# Presentation: 261752

## M. Meyyappan

- Director, Center for Nanotechnology
- NASA Ames Research Center
- Moffett Field, CA  94035
- meyya@orbit.arc.nasa.gov
- web:  http://www.ipt.arc.nasa.gov

- Carbon Nanotube
- Based Nanotechnology

## •	Nanotechnology and NASA

- Agenda

- •	Nanotechnology and NASA
- •	Carbon Nanotubes
- 		-	CNT - growth and characterization
- 		-	CNT based microscopy
- 		-	CNT based biosensors
- •	Some other Nano examples

## NASA's Own Moore's Law

## Why Nanotechnology at NASA?

- •	Advanced miniaturization, a key thrust area to enable new science and
- 	exploration missions
- 		-		Ultrasmall sensors, power sources, communication, navigation,
- 				and propulsion systems with very low mass, volume and power
- 				consumption are needed
- •	Revolutions in electronics and computing will allow reconfigurable,
- 	autonomous, “thinking” spacecraft
- •	Nanotechnology presents a whole new
- 	spectrum of opportunities to build
- 	device components and systems for
- 	entirely new space architectures
- 		-		Networks of ultrasmall
- 				probes on planetary surfaces
- 		-		Micro-rovers that drive,
- 				hop, fly, and burrow
- 		-		Collection of microspacecraft
- 				making a variety of measurements

- Europa Submarine

## Just one Material, so much Potential

## NASA's Investments in Nano

- •	NASA Ames Center for Nanotechnology, started in 1996, is the largest
- 	in-house R & D in Federal Government; consists of 50 scientists and
- 	engineers working on various aspects of experimental and computational 	nanotechnology fields.
- •	NASA Ames has strong collaboration with the academia
- 		-	undergraduate student research program
- 		-	high school student research program
- •	Smaller programs at JSC (CNT composites), Langley (Nano materials),
- 	Glenn (Energy storage), and JPL
- •	NASA’s university-based Nano-Institutes
- 		-	Three institutes, $3 M/year/institute for 5 + optional 3 years
- 			(Purdue, UCLA, Princeton/Texas A & M)
- •	Recent spin-off: Integrated Nanosystems, Inc.

## NASA Ames Nanotechnology

- Research Focus

***  Carbon Nanotubes**
- 	•	Growth (CVD, PECVD)
- 	•	Characterization
- 	•	AFM tips
- 		-	Metrology
- 		-	Imaging of Mars Analog
- 		-	Imaging Bio samples
- 	•	Electrode development
- 	•	Biosensor (cancer diagnostics)
- 	•	Chemical sensor
- 	•	Logic Circuits
- 	•	Chemical functionalization
- 	•	Gas Absorption
- 	•	Device Fabrication
*******	****Molecular Electronics**
- 	•	Synthesis of organic molecules
- 	•	Characterization
- 	•	Device fabrication
*******	****Inorganic Nanowires**
*******	****Protein Nanotubes**
- 	•	Synthesis
- 	•	Purification
- 	•	Application Development

*******	****Genomics**
- 	•	Nanopores in gene sequencing
- 	•	Genechips development
*******	****Computational Nanotechnology**
- 	•	CNT - Mechanical, thermal properties
- 	•	CNT - Electronic properties
- 	•	CNT based devices: physics, design
- 	•	CNT based composites, BN nanotubes
- 	•	CNT based sensors
- 	•	DNA transport
- 	•	Transport in nanopores
- 	•	Nanowires: transport, thermoelectric effect
- 	•	Transport: molecular electronics
- 	•	Protein nanotube chemistry
*******	****Quantum Computing**
*******	****Computational Quantum Electronics**
- 	•	Noneq. Green’s Function based Device Simulator
*******	****Computational Optoelectronics**
*******	****Computational Process Modeling****	**

## Carbon Nanotube

- CNT is a tubular form of carbon with diameter as small as 1 nm.
- Length: few nm to microns.
- CNT is configurationally equivalent to a two dimensional graphene sheet rolled into a tube.

- CNT exhibits extraordinary mechanical properties:  Young’s modulus over
- 1 Tera Pascal, as stiff as diamond, and tensile strength ~ 200 GPa.
- CNT can be metallic or semiconducting, depending on chirality.

## CNT Properties

- •	The strongest and most flexible molecular
- 	material because of C-C covalent bonding
- 	and seamless hexagonal network architecture
- •	Young’s modulus of over 1 TPa vs 70 GPa for 		Aluminum, 700 GPA for C-fiber
- 		-	strength to weight ratio 500 time > for Al; 			similar improvements over steel and 				titanium; one order of magnitude 				improvement over graphite/epoxy
- •	Maximum strain ~10% much higher than any 		material
- •	Thermal conductivity ~ 3000 W/mK in the axial 	direction with small values in the radial direction

## CNT Properties (cont.)

- •	Can be metallic or semiconducting depending on chirality
- 			-	‘tunable’ bandgap
- 			-	electronic properties can be tailored through application of 				external magnetic field, application of mechanical 							deformation...
- •	Very high current carrying capacity
- •	Excellent field emitter; high aspect ratio
- 	and small tip radius of curvature are
- 	ideal for field emission
- •	Can be functionalized

