STRUCTURAL-ANALYSIS OF EPITAXIAL-FILMS OF METAL PHTHALOCYANINES ON HYDROGEN-TERMINATED SI(111) SURFACES

Epitaxial growth of vanadyl- and chloro-aluminum-phthalocyanines has been examined on hydrogen-terminated Si(111) surfaces with various surface treatments. Molecular arrangements and orientation were investigated by reflection high-energy electron diffraction (RHEED) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS). Sharp RHEED patterns were observed for the films grown on the monohydride-Si(111) surface with a thickness up to 20 monolayers, while epitaxial growth did not occur on a surface terminated with the mixture of polyhydrides. Homogeneity and microscopic flatness of the substrate surface are essential factors for the epitaxial growth. RHEED study revealed that the molecules form commensurate centered rectangular lattices on the monohydride-Si(111) surfaces with an intermolecular distance of 1.38 nm, which was an optimum value for the molecules to stay parallel on the surface. The parallel molecular orientation was confirmed by ARUPS of the epitaxial films.