Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 25: Organic films II

O 25.10: Vortrag

Dienstag, 28. März 2006, 18:00–18:15, PHY C213

Electronic structure of thin organic films on metal surfaces studied by UV- and resonant photoemission — •Azzedine Bendounan, Frank Forster, Achim Schöll, Johannes Ziroff, Eberhard Umbach, and Friedrich Reinert — Experimentelle Physik II, Universität Würzburg, am Hubland, 97074 Würzburg, Germany

We present high-resolution photoemission data on the valence band structure of organic thins films on noble metal surfaces, in particular on the epitaxial systems PTCDA/Ag(111) and NTCDA/Ag(111). The valence band of one monolayer PTCDA on Ag(111) is characterized by two spectral features located close to the Fermi energy. Both features are associated to the formation of a strong chemical bond between the substrate and the molecule. The binding energy of these features show an immediate dependence on the PTCDA film thickness. The NTCDA molecule is less strongly bonded to the Ag(111) substrate, but also for this system the formation of hybrid orbitals can be observed in the photoemission spectra. The observed HOMO structure shifts slightly as the NTCDA coverage increases. Moreover, by combination of NEXAFS and resonant photoemission data, we identify the NTCDA and Ag contributions to the various peaks in the photoemission spectrum. In addition, an information is obtained about the coherent and incoherent processes occuring after excitation by analysis of the evolution of the Auger and photoemission features in the resonant photoemission spectra.