Investigation on chemical etching process of ZnO nanorods toward nanotubes

High-density vertically aligned ZnO nanotube arrays were prepared on ITO-coated glass substrates by a simple and facile chemical etching process from electrodeposited ZnO nanorods. The as-prepared nanotubes are single crystal, with hexagonal cross-section, a diameter of about 400 nm and a uniform central pore. Such ZnO nanotube arrays exhibited strong ultraviolet emissions at 372 nm at room temperature but negligibly defect-related visible emissions, indicating their high crystallinity and excellent optical quality. The nanotube formation was rationalized in terms of selective dissolution of the metastable Zn-rich (0 0 1) polar face. It was proposed that the diameters of the ZnO nanorods played a key role in the nanotube formation.