bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards 3D lattice reconstruction with the Position Sensitive Atom Probe
Authors: Warren PJ , Cerezo A , Smith GDW
Published: July 2020

3-dimensional atom probe (3DAP) analysis enables 3D reconstruction of the chemical variations inside materials with near atomic resolution. This technique has enabled important insights into the phase chemistry and microstructure of a range of complex engineering materials. Although individual planes can be resolved when analysing in a direction close to a low-index pole, the spatial resolution of this technique has not been sufficient for reconstruction of all the original lattice positions. The spatial resolution is thought to be fundamentally limited by small lateral displacements of the atom on the surface of the specimen during the field evaporation process due primarily to interactions with the neighbouring surface atoms. It has therefore been considered that it will be impossible to correctly reconstruct the crystal lattice from 3DAP data. Recently, we have found that a 3DAP reconstruction of a region near a grain boundary in pure tungsten (an element renown for its good imaging and evaporation behaviour) revealed several different sets of crystallographic planes visible at angles up to 45° from the direction of analysis.
Digital Field Ion Microscopy
Authors: Sijbrandij S J , Russell K F , Thomson R C , Miller M K
Published: July 2020

Due to environmental concerns, there is a trend to avoid the use of chemicals needed to develop negatives and to process photographic paper, and to use digital technologies instead. Digital technology also offers the advantages that it is convenient, as it enables quick access to the endresult, allows image storage and processing on computer, allows rapid hard copy output, and simplifies electronic publishing. Recently significant improvements have been made to the performance and cost of camera-sensors and printers. In this paper, field ion images recorded with two digital cameras of different resolution are compared to images recorded on standard 35 mm negative film. It should be noted that field ion images exhibit low light intensity and high contrast.

Field ion images were recorded from a standard microchannel plate and a phosphor screen and had acceptance angles of ∼60°.
Atom Probe Field Ion Microscopy of Poly Synthetically Twinned Titanium Aluminide
Authors: Larson D J , Miller M K , Inui H , Yamaguchi M
Published: July 2020

Two phase γ-based TiAl alloys are attractive for structural applications at high temperatures because they possess good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. The microstructures of these alloys consist of plates of the near equiatomic γ phase (L10-ordered structure) and the Ti3Al α2 phase (D019-ordered structure). It is of great interest to study the details of the lamellar α2+γ microstructure because the interface stability is the key to providing a usable high temperature material.

Polysynthetically twinned (PST) TiAl crystals have been developed in order to systematically study the lamellar microstructure. These PST materials contain no high angle grain boundaries and have an single set of aligned lamellae of a α2 and γ phases, as shown in Fig. 1. Therefore, PST samples facilitate the study of the dependence of mechanical properties on lamellar structure by providing a known, consistent set of aligned lamellae.
Atom Probe Studies of the Nanochemistry of Steels
Authors: Smith GDW , Cerezo A , Godfrey TJ , Wilde J , Venker FM
Published: July 2020

Steels represent by far the most widely used class of engineering alloys, and comprise almost 95% of total world metal production. Yet despite their familiarity and ubiquitous distribution, many fundamental questions remain unanswered regarding the nature of the solid state chemical reactions occurring during the heat treatment of steels, the mechanisms by which alloy additions affect the kinetics of these processes, and the role of trace impurities on properties.

The difficulties involved in studying such processes experimentally arise from two main sources. Firstly, the effects involved are often on an extremely fine scale. Secondly, one of the key elements involved is carbon, which is extremely difficult to study by conventional microanalytical techniques.

Remarkable progress has been achieved in these areas through the application of the atom probe method. Much of this work has been reviewed in a recent monograph by Miller et al.
The Role of Atom Probe in the Study of Nickel Base Superalloys
Authors: Blavette D
Published: July 2020

One of the advantages of Atom Probe Field Ion Microscopy (APFIM) as compared to other nanoanalytical instruments is its very high spatial resolution and its quantitativity in composition measurement. A few tenths of a nanometer at the specimen surface as well as an ultimate depth resolution of one atomic resolution can routinely be attained. Among the numerous improvements brought about since its early developments in the seventies, the advent of three-dimensional atomprobes (see papers of G.D.W Smith and A. Cerezo, this issue) has been probably one of the most important breakthroughs, the Tomographic Atom Probe (TAP) being the French prototype [1]. As shown in a recent publication, this instrument is able to map out both composition and order 3D fields on a scale close to that of the unit cell [2], In this contribution, we shall focus on the application of 1D and 3D atom-probes to the study of nickel base superalloys.
The Atom-Probe Field Ion Microscope: Applications in Surface M Science
Authors: Kellogg G L
Published: July 2020

The ability to locate an individual atom on a surface, remove it in a controlled fashion, and determine its chemical identity makes the atom-probe field-ion microscope an extremely powerful tool for the analysis of solid surfaces. By itself, the field ion microscope has contributed significantly to our understanding of surface atomic structure, single-atom surface diffusion, and the detailed interactions that occur between atoms and defects on surfaces.1 When used in combination with the atom-probe mass spectrometer there have been several additional areas within the traditional definition of "surface science" where the chemical identification capability of the atom probe has led to new insights. In this paper these applications are reviewed focusing on two specific areas: surface segregation in intermetallic alloys and chemical reactions on metal surfaces.

