorporating many of their unique

electronic properties into silicon device technology.

We have studied the epitaxy and lattice expansion

of SrTiO3 thin films grown coherently on Si(001)

by kinetically controlled sequential deposition.

Coherent growth is achieved by repetition of the

deposition sequence that includes a low-temperature

and high-oxygen partial-pressure step followed by a

high-temperature and low-oxygen partial-pressure step,

thereby suppressing the detrimental oxidation of the

silicon substrate.

Unlike films grown by more traditional

molecular-beam-epitaxy (MBE) methods, these films

are found to have an in-plane lattice constant that

is indistinguishable from the silicon substrate, an

out-of-plane lattice constant that is expanded by an

amount twice that predicted by the bulk elastic

constants of SrTiO3, and a critical-thickness behavior

beyond ~ 2 nm (5 unit cells or 5 monolayers (ML’s)).

The experimentally determined c/a-ratio as a

function of in-plane misfit strain is shown in Figure 1,

for both 5 ML and 10 ML films. The experimental

results are compared to the results of density functional

theory for the c/a ratio of a 5 ML film in coherent

registry with the silicon substrate as shown in Figure 2.

The difference between the two structures in Figure 2

is the presence of OH adsorbates on the surface and

oxygen vacancies at the interface, as revealed by

high-resolution x-ray photoelectron spectroscopy

for films that have been exposed to air.

Materials for Electronics

Figure 1: Measured c/a ratio for 5 ML and 10 ML films as

a function of in-plane lattice mismatch. Also shown are the

predictions of elastic theory and density functional theory (DFT).

Figure 2: Structure of the ideal 5 ML SrTiO3 /Si(001) system (a)

and the system with O vacancies and OH adsorbates (b).

Note the ferroelectric polarization in (b) but not in (a).

 This energetically favorable interfacial-defect/

surface-charge structure compensates the ferroelectric

depolarization field and allows the ferroelectric

polarization in these ultra-thin films that is confirmed by

Ti K-edge x-ray absorption fine-structure measurements.

Contributors and Collaborators

H. Li (Motorola Labs); P. Zschack, E. Karapetrova

(UNICAT); P. Ryan (Ames Lab); C.R. Ashman,

C.S. Hellberg (NRL); A. Allen, D. Black, M. Green,

I. Levin (Ceramics Division, NIST)

35
Theory and Modeling of Electronic Materials

Optimizing the properties of electronic materials

requires fundamental understanding of the origin

of their useful properties and computational tools

that connect atomic-scale knowledge obtained

from first-principles calculations to properties

that emerge at larger length scales. We are

developing first-principles based modeling tools

for calculating the physical properties of materials

as a function of chemical ordering on different

length scales and how these properties respond

to changes in the environment (temperature,

pressure, electric field, etc.). Such techniques

have applications in a variety of areas, including

dielectrics, dilute spin glass magnets, light-emitting

diodes, multiferroics, phase diagrams, piezoelectrics,

semiconductors, and spectroscopy.

Eric J. Cockayne, Richard J. Wagner, and

Benjamin P. Burton

Understanding and predicting the physical

properties of solid solutions is a difficult problem

in general. Even in the simplest case of a harmonic

crystal, the vibrational energy as a function of atomic

arrangement can have a strong affect on the phase

diagram. The calculated maximum temperature for the

miscibility gap in NaCl-KCl is reduced by about 50 %

when vibrational entropy is included, and the agreement

with the experimental phase diagram is much improved.

Many systems with useful electromechanical properties,

such as PbMg1/3Nb2/3O3 (PMN), the relaxor

ferroelectric that is a constituent of the ultrahigh

piezoelectric compound PMN-PbTiO3, are highly

anharmonic. Effective Hamiltonian (Heff) techniques

have been developed to simplify the modeling of

these systems, but the effect of chemical disorder

on the lattice dynamics of solid solutions is not well

understood. We published a methodology, based on

maximum localization, for automatically determining

the appropriate Heff basis for solid solutions and

showed that it correctly reproduces the phonon density

of states for low-frequency phonons. In PMN, these

phonons were determined to be of two types: those

involving displacements of Pb, and those involving

rotations of oxygen octahedra.

Experiments suggest that the relaxor behavior in

PbSc1/2Nb1/2O3 (PSN) is associated with nanoscale

chemically ordered regions in a disordered matrix. We

performed a molecular dynamics simulation of a PSN

Heff on a 320000 atom cell. Polarization fluctuations

are much larger in the chemically ordered regions,

which thus dominate the dielectric behavior of PSN

near its dielectric peak. This work demonstrates the

importance of Heff methods that allow us to make a

detailed investigation of the effects of nanoscale

chemical ordering on dielectric properties.

The semiconductor industry is interested in HfO2

as an alternate gate dielectric material. Experiments

typically show significant numbers of defects in HfO2.

First principles calculations show that O vacancies are

most stable on the 4-fold coordinated O site and that

HfO2 remains insulating with both a neutral and a 2+

charged vacancy. Work is underway to determine how

each kind of vacancy affects the dielectric properties.

Quantitative modeling of mechanical behavior at the

nanoscale requires connecting the large-scale elastic

displacement fields experienced by the whole device to

the small-scale atomistic regions where bond breaking

can mark the initiation of device failure through fracture

or plastic deformation. We are working to develop

multiscale models for connecting the microscopic

applied load in a nanoindentation experiment to the

initiation of the first broken bond. The sample is a

bulk Al single crystal with a <111> surface.

Contributors and Collaborators

S. Tinte, I. Levin (Ceramics Division, NIST);

L. Levine, F. Terrazza (Metallurgy Division, NIST);

A. Chaka (CSTL, NIST); A. van de Walle, M. Astar

(Northwestern University); D.J. Singh (ORNL);

W. Kleeman (University of Duisberg); U.V. Waghmare

(J. Nehru Center for Advanced Scientific Research)

Materials for Electronics

Figure 1: Snapshot of local polarization in PSN model showing

larger polarization and polarization correlations in the chemically

ordered regions (blue) than in the disordered matrix (red).

36
Advanced Materials for Energy Applications

Fundamental understanding, unique

characterization facilities, and standardized

materials and data form the technological basis

for advances in materials for energy-related

technologies. We are working to develop

the metrology required to relate properties

and performance of energy materials to

processing/manufacturing routes via

understanding the roles of chemistry, phase

relations, and microstructure, to establish a

sound physical basis for material system design.

Winnie Wong-Ng, Andrew J. Allen,

Daniel A. Fischer, and Lawrence P. Cook

Achallenge for the U.S. economy in the new

 millennium is for both emerging and mature

industries to provide environmentally friendly,

inexpensive, efficient, compact, and cutting-edge

synergistic technologies for energy conversion,

distribution, and storage applications. This project

aims to facilitate commercialization of energy-related

technologies by addressing various near-term and

long-term materials issues.

The proliferation of portable telecommunication

devices, computer equipment, and hybrid electric

vehicles has created a substantial interest in

manufacturing rechargeable Li-ion batteries that are

less expensive, non-toxic, durable, and small in size

and weight. The electronic structure of the electrode

materials during the electrochemical cycling is

particularly important to the implementation of Li-ion

batteries. This year, we studied the electronic structure

of the Li-ion deintercalated Li(1–x)Co1/3Ni1/3Mn1/3O2

materials with soft X-ray absorption spectroscopy

(XAS) at O K-edge and metal Lα, β-edges, in combination

with metal K-edge XAS spectra in the hard x-ray region

to elucidate the charge compensation mechanism.

We found that a large portion of the charge compensation

during Li-ion deintercalation is achieved in the oxygen

site due to the presence of Co.

Characterization of the triple phase boundary in

solid oxide fuel cells (SOFC), where the electron- and

ion-conducting phases and the gas transport (void)

phases meet, is a priority in understanding SOFC

performance and durability. By combining studies of the

large microstructure scale range, accessible using the

NIST-built ultrasmall-angle x-ray scattering (USAXS)

facility at the Advanced Photon Source, with anomalous

small-angle x-ray scattering (ASAXS) measurements,

it has been demonstrated that ASAXS can provide

the differential contrast for distinguishing between

the ion- and electron-conducting phase morphologies.

Figure 1 shows the spatial variation of the void/solid

surface areas involving the ion-conducting yttria-stabilized

zirconia (YSZ) and lanthanum strontium manganate

(LSM), and Ni that are the electron-conducting phases

in the cathode and anode layers.

Phase equilibria data are critical for the coated

conductor high Tc materials for cable, generator,

fly-wheel, and transformer applications. As an

integral part of a DOE R&D program, phase diagrams

were developed for the Ba-R-Cu-O (R = Tm and Yb)

systems. The “BaF2” process is a promising method

for producing long-length coated conductors.

We have investigated the role of low-temperature melt

and intermediate superlattice phases in the formation

of Ba2YCu3O6+x (Y-213). A new Ba(OH)F phase

(Figure 2) was discovered that may be related to the

low-temperature melting. The interaction of Y-213

with SrTiO3 substrates was studied in terms of

phase equilibria of the Ba-Sr-Y-Cu-Ti-O system.

In collaboration with the University of South Florida,

we have characterized the structure and provided

x-ray reference patterns for two clathrate phases

(Sr8Ga16Ge30 and Cs8Na16Ge136) that are promising

candidates for thermoelectric power conversion

applications. The structure of Na1–xGe3, which

often coexists with Cs8Na16Ge136, was also studied.

Defining the industrial needs for thermoelectric

metrologies and the uses of combinatorial approaches

for materials optimization remain a high priority.

Contributors and Collaborators

F. Biancaniello, M. Green, R. Radebaugh, G. Nolas

(USF); Z. Yang, I. Levin, Q. Huang, R. Feenstra

(ORNL); A. Goyal, V. Maroni (ANL); W.S. Yoon

(BNL); K.Y. Chung, X.Q. Yang, J. McBreen,

M. Balasubramanian, C.P. Grey, J. Ilavsky (APS XOR);

P.R. Jemian (University of Illinois); J. Ruud (GE),

W. Dawson (Nex Tech); A. Virkar (University of Utah)

Figure 2: Structure of

Ba(OH)F.

Figure 1: Spatial variation in

component phase surface areas.

Materials for Electronics

37
Polymer Photoresists for Nanolithography

Photolithography, the process used to fabricate

integrated circuits, is the key enabler and driver

for the microelectronics industry. As lithographic

feature sizes decrease to the sub 65 nm length

scale, challenges arise because both the image

resolution and the thickness of the imaging

layer approach the macromolecular dimensions

characteristic of the polymers used in the

photoresist film. Unique high-spatial resolution

measurements are developed to reveal limits

on materials and processes that challenge the

development of photoresists for next-generation

sub 65 nm lithography.

Vivek M. Prabhu

Photolithography is the driving technology used by

the microelectronics industry to fabricate integrated

circuits with ever decreasing sizes. In addition, this

fabrication technology is rapidly being adopted in

emerging areas in optoelectronics and biotechnology

requiring the rapid manufacture of nanoscale structures.

In this process, a designed pattern is transferred to the

silicon substrate by altering the solubility of areas of

a polymer-based photoresist thin film through an

acid-catalyzed deprotection reaction after exposure

to radiation through a mask (Figure 1). To fabricate

smaller features, next-generation photolithography

will be processed with shorter wavelengths of light

requiring photoresist films less than 100 nm thick and

dimensional control to within 2 nm.

To advance this key fabrication technology,

we work closely with industrial collaborators to

develop and apply high-spatial resolution and

chemically specific measurements to understand

changes in material properties, interfacial behavior,

and process kinetics that can significantly affect the

patterning process at nanometer scales.

This year, we initiated two new collaborations.

With SEMATECH, we are determining the materials

sources of line-edge roughness in model 193-nm

photoresists. With the Intel Corporation, we are

investigating the effect of extreme ultraviolet (EUV)

exposure on pattern resolution of model EUV

photoresist materials. With these partners, we continue

to provide new insight and detail into the complex

physico–chemical processes used in advanced

chemically amplified photoresists. These methods

include x-ray and neutron reflectivity (XR, NR), small

angle neutron scattering (SANS), near-edge x-ray

absorption fine structure (NEXAFS) spectroscopy,

combinatorial methods, solid state nuclear magnetic

Photoresists are multi-component mixtures that

require dispersion of additives, controlled transport

properties during the interface formation, and controlled

dissolution behavior. The fidelity of pattern formation

relies on the materials characteristics. We examine the

influence of copolymer compositions, molecular weight,

and photoacid generator additive size to determine

the root causes of image quality by highlighting

the fundamental polymer physics and chemistry.

In addition, our collaborators test our hypotheses

using 193-nm and EUV lithographic production tools.

Accomplishments for this past year include:

quantification of the developer profile in ultrathin films by

NR and QCM; quantification of the deprotection reaction

kinetics and photoacid-reaction diffusion deprotection

front for resolution and roughness fundamentals by

combined NR and FTIR; photoacid generator miscibility

and dispersion in complex photoresist co- and ter-polymers

by NMR; and aqueous immersion dependence on

photoresist component leeching by NEXAFS.

Contributors and Collaborators

B. Vogt, A. Rao, S. Kang, D. VanderHart, W. Wu,

E. Lin (Polymers Division, NIST); D. Fischer,

S. Sambasivan (Ceramics Division, NIST); S. Satija (NIST

Center for Neutron Research); K. Turnquest (Sematech);

K-W. Choi (Intel); D. Goldfarb (IBM T.J. Watson

Research Ctr); H. Ito, R. Allen (IBM Almaden Research

Ctr); R. Dammel, F. Houlihan (AZ Electronics);

J. Sounik, M. Sheehan (DuPont Elect. Polymers)

Figure 1: Key lithographic process steps; each step requires an

interdisciplinary array of experimental techniques to measure the

polymer chemistry and physics in thin films. A model 193-nm

resist under investigation is shown with the acid-catalyzed

deprotection reaction.

resonance (NMR), quartz crystal microbalance (QCM),

Fourier transform infrared spectroscopy (FTIR),

fluorescence correlation spectroscopy (FCS), and

atomic force microscopy (AFM).

Materials for Electronics

38
Organic Electronics

Organic electronics has dramatically emerged in

recent years as an increasingly important technology

encompassing a wide array of devices and

applications including embedded passive devices,

flexible displays, and sensors. Device performance,

stability, and function critically depend upon charge

transport and material interaction at the interfaces

of disparate materials. We develop and apply

nondestructive measurement methods to characterize

the electronic and interfacial structure of organic

electronics materials with respect to processing

methods, processing variables, and materials

characteristics.

Eric K. Lin and Dean M. DeLongchamp

Organic electronic devices are projected to

revolutionize new types of integrated circuits

through new applications that take advantage of low-cost,

high-volume manufacturing, nontraditional substrates,

and designed functionality. The current state of organic

electronics is slowed by the concurrent development

of multiple material platforms and processes and a lack

of measurement standardization between laboratories.

A critical need exists for new diagnostic probes, tools,

and methods to address these technological challenges.

Organic field effect transistor test structures were

also designed and fabricated onto silicon wafers with

variations in transistor channel length and width. Devices

constructed using organic semiconductors such as

poly(3-hexyl thiophene) (P3HT) were tested for their

electrical characteristics such as the field effect hole

mobility, on/off ratios, and threshold mobilities. Variations

in mobility, for example, are observed with changes in

processing variables such as annealing temperature and

casting solvent. Correlations are found between device

performance and the microstructure of P3HT as quantified

by NEXAFS, optical ellipsometry, and FTIR spectroscopy.

Contributors and Collaborators

J. Obrzut, B. Vogel, C. Chiang, K. Kano, C. Brooks,

N. Fisher, B. Vogt, H. Lee, Y. Jung, W. Wu (Polymers

Division, NIST); S. Sambasivan, D. Fischer (Ceramics

Division, NIST); M. Gurau, L. Richter (Chemical

Science and Technology Laboratory, NIST); C. Richter,

O. Kirillov (Electronics and Electrical Engineering

Laboratory, NIST); R. Crosswell (Motorola);

L. Moro, N. Rutherford (Vitex); A. Murphy,

J.M.J. Frechet, P. Chang, V. Subramanian (University

of California–Berkeley); M. Ling, Z. Bao (Stanford

University); M. Chabinyc, Y. Wu, B. Ong (Xerox)

Figure 1: Schematic of the geometry of near-edge x-ray absorption

fine structure (NEXAFS) spectroscopy for the determination of

the orientation of an oligothiophene organic semiconductor

synthesized by the University of California–Berkeley.

Organic electronics presents different measurement

challenges from those identified for inorganic devices.

We are developing an integrated suite of metrologies to

correlate device performance with the structure, properties,

and chemistry of materials and interfaces. We apply

new measurement methods to provide the data and

insight needed for the rational and directed development

of emerging materials and processes. Studies include

AC measurements of organic semiconductor thin films,

Figure 2: Schematic of an organic field effect transistor (OFET)

and a photo of the NIST OFET test bed fabricated onto silicon.

the influence of surface modification layers on device

performance, and the evaluation of moisture barrier

layers for device encapsulation.

This year, near-edge x-ray absorption fine structure

(NEXAFS) spectroscopy was applied to several classes

of organic electronics materials to investigate the

electronic structure, chemistry, and orientation of

these molecules near a supporting substrate. NEXAFS

spectroscopy was used successfully to quantify the

simultaneous chemical conversion, molecular ordering,

and defect formation of soluble oligothiophene

precursor films for application in organic field effect

transistors. Variations in field-effect hole mobility

with thermal processing were directly correlated to

the orientation and distribution of molecules within

3 nm to 20 nm thick films.

Materials for Electronics

39
Nanoporous Low-k Dielectric Constant Thin Films

NIST provides the semiconductor industry with

unique on-wafer measurements of the physical

and structural properties of nanoporous thin films.

Several complementary experimental techniques are

used to measure the pore and matrix morphology of

candidate materials. The data are used by industry

to select candidate low-k materials. Measurement

methods such as x-ray porosimetry and small

angle x-ray scattering are developed that may be

transferred to industrial laboratories. Methods are

being developed to measure patterned low-k samples

and to assess the extent of structure modification

caused by plasma etch.

Eric K. Lin and Wen-li Wu

Future generations of integrated circuits will require

porous low-k interlayer dielectric materials to

address issues with power consumption, signal

propagation delays, and crosstalk that decrease device

performance. The introduction of nanometer scale

pores into a solid film lowers its effective dielectric

constant. However, increasing porosity adversely

affects other important quantities such as the physical

strength needed to survive chemical mechanical

polishing steps and barrier properties to contaminants

such as water. These effects pose severe challenges

to the integration of porous dielectrics into the

device structure.

There is a need for nondestructive, on-wafer

characterization of nanoporous thin films. Parameters

such as the pore size distribution, wall density, porosity,

film uniformity, elemental composition, coefficient

of thermal expansion, and film density are needed to

evaluate candidate low-k materials. NIST continues

to develop low-k characterization methods using a

combination of complementary measurement methods

including small angle neutron and x-ray scattering

(SANS, SAXS), high-resolution x-ray reflectivity (XR),

x-ray porosimetry (XRP), SANS porosimetry, and ion

scattering. To facilitate the transfer of measurement

expertise, a recommended practice guide for XRP is

available for interested researchers.

In collaboration with industrial and university

partners, we have applied existing methods to new

low-k materials and developed new methods to address

upcoming integration challenges. A materials database

developed in collaboration with SEMATECH is used

extensively by SEMATECH and its member companies

to help select candidate materials and to optimize

integration processing conditions. We address the

effects of the ashing/plasma etch process on the low-k

material during pattern transfer. Often surfaces

exposed to ashing/plasma densify and lose terminal

groups (hydrogen or organic moiety) resulting in an

increased moisture adsorption and thus dielectric

constant. XR measurements enable quantification

of the surface densification or pore collapse in

ashing-treated and/or plasma-treated blanket films.

Figure 1: Four models of the damage layer profile plotted as

scattering length density (SLD) as a function of position within a

line. The matrix has a relative SLD of zero in the above plots.

This year, a new method using SAXS was

developed to investigate the effect of plasma etch on

patterned low-k films. After the plasma etch process,

samples are backfilled with the initial low-k material.

Any densification of the sidewall may be observable by

x-ray scattering from the cross-section of a patterned

nanostructure. This SAXS work was carried out at

Argonne National Laboratory using line gratings of

low-k material. The resulting data can then be

compared with several different scattering models

for the densification of the patterned low-k material

as shown in Figure 1. Distinctions between models

such as these will significantly help semiconductor

manufacturers to accelerate the integration of low-k

materials into next generation devices.

Contributors and Collaborators

H. Lee, C. Soles, R. Jones, H. Ro, D. Liu, B. Vogt

(Polymers Division, NIST); C. Glinka (NIST Center

for Neutron Research); Y. Liu (SEMATECH); Q. Lin,

A. Grill, H. Kim (IBM); J. Quintana, D. Casa (Argonne

National Laboratory); K. Char, D. Yoon (Seoul National

University); J. Watkins (University of Massachusetts)

Materials for Electronics

40
Electrical Methods for Mechanical Testing

The International Technology Roadmap for

Semiconductors calls for solutions to the

near-term challenge (through 2009) of achieving

necessary reliability because “new materials,

structures, and processes create new chip reliability

(electrical, thermal, and mechanical) exposure.

Detecting, testing, modeling and control of failure

mechanisms will be key.” To this end, we develop

test and detection methodologies for mechanical

reliability of dimensionally-constrained materials,

and further materials science understanding of

the observed mechanical behavior.

Robert R. Keller, Nicholas Barbosa III,

Roy H. Geiss, David T. Read, and

Andrew J. Slifka

This year we have consolidated three distinct

projects addressing different aspects of the reliability

of materials for microelectronics into one Division

program. The present focus is on electrical methods

for measuring thermal fatigue lifetime and mechanical

strength of patterned metal films. These methods

are based on the principle of applying Joule heating

to specimens in a controlled manner, by use of

low-frequency, high-current density a.c. electrical

signals. Thermal expansion mismatch between film

and substrate then leads to thermal strains, which can

be used as the basis for mechanical testing.

A key aspect of developing time-varying electrical

methods for mechanical metrology is knowledge of the

temperature of the specimen, with sufficient spatial and

temporal resolutions. Details are provided in the Materials

Reliability Division Technical Highlights section.

model material. Figure 1 depicts an inverse pole figure

(IPF) showing surface normal grain orientations before

and after a.c. stressing. Blue dots represent orientations

prior to stressing, and red dots represent orientations of

severely deformed regions after stressing. Black dots

along IPF edges indicate 10 ° increments. Reorientation

is consistent with a recent analysis of slip asymmetry

in cyclic deformation of bulk fcc crystals, which

showed that for the case of fully reversed loading,

a single crystal reorients such that during the tensile

half-cycle, the loading axis rotates toward the primary

slip direction, [011], and during the compressive

half-cycle, it rotates toward the normal to the primary

slip plane, (1 –1 1). The net result of this ratcheting

action is an ultimate crystal orientation near (113).

Development of methods to electrically

measure strengths of thin films is now underway,

with microtensile testing as a reference throughout.

Yield strength measurement is based on detection of the

onset of plasticity using changes in residual resistance

after accumulated cyclic damage. Ultimate strength

measurement is based on extrapolation of cyclic data

to a single cycle, by use of the Coffin-Manson rule.

Results from our work appeared this year in

two archival journal articles, and we target three

more journal submissions by October 2005; this

series of papers will establish us as the leaders in

this novel approach to mechanical testing of materials

with constrained dimensions. One paper written

with German colleagues (R. Mönig, R.R. Keller,

C.A. Volkert, “Thermal Fatigue Testing of Thin Metal

Films,” Rev. Sci. Instrum. 75, 4997–5004 (2004))

represents the first archival journal publication of this

work and describes in detail the test methodology.

