Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 44: Poster Session II (Semiconductors; Oxides and Insulators: Adsorption, Clean Surfaces, Epitaxy and Growth; Surface Chemical Reactions and Heterogeneous Catalysis; Surface or Interface Magnetism; Solid-Liquid Interfaces; Organic, Polymeric, Biomolecular Films; Particles and Clusters; Methods: Atomic and Electronic Structure; Time-resolved Spectroscopies)
O 44.2: Poster
Mittwoch, 28. März 2007, 17:00–19:30, Poster C
Electron Induced Desorption of Water on Ruthenium(0001) — •Franziska Traeger, Deler Langenberg, YouKun Gao, and Christof Wöll — Physikalische Chemie 1, Ruhr-Universität Bochum, Universitätsstr. 150, 44801 Bochum
When electrons impinge on adsorbed water molecules, desorption, dissociation or structural phase transitions may occur. The system water/Ru has been found to be particularly sensitive, as structures with varying coverage and similar energies have been observed, some of them stabilized by dissociation products (OH and H). In this work the influence of electrons on the adsorbate D2O/Ru has been investigated by the diffraction of a neutral He atom beam. Without electron impact a high order commensurate structure with 27.3 Å periodicity is found, in contrast to LEED experiments. These results can be explained in terms of a bilayer with slightly larger lattice constant than the bulk ice and which is rotated by 4.7∘ with respect to the substrate [1]. In further experiments electrons were accelerated with 1000-1200 V onto the surface. The observed changes in the specular He signal and in the He diffraction pattern strongly indicate, that at larger coverages desorption is the dominant mechanism. A quantitative analysis of the He intensity gives a desorption probability of about 0.7 % per electron. Several models for the analysis and their errors are presented. Finally, the results are discussed in comparison with electron induced desorption from the multilayer D2O/Ru and from ice surfaces.
[1] F. Traeger, D. Langenberg, Y.K. Gao and Ch. Wöll, submitted to Phys. Rev. Lett.