Self-seeded electrochemical growth of ZnO nanorods using textured glass/Al-doped ZnO substrates

In this work, large and dense arrays of zinc oxide (ZnO) nanorods (NRs) were fabricated by an improved template-free electrodeposition (ECD) route on top of home-made Al-doped ZnO (AZO) thin films deposited on glass. The AZO layer, acting as transparent conducting oxide, was found to display enhanced electrical and morphological properties compared to other commercially available substrates, facilitating the subsequent electrochemical growth of the ZnO nanostructures. In addition, its intrinsic columnar nature strengthened the vertical orientation of the obtained ZnO NRs. The one-step low-temperature electrochemical method did not require any additional seeding layer, being suitable for applications in which the process simplicity and substrate's thermal toughness are essential requirements. The ECD protocol was optimized as a function of the process temperature and duration, demonstrating the possibility to yield reasonable aspect-ratio ZnO NRs in a relatively short time synthesis. Further structural studies confirmed the excellent orientation along c-axis of the ZnO Wurtzite phase and have shown a polycrystalline nature of the NRs, with a well-defined hexagonal symmetry of the crystallites.