Tunable growth of urchin-shaped ZnO nanostructures on patterned transparent substrates

We report well-defined and uniform hollow urchin-shaped zinc oxide (ZnO) nanostructures on a micro-patterned transparent substrate by the process of electrochemical deposition. The thin aluminum-doped ZnO (AZO) film was completely covered on the patterned sapphire substrate by radio frequency (RF) magnetron sputtering method, serving as both a good seed layer and a transparent conductive oxide layer. The AZO-coated on the patterned transparent substrate provides the particular electric field distribution as well as the periodically arranged three-dimensional structures to integrate the ZnO nanorod arrays (NRAs), which forms various hollow urchin-shaped ZnO nanostructures by controlling the applied cathodic voltage and growth time. In comparison with ZnO NRAs on the AZO-coated flat sapphire substrate, furthermore, the improved crystallinity and photoluminescence property were clearly observed. Additionally, the hollow urchin-shaped ZnO nanostructures enhanced the light scattering property due to the higher order diffractions induced by the combination of the micro-grating structure with a period larger than the incident light wavelength and the wide bending angle of ZnO NRAs. These novel ZnO architectures can be very useful for multi-functional nano-device applications including photovoltaic and optoelectronic devices.