The electronic structure of iron phthalocyanine (FePc)
and interface
properties on Ag(111) and Au(100) are investigated by photoexcited
electron spectroscopies: photoemission (XPS and UPS) and X-ray absorption
spectroscopy (XAS or NEXAFS). Valence band structures with Fe character
were identified using resonant photoemission. The strength and nature
of the interaction at the interface depend clearly on the substrate.
A strong interaction of the central metal atom of the phthalocyanine
occurs on Ag(111), whereas no significant changes of the electronic
situation were found for FePc on Au(100). Resonant photoemission data
show that for FePc on Ag(111) the formed interface states close to
the Fermi level are determined by the interaction between Fe 3d states
and substrate related states. On the other hand, also the nitrogen
atom of FePc is involved in the interaction.
The electronic properties of the interface between cobalt phthalocyanine and gold substrate were investigated by photoexcited electron spectroscopies (UPS, XPS, and XAES). The experimental data indicate a quite strong interaction between the organic molecules and the metallic substrate, which is concluded from the different shape of the XPS Co 2p and Co LVV Auger spectral lines, as well as a splitting of the HOMO in the UP spectra. Initial and final state effects in photoemission and a possible change of the crystal field symmetry at the interface are discussed.
The work was supported by the German Research Council Ch 132/20-2. We acknowledge the Helmholtz-Zentrum Berlin -Electron storage ring BESSY II for provision of synchrotron radiation at the Optics-beamline. Financial travel support by BESSY is gratefully acknowledged. We thank W. Neu for technical support.
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