Morphology and luminescence properties of ZnO micro/nanostructures synthesized via thermal evaporation of Zn-Mg mixtures

ZnO crystals with various morphologies were synthesized by thermal evaporation of Zn/Mg mixtures under air atmosphere. When Zn powder was used as a source material, ZnO crystals had a tetrapod morphology. Depending on the mass ratio of Mg to Zn in the source material, ZnO crystals were synthesized having wires, tubes and grain-like morphologies. This provides strong evidence that Mg had an important effect on the morphology of the ZnO crystals and that the ratio of Mg to Zn is critical to the changes in morphology of the ZnO crystals. All the ZnO crystals had a wurtzite crystallographic structure. The possible role of Mg in the growth of the tubular-shaped ZnO crystals was discussed. Two emission peaks at around 380 (ultraviolet) and 510 nm (green) were observed in the cathodoluminescence spectra. A high intensity ratio of ultraviolet emission to green emission was observed for the tubular-shaped ZnO crystals, indicating the high crystalline quality of the ZnO crystals.