Pentacene thin films on diamond surfaces

The focus of this work is the study of influence of the substrate on the structural and optoelectronic properties of pentacene thin films. The termination of diamond surfaces with oxygen and hydrogen was used to change the chemical and electronic properties of the substrate without any modification of the surface morphology. It was found that the crystal structure of pentacene films depends on the termination and filament-like growth is preferably for the H-terminated diamond surface. Applied for the first time the temperature dependent photocurrent experiments in energy from 0.7 to 6 eV revealed a polarization dependent excitonic absorption in pentacene. Exciton dissociation and autoionization are identified as the dominant mechanisms of the photo-generation of free charge carriers in pentacene thin films.