Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 14: Poster session I (Adsorption, Epitaxy and growth, Phase transitions, Surface reactions, Organic films, Electronic structure, Methods) (sponsored by Omicron Nanotechnology GmbH)

O 14.35: Poster

Montag, 27. März 2006, 18:00–21:00, P2

Model reaction studies on ultra-thin vanadium oxide films on Pd(111) — •Markus Kratzer and Adolf Winkler — Institute of Solid State Physics, Graz University of Technology, A-8010 Graz

We have investigated the permeation/desorption of deuterium and the water production via reaction of permeating deuterium with gas phase oxygen on specifically prepared vanadium oxide films on Pd(111). Auger spectroscopy and LEED has been used to analyse and characterise the ultrathin vanadium oxide films. It is known that 0.3 ML of vanadium evaporated under oxygen atmosphere produce a stable (2x2) honeycomb like vanadium oxide film of V₂O₃ stoichiometry [1]. This unconventionally coordinated structure has been assumed to exhibit interesting catalytic properties. In this work we have focused on the translational energy distribution of the associatively desorbing deuterium and the water reaction product, using a time-of-flight spectrometer. The deuterium supply proceeds via permeation through a Pd(111) single crystal. On the clean Pd(111) surface both the desorbing deuterium molecules and the water molecules exhibit a thermalised kinetic energy distribution. On the Pd(111) surface covered with a (2x2) V₂O₃ film, however, desorbing deuterium shows a slightly translationally cooled energy distribution under reaction conditions. This demonstrates that the permeating/resurfacing D atoms with higher kinetic energy react preferentially with oxygen to D₂O, rather than to recombine with another D atom.

[1] S. Surnev et al., Surf. Sci. 495 (2001) 91 This work has been supported by the Austrian Science Fund, Project S9006-N02