Effect of electric field and postgrowth annealing on the morphology and crystallinity of hydrothermally grown ZnO nanostructures

ZnO nanorods and microrods are synthesized on an Si (1 0 0) substrate by hydrothermal treatment (HTT). The influence of electric field on the hydrothermal growth process of ZnO was investigated, which has not been reported previously. By applying a dc electric field, ZnO nanorods are found to disappear, and a new shape of amorphous ZnO nanostructures is observed. The ion exchange mechanism is used to explain the growth of ZnO rods. After postgrowth annealing in air, the morphologies and structures of the ZnO rods changes, and the length to diameter ratio of ZnO nanorods decreases.