We also completed the final report of our August 2004

workshop on Reliability Issues in Nanomaterials

(R.R. Keller, D.T. Read, and R. Mahajan, Report of

the Workshop on Reliability Issues in Nanomaterials,

NIST-SP, in BERB), which was reviewed by nine

non-NIST plenary speakers; this workshop established

us as being among the recognized leaders in the

broad field of reliability of nanomaterials.

Seven presentations of this work were given at five

conferences in FY05 (MRS, ASME, Characterization

and Metrology for ULSI Technology, GOMACTech,

Mechanics and Materials); two more conference

presentations are planned in October 2005.

Contributors and Collaborators

Y. Cheng (Protiro, Inc.); R. Mönig (MIT); C. Volkert

(Forschungszentrum, Karlsruhe, Germany); B. Sun (Intel)

Figure 1: Inverse pole figure showing surface normal orientations

before and after a. c. stressing of Al-1Si at 12.2 MA/cm2 for

1.4 x 105 temperature cycles.

We have made additional progress in documenting

the damage processes leading to failure during thermal

fatigue of patterned interconnects, using Al-1Si as a

Materials for Electronics

41
Thermochemical Metrology of Interfacial Stabilities

Hetero-interfaces are present in the majority of

electronic materials and affect the operating

characteristics of many devices. For successful

fabrication and optimal performance of advanced

designs, data on the behavior of interfaces during

thermal processing is essential. Efficient

measurement and prediction of the interfacial

thermochemical stabilities of potentially useful

materials combinations require new technology

and new approaches, which are being developed

in our laboratories.

Lawrence P. Cook, Mark Vaudin, and

Martin L. Green

By using thin-film differential scanning calorimeters

(DSCs), it is possible to study materials interactions

on a very fine scale — both in terms of the mass

of the samples involved, as well as the magnitude of

the thermodynamic quantities measured. A further

advantage of the thin-film DSC approach to

thermochemical metrology is that it lends itself to

combinatorial studies, in which compositionally

graded thin films can be deposited over a DSC array.

In this way, interfacial stabilities of various materials

combinations can be rapidly evaluated. Our plan is to

correlate thermochemical data from DSC arrays with

characterization by x-ray microdiffraction, using an area

detector and an automated stage to sample each element

of the array. The products formed during interfacial

reaction will be identified, and these experiments will form

the basis for more detailed examination of the kinetics

of reaction for appropriate materials combinations.

To date, our efforts on thin-film DSC have

concentrated on proof-of-concept using well-known

thermochemical events such as the melting of

Sn (232 oC), the ε/α transition in metallic Co (422 oC),

and the reaction between elemental Si and Ni thin films

(kinetically determined). Studies of the latter two reactions

are still in progress, but our preliminary studies of Sn

melting have been completed. Figure 1 shows a 200 nm

thick layer of Sn deposited on the sample side of a

thin-film DSC sensor. The sample was deposited by

pulsed laser deposition (PLD) through a 60 μm x 100 μm

mask; a range of particle sizes is evident. Figure 2 is an

uncalibrated average of multiple DSC scans from a sample

like that in Figure 1. The melting (endothermic) and

crystallization (exothermic) scans show multiple events,

possibly related to differences in thermal behavior of

different size fractions of the particles. A large thermal

hysteresis between melting and crystallization is evident.

This example suggests that the thin-film DSC is sensitive

to variations in materials properties, in this case probably

influenced by the interfacial tension between the metallic

Sn in the core of the particles and the thin SnO2 skin on

the surface of the particles.

Work has already begun on a second generation

of thin-film DSCs that will be optimized to give true

nanometric sensitivity. This work is being done

in collaboration with the University of Illinois at

Urbana–Champaign. Currently, instrumentation is

being set up to utilize the enhanced sensitivity that

will be achieved through a chip design minimizing

thermal mass. With the newer devices, near-adiabatic

measurements will be possible.

Contributors and Collaborators

R. Cavicchi, C. Montgomery, S. Semancik,

M. Carrier (Process Measurements Division, NIST);

P. Schenck, W. Wong-Ng, J. Blendell (Ceramics

Division, NIST); L. Allen (University of Illinois, Urbana–

Figure 1: PLD-deposited Sn on DSC sensor. Champaign); M. Efremov (University of Wisconsin)

Figure 2: Thin-film DSC of Sn in Figure 1.

Materials for Electronics

42
Combinatorial Metal Selection for Catalytic Growth

of ZnO Semiconductor Nanowires

Semiconductor nanowires (NWs) offer a unique

type of nanoscale building block for creating

next-generation lasers and chemical/biological

sensors. Control of NW dimension and structural

and electronic properties is a major barrier to

device fabrication. To address these issues, we

are developing a strategy for selecting metals for

catalytic growth of zinc-oxide (ZnO) nanowires

using an approach based on phase diagrams and

high-throughput fabrication and analysis.

Albert V. Davydov

Semiconductor NWs show significant promise for

 a wide variety of optoelectronic and electronic

devices including nano-lasers, detectors, and chemical

and biological sensors. To advance commercialization

of such devices, it is necessary to control properties

including size, orientation, and structural and electronic

defects of the fabricated nanostructures.

NWs are often produced using a vapor-liquid-solid

(VLS) approach, in which nanometer size islands of

catalytic metals act as nucleation and growth sites for

semiconductor NW growth. The choice of the metal

catalyst can significantly affect the NW properties. We

are developing a strategy for selecting appropriate catalytic

metals and applying this strategy to VLS growth of ZnO

semiconductor. The selection and screening of catalysts

has been achieved using thermodynamic information

from phase diagrams as well as a high-throughput

(combinatorial) approach recently demonstrated for

metallizations to wide-band-gap semiconductors.[1]

We have examined the role of elemental noble metals

and their alloys on ZnO NW growth and properties.

An experimental library was designed using the ternary

silver-gold-copper phase diagram and included elemental,

binary and ternary compositions as well as two

growth temperatures (850 and 950 oC). The metal

library elements were deposited on a single gallium

nitride/sapphire substrate, which was subsequently

annealed to form isolated metal droplets upon which

the ZnO NWs were grown. The resulting set of

metal islands and ZnO NWs was characterized using

electron microscopy, x-ray diffraction, and optical

spectroscopy. It was found that the ZnO NW growth

was significantly influenced by the nature of the catalytic

metal droplets formed on the substrate. For example,

growth from the Au islands at 850 oC yielded only a thin

ZnO nucleation layer with no NWs, while other metal

compositions, which melt at lower temperatures than

Au, produced a variety of NW shapes, sizes and

orientations at this temperature (Figure 1).

A combinatorial approach also permits rapid

correlation of the optical properties of the nanowires

with the composition of the metal islands from

which they were grown. For example, ZnO NWs

fabricated from the silver islands at 850 oC produced

the sharpest excitonic peak near 3.36 eV on the

cathodoluminescence spectrum (comparable to that

for bulk ZnO single crystal), indicating superior

crystalline structure. In contrast, the spectra were

significantly broader for the NWs grown from the

gold and copper containing islands. A comprehensive

assessment of the correlation of structural and

spectroscopic data for the ZnO NW library is still

underway. These initial results demonstrate the power

of the combined phase diagram/combinatorial approach

for controlling semiconductor NW properties.

1. A.V. Davydov, A. Motayed, W.J. Boettinger,

R.S. Gates, Q.Z. Xue, H.C. Lee, and Y.K. Yoo,

Phys. Stat. Sol.(c), 2(7), 2551.

Contributors and Collaborators

W. Boettinger, D. Josell, C. Handwerker, U. Kattner,

M. Vaudin, I. Levin, L. Robins (MSEL); B. Nikoobakht

(CSTL); N. Sanford (EEEL); A. Motayed (University

of Maryland)

Figure 1: Scanning electron microscope images from the

combinatorial library: (a) ZnO wetting layer grown using gold

catalyst (note the absence of NWs); (b) ZnO NWs grown using

gold-copper alloy catalyst; (c) ZnO NWs grown using silver

catalyst. Growth temperature 850 oC. The scale bar on the top

image is 1 μm.

Materials for Electronics

43
Advanced Processes and Materials for On-Chip Interconnects

As dimensions of copper wiring in on-chip electrical

conductors drop below 100 nm, control of electrical

resistivity has become critical. We have demonstrated

new barriers for seedless deposition processes that

will simplify processing and replace high resistivity

tantalum barriers. We have also demonstrated gold

superfill as an alternative metallization.

Daniel Josell and Thomas P. Moffat

As dimensions of transistors in integrated circuits

 shrink, the dimensions of the metal wires

connecting them shrink as well. With industry

passing through the 90 nm node, electron transport

is reduced and fabrication is increasingly difficult.

Figure 1: Copper superfill in trenches with ruthenium barriers

and no copper seed. (A) Desired copper wetting and superfill.

(B) Poor wetting in the presence of surface oxide. (C) Intriguing

localized deposition in trenches, the origin of which is unknown.

Figure 2: Gold superfill in trenches of three different aspect ratios

after indicated deposition times, showing bottom-up superfill.

Figure 3: The impact of leveling additives on trench superfill

and overfill bump formation. Higher adsorption kinetics k+

leads to reduced overfill bump formation (top), consistent with

experimental observation. Corresponding coverage of

accelerator is shown beneath. Consistent with dimensional requirements

specified in the International Technology Roadmap for

Semiconductors, we have been exploring new barrier

materials that will permit copper electrodeposition without

a copper seed layer. We have explored platinum group

elements and have found several that permit seedless

deposition. As part of this effort, we have explored

in depth the role of oxide removal and underpotential

deposition of copper in determining the wettability of

ruthenium barriers and associated reliability for seedless

copper superfill. This work has demonstrated a process

for “repair” of seeds through removal of surface oxide.

We have also explored novel metallizations.

With the successful demonstration of gold superfill

this year (Figure 2), we have now established processes

for superfill with three metals, our work being the first

to demonstrate superfill with either silver or gold.

Recognizing the significance of leveling additives

in industrial processing, we have now extended our

Curvature Enhanced Accelerator Coverage (CEAC)

mechanism to account for their presence during

superfill. The resulting equations predict reduction

of overfill bump through the use of levelers (Figure 3),

consistent with observation. Experiments are underway

to assess kinetics to permit quantitative comparison

to experiment.

Contributors and Collaborators

C. Witt (Cookson–Enthone); D. Wheeler (University

of Maryland)

Materials for Electronics

44
Pb-free Surface Finishes: Sn Whisker Growth

Soldered joints are increasingly tenuous links in

the assembly of microelectronics as a consequence

of ever shrinking chip and package dimensions,

the broadening use of flip-chip technology, and

the movement toward environmentally friendly

lead-free (Pb-free) solders. To support needs in

this area, the goal of this project is to provide

data and materials measurements of critical

importance to solder interconnect technology

for microelectronics assembly.

Maureen E. Williams and Kil-Won Moon

I

t is well known that the use of pure tin protective

 deposits can lead to problems with whiskers —

filamentary whiskers typically 1 μm diameter and

several mm long which grow from the plating

and cause electrical shorts and failure. Historically,

lead was added to tin plate to prevent whisker

growth as well as lower costs. The present project

focuses on Pb-free, Sn-rich deposits with alloying

additions that could potentially retard whisker

formation. The Sn-Cu system was selected for

compatibility reasons, since Sn-Cu-Ag is likely

to be the Pb-free solder of choice for industrial

applications. The substitution of a different solute

for Pb in the Sn-rich deposit was proposed to also

retard whisker growth. A detailed microstructural

comparison of deposits with high- and low-whiskering

tendency has been conducted, leading to a correlation

of Sn grain size, shape, and residual stress with

whisker growth.

A manuscript submitted to Acta Materialia,

“Hillock and Whisker Formation in Sn, Sn-Cu and

Sn-Pb Electrodeposits,” presents measurements of

compressive stress in the electrodeposits and how

various microstructural features of the deposits affect

whisker growth. Relief of the compressive stress

occurs by uniform creep for Sn-Pb because it has an

equiaxed grain structure. On the other hand, localized

creep in the form of hillocks and whiskers occurs

for Sn and Sn-Cu because both have columnar grain

structures. Compact hillocks form for Sn deposits

because the columnar grain boundaries are mobile.

Contorted hillocks and whiskers form for the Sn-Cu

deposits because the columnar grain boundary

motion is pinned by intermetallic precipitates.

Some reports suggest that restraining and cracking

of a tin oxide surface film are necessary steps in the

nucleation of Sn whiskers. However, results at NIST,

accepted for publication in the Journal of Electronic

Materials showed little support for this mechanism.

 For instance, whiskers were observed on

bright Sn-Cu electrodeposits but not on pure bright

Sn electrodeposits on pyrophosphate Cu substrates.

In order to understand the role of the deposit

surface, the Sn oxide surface film and surface

structures were analyzed by Auger and Electron

Backscatter Diffraction (EBSD). In Auger analysis,

residuals of the Sn oxide surface film were observed

after Ar+ ion cleaning. This feature allowed us to

discriminate the Sn whisker growth with or without

the oxide surface film.

Contributors and Collaborators

W. Boettinger, C. Johnson (Metallurgy Division,

NIST)

Figure 1: Low and high magnification SEM micrographs of the

electrodeposited surface of a 16 μm thick pure Sn layer on a

cantilever beam showing bimodal size distribution of conical

hillocks. Such hillocks form to relieve compressive residual

stress. Whiskers form when grain boundaries in the deposit

are pinned by precipitates.

Materials for Electronics

45
Materials for Advanced Si CMOS

Further size reduction of complementarymetal-oxide-silicon (CMOS) devices in the Si

microelectronics industry, necessary for continued

adherence to Moore’s law, is currently materials

limited. The gate stack, composed of the SiO2

gate dielectric and the doped polycrystalline

Si gate electrode, is no longer sufficient and

must be replaced by new materials. Further, starting

Si wafers must be strain engineered to increase

carrier mobility and subsequent device performance.

NIST plays an active role in both activities.

Martin L. Green

NIST/MSEL is poised to play important roles

in the introduction of new materials to the Si

microelectronics industry, so that further scaling

(size reduction) may be enabled. One example is

the advanced gate stack for Si CMOS. To enable

further device scaling, the capacitive equivalent

thickness (CET) of the gate stack must be 0.5 nm

to 1.0 nm. This will not be achievable with existing

SiO2/polycrystalline Si gate stacks. Since replacements

for SiO2 have already been identified, it is now particularly

important to replace the doped polycrystalline Si gate

electrode with a true metal. Given the large number of

possible choices of alloys for the metal gate electrode,

the combinatorial approach is seen as the most effective

way of identifying alloys possessing the proper work

function and stability as metal gates on HfO2.

Figure 1 shows flatband voltage data, from which

work functions may be derived, measured on hundreds

of capacitors, where each small square represents a

different metal gate composition in the Nb-W-Pt ternary

system. Variations in flatband voltage, due to alloy

composition, are readily observed. As can be seen from

Figure 2, work functions determined through combinatorial

experiments are in excellent agreement with those

determined by other, less straightforward means.

Figure 1: Flatband voltage measurements obtained from

capacitance — voltage data, for the Nb-Pt-W metal gate system.

Figure 2: Comparison of work function data determined through

combinatorial experiments and other techniques.

Figure 3: Raman shift of strained Si with respect to relaxed Si.

Another example of NIST activity in advanced Si

materials is strained Si, which is increasingly being

used to enhance carrier mobilities in high performance

devices. Figure 3 shows the characteristic Raman shift

that accompanies strain in the Si lattice. MSEL/NIST

is working to calibrate the Raman shift to an absolute

strain measurement (via precision lattice parameter

determination) to facilitate the introduction of this

technology.

Contributors and Collaborators

D. Black, K.-S. Chang, T. Chikyow (NIMS,

Japan); M. Gardener (Sematech); D. Josell, R. Lei

(Intel); P. Majhi (Sematech); A. Paul, P. Schenck,

W. Wong-Ng, J. Suehle (EEEL/NIST); I. Takeuchi

(University of Maryland)

Materials for Electronics

46
Metrology and Standards for Electronic and

Optoelectronic Materials

The electronics and optoelectronics industries

require accurate materials properties data to

improve their device fabrication, modeling, and

evaluation processes. Our recent activities have

emphasized optical and structural metrologies

applicable to wide bandgap semiconductor

nanowires, and UV Raman spectroscopy

for the evaluation of strain in strained

silicon-on-insulator structures.

Lawrence H. Robins and Albert J. Paul

Nanowires, defined as semiconductor or metal

structures having a quasi-cylindrical geometry

with diameter in the range 1 to 100 nm, are expected

to have a major impact on future electronic and

optoelectronic technologies. A NIST program was

recently started to develop growth and manipulation

techniques, metrologies, and test structures for

semiconductor nanowires, based on GaN growth

by molecular beam epitaxy (MBE), and ZnO growth by

the catalyst-assisted vapor-liquid-solid (VLS) method.

We are contributing to this program by developing

metrologies for structural and optical characterization

of the nanowire samples and test structures.

in the dark-field image (Figure 1(b)), and also give rise

to streaking in electron diffraction (not shown here).

In contrast, the nanowires appear free of extended

defects in TEM.

Figure 1: Dark-field TEM images of GaN nanowire and matrix

structure grown on AlN/Si. (a) Lower magnification image shows

nanowires and unwanted matrix layer both growing from AlN

buffer. (b) Higher magnification image shows basal-plane defects

in matrix layer.

Figure 2: Low-temperature CL of GaN nanowire sample. Red

curve: as-grown. Blue curve: nanowires only, removed from

matrix layer. Green curve: matrix layer + nanowire “roots,”

with tops of nanowires polished off.

The nanowire structure from Figure 1 was

characterized by low-temperature cathodoluminescence

(CL), as shown in Figure 2. The CL of the nanowires

is dominated by excitons bound to shallow donor

impurities (3.4716 eV peak) while the matrix layer CL

is dominated by excitons bound to structural defects

(peaks “d1” through “d5”) that may be related to the

defects seen by TEM.

Similarly to the GaN samples, the ZnO samples were

found to contain a highly defective “matrix” layer together

with relatively defect-free vertical nanowires, but the

matrix layer in the ZnO was found to consist of horizontally

growing nanowires. The choice of metal catalyst

(Ag, Au, or Cu-containing alloy) for VLS growth of the

ZnO samples was found to have a strong affect on the

CL spectra, ascribed to catalyst doping of the ZnO and

concomitant formation of catalyst-related impurity levels.

Our characterization results on GaN and ZnO nanowires

were reported at the 2005 Electronic Materials Conference

(Santa Barbara, CA, June 22–24).

Contributors and Collaborators

A. Davydov, A. Motayed (Metallurgy Division,

NIST); J. Barker, K. Bertness, N. Sanford (Optoelectronics

Division, NIST); B. Nikoobakht (Surface and

Microanalysis Science Division, NIST); R.Z. Lei

(Intel Corporation); G. Celler, M. Kennard (SOITEC)

TEM structure of one of our first GaN nanowire

samples, grown by MBE on an AlN buffer layer on

Si(111), is shown in Figure 1. The sample contains

both nanowires and a rough, faceted “matrix” layer

(lower half of Figure 1(a)). Growth of most nanowires

appears to initiate at the AlN buffer, rather than within

the matrix layer. The matrix layer contains a high

density of basal-plane defects, which produce striations

Materials for Electronics

47
Nano-Structured Materials for Sensors and

Ultra-High Density Data Storage

Magnetic sensors play a central role in many

important technologies ranging from health care

to homeland security. A common need among

these technologies is greater sensitivity through

nano-structured materials.

In ultra-high density data storage, one of the most

pressing needs is for nano-structured media that

store data at ever-increasing densities. Improved

methods for the magnetic isolation of grains in

ultra-thin films are a key need. We have initiated

research programs in both areas.

William F. Egelhoff, Jr.

Over the past decade, NIST’s Magnetic Engineering

Research Facility (MIRF) has made important and

widely recognized contributions to the thin magnetic films

used as read heads for hard disk drives. MIRF is one of

the most versatile facilities in the world for the fabrication

and analysis of novel magnetic thin films. This versatility

is illustrated by two new areas of research that have

recently been initiated. One is magnetic sensors and the

other is magnetic media. The common link is that both

require nano-structured thin films.

thin-film form. Second, some of the bulk sensitivity

can be recovered by nano-layering the magnetic thin

films with non-magnetic thin films. Third, conventional

thin-films sensor designs contain a design flaw that

allows magnetic irregularities to reduce the potential

sensitivity by over a factor of 100. Fourth, we have

found a way to use nano-structuring of the thin films to

reduce these irregularities sharply and achieve a factor

of 40 improvement in sensitivity. Fifth, an analysis of

the physics of the nano-structuring immediately suggests

that opportunities exist for significant further gains.

In the area of novel magnetic media we have been

collaborating very closely with Seagate. Seagate is the

world’s leading manufacturer of hard-disk drives, and for

the past two years, they have been sending a Ph.D. physicist

from their research labs to work with us, first on ballistic

magnetoresistance, and then on novel magnetic media.

Figure 1: The Magnetic Engineering Research Facility.

We are now 1.5 years into the Magnetic Sensors

Competence Program. We have evaluated a series of

complex magnetic alloys that in bulk form are very

sensitive to small magnetic fields but had not previously

been studied in thin-film form (e.g., Ni77Fe14Mn5Cu4).

Our approach is to carry out the metrology needed to

optimize these materials in thin-film form.

We have made several surprising discoveries.

First, these alloys are uniformly less sensitive in

In recent work, we have found a novel method for

magnetically decoupling grains in CoPd media. CoPd

multilayers are one of the leading candidates for the next

generation of magnetic media. We have found that if

we deposit an Au film on top of the CoPd and anneal the

sample in air, two unexpected phenomena occur as a

result of rapid diffusion of atoms along grain boundaries.

One is that Co atoms diffuse to the surface, react with

oxygen, and remain at the surface. The other is that Au

atoms diffuse into the grain boundaries replacing Co. The

net effect is that the grain boundaries are demagnetized,

and each grain can magnetically switch independently of

its neighbors. This method provides the best magnetic

isolation of grains yet found.

This work has been reported at several conferences

and industrial workshops.

Contributors and Collaborators

E.B. Svedberg, D. Weller (Seagate); R.D. McMichael,

T.P. Moffat, J. Mallett, A.J. Shapiro, J.E. Bonevich

(Metallurgy Division, NIST); D.P. Pappas

(Electromagnetics Division, NIST); M.D. Stiles

(Physics Lab, NIST)

Figure 2: Grains isolated magnetically by Au diffusing into grain

boundaries.

Materials for Electronics

Annealed at 300 °C, 1 hour

48
Program Overview

Advanced Manufacturing Processes

The competitiveness of U.S. manufacturers depends

substantially on their ability to create new product concepts

and to quickly translate such concepts into manufactured

products that meet their customers’ increasing expectations

of performance, cost, and reliability. This is equally true

for well-established “commodity” industries, such as

automotive, aerospace, and electronics; for materials

suppliers of aluminum, steel, and polymers; and for

rapidly growing industries based on nanotechnology

and biotechnology. In support of these industries,

MSEL is developing robust measurement methods,

standards, software, and process and materials data

needed for design, monitoring, and control of new

and existing materials and their manufacturing processes.

The Advanced Manufacturing Processes Program focuses

on the following high-impact areas:

■ Development of combinatorial and high-throughput

methods for developing and characterizing materials

ranging from thin films and nanocomposites to micro

and macroscale materials structures;

■ Automotive industry-targeted R&D for improved

measurement methods for sheet metal forming

of lightweight metals and for the development

of hydrogen storage materials needed for

hydrogen-powered vehicles;

■ Development of innovative, physics-based process

modeling tools for simulating phase transformations

and deformation during manufacturing and creation

of the databases that support such simulations;

■ National traceable standards having a major impact

on trade, such as hardness standards for metals and

MALDI process standards for polymers; and

■ Development of innovative microfluidic testbeds

for process design and characterization of polymer

formulations.

