Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 32: Oxides and Insulators: Clean Surfaces

O 32.2: Vortrag

Dienstag, 26. Februar 2008, 13:15–13:30, MA 042

Structure determination of clean V₂O₃(0001) and TiO₂(110) surfaces — •Werner Unterberger¹, Emily A. Kröger¹, Tsenolo J. Lerotholi², Francesco Allegretti², David I. Sayago¹, Matthew Knight², and Phillip Woodruff^1,2 — ¹Fritz-Haber-Institute — ²Physics Department, University of Warwick

Scanned-energy mode photoelectron diffraction (PhD) is a well-established method to determine quantitatively the local structure of adsorbates at surfaces. Here we describe its application to the clean surfaces of TiO₂(110) and thin epitaxial films of V₂O₃ on Pd(111).

For V₂O₃(0001) key questions are termination and relaxation of the clean surface; current understanding is based only on theoretical calculations and STM imaging. While the PhD technique is more naturally suited to studies of adsorbate structures, here we report its application to the clean surfaces of V₂O₃ and TiO₂. The TiO₂(110) surface is in principle well-known, and so provides a valuable test of the methodology, although the sign and magnitude of the relaxation of the bridging O atoms has been the subject of recent controversy. The PhD analysis for this surface yields relaxation parameter values in good agreement with the most recent results giving some confidence in the method. For the V₂O₃(0001) surface the results clearly favour the "half-metal" termination with a strongly relaxed outermost layer, as found in published theoretical total energy calculations. However, the PhD results prove inconclusive regarding the presence or absence of surface vanadyl (V=O) species favoured by theory.