Conversion process of ZnO nano-/micro-rods into nano-/micro-tubes and cathodoluminescence characterization

A simple two-steps method has been successfully developed to synthesize ZnO nanotubes. The alkaline etching process was investigated in detail using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of ZnO nanotube structures was due to the preferential dissolution of the defect-rich top (polar) faces. Cathodoluminescence (CL) was performed on both top and side surfaces of the ZnO tubes. Only the near-band-edge UV emission was observed, implying that the as-grown ZnO nanotubes have a very low concentration of defects. This CL result also provides evidence for explanation of ZnO tubular structure growth.