Our research is conducted in close collaboration

with industrial partners, including industrial consortia,

and with national standards organizations. These

collaborations not only ensure the relevance of our

research, but also promote rapid transfer and utilization

of our research by our partners. Three projects from

the Advanced Manufacturing Methods Program are

highlighted below.

NIST Combinatorial Methods Center (NCMC)

The NCMC develops innovative combinatorial and

high-throughput (C&HT) measurement techniques and

experimental strategies for accelerating the discovery

and optimization of complex materials and products,

such as polymer coatings and films, structural plastics,

fuels, personal care goods, and adhesives. These

C&HT array and gradient methods enable the rapid

acquisition and analysis of physical and chemical

data from materials libraries, thereby accelerating

materials discovery, manufacturing design, and

knowledge generation. In 2005, the NCMC

Consortium consisted of 19 institutions from industry,

government laboratories, and academic groups, which

represents a broad cross-section of the chemical and

materials research sectors. A growing component of

the NIST NCMC program is focused on accelerating

the development and understanding of emerging

technologies, including nanostructured materials,

organic electronics, and biomaterials, and, in particular,

on the nanometrology needed for C&HT-based

research for these technologies.

Forming of Lightweight Materials

Automotive manufacturing is a materials intensive

industry that involves approximately 10 % of the U.S.

workforce. In spite of the use of the most advanced,

cost-effective technologies, this globally competitive

industry has major productivity issues related to

materials measurements, materials modeling, and

process design. Chief among these is the difficulty

of designing stamping dies for sheet metal forming.

An ATP-sponsored workshop (“The Road Ahead,”

June 20–22, 2000) identified problems in the production

of working die sets as the main obstacle to reducing

the time between accepting a new design and actual

production of parts. This is also the largest single

cost (besides labor) in car production. Existing finite

element models of deformation and the materials

measurements and data on which they are based are

inadequate to the task of evaluating a die set design:

they do not accurately predict the multi-axial hardening,

springback, and friction of sheet metal during metal

forming processes and, therefore, the stamping dies

designed using finite element analyses must be modified

through physical prototyping to produce the desired

shapes, particularly for high-strength steels and

aluminum alloys. To realize the weight savings and

increased fuel economy enabled by high-strength

steel and aluminum alloys, a whole new level of

formability measurement methods, models, and data

is needed for accurate die design, backed by a better

understanding of the physics behind metal deformation.

The MSEL Metallurgy Division is working with the

U.S. automakers and their suppliers to fill these needs.

A key component of our program is the unique

multi-axial deformation measurement facility with

which local strains in deformed metal sheet can be

measured in situ. This facility has enabled NIST

to take a key role in developing new methods for

49
assessing springback, residual stresses, friction

between the sheet metal and die during forming, and

surface roughening, and in providing benchmark data

for international round-robin experiments for finite

element code. New techniques for detecting local

deformation events at surfaces are providing insights

into the physics of deformation and are leading to

physics-based constitutive equations.

Hardness Standardization:

Rockwell, Vickers, and Knoop

Hardness is the primary test measurement used to

determine and specify the mechanical properties of

metal products and, as such, determines compliance

with customer specifications in the national and

international marketplace. The MSEL Metallurgy

Division is engaged in developing and maintaining

national traceability for hardness measurements and

in assisting U.S. industry in making measurements

compatible with other countries around the world,

enabled through our chairing the ASTM International

Committee on Indentation Hardness Testing and heading

the U.S. delegation to the ISO Committee on Hardness

Testing of Metals, which oversees the development

of the organizations’ respective hardness programs.

Our specific R&D responsibilities include the

standardization of the national hardness scales,

development of primary reference transfer standards,

leadership in national and international standards writing

organizations, and interactions and comparisons with

U.S. laboratories and the National Metrology Institutes

of other countries.

Contact: Frank W. Gayle (Metallurgy Division)

Program Overview

50
Mechanisms for Delivery of Thermodynamic and Kinetic Data

Many commercial processes are controlled by the

thermodynamic and diffusion properties of the

material. The ready availability of reliable data

is a key component to successful design of

new materials and manufacturing processes.

Thermodynamic and diffusion mobility databases

provide an efficient method of storing the wealth

of these data, and software tools allow the user

to efficiently retrieve the needed information.

Ursula R. Kattner and Carelyn E. Campbell

The complexity of thermodynamics and diffusion

kinetics prevented their direct application in the

design of complex materials and processes in the past.

Graphical representation of multicomponent systems is

too complex, and, because of the enormous number,

storage of every single datum is impractical. However,

mathematical functions representing thermodynamic

and diffusion properties of the phases permit efficient

storage. Since these functions are based on physical

models, they further provide the power to extrapolate

binary and ternary systems to higher order systems.

Software then allows calculation of the desired

quantities. This approach is called the CALPHAD

methodology. Unfortunately, previous software was

tailored for expert users and was difficult for the

occasional, less experienced user.

manipulation. Links to a downloadable Mathematica

script for DTA analysis simulation using these output

tables as well as tutorial pages on the interpretation

of phase equilibria information are also found on

the Metallurgy Division Phase Diagram web site

(www.metallurgy.nist.gov/phase/).

Advanced Manufacturing Processes

The databases and software developed in this project

are designed to provide users with simple tools to

retrieve and disseminate information needed for efficient

materials and process design. A web site is being

developed for interactive solidification calculations using

the NIST superalloy and solder thermodynamic

databases (Figure 1). Results are provided in tabular

form and can be used with other software packages,

such as Mathematica or spreadsheets, for further

Multicomponent multiphase diffusion couples can

be simulated using NIST thermodynamic and diffusion

mobility databases, and experimental and calculated

composition profiles can be compared. Figure 2

shows the comparison of calculated and experimental

composition profiles for a γ + γ ́/γ diffusion couple

(IN100/René-88). The high fraction of γ ́ in the

IN100 alloy leads to the observed experimental scatter

on the left-hand side. Efforts to incorporate the

diffusion in ordered phases such as B2 (NiAl) and

γ ́ (Ni3Al) are being pursued. Future work will assess

the diffusion mobilities in the Ni-Al-Cr system for the

B2 and γ ́ phases.

Interactions developed through our “High Throughput

Analysis of Multicomponent Multiphase Diffusion”

workshop series are posted at (www.ctcms.nist.gov).

The NIST Diffusion Data Center is being converted into

an electronic searchable form, and a preliminary version

is now available at <winweb.nist.gov/diffusion>.

Contributors and Collaborators

W.J. Boettinger (Metallurgy Division, NIST);

A.R. Roosen (CTCMS, NIST); J.-C. Zhao (General

Electric)

Figure 2: Experimental and calculated composition profiles for

IN100/René-88 diffusion couple (1150 oC, 1000 h).

Figure 1: Web site for interactive solidification calculations.

51
FiPy: An Adaptable Framework for Phase Field

and Level Set Modeling

Phase field and level set methods have enjoyed

considerable success for phase transformation

modeling. However, any but the simplest

implementations of these methods are beyond the

capabilities of otherwise interested researchers.

An adaptable software tool is being developed to

support these scientists.

Jonathan E. Guyer and Daniel Wheeler

The equations that model the evolution of many

physical, chemical, and biological systems have

a remarkably similar form. Despite the common

mathematical structure of these models and the common

approaches to solving them, most research codes are

developed by individuals for one particular problem

and then abandoned. They tend not to be documented

well enough nor designed well enough to be adapted by

other scientists. In fact, many scientists have difficulty

adapting their own previous codes and opt, instead, to

start from scratch for each new problem.

Another problem with research codes is that

they are often implemented with the solution schemes

that result in a functioning code in the shortest

amount of time. As a result, little advantage is taken

of sophisticated numerical techniques that could allow

dramatically faster solutions, over larger physical

domains, for longer elapsed simulation times.

method of solving PDEs, which is widely employed in

the demanding field of computational fluid dynamics.

The goal of the project has been to encapsulate existing

libraries and tools for tasks such as sparse matrix

solutions and data visualization into a framework that

is approachable by materials scientists. At the same

time, every aspect of the tool is open, allowing any

user to adapt, extend, or improve as they desire.

First released in November 2004, FiPy is already being

used for phase field work by researchers at NIST and

elsewhere. Existing codes have been re-implemented in

FiPy, making them easier to understand and opening them

to a wider battery of solution methods. FiPy has also

enabled prototyping new problems in a matter of hours,

rather than the days or weeks that were previously

required. In addition, FiPy is being applied to new

models of both cell chemotaxis and drug delivery.

Figure 1: Phase field calculations of anisotropic grain growth.

Figure 2: Level set calculations of “superfill.”

Perhaps the greatest success of the tool has been

to allow dissemination of NIST’s Curvature Enhanced

Accelerator Coverage (CEAC) model to researchers

outside of NIST. This model of electrochemical “superfill”

has successfully explained many aspects of the

metallization of microchips, however the FORTRAN-based

level set code to implement the model was impractical

to use by anyone other than its author. Since being

re-implemented in FiPy, the code has already been put

into use by both industrial and academic researchers.

The FiPy implementation of CEAC was highlighted by

John Dukovic of Applied Materials in his Electrochemical

Research Award Address at the 2004 Electrochemical

Society meeting. FiPy can be obtained via the web at

http://www.ctcms.nist.gov/fipy.

Contributors and Collaborators

J. Warren (Metallurgy Division and CTCMS, NIST);

D. Saylor (FDA); W. Losert (University of Maryland);

J. Dukovik (Applied Materials); Y. Shacham-Diamand

(Tel-Aviv University and Waseda University); D. Lewis

(General Electric)

A software framework called FiPy has been jointly

developed in the Metallurgy Division and the Center

for Theoretical and Computational Materials Science

(CTCMS) to address this constant reinvention of phase

transformation codes. FiPy is based on the finite volume

Advanced Manufacturing Processes

52
Metrology Tools to Accelerate Industrial Development

of Solid State Hydrogen Storage Materials

Realization of the “Hydrogen Economy” will require

technological advances in hydrogen production,

storage, and fuel cell implementation. Hydrogen

storage poses the greatest technical challenge,

and solid-state storage of hydrogen in metal

hydrides will eventually be required to alleviate

the safety issues associated with on-board

vehicular storage of high pressure or liquefied

hydrogen. The current state of metal hydride

storage technology falls far short of targets for

vehicular applications. A suite of versatile

measurement tools is needed to accelerate the

development of hydrogen storage materials.

Leonid A. Bendersky, Ursula R. Kattner,

and Martin L. Green

The hydrogen economy has enormous potential to

make the United States less dependent on foreign

sources of energy, as well as create a healthier global

environment. In 2003, the hydrogen-powered

“Freedom Car” was put forth as a grand challenge to

the American people, and funded at the level of $1.2 B.

Of the three enabling technologies necessary for the

realization of this vehicle, i.e., hydrogen production,

storage, and fuel cell implementation, hydrogen storage

is viewed as the biggest obstacle.

On-board storage of high-pressure or liquefied

hydrogen, the most direct approach, has insurmountable

safety issues. In addition, neither liquid hydrogen

(8.4 MJ/L) nor high-pressure (133 MPa) hydrogen

(4.4 MJ/L) meet the fuel energy density specification

of 10 MJ/L established for the Freedom Car. Solid-state

storage of hydrogen in metal hydrides is a safer alternative

for automobiles, as well as for ships, aircraft and

spacecraft. However, the development of solid-state

hydrogen storage materials poses many challenges, and

current materials fall far short of the Freedom Car goals.

Major limitations of metal hydride storage are

as follows: energy density is presently limited to

about 4 MJ/L; desorption behavior (delivery) is not

sufficiently rapid; excessive heat is evolved as a result

of hydrogen adsorption (“filling up”); the fundamental

thermochemistry of hydrides and hydrogen adsorption

and desorption kinetics are a poorly understood

function of composition and microstructure; finally,

reliability of the hydrides, i.e., fatigue and degradation

during reversible hydrogen cycling, is not known.

The goal of this project is the development of new

high-throughput measurement methods to study this

extremely important phase transformation in a wide

variety of metal and intermetallic-based hydrides,

thereby providing tools for industry to develop these

materials at a greatly accelerated pace.

A multidisciplinary approach is used to address

some of the major problems associated with

solid-state hydrogen storage: (i) development of IR

emission spectroscopy and microcalorimetry-based

high-throughput metrologies for measuring hydrogen

adsorption and desorption kinetics, as well as

thermochemical parameters of metal hydrides; and

(ii) development of thermodynamic and kinetic data

underlying this behavior, to guide future development.

Figure 1: Synthesis of combinatorial continuous compositional

spreads.

During the initial phase of this project, combinatorial

film libraries of a metal alloy system have been fabricated

in a form of thin film continuous compositional spreads.

Initial systems include: Fe2Ti-FeTi2, Ni-Mg, and

Zr35Ni65–xVx. The synthesis of the compositional spread

is verified by EDS, x-ray diffraction, and cross-sectional

TEM. The construction of the reaction chamber for the

hydrogenation and IR measurement experiments has been

initiated. Special precautions were made in the design to

address safety issues arising from working with hydrogen

gas at elevated temperatures and pressures.

For the construction of the thermodynamic database,

the available Gibbs energy functions of the alloy systems

and the metal hydride are also being evaluated.

 Contributors and Collaborators

D. Josell (Metallurgy Division, NIST); L.P. Cook

(Ceramics Division, NIST); E.J. Heilweil (Physics Lab,

NIST); S. Semancik (CSTL, NIST)

Advanced Manufacturing Processes

53
Fundamental Nature of Crack Tips in Glass

Lifetimes of glasses and structural ceramics are

determined by the size and severity of mechanical

flaws and defects found in their surfaces.

Understanding the nature of these flaws and how

they respond to the surrounding chemical and

physical environment is of particular importance for

the prediction of component lifetime. This project

has as its objectives the quantification of crack

growth parameters in glasses and ceramics in order

to provide design information to colleagues (NASA,

SSG Inc.) wanting to improve the reliability of real

components. Thus the project provides crack growth

parameters for glasses and ceramics, characterizes

cracks and crack tips in these materials using

advanced detection techniques, and develops

methods of assuring structural reliability.

Sheldon M. Wiederhorn

The static fatigue limit in glasses is important

for predicting the long-term reliability of glass.

The static fatigue limit is the applied stress intensity

factor (load times the square root of crack length)

below which cracks will no longer grow. Some

glasses (soda-lime-silica glass) have a static fatigue

limit; others (silica) do not. The methodology for

assuring structural reliability can depend on which kind

of glass is being considered for an application. Hence,

it is important to characterize the factors that determine

the effectiveness of this limit in controlling fracture.

Using atomic force microscopy, we characterized

crack shape and other features that develop at crack

tips in glass near the static fatigue limit. Both of

these characterizations require measurements at the

nanometer scale. The techniques developed on this

project are proving very promising to explore the

high-stress region at crack tips.

During the past year, we concluded that the fatigue

limit is a consequence of the exchange of alkali ions in

the glass for hydroxyl ions in the external environment.

The ion exchange results in a compressive stress

around the crack tip that retards crack motion when

the load is increased above the fatigue limit. Although

the flanks of the crack are corroded, the corrosion

does not reach the crack tip, which is held closed

by the compressive stresses arising from the ion

exchange process.

Finally, fracture areas taken from opposite sides

of the fracture surface have been shown to match to

an accuracy of 0.3 nm normal to the surface and 5 nm

parallel to the surface. No evidence of cavitation is

observed, which means that the fracture of glass occurs

by a completely brittle process. This observation is

contrary to mechanisms reported for very brittle bulk

metallic glasses, for which cavity formation precedes

the fracture process in the glass.

Figure 1: A comparison of opposing fracture surfaces of

soda-lime-silicate glass, AFM scan. The two surfaces are

scanned separately. The sections of the surface are placed in the

figure in such a way that the highlights in the two figures match.

Note the overlap of the polygons formed by connecting the same

highlight features in each figure. Within experimental scatter, the

two images are identical.

The difference in behavior between silicate glasses

and bulk metallic glasses is probably related to the type

of bond holding the material together. Bonds in silicate

glasses are covalent in nature. These are directional

and resistant to shear. By contrast, bonding in metallic

materials is non directional, which makes them

susceptible to displacements by shear stresses, hence

the ease of cavity formation at the tips of cracks in

bulk metallic glasses.

Publications

Jean-Pierre Guin and Sheldon M. Wiederhorn,

“Fracture of Silicate Glasses: Ductile or Brittle?”

Phys. Rev. Let. 92 [21] 215502 (2004).

Jean-Pierre Guin, Sheldon M. Wiederhorn, and

Theo Fett, “Crack-Tip Structure in Soda-Lime-Silicate

Glass: Experimental Observations,” J. Am. Ceram. Soc.

88 [3] 652–659 (2005).

Contributors and Collaborators

Prof. Tanguy Rouxel (University of Rennes, France);

Prof. Theo Fett (Forschungszentrum, Karlsruhe,

Germany)

Advanced Manufacturing Processes

54
Hardness Standardization: Rockwell, Vickers, Knoop

Hardness is the primary test measurement used to

determine and specify the mechanical properties

of metal products. The Metallurgy Division is

engaged in all levels of standards activities

to assist U.S. industry in making hardness

measurements compatible with other countries

around the world. These activities include the

standardization of the national hardness scales,

development of primary reference transfer

standards, leadership in national and international

standards writing organizations, and interactions

and comparisons with U.S. laboratories and the

National Metrology Institutes of other countries.

Carlos Beauchamp and Sam Low

At the international level, the Metallurgy Division is

 leading the Working Group on Hardness (WGH)

under the International Committee for Weights and

Measures (CIPM), with a goal to standardize hardness

measurements worldwide. As Secretary of the WGH,

we have led an effort this year to better define the

Rockwell hardness test procedure used by National

Metrology Institutes (NMIs). The new definition

is awaiting approval by the CIPM. Other activities

include chairing the ASTM-International Committee

on Indentation Hardness Testing and heading the

U.S. delegation to the ISO Committee on Hardness

Testing of Metals, which oversees the development

of the organizations’ respective hardness programs.

In conjunction with ASTM International and IMEKO,

the Metallurgy Division organized the HARDMEKO

2004 Conference, an international conference for

scientists and specialists involved in the measurement

of hardness (see Figure 1). The conference was very

successful, bringing together an international audience

to hear over 25 technical presentations by experts

from 11 countries.

Our primary task at the national level is to

standardize the U.S. national hardness scales and

to provide a means of transferring these scale values

to industry. Currently, we are producing test block

Standard Reference Materials® (SRMs) for the Rockwell,

Vickers, and Knoop hardness scales, as well as developing

new reference standards. A new microindentation

standardizing machine has been acquired and is currently

undergoing testing and uncertainty analysis. Vickers

and Knoop microindentation SRMs are available at

hardness levels of 125, 600, and 760 kgf/mm2. Additional

hardness levels are being investigated ranging from 900

to 1,400 kgf/mm2. These blocks will significantly extend

the range of microindentation SRMs offered by NIST.

In addition to newly introduced Standard Reference

Materials® (SRMs) for the Rockwell B scale and three

SRM Rockwell C scale blocks currently available,

we are in the process of producing new SRMs for the

HR15 N and HR30 N Rockwell scales. The N scales

are used primarily for measuring thinner gage material

or case depth. Work is also continuing to produce

a new Rockwell hardness diamond indenter SRM.

A joint project with Gilmore Diamond Tools has

recently demonstrated that diamond indenters can

be repeatedly produced with the correct shape and

adhere to the very tight calibration grade tolerances.

Other activities at the national level occurring this

year included the assessment of commercial secondary

hardness calibration laboratories for the NIST National

Voluntary Laboratory Accreditation Program (NVLAP)

and the development of indentation Finite Element

Analysis models used to analyze effects of different

indenter materials for all Rockwell hardness scales

in support of proposed revisions to international

test standards.

Contributors and Collaborators

J. Fink, D. Kelley, L. Ma, H. Gates (Metallurgy

Division, NIST); J. Song (MEL, NIST); W. Liggett, Jr.,

N. Zhang (ITL, NIST); S. Doty, B. Belzer, D. Faison

(NVLAP, NIST); W. Stiefel (TS, NIST); M. Mihalec

(Gilmore Diamond Tools, Providence, RI)

Advanced Manufacturing Processes

Figure 1:

HARDMEKO

2004 Conference

organized by

NIST with ASTM

and IMEKO.

55
NIST Combinatorial Methods Center

Pioneer and Partner in Accelerated Materials Research

Combinatorial and high-throughput (C&HT)

methods hold great potential for making materials

research more productive, more thorough, and less

wasteful. However, significant barriers prevent

the widespread adoption of these revolutionary

techniques. Through creative, cost-effective

measurement solutions, and with an eye towards

fruitful collaboration, the NIST Combinatorial

Methods Center (NCMC) strives to ease the

acquisition of C&HT techniques by the materials

research community.

Michael J. Fasolka

The NIST Combinatorial Methods Center is now in

its fourth year of service to industry, government

laboratories, and academic groups interested in acquiring

C&HT research capabilities for materials research.

In 2005, the NCMC consortium included 19 member

institutions (see table), which represent a broad crosssection of the chemical and materials research sectors.

The NCMC fosters wide-spread adaptation of

C&HT technologies through two complementary efforts.

The first is an extensive research program, centered in

the Multivariant Measurement Methods Group of the NIST

Polymers Division. Our research provides innovative

measurement solutions that serve to accelerate the

discovery and optimization of complex products such

as polymer coatings and films, structural plastics, fuels,

personal care goods and adhesives. Moreover, a growing

component of our program aims to speed the development

and understanding of emerging technologies including

nanostructured materials, nanometrology, organic

electronics, and biomaterials. Several of these research

directions are highlighted elsewhere in this report,

as identified by the NCMC symbol (see top right).

emerging industrial needs for C&HT measurements of

materials systems such as biomaterials and organic

electronics. Accordingly, NCMC-6 included plenary

symposia outlining engineering issues in these advanced

systems, sessions illustrating NIST capabilities in these

areas, and a panel discussion aimed at determining new

measurements that should be pursued.

In addition, on May 2–3 2005, we hosted NCMC-7:

Adhesion and Mechanical Properties II. Central to

this event was a symposium presenting new NCMC

methods for the development and optimization of

adhesives. Highlights included a new gradient peel-test

for the HT assessment of backed adhesives (e.g., tapes),

and approaches for the rapid screening of epoxy

formulations. A variation of our buckling technique to

measure modulus, useful for evaluating soft systems

such as polymer gels, was also described.

Advanced Manufacturing Processes

“As a member of NCMC, I believe that Procter & Gamble has

access to a high-performance work group with expertise in high

throughput and combinatorial techniques. The conferences

have been particularly valuable for networking with NIST

scientists as well as other industrial members of NCMC.”

— M. McDonald (Procter and Gamble)

“The coatings industry has been traditionally perceived to react

slowly to implementing newer and quantifiable measurement

techniques for characterizing structure–property relationships

in paints and films. The [NCMC] has pioneered elegant

approaches that can significantly reduce experimental time

[for] testing coating formulation performance.”

— D. Bhattacharya (Eastman Chemical)

In conjunction with its research program, the

NCMC conducts an outreach effort to disseminate

NIST-developed C&HT methods, assess industry

measurement needs, and form a community to advance

the field. A key component of NCMC outreach is our

series of member workshops. On November 8–9 2004,

we hosted our 6th workshop, NCMC-6: Advanced

Materials Forum. The goal of NCMC-6 was to gauge

“The combinatorial methods program at NIST makes the NCMC

critical to any company’s development of high-throughput

workflows. The import of this effort to industry is clearly

indicated by your center’s number of industrial members.”

