Effect of ZnS/C Mass Ratio on the Morphologies and Luminescence Properties of ZnO Nano/Microstructures Synthesized via Thermal Evaporation of ZnS and C Powder Mixtures

Abstract

ZnO nano/microstructures were grown via a simple thermal evaporation process in air at atmospheric pressure. Mixtures of ZnS and carbon powders were used as the sources. The effects of growth temperature and mass ratio of carbon powder to ZnS on the morphologies and luminescence properties of the ZnO nano/microstructures were investigated in this study. When the growth temperature was 1000 ^oC, ZnO nanowires with a hexagonal wurtzite crystal structure started to be formed and were preferentially grown along the [0001] direction. As the temperature increased to 1200 ^oC, the crystal growth in the lateral direction perpendicular to the [0001] direction was enhanced, which resulted in a decreasing aspect ratio of the onedimensional ZnO nanowires. When source powders with different mass ratios of ZnS:C=2:1, 1:1 and 1:2 were used to grow ZnO nano/microstructures at 1200 ^oC, ZnO microrods with wurtzite crystal structure were formed in all the samples. As the mass ratio of carbon powder to ZnS increased, the aspect ratio of ZnO microrods was reduced, which suggests that the carbon powder enhanced the growth of ZnO microrods in the lateral directions. A strong ultraviolet emission band centered at 380 nm was observed in the ZnO nano/microstructures synthesized using the source powders with the mass ratios of ZnS:C=1:1 and 1:2, indicating that the ZnO nano/microstructures had a high crystalline quality.