Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 34: Metal Substrates: Adsorption of Organic/Bio Molecules II

O 34.9: Talk

Tuesday, February 26, 2008, 15:45–16:00, MA 043

Adsorption studies of azobenzene molecules on Cu(001) and Au(111) — •Marten Piantek, Matthias Bernien, Jorge Miguel, and Wolfgang Kuch — Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14145 Berlin

Mono- and multilayers of Dimetacyano-azobenzene (DMC) have been evaporated under ultra high vacuum conditions on Au(111) and Cu(001) substrates in order to investigate the influence of the substrate on their physical properties. The electronic properties as well as the adsorption geometry of the molecules were studied by angle-dependent near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. DMC molecules adsorb in their planar trans conformation flat on the Au(111) surface. X-ray photoemission spectroscopy (XPS) of the monolayer on Au(111) yielded the same spectra as for the multilayer. Thus we conclude that there are no additional chemical bonds formed between the molecule and the metallic surface. On Cu(100) the molecules in the first monolayer present an out-of-plane geometry with respect to the substrate. From the change in the π * resonances at the N K-edge NEXAFS we conclude that a molecular nitrogen π -bond breaks, while the angular dependence of NEXAFS shows that the benzonitrile moieties are tilted out of the molecular plane. The XPS N1s peaks of a monolayer of DMC on Cu(001) are shifted compared to those of the multilayer sample, due to an additional bond formation to the substrate.