Influence of seed layer thickness on well-aligned ZnO nanorods via hydrothermal method

Zinc oxide (ZnO) nanorods (NRs) were fabricated via the hydrothermal method at 90°C for 6 hour on the substrates with the ZnO seed layers. The ZnO seed layers had previously prepared at the different thickness, whose effects on the ZnO NRs were investigated. On the prepared ZnO samples, the morphologies and the crystal structures were examined by field-emission scanning electron microscopy and X-ray diffraction, respectively. The results show that the thickness of the seed layers directly affected on their crystallinity, the surface roughness and the ZnO NRs structures. From the hydrothermal process, the ZnO NRs grown on the seed layers with the smooth surface showed the well-aligned nanorod patterns. In addition, the growth rate of the ZnO NRs was also greatly affected by the seed layer thickness because of the corresponding surface energy. Finally, the optimizations of the uniformity and high aspect ratios of the ZnO NRs were carefully investigated and discussed.