The equilibrium distribution of component species in the near surface region of solid solution alloy may be different from the distribution in the bulk.
APFIM Studies of Interfaces: Structure and Composition
Authors: Hans Nordén
Published: July 2020

The distribution of small amounts of alloying elements or impurities to interfaces can have a major influence on the properties of a material and the atom probe field ion microscope technique is well suited for the study of such segregation effects, where structural and compositional changes often take place over regions only a few nanometers wide.

Many features of the atom probe technique make it very useful in studies of interfaces:

i) high spatial resolution, about lnm laterally and 0.2 nm in depth ii) equal sensitivity for all elements, including the lightest iii) no specimen contamination, surface artifacts from the specimen preparation are removed by field evaporation, iv) low temperature operation, negligible diffusion during analysis

A ncessary prerequisite for any systematic analysis is the ability to prepare suitable specimens. The volume accessible for analysis by APFIM is orders of magnitude smaller than a typical grain size, so a specimen preparation technique was developed that could bring features of interest sufficiently close to the apex (see Fig. la).
Compositional Imaging Rediscovered: What‚s New/What‚S Not?
Authors: Isaacson M S
Published: July 2020

The last several decades have seen an explosion in the number of experimental techniques being developed to characterize materials. In particular, there has been exponential growth in the coupling of microscopic methods with conventional spectroscopic characterization tools. This has been due mainly to the renaissance in microscopy over the last quarter century and the advent of significant computational power “on a bench”.

Compositional imaging is just a new term for what was over a half century ago called “Chemical Microscopy”. Although then the term referred to optical microscopy, today the notion of compositional imaging refers to a method by which we can correlate chemical or elemental composition with a microscopic image feature.

Because many of these microcharacterization methods have developed from many different disciplines, the “local” language used often appears to be untranslatable from one technique to the next without considerable pain and difficulty.
Direct Imaging of Trace Elements, Isotopes, and Molecules Using Mass Spectrometry
Authors: Linton Richard W
Published: July 2020

Secondary ion mass spectrometry (SIMS) is based upon the energetic ion bombardment of surfaces resulting in in the emission of sputtered particles, including both atomic and molecular ions. The use of mass spectrometric detection provides a highly versatile and sensitive tool for surface and thin film microanalysis. The scope of the technique includes a diversity of analysis modes including:

1. Elemental Depth Profiling (dynamic SIMS), 2. Laterally Resolved Imaging (ion microprobe or ion microscope analysis), 3. Image Depth Profiling (combination of modes 1 and 2 providing 3-D images), 4. Molecular Monolayer Analysis and Imaging (static SIMS), 5. Sputtered Neutral Mass Spectrometry (post-ionization).

Much of the early work in dynamic SIMS centered on depth profiling and imaging techniques, with an emphasis on applications to electronic materials. SIMS has made extensive contributions to semiconductor materials science since the 1960's, including the development of new devices and processes, and in failure analysis.
Strategies For Combining Elemental Distribution Data Derived From Multiple Images and Samples
Authors: Cantino Marie E , Eichen Joseph G
Published: July 2020

Data from digital electron probe x-ray microanalysis (EPXMA) images can be used to generate high resolution profiles of Ca binding within sarcomeres of vertebrate striated muscle. While ratios of elemental peak to bremstrahlung at each point (Hall method) have been used in many studies to allow comparison of data taken from different samples, this procedure has limitations for our application. A different normalization procedure is described here which provides a means of assessing variation among elemental and bremstrahlung profiles obtained from different images and samples.

Freeze dried cryosections of chemically skinned frog or rabbit skeletal muscle were prepared as previously described. Digital EPXMA images were collected for 24 to 36 hours using a Zeiss EM910 STEM and an Oxford ExL2 microanalysis system. Calcium and bremstrahlung counts were summed within one pixel wide masks placed at successive positions along each half sarcomere, as previously described, using an automated routine in IPLAB on a Power Mac 7100.
Quantitative Composition and Thickness Mapping With High Spatial Resolution By XEDS In a 300kv FEG-AEM
Authors: Watanabe M , Williams D B
Published: July 2020

Since the first demonstration by Cosslett and Duncumb, X-ray mapping by an electron probe microanalyzer (EPMA) has become a most popular approach in microanalysis because elemental distributions of constituents in a bulk sample can be displayed visually. The major disadvantage of EPMA mapping is poor spatial resolution (∼ 1 μm). The spatial resolution of X-ray microanalysis can be improved to a few nanometers using electron transparent thin-specimens in the analytical electron microscope (AEM). However, X-ray count rates from thin specimens are strictly limited because of the improved spatial resolution (i.e. smaller interaction volume) and the poor collection efficiency of X-ray. To obtain reasonable counts for accurate quantification in the AEM, extraordinarily long mapping times are required. Therefore, quantitative X-ray mapping is rarely attempted in the AEM. However, these limitations can be overcome by use of intermediate-volt age instruments combined with field-emission guns to increase the beam current-density, careful stage design to maximize the X-ray collection efficiency and the peak-to-background ratio, and ultrahigh vacuum system to reduce contamination.
X-Ray Microscopy Analysis of the Morphology of Poly(Ethylene Terephthalate)/Vectra Blends Produced by Mechanical Alloying
Authors: Smith A P , Bai C , Ade H , Spontak R J , Balik C M , Koch C C , Saw C K
Published: July 2020

