Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 40: Oxides and insulators
O 40.9: Vortrag
Donnerstag, 30. März 2006, 17:00–17:15, WIL A317
LASER DESORPTION OF METAL ATOMS BY SITE-SPECIFIC EXCITATION OF METAL OXIDE SURFACES — •Matthias Henyk1, Kenneth M. Beck1, Chongmin Wang1, Paolo E. Trevisanutto2, Peter V. Sushko2, Alexander L. Shluger2, and Wayne P. Hess1 — 1Pacific Northwest National Laboratory, EMSL, P.O. Box 999, Richland, WA 99352,USA — 2Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT,UK
Mg-atom emission is studied at MgO by using laser light tuned to excite specific surface sites at energies well below the excitation threshold of the bulk material. We find that at 4.66 eV laser excitation MgO nanocrystalline films and nanocube samples desorb neutral Mg-atoms with multi-modal distributions of kinetic energy (0.11, 0.18, 0.25 eV).Time-resolved desorption measurements reveal two distinct decay components (1.2, 100 ps) in addition to the typically observed coherence feature (80 fs, FWHM). These results are consistent with Mg-atom desorption driven by multiple electronic transitions,including an ultra-fast correlated 2-electron-transfer as well as the rapid decay of Mg+ surface states. Our ab initio calculations suggest an electron plus exciton mechanism, involving both excitation and trapping of electrons and surface excitons at 3-coordinated Mg surface sites. The proposed mechanism exemplifies a scheme of atomic scale modification of a metal oxide surface and can be useful for the further understanding of photo-induced desorption of more complex metal oxide materials.