## CNT Applications:

- Structural, Mechanical

- •	High strength composites
- •	Cables, tethers, beams
- •	Multifunctional materials
- •	Functionalize and use as polymer back bone
- 		-	plastics with enhanced properties like “blow
- 			molded steel”
- •	Heat exchangers, radiators, thermal barriers, cryotanks
- •	Radiation shielding
- •	Filter membranes, supports
- •	Body armor, space suits

**Challenges**

- -	Control of properties, characterization
- -	Dispersion of CNT homogeneously in host materials
- -	Large scale production
- -	Application development

## CNT Applications:  Electronics

- •	CNT quantum wire interconnects
- •	Diodes and transistors for
- 	computing
- •	Capacitors
- •	Data Storage
- •	Field emitters for instrumentation
- •	Flat panel displays
- •	THz oscillators

**Challenges**

- •	Control of diameter, chirality
- •	Doping, contacts
- •	Novel architectures (not CMOS based!)
- •	Development of inexpensive manufacturing processes

## CNT Applications: 

- CNT Applications:
- Sensors, NEMS, Bio

- •	CNT based microscopy:  AFM, STM...
- •	Nanotube sensors:  force, pressure, chemical...
- •	Biosensors
- •	Molecular gears, motors, actuators
- •	Batteries, Fuel Cells:  H2, Li storage
- •	Nanoscale reactors, ion channels
- •	Biomedical
- 		-	in vivo real time crew health monitoring
- 		-	Lab on a chip
- 		-	Drug delivery
- 		-	DNA sequencing
- 		-	Artificial muscles, bone replacement,
- 			bionic eye, ear...

**Challenges**

- •	Controlled growth
- •	Functionalization with
- 	probe molecules, robustness
- •	Integration, signal processing
- •	Fabrication techniques

## CNT Synthesis

- •	CNT has been grown by laser ablation
- 	(pioneering at Rice) and carbon arc process
- 	(NEC, Japan) - early 90s.
- 		-	SWNT, high purity, purification methods

- •	CVD is ideal for patterned growth 		(electronics, sensor applications)
- 		-	Well known technique from 				microelectronics
- 		-	Hydrocarbon feedstock
- 		-	Growth needs catalyst 						(transition metal)
- 		-	Multiwall tubes at
- 			500-800° deg. C.
- 		-	Numerous parameters
- 			influence CNT growth

## Catalyst Characterization

- •	Catalyst surface characterized by AFM (with SWNT tip) and STM.
- •	AFM image of as-sputtered 10 nm iron catalyst (area shown is
- 	150 nm x 150 nm).  Also, the same surface after heating to 750° C
- 	(and cooled) showing Fe particles rearranging into clusters.

- •	STM image of a nickel catalyst
- 	showing nanoscale particles
- •	These results are consistent with
- 	high resolution TEM showing
- 	particles as small as 2 nm.

## CVD Growth Mechanisms For 

- •	Adsorption and decomposition of feedstock on the surface of the catalyst particle
- •	Diffusion of carbon atoms into the particle from the supersaturated surface
- •	Carbon precipitates into a crystalline tubular form
- •	Particle remains on the surface and nanotube continues to lengthen - “base growth”
- 	mechanism
- •	Growth stops when graphitic overcoat occurs on the growth front - “catalytic poisoning”

- CVD Growth Mechanisms For
- Carbon Nanotubes

## SWNTs on Patterned Substrates

- -	Methane, 900° C, 10 nm Al/1.0 nm Fe/0.2 nm Mo

## Raman Analysis of SWNTs

- •	2 mw laser power, 1 μm focus spot
- •	Characteristic narrow band at 1590 cm-1
- •	Signature band at 1730 cm-1 at SWNTs
- •	Diameter distribution 1.14 nm to 2 nm; consistent with TEM results
- •	High metallic % of NTs

## Multiwall Nanotube Towers

- Grown using ethylene at 750o C

## ICP Reactor for CNT Growth

- •	Inductively coupled plasmas are the simplest type of plasmas; very efficient in sustaining 	the plasma; reactor easy to build and simple to operate
- •	Quartz chamber 10 cm in diameter with a window for sample introduction
- •	Inductive coil on the upper electrode
- •	13.56 MHz independent capacitive power on the bottom electrode
- •	Heating stage for the bottom electrode
- •	Operating conditions
- 	CH4/H2 : 5 - 20%
- 	Total flow : 100 sccm
- 	Pressure : 1 - 20 Torr
- 	Inductive power : 100-200 W
- 	Bottom electrode power : 0 - 100 W

## CNT in Microscopy

- Simulated Mars dust

- Atomic Force Microscopy is a powerful technique for imaging, nanomanipulation, as platform for sensor work, nanolithography...
- Conventional silicon or tungsten tips wear out quickly.
- CNT tip is robust, offers amazing resolution.

