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Thermal desorption spectroscopy; X-ray photoelectron spectroscopy; Infrared absorption spectroscopy; V2O3(0 0 0 1)/Au(1 1 1); V2O3(0 0 0 1)/W(1 1 0); Water; Thin films; Phonons; Electronic structure; Adsorption
Abstract:
V2O3(0001) films have been grown epitaxially on Au(111) and W(110). Under typical UHV conditions these films are terminated by a layer of vanadyl groups as has been shown previously [A.-C. Dupuis, M. Abu Haija, B. Richter, H. Kuhlenbeck, H.-J. Freund, V2O3(0001) on Au(111) and W(110): growth, termination and electronic structure, Surf. Sci. 539 (2003) 99]. Electron irradiation may remove the oxygen atoms of this layer. H2O adsorption on the vanadyl terminated surface and on the reduced surface has been studied with thermal desorption spectroscopy (TDS), vibrational spectroscopy (IRAS) and electron spectroscopy (XPS) using light from the BESSY II electron storage ring in Berlin. It is shown that water molecules interact only weakly with the vanadyl terminated surface: water is adsorbed molecularly and desorbs below roorn temperature. On the reduced surface water partially dissociates and forms a layer of hydroxyl groups which may be detected on the surface up to T similar to 600 K. Below similar to 330 K also co-adsorbed molecular water is detected. The water dissociation products desorb as molecular water which means that they recombine before desorption. No sign of surface reoxidation could be detected after desorption, indicating that the dissociation products desorb completely.
