Abstrakt

We utilize low-energy electron microscopy (LEEM) to characterize the bimolecular domains composed of cobalt phthalocyanine (CoPc) and perfluorinated copper phthalocyanine (F16CuPc) adsorbed on Ag(100) surfaces at room temperature and subsequently annealed at 470 K. After deposition of the two molecules in a 1:1 ratio, the first monolayer of the bimolecular phase is given by a (52⎯⎯√×52⎯⎯√) R45° superstructure. The phthalocyanine (Pc) molecules are adsorbed in this structure in such a way that the molecular axes (given as diagonals connecting the phenyl rings on opposite lobes) are rotated by ±27.5° with respect to the ⟨011⟩ directions of the substrate. This results in two domains of opposite chirality. The structure factor of the constituent molecules enables the identification of these domains in the LEEM operated either in dark-field or microdiffraction (μLEED) mode. We show that the initial deposition of 0.5 ML of F16CuPc results in the formation of a 2D gas phase with discrete azimuthal orientations of the flat-lying molecules. Tracking the evolution of the diffraction pattern during deposition shows that the addition of CoPc to this 2D molecular gas triggers the immediate condensation of the bimolecular phase.