Effect of the O2/N2 ratio on the morphology of ZnO nanostructures grown by a thermal evaporation technique

ZnO nanostructures were synthesized by thermal evaporation of Zn powder in an oxygen and nitrogen gas environment at 1000 °C. No substrates or catalysts were used for the formation of the ZnO nanostructures. The ZnO nanostructures were synthesized inside crucibles with Zn source powder. ZnO nanoneedles began to be found at O₂/N₂ ratios of less than 60/40. As the O₂/N₂ ratio increased to 80/20, the ZnO nanostructures mainly grew in the longitudinal direction. Upon increasing the O₂/N₂ ratio to 100/0, the ZnO nanostructures grew mainly in the transverse direction. CL spectra showed that ZnO with a high crystalline quality was obtained at a O₂/N₂ ratio of 80/20.