Positron Annihilation Study Of Defects In Electron-Irradiated Single Crystal Zinc Oxide

Pressurized melt grown zinc oxide (ZnO) single crystals purchased from Cermet Inc. were irradiated by 2MeV electrons with fluence of 6x10(17) cm(-2). Isochronal annealing from 100 degrees C-800 degrees C was performed on the crystals under argon and air ambience. Variable Energy Doppler Broadening Spectroscopy (VEDBS) was carried out on both the as-grown and the irradiated samples at each annealing step. The migration, agglomeration and annealing of grown-in and irradiated-introduced defects were studied. It was observed that the grown-in vacancy-type defects concentration decreased at 300 degrees C and 600 degrees C. For the irradiated sample annealed in argon, the positron trapping vacancy-type defect concentration decreased at 300 degrees C and 600 degrees C. Further annealing the as-grown and irradiated samples in argon increased the S parameter further. For the irradiated sample annealed in air, the vacancy-type defect concentration decreases at 300 degrees C and 700 degrees C.