Philip Wallis, SouthWest NanoTechnologies
SINGLE WALL CARBON NANOTUBES FOR
PRINTED ELECTRONICS
CONTENTS
• What are Carbon Nanotubes?
• Properties of Carbon Nanotubes
• Advantages of Printed Electronics
• Overcoming Barriers to Adoption
• Current Status for TCF and TFTs
MAJOR CATEGORIES OF CARBON NANOTUBES
Multiwall Carbon nanotubes
5 < d < 200 nm
Additives for plastics and resins.
Single Wall Carbon Nanotubes
d ~ 1 nm
Thin Films for Electronics
SWCNT CHIRALITY AND DIAMETER
Armchair
n = m Metallic
Zig-Zag
Chiral
Distance from origin is
proportional to nanotube
diameter
Zig-Zag; (n,0) ; chiral angle = 0
7,4
7,2
9,0
9,1
8,3
8,0
8,2
8,1
7,3
7,1
6,3
6,0
6,2
6,1
5,3
5,0
5,2
5,1
4,3
4,0
4,2
4,1
6,4
3,0
3,2
3,1
5,4
7,0
2,1
2,0 1,0
4,4
3,3
5,5
2,2
1,1
6,5
6,6
(6,6) = 0.81 nm
7,5 (7,5) = 0.82 nm
8,4 (8,4) = 0.83 nm
9,3 (9,3) = 0.85 nm
9,2 (9,2) = 0.79 nm
10,1 (10,1) = 0.82 nm
10,0 (10,0) = 0.78 nm
SWCNT DENSITY OF STATES
Metallic tubes have non-zero electron density at the Fermi level.
Semiconducting tubes have zero density and exhibit a band gap.
Gap energies
E11
E22
OPTICAL ABSORBANCE SPECTRA
400 600 800 1000 1200 1400
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
S11
(6,5)
(6,5)
No
rma
lize
d A
bso
rba
nce
(7
80
nm
)
Wavelength (nm)
(8,7)
(8,6)
(7,6)
(8,7)
(8,6)(7,6)
Optical Absorbance Spectrum for SWeNT® SG65 and SG76
M11
S22
WHY CARBON NANOTUBES
• “Discovered” by IIjima in 1991 >20 Years Ago
• 50X Stronger than Steel
• More Conductive than Copper
• ½ Density of Al
• Metallic or Semiconducting
• Optically Transparent
POTENTIAL APPLICATIONS
High Performance Computing
Carbon Electronics
Lighting Displays Touch TFTs Sensors Solar
9 3/1/2012
Additive Process
(Printing)
Expose
Develop
Etch / strip
• Less steps
• Less waste
• Lower cost
• Short cycle time
Subtractive Process
(Photolithography)
WHY PRINT ELECTRONICS?
Expose
Develop
Etch/Strip
Deposit Film
Apply Resist Print
OVERCOMING THE BARRIERS TO ADOPTION
• Quality and Consistency
• Availability
• Cost
• Purity
• Other Carbon Forms
• Residual catalyst
• Chiral Mixture
• Handling
• Processing / Printing
2001
Founded Dr. Resasco
MANUFACTURING PLATFORM
Large Scale Production
2008
Norman, OK
Apps Dev Ctr
Canton, MA
2009
TSCA Listing
OVERCOMING THE BARRIERS TO ADOPTION
• Quality and Consistency
• Availability
• Cost
• Purity
• Other Carbon Forms
• Residual catalyst
• Chiral Mixture
• Handling
• Processing / Printing
TECHNOLOGY PLATFORM - CoMoCAT
• CO disproportionation ( 2 CO → C + CO2 )
• Supported transition metal catalysts
• Moderate pressures = 1 – 10 atm
Zone 3
Zone 2
Zone 1
Zone 4
Flo
w
P
• Fluidized bed for uniformity
690
695
700
705
710
715
720
10:48 10:55 11:02 11:09 11:16 11:24 11:31 11:38 11:45 11:52
Tem
per
atu
re (
C)
Time
Tuned Furnace Internal Temperatures
14" Above D. Plate
10" Above D. Plate
6" Above D. Plate
2" Above D. Plate
Set Point
Carbon Monoxide On
Thermocouples Within Fluidized Catalyst Bed
Thermocouples Above Fluidized Catalyst Bed
• Moderate temperatures (700 – 900°C) with precise
control (±1° C)
• Diameter Control and Distribution
