Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 18: Poster Session I - MA 141/144 (Atomic Wires; Size-Selected Clusters; Nanostructures; Metal Substrates: Clean Surfaces+Adsorption of Organic / Bio Molecules+Solid-Liquid Interfaces+Adsorption of O and/or H; Surface or Interface Magnetism; Oxides and Insulators: Clean Surfaces)

O 18.22: Poster

Montag, 25. Februar 2008, 18:30–19:30, Poster F

Ferrocene-1,1-dithiol (FDT) between perfect and defective Ag electrodes — Thomas Bredow¹, Jörg Meyer², Volodymyr Maslyuk³, •Gernot Gardinowski⁴, Christoph Tegenkamp⁴, Herbert Pfnür⁴, and Ingrid Mertig³ — ¹Institut f. Physikalische und Thoeretische Chemie, Universität Bonn, Germany — ²Fritz-Haber-Institut - Abtl. Theorie, Berlin, Germany — ³Fachbereich Physik, Martin-Luther-Universität Halle-Wittenberg, Germany — ⁴Institut f. Festkörperphysik, Leibniz Universität Hannover, Germany

The role of surface defects on the energetic and electronic structure of a molecule between two electrodes is of high intrest. We present a theoretical study of the interaction of ferrocene-1,1-dithiol (FDT) with two perfect or defective (vacancies, steps, etc.) parallel Ag(111) surfaces using DFT. We demonstrate, that the adsorption geometry has a strong effect on the electronic levels and conductivity. Furthermore, we show that the presence of point defects strongly enhances the molecule-surface interaction but has a suprisingly small effect on the density of states. Ferrocene dithiolate preferably binds to low-coordinated Ag atoms, which leads to significant shifts of the molecular orbitals and to a decrease of the electronic conductivity compared to the adsorption at perfect surfaces due to increased splitting of molecular levels. The latter leads to a decrease of the overlap with the metal levels near Fermi energy, and therefore to a reduction of the conductivity. Finally, we conclude that highly conducting molecules need collective stabilization by a significant amount of FDT molecules saturating the energetically favorable, but less conducting sites on an Ag electrode.