The intimate blending of two incompatible polymeric materials constitutes one of the most important fields of study in polymer science. A vast arsenal of techniques, ranging from copolymerization to melt-blending, has been assembled to mix intrinsically immiscible polymers and optimize the physical properties of the resultant system. For some systems, however, even established techniques cannot produce useable blends. To overcome this limitation, non-equilibrium mechanical alloying (high-energy ball milling of two or more dissimilar powders) has been employed to produce blends of poly(ethylene terephthalate) (PET) and Vectra (73/27 oxybenzoate/oxynaphthoate). Characterization of these blends by TEM is confounded by the absence of a preferential staining agent, in which case Scanning Transmission X-ray Microscopy (STXM) provides a valuable alternative in examining the morphology and chemistry of these blends.

The x-ray microscope utilizes a diffraction element called a zone plate to focus soft x-rays into a microprobe. A thin section of sample is placed in this microprobe, and the transmitted photon intensity measured.
Compositional Characterization of an O-N-O Layer in a Dram Using FE-TEM and EDS Elemental Mapping
Authors: Kawasaki M , Oikawa T , Ibe K , Park K H , Shiojiri M , Kersker M
Published: July 2020

An O-N-O layer within a DRAM is designed to be an insulator between a single-crystal silicon substrate and a poly-crystalline silicon gate. The nominal structure of the layer is SiO2-Si3N4-SiO2. A small amount of phosphorus is doped in the poly-crystalline silicon gate to improve the electrical characteristics of the device. Transmission Electron Microscopy (TEM) was first used to view the micro structure in the layer. A bright field image gave clear contrast in the O-N-O layer, however, TEM images do not provide direct information about the elemental distribution. In this study X-ray elemental mapping was thus used to show this distribution.

The specimen was cut from a 16M-DRAM device and thinned using the cross-section ion milling method. The O-N-O layer was examined using a JEM-201 OF FE-(S)TEM equipped with a JEOL UTW-EDS detector. Fig. 1 shows a high resolution TEM image of the O-N-O layer.
Industrial and Clinical Applications of Infrared Spectroscopic Imaging Using Focal-Plane Arrays
Authors: Kidder Linda H , Levin Ira W , Neil Lewis E
Published: July 2020

Conventional Fourier transform infrared (FTIR) spectroscopy is a workhorse analytical technique providing quantitative and qualitative information on a vast array of materials, ranging from semiconductors to biological samples. By coupling a Michelson interferometer and infrared (IR) microscope to an IR sensitive focal-plane array detector, we have added an imaging component to the existing analytical capabilities of FTIR spectroscopy. This additional capability makes it possible to image the distribution of subtle structural and compositional changes reflected in the infrared spectrum within heterogeneous materials. As such, it is an extremely powerful analytical tool which is currently employed in a variety of basic research and industrial applications. Similarly the utility of FTIR spectroscopy for the investigation of biological materials can be greatly extended by recording spectroscopic imaging data sets instead of single FTIR spectra. This spectroscopic imaging capability, especially when combined with microscopy, ensures that information concerning spatial variations in the system’s biochemistry, as well as its cellular morphology, is maintained.
Compositional Mapping by Scanning Electron Microscopy With Energy Dispersive X-Ray Spectrometry: Recognizing Facts and Artifacts
Authors: Newbury Dale E , Bright David S
Published: July 2020

Compositional mapping with energy dispersive x-ray spectrometry (EDS) in the scanning electron microscope (SEM) is one of the most widely used techniques for elemental imaging of microstructures. SEM/EDS maps are usually qualitative presentations of elemental distributions in x-y space. In older implementations of mapping, the x-ray intensity from a single spectral region of interest (ROI) above a threshold was recorded on film as a white “dot” during analog scanning. With modem digital control and data recording, x-ray intensities from many ROIs can be recorded in parallel and true counts stored in memory. For display purposes a gray level or color value is used to represent the stored x-ray intensity at each pixel. For major constituents (arbitrarily, major >10%), it is generally possible to make valid, robust comparisons between regions within an individual compositional map, but comparisons may be problematic among several maps of different constituents within the same field of view, depending on the sophistication of the mapping software.
The Next Generation of EDS: Microcalorimeter Eds With 3 eV Energy Resolution
Authors: Martinis John M , Irwin K D , Wollman D A , Hilton G C , Dulcie L L , Bergren N F
Published: July 2020

Semiconductor energy dispersive spectrometers (EDS), the most commonly used detectors for x-ray microanalysis, have matured to the point that significant improvement in energy resolution is not expected in the future. We believe a revolutionary advance in x-ray microanalysis will occur in the next few years due to the development of new x-ray spectrometers based on microcalorimeters. Energy resolution comparable with wavelength dispersive spectrometers, 3 eV to 10 eV, has already been achieved; future detectors may reach a fundamental limit as low as 0.5 eV to 1 eV.

