Nucleation in Organic Thin Film Growth: Perylene on Al2O3/Ni3Al(111)

The molecular orientation of perylene thin films has been investigated using near-edge X-ray absorption fine structure spectroscopy. The presence of different molecular orientations in the monolayer, ranging from flat-lying to more upright-standing molecules, has been found and related with the different sets of growth parameters used for each sample preparation. The same molecular tuning has been observed in the multilayer regime. It is shown that it is possible to explain these results by using concepts of the atomistic theory of nucleation. Regarding perylene on Al2O3/Ni3Al(111) as a model system for organic layers in, for example, organic field effect transistors, our findings raise some questions about the suitability of perylene as an active layer in a real device.