Dresden 2009 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 2: Dielectric Spectroscopy & Microscopy
DF 2.2: Vortrag
Montag, 23. März 2009, 11:00–11:20, WIL A317
Oxygen Vacancies in Oxides Studied by Annihilation of Mono-Energetic Positrons — •Christoph Hugenschmidt1,2, Philip Pikart1,2, and Klaus Schreckenbach2 — 1ZWE FRM II, Technische Universität München, Lichtenbergstrasse 1, 85747 Garching — 2Physik-Department E21, Technische Universität München, James-Franck-Strasse, 85748 Garching
Oxygen vacancies play a fundamental role for the material properties of various oxides, e.g. charge carrier density in high-Tc superconductors, magnetic properties of diluted magnetic semiconductors or paramagnetic properties of SiO2. In this study, open volume defects in (metal) oxides are investigated by Doppler-broadening spectroscopy (DBS) of the positron annihilation. More detailed information about the chemical surrounding at the positron annihilation site is gained by additional coincident DBS experiments, where a signature of positrons annihilating with electrons from oxygen is observed. The mono-energetic positron beam at NEPOMUC [1] was used which allows depth dependent measurements, and hence the investigation of thin oxide layers. Recent results for metallic oxides such as ZnO are presented and compared with various non-metallic oxides such as amorphous and crystalline SiO2, oxygen terminated Si-surface, and ice. The role of neutral and charged oxygen vacancies and the application of the positron annihilation technique to study oxygen vacancies will be discussed.
[1] C. Hugenschmidt B. Löwe, J. Mayer, C. Piochacz, P. Pikart, R. Repper, M. Stadlbauer, K. Schreckenbach; Nucl. Instr. Meth. A 593 (2008) 616