ZnO nanocrystals grown by chemical solution deposition were studied by means of photoluminescence and cathodoluminescence spectroscopy. A postgrown annealing treatment significantly improved the UV emission efficiency and resulted in the clear appearance of a low temperature emission band around 3.31 eV (so-called A-line). Spatially and wavelength resolved cathodoluminescence measurements revealed a spotlike distribution of the A-line emission on a nanocrystal surface. It is found that there is a strong correlation between the emission around 3.31 eV and the specklike defects on the nanocrystal surface that appeared after annealing. The origin of the A-line and the specklike defects are discussed.

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ZnO nanocrystals grown by chemical solution deposition have been annealed in ambient air using heat and cw He-Cd laser treatments. Both annealing processes increased markedly the visible luminescence intensity. The obtained results indicate that annealing under laser illumination results in effects comparable to those of high temperature annealing.