Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Metal Substrates: Adsorption of Organic/Bio Molecules I

O 8.2: Talk

Monday, February 25, 2008, 12:15–12:30, MA 041

Island formation and diffusion of PTCDA on Ag(100) surface — •Julian Ikonomov, Oliver Bauer, and Moritz Sokolowski — Institut für Physikalische und Theoretische Chemie, Universität Bonn

Perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) forms a c(8×8) ordered structure with a high symmetry on Ag(100). For submonolayers the attractive interactions between the molecules lead to two-dimensional islands with a quadratic equilibrium shape. The ordered PTCDA islands are in equilibrium with a disordered two-dimensional gas-like phase, consisting of highly mobile molecules. The dynamic behavior of this system was studied by variable temperature scanning tunneling microscopy. At room temperature, the islands were found to grow preferentially at the lower side of substrate steps, while at lower sample temperature, they grow on the terraces. At temperatures of about 680 K, a phase transition to a fully disordered phase was observed. The island decay and the diffusion of the PTCDA molecules were quantitatively investigated in order to obtain surface related energies and the diffusion parameters. Funded by the DFG SFB 624.