Controlled c-oriented ZnO nanorod arrays and m-plane ZnO thin film growth on Si substrate by a hydrothermal method

Oriented ZnO nanorod arrays and ZnO thin films were simultaneously grown on magnetron sputtered ZnO seed layers through a hydrothermal approach without any metal catalyst. The c-oriented ZnO nanorod arrays were grown on the unannealed ultrathin ZnO seed layer, while the ZnO thin films with (1 0 0) preferred orientation were grown on the annealed ultrathin ZnO seed layer. Thermodynamically preferred (0 0 2) oriented grain growth will be suppressed by the morphology changes of the ultrathin seed layer while the (1 0 0) orientation will preferentially develop instead. Photoluminescence spectroscopy results show that the UV emission peak shifts slightly to shorter wavelength with increasing the annealing temperature of the ultrathin ZnO seed layer.