Effects of annealing temperature and dopant concentration on the structure, optical, and magnetic properties of Cu-doped ZnO nanopowders

摘要

This study analyzed the effects of annealing temperature and dopant concentration on the structural, optical, and magnetic properties of Cu-doped ZnO nanopowders. Cu-doped ZnO nanopowders were prepared using a solid-state reaction method. The X-ray diffraction results demonstrated that the Cu ions successfully substituted the Zn ions in the hexagonal wurtzite structure of the ZnO nanoparticles. Ultraviolet-visible spectroscopy measurements revealed that the band gap decreased due to the incorporation of Cu. The photoluminescence results showed that the intensity of the emissions increased with doping and decreased as the annealing temperature (T_A) increased, which can be attributed to the increase and decrease of the oxygen vacancies (V_O), respectively. The magnetic properties of the ZnO nanopowders were also found to be affected by Cu doping and T_A. The ferromagnetic behavior of the ZnO nanopowders decreased as both the doping concentration and T_A increased. This behavior can be explained by the increase in the antifer-romagnetic superexchange interaction along with Cu doping due to the decrease in the distance between the Cu ions and the decrease in V_O, respectively. Thus, the results indicate oxygen stoichiometry and V_O both play a dominate role in the room temperature ferromagnetic response of ZnO nanopowders.