Influence of vacancy defects on the electronic structure and magnetic properties of Cu-doped ZnO monolayers: A first-principles study

The development of available electronic structures and magnetism has received considerable interest for ap-plications in nanoelectronic and spintronic devices. In this paper, we investigated the electronic and magnetic properties of Cu-doped defective ZnO monolayers by first-principles calculations. The results demonstrate that the formation energies of the V-O + nCu(Zn) complex under Zn-rich conditions are lower than those under O-rich conditions. However, the formation energies of the V-Zn + nCu(Zn) complex under O-rich conditions are lower than those under Zn-rich conditions. Furthermore, the Cu dopant and vacancies both play an important role in the contribution of the magnetic moment. The total magnetic moments of the Cu2Zn14O15 monolayers remain at 1.822-1.868 mu B, and the average local magnetic moment is approximately 0.439-0.443 mu(B) per Cu atom. The magnetic moments of the O atoms close to the Cu atom are 0.124-0.163 mu(B) per O atom. The magnetic moments of the V-O + nCu(Zn) complexes satisfy the odd-even doping rule, and the V-O + nCu(Zn) complexes undergo a transition from NM to FM with increasing Cu concentration. For the V-Zn + nCu(Zn) complex, the total magnetic moments increase monotonically with an increase in the number of Cu atoms. The absolute value of total magnetic moment of the CuZn14O16 monolayer is 0.225 mu(B), which is contributed by the Cu dopant (0.433 mu(B)), as well as the nearest O atoms around the Cu dopant. Furthermore, the combined effect of defect vacancy and Cu dopant could tune the ZnO monolayer from a direct semiconductor to an indirect semiconductor and even regulate the band gap. These findings are potentially useful for nanoelectronic and spintronic applications.