Structure of pentacene thin films

Grazing incidence x-ray diffraction, x-ray reflectivity and atomic force microscopy have been performed to study the structure of pentacene thin films on oxidized Si substrates from submonolayer to multilayer coverages. The volume of the unit cell in the thin film phase is almost identical to that of the bulk phase, thus the molecular packing efficiency is effectively the same in both phases. The structure forming from the first monolayer remains the same for films at least 190Å thick. The in-plane structure of the submonolayer islands also remains unchanged within a substrate temperature range of 0Tsub45°C while the island size changes by more than a factor of 4.