— J. Dias (ExxonMobil)

Moreover, this year the NCMC continued community

forming activities by organizing several high-profile

sessions dedicated to C&HT research at national

conferences, including meetings of the American Physical

Society, the American Chemical Society, the Materials

Research Society, and the Adhesion Society.

Contributors and Collaborators

C.M. Stafford, P.M. McGuiggan, K.L. Beers,

A. Karim, E.J. Amis (Polymers Division, NIST)

NCMC Members (*New in FY2005):

Hysitron International

Intel

ICI/National Starch & Chemicals 

L’Oreal*

PPG Industries

Procter & Gamble

Rhodia

Univ. of Southern Mississippi

Veeco/Digital Instruments

Air Force Research Lab

Air Products & Chemicals 

Arkema Inc.

BASF

Bayer Polymers

BP

Dow Chemical Company

Eastman Chemical

ExxonMobil Research

Honeywell International

For more information on the NIST Combinatorial

Methods Center, please visit http://www.nist.gov/combi.

56
Polymer Formulations:

Materials Processing and Characterization on a Chip

We develop high-throughput methods to

advance polymer formulations science through

the fabrication of microscale instrumentation

for measuring physical properties of complex

mixtures. Adaptation of microfluidic technology

to polymer fluid processing and measurements

provides an inexpensive, versatile alternative

to the existing paradigm of combinatorial

methods. We have built a platform of polymer

formulations-related functions based on

modified microfluidic device fabrication

methods established in our facilities.

Kathryn L. Beers

Microfluidic device fabrication methods previously

developed in the Polymers Divison enable

combinatorial fabrication and characterization of

polymer libraries. Recent accomplishments include

the integration of multiple functions on a chip for the

formulation, mixing, processing, and characterization

of polymer particles for evaluation of dental composite

materials and the fabrication of gradient polymer

brush surfaces for measuring the behavior of

stimuli-responsive surfaces.

with shrinkage. The first publication on this work

(Langmuir 21, 3629, 2005) was recently profiled in

the Research Highlights of Lab on a Chip.

Advanced Manufacturing Processes

Figure 1: (a) A thiolene microfluidic device used to create,

mix, polymerize and characterize monomer droplets.

(b) Optical images of monomer droplets and polymer particles.

(c) Raman spectra of monomer (red) and polymer (black).

Figure 2: (a) Schematic of amphiphilic block copolymer brush

gradients representing the proposed conformation shift in response

to good and poor solvents for the top block layer. (b) Water contact

angle measurements as a function of top block thickness on three

gradients of top block thickness on uniform bottom blocks of three

different lengths (blue – 4 nm, red – 10 nm, green – 14 nm) in good

(open) and poor (filled) solvents for the top block.

Building on our ability to form organic-phase

droplets in thiolene-based microfluidic devices

(Figure 1a), we can establish libraries of droplets

with systematic composition variations. The droplets

are subject to various processes such as mixing and

photopolymerization on the chip. Raman spectroscopy

on the chip (Figure 1c) and optical imaging (Figure 1b)

are used to measure and correlate properties such as

monomer composition and conversion to polymer

Microchannel confined surface initiated polymerization

was used to prepare surfaces with gradients of molecular

weight and block and statistical copolymer composition.

The block copolymer surfaces were studied for their ability

to reorganize at the air/solution interface depending

on the nature of the polymer and solvent (Figure 2a).

The ability of the surface layer to rearrange was shown

to depend on the thickness of both the top and bottom

block layers (Figure 2b).

The capabilities for controlled radical polymerization

on a chip (CRP Chip) were also extended this year to

include block copolymer synthesis and higher-order

control of solution compositions. A three-input device

was developed, enabling stoichiometric variations in

reactions and faster measurement of kinetic behavior

(Macromol. Rapid Commun. 26, 1037, 2005).

Contributors and Collaborators

Z.T. Cygan, C. Xu, S. Barnes, T. Wu, A.J. Bur,

J.T. Cabral, S.D. Hudson, A.I. Norman, J. Pathak,

W. Zhang, M.J. Fasolka, E.J. Amis (Polymers Division,

NIST)

57
Matrix-assisted laser desorption ionization

time-of-flight mass spectrometry (MALDI-TOF-MS)

is being developed as a method for absolute

molecular mass distribution measurement of

synthetic polymers. This means determining a

comprehensive uncertainty budget for a complex

measurement technique that must include both

Type A (“random”) and Type B (“systematic”)

uncertainties.

William E. Wallace

I

n mass spectrometry, methods exist to calibrate

 the mass axis with high precision and accuracy.

In contrast, the ion-intensity axis is extremely difficult

to calibrate. This leads to large uncertainties in

quantifying the content of mixtures. This is even true

when the mixture is composed solely of different mass

oligomers of the same chemical species as in the case

of polymer polydispersity. The aim of this project is

to calibrate the ion intensity axis. This task has

been divided into three parts: sample preparation/ion

production, instrument optimization/ion separation,

and data analysis/peak integration. Each part is

necessary but on its own is not sufficient to

guarantee quantitation.

We study the MALDI ion-creation process

phenomenologically using combinatorial libraries.

The ratio of analyte to matrix is varied along a linear

path laid down by nebulizing a continuously varying

mixture of two solutions, one analyte+ matrix+ salt

and the other matrix+ salt. In our case, the analyte is

a mixture of two polymers having different end groups

and closely matched molecular mass distributions.

The figure on this page shows such a library

where the blue arrows indicate a linearly changing

analyte:matrix ratio.

To this, we add stochastic-gradient numerical

optimization to adjust the instrument parameters at

each composition to give a mass spectrum that best

matches the known polymerA:polymerB ratio in the

analyte. Instrument parameters optimized include

laser energy, ion extraction voltage, ion lens

voltage, extraction delay time, and detector voltage.

Stochastic methods must be used because the data

has some measure of Type A random uncertainty

(i.e., “noise”) to it; therefore, exact values of the

function to be optimized are not available.

Finally, to this we add our MassSpectator software

which ensures unbiased, logically-consistent integration

of the peaks in the (noisy) mass spectrum. A software

script has been written around MassSpectator that

automatically identifies oligomeric series in the mass

spectrum and calculates the total amount and the

molecular mass moments for each series identified.

Advanced Manufacturing Processes

Quantitative Polymer Mass Spectrometry

An early embodiment of our approach can be

found in ASTM Standard Test Method D7134, the

first MALDI-TOF-MS method endorsed by ASTM.

Working through the Versailles Project on Advanced

Materials and Standards (VAMAS), and in close

cooperation with our industry and national metrology

institute (NMI) colleagues from around the world, an

interlaboratory comparison was initiated to understand

the nexus of critical measurement factors when

performing quantitative polymer mass spectrometry.

From the knowledge gained by the interlaboratory

comparison, D7134 was written with particular

attention paid toward controlling the critical factors.

The MALDI project maintains a vigorous,

worldwide outreach program including an online

polymer MALDI recipes catalog, annual polymer MS

workshops, and the availability of our MassSpectator

software on the web. For more information on

any of these topics please visit our web page at:

www.nist.gov/maldi.

Contributors and Collaborators

W.R. Blair, K.M. Flynn, C.M. Guttman (Polymers

Division, NIST); A.J. Kearsley (Mathematical &

Computational Sciences Division, NIST)

58
Standard Tests and Data for Sheet Metal Formability

rolling directions of the sheet. These data will be

used by industry to eliminate several assumptions that

extrapolate estimated biaxial flow behavior based on

a series of uniaxial tensile tests. This should lead to

more accurate designs and cost savings.

This year, NIST was asked to generate materials

property data for simulations of prototype parts as part

of the NUMISHEET 2005 conference. In addition,

the NUMISHEET 2005 benchmark tests are adding

a new level of complexity by requiring modelers to

predict stresses at specific sample positions during

a benchmark forming process. NIST provided the

corresponding measurements using our unique

capabilities described above. This work also

will be the subject of a plenary presentation at

NUMISHEET 2005.

In order to meet goals for fuel efficiency, the

U.S. automotive industry is moving to lighter,

high-strength materials for auto bodies. NIST has

surveyed the industry and found that accurate

material properties and methods for die designers

to incorporate them into finite element models of

sheet-metal forming dies, is a critical need for the

U.S. auto industry. This project seeks to develop

new standard tests and metrology to accurately

determine sheet metal mechanical response under

forming conditions.

Timothy J. Foecke and Mark Iadicola

Successful introduction of new high-performance

 alloys into automotive production requires

comprehensive data on alloy behavior under realistic

forming conditions. Existing tests are inadequate.

This project is developing two sheet metal formability

tests, along with associated metrology, that can be

standardized and used by industry.

Work on the first formability test, the springback

cup, was undertaken at the direct request of industrial

representatives in the United States Council for

Automotive Research (USCAR). Springback is the

shape change that occurs during elastic relaxation of

the residual stresses that develop during the stamping

process. Accurate springback predictions would

greatly decrease the cost and number of iterations

required for producing stamping dies.

The proposed test for springback consists of

splitting open a ring cut from the sidewall of a deep

drawn cup. The springback cup test was submitted

to ASTM, and a subgroup has been formed to seek its

standardization. In addition, an alternative springback

standard based on stretch flanging over a cylindrical

mandrel, developed by Kuwabara of Japan, has been

submitted to ISO, with NIST staff developing the

ASTM commentary on shortcomings of the standard

geometry and procedures.

The second test method under development uses

unique X-ray system that allows the direct, in situ

measurement of stress in a given direction while the

sample is under multiaxial load. This year we have

made significant progress in mapping the multiaxial

stress-strain surface for DQSK steel, an industry

workhorse alloy, as well as high-strength steels such

as HSLA and DP600. As with the aluminum alloys

studied last year, both the flow stress and the hardening

exponent were found to differ in the transverse and

Advanced Manufacturing Processes

Figure 1: NUMISHEET benchmark sample loaded for plane

strain deformation.

Plans for the upcoming year involve completing

measurement of the multiaxial stress–strain surfaces

for several alloys. This project will determine how the

flow surface evolves with different types and amounts

of multiaxial prestrain in a collaboration with modelers

at GM. In addition, studies to date show that the

influence of plastic strain on the elastic modulus of

the material appears to be significant, and we intend to

quantify the affect of plastic strain state and magnitude

on the effective x-ray elastic constants of aluminum

and alloy steel sheet.

Contributors and Collaborators

R.F. Fields; T. Gnaupel–Herold (NIST Center for

Neutron Research); M. Shi (USS); E. Chu (ALCOA);

C. Xia (Ford); T. Stoughton, M. Wenner, C.T. Wang

(GM); J. Siekirk (DaimlerChrysler)

59
Existing data, measurements methods, and basic

understanding of metallurgical factors that

influence friction, tearing, and surface finish

during sheet metal fabrication are insufficient to

meet the predictive modeling requirements of the

automotive industry. This project addresses the

measurement and data needs through evaluation

of the microstructural origins of the distribution of

slip, surface roughening, and strain localization

during plastic straining. These studies focus on

the relationships between initial material

characteristics and deformation behavior of

aluminum and iron base sheet. New protocols

have resulted that incorporate high-resolution

confocal microscopy imaging to assess the

roughening character over an entire field of view.

Mark R. Stoudt and Stephen W. Banovic

Lightweight materials, such as high-strength steels

 and aluminum alloys, are designed to reduce vehicle

weight and increase fuel economy. The widespread use

of these new alloys in automotive components is limited,

however, by insufficient property data and constitutive

laws required for accurate numeric predictions of the

mechanical behavior and friction during metal forming

processes. One approach to meeting these critical data

needs is a careful examination of the structure property

relationships that directly influence formability.

The inability to reliably predict the deformed surface

morphology with numeric methods raises serious questions

as to how well the analytical tools employed to interpret

roughness data actually represent the real surface.

The underlying principles used to interpret surface

roughness measurements were examined to ascertain the

magnitude and source of any inconsistencies. The study

assessed the variability within the surface roughness

data that occurs over a surface by acquiring multiple

roughness profiles from regularly spaced locations on

an image (Figure 1) and establishing the actual form of

the data with a set of mathematically rigorous protocols.

Most roughness analyses tacitly assume that a

measured profile is completely described by ideal

Gaussian statistics. However, the deviations observed

in the skew and kurtosis data in this study revealed

that roughness profiles taken from plastically deformed

surfaces do not exhibit an ideal Gaussian form.

The significance of this conclusion is twofold:

first, non-Gaussian behavior means the roughness is

produced by a small number of active mechanisms.

This agrees with the literature in that deformation-induced

surface roughness is primarily crystallographic slip

Microstructural Origins of Surface Roughening

and Strain Localizations

and near grain boundary deformation. Second, these

deviations from ideal Gaussian behavior provide direct

evidence that the roughening behavior of a polycrystalline

material cannot be accurately characterized with any

parameter that presumes an ideal Gaussian form

(i.e., mean(Ra) or rms(Rq)). These parameters also

compress the complex surface information within a profile

into a singular expression that can be quite coarse with

respect to the length scale of the surface features.

Advanced Manufacturing Processes

Figure 1: Scanning laser confocal image of the surface produced

by 12 % uniaxial strain in AA6022. The dashed lines indicate the

general locations where surface roughness data were acquired.

Since surface roughness evaluations are highly

dependent upon the statistical methods used in the

analysis, small deviations from the ideal condition, such

as those produced by plastic deformation, are likely to

have pronounced influences on the accuracy of the

analytical methods used to interpret the roughness data.

Hence, the current practice of extrapolating averaged,

compressed values into representations of an entire

surface in a particular strain condition introduces

substantial measurement error into numeric predictions

of behavior. Expressions are being developed to more

accurately represent the stochastic nature of variations

in surface roughness.

Contributors and Collaborators

J.B. Hubbard, R.E. Ricker, L.E. Levine (Metallurgy

Division, NIST); S.A. Janet (ITL, NIST); R. Reno,

E. Moore (UMBC); J.T. Liu (ALCOA)

60
Underlying Processes of Plastic Deformation in Metal Alloys

A substantial increase in the use of aluminum alloys

and high-strength steels in automobiles would greatly

increase fuel efficiency. The primary reason why

this has not yet occurred is a lack of accurate

deformation models for use in designing the stamping

dies. This project is developing a physics-based

model of plastic deformation using a combination

of statistical physics approaches, atomistic modeling,

and advanced measurement techniques.

Lyle E. Levine

Plastic deformation of metals (as in cold rolling,

stamping, drawing, and metal fatigue) is a topic

of great importance to industries worldwide, and

improvements in the basic technology would have a

significant impact on our economy. Unfortunately,

existing constitutive equations cannot accurately predict

the material behavior, and many tryout and redesign

steps are required. Another related difficulty is in

the design of new alloys with improved formability

characteristics. Currently, alloy design is done

empirically with little understanding of how the

various constituents affect the mechanical properties.

In the current work, we have developed a theoretical

framework called the segment length distribution (SLD)

model for fcc single crystals that describes how

macroscopic deformation arises from the statistical

behavior of large numbers of dislocations. Although work

on the SLD model is continuing, the primary emphasis

over the past year has been on validation testing with

Washington State University and new experimental

measurements of the distribution of stresses within

dislocation cells (with the University of Southern California

and Oak Ridge National Laboratory). These stresses

could affect the assumptions used in the SLD model.

Single crystal aluminum tensile specimens are

being produced at NIST for the validation tests. These

specimens are then strained, in situ, in ultra-high vacuum.

A pulsed ultra-violet laser produces photostimulated

electron (PSE) emission from fresh (unoxidized) Al in

the slip lines/bands, and the electrons are collected by

an electron multiplier. These time-resolved studies allow

us to measure the time dependence of slip line/band

production and compare these results to SLD model

predictions. The SLD model predicts intermittent slip

events under some conditions. Figure 1 shows preliminary

PSE results that are consistent with these predictions.

Figure 1: PSE data from Al single crystals.

Figure 2: 117 reflection from deformed Cu crystal.

Preliminary measurements of residual stresses in

plastically deformed Cu single crystals were carried

out using X-ray micro-beams at the Advanced Photon

Source, Argonne National Laboratory. Spatial resolution

(in all three dimensions) is approximately 0.5 μm.

Large fluctuations in elastic strain (and thus stress)

were observed over length scales consistent with

dislocation cells. Figure 2 shows an integrated energy

scan of a 117 reflection from a Cu single crystal

deformed 24 % in compression. The localized and

diffuse features originate primarily from dislocation

cells and cell walls, respectively.

Finally, NIST researchers served on the executive

committee of Dislocations 2004, and were co-organizers

of Fall 2004 MRS and Plasticity 2005 symposia.

Contributors and Collaborators

F. Tavazza (Metallurgy Division, NIST);

A. Chaka (Physical and Chemical Properties Division);

T. Dickinson, S. Langford, M. Cai (Washington State

University); M. Delos-Reyes, Z. Gao, M. Kassner

(University of Southern California); B. Larson,

W. Yang (Oak Ridge National Laboratory)

Advanced Manufacturing Processes

61
Evaluation of Friction Behavior During Metal Forming

Unpredictable friction resulting from

inhomogeneous surface deformation is a significant

obstacle to the widespread introduction of new

high-strength alloys in the automotive industry.

Metal-forming computer models still rely heavily on

empirical friction data. Most existing approaches

are unable to address the strong influences that

variations in metallurgical condition have on the

dynamic material properties and on the evolution

of surface roughness. This project addresses the

need for improved friction measurements, data, and

models, which will allow the auto industry to improve

die design and processes for forming lightweight,

high-strength sheet metal alloys.

Mark R. Stoudt

Many new alloys intended to decrease automobile

weight are sensitive to variations in processing

conditions. This variability causes inconsistencies in

predicted friction behavior that exacerbate the forming

difficulties. Traditional measurements normally focus on

friction mechanics and do not account for the strong

influences that dynamic loading and variations in

metallurgical conditions have on the material properties.

Hence, the friction values selected for a finite element

analysis (FEA) simulation may not fully reflect the actual

metal behavior under those particular conditions. Since

one measurement cannot provide all essential data, new

approaches are needed that: (a) evaluate both static and

dynamic properties, and (b) improve the understanding

of the relationships between friction and microstructural

variations that affect properties during metal forming.

A single-pull measurement protocol (shown

schematically in Figure 1) that produces friction data

under a wide range of carefully controlled loading and

strain conditions to help meet this critical need is under

development. The principal advantage of this technique

is that it enables direct assessment of the influences

of metallurgical variables (i.e., grain size, orientation

effects, strengthening mechanisms, slip homogeneity)

as well as microstructural changes that are produced

during deformation. This new information is anticipated

to guide the development of improved numeric models

that predict the final shape of formed parts.

Figure 1: Schematic diagram of the prototype friction apparatus.

The suitability of this approach was established

through a series of friction experiments conducted

on hot-dipped draw quality semi-killed (DQSK) steel.

The data in Figure 2 demonstrate that the prototype

can easily distinguish the transition from the static to

the sliding state and that the magnitude of the friction

coefficient can be determined in real time at any point

during the test. In addition, the measurement sensitivity

of the apparatus is such that the quality of the resulting

data is amenable to detailed statistical analysis.

Results to date indicate that the measurement

protocol is appropriate for further development.

A matrix of experiments is planned to further evaluate

the influences of initial surface roughness and asperity

distribution, strain rates and surface lubricants.

Contributors and Collaborators

S.P. Mates, J.B. Hubbard, D.J. Pitchure, R.E. Ricker,

L.E. Levine (Metallurgy Division, NIST); G.B. Dalton,

(TribSys, Inc.); D.E. Green (University of Windsor)

Figure 2: Variation in friction coefficient as a function of time for

lubricated DQSK steel under a 1250 N indentation force.

Advanced Manufacturing Processes

62
Biomaterials

Rapid development of medical technologies

depends on the availability of adequate methods to

characterize, standardize, control, and mass produce

them. To realize this goal, a measurement infrastructure

is needed to bridge the gap between the exponentially

increasing basic biomedical knowledge and clinical

applications. The MSEL Biomaterials Program is a

collaborative effort creating a new generation of

performance standards and predictive tools targeting

the metrology chain for biomedical research.

Today, all areas of materials science confront real

systems and processes. In the biomaterials arena,

we can no longer advance science by simply studying

ideal model systems. We must comprehend complex

realistic systems in terms of their structure, function,

and dynamics over the size range from nanometers to

millimeters. MSEL is uniquely positioned to make a

major contribution to the development of measurement

infrastructure through three focus areas: Systems

Biology, Bioimaging, and Nanobiosensing.

Systems Biology

MSEL research in systems biology focuses on

quantifying relationships of systems at the cell, tissue,

and organ level. To meet this need, we are developing

libraries of reference materials, high-throughput

techniques for screening libraries, and informatics

approaches for data analysis and interpretation.

Physicochemical and biochemical components are

organized using patterning, phase separating, and

self-assembling processes. Physicochemical

components of interest include modulus and surface

topography; biochemical components of interest

include peptide moieties that interact specifically

with cell receptors.

Gradient libraries of tyrosine derivatized

polycarbonate blends and fibronectin/poly(hydroethylmethacrylate) gradients were developed as reference

materials for biomaterial research, such that cell

responses included changes in geometry, distribution,

and proliferation, to assess intercellular communication

among osteoblast and fibroblast cells. Complementing

these surface studies, we are developing metrologies

to establish the relationship between 3D scaffold

morphology (i.e., porosity and permeability) and

cell response. Studies focused on identifying the

relationship between applied macroscopic stresses

and local stresses at the cellular level is also underway,

which will provide valuable input into development

of finite-element models.

Experiments on the mechanical stimulation

of tissues and tissue engineered constructs were

conducted to understand the role of metrology

in diagnostic testing of healthy or disease states.

Stress–strain relationships were defined for vascular

smooth muscle cells and bovine cardiac tissues.

Specialized bioreactors coupled to ultrasound and

infra-red spectroscopy were successful in differentiating

response among the systems. We have demonstrated

that the structure–property relations in healthy tissue

of pulmonary arteries, and in tissue that has remodeled

in response to the onset of disease, can be assessed

using mechanical testing, quantitative ultrasonic

characterization, and histology.

Bioimaging

Advances were made in developing and optimizing

physical methods and informatics tools to enhance

bioimaging and visualization technologies at multiple

length scales. With the reduction of background

noise, images were obtained using broadband coherent

anti-stokes Raman scattering microscopy with a 10-fold

increase in signal, and proteins on the surface of polymer

blends were differentiated. Optical techniques like OCM

and CFM, with spatial resolutions of ≈1 μm, were

employed to image dynamic cell culture experiments

in-situ in a bioreactor. Other advances in computational

modeling of single cell forces and cell populations were

carried out to predict normal ossification patterns and

cartilage formation. By combining information from

different techniques on the same sample and visualizing

structure using interactive, immersive visualization

techniques, scientists will gain new insights into the

physics and materials science of complex systems.

Nanobiosensing

Research in this focus area concentrates on the

development of techniques to measure and manipulate

biological atoms, molecules, and macromolecules at

the nanoscale level (1–100 nm). Mechanical tools

including an optical trap and bioMEMS devices that

can be integrated with currently used biological

techniques for evaluating and measuring cellular

response (i.e., gene expression, cell morphology,

area of adhesion) were developed. Additional studies

focus on identifying mechanical forces that indicate

the onset of osteogenesis and angiogenesis.

