Dr. Richard A. WyskIndustrial & Manufacturing Engineering Department
Pennsylvania State University
CNT-Based Nano-Scale Fabrication: Creating Commercially Viable Nano-Manufacturing
Dr. Chuck ZhangDr. Ben Wang
Industrial & Manufacturing Engineering DepartmentFlorida State University
Presentation Outline
Background and Motivation
Review of NanoEM Process
Research Objectives
Experimental Setup and Investigations
Challenges
Conclusions and Future Work
Review of Nano-manufacturing Processes
Current Nano-fabrication Techniques:
Focused Ion Beam (FIB), Femto-Second Laser, Scanning
Probe Microscope (SPM), UV Lithography
Limited Resolution and Production Rate
Work only for SILICON and POLYMERIC materials. (Malshe et
al., 2005)
Electro Machining: Electro-Beam Machining (EBM), Electro-
Chemical Machining (ECM), Electro-Discharge Machining
(EDM)
Excellent for producing micron-sized features
Ability to generate 3-D features
Limiting Feature: Conventional Electrode Size ~ 20μm
Review of NanoEM Process
Non-contact process with small forces on both the
electrode and the workpiece.
Based on the thermoelectric energy created between a
workpiece and an electrode submerged in a dielectric
medium.
Workpiece + Electrode → separated by ‘spark-gap’
Pulsed discharge → Material Removal by Melting,
Evaporation and chemical reactions
Among other factors, Size and Form of the machined
feature depends primarily on properties of the electrode
such as electrode size, conductivity and strength.
Ignition Plasma formation Melting and evaporation
http://nmrc.yonsei.ac.kr/
Review of Nano-EM Processes
Feature Size(nm)
ElectrodeMaterial
PositioningSystem
OperatingEnvironment
WorkpieceMaterial
MaterialRemoval
Rate(nm3/s)
U of Kentucky
(Shreve & Vallance, 2004)
200 Tungsten STM Air Au -
U of Maryland(Gomez 2005) 150 Tungsten
STM +InertialMotor
Air/Vacuum
Au, Si3N4
-
U of Arkansas(Malshe et al. 2005) 10 Pt-Ir
STM(nano)
Oil Au (111) 141
Current ResearchPreliminary Results 30
CarbonNanotube
AFM &nano-stage
AirAu,
HOPG 700-8000 (HOPG)
Research Objectives
Use of Carbon Nanotubes as Electrodes
Non-Vacuum Environment – Commercial Nano-
stage instead of AFM
Range of materials including Si, Au and HOPG
Commercialization of the process
Targeted Feature Size: ~10nm
Targeted Material Removal Rate: 1000nm3/s
Foundation for creating $ 0.10 nano features
SiHOPG
Au
Power Source
Experimental Setup
Preliminary Experimental Setup using AFM:
AFM Tip Holder
NanoEm Experiments: STM tip
Etched tungsten tip
Resulting feature on Au (~ 200 nm)
U. of Kentucky
U. of Maryland
Etched tungsten tip
Holes using STM tip
NanoEM Experiments: Buckypaper Electrode
Experimental Setup:
Buckypaper Electrode
Silicon wafer with gold pattern surface
Buckypaper after EDM Buckypaper before EDM
NanoEM Experiments: Buckypaper Electrode
40V single pulse 100ms
50V single pulse 100msGap ~ 2 um
Holes using Buckypaper Electrode
Holes using Buckypaper Electrode(contd.)
Gap ~ 10 um
50V single pulse 100ms
Holes using AFM Tip
Typical hole diameter: ~100nm, distance between hole: 500nmPositioning error is due to open-loop piezo
-10V, 50ms (50 % duty ratio), 1000 times on HOPG surface
Holes using AFM Tip (contd.)
50ms, 1000times on Cr/Au film (after washing and blowing)
Metal-coated (Cr/Au) AFM tip, contact mode
Diameter: 130 nmDepth : 10 nm
Diameter : 100 nmDepth : 4 nm
-15V
-10V
AFM Tip with MWNT Attachment as Electrode
Solution processedRaw MWNT sample
• AFM was used to approach tip to the MWNT surface from top
• Cr/Au(10 nm/30 nm) coated AFM tip
• MWNT dispersed in surfactant (AC electric field 10 Vpp, 10 MHz )
• Too many MWNT surfactant remnant
AFM Tip with MWNT Attachment as Electrode (contd.)
~ 5V
• HOPG substrate• Commercial nanotube tip (CNTEK, MWNT
probe)
Holes using AFM Tip + MWNT Electrode
Before After
HOPG surface
10V, 100ms single pulse
AFM Tip with a
MWNT
Slots using AFM Tip + MWNT Electrode
6V 7VWidth : 38nmLength : 160nm
Width : 44 ~ 58nmLength : 400nmHOPG
Nanotube contact substrate with angle and bended
10nm60nm
MWNT Tip after Discharge
After discharge
Before discharge
Nanotube burn out?Or blasted away by force?
Some of the Challenges…
Plethora of uncertainties associated with the actual material
removal mechanism:
Discharge in nanoEM very sensitive to the environment (especially
moisture). Electrodes wear out immediately.
NanoEM process → Complex energy transport requiring multiple
levels of models of plasma generation + interaction with the surface.
Experimental Investigations: Surface response for ambient n-EM is
quite different from mere creation of craters, the main micro-EDM
mechanism → Need for Simulation Modeling.
At nano-level, sublimation from the surface, rather than melting and
evaporation, may be responsible for the material removal process.
Conclusion and Future Work
So near yet so far ! Experimental Investigations show the NanoEM
Process to be technologically feasible. Yet, lot of further research is
desired.
A preliminary simulation model is currently being built in ANSYS
using Thermo-electric and Thermo-elastic Analysis.
Further technological assessment includes detailed metrics
concerning feature size/variation/location, material removal rates,
electrode life, aspect ratio, profile of features, as well as the impact of
voltage and pulse characteristics on performance.
References
A.P.Malshe, K.Virwania, K.P.Rajurkar and D.Deshpande, 2005, ”Investigation
of Nanoscale Electro Machining (nano-EM) in Dielectric Oil”, CIRP Annals –
Manufacturing Technology, 54(1), pp.175-178.
S.M.Shreve and R.Vallance, 2004, “Nano-EDM Utilizing Etched Tungsten
Nanoprobes & Modulated Electrical Fields”, Lab Poster presented at The
Ninth Annual International Symposium for Magnetic Bearings,
www.engr.uky.edu/psl
J.G.Park, C.Zhang, R.Liang and B.Wang, “Nano-machining of highly oriented
pyrolytic graphite using conductive atomic force microscope tips and carbon
nanotubes”, 2007, Nanotechnology, 18(40).
Research by Dr. Gomez, University of Maryland, College Park.
http://www.cartoonstock.com/newscartoons/cartoonists/cgo/lowres/cgon188l.jpg
Thank You!
Top Related