Crystallinity of the epitaxial heterojunction of C₆₀ on single crystal pentacene

The structure of pn heterojunctions is an important subject in the field of organic semiconductor devices. In this work, the crystallinity of an epitaxial pn heterojunction of C₆₀ on single crystal pentacene is investigated by non-contact mode atomic force microscopy and high-resolution grazing incidence x-ray diffraction. Analysis shows that the C₆₀ molecules assemble into grains consisting of single crystallites on the pentacene single crystal surface. The in-plane mean crystallite size exceeds 0.1 µm, which is at least five time larger than the size of crystallites deposited onto polycrystalline pentacene thin films grown on SiO₂. The results indicate that improvement in the crystal quality of the underlying molecular substrate leads to drastic promotion of the crystallinity at the organic semiconductor heterojunction.