Regensburg 2000 – wissenschaftliches Programm
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M: Metallphysik
M 7: Atomare Fehlstellen
M 7.7: Vortrag
Dienstag, 28. März 2000, 12:15–12:30, H6
Specific search for lattice vacancies on various sublattices in SiC and WC by positron lifetime and coincident Doppler broadening. — •A.A. Rempel1,2, M.A. Müller1, K. Reichle1 und H.-E. Schaefer1 — 1Univ. Stuttgart, Inst. f. Theor. u. Angew. Physik, 70550 Stuttgart, e-mail: rempel@itap.physik.uni-stuttgart.de — 2Institute of Solid State Chemistry, Russian Academy of Sciences, Ekaterinburg 620219, Russia, rempel@ihim.uran.ru
Vacancies on the two sublattices in 6H-SiC single crystal and hexagonal WC polycrystal were studied by means of coincident Doppler broadening and positron lifetime after irradiation by electrons of various energies. By employing both techniques simultaneously vacancies are detected by the trapping of positrons and their chemical neighborhood studied by measuring the core electron momentum distribution via coincident Doppler broadening.
By these techniques the positron lifetimes of 158 and 210 ps in electron-irradiated silicon carbide can be attributed to C and Si vacancies, respectively, and the positron lifetimes of 136 and 175 ps in electron-irradiated tungsten carbide to C and W vacancies, respectively. The electron momentum distribution of core electrons in unirradiated SiC and WC shows, that positrons are annihilated mainly with electrons of Si or W which exhibiting positron lifetimes of 146 and 124 ps, respectively.
(Financial support by DFG-SPP-322-1037 and RFBR-98-03-32856a.)