- 2 nm thick Au on Mica

## MWNT Scanning Probe

## 280 nm line/space.  Array of polymeric resist on a silicon substrate.

- Profilometry in Integrated Circuit
- Manufacturing

- MWNT Probe

- Conventional Si Pyramidal Cantilever

- Nguyen et al., Nanotechnology, 12, 363 (2001).

## AFM Image with a MWNT Tip

- 193 nm IBM Version 2 Resist

## AFM Image with MWNT Tip 

- Nguyen et al., App. Phys. Lett., 81, 5, p. 901 (2002).

- AFM Image with MWNT Tip

- DUV Photoresist Patterns Generated by Interferometric Lithography

## Imaging of Mars Analogs

- Red Dune Sand (Mars Analog)

- Optical image

- AFM image using carbon nanotube tip

## High Resolution Imaging of 

- DNA

- PROTEIN

- High Resolution Imaging of
- Biological Materials

## CNT Based Biosensors

- •	Our interest is to develop sensors for astrobiology to study origins of life.  CNT, though inert,
- 	can be functionalized at the tip with a probe molecule.  Current study uses AFM as an
- 	experimental platform.

- •	The technology is also being used in collaboration with NCI to develop 		sensors for cancer diagnostics
- 		-	Identified probe molecule that will serve as signature of leukemia 				cells, to be attached to CNT
- 		-	Current flow due to hybridization will be through CNT electrode to 			an IC chip.
- 		-	Prototype biosensors catheter development

## The Fabrication of CNT Nanoelectrode Array

**(1) Growth of Vertically Aligned CNT Array**

**(2) Dielectric Encapsulation**

**(3) Planarization**

**(4) Electrical Property Characterization**
**By Current-sensing AFM**

**(5) Electrochemical Characterization**

- we

- re

- ce

- Potentiostat

## Fabrication of CNT Nanoelectrodes

- 45 degree perspective view

- Top view

- Side view after encapsulation

- Top view after planarization

- J. Li et al, *Appl. Phys. Lett*., **81**(5), 910 (2002)

## Slide 31

## Chemical Functionalization 

- Highly selective reaction of primary amine with surface –COOH group

## Functionalization of DNA 

- Cy3 image

- Cy5 image

## CNT DNA Sensor

**3+**

**2+**

**e**

**3+**

**2+**

- Using Electrochemical Detection

**MWNT array electrode functionalized with DNA/PNA probe as an ultrasensitive sensor for detecting the hybridization of target DNA/RNA from the sample.**
- Signal from redox bases in the excess DNA single strands
**The signal can be amplified with metal ion mediator                        oxidation catalyzed by Guanine.**

## Electrochemical Detectionof DNA Hybridization

- 1st, 2nd, and 3rd cycle in cyclic voltammetry

- 1st – 2nd scan: mainly DNA signal
- 2nd – 3rd scan: Background

## CNT-based Logic and Memory Devices

- by Chongwu Zhou (USC) and Jie Han (NASA Ames)

- 100

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**V****0**

**V****DD**

**Carbon nanotube**

**n-type**

**p-type**

**V****ou**t

**V****in**

**p-MOSFET**

**n-MOSFET**

## Switching Energy of Electron

- Devices and Brain Cells

## Four-level CNT Dentritic Neural Tree

- •	Neural tree with 14 symmetric Y-junctions
- •	Branching and switching of signals at each junction similar to what happens in biological 	neural network
- •	Neural tree can be trained to perform complex switching and computing functions
- •	Not restricted to only electronic signals; possible to use acoustic, chemical or thermal 		signals

## •	Estimated surface area of purified HiPCo SWNTs is 1580 m2/gm

- •	Estimated surface area of purified HiPCo SWNTs is 1580 m2/gm
- •	Applications in catalysis, gas absorption....

## Functionalization Using a Glow Discharge

## Atomic H Functionalization: FTIR

## Zinc Oxide Nanowires

## Protein Nanotubes

- •	Heat shock protein (HSP 60) in organisms living at high temperatures
- 	(“extremophiles”) is of interest in astrobiology
- •	HSP 60 can be purified from cells as a double-ring
- 	structure consisting of 16-18 subunits.  The
- 	double rings can be induced to self-assemble
- 	into nanotubes.

## Extremophile Proteins for Nano-scale Substrate Patterning

**Nano-scale engineering for high resolution lithography**

***Extremophile Proteins for ******Nano-scale Substrate Patterning***

## DNA Sequencing with Nanopores

- DNA in buffer
- Voltage clamp
- Measure current

- G. Church, D. Branton, J. Golovchenko, Harvard
- D. Deamer, UC Santa Cruz

- The Concept

## Present

- Future

- The Sequencing Concept

## Summary

- •	Nanotechnology is an enabling technology that will impact electronics 	and computing, materials and manufacturing, energy, transportation....
- •	The field is interdisciplinary but everything starts with material science.  	Challenges include:
- 		-	Novel synthesis techniques
- 		-	Characterization of nanoscale properties
- 		-	Large scale production of materials
- 		-	Application development
- •	Opportunities and rewards are great and hence, tremendous worldwide 	interest
- •	Integration of this emerging field into engineering and science curriculum 	is important to prepare the future generation of scientists and engineers