Temperature dependence and decay times of zinc and oxygen vacancy related photoluminescence bands in zinc oxide

A photoluminescence study was performed at different temperatures on bulk ZnO samples annealed in zinc- and oxygen-rich atmospheres. The different annealing conditions create oxygen and zinc vacancies in a controlled way in the ZnO samples. These defects are both involved in the deep band emission (DBE) that is often observed in ZnO but exhibit different optical characteristics promoting defect identification. In particular, when decreasing the PL measurement temperature the energy peak position of the V-O-related band decreases while that of V-Zn increases. Secondly, phonon replicas are clearly observed in the DBE spectra in the sample containing V-Zn. Finally, the characteristics of the DBE decay time for V-Zn- and V-O-enriched samples are also different. Specifically, for the V-Zn-enriched sample the decay curves show strong wavelength dependence and generally slower decay components as compared to the sample enriched with V-O. (C) 2007 Elsevier Ltd. All rights reserved.