• Tube Length
• Bundle Size
• Purity
• Temperature
• Pressure
• Catalyst Composition
• Gas composition
CUSTOMIZATION OF SWCNT
Variables Effects
400 600 800 1000 1200
0.5
1.0
1.5
2.0
2.5
3.0
A
bsorb
ance (
norm
aliz
edat
780 n
m)
Wavelength (nm)
T1
T2
T3
T4
Effect of Temperature
EFFECT OF TEMPERATURE
QUALITY MEASUREMENTS
OPTICAL ABSORBANCE SPECTRA
400 600 800 1000 1200 1400
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
(6,5)
(6,5)
No
rma
lize
d A
bso
rba
nce
(7
80
nm
)
Wavelength (nm)
(8,7)
(8,6)
(7,6)
(8,7)
(8,6)(7,6)
Optical Absorbance Spectrum for SWeNT® SG65 and SG76
M11
S22
QUALITY MEASUREMENTS
17
6,5
0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.50.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Diameter Distribution from Fluorescence Analysis
Re
lative
ab
un
da
nce
Nanotube diameter (nm)
100 200 300 400 500 600 700 800
0
1
2
3
4
5
6
100 200 300 400 500 600 700 800
0.0
0.5
1.0
1.5
2.0
Weig
ht
Temp
Derivative
Temp
TGA for SG76
OVERCOMING THE BARRIERS TO ADOPTION
• Quality and Consistency
• Availability
• Cost
• Purity
• Other Carbon Forms
• Residual catalyst
• Chiral Mixture
• Handling
• Processing / Printing
0.1 1 10 100 1000
0.1
1
10
100
VC100 Screen Ink
VC200 Gravure Ink
Vis
co
sity (
Pa
.s)
Shear Rate (s-1)
Viscosity vs. Shear for V-Series Conductive Inks
Courtesy Dr. Erika Rebrosova, Western Michigan University
Recovery to 80% of original
viscosity ~7 seconds after
reduction of shear rate
0 100 200 300 400 500
0
2
4
6
8
10
12
Shear Rate returns to 2 s-1
Vis
co
sity (
Pa
.s)
Time (sec)
Viscosity Recovery after Shear is Removed for VC100
Shear Rate Increased from 2 s-1
to 1,000 s-1
0
200
400
600
800
1000
Sh
ea
r R
ate
(s
-1)
RHEOLOGY OF V-SERIES SCREEN AND GRAVURE INKS
CNT Ink
* Patents pending
20
V2V™ INK TECHNOLOGY*
No residual surfactants
or processing aids!
CNTs can be printed using Standard
Industrial Printing Equipment
SWCNT TAILORED FOR APPLICATIONS
Semiconducting Enriched for TFTs
84 86 88 90 92 94 96 98 100
SG65 Production
R & D Enhanced SG65
New R & D Material
Synthesis Goal
90
95
97
99
Metallic Enriched for TCF Electrodes etc.
0 20 40 60 80
SG76
R & D Material
Synthesis Goal
33
45
67
METALLIC ENRICHED FOR TCF
10
100
1000
10000
75 80 85 90 95 100
Su
rfac
e R
esis
tan
ce (
/)
Transmittance at 550 nm (%)
SWeNT SG76
R & D Champion 4/14/11
R & D Champion with TopCoat
269 ohm/sq @
89.7% VLT
Chasm Film Ref # 128301 Our Champion Sample
(April 2011)
CNT TFTs ref. Zhou et al, Nano Lett. 9, 4285 (2009)
Red = Metallic CNT
Gray = SC CNT
FLEXIBLE, HIGH PERFORMANCE CARBON
NANOTUBE INTEGRATED CIRCUITS
CNT TFTs can have 100X higher Mobility than a-Si and Organic semiconductors!
Ref. Sun, D.M. et. al. Nature Nanotechnology Letts 6, 156–161 (2011).
Raw material Max
ON/OFF
Max Mobility
cm2/V.s
Channel L
µm
Channel W
µm
Goal >106 > 10 cm2/V/s
20 – 40 µm
40 – 80 µm
Current
Commercial
SWCNT
105 > 10 cm2/V/s 35 50 - 150
SEMICONDUCTING ENRICHED SWCNT INKS FOR
PRINTING THIN FILM TRANSISTORS
S D CNT film
G
SiO2
Low R Si
Cross-Sectional View of BSI Test TFT
THANK YOU
QUESTIONS?