Electrochemical/chemical synthesis of highly-oriented single-crystal ZnO nanotube arrays on transparent conductive substrates

Arrays of ZnO nanotube (ZNT) were prepared by a two-step electrochemical/chemical process on a transparent, conductive substrate from an aqueous solution at 85 °C. The as-grown ZNTs are single crystals with wurtzite structure and have good crystalline state. The tubular morphology was formed by the proton generated from anodic splitting of water and defect-selective etching of the electrodeposited ZnO nanorod (ZNR) along the c-axis. The photoluminescence and cathodoluminescence spectra of the ZNT arrays show two emission bands located in the ultraviolet (UV) and visible region, respectively. It was found that the PL intensity in the UV band as well as the ratio of Iuv/Ivisible increased with increasing of the excitation intensity.