Room temperature ferromagnetism was observed in Li-N co-doped ZnO thin films [ZnO:(Li,N)] fabricated by plasma-assisted molecular beam epitaxy, and p-type ZnO:(Li,N) showed the strongest room temperature ferromagnetism. Positron annihilation spectroscopy and low temperature photoluminescence measurements indicate that the room temperature ferromagnetism in ZnO:(Li,N) was attributed to the defect complex related to VZn, such as VZn and Lii-NO-VZn complex, well supported by first-principles calculations. The incorporation of NO could stabilize and enhance the room temperature ferromagnetism of ZnO:(Li,N) by combining with Lii to form Lii-NO complex, which restrained the compensation of Lii for VZn and made the ZnO:(Li,N) conduct in p-type.

Evidence of Cation Vacancy Induced Room Temperature Ferromagnetism in Li-N Codoped ZnO Thin Films. Zhang, B.Y., Yao, B., Li, Y.F., Liu, A.M., Zhang, Z.Z., Li, B.H., Xing, G.Z., Wu, T., Qin, X.B., Zhao, D.X., Shan, C.X., Shen, D.Z.: Applied Physics Letters, 2011, 99[18], 182503