Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 21: Adsorption an Oberfl
ächen II
O 21.6: Vortrag
Dienstag, 25. März 2003, 16:15–16:30, HSZ/03
Photon stimulated desorption of halogens from silicon surfaces — •J. I. Flege1, Th. Schmidt2, J. Falta2, G. Materlik3, M. Çakmak4, and G. P. Srivastava5 — 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg — 2Inst. f. Festkörperphysik, Universität Bremen, Postfach 330440, D-28334 Bremen — 3Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK — 4Departement Natuurkunde, 3001 Leuven, Belgium — 5School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
The phenomenon of x-ray photon stimulated desorption (XPSD) is presently not very well understood in detail. Specifically, the determination of the adsorption sites of the desorbate and the corresponding desorption mechanisms is a challenging task. In this contribution, investigations of halogen-terminated silicon surfaces with x-ray standing waves (XSW) and XPSD are presented. For the model system Cl/Si(111), an extensive study employing XSW, x-ray photoemission spectroscopy and scanning tunneling microscopy leads to the identification of minority sites as the desorption-active sites for positive chlorine ions. For Br/Si(111) an analoguous feature is observed for the desorption of Br+ ions, while in the case of Cl/Si(001) the Cl+ desorption is dominated by the majority sites. For each system, the prevailing contribution to the total positive ion yield is shown to stem from direct desorption processes triggered by the initial creation of core holes in the adsorbate atoms. Furthermore, structural models derived from the XSW experiments are compared to results obtained from ab initio calculations based on density functional theory for each adsorbate system.