Conversion of ZnO microrods into microdisks like structures and its effect on photoluminescence properties

ZnO microstructures were synthesized by the hydrothermal method. Scanning electron microscopy (SEM) revealed the formation of ZnO microrods in absence of trisodium citrate and hexagon-shaped ZnO microdisks in presence of trisodium citrate. The length and width of ZnO microrods were 3-5 μm and 500 nm-1 μm, respectively and they were tapered at both ends, whereas ZnO microdisks were 1-2 μm in diameter. Crystal growth mechanism suggested that citrate suppressed the growth of ZnO along c-axis which resulted into the formation of microdisks like structure. Photoluminescence (PL) spectroscopy showed a weak ultraviolet (UV) and strong green emission in ZnO microrods but a strong UV and very weak green emission in ZnO microdisks. It was suggested that the green emission in ZnO microrods was due to structural defects present at polar planes which was reduced in microdisks with reduction in polar planes.