In a microcalorimeter, the energy of an x-ray is converted into heat, and a measurement of the temperature rise of the detector gives the deposited photon energy. Our microcalorimeter detector consists of a superconducting transition edge thermometer cooled to an operating temperature of 100 mK by a compact adiabatic demagnetization refrigerator, a read-out SQUID (Superconducting Quantum Interference Device) preamplifier followed by pulse-shaping amplifier and pile-up rejection circuitry, and a multi-channel analyzer with real-time computer interface.
Application of X-Ray Optics to Energy Dispersive Spectroscopy
Authors: McCarthy J J , McMillan D J
Published: July 2020

The application of x-ray optics for focusing x-rays into high intensity spots or for collimation of x-ray beams has been reported by several authors. Example applications for x-ray optics include microfluorescence, microdiffraction, tomography and lithography, and WDS. Kirkland et al. pointed out that the use of an optic, in a collimating configuration could provide enhanced detection sensitivity in wavelength dispersive spectroscopy. In these proceedings last year, Agnello et al. presented data from a new WDS device specifically designed to use a grazing incidence collimating x-ray optic that confirmed and extended the work of Kirkland.

A few studies have appeared reporting the use X-ray optics in applications using EDS. Focusing x-ray optics have been used on both the excitation and detection side of EDS systems. In a series of papers, Carpenter and his collaborators describe an x-ray microprobe which uses capillary optics to provide an intense convergent beam of x-rays from a microfocus x-ray tube to excite the sample for x-ray microfluorescence studies. Wollman et al.
X-Ray Energy Dispersive Spectroscopy in the Environmental Scanning Electron Microscope
Authors: Mansfield John F , Pennington Brett L
Published: July 2020

The environmental scanning electron microscope (Environmental SEM) has proved to be a powerful tool in both materials science and the life sciences. Full characterization of materials in the environmental SEM often requires chemical analysis by X-ray energy dispersive spectroscopy (XEDS). However, the spatial resolution of the XEDS signal can be severely degraded by the gaseous environment in the sample chamber. At an operating pressure of 5Torr a significant fraction of the primary electron beam is scattered after it passes through the final pressure limiting aperture and before it strikes the sample. Bolon and Griffin have both published data that illustrates this effect very well. Bolon revealed that 45% of the primary electron beam was scattered by more than 25 μm in an Environmental SEM operating at an accelerating voltage of 30kV, with a water vapor pressure of 3Torr and a working distance of 15mm.
The Analysis of Particles With Energy Dispersive X-Ray Spectroscopy (EDS)
Authors: Small J A , Armstrong J A , Bright D S , Thorne B B
Published: July 2020

The addition of the Si-Li detector to the electron probe, the scanning electron microscope, and more recently the transmission electron microscope (resulting in the analytical electron microscope) has made it possible to obtain elemental analysis on individual “particles” with dimensions less than 1 nm using EDS. Although some initial particle studies on micrometer-sized particles were done on the electron probe using wavelength dispersive spectrometers, WDS, the variability and complexity of many particle compositions coupled with the high currents necessary for WDS made elemental analysis of particles by WDS difficult at best. In addition, the use of multiple spectrometers, each with a different view of the particle and therefore different particle geometry as shown in Fig. 1, limited the quantitative capabilities of the technique. With the introduction of the Si-Li detector, there was only one spectrometer with a single geometry resulting in the development of various procedures for obtaining quantitative elemental analysis of the individual particles.
Unprecedented Performance Improvement For Thermoelectrically Cooled Si(Li) Detector for EDS
Authors: Barkan S , Ihrig K F , Abott M B
Published: July 2020

High performance Si(Li) detectors for EDS applications must be cooled in order to eliminate excess leakage current and to reduce noise as a result of thermal excitation. The most common cooling method is the use of liquid nitrogen (LN), which has been commonly used during the last four decades. The LN method is relatively simple, however, it has some disadvantages such as: requiring a large dewar for storing the LN, the necessity of refilling it with LN, as well as some hazardous handling issues.

Several years ago, Kevex introduced a new no-LN x-ray detector, the SuperDry, offering the customer a solution to the previously mentioned cooling problems. The SuperDry uses a thermoelectric device, a Peltier solid-state refrigerator, without any moving parts. The SuperDry covers all the disadvantages of the LN method, however, the temperature achieved has not reached the same low level as the LN products.
A New EDS Equipment (GEM Detector With Superatw Window) and a Correction for Si-Contamination Improve the Quantitative Electron Probe Micro Analysis of Biological Cryosections
Authors: Schultz M , Rudolf F , Wendt-Gallitelli MF
Published: July 2020

