Using a hydrothermal synthesis method, zinc oxide (ZnO) nanowires (NWs) have been grown on ZnO/Au/Ti/Si substrates. This method shows a low temperature (70 °C) approach for growing ZnO NWs on a ZnO seed layer. ZnO films of about 50 nm thickness were deposited by radio frequency (RF) magnetron sputtering at various sputtering powers (150, 100 and 65W). The formation of ZnO seed layers and ZnO NWs was clarified using X-ray diffraction (XRD), and the surface microstructure of the prepared ZnO NWs and ZnO films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. The results show that the growth behavior of ZnO NWs is strongly impacted by the sputtering power of ZnO seed layers. The decrease of RF sputtering power leads to a diminution in the grain size of ZnO seed layers and a smaller lattice mismatch between seed layers and NWs, thus inducing a morphological improvement and a better alignment of the obtained ZnO NWs. These works aim at optimizing the integration of ZnO NWs for mechanical energy harvesting applications, and to enhance the performance of such piezoelectric devices.