A scanning Kelvin probe study of charge trapping in zone-cast pentacene thin filmtransistors

Abstract

We have used scanning Kelvin probe microscopy (SKPM) as a local probe tostudy charge trapping in zone-cast pentacene field effect transistors on bothSiO2 and benzocyclobutene (BCB) substrates. Annealing at130 °C was found to reduce the threshold voltage, susceptibility to negative gate bias stress andtrapping of positive charges within single pentacene grains. We conclude that oxygen isable to penetrate and disassociatively incorporate into crystalline pentacene, chemicallycreating electrically active defect states. Screening of a positive gate bias caused by electroninjection from Au into pentacene was directly observed with SKPM. The rate of screeningwas found to change significantly after annealing of the film and depended on the choice ofgate dielectric.