Berlin 2005 – scientific programme

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DS: Dünne Schichten

DS 24: Postersitzung II

DS 24.2: Poster

Tuesday, March 8, 2005, 17:00–19:00, Poster TU B

Surface optical anisotropy induced by water molecules adsorbed on Si(001): First-principles calculations — •Kaori Seino and Wolf G. Schmidt — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743 Jena, Germany

Water is a major component in the residual gas in most ultra-high vacuum apparatus. Water coadsorption therefore occurs on many Si(001) surfaces to a noticeable degree. The interaction of water with Si(001) surface has also been discussed in the context of type-C defects on Si(001) surfaces. Here we present reflectance anisotropy spectra (RAS) for water covered Si(001) surfaces calculated within the independent particle approximation. We mainly discuss two configurations: the dissociative adsorption (i.e. the formation of HO-Si-Si-H) and the oxygen insertion into the Si dimer (i.e. the formation of H-Si-O-Si-O). For low coverages we find essentially an attenuation of the RAS features typical for clean Si surfaces. For the saturation coverage of one molecule per dimer, however, dissociative adsorption and oxygen insertion into the Si dimer give rise to clearly different optical anisotropies.