Long-Range Order in an Organic Overlayer Induced by Surface Reconstruction: Coronene on Ge(111)

Using scanning tunneling microscopy, we show that coronene molecules form supramolecular structures upon room-temperature deposition on Ge(111), in full commensurability with the c(2 x 8) reconstruction of the clean surface. The molecules are not adsorbed in a planar manner in the first layer; the balance between lateral intermolecular interactions and directional bonding to the surface forces them into a tilted configuration. Further coronene deposition leads to the formation of large domains of weakly bonded molecules adsorbed on top of the first layer. The ordering of the second layer is dictated. by both, the first layer of molecules and the unaltered reconstructed substrate underneath. We provide a detailed analysis of the encountered molecular periodicities and discuss the mechanisms that lead to long-range ordering in these layers.