Function dependent changes in the intracellular (i.c.) concentrations of calcium and sodium play a crucial role in the regulation of biological processes such as contraction of heart muscle. However, accurate measurements of both elements are difficult since in i.e. compartments they are present in low concentrations, hence the Ca and Na peaks show small count rates and small peak to continuum ratios. The accurate quantification of Ca and Na is rendered even more difficult by the partially overlap of the NaK with CuL peak and CaKα with KKβ peak. In some cases electrophysiologist substitute in the experiments K+ with Cs+ or the pathologist is interested in the storage of mercury. For analysis of such elements (Cs, Hg) with higher atomic number the stopping power of the EDS crystal play an important role for system sensitivity. Quantitative analysis of thin biological cryosections with the continuum method must be corrected for influence of X-rays emit from holder, supporting film and grid.
Problem Elements and Spectrometry Problems in X-Ray Microanalysis: the Black Holes of the Periodic Table
Authors: Armstrong John T
Published: July 2020

Few quantitative analysis techniques attempt as large an extrapolation between the compositions of standards and samples than is attempted in electron microbeam x-ray emission analysis. In-situ x-ray microanalysis can be performed for essentially all elements in the periodic table in complex matricies that may contain, in extreme cases, thirty or more detectable elements. Analyses are attempted for the same elements, using the same standards, in various matrices whose average atomic numbers might range from 4 to 94. Unlike most analytical techniques, where suites of standards are synthesized having similar bulk compositions as the samples and bracketing the concentrations of the elements of interest, the standards employed in microbeam analysis are most commonly pure elements, simple oxides, or other binary element compounds. This is true even though matrix effects on electron retardation and scattering, x-ray absorption, and secondary x-ray fluorescence can cause major variations in the differences between relative intensity and relative concentration.
Analyzing the Light Elements in an Electron Probe Micro Analyzer
Authors: Bastin GF , Heijligers HJM
Published: July 2020

Wavelength-dispersive analysis of the ultra-light elements boron, carbon, nitrogen, and oxygen requires much more complicated experimental procedures than the analysis of medium-to-high Z (Z >11) elements. For a large part this is the result of a number of fundamental physical problems which cannot be circumvented. The most difficult problems of this nature are those related to the differences in the x-ray emission profiles from one ultra-light element compound to another. These differences are caused by the fact that in exciting ultra-light element x-rays electronic transitions of the bonding electrons are involved. As a consequence one has to deal with large peak shifts and large peak shape alterations in WDS analysis of ultra-light elements. While peak shifts can easily be accounted for by simply retuning the spectrometer when moving from standard to specimen the effects of peak shape alterations are much more difficult to deal with and in general it is imperative to perform the intensity measurements in an integral fashion.
Analyzing Mg and Fe in Olivines, Pyroxenes, and Garnets: Systematic Discrepancies
Authors: Carpenter P , Armstrong J
Published: July 2020

Quantitative analysis of Mg and Fe in olivines, pyroxenes, and garnets is important for geochemical studies. Natural olivines have compositions close to the forsterite (Mg2SiO4) and fayalite (Fe2SiO4) binary system, with relatively minor substitution of other components. Pyroxenes and garnets are problematic in that they exhibit more diverse solid solution, and may contain both Fe2+ and Fe3+, the relative concentrations of which cannot be directly measured with the microprobe. The forsterite-fayalite olivine binary is a convenient system for studying the accuracy of Mg and Fe analysis without other complicating factors.

Bence and Albee utilized the a-factor approach for quantitative analysis of silicates, based on the empirical observation:

where CA,AB is the weight fraction of the oxide A in a binary oxide system AB, and KA,AB is the measured x-ray intensity of A relative to that of the pure oxide A.
Limits of Analytical Accuracy for Two Critical Semiconductors Systems: (Al, Ga)(As, P) and (In, Ga)(As, P)
Authors: Armstrong John T
Published: July 2020

Among the more important semiconductor materials, with commercially important applications in microelectronics, photonics, and nanodevice development are alloys in the system GaP-GaAs-AlAs- InAs (e.g., 1). These components have extensive regions of solid solution. With the wide variety of phases that can be grown in this system, it is possible to “tailor” heterojunctions that have desired band offsets or quantum wells that have a given shape of confinement potential, which is the basis of “bandgap engineering” (e.g., 2-4). In order to characterize the properties of these phases and maintain quality control in the manufacturing of devices utilizing these phases, it is critical to be able to perform accurate determinations of their compositions. This can be especially difficult, since many of the applications utilizing these phases involve micro- or nano-devices or thin multilayer coatings. In terms of the spatial analysis requirements, electron microbeam x-ray microanalysis is ideally suited for characterization of such specimens.
Beam Induced Composition Modifications During Electron Beam Microanalysis
Authors: Howitt D G , Medlin D L
Published: July 2020

The most common cause of composition modification to a specimen during electron probe microanalysis is the field induced migration of light elements. This is an indirect effect which occurs in response to the long range electric fields that form when dielectric specimens suffer charge imbalance. The result is that the ions are redistributed within the sample according to their respective mobilities and the affect is enhanced rather than eliminated when the sample is coated. The ions typically move radially outward in thin samples because of the excess production of secondary electrons from the specimen surfaces, Cazaux(1986)and downwards in conventional SEM samples when the field is due primarily to the deposition of electrons within the bulk of the specimen

