Phthalocyanine arrangements on Ag(100): From pure overlayers of CoPc and F16CuPc to bimolecular heterostructure.

Abstract

We have utilized scanning tunneling microscopy (STM) and low energy electron diffraction to determine the structural properties of two types of metal-phthalocyanines (MPcs), i.e., cobalt-phthalocyanine (CoPc) and hexadecafluorinated copper-phthalocyanine (F16CuPc) on the Ag(100) surface. For coverage close to one monolayer, both systems form long-range ordered structures with square unit cells. The size and rotation of the unit cell with respect to the silver lattice depend on the chemical composition of MPc. Both types of molecules prefer adsorption with around a 30° angle between the molecular axis and the [011] silver direction. The CoPcs mainly arrange in a (5 × 5)R0 phase; however, two additional local arrangements, a and a (7 × 7)R0, were detected by STM. The F16CuPcs form a structure. The co-adsorption of CoPc and F16CuPc on the Ag(100) surface in a 1:1 ratio leads to the formation of a compositionally ordered chessboard-like structure. During filled states imaging, the different appearance of the central part of each MPc allows us to distinguish CoPcs from F16CuPcs. Regardless of the applied voltage polarity, the ligands of F16CuPcs appear brighter than the ligands of CoPcs.