Carbon Nanotubes as Injection Electrodes for TFTsKevin Wang Nanofabrication Seminar2008/4/27

Concept

Aguirre, C.M., Martel, R. et al. Engineering Physics, EP Montréal Chemistry, U. of Montréal

Backgated

Pentacene Island

Thin Film

Fabrication – Island

Double-wall nanotubes Form gaps - electrical breakdown

Contacts – optical lithography Ti and Pd by e-beam evaporation Anneal (vacuum) 550°C, 1h

Post-Breakdown

Fabrication – Island (cont.)

Spin-coat precursor 2 mg/mL chloroform solution

13,6-N-sulfinylacetamido-pentacene Converts to pentacene

(170-200°C)

Asymmetric CNT – Pd

Fabrication – TFT

SWNTs (10 nanotubes/μm2)

Ti contacts, optical Lithography, liftoff Sonicate free nanotubes Anneal (vacuum) 550°C, 1h

Pentacene (50nm) Vacuum sublimation (0.2nm/s)

Fabrication – TFT (cont.)

W/L = 200μm/20μm Au or Ti, 30 nm thick

Performance – Island

40 nm gap device Ion/Ioff = 100 Ion = 2nA (Vds = 8V)

Superlinear IV Poor gate control tox = 20 nm

Subthreshold Swing 1.3V/dec

Asymmetric CNT-Pd

Injection from CNT side 21x more current CNT good emitter, poor collector?

Performance - TFT

CNT array – ideal linear behavior Au, Ti – nonlinear, large contact

barriers

Barrier at CNTlowered by E-field enhancement Molecular energy shift

Performance – TFT (cont.)

Conclusion

Carbon nanotubes enhance transistor current

Effective barrier lowering at CNT-Pentacene interface

Additional

Ti contacts