Photoluminescence spectroscopy was used to study monocrystalline ZnO samples which had been annealed in inert, Zn-rich or O-rich atmospheres. A striking correlation was observed between the annealing ambient and the position of the deep band emission. In particular, annealing in O2 resulted in a deep band emission at 2.35eV, whereas annealing in the presence of metallic Zn resulted in a deep band emission at 2.53eV. The former band was attributed to VZn-related defects, and the latter to VO-related defects. Additional confirmation of the VO and VZn peak identifications came from the observation that the effect was reversible when O-rich and Zn-rich annealing conditions were switched. After annealing in the presence of ZnO powder, there was no sign of VZn- or VO-related bands, but a low-intensity yellow luminescence band was observed which peaked at 2.17eV and was probably related to Li; a common impurity in hydrothermally grown ZnO.

Identification of Oxygen and Zinc Vacancy Optical Signals in ZnO. T.M.Børseth, B.G.Svensson, A.Y.Kuznetsov, P.Klason, Q.X.Zhao, M.Willander: Applied Physics Letters, 2006, 89[26], 262112 (3pp)