Structure, X-ray photoelectron spectroscopy and photoluminescence properties of highly ordered ZnO microrods

ZnO microrods were grown by aqueous bath synthesis at 90 °C and annealed at 400 °C in air. Both scanning electron micrographs and X-ray diffraction patterns indicate that the ZnO microrods are wurtzite crystallographic phase with metastable (0 0 2) preferred orientation. X-ray photoelectron spectroscopy spectra show that Zn 2p and O 1s spectra mainly originate from the Zn2+ and O2− ions in Zn-O bonds, respectively. Photoluminescence spectra of ZnO microrods are dominated by outstanding ultraviolet (UV) emission bands, which are attributed to the first, the second or the third longitudinal optical phonon replicas of free-exciton (EFX) emission. The degeneration of (0 0 2) crystalline planes causes the intensity decline and the redshift of UV emission peaks in the ZnO microrods.