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O: Fachverband Oberflächenphysik
O 58: Metal Substrates: Adsorption IV
O 58.4: Talk
Thursday, March 29, 2007, 16:30–16:45, H39
Substrate dependent bonding distances of PTCDA - A comparative X-ray standing-wave study on Cu(111) and Ag(111) — •Alexander Gerlach1, Stefan Sellner1, Frank Schreiber1, Norbert Koch2, and Jörg Zegenhagen3 — 1Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany — 2Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany — 3European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, BP 220, 38043 Grenoble Cedex 9, France
We study the adsorption geometry of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(111) and Cu(111) crystals using X-ray standing waves. The element-specific analysis shows that the carbon core of the molecule adsorbs in a planar configuration, whereas the oxygen atoms experience a non-trivial and substrate dependent distortion. On copper (silver) the carbon rings resides 2.66 Å (2.86 Å) above the substrate. In contrast to the conformation on Ag(111), where the carboxylic oxygen atoms are bent towards the surface, we find that on Cu(111) all oxygen atoms are above the carbon plane at 2.73 Å and 2.89 Å, respectively.