Hydrothermal growth of periodic ZnO nanorod arrays using polystyrene sphere templates

Zinc Oxide (ZnO) photonic crystals (PCs) are of great interest in recent years due to its potential applications in optoelectronic devices. However, most of the growth temperatures in fabricating ZnO nanostructures in periodic structures reported up to date are very high (>500°C), which is not favorable for low cost manufacture. In this work, a method involving low growth temperature (90°C), hydrothermal synthesis, was used to fabricate ZnO nanostructures. Self-assembly of polystyrene (PS) spheres was used to fabricate periodic arrays. PS spheres were self-assembled on the silicon (Si) or fluorine-doped tin oxide (FTO) substrate with ZnO seed layer derived from zinc acetate. After crosslinking the PS sphere layer, hydrothermal growth was performed. The influence of growth conditions (concentration, addition of PEI, etc.) on fabricated ZnO nanorod array has been studied. Then, PS spheres were removed by annealing in air, and fabricated ZnO nanorod arrays were studied by scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy. Periodicity of the array was strongly substrate dependent (better on Si than on FTO). Light emitting diodes were also fabricated in order to demonstrate the potential use of this ZnO periodic array.