Growth of alpha-sexithiophene nanostructures on C-60 thin film layers

Organic molecular beam grown α-sexithiophene (α-6T) forms nanostructured thin films on buckminsterfullerene (C60) thin film layers. At substrate temperatures of 300 K during growth a rough continuous film is observed, which develops to larger elongated islands and dendritic- as well as needle-like structures at temperatures around 390 K. X-ray diffractrometry reveals (100) crystalline orientation in the films grown at higher surface temperatures, which corresponds to upright oriented molecules. Rocking curves reveal the lowest mosaicity for samples grown at the highest substrate temperatures. From fluorescence polarimetry measurements the in-plane orientation within the needle like structures is determined. The polarimetry investigations together with the intensity of the fluorescence strongly indicate that the needle like structures consist of lying molecules.