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O: Fachverband Oberflächenphysik
O 5: Nanostructures at Surfaces I (Wires, Tubes)
O 5.3: Talk
Monday, March 26, 2007, 11:45–12:00, H36
Topography and valencebandstructure of dysprosium-silicide on Si(557) — •Karolin Löser, Martina Wanke, Gerd Pruskil, and Mario Dähne — Institut für Festkörperphysik, Technische Universität Berlin, D-10623 Berlin
Rare Earth silicide structures on silicon are of special interest because of their extremely low Schottky barrier on Si(111) and the formation of nanowires on Si(001). Here we report on the self-assembled formation of dysprosium-silicide nanostructures on Si(557), which we investigated by high-resolution scanning tunneling microscopy and angle-resolved photoelectron spectroscopy. The formation of the different structures depends mainly on the dysprosium coverage less on the annealing temperature in the range of 600-750∘C. Looking at the atomic structure we found three different types of nanostructures. Nanowires similar to those on Si(001) form for a coverage of 0.5 Å. At a coverage of 1,0 Å there is a 5×2-chain structure like that of Gd on vicinal Si(557). At higher coverages more than 3000 Å long and 50-100 Å wide structures form. These consist of DySi2 with a 1×1 reconstruction for coverages around 2,0 Å, while they consist of √3 × √3 reconstructed DySi1.7 for higher coverages. Both structures are known from the Si(111) surface. Our investigations by angle-resolved photoelectron spectroscopy verified these findings. The DySi2 and DySi1.7 structures are characterized by a two-dimensional electronic structure. In contrast, an anisotropic metallicity was found at low coverages for the nanowires and the 5×2-chain structure. This project was supported by DFG, project number DA 408/11.