Perfluorinated Phthalocyanines on Cu(110) and Cu(110)-(2 × 1)O: The Special Role of the Central Cobalt Atom
Axel Belser, Katharina Greulich, Peter Grüninger, Reimer Karstens, Ruslan Ovsyannikov, Erika Giangrisostomi, Peter Nagel, Michael Merz, S. Schuppler, Thomas Chassé, Heiko Peisert
Abstract
Interface properties of CoPcF16 on Cu(110) and Cu(110)-(2 × 1)O were investigated by X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), X-ray absorption spectroscopy (XAS), and scanning tunneling microscopy (STM). The results are compared to FePcF16 on Cu(110)-(2 × 1)O. A charge transfer from both substrates to the central Co ion of CoPcF16 is observed. Unlike to FePcF16 and related molecules, the strong interaction between CoPcF16 molecules of the first layer and the Cu(110) substrate is only partially suppressed by oxygen termination. The special nature of the electronic structure of the Co ion in Co phthalocyanines is discussed. The analysis of the fluorine Auger parameter enables the discussion of initial and final state effects of core level binding energy shifts in photoemission. A bidirectional charge transfer also involving the macrocycle of CoPcF16 molecules is concluded.