Morphology and crystallographic properties of rubrene thin films grown on muscovite(0 0 1)

Thin films of the organic semiconductor rubrene were deposited on muscovite (0 0 1) substrates by hot wall epitaxy. The morphology of rubrene thin films in combination with their crystallographic properties was characterized by transmission electron microscopy. The initial growth proceeds in a partially wetting regime where amorphous droplets are formed. Through diffusive interactions the droplets merge together in partially crystalline open networks. At a more advanced growth stage, spherulites are formed and a variety of crystalline morphologies appears. Platelet- and needle-like morphologies can be assigned to the orthorhombic phase of rubrene with the [3 0 1] and [1 1 0] zone axes, respectively.