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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.76: Poster

Monday, March 26, 2007, 17:30–20:30, Poster C

Adsorbate Induced Modifications of SiC Surfaces studied by High Resolution Electron Energy Loss Spectroscopy — Maxim Eremtchenko, Rolf Öttking, Jens Uhlig, Anita Neumann, •Syed Imad-Uddin Ahmed, and Juergen A. Schaefer — Institut für Physik und Institut für Mikro- und Nanotechnologien, Technische Universität Ilmenau, P.O. Box 100565, 98684 Ilmenau, Germany

Silicon carbide (SiC) is a wide band gap semiconductor that is suited for high power, high temperature and high frequency applications in which surface and interface chemical reactivity need to be thoroughly understood. For this material, we are able to monitor changes in carrier concentration profiles and band bendings owing to the C- and Si-terminated cubic and hexagonal SiC as well as vibrational properties of atmospheric adsorbates like, for e.g, oxygen, by comparing HREELS-data with simulations based on dielectric theory. The surface state density is directly related to the type of reconstruction and surface composition and plays an important role in correlation with the substrate temperature. In particular, on 6H-SiC (0001), we observed for the first time new vibrational modes, which can be identified with distinct Si-O-Si vibrations, namely its asymmetric- and symmetric stretching vibrations and its wagging motion. In particular, the energy and intensity of the asymmetric stretching frequency is strongly dependent upon oxygen coverage and substrate temperature, analogous to the situation of initial stage oxidation of Si surfaces.

We acknowledge financial support by the Deutsche Forschungsgemeinschaft - DFG under grant Scha 435/17-1.