Effect of the cooling condition on the morphology and photoluminescence properties of ZnO nanostructures

Abstract

The cooling condition has a significant effect on the morphology and optical properties of ZnO nanostructures. In this study, four types of nail-shaped nanostructures were prepared by thermal evaporation of Zn powders under different cooling conditions, including natural cooling, vacuum cooling, rapid cooling and vacuum & rapid cooling. XRD results suggest that our samples are highly crystallized wurtzite ZnO with preferable c-orientation. XPS indicated vacuum and/or rapid cooling could reduce the oxygen vacancies in the surface of ZnO samples. PL spectra showed that the intensity ratio of UV to green emission was increased under vacuum and/or rapid cooling conditions, which was in agreement with the XPS results. We can control the tip morphology of ZnO nanostructures and oxygen vacancies on the surface by adjusting cooling conditions for different applications.