Field induced migration is responsible for most of the elemental signal variations observed during the microanalysis of silicate glasses containing sodium or potassium ions.
Fluorescent Spectroscopy of Mineral and Material Samples
Authors: MacRae CM , Harrowfield I R , Wilson N , Yoshiya M , Fazey P , Peacock S , de Yong L , Adachi H
Published: July 2020

Wavelength dispersive spectrometry of long wavelength lines by EPMA can give information on the site symmetry and bonding of the x-ray-emitting atom. For fully focussing spectrometers, the energy resolution can be as high as 2eV or better at a spatial resolution of 1 μm, but electron beam currents often must be set to damaging levels. Fluorescent spectroscopy of the same lines in the commercial laboratory XRF spectrometer is far less damaging but spatial resolution is non-existent or, with collimators, relatively poor. With a combination of electron induced and x-ray induced fluorescent spectroscopy, and the insight provided by molecular orbital calculations, speciation or state analysis can be achieved even on damage prone specimens.

Electron and x-ray induced fluorescence has been employed to investigate surface coatings on magnesium metal. Oxygen Kα spectra for crystalline MgO, MgCO3 and powdered 4MgCO3.Mg(OH)2.5H2O were recorded using a TAP(2d=2.5757 nm) analysing crystal on a JEOL 8900R EPMA and a Philips PW 1404 XRF.
Electron Microprobe Reference Materials for Geologic Analysis a Need for Developing Strategy
Authors: Jarosewich Eugene
Published: July 2020

Each field of electron microprobe analysis has its own specific analytical difficulties. Problems relating to the analysis of geologic materials can be primarily attributed to the fact that the samples are nonconductive, some are unstable under the beam, and they have a complex matrix. There are various techniques to solve these analytical problems, but the selection of appropriate standards is one of most important factors.

In study of geologic materials a convention prevails that the summation approximates 100%. For most analyses summation is an indication of the quality of analysis, although some elements could be over or under corrected. Significant progress has been made in developing correction procedures, yet some fundamental parameters still are not well known, and the results will vary depending on which procedures or fundamental parameters are used. One of the most practical solutions to eliminate significant matrix effects is to select reference materials with a close composition to the unknown.
A Basalt Glass Standard for Multiple Micro Analytical Techniques
Authors: Meeker GP , Taggart JE , Wilson SA
Published: July 2020

Well-characterized calibration standards for microanalytical applications are difficult to obtain, often poorly characterized, and often not homogeneous from piece to piece. In addition, many microanalytical standards are available only in very small quantities making inter-laboratory comparisons difficult. To further complicate the situation, destructive microbeam techniques such as secondary ion mass spectrometry (SIMS) and laser source mass spectrometries (LSMS) require larger quantities of material than nondestructive techniques.

The U.S. Geological Survey, Geologic Division is in the process of evaluating ways to produce relatively large quantities of well-characterized standards. We are interested in producing standards of geological materials appropriate for multiple microbeam techniques including electron probe microanalysis (EPMA), SIMS and LSMS. The microbeam standards are produced by melting powders of standards of naturally occurring materials that the USGS has previously provided as bulk analytical standards.
Factors Affecting the Performance of Backscattered Electron Detectors at Low Beam Accelerating Voltages in SEM
Authors: Robinson V N E
Published: July 2020

The use of backscattered electron (BSE) imaging in low voltage scanning electron microscopy (SEM) has increased over the past few years. This appears to be due to several factors including improved performance of SEMs at low voltages, reduced beam penetration, more reliable metrology, improved atomic number (Z) contrast information (for low Z) and reduced charging artefacts over secondary electron (SE) imaging. Understanding the factors involved in low voltage BSE detection may assist in improving the information attainable.

It has been shown that the signal Sdet from a BSE detector, for EB ≫ Ew is given by

where η is the BSE yield, Ω is the solid angle subtended by the detector to the specimen, D is the internal conversion efficiency of the detector, EB is beam accelerating voltage, Ew is the energy barrier of the dead layer on the detector's surface, IB is the beam current, F(Z) and F(Ω) are functions which take into account the variation of BSE energy with atomic number Z and collection angle respectively.
Chemical Quantitative Analysis of Small Precipitates in the FE-SEM Using the Energy Distribution of Backscattered Electrons
Authors: Gauvin Raynald
Published: July 2020

Low voltage scanning electron microscopy with a field emission source allows characterization of materials with high spatial resolution. This high resolution comes from the low incident energy which gives a small interaction volume (about 10 nm in Fe at 1 keV ), from the field emission source which gives a small probe size (about 2.5 nm in the most recent FE-SEM) and from virtual, or through the lens, secondary electron detectors with gives high collection efficiency and eliminates some of the SEII and all the SEIII- For example, it has been shown that 10 nm NbC inclusions in steels can be imaged in such FE-SEM at 2 keV (this work was performed with a HITACHI S-4500). However, quantitative x-ray analysis of such precipitates are difficult because the critical ionization energy of the Nb Lα lines is equal to 2.37 keV, an incident electron energy of at least 5 keV must be used to get significant x-ray counts rates.
Wool and Cashmere Fiber Identification Study Using Scanning Electron Microscopy
Authors: Baker J D , Lentz H P , Kritikos D G , Schamber FH , Lee R J
Published: July 2020

Despite the large production and consumption of textile fibers on a global basis, the ability to identify specific types of textile fibers with similar physical-chemical properties is a challenging obstacle for the textile industry. One problem in particular is the identification of specialty animal fibers. Cashmere is a specialty fiber that has a value of 7 to 8 times higher than its similar counterpart wool. It is important, therefore, for textile manufactures to be capable of distinguishing between bails of high value specialty fibers and those containing contamination from lower value products.