Contact: Lori A. Henderson (Polymers Division)

Program Overview

63
Combinatorial Methods for Rapid Characterization

of Cell-Surface Interactions

The increasingly complex nature of functional

biomaterials demands a multidisciplinary

approach to identify and develop strategies

to both characterize and control cell-material

interactions. A robust framework outlining the

interactions governing biomaterial performance

does not exist but is desperately needed. This

project provides the basis for this framework

by focusing on fabrication of single and

multi-variable continuous combinatorial libraries

to rapidly identify compositions and physical

properties exhibiting favorable cell-material

interactions.

Matthew L. Becker and Lori A. Henderson

Developmental biology and tissue engineering are

avenues of research that must be fully integrated

to realize the opportunities in regenerative medicine.

For example, while the interactions between cell and

extracellular matrix have been studied extensively, much

less is understood regarding the influence of synthetic

materials. There is little doubt that having good control of

surface morphology as well as advanced high-throughput

(HT) metrologies for analyzing cell-surface interactions

are needed for biological interpretations, and while

chemical and topographical manipulations of surfaces

have been established, HT methods to evaluate

biological responses to these manipulations have not.

For these reasons, we are developing metrologies and

HT platforms to rapidly analyze physicochemical,

mechanical, and material properties of biomaterials.

We provide examples of two of our sample fabrication

methods, distinct from traditional self-assembled

monolayer approaches, that are being used to design,

manipulate, and quantify cell-surface interactions.

Two functional polymer surfaces, phase separated

tyrosine-derived polycarbonate blends (DTR-PC) and

conformational-based poly(2-hydroxyethyl methacrylate)

brushes [poly(HEMA)], were analyzed using combinatorial

methodologies. The DTR-PC films, consisting of

homopolymer and discrete composition blends of

tyrosine-derived polycarbonates, were shown to have

compositionally dependent gene expression profiles with

the blends differing significantly from the respective

homopolymers. Figure 1 illustrates the effect that polymer

blending has on cell spreading; the extension and distortion

of the lamellapodia increase and the cells appear to spread

less in the blend samples with increasing DTO content.

The surface properties from these discrete films will be

used to establish correlations and limitations for comparing

measurements from discrete samples and single and

multi-variable continuous gradient substrates.

Figure 1: AFM micrographs of the tyrosine-derived polycarbonate

homopolymers and discrete blends show compositionally dependent

phase separation, which is reflected in the immuno-fluorescent

staining for actin (red, cell spreading) and vinculin (green, focal

adhesion contacts) on MC3T3-E1 osteoblasts.

Figure 2: Schematic representation of the poly(HEMA)-FN

gradient and Fibroblast cell distribution.

Poly(HEMA) gradients were prepared to study

molecular interactions and cell conformation on

fibronectin (FN) coated poly(HEMA) by combining

“controlled” free radical polymerization with gradient

preparation technology. This gradient covers

“mushroom” to “brush” regimes in order to determine

how grafting density influences protein adsorption and

cellular response as shown in Figure 2. The number

of cells, their shape, and size were thus correlated to

the density of fibronectin across the gradient.

In summary, the tools developed in this program

will enable the design of material libraries to be used

to probe the behaviors of cells.

Contributors and Collaborators

N.D. Gallant, L.O. Bailey, C. Simon, Jr., T.W. Kee,

Y. Mei, J.S. Stephens, E.J. Amis (Polymers Division,

NIST); K. Langenbach, J.T. Elliot (Biotechnology

Division, NIST); J. Kohn, A. Rege, J. Schutt (Rutgers

University & The New Jersey Center for Biomaterials)

Biomaterials

64
Cellular Level Measurements

Another tool uses Bio-MEMS for cell pulling and

adhesion. Both adhesion and the mechanical response

of a cell to varying mechanical environments are

fundamental to understanding cell motility and

numerous disease mechanisms. A device has been

designed and built that has a transparent platform on

which a single cell can adhere. The focal adhesions

of the cell can be viewed using reflection interference

microscopy or appropriate staining. The platform is

split so that the cell can be strained from one side and

forces measured on the other by way of thin cantilever

beams (see Figure 1). Image analysis can yield strain

and also the cross-sectional size of the cell so that

stress can be determined using the force information.

Therefore, force- or stress-strain response of a single

cell can be done in addition to force as a function of

adhesion area. The device and instrumentation can

also be operated in a cyclic mode, which can be used

to determine the change in mechanical response of

the cell as a function of cyclic fatigue. The design

of this device and results on vascular smooth muscle

cells will be presented at the Biomedical Engineering

Society Annual Fall Meeting in Baltimore, Maryland

in September.

Another tool under development is a Bio-MEMS

device for quartz-crystal microbalance (QCM)-type

measurements. The QCM is used extensively in the

medical research field for characterizing antibody

systems. It is a macroscale device with high sensitivity

due to its oscillating nature. We believe that a

Bio-MEMS device that works similarly could yield a

thousand-fold increase in sensitivity and have as wide

application as the QCM. We have made measurements

on a model antibody system as a baseline and have

designed and built a Bio-MEMS device that mimics

the QCM. We have developed a model of the device

response in order to optimize future designs for

particular applications. A manuscript on the device

design and model has been written for the Journal of

Applied Physics. We are pursuing simple methods

for electrical measurement of the change in oscillator

response, which is the heart of the QCM measurement

technique.

Contributors and Collaborators

V.M. Aponte, E.S. Drexler, D.S. Finch, D. Lauria,

C.N. McCowan, H. Panchawaugh, R.A.L. Rorrer,

D.B. Serrell, R.P. Vinci (Materials Reliability Division,

NIST)

Techniques and tools that facilitate the exposure

of single cells (and arrays) to controlled

mechanical environments and quantification

of mechanical forces, and at the same time allow

for the characterization of other biological

phenomena, are needed for the study of tissues

and cells. The development and evaluation of

one of these tools, a Bio-MEMS cell puller,

is the focus of this year’s effort.

Andrew J. Slifka

Research on the mechanical response of biological

materials at the cellular and sub-cellular levels is

being done with the development of a number of tools.

Optical trapping for cellular mechanics and small-force

materials science is one. We use an optical trap with

a scanned laser to trap multiple dielectric spheres.

These spheres can be attached to a cell. We plan

to use four balls to perform a biaxial mechanical

measurement of a single cell. We are developing data

analysis routines to allow measurement of transient

mechanical response. The optical trap is also being

used to study attractive forces by measuring those

forces required to pull apart two-dimensional islands

of self-assembling nanoparticles.

Figure 1: Detail of the cell platform of the Bio-MEMS device

used for mechanical and adhesion measurements, showing a cell

being stretched.

Biomaterials

65
Biomaterials

Cell Response to Tissue Scaffold Morphology

Industrial and regulatory sectors have expressed

a need for standards and new metrologies relating

to properties of tissue scaffolds for regenerative

medicine. We seek to meet these needs in several

areas where the criteria are clear, and to help

clarify industrial and regulatory needs in other

areas where such clarification is required. We are

developing a reference scaffold for porosity and

permeability. Also, we are developing metrologies

for establishing the relationship between scaffold

porosity/morphology and cell response, for

assessing the ability of a tissue scaffold to safely

host cytokine, and for quantifying mechanical

stimulation requirements for cells — at the cellular

level — from macroscopic inputs.

Marcus T. Cicerone

I

n the field of regenerative medicine, one seeks to

 guide cell differentiation and proliferation, and

production of the extracellular matrix through functional

properties of 3D tissue scaffolds. Developing the ability

to guide such cell behaviors requires first the ability to

characterize and assess properties of tissue scaffolds

as they relate to cell response. This, in turn, requires

well-defined physical and biological systems for which

quantitative rules can be formulated and verified.

We are developing methods for quantitatively

characterizing tissue scaffolds and the cellular

responses they elicit. There are three classes of

scaffold properties that we focus on relative to their

impact on cell behavior; these are: (i) morphological/

topological properties, (ii) mechanical properties, and

(iii) ability of biodegradable scaffold materials to act

as biopreservents in connection with hosting growth

factors and other cytokines.

We led a worldwide collaboration under ASTM with

17 other laboratories to establish a series of reference

scaffolds for porosity and permeability. Our primary

characterization method for these scaffolds is based on

tomographic image analysis of scaffold morphology.

We are developing metrologies for assessing osteoblast

response to pore size distributions in tissue scaffolds based

on extracellular matrix (ECM) production. We are also

investigating morphology effects on osteoblast response

to surface chemistry. The image analysis methods

developed in the reference scaffold activity serve to

support these efforts. The ability to uniformly and

reproducibly seed 3D scaffolds with adherent cells is

another critical factor for quantifying links between

scaffold morphology and cell response, and we have

developed methods to accomplish this.

We are using computational modeling coupled with

high-resolution imaging, atomic force microscopy

(AFM), and optical trapping to develop metrology in

the area of cell response to environmental mechanical

stresses. It is clear that mechanical stimulation is

required for some cell types to differentiate properly.

Thus, it is important to be able to measure precisely

what stress conditions are necessary for proper

phenotypic expression for selected cell types. We are

collaborating with the Materials Reliability Division

of MSEL to establish methods to quantify the stress

conditions at the cellular level based on macroscopic

forces placed on the scaffold construct. Our approach

is to translate ranges of macroscopic stresses to local

stresses experienced by cells using a finite element

model. These local stresses will be correlated with

cell response in terms of ECM production.

Biopreservation of cytokines in tissue scaffolds is a

complex but important area of regenerative medicine that

has been historically underserved. We are collaborating

with six academic and one national lab to create a holistic

approach to stabilizing proteins in solid hosts such as tissue

scaffolds. We are leading the grant-writing efforts in this

collaboration and are focusing on clarifying the relationship

between fast glassy dynamics and biopreserving ability

of a material, which we have already observed in neutron

scattering experiments. In keeping with this goal, we are

establishing accessible time-resolved optical metrologies

for measuring these dynamics.

NIST Contributors and Collaborators

J. Dunkers, F. Wang, J. Cooper, T. DuttaRoy,

J. Stephens, F. Phelan, M.Y.M. Chiang, L. Henderson

(Polymers Division, NIST); Tim Quinn (Materials

Reliability Division, NIST)

Figure 1: A reconstruction of a candidate reference scaffold,

generated from a tomographic image. Each colored object

represents a separate unit cell within the pore structure of the scaffold.

66
3-Dimensional In Situ Imaging for Tissue Engineering:

Exploring Cell/Scaffold Interaction in Real Time

Real time investigations of cell/scaffold

interactions provide valuable information about

the dynamic nature of cells and their spatial

arrangements with respect to the three-dimensional

(3D) architecture of tissue engineering scaffolds.

In situ imaging capabilities will enable determination

of the structure/function relationship of tissue

engineering scaffolds and definition of the

necessary properties to promote tissue

regeneration. We demonstrate tools for

in situ imaging of cells/scaffold interactions.

Jean S. Stephens and Joy P. Dunkers

The ability to image live cells and their corresponding

interactions with the surrounding environment

provides critical information about the ability to promote

desired cellular activity (proliferation, differentiation,

etc.) for tissue regeneration. In order to develop

in situ optical imaging capabilities, we must be able

to nondestructively and noninvasively image the

interactions at the cell/scaffold interface while

maintaining cell viability.

In our laboratory, collinear optical coherent

microscopy/confocal fluorescence microscopy

(OCM/CFM) has successfully been used to image

the 3D interconnected porous structure of polymeric

scaffolds. This system combines high spatial resolution

(~1 μm), high sensitivity (>100 dB), and exceptional

depth-of-penetration associated with OCM with the

fluorescent capabilities of CFM. This, therefore, allows

us to not only investigate the 3D scaffold, but also the

use of conventional fluorescent staining techniques to

evaluate cellular response.

In order to perform live cell imaging, a system

or bioreactor that can sustain cell viability outside of

an incubator and allow for imaging was constructed

(Figure 1). The bioreactor is a perfusion flow

bioreactor. This design forces the media to flow

through the scaffold, therefore ensuring nutrient

delivery and oxygen perfusion, as well as waste

removal, throughout the entire structure. Also, a

dynamic cell culture creates an environment that better

mimics physiological conditions. The temperature

of the bioreactor system is maintained by circulating

water (37 °C) through a copper element.

Figure 1: Bioreactor in OCM/CFM, open and top view.

Figure 2: Time-lapse images of cell movement.

Initial in situ imaging studies indicate the

maintenance of cell viability, and we have successfully

imaged cells for several hours. The series of images

in Figure 2 illustrate cell movement over a 2 hour time

period. The ability to collect images in real time will

give a great insight and understanding of how cells

are responding to different materials, scaffold

architectures, and culture conditions. These data

will provide new metrics for the evaluation of

tissue engineering scaffolds.

Contributors and Collaborators

J.A. Cooper, C.R. Snyder (Polymers Division,

NIST)

Biomaterials

67
Broadband CARS Microscopy for Cellular/Tissue Imaging

In many of the biological sciences, as well as

many areas of polymer science, there is a need

for high-resolution, noninvasive, and chemically

sensitive imaging. We have developed a broadband

coherent anti-Stokes Raman scattering (CARS)

microscopy that provides an unprecedented

combination of imaging speed and spectral coverage

(i.e., chemical sensitivity). Our current efforts are

focused on eliminating nonresonant background

effects, which can limit sensitivity of the technique.

Marcus T. Cicerone

We have developed a broadband CARS microscopy

method which allows us to obtain vibrational

spectra in the range (500 to 3000) cm–1 in less than

1/50th the time required to obtain similar spectra by

spontaneous Raman. This development was reported

at the first meeting of National Institute for Biomedical

Imaging and Bioengineering (NIBIB) grantees, in

Bethesda, Maryland, the 11th Annual Time Resolved

Vibrational Spectroscopy Conference, and the

2005 Biophysical Meeting.

One key to the method we have developed is the

generation of a broadband continuum. Optical pumping

of a tapered silica fiber was used to generate broadband

continuum in the first prototype of this instrument.

Accumulative photo-damage limits the lifetime of the

tapered fiber, and seriously limits the power level of

the light that can be generated, significantly restricting

the taper fiber as a reliable light source for CARS

microscopy. With the assistance of an outside vendor,

we have designed and procured a photonic crystal

fiber (PCF) that is sealed at the ends, and which avoids

the above issues. The PCF did not show any sign of

degradation after a month, under long-term irradiation

of 40 kW peak power femtosecond laser pulses. This

advance provided ≈10-fold increase in signal levels,

so that, in principle, we can gather broadband spectra

in 1/500th the time required for spontaneous Raman

spectroscopy. In practice, this rate exceeds the

capabilities of the CCD camera, which therefore sets

the limits on data acquisition; a faster camera would

allow higher data collection rates.

A blend of chemically similar biodegradable

polymers, abbreviated as DTE and DTO (see Figure

1a), have induced remarkable low immune response

upon fibroblast cell adhesion. These two polymers

phase-separate upon annealing, and since they have

similar indices of refraction, optical microscopy cannot

be used to image the phase-separated domains. On the

other hand, broadband CARS microscopy has the

sensitivity to distinguish the two polymers. Figure 1

shows the three-dimensional imaging of a 50/50

DTE/DTO blend sample. In this sample, the spatial

resolution is approximately 0.4 μm. We are currently

exploring the hypothesis that the low cellular immune

response to the blends has its origins in spatial

patterning of the adhesion proteins. We are working

to correlate the protein adsorption with spatial

patterning of DTO and DTE rich domains.

In Figure 2, bright circular features are triglyceride

lipid droplets in adipocytes, and the more subdued

quasi-circular objects are the cells. We were unable

to image the presence of protein in the cytosol due to

nonresonant background. Detection of these proteins

is crucial to identifying cell type, and we are currently

focusing our efforts on substantially reducing the

effects of nonresonant background.

Contributors and Collaborators

T.W. Kee, H. Zhao, J. Taboas (Polymers Division,

NIST); W-J. Li, R. Tuan (NIH/NIAMS)

Figure 2: Micrograph of adipocyte. This image was obtained without

the use of contrast agents such as fluorescent stains; the 2845 cm–1

C-H stretch vibrational band was the only image contrast.

Figure 1: (a) Chemical structures of DTE and DTO. CARS

images of a 50/50 DTE/DTO blend at depth: (b) 0 μm, (c) 3 μm,

(d) 6 μm. The white areas in these images are DTO; the black

regions are DTE.

Biomaterials

68
Biomaterials

Response of Tissues and Tissue-Engineered Constructs

to Mechanical Stimulation

noted in the reactor at any time in the verification testing.

Stress–strain testing was also accomplished during the

trials. An example of the utility of online monitoring was

evidence of damage to the scaffold in the form of fiber

de-adhesion at a strain of 10 %.

Mechanisms for the Increased Bioavailability

of Materials Using High-Intensity Focused

Ultrasound

At low powers, the mechanical stimulation of

high-intensity focused ultrasound (HIFU) can be used

to increase the permeability of tissues and, therefore,

could be used to increase the effectiveness of drugs

delivered to treated tissues. At these power levels,

the tissue is not permanently damaged but can heal

and return to its original pre-HIFU state.

In order to optimize the HIFU treatment, we need

to know the mechanism by which the tissue is made

more permeable. To understand this, a simple model

of the sound propagation is being developed together

with a parameterized model of the openings (“cracks”)

between cells, and between cells and the extracellular

matrix. Concepts from the field of damage mechanics

(usually reserved for materials like metals) are being

used to develop this model.

Supporting experiments using bovine cardiac tissue

are being conducted to identify the unknown parameters

to the models and to identify the mechanical mechanism

that leads to the increased permeability. This newly

implemented system relies on confocal therapeutic

and imaging ultrasonic elements, packaged together

commercially. A gated function generator and power

amplifier is used to drive the outer, therapeutic HIFU

element in pulsed mode at 1 MHz. An ultrasonic

pulser/receiver simultaneously drives the inner 10 MHz

imaging element and collects data for processing.

The system has a number of unique capabilities for

biological application. The imaging element is used to

monitor the radiation force, which has been proposed

as the main mechanism behind the effect. Following

designs used in the literature, we have constructed a

device to measure the permeability of the tissue samples.

1. Martin, et al., Ann. Biomed. Eng., 27, 656, 1999.

Contributors and Collaborators

A. Slifka, E. Drexler (Materials Reliability Division,

NIST); F. Landis, L. Henderson (Polymers Division,

NIST); V. Frenkel, K. Li (NIH)

Figure 1: The biodegradable scaffold with tissue ingrowth taken

during a stress–strain test. Image correlation is used to measure

strain.

Human coronary smooth muscle cells (passages 7–9)

were obtained from a commercial source and used in

the experiments. The coronary smooth muscle cells

propagated on the scaffold and were seen without difficulty

by day 7 (Figure 1). No evidence of contamination was

Mechanical stimulation of tissue as it is being

grown in a bioreactor has been shown to make

tissue engineered constructs more like healthy,

natural tissue. However, little effort has gone into

studying exactly how the stimulation should be

done.[1] Mechanical stimulation can also be used

for enhanced drug delivery. Researchers at the

National Institutes of Health have been developing

an ultrasonic system to enhance drug delivery in

tumors that are not easily treated with chemotherapy.

We are developing instrumentation and models to

optimize these methods.

Timothy P. Quinn, Tammy L. Oreskovic,

and Brian E. O’Neill

Mechanical Stimulation of

Tissue-Engineered Constructs

Abioreactor has been developed that can provide

 both mechanical stimulation to a tissue-engineered

(TE) construct and mechanical testing while the tissue

is being grown in the bioreactor. The reactor was

designed to facilitate studies to determine the optimal

variables for growing TE constructs for vascular

grafts. In this bioreactor, we can stimulate a planar

sheet of tissue/scaffold construct with an arbitrary

waveform. The reactor can be configured to apply a

given force or a given displacement. It is equipped with

actuators, load cells, and viewports to conduct online,

biaxial stress–strain tests without removing the sample

from the reactor.

69
Biomaterials

Mechanical Behavior of Tissue

crotaline-treated, and hypoxia-treated genetically modified

to disable a receptor responsible for activating vasodilators.

Figure 1 shows the stress–strain behavior of the treated

populations compared with the controls. The difference

between the two hypoxic populations and the controls

are readily obvious. However, the monocrotaline-treated

data indicate that the arteries have not remodeled similarly

to the hypoxic rats, and an entirely different mechanism,

other that arterial wall remodeling, may be operating.

Complementary work is underway on the histology

and quantitative ultrasonic properties of the pulmonary

arteries. The reduction in elastic fiber, which accompanies

the increase in thickness in the hypoxic samples is

consistent with the change in mechanical properties

typically associated with hypertension, where the arteries

become less compliant. The increased thickness of the

medial layer is mostly due to thicker muscular layers

between elastic lamellae. At constant pressures, increases

in thickness and reductions in elastin content contribute

to a stiffer response. We have used quantitative ultrasonic

characterization to correlate mechanical properties due to

remodeling to the ultrasonic properties of the unstressed

remodeled tissue. Ultrasonics is also used to predict

fracture risk in osteoporitic patients. Dispersion

(or how the speed of sound changes with frequency)

appears to be sensitive to changes in bone mineral

density. We organized a topical meeting on ultrasonic

characterization of trabecular and cortical bone that

was sponsored by the Acoustical Society of America.

The results comparing the arteries from the

hypoxia-treated rats to those of the controls, along with

this histology, were presented at the ASME Summer

Bioengineering Conference in Vail, Colorado, in June.

The comparison between the monocrotaline and hypoxic

to the controls will be presented at the Biomedical

Engineering Society Annual Fall Meeting in Baltimore,

Maryland, in September. A manuscript on the technique,

and the control results, was submitted to the Journal

of Biomechanics. Three papers have been published

on the topic of improving quantitative ultrasonics for

tissue characterization, and a NIST IR is now available

summarizing the Inaugural Workshop on Computational

Tools for Modeling Acoustic Propagation in Real-World

Materials. Additional presentations have been made

at the IEEE International Ultrasonics Symposium in

2004 and the 148th Meeting of the Acoustical Society

of America.

Contributors and Collaborators

C. McCowan, K. Waters, A. Slifka, T. Quinn

(Materials Reliability Division, NIST); R. Shandas,

D. Ivy, C. Cool, K. Colvin (University of Colorado

Health Sciences Center)

Using a rat model as a first approximation to the

behavior of human arteries, we have measured the

stress–strain properties of pulmonary arteries from four

different populations: control, hypoxia-treated, monoFigure 1: Graph showing the stress–strain behavior of the control,

hypoxic, and monocrotaline-treated rat pulmonary arteries.

Measurements of the structure and mechanical

properties of biological materials elucidate

mechanisms of disease, and permit quality

assessment of tissue-engineered constructs.

Certain diseases may be identified by changes

in the mechanical properties of the affected

tissue before loss of function is detected, thus

enabling earlier diagnoses and intervention.

Our objective is to provide support to clinicians

by developing measurement techniques and by

measuring the properties of tissue.

Elizabeth S. Drexler

Research on the mechanical properties at the tissue

 level has focused on the properties of pulmonary

arteries with the onset of pulmonary hypertension

(PHT). The onset of PHT is known to cause

remodeling of the walls of the pulmonary arterial

system, and, if left untreated, can lead to right-side

heart failure. We have tested the left and right main

arteries, and the trunk (the arteries most accessible for

clinical diagnostics) in the direction of blood flow and

in the circumferential orientations. Our goals are:

(i) to determine the onset of pulmonary hypertension

by correlating our measured mechanical properties to

the output of tissue Doppler and ultrasound techniques

currently being developed as diagnostic tools and

(ii) to develop structure–property relations.

Monocrotaline vs. Hypoxic Treatments

70
Materials Design for Biomechanical Structures

Biomechanical prostheses such as dental crowns,

total hip and knee replacements, heart valves,

and spinal disk devices are becoming more

commonplace in an ever-aging population.

