The evolution of native point defects with temperature in single crystals was studied using positron lifetime and coincidence Doppler broadening spectroscopy, combined with the calculated results of positron lifetime and electron momentum distribution. The calculated and experimental results of the positron lifetime in bulk ZnO ensured the presence of the zinc monovacancy, and the zinc monovacancy concentration began to decrease above 600C annealing treatment. Coincidence Doppler broadening was combined with calculated electron momentum distributions in order to determine the oxygen vacancies, which did not trap positrons due to their positive charge. The coincidence Doppler broadening spectra showed that oxygen vacancies did not appear until 600C of annealing treatment, and increased with increasing annealing temperature. This study supported the idea that green luminescence had a close relationship to oxygen vacancies.

Evolution of Native Point Defects in ZnO Bulk Probed by Positron Annihilation Spectroscopy. Peng, C.X., Wang, K.F., Zhang, Y., Guo, F.L., Weng, H.M., Ye, B.J.: Chinese Physics B, 2009, 18[5], 2072-7