Environmental stability and electronic transport of pentacene thin film transistors

Abstract

The influence of environmental conditions on the electronic structure and the device stability of polycrystalline pentacene transistors were investigated. Electrical in situ measurements of pentacene TFTs were carried out to study the influence of dry oxygen on the device operation. The polycrystalline pentacene thin film transistors were fabricated by organic molecular beam deposition (OMBD) on thermal oxide dielectrics. Exposing the pentacene film to oxygen leads to the creation of acceptor-like states deep in the bandgap. The acceptor-like states cause a reduction of the subthreshold slope and a shift of the onset of the drain current to positive gate voltages. The threshold voltage and the mobility of the transistors are not affected by the dry oxygen. A simple model will be described which directly correlates the onset voltage of the transistors with the acceptor concentration in the pentacene film.