Microscopic evidence for spatially inhomogeneous charge trapping in pentacene.

Using high sensitivity electric force microscopy we are investigating the electronic properties at the semiconductor-dielectric interface in pentacene thin film devices. It is believed that the conduction takes place within the first few monolayers of the organic and is adversely affected by the presence of charge traps. We find that charge traps in polycrystalline pentacene are distributed inhomogeneously but do not appear to be associated with grain boundaries as is generally supposed. We will also report on ongoing studies of thin (1-3 monolayers) devices, where the relationship between the topography and the location of the charge traps is more easily interpreted.