First-principles plane-wave pseudopotential calculations were conducted to investigate Co impurities and native defects associated with O excess in ZnO. The electronic states and formation energies were evaluated by using the total energies of super-cells. The electronic states indicated that Co impurities were donor-like, while native defects associated with O excess were acceptor-like. Among the native defects, Zn vacancies were likely to be a dominant species in view of the much lower formation energy than those of the others. Calculations for Co impurity-Zn vacancy complexes implied that Co impurities stabilized Zn vacancies and hence an O excess in their vicinities.

First-Principles Calculations of Co Impurities and Native Defects in ZnO. F.Oba, T.Yamamoto, Y.Ikuhara, I.Tanaka, H.Adachi: Materials Transactions, 2002, 43[7], 1439-43