A novel process of multi-annealing was proposed for forming well-arrayed ZnO nanostructures on asdeposited ZnO thin films that were prepared on quartz glass using a radio frequency (rf) magnetron sputtering at low temperature. It was found that the formation and morphology of ZnO nanostructures were strongly dependent on the reducing gas annealing processes. Oxygen ambient annealing between two reducing annealing processes had the effect of introducing more oxygen into the ZnO thin film, as well as improving the crystallinity of the ZnO nanostructures. An intense photoluminescence peak centered at 504 nm was observed in the wellarrayed ZnO nanostructures, due to the large amount of oxygen vacancies which existed on the larger surface area of ZnO nanostructures formed after the multiannealing processes at a low temperature of 430 ºC. These results show that multi-annealing processes are very effective in forming well-arrayed and controllable ZnO nanostructures.

ZnO thin films were deposited on quartz glasses by a radio frequency (rf) magnetron sputtering. The mechanism for stoichiometry in the ZnO thin films was investigated by adjusting Ar/O2 working gas ratio during deposition. The optical emission spectroscopy (OES) in situ measurement revealed the kinetics species variation during rf plasma deposition process. It was found that the intensity of the excited atomic oxygen (O*) was increased with the oxygen ratio increasing, resulting in enhancing the oxidization effect during ZnO film fabrication. On the contrary, the intensities of atomic zinc emission were gradually decreased, resulting in the zinc ratio in the film were decreased with the oxygen ratio increasing. Therefore, it is possible to control the stoichiometry of ZnO film by simply adjusting the working gas ambient in the rf plasma deposition. The structural and optical properties of ZnO thin films were investigated as well.