Nanoscale selective area epitaxy of C60 crystals on GaAs by molecular beam epitaxy

Abstract

Fabrications of nanoscale structures of C60 crystals on GaAs substrates are successfully achieved by selective area molecular beam epitaxy. The grown structures are examined by scanning electron and atomic force microscopies. The {100} and {110} facets appear at the side boundaries of the C60 crystals. The surface morphology of C60 crystals grown on GaAs (111)B is much smoother than that grown on GaAs (001). Good crystalline properties of C60 films grown on GaAs (111)B are also confirmed by x-ray diffraction φ (phi) scan measurement. During C60 deposition, C60 molecules landing on SiO2 mask either evaporate or migrate to the open area enhancing the growth rate at the edges of the area. The mean diffusion length of C60 molecules on SiO2 mask at 200°C is evaluated to be 200–300nm. The C60 crystals grown on GaAs (001) with narrow open area (100–200nm) have a fourfold symmetry, indicating that the epitaxial orientation of these C60 crystals is [001]. This result should be compared with the [111] orientation observed in planar or wide area growth.