Defects in 3 different types of ZnO nanostructure, before and after annealing under various conditions, were studied. The annealing atmosphere and temperature were found to affect strongly the yellow and orange-red defect emissions, while the green emission was not significantly affected by annealing. The defect emissions exhibited a strong dependence upon the temperature and excitation wavelength, with some defect emissions being observable only at low temperatures and for certain excitation wavelengths. The yellow emission in samples prepared by using a hydrothermal method was suggested to be due to the presence of OH groups, rather than the commonly cited interstitial O defect. The green and orange-red emissions were thought to be due to donor-acceptor transitions involving defect complexes, and which probably included Zn-vacancy complexes in the case of orange-red emissions.

Defect Emissions in ZnO Nanostructures. A.B.Djurisic, Y.H.Leung, K.H.Tam, Y.F.Hsu, L.Ding, W.K.Ge, Y.C.Zhong, K.S.Wong, W.K.Chan, H.L.Tam, K.W.Cheah, W.M.Kwok, D.L.Phillips: Nanotechnology, 2007, 18[9], 095702 (8pp)