The lifetimes of such prostheses are limited by

materials properties. Accordingly, it is imperative

that we understand the modes of failure in these

systems, in order that materials can be developed

for superior performance. This program

with extramural partners (New York University,

University of Maryland) and international

institutions seeks to determine fundamental ground

rules for designing biomechanical systems for

improved lifetime performance by identifying

and analyzing clinically relevant damage modes.

Brian Lawn

Cracking and other damage modes in ceramic layers

on soft substrates are of broad general interest

because of the potential for lifetime-limiting premature

failures. This is especially true of biomechanical

prostheses — dental crowns, hip and knee replacements,

heart valves, spinal disk replacements — where ceramic

components introduced to enhance wear resistance,

strength, chemical durability and, in the case of dental

crowns, aesthetics are exposed to cyclic concentrated

loads under stringent in vivo environmental conditions.

A proper understanding of the materials aspects of

any such ceramic-based prosthetic device becomes

a quality-of-life issue. In many such applications the

ceramic is just one component in combination with

polymer and/or metal support sublayers, so a systems

approach is essential.

In this program, we characterize contact-induced

damage modes in model layer systems — bilayers,

trilayers, and even multilayers — that simulate the

basic loading features of biomechanical structures and,

at the same time, allow direct in situ observations of

the damage evolution during loading and unloading.

The most revealing are model layer structures made

from transparent components, e.g., ceramic coating

layers on clear polymer substrates, or glass coatings

on metal substrates. Critical conditions for damage

initiation can then be directly monitored and quantified.

Using this approach, we have been able to identify

damage modes believed to be responsible for the

failure of clinical prostheses, especially dental crowns.

Analytical relations expressing the critical applied loads

(e.g., biting force, body weight on hip replacements)

in terms of ceramic layer thicknesses and material

properties (strength, toughness, modulus, hardness)

have been determined. These relations can be used

to predict optimal interlayer dimensions and material

properties for any given layer system. Design criteria

for this optimization are being laid down.

This work has been funded by the National

Institute of Dental and Craniofacial Research.

Materials scientists, engineers and clinicians are

involved. The first five-year stage of this program

has been completed. A second five-year stage is under

way. Several dental materials companies participate

in this program.

Publications

Brian Lawn’s publications can be viewed and

downloaded at http://www.msel.nist.gov/lawn/

index.html.

Contributors and Collaborators

D. Rekow, V. Thompson, Y. Zhang (New York

University); I. Lloyd (University of Maryland); A. Pajares,

F. Guiberteau, P. Miranda, E. Sanchez (University of

Extremadura); M. Bush, X. Hu (University of Western

Australia); S. Bhowick, I. Hermann, J.-W. Kim (Guest

Scientists); Ivoclar-Vivadent (Norton-Desmarquest);

V. Zahnfabrik (Ceramco, Therics)

Biomaterials

71
Biomaterials

Molecular Design and Combinatorial Characterization

of Polymeric Dental Materials

Polymeric dental materials are finding increasing

applications in dentistry and allied biomedical

fields. As part of a joint research effort supported

by the National Institute of Dental and Craniofacial

Research and also in collaboration with the

American Dental Association Health Foundation

Paffenbarger Research Center, NIST is providing

the dental industry with a fundamental knowledge

base that will aid in the prediction of clinical

performance of dental materials.

Joseph M. Antonucci and Sheng Lin-Gibson

I

n contrast to current methods that rely on

one-specimen-at-a-time measurements, metrologies

based on combinatorial and high-throughput (C&HT)

approaches can accelerate fundamental and applied

research in dental materials. For dental polymers

and their derivatives (sealants, adhesives, restorative

composites), many critical properties depend on the

chemical, structural, and compositional nature of the

initial monomer (resin) system. For multiphase dental

materials, e.g., composites, similar factors govern the

quality of the interphase between the silanized filler phase

and the resin matrix. The objective of this research was

to determine the feasibility of adapting C&HT techniques

to measure material properties and screen various

experimental resin chemistries for molecular design of

novel dental polymers and composites. The technologies

developed to enable this research include nanoindentation

and the fabrication of single component or multi-variable

discrete and continuous gradient films.

instability for mechanical measurements test. SIEBIMM

on PMMA, a linear polymer, yielded a modulus comparable

to that obtained by the 3-point bend test. Buckling patterns

from cross-linked BisGMA/TEGDMA films (Figure 1)

resulted in moduli with increased variability, i.e., the

buckling patterns were not straight, parallel lines.

Reasons for this behavior are under study.

Figure 2: Elastic moduli of photopolymerized BisGMA-TEGDMA

of different compositions as a function of irradiation time

(represented as distance).

Figure 1: Buckling patterns of BisGMA-TEGDMA in mass ratios

of 30:70 (left) and 70:30 (right).

BisGMA-TEGDMA networks with 2D gradients,

varying in monomer composition and conversion,

were fabricated with a broad conversion range for all

monomer compositions. Conversions were measured

using near-IR spectroscopy, and elastic modulus and

hardness. As shown in Figure 2, the conversion and

the mechanical properties correlated well.

Additional techniques with the potential for C&HT

approaches are being evaluated for their ability to screen

other properties of dental materials, including the interfacial

silane chemistry and cellular response. Studies on the

interfacial chemistry have shown that covalent bonding

of nanoparticles with the polymerized matrix resulted in

well-dispersed composites. To screen the biological

response to dental materials, methods to measure cell

viability, apoptosis, and gene expression levels as a function

of vinyl conversion have been developed.

Contributors and Collaborators

E.A. Wilder, K.S. Wilson, N.J. Lin, C.M. Stafford,

L. Henderson (Polymers Division, NIST);

P.L. Votruba–Drzal (Materials and Construction

Research Division, NIST)

 Among the different resin chemistries under

investigation, 2D compositional gradients using BisGMATEGDA were selected as the benchmark for developing

metrologies and rapid screening techniques for optimizing

hardness, shrinkage, and biocompatibility. The elastic

modulus was determined by two methods, nanoindentation

and SIEBIMM — a strain-induced elastic buckling

72
Safety and Reliability

includes the development and innovative use of

state-of-the-art measurement systems; leadership in

the development of standardized test procedures and

traceability protocols; development of an understanding

of materials in novel conditions; and development and

certification of Standard Reference Materials® (SRMs).

Many of the tests involve extreme conditions, such as

high rates of loading, high temperatures, or unusual

environments (e.g., deep underwater). These extreme

conditions often produce physical and mechanical

properties that differ significantly from handbook values

for their bulk properties under traditional conditions.

These objectives will be realized through innovative

materials property measurement and modeling.

We take for granted that the physical infrastructure

around us will perform day in and day out with

consistent reliability. Yet, failures occur when these

structures degrade to where they no longer sustain their

design loads, or when they experience loads outside

their original design considerations. In addition, we

have become increasingly aware of our vulnerability to

intentional attacks. The Safety and Reliability Program

within MSEL was created to develop measurement

technology to clarify the behavior of materials under

extreme and unexpected loadings, to assess integrity

and remaining life, and to disseminate guidance and

tools to assess and reduce future vulnerabilities.

Project selection is guided by identification and

assessment of the particular vulnerabilities within

our materials-based infrastructure, and focusing on

those issues that would benefit strongly by improved

measurements, standards, and materials data. This year,

we have worked with the Department of Homeland

Security and the Office of Science and Technology

Policy in developing the National Critical Infrastructure

R&D Plan, which will provide guidance across much

of the national infrastructure. Ultimately, our goal is

to moderate the effects of acts of terrorism, natural

disasters, or other emergencies, all through improved

use of materials.

Our vision is to be the key resource within the

Federal Government for materials metrology

development as realized through the following

objectives:

■ Develop advanced measurement methods needed by

industry to address reliability problems that arise with

the development of new materials;

■ Develop and deliver standard measurements and data;

■ Identify and address vulnerabilities and needed

improvements in U.S. infrastructure; and

■ Support other agency needs for materials expertise.

This program responds both to customer requests

(primarily other government agencies) and to the

Department of Commerce 2005 Strategic Goal of

“providing the information and framework to enable

the economy to operate efficiently and equitably.”

For example, engineering design can produce safe

and reliable structures only when the property data

for the materials are available and accurate. Equally

important, manufacturers and their suppliers need to

agree on how material properties should be measured.

The Safety and Reliability Program works toward

solutions to measurement problems on scales ranging

from the macro to the micro. The scope of activities

The MSEL Safety and Reliability Program is

also contributing to the development of test method

standards through committee leadership roles in

standards development organizations such as the

ASTM International and the International Standards

Organization (ISO). In many cases, industry also

depends on measurements that can be traced to

NIST SRMs.

In addition to the activities above, MSEL provides

assistance to various government agencies on homeland

security and infrastructural issues. Projects include

assessing the performance of structural steels as part of

the NIST World Trade Center Investigation, collaborating

with both the Department of Transportation and the

Department of Energy on pipeline safety and bridge

integrity issues, advising the Bureau of Reclamation on

metallurgical issues involving pipelines and dams, and

advising the Department of the Interior on the structural

integrity of the U.S.S. Arizona Memorial.

Contact: Thomas A. Siewert (Materials

Reliability Division),

Frank W. Gayle (Metallurgy Division)

Program Overview

73
Safety and Reliability

Analysis of Structural Steel from the World Trade Center

In 2005 NIST completed the three-year Federal

Building and Fire Safety Investigation of the

World Trade Center Disaster. The investigation

addressed many aspects of the catastrophe, from

occupant egress to factors affecting how long the

WTC towers stood after being hit by the airplanes,

with a goal of gaining valuable information for

the future. A critical aspect of the investigation

was the metallurgical analysis of the recovered

structural steel. The analysis included

characterization of mechanical properties,

failure modes, and structural response

determined from photographic evidence.

William E. Luecke, Stephen W. Banovic,

Timothy J. Foecke, J. David McColskey,

Christopher N. McCowan, Richard J. Fields,

Thomas A. Siewert, and Frank W. Gayle

The collapse of the World Trade Center (WTC)

towers was the worst building disaster in human

history. Engineers, emergency responders, and the nation

were largely unprepared for such a catastrophe. The task

of the NIST investigation was to determine the details

of why and how the towers collapsed. As part of this

investigation, the Metallurgy and Materials Reliability

Divisions characterized the recovered structural steel.

The project is comprised of five tasks:

1. Collect and catalog physical evidence.

2. Categorize failure mechanisms from visual evidence.

3. Determine steel properties to support modeling.

4. Correlate determined and specified steel properties.

5. Analyze steel to estimate temperature extremes.

Analysis of fracture surfaces of recovered perimeter

columns struck by the aircraft showed that the steel

remained ductile even at high deformation rates. Data

such as these were important in assuring the accuracy

of the steel properties supplied to the modeling efforts.

Photographic analysis demonstrated that perimeter

columns of WTC 2 began to pull into the building

almost 30 minutes before collapse. Our staff developed

pull-in maps based on pre-collapse photographs,

Figure 1, which were instrumental in constraining

the finite element models of the building deformation.

Figure 2: Measured yield strength of perimeter column specimens.

Figure 1: Pull-in map of perimeter columns (in inches) on the

east face of WTC 2, 9:03 a.m.

Tensile tests of the dozens of steel types and grades

recovered showed that their yield and tensile strengths

are consistent with the expected values. In a few cases,

the strengths of the NIST-tested specimens were slightly

less than called for, but the number of under-strength

samples is consistent with the natural variability in steel

strength and the damaged state of the recovered steel.

Figure 2 shows the ratio of measured to specified yield

strength for recovered perimeter column steels.

Photographic evidence indicated that 16 of the

recovered perimeter column panels from WTC 1 were

exposed to fire before the collapse. Our staff developed

a forensic test based on paint cracking due to thermal

expansion of the steel. This test placed limits on the time

and temperature exposure of the recovered columns.

Results indicate that only three locations on these 16

recovered columns reached temperatures above 250 °C.

The final draft of the investigation report was issued

for public comment in June 2005.

Contributors and Collaborators

R. Santoyo (Materials Reliability Division, NIST);

M. Iadicola (Metallurgy Division, NIST)

74
Infrastructure Reliability: Charpy Impact Machine Verification

We assist owners of Charpy impact machines in

achieving conformance with the requirements of

ASTM Standard E 23. We interact with the ASTM

Committee responsible for the Charpy impact

standard, to improve the service and to maintain

a high-quality verification program. We also

participate in the activity in ISO Committee TC

164, so our specimens and procedures remain

compatible with the associated international and

regional standards.

Thomas A. Siewert

Technical Description

The Charpy impact test uses a swinging hammer to

assess the resistance of a material to brittle fracture.

The absorbed energy is measured from a calibrated

scale, encoder, and/or an instrumented striker. The low

cost and simple configuration of the test have made it

a common requirement in codes for critical structures

such as pressure vessels and bridges. This project is

handled jointly by the Standard Reference Materials

Program (of the Office of Measurement Services),

which oversees the administrative aspects of the

program, and the Materials Reliability Division,

which handles the technical and verification aspects.

NIST provides highly characterized Standard

Reference Materials® (SRMs) to machine owners

and independent calibration services, then evaluates

the results of tests of these specimens on their

impact machines. Owners of machines that meet the

requirements of ASTM Standard E 23 are given a letter

of conformance, while owners of nonconforming

machines are given recommendations on corrective

actions. Our special facilities include three master

Charpy impact machines (all 300 J to 400 J capacity).

These three machines are used to establish certified

values for the NIST reference materials sold through

the Standard Reference Materials Program Office.

In addition, we have several more machines

(3 J to 400 J capacities) that are used for research

purposes.

Accomplishments

Ray Santoyo continues in his role as Charpy

Coordinator. We have served about 850 customers

in the past year, a slight increase over the year before.

The great majority of these machines were within

tolerances required by ASTM Standard E 23.

As usual, many customers took advantage of our

support services, as shown by over 674 emails,

730 faxes, and 500 phone calls in the first 9 months

of FY05. We immediately contact the machine

owner if their machine fails to meet the verification

criteria. In this contact (by phone, mail, email, or fax),

we suggest corrective measures.

NIST’s support of ISO Standard 17025 means

that we have been reformatting our quality manual for

the Charpy program to match the new NIST styles

and to fit with the overall NIST Quality Manual (QM-I).

Thus, Chris McCowan has refined our Division quality

manual (QM-II) and the Charpy program manual

(QM-III) to match those of the other Laboratories

and Divisions. We expect to perform an independent

audit by September 2005 and then formally adopt

these new quality manuals.

 We helped to organize another international

symposium, the Second Symposium on Pendulum

Impact Machines: Procedures and Specimens, held in

conjunction with the November 2004 meeting of ASTM

Committee E 28 in Washington, D.C. We also helped

to lead the symposium and contributed to three of the

papers. Previous symposia have provided valuable

insight into improvements in our program.

This year, we produced the first batch of Izod

impact verification specimens, which has been tested

and is undergoing statistic evaluation. Soon, it is

expected to enter inventory as SRM 2115.

Chris McCowan serves as the Chairman of ISO

TC164 SC4 P, on pendulum impact and also as

the Chairman of ASTM Subcommittee E28.07 on

impact testing.

Contributors and Collaborators

R. Santoyo (Charpy Program Coordinator);

C. McCowan, J. Clark, D. Cyr, C. Dewald, S. Vincent,

N. Neumeyer, J. Percell (Materials Reliability Division,

NIST); IRMM (Europe); NRLM (Japan); Members of

ASTM Subcommittee E 28.07

Safety and Reliability

75
Standard Test Methods for Fire-Resistive Steel

The fires and subsequent collapse of the

World Trade Center focused attention on the

vulnerability of structural steel to fire. Recently

steels designated as “fire-resistive” have become

available. This project is developing a standard

test method for quantitatively evaluating and

comparing the resistance of structural steels to

high-temperature deformation.

William E. Luecke and J. David McColskey

All steels lose strength with increasing temperature.

 By 600 °C, most structural steels have lost more

than half their strength. At intermediate temperatures

the strength is independent of time, but above 500 °C,

creep, or time-dependent deformation, further reduces

the load-carrying capability. To combat this loss of

load-carrying capability, structural steel in buildings is

insulated to keep it cool in fire.

Fire resistive (FR) steels are intended to be drop-in

replacements for existing grades of structural steel.

They can meet the same specifications, have similar

weldability, cost only marginally more, but have

superior elevated temperature strength. Their superior

high-temperature properties have the potential to provide

extra time for building occupants to escape a fire.

In Japan and Europe, FR steels are qualified based

on high-temperature retained yield strength. Although

this definition employs a simple, familiar test, because

it is a short-term test, it ignores the time dependence

of the deformation resistance. Domestic standards for

structural components use a critical temperature criterion

for failure of steel, so effectively all steels are identical,

regardless of high-temperature deformation resistance.

We are studying three possible test methods

for standardization. The first is the conventional

high-temperature retained yield strength. The second

is a slow-rate (several hours to failure) tension test,

which should capture the time-dependent deformation

effects. The third method is a hybrid of a creep and a

conventional tension test in which the test specimen is

held under constant load as the test temperature ramps

upward linearly. Over a narrow temperature range,

which can be approximated as a critical temperature,

the deformation rate increases drastically, and the

specimen fails. This critical temperature can be used

as a measure of the fire-resistance.

One goal of this project is to build on recent

worldwide research on similar tests, but to take the

proof of concept to a draft standard. Each potential

method has advantages, but there has been no

research to compare the results of each to the others.

Our research focuses on understanding the limitations,

repeatability, and reproducibility of the methods by

characterizing several different classes of construction

steels. In the near term, after selecting a single method,

we will organize an interlaboratory study (ILS) to

probe the limitations and establish precision and bias.

Figure 1 compares the behavior of two FR steels

evaluated using high-temperature, tensile yield strength,

Fy, measured in a high-temperature tensile test and the

critical temperature evaluated using the temperature ramp

test. Although the normalized yield strengths diverge

significantly above 600 °C, the critical temperatures

measured in the ramp tests are very similar.

Contributors and Collaborators

R.J. Fields (Metallurgy Division, NIST)

Figure 1: Comparison of tensile and ramp tests.

Safety and Reliability

76
Frangible Bullets and Soft Body Armor

The NIST Office of Law Enforcement Standards

(OLES) is currently involved in modifying existing

standards for the ballistic resistance of personnel

body armor and providing new performance

standards for frangible bullets (designed to

fully disintegrate on impact with hard surfaces).

The deformation behavior of this frangible

material when impacting a soft surface such

as NIJ Level II or IIIA soft body armor is not as

predictable as conventional bullets and requires

a better understanding of the high-strain rate

deformation behavior of the fabrics used in soft

body armor and the various frangible materials.

Stephen D. Ridder and Steven P. Mates

As part of this multi-year project, the Metallurgy

 Division is testing Pressed and Sintered Cu-Sn

(PS Cu-Sn) bullets, one of the frangible ammunition

materials selected for testing by OLES. PS Cu-Sn

frangible material is made by blending a 9:1 mass ratio

of Cu and Sn powder with nominal particle sizes of

50 μm, pressing the powder mixture in molds and

then using transient liquid phase sintering to bind the

compacts and form a Cu-Sn reaction layer (≈30 min @

260 °C). Sintering time and temperature are controlled

to limit the reaction zone and avoid formation of the

less frangible α-bronze phase.

Microstructural analysis of the as-received PS

Cu-Sn material has shown that the matrix consists of a

mixture of copper particles with varying morphologies

— some with equiaxed grain structures and others with

Cu-P precipitates (possibly the result of copper powder

from different suppliers). EDS analysis indicates that

the binding region between the copper matrix particles

consists of columnar grained Cu3Sn (ε) phase, a more

blocky shaped Cu6Sn5 (η ́) phase, and unreacted Sn.

SEM fractographs of Kolsky Bar specimens have

shown brittle fracture in the ε phase, brittle cleavage

in the η ́ phase, and ductile failure with micro-void

coalescence in the copper matrix adjacent to the

intermetallic layers.

The mechanical deformation of PS Cu-Sn frangible

bullets has been examined at conventional strain rates

and at high strain rates in compression in the NIST

Kolsky Bar facility. Kolsky bar tests have been

performed to assess the compressive stress–strain

behavior at strain rates up to 103 s–1. Dynamic tensile

strength has also been measured using the Kolsky Bar

to perform diametral compression tests, or Brazil tests.

In this test, a disk of the bullet material is exposed to

Safety and Reliability

a rapidly rising stress pulse along its diameter, which

creates a tensile stress perpendicular to the applied load.

A crack eventually forms due to this tensile stress, from

which the tensile strength can be measured. Typical

Brazil tests involve purely brittle materials, and only the

elastic deformation behavior of the sample is needed to

determine tensile strength. However, in the case of

frangible bullet materials, significant plastic deformation

was observed before failure. Finite element modeling

(Figure 1) was used to determine how plastic yielding

affected the evolution of tensile stress in the sample

during the test in order to obtain a more accurate

estimate of the tensile strength. The high-strain rate

plastic flow and tensile strength data can then be used

to model the deformation and breakup of a frangible

bullet as it impacts a soft armor-like surface.

Expected Impacts

These data and associated bullet impact modeling

efforts will be used by the NIST Office of Law

Enforcement Standards in a continuing effort to develop

a performance standard for frangible ammunition and in

the revision of the National Institute of Justice Ballistic

Resistance of Personnel Body Armor Standard.

Contributors and Collaborators

S. Banovic, R. Fields, L. Levine, L. Ma (Metallurgy

Division, NIST); M. Kennedy, R. Rhorer, E. Whitenton

(Manufacturing Metrology Division, NIST); T. Burns

(Mathematical and Computational Sciences Division,

NIST)

Figure 1: 3-D simulation of diametral test of frangible

ammunition cross-section.

77
Pipeline Safety: Corrosion, Fracture, and Fatigue

A critical element of the nation’s infrastructure is

the more than 3 million km of natural gas and

hazardous liquid pipelines that deliver almost 2/3

of the nation’s energy. Following the passage of

the Pipeline Safety Improvement Act in 2002, NIST

began working with the pipeline industry, DoE,

DoI’s Minerals and Management Service, and

DoT’s Office of Pipeline Safety to provide the

measurement methods, standards, and data needed

to understand corrosion, fracture, and fatigue

failure mechanisms in this critical element of the

nation’s infrastructure.

Richard E. Ricker and J. David McColskey

After Congress passed the Pipeline Safety Improvement

 Act in 2002, NIST, DoE, and DoT developed a

memorandum of understanding (MOU) detailing

a coordinated program of research, development,

demonstration, and standardization. The goals of the

program are to continue improvements in the safety and

operation of pipelines and related facilities. NIST has a

long history of contributions to pipeline safety and, in this

project, is responsible for materials research addressing

concerns with corrosion, fatigue, and fracture, especially

as pipelines are pushed to higher performance using new

materials and higher pressures.

in the original study to that determined by modern

computer curve fitting routines. This figure shows:

(i) strong evidence of non-linear kinetics and decreasing

corrosion rates, and (ii) that only minor differences

were obtained with modern analysis. In both original

and new analyses, the scatter in the data limits the

conclusions. The origin of this scatter needs to be

understood before less conservative non-linear kinetics

can be used for rate models.

Safety and Reliability

At the urging of the Pipeline Research Council

International (PRCI) and DoT’s Office of Pipeline

Safety (OPS), NIST reexamined data from the original

NBS underground corrosion studies conducted between

1920 and 1957, involving over 36,000 samples buried at

128 different sites across North America. The original

study was found to be thorough and ahead of its time

with respect to statistical analysis. Figure 1 compares

the results of the power law exponent fit determined

Figure 1: Corrosion analysis (historical data), power law exponents.

Figure 2: Crack tip opening angle behavior — conventional steel.

