EPITAXIAL-GROWTH OF METAL-PHTHALOCYANINES ON HYDROGEN-TERMINATED SI(111) SURFACES

Molecular arrangements and orientations of metal-phthalocyanines (MPc's, M=VO, and AlCl) in epitaxial films grown on hydrogen-terminated Si(lll) surfaces were investigated by reflection high-energy electron diffraction (RHEED) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). RHEED studies revealed that VOPc and AlPcCl molecules formed centered rectangular lattices, [(3 4)(-3 1)], [(4 3)(-1 3)], and [(4 1)(1 4)], on the monohydride Si(111) surface. The lattices were commensurate to the substrate surface and the intermolecular distance was 1.38 nm. The molecules are thought to pack together as close as possible with their molecular planes parallel to the surface. The parallel molecular orientation was also confirmed by ARUPS measurements of the epitaxial films. Epitaxial features were strongly influenced by the surface treatments of hydrogen termination. Homogeneity and microscopic flatness of the substrate surface are important factors for the epitaxial growth of MPc molecules.