Theoretical Investigations of the Defect Structure for Ni~(3+) in ZnO

摘要

The defect structure for Ni~(3+) in ZnO crystal is theoretically investigated using the perturbation formulas of the spin Hamiltonian parameters for a 3d~7 ion in trigonally distorted tetrahedra. In view of the significant covalency of the system due to the high valence state of Ni~(3+) , the ligand orbital and spin-orbit coupling contributions are taken into account in a uniform way based on the cluster approach. The impurity Ni~(3+) is found not to occupy the ideal Zn~(2+) site in ZnO but to undergo the small axial displacement of about 0.044 A away from the oxygen triangle along the C_3 axis. The theoretical spin Hamiltonian parameters based on the above impurity displacement show good agreement with the experimental data. The defect structure of this impurity center is compared with that for the similar Fe~(3+) in ZnO.