STM studies of the bimolecular layer of CoPc and F16CuPc on Ag(100) with non-equal composition

Abstract

The bimolecular layer composed of cobalt phthalocyanine (CoPc) and hexadecafluoro copper phthalocyanine (F16CuPc) deposited at room temperature on Ag(100) was investigated by scanning tunneling microscope. The coexistence of ordered bimolecular chessboard-like structure with 2D molecular gas phase is observed after deposition 0.7 ML of CoPc and 0.1 ML F16CuPc. The 2D gas phase contains mostly CoPc molecules. In the ordered domains, the CoPc:F16CuPc ratio is about 1.2, i.e. around five and a half times lower than the deposition ratio. The molecular ratio, higher than one, in the chessboard-like structure arises from the substitution of F16CuPc by cobalt compound. A slight increase (up to ca. 1.6) of the molecular ratio is observed close to the border of the ordered domain with CoPc rich 2D gas phase. Almost complete molecular monolayer was prepared by adding about 0.2 ML of CoPc. Thenceforth, the coexistence of chessboard-like bimolecular structure with monomolecular CoPc ordered domains is found. The addition of CoPc does not change the CoPc:F16CuPc ratio assembled in the bimolecular chessboard-like structure.