Improvement in the Grain Growth of Plasma-Treated Nano-Sized ZnO Films and Their Characterization

The well-aligned ZnO nanorods were rapidly grown on an indium tin oxide (ITO)-coated glass substrate using Al-doped ZnO (AZO) thin film as seed layer by the microwave-assisted hydrothermal chemical route. The optimal growth conditions for the well-aligned ZnO nanorods were obtained by modulating H2 plasma pretreatment time for the seed layer and synthesis time for ZnO nanorods. The H2 plasma effect of the seed layer on the alignment, growth rate and crysallinity of ZnO nanods is also demonstrated. The synthesized ZnO nanorods were annealed in atmosphere of N2, O2 and H2 + N2 mixed gas to improve the related physical characteristics, the ZnO nanorods on grapheme/ITO substrate were also investigated. The results show that the alignment and growth rate of ZnO nanorods depends on the physical characteristics and roughness of the seed layer, which can be improved by H2 plasma pretreatment. The average growth rate of ZnO nanorods synthesized by microwave hydrothermal technique is about 2.2 μm/hr which significantly superior to other conventional techniques. After the appropriate N2 annealing treatment, good quality and well-aligned ZnO nanorods, which are single crystal with stacking defects and pyramid or candle shape, were obtained. A fundamental model of the effect of H2 plasma pretreatment on the surface of seed layer and the growth of ZnO nanorods using a microwave-assisted hydrothermal chemical route is also described.