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.

KEYWORDS:

• Bottom-gate
• Carbon nanotube thin film transistors
• Dual-gate
• On–off current ratio
• Single-walled carbon nanotubes
• Subthreshold swing
• Temperature
• Transconductance

Acknowledgment

This work was carried out at the Centre of Excellence in Nanoelectronics (CEN) at Indian Institute of Technology Bombay (IITB) with financial support from Indian Nanoelectronics Users Program (INUP) initiated by Department of Information Technology (DIT), Ministry of Communications and Information Technology (MCIT), Government of India. The authors thank Professors and Staff members of CEN, IITB, for their valuable suggestions and support.

Additional information

Notes on contributors

M. C. Chandrashekhar

M C Chandrashekhar received the BE degree in electronics and communication engineering from Bangalore University, Bangalore, India and the ME degree in digital electronics from Karnatak University, Dharwad, India in 1997. Currently, he is an associate professor with the Department of Electronics and Communication Engineering, Sri Siddhartha Institute of Technology, Tumakuru and working toward the PhD degree with the Department of Telecommunication Engineering, Siddaganga Institute of Technology, Visvesvaraya Technological University, Tumakuru, India. His research interests include the design and fabrication of digital circuits using carbon nanotube thin film transistors on flexible substrates.

K. C. Narasimhamurthy

K C Narasimhamurthy received the BE degree in electronics and communication engineering from Bangalore University, Bangalore, India and the M.Tech. degree in industrial electronics from Mysore University, Mysore, India in 1995 and the PhD degree in VLSI from the Indian Institute of Technology, Guwahati, India in 2011. Currently, he is a professor with the Department of Telecommunication Engineering, Siddaganga Institute of Technology, Tumakuru, India. His research interests include the design of analog circuits using carbon-nanotube transistors, design, and fabrication of digital circuits using carbon nanotube thin film transistors on flexible substrates and virtual labs for analog electronic circuits. E-mail: [email protected]