Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Oxides and insulators: Adsorption II

O 45.2: Vortrag

Mittwoch, 16. März 2011, 11:30–11:45, WIL C307

On the influence of molecular symmetry on surface diffusion — Tobias Sonnleitner, Ingmar Swart, •Niko Pavliček, Andreas Pöllmann, and Jascha Repp — Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany

Symmetries govern many fields of physics and chemistry. In the case of molecules adsorbed on single-crystal surfaces the symmetry of the combined adsorbate-substrate system is decisive for its properties. For example, in spectroscopy symmetry arguments are the basis of many selection rules. However, in diffusion there do not exist such things as selection rules that completely forbid certain diffusion steps. This raises the question how big structural differences that reduce the symmetries have to be, in order to have a significant influence on the surface-potential landscape.

Here, we address the issue of how diffusion of molecules is influenced by the molecular symmetry in a systematic manner using a scanning tunneling microscope. To this end, we investigated π-conjugated molecules for which four symmetry distinct isomers exist on an insulating surface. Despite minute changes in the molecular structure in such a weakly interacting system we find that the surface-potential landscape is governed by the molecular symmetry. Indeed, the four isomers exhibit four distinctly different diffusion patterns, as evidenced by diffusion movies.