Growth of ZnO nanorod arrays by hydrothermal method using homo-seed layers annealed at various temperatures

Vertically arrayed ZnO nanorods were synthesized by a hydrothermal method on homo-seed layers deposited using a sol-gel process and heat-treated at various temperatures ranging from 400 to 700 °C in air. The effect of the annealing temperatures on nanorod formation was investigated. With increasing temperature, the microstructure of the ZnO seed layers changed from nanocrystals to coarse polycrystals with a preferred orientation, which led to an increase in the length and diameter of the hydrothermally grown nanorods. The ZnO nanorods, based on a solution process, exhibited deep-level emission in the orange- red region related with hydroxyl group reactions, while the thermally treated seed layers showed oxygen vacancy-related emission.