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 18.5: Poster

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

Adsorbate induced refacetting: Pb chains on Si(557) — •Annemarie Schuster, Marcin Czubanowski, Shima Akbari, Herbert Pfnür, and Chistoph Tegenkamp — Leibniz Universität Hannover, Institut für Festkörperphysik, Appelstr. 2, 30167 Hannover

The adsorption of monolayers (ML) of Pb on Si(557) followed by annealing to 640K results in the formation of an atomic wire structure. Recently performed transport measurements have shown, that below 78K only along the wires transport occurs, whereas in the perpendicular direction an insulating behavior is found [1]. This finding depends sensitively on the Pb chain structure. Therefore, we have investigated the structure on the atomic and mesoscopic scale by high-resolution low energy electron diffraction (SPA-LEED). Depending on Pb coverage in the range between 1.2 and 1.6ML, formation of various facets [(112), (335), (223)] is induced by the Pb layers, in agreement to recent STM results [2]. The facet orientation in general does not coincide with the macroscopic orientation of the (557) surface. After an initial annealing step to 600 K, starting with 1.2ML of Pb, this new vicinality can be tuned gradually and reversibly even at temperatures below 180K by further adsorption, but also by desorption of Pb. Superstructures of the Pb layers on the terraces were identified on the most stable (223) facets, showing a correlation of adjacent terraces. Here parts of the devil's staircase and the striped-incommensurate (SIC) phases known from Si(111) surfaces develop [3]. [1]C. Tegenkamp et.al. PRL 95 (2005) 176804 [2] H. Murikawa et.al. PRB 76 (2007) 165406 [3]Yakes et.al. PRB 69 (2004) 224103