Electron irradiation-induced defects in ZnO studied by positron annihilation

ZnO crystals were subjected to 3 MeV electron irradiation up to a high dose of 5.5 x 10(18)cm(-2). The production and recovery of vacancy defects were studied by positron annihilation spectroscopy. The increase of positron lifetime and Doppler broadening S parameter after irradiation indicates introduction of V-Zn, related defects. Most of these vacancies are annealed at temperatures below 200 degrees C. However, after annealing at around 400 degrees C, secondary defects are produced. All the vacancy defects are annealed out at around 700 degrees C. (c) 2006 Elsevier B.V. All rights reserved.