Ga-assisted synthesis and optical properties of ZnO submicron- and nanotowers.

Tower-like ZnO submicron- and nanostructures were synthesized by simply evaporating a mixture of Zn and Ga. Scanning electron microscopy and transmission electron microscopy observations showed that the regular hexagonal tower-like structure is likely to be made up in a layer-by-layer fashion and consist of sheets. According to our experiments, the amount of Ga has a large effect on their morphologies. The growth of such tower-like structures is ascribed to the vapor-solid mechanism. The introduction of Ga hinders the growth of ZnO along the [0001] direction, resulting in the formation of the novel tower-like structures. In addition, the photoluminescence of such structures shows a strong green-light emission.