Evolution of native point defects in ZnO bulk probed bypositron annihilation spectroscopy

This paper studies the evolution of native point defects withtemperature in ZnO single crystals by positron lifetime andcoincidence Doppler broadening (CDB) spectroscopy, combined with thecalculated results of positron lifetime and electron momentumdistribution. The calculated and experimental results of thepositron lifetime in ZnO bulk ensure the presence of zincmonovacancy, and zinc monovacancy concentration begins to decreaseabove 600,du annealing treatment. CDB is an effective methodto distinguish the elemental species, here we combine this techniquewith calculated electron momentum distribution to determine theoxygen vacancies, which do not trap positrons due to their positivecharge. The CDB spectra show that oxygen vacancies do not appearuntil 600,du annealing treatment, and increase with the increaseof annealing temperature. This study supports the idea that greenluminescence has a close relation with oxygen vacancies.