Microphotoluminescence investigation on single ZnO microrods with different morphologies

Spatially resolved microphotoluminescence (μ-PL) was employed to investigate the photoluminescent properties of single ZnO microrods with three morphologies: fusiform, straight, and dumbbell. The morphology of ZnO microrods as well as the measurement region, both had great influence on the observed μ-PL. These were analyzed in terms of the defect density, the ionization effect of surface charges, and the thermal effect of laser. It was found that crystal defects favored the formation of bound excitons, which resulted in the redshift of ultraviolet bands in μ-PL. This redshift effect, however, could be submerged by the ionization of the bound excitons under the surface electric field, especially at the large surface-to-volume regions. The thermal effect of laser, an important factor for traditional photoluminescence characterization, can be neglected in the case of single rod μ-PL measurement.