Fracture and fatigue studies are underway on

both traditional and modern steels. By acquiring and

publishing data on these properties, NIST hopes to

enable better modeling of performance. The focus of

this study is to assess the ability of different pipeline

steels to arrest crack propagation. Crack tip opening

angle (CTOA) measurements were made on samples

cut from the pipeline samples. Figure 2 shows the

CTOA measurements on two baseline steels and the

region of stable crack growth.

Working with OPS, MMS (DoI), DoE, PRCI,

American Gas Association, the Gas Technology Institute,

ASTM Intl. NACE Intl. CANMET, and the National Energy

Board (Canada), NIST organized a workshop on Advanced

Coatings for Pipelines and Related Facilities held at NIST

June 9–10. Sixty representatives of the pipeline industry,

suppliers, and government agencies from the U.S., Canada,

and the UK attended this meeting. NIST also assisted

OPS in organizing the Government/Industry Pipeline R&D

Forum in Houston, Texas, March 22–24, 2005.

Contributors and Collaborators

F. Gayle, T. Foecke, S. Mates, R.J. Fields,

C. Handwerker (Metallurgy Division, NIST); T. Siewert,

C. McCowan (Materials Reliability Division, NIST);

M. Smith (PRCI); C. Sames (AGA); J. Merritt, S. Gerard,

R. Smith (DoT/OPS); C. Freitas, R. Anderson, D. Driscoll

(DoE); M. Else (DoI/MMS)

78
Polymer Reliability and Threat Mitigation

This project is developing metrologies and

predictive models to test and predict the long-term

reliability of polymers used in ballistic resistant

armor and machine readable travel documents.

Use of these methods and models will enable one

to monitor the performance of polymeric materials

while in use, elucidate how environmental and

mechanical factors influence performance, and

provide a basis for estimating durability and

establishing care procedures.

Chad R. Snyder, Gale A. Holmes, and

Walter G. McDonough

Ballistic Resistant Armor

I

n response to an apparent failure of ballistic resistant

 armor during first responder use, NIST’s Office of Law

Enforcement Standards initiated a research program

designed to strengthen the certification process of these

protective devices. We are working to identify and develop

analytical metrologies for quantifying the mechanical

properties and degradation pathways of ballistic fibers that

comprise this armor, with the ultimate goal being an

estimate of vest durability and care procedures.

as quantified through the method of Cuniff and Auerbach.

Ongoing research is examining the effects of fold radius

as well as the effects of repeated folding.[1]

Complementing our mechanical properties studies,

our research into the degradation pathways of PBO

and PBO-like materials has made significant headway.

In addition to completion of our review article,[2]

we have synthesized the model compounds

2-phenylbenzoxazole and bis-1,4-(2-benzoxazolyl)

phenylene, and their hydroxy analogs, and we are

currently analyzing, through matrix assisted laser

desorption/ionization (MALDI) mass spectrometry,

the degradation products resulting from exposure to

our newly acquired solar simulator.

Machine Readable Travel Documents

As indicated in an October 14, 2004 press release

from the U.S. Government Printing Office (GPO),

NIST is testing the candidates for the new U.S.

electronic passports for their ability to meet durability,

security, and electronic requirements. This new

technology will eventually be incorporated into

electronic U.S. passports to enhance the security

of millions of Americans traveling around the world.

At the request of the U.S. Department of State, we

participated in the WG3 (Working Group 3 of ISO)

meeting of the Document Durability Task Force for

the EPassport in Tsukuba, Japan. The purpose of the

task force meeting was to update the participants on the

status of the Test Specification for Machine Readable

Travel Documents (MRTD). The main recommendation

from the meeting was that any proposed test specification

by ISO would serve as the guideline to help nations

writing requests for proposals to develop their own

MRTDs. Also, the task force chairs have decided to

use more complex testing sequences to better represent

real-world applications; this was in line with the

recommendations made by NIST.

References

1. P.M. Cunnif and M.A. Averback, 23rd Army Science

Conference, Assistant Secretary of the Army (Acquisition,

Logistics and Technology), Orlando, FL (Dec. 2002).

2. G.A. Holmes, K. Rice, and C.R. Snyder, Journal of

Materials Science, in press.

Contributors and Collaborators

J. Dunkers, C.M. Guttman, K. Flynn, J. Kim,

F.A. Landis, D. Liu, W. Wallace (Polymers Division,

NIST); D. Novotny, J. Guerrieri, G. Koepke, M. Francis,

N. Canales, P. Wilson (Electromagnetics Division, EEEL);

K. Rice (Office of Law Enforcement Standards, EEEL);

T. Dang (Air Force Office of Scientific Research)

This year, we have made considerable progress on

multiple fronts towards these goals for poly(benzoxazole)

(PBO) ballistic fibers. The modified single fiber

fragmentation test, developed last year, was used to

examine the effect of fiber fatigue on ballistic resistance.

Figure 1 shows the effect of folding on the morphology

and mechanical properties of a PBO fiber. Our analysis

suggests that, for this case, folding resulted in an

estimated >10 % reduction in overall ballistic performance,

Figure 1: Top and Left: Micrograph and yield strength data

obtained from modified single fiber test on an unfolded PBO fiber;

Bottom and Right: Micrograph and figure for a folded PBO fiber.

Safety and Reliability

79
Facilities and Capabilities

space, while single crystal methods can be adapted to

high-resolution analysis of materials such as thin films.

However, results from both powder and

high-resolution techniques are affected by a complex

optical aberration function that is specific to the

diffraction optics and goniometer assembly used in

the experiment. NIST Standard Reference Materials

(SRMs) are the recognized means by which these

aberrations may be characterized to achieve improved

measurement accuracy. To address these issues,

Dr. James Cline of the Data and Standards Technology

Group conceived and designed the Ceramics Division

Parallel Beam Diffractometer (CDPBD).

Advanced Measurement Capabilities

UHV STM/AFM

Figure 1: Ultrahigh vacuum STM/AFM apparatus.

Figure 2: The Ceramics Division Parallel Beam Diffractometer

in the AML.

Enhanced by the superior vibration isolation and

clean room environment in NIST’s new Advanced

Measurement Laboratory (AML), our UHV STM/AFM

system, Figure 1, provides atomic imaging and force

measurement with an unprecedented resolution and

accuracy. Combined with our conventional AFM,

equipped with a “triboscope” attachment, we are able

to image and manipulate surface features and measure

a wide range of material characteristics and properties

important in nanodevice operation. As a result, we

now are leading fundamental metrological efforts,

working with device and magnetic hard disk industries,

as well as academic institutions, to establish reliable

measurement methods, calibration artifacts, and

infrastructural support for current and future industries.

High Resolution X-ray Metrology

Powder and single crystal x-ray diffraction are

widely used in industry, research facilities, and

academia as one of the principal means of characterizing

materials. Both techniques yield a wealth of information

on the crystallographic and microstructural character of

the specimen. The powder diffraction method has the

virtue that it can probe a continuous sequence of

crystallographic reflections with a single scan in angular

The CDPBD, Figure 2, was designed and built

specifically to perform traceable measurements on

powder and thin film specimens. Installed in the new

NIST Advanced Measurement Laboratory, this facility

provides the environmental and temperature controls

requisite for a new generation of NIST SRMs that

will enable unprecedented measurement accuracy in

a highly competitive, data conscious, materials

research community.

Facilities and Capabilities

80
X-ray Absorption Spectroscopy

Advances in our x-ray absorption spectroscopy

facilities have achieved an unrivaled capability enabling

our Characterization Methods Group (CMG) to address

a remarkably broad range of challenging structure and

chemistry issues at the forefront of materials science

research today. Through the application of a truly

unique combination of beamline facilities, we are able

to examine characteristics of surfaces, interfaces, and

bulk materials in a manner heretofore inaccessible.

Figure 3: The soft x-ray spectroscopy station on beamline U7A.

Facilities and Capabilities

To achieve this capability, CMG, led by Dr. Daniel

Fischer, brought together a suite of three unique

high-throughput x-ray spectroscopy beamlines

(designated U7A, X24A, and X23A2). Housed in the

National Synchrotron Light Source located at Brookhaven

National Laboratory in New York, these beamlines,

taken together, can easily examine nearly all of the

naturally occurring elements in the entire periodic table.

This year, the capabilities of beamline U7A, used for

soft x-ray materials science applications, were

significantly enhanced by the addition of a 14 element,

state-of-the-art, Si (Li) fluorescence yield detector,

providing best-in-the-world resolution. Further

enhancement of U7A, Figure 3, was achieved through

the installation of a 6-axis manipulator that enables the

exciting prospect of molecular alignment studies.

Figure 4: Tammy Oreskovic adds cells to a tissue-engineered

scaffold.

Building on these capabilities, CMG has initiated

a long-term plan, co-funded with Sandia National

Laboratory, for establishing a variable energy XPS

(x-ray photoelectron spectroscopy) and NEXAFS/EXAFS

(near edge/extended x-ray absorption fine structure)

scientific program utilizing beamline X24A. A new,

fully automated materials science end-station is planned,

modeled after the very successful high throughput

attained on U7A. The emphasis for this work will

be on the use of variable energy XPS for chemical

depth profiling, sub-surface chemistry, and interface

chemistry.

Combinatorial Thin Film Laboratory

A new laboratory for the synthesis of inorganic

combinatorial thin-film libraries is under construction.

Combinatorial methodologies can greatly accelerate

the optimization of materials in complex systems and,

thus, their introduction into commercial products.

The Ceramics Division’s state-of-the-art combinatorial

deposition tool will have dual capability, featuring

sputtering as well as pulsed laser deposition (PLD)

chambers. The tool will be used to synthesize

libraries of multilayer structures, such as advanced

complementary-metal-oxide-silicon (CMOS) gate

stack structures, in situ, for metrology development

and characterization studies.

Tissue Engineering (TE) Bioreactors

The Center for Mechanical Behavior of Biological

Materials (CMBBM) has developed unique bioreactors

that allow for experiments to optimize the variables that

81
Figure 5: BioMEMS devices fabricated at NIST allow the

measurement of single-cell mechanical properties.

Facilities and Capabilities

control the mechanical properties of the engineered

tissue. The bioreactors that have been developed

provide mechanical stimulation to a TE construct and

measure mechanical properties while the tissue is being

grown in the bioreactor. Cyclic, mechanical stimulation

of TE constructs is necessary to make the constructs

more like natural tissue. In these bioreactors, we can

stimulate a planar sheet of tissue/scaffold construct with

an arbitrary waveform. The reactor can be configured

to apply a given force or a given displacement.

The bioreactor is equipped with actuators, load cells,

and view ports to conduct biaxial stress–strain tests

without removing the sample from the reactor. We are

equipped with the necessary equipment to culture tissue

and assess its growth and viability.

Optical Trap

We have assembled an optical trap that uses a

scanned laser at 1064 nm as the trapping source.

The long wavelength allows us to make measurements

on biological samples with minimal damage to cellular

proteins. The scanned laser system provides multiple

time-shared traps and movement of trapped objects so

that transient mechanical measurements can be made.

The laser operates from 100 mW to 500 mW, providing

a range of trap stiffnesses. Trap stiffnesses on the

order of 10-6 N/m are typical, which allows mechanical

measurement of cells, subcellular fibers and structures,

DNA strands, and assembled nanoparticles.

Crack-Tip Opening Angle

Mechanical Testing

Better measurements of the tendency to stop a

running crack in a structure come from a new test

called crack-tip opening angle (CTOA). This test

measures the angle at which a crack progresses at a

stable rate through a material with a fatigue precrack.

It has substantial advantages over its predecessor,

the crack-tip opening displacement test, by allowing

multiple measurements directly at the crack tip.

We are using our system to measure the crack arrest

tendencies of a variety of pipeline steels. Improvements

that we make in the procedures are being fed back to

the ASTM Committee (E08.08) responsible for its

development and promulgation.

MEMS Fabrication Facility

The fabrication facility at NIST–Boulder is a

200 square meter multifunction class 100 clean room

capable of 50 nm linewidths. It is currently used to

fabricate micro- and nanoelectromechanical systems

(MEMS/NEMS/BioMEMS) which are essential to

much of the ultra-sensitive equipment designed

and used across many divisions at NIST.

From start to finish, all aspects of small-scale

fabrication are available within the NIST facility.

The facility includes: computer-aided design (CAD),

a pattern generator (PG), a 5x wafer stepper or a 1x

contact printer with backside alignment capability,

an electron beam lithography system, various sputter

and e-beam deposition tools, as well as an electron

cyclotron resonance (ECR) system for low-temperature

plasma-enhanced chemical vapor deposition (PECVD),

a multiuse chemical vapor deposition (CVD) furnace

bank, various reactive ion etching (RIE) tools, a XeF2

isotropic etcher, a chemical mechanical polisher (CMP)

for planarization, and a deep reactive ion etcher (DRIE).

The facility is professionally staffed by experienced and

knowledgeable NIST researchers.

Biaxial Membrane Test Capabilities

The Materials Reliability Division in Boulder,

Colorado, has a program in measuring the mechanical

behavior of biological materials. One facet of that

program is to measure the biaxial, load-displacement

behavior of membrane-like tissue. That is accomplished

with a bubble test fixture and a computer-driven system

to pressurize the specimen and collect images from four

cameras. The multiple camera angles (3 side views +

stage rotatability, and 1 top view) allow capture of

anisotropic displacement behavior. We have two

different sized fixtures, 2.38 and 20.0 mm in diameter,

so we can test materials of different thicknesses while

maintaining the 1:10 thickness-to-diameter ratio required

for a valid bubble test. All tests on natural tissue are

conducted in a 37 °C, phosphate-buffered saline water

bath to sustain cell viability.

Laboratory Setup and

Establishment of Cell Lines

The biological laboratory in the Materials Reliability

Division has approximately 400 square feet available

82
Facilities and Capabilities

within two adjacent lab areas. A fully equipped tissue

culture facility is available for culturing vascular smooth

muscle cells and future osteoblast-like and fibroblast

cell lines. Also, a flow bioreactor for mechanical

evaluation of biological scaffold materials with a

specially modified incubator is available. Laboratory

equipment includes a biological laminar flow hood with

ultraviolet lights, two water-jacketed CO2 incubators,

benchtop centrifuge, liquid nitrogen storage vessel,

inverted microscope with fluorescent capabilities and

integrated firewire camera and analysis software,

refrigerator (4 oC)/freezers (–20 oC & –50 oC), and

an automated plate reader. Additionally, a probe station

for conducting Bio-MEMS testing and single-cell

experiments occupies one of the lab areas.

Ultrasonic Imaging and

Measurement Facilities

Our ultrasound measurement equipment includes:

■ Range of ultrasonic transducers (<1 MHz up to

150 MHz);

■ Calibrated hydrophone (up to 20 MHz);

■ 150 MHz square-wave pulser/receiver;

■ 200 MHz negative-spike pulser/receiver;

■ Arbitrary waveform generator (up to 15 MHz);

■ Broadband amplifier (>50 dB up to 400 MHz);

■ High-frequency digitizer (1 GHz — 8-bit);

■ Three-axis automated motion control system;

■ Automated acquisition system;

■ Temperature-controlled immersion baths;

■ Custom specimen fixtures.

The acoustic microscope has been used to

measure properties of bone, cartilage, arterial tissue,

and imaging-enhancing bubbles, to date.

Microfluidic and Particle

Processing Facility

The Polymers Division’s new microfluidic facility

enables entirely new research programs in polymer

chemistry, nanoparticle assembly, and complex fluids

metrology. This capability stems from new fabrication

methods accommodating organic complex fluids,

multilayer architecture integrating functions, and flow

simulations central to device design. A suite of in-situ

chemical and physical measurements are brought to

bear, including Raman spectroscopy, fluorescence,

high-speed image analysis, electronic sensing, and

rheometry. On-chip processing and production

methods comprise controlled radical synthesis, droplet

formation and handling, and particle manipulation

and assembly.

Two technological problems currently under

examination by exploiting these high-throughput

metrologies are polymerization-induced shrinkage of

dental resins and interfacial tension between two liquids.

These applications rely on our capability to measure

two-component flow, droplet chemistry, and droplet-shape

dynamics. In addition, high-frequency on-chip particle

size analysis, using embedded electrodes, is a feature of

a more complex device that integrates particle counting

and analysis, encapsulation, and automatic valve

triggering. These capabilities will enable construction

of complex nanomanufacturing operations.

Small Angle X-ray Scattering Facility

As pattern sizes in the semiconductor electronics

industry decrease to sub-50 nm dimensions, techniques

Figure 6: Phillip Stone using microfluidic interfacial tensiometer.

Figure 7: Modeled CD-SAXS data.

83
Facilities and Capabilities

such as critical dimension-scanning electron

microscopy (CD-SEM) face significant technical

hurdles in quantifying parameters such as Line Edge

Roughness (LER). NIST is evaluating the potential

application of small-angle x-ray scattering (SAXS) as

a metrology tool for both process development and

the production of nanoscale dimension standards.

The Polymers Division is building a laboratory

scale SAXS system to measure with sub-nanometer

resolution, quantitatively and non-destructively, critical

dimensions and feature shape of patterns on production

scale test samples. This system will use a highly

focused molybdenum source with a wavelength where

silicon is transmissive and a two-dimensional detector

for the evaluation of critical dimension, sidewall angle,

and statistical deviations across large areas for dense

high-aspect ratio patterns with sub-50 nm dimensions.

In addition to these capabilities, this facility will include

state-of-the-art SAXS equipment including a copper

source and sample handling equipment for the

measurement of nanostructured materials, fibers,

and polymer solutions.

Organic Electronics Competence

In 2005, the Polymers Division led a successful

5-year competence proposal, “Metrology to Enable

the Realization of Organic Electronics Devices,”

in collaboration with the Ceramics Division, the

Electronics and Electrical Engineering Laboratory

(EEEL), and the Chemical Science and Technology

Laboratory (CSTL). In this project, NIST plans to

develop an integrated and interdisciplinary suite of

metrologies correlating device performance with the

structure, properties, and chemistry of critical materials

and interfaces. NIST will guide the development of

standard test methods and provide the fundamental

measurements needed for the development of materials

and processes to realize the potential of organic electronics.

Several new capabilities have been added at NIST to

achieve these goals, including the design of a controlled

atmosphere glove box train, a programmable, shielded

probe station, and new optical spectroscopy equipment.

These facilities, plus the clean room facility available

in the Advanced Measurement Laboratory, allow

NIST to measure both the structure of materials

and device performance.

MSEL Electron Microscopy Facility

The MSEL Electron Microscopy Facility consists of

two transmission electron microscopes, three scanning

electron microscopes, a specimen preparation laboratory,

and an image analysis/computational laboratory.

Figure 9: Evolution of texture (EBSD maps) in DQSK steel

sheets. Initial conditions (left) and after 10 % uniaxial tensile

strain (right).

Figure 8: Oleksiy Anopchenko (left) and Dean DeLongchamp (right) at Organic Electronic characterization and preparation facilities.

84
Facilities and Capabilities

The JEM3010 TEM resolves the atomic structure

and employs an energy selecting imaging filter (IF) and

X-ray detector (EDS) for analytical characterization of

thin foil specimens. The S-4700-II FE-SEM employs

electron backscattered diffraction/phase identification

(EBSD) and EDS systems to characterize the texture

and composition of materials.

Highlights from the EM Facility for FY2005 include:

■ A new stage compatible with EBSD acquisition will

allow analysis of texture evolution under dynamic

loading (tensile/compressive) conditions (see Figure 9).

■ New forward scatter detectors for the FESEM-EBSD

camera allow simultaneous, multiple mode acquisition

of secondary and backscattered electrons.

Thin Film Deposition Facility

Figure 12: NUMISHEET benchmark sample in the Formability

Station being loaded in plane strain.

Figure 11: The two sources in the combinatorial thin-film

deposition system are each capable of depositing up to six different

materials in a single deposition run.

Figure 10: The combinatorial thin-film deposition system has a

base vacuum in the low 10–8 Torr (10–6 Pa) range and is

equipped with a load-lock for specimen transfer.

The Thin Film and Nanostructure Processing

group of the Metallurgy Division has two high-vacuum,

electron-beam evaporator systems for fabrication

of thin-film and multilayer thin-film specimens.

One system has three independent 15 cc sources

and is used for deposition of thin films and multilayer

thin films of materials from lower melting metals

like aluminum, silver, and copper up to refractory

metals like ruthenium, iridium, and tungsten.

The other system (Figure 10) has two independent

sources (Figure 11), each capable of depositing as many

as six different materials in a single deposition run. With

its two-axis, computer-controlled specimen shutter, it is

used for fabrication of combinatorial-layered as well as

compositionally graded specimens.

Sheet Metal Formability Station

The Metallurgy Division Materials Performance

Group is using the Sheet Metal Formability Station to

develop two new formability tests. The closed-loop

servo-hydraulic system has 500 kN capacity for both

the ram and blank hold-down, and it is capable of

deformation rates up to 30 s–1. A unique and important

capability is that the system is outfitted with an in situ

X-ray diffraction system that makes it possible to

measure the stress in the test specimen at discrete

points during the test. From these data, it is then

possible to produce true-stress-true strain curves for

the multiaxial stress states encountered in forming,

rather than relying on curves derived from unixial tests.

Currently the Materials Performance Group members

are producing materials property data for simulations

of prototype parts in a benchmark forming process

as part of the NUMISHEET 2005 Conference.

85
Facilities and Capabilities

Figure 13: The Kolsky Bar Facility is equipped with a special

pulse-heating capability (not shown) provided by conductive

bearings at the bar supports nearest the sample.

Figure 14: The Magnetic Engineering Research Facility is the

world’s most elaborately instrumented system for magnetic

thin-film deposition and in situ characterization.

Kolsky Bar Facility

The Materials Performance Group of the Metallurgy

Division has developed a Kolsky or Split-Hopkinson bar

facility (Figure 13) to measure the high strain-rate, high

heating-rate constitutive response of metals to provide

data for developing predictive models of these materials

for use in finite element codes or other numerical

analysis techniques. A key feature of the NIST Kolsky

Bar is the ability to rapidly heat samples prior to testing.

Sufficiently rapid heating can short-circuit normal

diffusion-related microstructural changes that would

ordinarily occur under quasi-equilibrium heating.

As a result, the flow stress of rapidly heated materials

can be much different than what is measured under

quasi-equilibrium conditions. There is currently a lack

of such high-temperature non-equilibrium constitutive

data for most metals and alloys of interest. An important

application of industrial interest is high-speed machining,

where rapid temperature increases occur at the

tool/workpiece interface.

Magnetic Engineering Research Facility

The Magnetic Materials Group of the Metallurgy

Division has an elaborate facility specifically designed

for advancing key enabling technologies in the field

of ultrahigh-density data storage. It has many unique

features. Films can be deposited both by the method

preferred in basic research (molecular beam epitaxy)

and by the method of industrial manufacturing (magnetron

sputtering). Numerous in situ characterization techniques

are available including scanning tunneling microscopy,

x-ray photoelectron spectroscopy, Auger electron

spectroscopy, ion scattering spectroscopy, low-energy

electron diffraction, reflection high-energy electron

diffraction, and mass spectrometry. For in situ

magnetic measurements both a superconducting magnet

and an electromagnet are available and are equipped for

magnetoresistance and magneto-optical Kerr effect

measurements.

In Situ Stress Measurement Facility

Figure 15: Optical bench showing components of in situ stress

measurement system.

Figure 16: Close-up of electrochemical cell showing cantilever

electrode.

