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 44.65: Poster
Mittwoch, 28. März 2007, 17:00–19:30, Poster C
EELS investigations of surface color centers in BaO, SrO and lattice matched Ba0.7Sr0.3O on Si(001) — •Dirk Müller-Sajak and Herbert Pfnür — Leibniz-Universität Hannover, Institut für Festkörperphysik, Appelstr. 2, 30167 Hannover, Germany
We investigated the generation of color centers in ultrathin films of BaO and SrO on Si(001) by electron bombardment both as a function of electron energy and of exposure. Both materials grow nanocrystalline on this surface. In a second stage, lattice matched and crystalline layers of Ba0.7Sr0.3O on the same surface are investigated. Electron energy loss spectroscopy was used to identify the color centers formed. These color centers will finally be used as nucleation centers for metal wires and dots.
The dependence of cross sections in the energy range 30-100eV for color center generation on electron energy is compatible with a Knotek-Feibelman generation mechanism. Apart from energetic positions, decay processes and rate dependent behavior were investigated. By controlled oxygen exposure and their extinction as a function of exposure, these defects were clearly identified as oxygen vacancies. Two peaks with characteristic losses at 0.75 and 1.39 eV in the EELS spectra of electron bombarded BaO films decay with the same time constant. They were assigned to surface color centers. A third loss peak at 2.15 eV coincides with that bulk color centers. Correlations with structural properties of the films are discussed.