Temperature-dependent Electrical Characterization of Single and Dual-gate Flexible Carbon Nanotube Thin Film Transistors

Abstract

Dual-gate carbon nanotube thin film transistors (CNTTFTs) with hafnium dioxide (HfO2) and silicon dioxide (SiO2) as gate dielectrics and single-gate CNTTFTs of two types both of bottom-gate structure but one with HfO2 as gate dielectric and another with SiO2 as gate dielectric were fabricated on a flexible polyimide substrate using a scalable process. Electrical characteristics of the fabricated devices at elevated temperatures varying from 25 to 120°C were investigated and compared. Both single and dual-gate flexible devices have exhibited p-type characteristics. As the temperature was raised the on-current, off current, subthreshold swing, transconductance and drain conductance of both single and dual-gate devices increased whereas on–off current-ratio and threshold voltages decreased. The devices exhibited deterioration in transconductance and on-current with the increase of channel lengths. The present work illustrates that dual-gate flexible CNTTFTs outperform the single-gate flexible CNTTFTs in all electrical characteristic parameters and have shown the highest gate control over the channel at different temperatures varying from 25 to 120°C. The performance variations of both single and dual-gate flexible devices were less than 3.1% till the temperature of 50°C and were operational as CNTTFTs at temperatures varying from 25 to 120°C. The on–off current ratio, subthreshold swing, and threshold voltages deteriorate highly at temperatures higher than 120°C and also it was investigated that electrical characteristics were not repeatable at temperatures higher than 120°C. The CNTTFTs on the flexible substrate can be used for flexible electronics applications till 120°C.