Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)
O 17.36: Poster
Monday, March 26, 2007, 17:30–20:30, Poster C
Towards real surfaces: adsorption of ferrocene dithiolate between defective Ag(111) surfaces — •Thomas Bredow1, Herbert Pfnür2, Christoph Tegenkamp2, and Jörg Meyer3 — 1Universität Bonn, Institut für Physikalische und Theoretische Chemie, Wegelerstr. 12, 53115 Bonn, Germany — 2Leibniz-Universität Hannover, Institut für Festkörperphysik, Appelstr. 2, 30167 Hannover, Germany — 3Fritz-Haber-Institut, Faradayweg 4-6, 10033 Berlin, Germany
In recent experiments ferrocene-1,1’-dithiol (FDT) has been successfully tested as a molecular contact between silver electrodes. A large conductance without activation thresholds was observed and confirmed by theoretical studies. Our earlier model calculations considered FDT adsorption at perfect Ag(111) surfaces. As real electrode surfaces are expected to contain defects such as adatoms, steps and vacancies, the adsorption of FDT at defective Ag(111) surfaces has been studied. Periodic slab calculations are performed at DFT level with the plane-wave code VASP employing the projector-augmented wave method. Based on our previous experience FDT is adsorbed dissociatively as thiolate via the sulfur atoms. Various adsorption sites above or near single point defects or small 2x2 terraces are considered. We found that FDT-surface interaction is substantially enhanced by the presence of defects. The molecule is slightly deformed for optimal bond formation with the surface atoms. The projected density of states near the Fermi level is compared to previous results for the perfect surfaces and related to the measured conductivity.