A Study of Room Temperature Deposition Techniques on Insulator
Substrates.
A Study of Electrophoretic Deposition (EPD) of Carbon Nanotubes
on Insulator SubstratesJared DeSoto, Anirban Sarkar, and Theda
Daniels-RaceApplied Hybrid Electronics Materials & Structures
(AHEMS) LaboratoryDivision of Electrical and Computer Engineering
School of Electrical Engineering and Computer ScienceLouisiana
State University and A&M College, Baton Rouge, LA 70803SESAPS,
2013
Bottom right corner: SESAPS 20131Table of Contents
Carbon Nanotubes: Introduction and SynthesisSolution-Based
Deposition TechniquesElectrophoretic
DepositionFundamentalsBenefitsResearch MotivationExperimental
ProcedureProcess RecipesExperimental ResultsConclusions and Future
Work
Carbon Nanotubes (CNTs): Introduction and Synthesis
http://www.futuretimeline.net/21stcentury/images/carbon-nanotube-2040.jpghttp://jnm.snmjournals.org/content/48/7/1039/F1.large.jpgSingle-walled
carbon nanotubes (SWCNTs)Multi-walled carbon nanotubes
(MWCNTs)Single sheet of graphene rolled as a cylinderMultiple
sheets of graphene rolled into concentric cylinders
Synthesis: Direct Growth
Arc Discharge (Prof. Ijima,1991)
2. Laser Ablation(Prof. Smalley, Rice University)
3. Chemical Vapor Deposition (CVD)Solution-Based Deposition
TechniquesBenefits:Economical set-upRoom temperature processingLow
cost Simple apparatus Solution based depositionChoice of solvents
for dispersionDeposition of purified materialsControl of deposition
parametersFast processing timeNo vacuumPotential to scale-up for
mass productionPlastic and low temperature printing
technologieshttp://spie.org/Images/Graphics/Newsroom/Imported/0969/0969_fig1.jpgUsed
with Permission
State-of-the-art techniques:Spray Coating
Inkjet Printing
Drop CastingSpin CoatingDip/Rod CoatingAdd pictures for maybe
spray coating and inkjet printing4Electrophoretic Deposition
(EPD):Fundamentals and Benefits
Benefits of EPD:Simple experimental set up/ no vacuumFast
processing, high yieldApplicable to any powdered solid that forms a
stable suspensionBetter surface coverageControl of deposition
thicknessSingle-step processingPossibility to scale up for
large-scale applicationsTwo step process:Electrophoresis:Particle
migration under electric field Deposition:Particle coagulation on
the depositing electrode
Schematic of EPDChallenge and Research Motivation
EPD of CNTsPredominantly performed on conducting substrates e.g.
Al, Cu, ITO and conducting polymersCNT-based thin film
transistorsDeposition necessary on gate dielectric films (SiO2,
polyimide, Al2O3) Research Objective:Study of Electrophoretic
Deposition of CNTs on insulator (glass) substrates
Gate DielectricSource metalDrain metalSemiconducting CNT
networks6Experimental Procedure
Pre-cleaning of glass substrates by piranha treatmentSurface
functionalization by organosilane 20% APTES*Acid treatment of CNTs
( H2SO4:HNO3=3:1)Ultrasonic dispersion of CNTs in water (H2O):
EtOH=1:1 Controlled drop casting of CNTs 2nd round of APTES
treatment on the drop casted CNTsDispersion of acid-refluxed CNTs
in IPA (EPD Solution)Electrophoretic Deposition Applied voltage:
100-150 V for 3 minutesAPTES*- 3-Amino propyl tri ethoxy
silaneProcess Recipes:
Recipe ARecipe BRecipe CPiranha treatment 1 hr.Piranha treatment
1 hr.
Piranha treatment 1 hr.20% APTES- 1 hr.20% APTES- 1 hr.
20% APTES- 1 hr.
Drop castingSolvent: H2O: EtOH=1:1Drop castingSolvent: H2O:
EtOH=1:1
Drop castingSolvent: H2O: EtOH=1:1
20% APTES- 1 hr.20% APTES- 1 hr.2% APTES- 1 hr.EPD voltage: 150
VDep. Time: 3 minEPD voltage: 30-40 VDep. Time: 3 min
EPD voltage: 150 VDep. Time: 3 min
Film Thickness: ~2.0mFilm Thickness: ~1.8mFilm Thickness:
~3.4mExperimental Results
EPD coated CNTsDrop casted CNTsOptical images of the EPD coated
CNTs on drop casted layer of CNTs1 cmAppreciable surface coverageNo
microscopic voids in the film morphologySEM image of the EPD coated
filmsExperimental ResultsKLA Tencor Alpha Step results:
Average film thickness: ~2-2.5 m
Average surface Roughness: ~500-600 nm
Raman SpectroscopyAbsence of radial breathing modes
(RBM)Disordered induced D-band (~1300 cm-1)Tangential G-band (~1600
cm-1)
Thickness and Surface RoughnessConclusion and Future WorkFuture
work:Use of semiconducting CNTsUse of competing deposition
techniques e.g. spray coating, inkjet printing to obtain the
initial CNT coating CNT EPD on sputter coated silicon dioxide
(SiO2), silicon nitride (SiN) filmsDevice Fabrication
First time study of EPD of CNTs on glass (insulator)
substrates
Use of CNTs (drop casted) to deposit thick CNT films by EPD
Characterization of the deposited films ( SEM, Raman, Alfa Step
data)
AcknowledgementsThis work was funded in part by the Louisiana
Board of Regents (LEQSF(2011-14) -RD-A-07), NASA (2011)-DART-44,
the generous support of Dr. Kristina Johnson, and the AES
Corporation. We are also grateful for the use of the Electronic
Material and Device Laboratory within the Division of Electrical
& Computer Engineering (LSU).