The influence on intensity ratio of peak emission between recombination of free-excitons and deep-defect for ZnO nanostructure evolution from nanorods to nanotubes

Zinc oxide (ZnO) nanorods are grown by a hydrothermal method. The morphology was changed from nanorod to nanotube via a well-controlled chemical aqueous etching process with appropriate amount potassium chloride (KCl). SEM analyses show that the ZnO nanorods can be changed to nanotubes when the chemical etching process was adopted with appropriate KCl concentration and etching time. Uniform ZnO nanotube can be achieved formed when the ZnO nanorods were immersed in 4M KCl aqueous with 13 hrs. The luminescence character of nanorods and nanotubes were investigated by the temperature dependence photoluminescence spectra. Two peaks (excitonic peak and deep level emission) were observed in both morphologies. However, the excitonic peak intensity (EI) and defect related emission peak intensity (DI) ratio of ZnO nanotubes increase when the etching time increases. The intensity ratio variation of EI to DI maybe can be attributed to the surface state of ZnO are increased and oxygen defects of ZnO are decreased in the etching process. The potential application of ZnO nanotubes is demonstrated.