Today the universally accepted method of identifying fibers is microscopic analysis. However, the optical microscope is limited because of the subjective nature of the analysis and its limited ability to easily measure different parameters of the fiber such as the fiber diameter, the fiber scale length and the fiber scale thickness.
Use of the Disk-of-least-confusion in X-ray Microanalysis
Authors: Kenik E A , Ren S X
Published: July 2020

Whereas the spatial resolution for standard secondary electron (SEI) imaging in a scanning electron microscope or electron probe microanalyzer is related to the incident probe diameter, the spatial resolution for x-ray microanalysis is related to the convolution of the probe diameter with the spatial extent of the analyzed volume for a point probe. The latter is determined by electron scattering in the specimen and the subsequent emission of excited x-rays from the specimen. As such, it is possible that “What you see is not what you get”. This is especially true for instruments with high brightness electron sources (field emission). This problem is compounded by probe aberrations which at Gaussian image focus can produce significant electron tails extending tens of microns from the center of the probe.
Quantifying SEM Resolution and Performance
Authors: Joy David C , Völkl Edgar
Published: July 2020

The ability to reliably and quickly determine the resolution of the scanning electron microscope (SEM) is highly desirable becauseonly then can the level of performance which is being achieved be compared to that which was anticipated or specified. Further, in activities such as automated line width measurements, or in telemicroscopy, the ability to quantify the imaging performance provides the remote operator with the necessary information to monitor, document, and optimize the instrument set-up. However, compared to the equivalent task on the transmission electron microscope (TEM) an analysis of SEM performance is hampered by poor signal to noise ratios, and the absence of ideal ‘white noise’ samples.

The two dimensional Fourier power spectrum of an image provides a readout of the frequency content of the information present in the micrograph. From an analysis of the power spectrum the highest spatial frequency transferred in the image can then be determined and hence the resolution of the micrograph can be specified.
Microstructure and Microtexture in Nb-Silicide Based Composites
Authors: Bewlay BP , Sutliff JA
Published: July 2020

Directionally solidified in-situ composites based on niobium and niobium silicides, such as Nb5Si3 and Nb3Si, are presently under investigation as structural materials [1, 2], Alloying additions of elements such as Hf, Ti and Mo to these silicides are also being explored in order to increase strength and oxidation resistance. The present paper describes the effect of Hf, Mo and Ti additions on microstructure and microtexture of high temperature silcide-based in-situ composites.

Alloys were prepared from high purity elements (>99.9%) using induction levitation melting in a segmented water-cooled copper crucible. The alloys were directionally solidified using the Czochralski method [2], Phase identification was performed using scanning electron microscopy, electron microprobe analysis (EMPA), and automated electron back scattering pattern (EBSP) analysis. Using EBSP, positive phase identification was accomplished by direct comparison of the location and character of the diffraction bands in the experimental pattern with those calculated from simulated patterns generated using the possible structure types.
Evaluation of Boron Nitride Coated Nextel 312TM Fiber/BlackglasTM Composites Using an Environmental SEM
Authors: Schalek Richard L , Helmuth John , Drzal Lawrence T
Published: July 2020

The most critical technical issue preventing large scale application of ceramic matrix composites is the cost-effective application of stable interface coatings on continuous ceramic fibers. Currently, an alumina-silica ceramic fiber containing up to 14 wt. % boria (Nextel 312TM) is composited at elevated temperatures to form a boron nitride (BN) coating on the fiber surface. This BN coating serves as a compliant layer facilitating crack deflection and producing a non-catastrophic failure mode. Continued development of these ceramic matrix composites requires a more complete understanding of the mechanistic paths involved in composite densification. The objective of this work is to investigate and more clearly describe the role of the BN coating and its relation to composite processing and properties of the densified Nextel 312TM fiber/BlackglasTM (silicon oxycarbide) composites.

Three composites consisting of as-received fibers (coated with an organic sizing), desized fibers (sizing removed by heating), and boron nitride coated fibers were fabricated using BlackglasTM preceramic polymer 489C B-stage resin.
‘Cool ESEM’ - Imaging Ice-Containing Systems at Freezer Temperatures
Authors: Fletcher AL , Keller TH , Thiel BL , Eddy AE , Donald AM
Published: July 2020

Conventional scanning electron microscopy permits the use of cryogenic techniques, which has led to the examination of ice-containing samples (eg ice cream) at temperatures of -80°C and below. At these temperatures moderate etching of the ice crystals occurs which helps to identify the crystals in the surrounding glassy matrix. However, imaging at higher temperatures - equivalent to those at which most ice-containing systems are actually utilised - is impossible because of rapid sublimation. We have set out to develop a system which will enable us to examine ice crystals at temperatures of -20°C and below, corresponding much more closely to realistic conditions of use.

