Deconvoluted coincidence Doppler broadening spectroscopic measurements were performed on 300keV and 1.7MeV electron-irradiated SiC. Lower-energy irradiation produced only C vacancies, while a higher energy produced both C and Si vacancies. This distinction was clearly seen in the high (20 to 35mrad) momentum range, where an atomic signal of Si was seen for the C vacancy. In addition to the higher-momentum region, the higher resolution of the deconvoluted coincidence Doppler broadening spectra revealed structural information related to the crystal lattice. The autocorrelation function obtained for positrons trapped at C vacancies was found to show a stronger lattice signal indicative of a more extended positron wave function and a less strongly bound state. Conversely that positron trapped at the silicon vacancy showed a more damped autocorrelation function characteristic of a more spatially confined positron state.

Silicon and Carbon Vacancies in Silicon Carbide Studied by Coincidence Doppler Broadening Spectroscopy. J.D.Zhang, C.C.Cheng, C.C.Ling, C.D.Beling, S.Fung: Physica Status Solidi C, 2007, 4[10], 3676-9