Transition-Metal Phthalocyanines on Transition-Metal Oxides: Iron and Cobalt Phthalocyanine on Epitaxial MnO and TiOx Films

摘要

The interaction at interfaces between transition-metal phthalocyanines and ultrathin transition-metal oxide films is studied by means of photoemission (PES) and X-ray absorption spectroscopy (XAS). Our results are compared to the recently investigated system CoPc on MnO. A flat-lying adsorption geometry of iron and cobalt phthalocyanines (Fe Pc and CoPc) on the different oxide substrates was observed: ultrathin epitaxially grown MnO films and' ultrathin TiOx films. A charge transfer from the MnO, in particular, to the Fe atom of the FePc molecule is observed by both PES and XAS. X-ray absorption spectra of the N K-edge of FePc do not hint at a nitrogen involvement in the interaction process. As a consequence of the charge transfer, a shift of the Fermi level of the semiconducting MnO films is observed, which is visible as a shift of MnO related core levels to lower binding energy. In contrast, CoPc and FePc deposited on TiOx show no hints for a charge transfer, although the flat-lying adsorption geometry allows in principle a maximum interaction between the pi-system and the substrate. Increased surface roughness (compared to MnO) and an oxygen termination of the surface of the TiOx films is considered to suppress a possible strong interaction between the organic molecules and the substrate.