Defect emissions in ZnO nanostructures

TLDR

Defects in three types of ZnO nanostructures were studied before and after annealing under various conditions. Annealing atmosphere and temperature strongly influence yellow and orange‑red defect emissions, while green emission remains largely unchanged; emissions also depend on temperature and excitation wavelength, with yellow emission in hydrothermal samples attributed to OH groups and green/orange‑red emissions arising from donor‑acceptor transitions involving defect complexes, including zinc vacancy complexes.

Abstract

Defects in three different types of ZnO nanostructures before and after annealing under different conditions were studied. The annealing atmosphere and temperature were found to strongly affect the yellow and orange-red defect emissions, while green emission was not significantly affected by annealing. The defect emissions exhibited a strong dependence on the temperature and excitation wavelength, with some defect emissions observable only at low temperatures and for certain excitation wavelengths. The yellow emission in samples prepared by a hydrothermal method is likely due to the presence of OH groups, instead of the commonly assumed interstitial oxygen defect. The green and orange-red emissions are likely due to donor acceptor transitions involving defect complexes, which likely include zinc vacancy complexes in the case of orange-red emissions.