Geometrical Structure and Interface Dependence of Bias Stress Induced Threshold Voltage Shift in C₆₀-Based OFETs

Abstract

The influence of the nature of interface between organic semiconductor and gate dielectric on bias stress electrical stability of n-type C60-based organic field effect transistors (OFETs) was studied. The bias stress induced threshold voltage (Vth) shift was found to depend critically on the OFET device structure: the direction of Vth shift in top-gate OFETs was opposite to that in bottom-gate OFETs, while the use of the dual-gate OFET structure resulted in just very small variations in Vth. The opposite direction of Vth shift is attributed to the different nature of interfaces between C60 semiconductor and Parylene dielectric in these devices. The Vth shift to more positive voltages upon bias stress in bottom-gate C60-OFET was similar to that observed for other n-type semiconductors and rationalized by electron trapping in the dielectric or at the gate dielectric/C60 interface. The opposite direction of Vth shift in top-gate C60-OFETs is attributed to free radical species created in the course of Parylene deposition on the surface of C60 during device fabrication, which produce plenty of hole traps. It was also realized that the dual-gate OFETs gives stable characteristics, which are immune to bias stress effects.

Influence of the gate bias stress on the stability of n-type organic field-effect transistors based on dicyanovinylene–dihydroindenofluorene semiconductors

“…This work shows how slight structural modifications of the molecular structure of the semiconductor can lead to different insulator/semi-conductor interfaces and hence to electrical instabilities arising from different features. Interface effects on the electrical instabilities have previously been approached by Ahmed et al 63,64 In a second step, similar studies were performed by increasing the gate bias stress (VGSstress-VTH=40V) of (1) and (2)-based OFETs. The goal was to investigate the influence of the gate bias stress on the origin of the instabilities.…”

Metal–organic frameworks in a blended polythiophene hybrid film with surface-mediated vertical phase separation for the fabrication of a humidity sensor

“…20 Organic transistors inevitably suffer from poor stability and electrical properties, resulting in the slow response and recovery of the sensor device. 10,21,22 We attempted to address this issue by developing an OTFT-based humidity sensor, in which a humidity-capturing material was inserted into the polymeric semiconductor ( Fig. 1).…”

Solution-processed n-type fullerene field-effect transistors prepared using CVD-grown graphene electrodes: improving performance with thermal annealing

“…8,9 Pentacene, fullerene (C 60 ), and their derivatives have been extensively studied in small molecule semiconductors. [10][11][12] Among these, C 60 and its derivatives have been most attractive because of their good solubility in a variety of organic solvents. 13,14 However, the studies on the solution-processable C 60 -based FETs reported to date have focused only on the effects of surface modifications on the insulating layer and solvent dependence of the formation of a stable C 60 thin film, and the electron transfer properties.…”