Regensburg 2000 – scientific programme

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O: Oberflächenphysik

O 11: Postersession (Eröffnung)

O 11.129: Poster

Monday, March 27, 2000, 19:00–22:00, Bereich C

Directional Preference in Particle Motion: Selftrapping of Vacancies in an ordered Adsorbate Layer — •P. Jakob, M. Gsell, and D. Menzel — Physik-Department E20, Technische Universität München, D-85747 Garching

Using STM, single vacancies within the dense Ru(001)-(2x2)-3O layer are found to display highly directional diffusion characteristics that leads to a self-trapping of this quasi-particle to within three neighboring sites. While a high mobility within these few sites is found, vacancy diffusion across the surface is very slow (ratio > 1000:1). The nonzero motion of the entire triangular unit proceeds in the usual stochastical way and demonstrates that intrinsic structural defects of the substrate lattice are not involved in the self-trapping process. It is shown that the observed motional constraint is due to the local symmetry of the oxygen adsorption sites which implies a directional dependence of diffusion barriers within the (2x2) unit cell.