Microwave assisted synthesis of flower-like ZnO and effect of annealing atmosphere on its photoluminescence property

Large scale flower-like ZnO microstructures were synthesized by microwave assisted hydrothermal method in short reaction time. These flower-like structures were composed of dozen of rods like building block units radiated from a centre. Similar morphology was not obtained in normal hydrothermal method. TEM microscopy study showed that individual rods of flower-like structures are single crystalline in nature and preferentially grown along [0001] direction. Growth mechanism showed that microwave induction and ethylenediamine (EDA) played an important role in the formation of flower-like ZnO microstructures. Photoluminescence property of flower-like ZnO microstructures showed deep level emission along with UV emission which indicates the presence of structural defects. The nature of defect responsible for deep level emission was examined by annealing the sample in different atmospheres. There was no significant effect of annealing the sample in air and argon atmospheres however in hydrogen atmosphere deep level emissions were passivated.