Unexpected positive role of oxygen vacancies in Na-doped ZnO

The interaction of Na impurities and O vacancies (VO) in ZnO was studied in theory and experiment. The VO facilitated substitutional Na (Na-Zn/Na-Zn(-)) acceptors with inhibiting interstitial Na (Na-i/Nai+) donors, which may benefit the p-type conductivity. The formed (Na-Zn-V-O)(+/0) complexes induced the change of band structures of ZnO, with the broadening of gap energies and disappearance of the V-O(2+)-related impurity level, which confirmed by the blue shift of the nearband-edge (NBE) UV emission and the decay of the visible emission in PL spectra. The strong and dominant NBE UV emission suggested acceptable luminescence behaviors of Na-doped ZnO. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768279]