Regensburg 2002 – scientific programme
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M: Metallphysik
M 17: Diffusion und Punktdefekte II
M 17.6: Fachvortrag
Wednesday, March 13, 2002, 18:15–18:30, H6
Detection of vacant sites on the two sublattices of electron irradiated SiC by two-detector-Doppler broadening techniques — •A. A. Rempel1,2, K. J. Reichle1, K. Blaurock1, W. Sprengel1, and H.-E. Schaefer1 — 1Institut of Theoretical und Applied Physics, Stuttgart University, 70550 Stuttgart, Germany — 2Institute of Solid State Chemistry, Russian Academy of Sciences, Ekaterinburg, Russia
In the present study vacancies on the two sublattices of SiC as selectively induced by electron irradiation are specifically identified by coincident Doppler broadening and positron lifetime spectroscopy. Coincident measurements of the Doppler broadening of the electron-positron annihilation γ spectrum were performed with a collinear set-up of two high-purity Ge detectors. The vacancies induced by 230-350 keV electrons are characterized by Si nearest neighbors, as deduced from the increased annihilation probability with Si core electrons. These vacancies are therefore located on the C sublattice. They exhibit a positron lifetime of 153 ps as suggested theoretically. In contrast to that, the vacancies which trap positrons after 500 keV electron irradiation are found to be surrounded by carbon nearest neighbor atoms and are, therefore, located on the Si sublattice with a substantially higher positron lifetime of 176 ps. The techniques employed here may be of more general relevance for the site detection of vacancies in ordered lattices, the study of order-disorder transformations or the investigation of the atomic environment of free volumes in, e.g. interfaces.