Berlin 2008 – scientific programme

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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 18.28: Poster

Monday, February 25, 2008, 18:30–19:30, Poster F

Growth and electronic characterization of TMTTF-TCNQ on metal surfaces — •Dagmar Kreikemeyer Lorenzo, Isabel Fernández Torrente, Katharina Jennifer Franke, and Jose Ignacio Pascual — Institut für Experimentalphysik, Freie Universität Berlin, Berlin, Germany

Here we investigate the adsorption properties and growth of the Bechgaard salt TMTTF-TCNQ on a Au(111) surface by means of Low Temperature Scanning Tunneling Microscopy. TMTTF (tetramethyl-tetrathiafulvalene) is a charge donor and TCNQ (7,7,8,8- tetracyanoquinodimethane) is an acceptor. The bulk structure is formed by parallel chains of TMTTF and TCNQ, giving rise to one-dimensional conduction bands along the molecular rows. The electronic structure of TMTTF is essentially the same as the well known donor TTF, but the addition of the four methyl groups gives it more three-dimensional shape and increases the decoupling between the chains. The submonolayer growth of pure TMTTF on Au(111) shows a repulsive interaction between molecules as a consequence of its charged state [1]. On the contrary, pure TCNQ self-assembles in close-packed islands. When co-deposited on a metal surface, TMTTF and TCNQ show a strong tendency to mix in ordered domains with alternating rows of each molecule, similar to bulk. By Scanning Tunneling Spectroscopy we identify the molecular resonances of TMTTF and TCNQ and a depopulation of the surface state. Our data indicates that donor-acceptor interactions are still present on a metallic surface. [1] Torrente et al, Phys. Rev. Lett. 99, 176103 (2007)