The Thin Film and Nanostructure Processing group

of the Metallurgy Division has established a Class II

(1 mW) HeNe optical bench dedicated to the in situ

measurement of surface and growth stress during

electrochemical processing using the wafer curvature

86
Facilities and Capabilities

method. Surface stresses on the order of 0.008 N/m

(23 km radius of curvature for 0.1 mm thick borosilicate

glass substrates) can be resolved while the beam is in

solution, sufficient to study the adsorption of molecular

monolayers onto the electrode surface. The curvature

of the substrate is monitored during electrodeposition

by reflecting the laser off of the glass/metal interface,

through a series of mirrors, and onto a position-sensitive

detector, Figures 15 and 16. Surface and internal

stresses for metal films electrodeposited onto the

substrate can be calculated from the deflection of the

beam as a function of time.

Supporting an increasing number of users, there

are several notable developments at the NCNR in:

Sample Preparation and Characterization

Laboratories, Commissioning of a Double

Focusing Triple-Axis Spectrometer, Beginning

installation of the High Intensity Multi-Axis Cold

Neutron Spectrometer (MACS), Data Analysis,

Visualization, and Modeling Software — DAVE II,

and Deployment of Electronics for Large

Detector Arrays.

Sample Preparation and

Characterization Laboratories

The NCNR completed in 2005 the renovation of

three, 7.3 m x 4.9 m (24 ft x 16 ft), laboratories, nearly

doubling the space and equipment available for the

preparation and characterization of samples for

neutron scattering experiments by users and staff.

Users preparing to come to the NCNR for an

experiment can find detailed descriptions of available

laboratory equipment and supplies on the NCNR’s

website at http://www.ncnr.nist.gov/userlab/.

One of the new laboratories is the result of a

bioengineering research partnership between the NCNR

and five universities, with partial funding from the

National Institutes of Health. This Cold Neutrons

for Biology and Biotechnology (CNBT) laboratory

is equipped with a high-volume laminar flow hood

designed for working with acids (e.g., for cleaning

substrates); a 1.44 m3 (51 ft3) chromatography

refrigerator; a large –40 oC freezer; a temperature

controlled, 13 200 rpm microtube centrifuge; as well

as standard wet chemistry equipment for preparing

biology-related samples for diffraction, reflectometry,

and SANS experiments.

One laboratory is dedicated primarily to sample

characterization and includes equipment for dynamic

light scattering, infrared spectroscopy, UV-Visible

Spectrophotometry, gas chromatography, and an optical

microscope with temperature-controlled sample stage,

camera, and attachments for fluorescence measurements.

Figure 17: Yamali Hernandez keeps a watchful eye on the

Langmuir–Blodgett trough in one of the NCNR’s recently

renovated user laboratories.

This laboratory also has a rotary evaporator for purifying

solvents and a computer controlled Langmuir–Blodgett

(LB) trough (see Figure 17) for depositing multi-molecular

layer LB films on solid substrates.

In addition to the above, there are laboratories

with specialized equipment for x-ray diffraction,

solid-state chemistry, surface and interface science,

and general solution chemistry. Also implemented this

year is a bar-coding system for maintaining an accurate

chemical inventory for all the laboratories. Users can

now quickly obtain Materials Safety Data Sheets and

determine the availability, location, and quantity of

chemicals kept in any laboratory.

Commissioning of a Double Focusing

Triple-Axis Spectrometer

The first measurements to characterize the

performance of the new state-of-the-art thermal

neutron triple-axis spectrometer at beam port BT-7 have

been carried out and have met expectations. The new

instrument features the choice of either a Cu(220) or

PG(002) doubly-focusing monochromator, providing a

continuous incident neutron energy range from 5 meV

to 500 meV. The 400 cm2 reflecting area for each

monochromator yields as much as an order-ofmagnitude gain of neutrons onto the sample compared

with other thermal triple-axis spectrometers at the

NCNR. The reactor beam and post monochromatic

beam elements (collimators, slits, and filters) offer a

wide range of choices to optimize the resolution and

intensity of the instrument, with available fluxes well

into the 108 n/cm2/s range.

The sample stage of the instrument includes two

coaxial rotary tables, one for sample rotation and one

87
for the independent rotation of magnetic field coils,

and a computer-controlled sample goniometer and

elevator. Polarized 3He cells are under construction for

the instrument to provide full polarization analysis with

either one of the monochromators and any of the

standard analyzer crystals.

Figure 18: Comparison of the beam intensities (monitor count

rates) for the PG(002) monochromators for the new BT-7

triple-axis spectrometer and the conventional triple-axis

spectrometer at BT-2. The BT-7 monochromator features

vertical focusing that varies with energy, whereas the BT-2

monochromator has a fixed vertical focus optimized for 14.7 meV.

The collimation was open-50’ before and after the monochromator,

respectively, on both instruments. The much larger BT-7

monochromator provides more neutrons that fully illuminate the

sample over a wider range of incident energies. The new double

focusing mode is seen to provide a dramatic gain in neutron

intensity by relaxing the wave vector resolution of the instrument.

Figure 19: Peter Hundertmark and Timothy Pike examine the

ball screw mechanism that will rotate the sample and detector

around the green monochromatic beam transport system, which

they designed.

the instrument is now fully operational as a triple-axis

spectrometer, although the full measurement capability

and flexibility won’t be realized until the new analyzer

system is available.

Installation of the High Intensity

Multi-Axis Cold Neutron Spectrometer

(MACS) Begins

While inelastic neutron scattering in principle can

elucidate atomic-scale dynamics in almost any material,

experiments on the most exciting new materials are

often impractical because high-quality samples are too

small. Arguably, this is not a fundamental limitation of

the technique but due to the lack of flux and detection

efficiency of current instrumentation. The MACS

project aims to increase both factors by an order of

magnitude to enable informative experiments on 1 mg

samples and comprehensive maps of inelastic scattering

when larger samples are available.

MACS is a third generation cold neutron

spectrometer and, as such, presents many fascinating

engineering challenges. In the past year, most of these

have been overcome, and MACS is now in the midst of

a busy manufacturing and installation phase. Led by

Donald Pierce, George Baltic, and Nick Maliszewskyj,

the NCNR facilities engineering group has designed,

procured, painted, and filled more than 50 metric tons

(50 tons) of beamline shielding and beam conditioning

optics for MACS.

The BT-7 spectrometer is designed to be used with

interchangeable customized analyzer/detection systems

supported on air pads. The first new analyzer system

will have a multi-strip PG(002) analyzer array that can

be used in a horizontally focused mode, or in a flat

configuration either with a linear position-sensitive

detector or with conventional Söller collimators. All

options will be under computer control and can be

selected and interchanged by the experimenter without

requiring any mechanical changes or user intervention.

A separate diffraction detector is provided in front of

the analyzer for Bragg peak measurements, and a series

of 13 detectors embedded in the shielding behind the

analyzer will continuously monitor the neutron flux

entering the analyzer system. These detectors can also

be used for measurements of the instantaneous

correlation function, for example, or with a radial

collimator to determine a diffraction pattern over a

limited angular range. This analyzer system is at an

advanced stage of development and is scheduled to be

installed early in 2006. In the interim, a conventional

analyzer system has been installed on air pads so that

Figure 19 shows parts of the monochromatic beam

transport system for MACS along with Timothy Pike

and Peter Hundertmark who designed it. The shielding

penetration consists of an adjustable channel lined by

m = 3.5 super mirrors that will guide a converging

monochromatic beam to the sample position while

minimizing the aperture for fast neutrons and gamma

Facilities and Capabilities

PG Monochromator Performance

88
radiation. The ball screw actuation mechanism

visible in Figure 19 will position the super mirror

channel, the sample table, and the detector system to

receive a monochromatic beam with energies varying

from 2.5 meV to 20 meV. Anticipating high-field

superconducting magnet systems, all materials within

750 mm of the sample position are non-magnetic.

Figure 21: Data in DAVE II can be imported, manipulated, and

displayed in easily customizable yet sophisticated plots.

Figure 20: Stephen Smee (left) and Gregg Scharffstein with the

MACS monochromating system. (The monochromator is between

and behind them on the bench.) Not shown are Joe Orndorff and

Randy Hammond who complete the team from the Instrument

Development Group at Johns Hopkins University that designed

and assembled the system.

Apart from the intense NCNR cold neutron source,

the key to enhancing flux on sample is the monochromating

system, which will focus the beam from 1400 cm2 to

8 cm2. It consists of a variable beam aperture to

minimize background and to control wave vector

resolution, a four-position radial collimation system to

control energy resolution, and a translating, doubly

focusing graphite monochromator. These will inhabit a

helium-filled cask to reduce air scattering and pack

shielding close to the complex beamline elements.

Figure 20 shows these items during tests by the

Instrument Development Group at Johns Hopkins

University where they were designed and assembled.

The monochromating system now stands ready for

neutrons at the NCNR.

All the equipment described above was installed in

the beamline in the late summer and early fall of 2005.

Sample stage and detector system installation will start

in the fall so MACS can be ready for commissioning

experiments and friendly users in the spring of 2006.

While MACS will eventually become a Center for

High Resolution Neutron Scattering (CHRNS) user

facility for a broad range of science spanning

condensed matter physics, chemistry, and biology,

principal investigators Collin Broholm and Jeff Lynn

are particularly excited about the new capabilities that

MACS will provide for research in quantum magnetism

and superconductivity.

Data Analysis, Visualization, and

Modeling Software — DAVE II

Significant development activity in the Data

Analysis and Visualization Environment (DAVE) team

over the last year has resulted in a brand new look and

feel for DAVE. DAVE II brings a new paradigm to

data visualization and analysis via a novel data-centric

user-interface. The infrastructure includes a project

manager, data manager, visualization manager,

user-interface, visualization modules, and mechanisms

for easy integration of additional applications as they

become available. All of this has been designed to

help the user get the most from his/her neutron data.

The project manager concept promises to greatly

simplify the user experience because it allows a user

to save a complete session (plots, reduction steps, data

operations, etc.) and restore it at a later time. Moreover

there is much greater flexibility in DAVE II with the

implementation of a document/view architecture.

Facilities and Capabilities

89
Figure 22: Preamplifier-Amplifier-Discriminator 2 (PAD2)

system components.

Multiple datasets can be loaded simultaneously and

multiple views (even of the same dataset) can be

created (line, contour, image, surface and volume

renderings using OpenGL, the industry standard for

high performance graphics). The visualizations are

feature-rich allowing simple creation of sophisticated

plots resulting in publication-quality output. Undo/redo

functionality is implemented allowing scientists to

perform what-if types of analyses with ease, thus

enhancing the user experience. In the initial release,

support for ASCII and the current DAVE format are

provided. Operations to perform specific data analysis

tasks are being implemented, and the initial data

reduction functionality is identical to that of the

current version of DAVE.

Deployment of Electronics for

Large Detector Arrays

As the number of detectors on an instrument

increases and the detectors themselves are buried in

locations that are not readily accessible, the task of

tuning the discriminator thresholds and periodically

inspecting the banks for quality control becomes a

major undertaking. The Preamplifier-AmplifierDiscriminator 2 (PAD2) system (Figure 22), developed

by the NCNR’s Jeff Ziegler and Nick Maliszewskyj, is

a state-of-the art solution to the needs of instruments

with a large number of detectors. This system

consists of compact front-end modules combining the

functions of preamplifier, amplifier, and discriminator;

concentrator boards that multiplex control and

data signals for eight front-end units; and a system

controller that can set the gain and signal threshholds

for a collection of up to 2048 individual detectors.

The differential signal levels employed allow for longer

cable runs and greatly improved noise rejection over

the existing TTL solutions. Live quality control is

now possible thanks to in situ pulse height analysis.

A single point of control makes it possible to tune the

discriminator settings for detectors behind shielding

or in vacuo. Taken in combination, the capabilities

of this new system are groundbreaking and surpass

anything available commercially. The system was

successfully deployed on the 32-detector BT-1 powder

diffractometer and the HFBS backscattering

spectrometer in 2005.

Facilities and Capabilities

90
Databases

Databases

SRD 31: Phase Equilibria Data

T.A. Vanderah

The Phase Equilibria Data project is a joint effort

of NIST and the American Ceramic Society (ACerS).

Working together, NIST and ACerS have published

more than 20,000 diagrams depicting graphical

representations of the regions of distinct chemical

and structural behavior of materials in thermodynamic

equilibrium. The diagrams are distributed by ACerS in

traditional printed volumes and in a modern searchable

PC database system. Phase Equilibria Diagrams,

Volume XIV, Oxides, completed this year and unveiled

at the annual ACerS meeting in April, contains figures

numbered from 10841 to 11637 and covers oxide

systems originally published in the literature between

1980 and 2004 and not previously included in the series.

SRD 83: NIST Structural Database

V.L. Karen

The NIST Structural Database (NSD) contains

evaluated crystallographic data (lattice parameters,

atomic positions, and symmetry classifications) for

metallic crystalline substances, including alloys,

intermetallics, and minerals. The data set is licensed

for use in both personal computers and instrumentation.

This year’s updates doubled the accessible data to more

than 16,000 records.

SRD 84: FIZ–NIST Inorganic Crystal

Structure Database

V.L. Karen

The Inorganic Crystal Structure Database (ICSD) is

produced cooperatively by the Fachinformationszentrum

Karlsruhe (FIZ) and the National Institute of Standards

and Technology (NIST). The ICSD is a comprehensive

collection of crystal structure data for inorganic

compounds. In addition to the full three-dimensional

crystal structure data, chemical composition, reduced

cell symmetry data, and bibliographic information, the

ICSD includes enhanced features for the characterization

of materials based on lattice and chemistry search modules,

3-dimensional visualization, and powder pattern simulation

of inorganic structures. Two updates this year added

approximately 2000 entries and brought the total

number of entries to more than 70,000.

SRMs

The Ceramics Division is the world’s leading producer

of x-ray Certified Reference Materials. Last year,

determination of the amorphous content of NIST

Standard Reference Material® (SRM) 676 (the primary

internal standard for quantitative analysis by x-ray

diffraction) launched a recertification effort for a suite

of additional SRMs also utilized in quantitative analysis.

Recertification now has been completed for SRMs

656 (two mixtures of α and β phases of silicon nitride),

674b (oxide powders for internal intensity standards),

and 1878a (respirable quartz) and 1879a (respirable

cristobalite) for quantitative analysis in occupational

safety and health applications.

91
Recommended Practice Guides

Recommended Practice Guides

SP960-1: Particle Size Characterization

Ajit Jillavenkatesa, Stanley J. Dapkunas,

and Lin-Sien H. Lum

The consequences of improper particle size analyses

include poor product quality, high rejection rates, and

economic losses. Hence, the ceramic manufacturing

industry and the broad range of applications utilizing

powders have a strong and active interest in the

metrology required for accurately determining the

distribution of particle sizes in a powder. This Guide

describes the techniques most commonly used for

measurement of particle size and size distribution,

including sieving, gravitational sedimentation, laser

light diffraction, and microscopy-based methods.

The capabilities and limitations of these techniques

are examined together with discussions of the

general principles on which the techniques are based.

The Guide includes discussions of the fundamental

issues in representative sampling, the procedures and

precautions generally followed for sample preparation

and analysis, and the assessment of sources of error, bias,

and other potential variations in the measurement results.

SP960-2: The Fundamentals of

Neutron Powder Diffraction

John R.D. Copley

This Recommended Practice Guide introduces the

reader to neutron powder diffraction, a powerful

technique that complements x-ray diffraction as a

means to determine crystal structures. The principal

differences between the x-ray and neutron techniques

are discussed, and several examples of applications to

materials of industrial interest are described.

SP960-3: The Use of Nomenclature in

Dispersion Science and Technology

Vincent A. Hackley and Chiara F. Ferraris

Measurements and standards enhance reliability in

manufacturing by providing a common basis for

quantifying and comparing material properties during

each phase of the manufacturing process, from raw

materials to the finished product. Underlying this ability,

and essential to its success, is the use of a well-defined,

widely accepted, and uniformly applied nomenclature.

An established nomenclature significantly enhances

the accuracy and efficiency of the descriptions of

experimental methods and instrumentation, facilitates

the sharing of technical ideas and concepts, and

provides a sound basis on which to standardize

measurement methods and data reporting practices.

This Guide was prepared as a resource for researchers,

engineers, and students working on dispersion-based

applications. While emphasizing commonly encountered

terms, every effort was made to maintain a degree of

uniformity with existing standards and conventions to

provide a consistent framework for improved technical

communication. The result was a comprehensive

glossary of terms related to the central issues in

dispersion science and technology.

SP960-4: Installing, Maintaining, and

Verifying Your Charpy Impact Machine

Daniel P. Vigliotti, Thomas A. Siewert, and

Chris N. McCowan

The quality of the data developed by pendulum impact

machines depends on how well the machines are

installed, maintained, and verified. This is the reason

that ASTM Standard E 23 Standard Test Methods for

Notched Bar Impact Testing of Metallic Materials

specifies annual direct and indirect verification tests.

Each year, NIST provides reference specimens for

indirect verification of over 1000 machines around the

world. From evaluation of the absorbed energies and

the fractured specimens, we attempt to deduce the

origin of energies that are outside the ranges permitted

by Standard E 23 and report these observations back

to the machine owners. This Recommended Practice

Guide summarizes the bases for these observations

and, hopefully, will allow machines to be maintained

at higher levels of accuracy. In addition, we provide

details of the NIST verification program procedures

and the production of the specimens.

SP960-5: Rockwell Hardness

Measurement of Metallic Materials

Samuel R. Low

The Rockwell hardness test continues to be applied as

a tool for assessing the properties of a product while

the tolerances on the acceptable material hardness have

become tighter and tighter. Adhering to “good practice”

procedures when performing Rockwell hardness

measurements and calibrations is a beneficial step to

reducing measurement errors. The purpose of this

Guide is to explain the causes of variability in Rockwell

hardness test results and to supplement the information

given in test method standards with good practice

recommendations. Although this Guide is directed

more towards the users of Rockwell hardness

having the greatest concern for accuracy in their

measurements, much of the information given is also

applicable for users that only require test results to be

within wide tolerance bands, where high accuracy is

not as critical.

92
Recommended Practice Guides

SP 960-7: Capacitance Cell

Measurement of the Out-of-Plane

Expansion of Thin Films

Chad Snyder and Frederick Mopsik

This Guide describes the construction, use, and data

analysis methods for a capacitance-based metrology

for robust and highly accurate measurement of the

out-of-plane expansion of films between 2 μm and

1 cm in thickness. This metrology was developed

because the coefficient of thermal expansion (CTE)

continues to be a critical design parameter for the

semiconductor electronics industry and is increasingly

important to nanotechnology applications, as it is

needed to estimate the stresses generated by thermal

differentials. In response to a lack of robust methods

for measuring the out-of-plane expansion of thin

polymer films in the thickness range between the

capabilities of typical thermomechanical analyzers

(TMA) and x-ray reflectometers, NIST developed this

capacitance-based measurement technique. This guide

closely examines the sources of error associated with

the metrology, and the descriptions are sufficiently

detailed that the reader should be able to reproduce

the metrology and achieve its typical measurement

reproducibility upon thermal cycling of ±2 μm/m.

SP960-8: Test Procedures for

Developing Solder Data

Thomas A. Siewert and Carol A. Handwerker

This publication documents standardized test

procedures that can produce valid and reproducible

mechanical-property data for lead-free solders.

Such data speeds the application of lead-free solders

in high-volume, automated production of electronic

assemblies, especially when current production

expectations combine high levels of quality with the

lowest cost. Use of standardized procedures facilitates

the comparison of data between laboratories and

permits the combination of data from different

sources into a single, comprehensive database.

Most dimensions and temperatures are listed

without tolerances. Unless otherwise specified, use

± 5 % on dimensions, times, and pressures, and ± 3 °C

for temperatures.

Many of the procedures assume some skill in

the arts of specimen production and testing. Various

textbooks and industry brochures (some listed in the

Bibliography) can provide background information

on these skills and any hazards associated with

these procedures.

SP960-9: Surface Engineering

Measurement Standards for

Inorganic Materials

Stanley J. Dapkunas

Applications as diverse as medical implants and gas

turbines have been the beneficiaries of the substantial

accomplishments in the surface engineering of

materials. Characterizations of surfaces and

measurements of surface properties have become

vital to systems design, maintenance, and analysis

and, hence, to the commerce that depends on those

systems. This Guide identifies pertinent properties

and characteristics of engineered surfaces and

provides descriptions of the most prevalent standard

test methods applied to the measurement or assessment

of those characteristics. The type of data produced

using each method is described as well as the specimen

requirements, the intended application, and the limits

of the method. An extensive cross index of key

words allows identification of standards by method,

property, or type of material.

SP960-10: X-Ray Topography

David R. Black and Gabrielle G. Long

The study of the interrelationships among processing,

structure, and properties is fundamental to the field of

materials science and engineering. The important role

of microstructure in these relations has driven the

development of a wide variety of x-ray based

characterization techniques, including the technique

of x-ray topography (XRT). This powerful tool

provides a nondestructive means of imaging the defect

microstructure of crystals for defects in the size

range of micrometers to centimeters. This technique,

however, has been underutilized in the United States.

Consequently, this guide was developed to make the

technique more accessible to materials scientists who

can benefit from the rich variety of microstructural

information it offers. The basic principles and practical

aspects of topography are discussed, and numerous

examples are presented to illustrate the diversity of

applications that can benefit from this technique.

SP960-11: Data Evaluation Theory

and Practice for Materials Properties

Ronald G. Munro

Technology thrives on data, and advances in science

are propelled by advances in data. It follows that the

quality of the available data is a concern of central

importance to all of science and engineering. The

process by which collections of data are assessed with

respect to reliability, completeness, and consistency is

93
Recommended Practice Guides

known as data evaluation. This guide addresses data

evaluation for materials properties as a scientific

discipline that evolves from the formal underpinnings

of materials metrology. After carefully establishing a

theoretical foundation, an extensive collection of

examples is used to examine, in succession, the issues

of accessibility, reproducibility, consistency, and

predictability. Distinctions are made among definitive

relations, correlations, derived and semi-empirical

relations, heuristic theories, and value estimates.

Special subtopics include the use of properties as

parameters in models, the interpretation of ad hoc

parameters, and the treatments of procedural properties,

response dependent properties, and system dependent

data. The principles and practices set forth in this

work serve as a guide to data evaluation across many

disciplines, wherever considerations of numeric

property data are crucial to the interpretation and

application of quantitative observations.

SP 960-13: Pore Characterization in

Low-k Dielectric Films Using X-ray

Reflectivity: X-ray Porosimetry

Christopher L. Soles, Hae-Jeong Lee,

Eric K. Lin, and Wen-li Wu

This recommended practice guide describes the

equipment and methodology for quantifying the average

pore size, pore size distribution, and wall density in thin

films where the sample mass is prohibitively small for

traditional porosimetry measurements. This method

was initially developed for nanoporous low-dielectricconstant thin films needed for the further advancement

of semiconductor devices where in-house structural

characterization methods are needed to evaluate

candidate materials and processing methods, but can

be easily generalized to other nanoporous thin films.

The developed porosimetry method uses X-ray

reflectivity to measure the density of the film while

gradually increasing or decreasing of the partial

pressure of condensate vapors such as toluene in

the presence of the film. The change in film density

can be directly related to the amount of adsorbed

condensate, and thus porosity, if the density of the

condensed fluid is known. Monitoring the amount

of adsorbed condensate as a function of the partial

pressure defines a physisorption isotherm, the

basic starting point for any number of analytical

interpretations. The X-ray Porosimetry Recommended

Practice Guide provides detailed information so that

this knowledge and expertise may be transferred to

industrial research and university laboratories. It is

hoped that X-ray porosimetry will be widely adopted

for the evaluation and characterization of newly

developed nanoporous thin-film materials.

94
Ceramics Division FY04 Annual Report Publication List

95
vi