Two-dimensional angular correlation of annihilation radiation and coincidence Doppler broadening of annihilation radiation measurements were performed on electron-irradiated n-type 3C-SiC in which isolated Si vacancies were responsible for positron trapping. After irradiation, the intensity of the coincidence Doppler broadening spectrum increased and decreased in low- and high-momentum regions, respectively. These features were explained by a theoretical calculation considering Si vacancies. The central region of the 2-dimensional angular correlation of annihilation radiation spectra became isotropic after irradiation, while the overall anisotropies extending within the Jones zone were conserved suggesting that isolated Si vacancies had tetrahedral symmetry, as expected from a previous electron spin resonance study.

Electron-Positron Momentum Distributions Associated with Isolated Silicon Vacancies in 3C-SiC. A.Kawasuso, M.Yoshikawa, H.Itoh, T.Chiba, T.Higuchi, K.Betsuyaku, F.Redmann, R.Krause-Rehberg: Physical Review B, 2005, 72[4], 045204 (6pp)