In the environmental scanning electron microscope (ESEM), a gas can be maintained around the sample. Not only can this be used to maintain the sample in its native state, but the gas is actively involved in the imaging process through its role in signal amplification.
Secondary Electron Contrast in Molecular Liquids
Authors: Thiel BL , Stokes DJ , Donald AM
Published: July 2020

Liquid containing specimens can be stabilized for observation in the Environmental Scanning Electron Microscope (ESEM). It is also possible to examine systems that are primarily liquid, such as colloidal suspensions and gels, or even possess a multi-component liquid microstructure as in emulsions.(l) In order for such investigations to be useful, an understanding of the origins of secondary electron contrast in liquids is necessary. Our aim here is not to produce a complete theory of secondary electron emission in these systems, but to provide general guidelines for discriminating between two liquids based on relative contrast.

Secondary electron emission from a substance is determined by three processes: creation, transport through the material, and escape from the surface.(2) Contrast between two regions will be due to differences in one or more of these processes. Initial generation of secondary electrons is primarily a function of the ionization cross-sections of the substance and its density.
Charge Contrast: Some ESEM Observations of A New/Old Phenomenon
Authors: Doehne Eric
Published: July 2020

Over the past few years there have been occasional reports of unusual secondary electron contrasts in certain nonmetallic materials using conventional (CSEM-Johansen et al, 1997), low voltage (LV-SEM-Harker et al, 1993; Harker et al, 1994) and environmental scanning electron microscopy (ESEM-Griffin, 1997; T. Hardt, personal communication) which have documented novel contrast mechanisms whose origins are not yet well understood. Indeed, similar observations were made over 20 years ago in certain uncoated materials (such as SiC) using conventional SEM (Sawyer and Page, 1978). Aspects of these charge contrast imaging (CCI) phenomena are further documented here in a series of ESEM experiments on polished cross sections of uncoated travertine calcite. What is “old” is the fact that these contrasts have been reported on several occasions. What is “new” is the observation that these unusual contrasts are more readily studied and, in some cases, have been found in a wider range of materials using ESEM.
Operating Conditions For Quantitative X-Ray Analysis In The Environmental SEM
Authors: Carlton R A , Lyman C E , Roberts J E
Published: July 2020

Standard Reference Material (SRM) 482 of the National Institute of Standards and Technology is a set of 6 gold/copper wires, ranging in concentration from 0 to 100% Cu in 20% steps, intended for calibration studies of electron beam microanalyzers. This is an appropriate standard to test the accuracy of energy dispersive x-ray spectrometry (EDS) in the Environmental Scanning Electron Microscope (ESEM). While the presence of the gas in the sample chamber gives the ESEM its unique capabilities, it also is the source of complications to x-ray spectrometry. The gas can spread the primary electron beam into a wide skirt of electrons with the consequent production of x-rays many micrometers from the target location of the beam. In spite of the difficulties, at least two methods have been proposed to correct high pressure data to that expected at low pressures.
Ordering of a Functional Molecules on a Flat Surface as Evidenced by Scanning Probe Microscopies: The Case of a Di-Alkyl Amino Group
Authors: Gorman Christopher , Touzov Igor , Miller Russell
Published: July 2020

Our group is interested in exploring how functional molecules (e.g. those composed of organic functional groups that do not necessarily lend themselves to an ordered 2D packing arrangement) can form well-ordered adlayers with functional properties. To this end. we have studied the formation of self assembled structures of 5-(N,N-didecyl-amino)-2.4- pentadienal (DAPDA, Figure 1) deposited on a highly ordered pyrolytic graphite (HOPG) surface. This molecule has two distinctive features that should dramatically affect its ordering on a surface. Neither of these have been systematically explored in ordered adlayers. First, the extended conjugation of the molecule gives it a large in-plane dipole moment as well as a high polarizability. Second, it contains two hydrocarbon tails, only one of which can lie coplanar with the conjugated moiety. Both molecularly resolved monolayer and bilayer structures were found using a combination of scanning tunneling microscopy and tapping mode atomic force microscopies.
Langmuir-Blodgett Film Stability Via Atomic Force Microscopy
Authors: Takamoto Dawn Y
Published: July 2020

Langmuir-Blodgett (LB) films of fatty acid salts are inherently unstable due to the fundamental incompatibility of the asymmetric monolayer film transferred from the water surface with the centrosymmetric equilibrium form of the fatty acid bulk crystal. One consequence of this incompatibility is that fatty acid salt films deposited by the LB technique do not remain as flat and uniform films, but reorganize into bilayer step islands. By using mixed chain length films, the islands and holes had distinct heights that suggest this reorganization occurs by a bulk folding of the layers rather than a molecular reorganization of the molecules.

We have studied cadmium arachidate (CdA) LB films, varying the substrate used, the number of layers deposited, and the time the film spends under the aqueous subphase. All films were imaged in air with an Atomic Force Microscope (AFM).