On-current tunable carbon nanotube thin-film transistor by SiO2 passivation layer

Abstract

A concept of tuning the on-current for p-type carbon nanotube thin film transistors (CNT TFTs) by SiO2 passivation layer has been proposed, which meets the different current density requirement for macroelectronic applications. The adsorbed oxygen molecules shift the fermi level down towards valence band, which decreases the barrier height between CNTs and electrodes for holes, so that an as-made CNT TFT with titanium or gold electrode exhibits dominant p-type conduction behavior although the intrinsic behavior of carbon nanotube (CNT) is bipolar. In order to tune the on-current of the p-type CNT TFTs, annealing process in high temperature and SiO2 passivation layer by Plasma Enhanced Chemical Vapor Deposition are used to desorb and prevent oxygen molecules from adsorbing onto the channel again. The methods for forming passivation layer are industry-compatible. Important factors affecting the tuning performance include the thickness and the length of the channel layer are studied in this paper. Besides, the mechanism of the tuning process is disclosed. We found the on-current tuning effect by SiO2 passivation layer is more significant for CNT TFTs with longer channel length than those with shorter channel length. Moreover, a positive correlation between the tuning efficiency and the thickness of passivation layer is concluded from experiments.