Evidence of cation vacancy induced room temperature ferromagnetism in Li-N codoped ZnO thin films

Room temperature ferromagnetism (RTFM) was observed in Li-N codoped ZnO thin films [ZnO:(Li, N)] fabricated by plasma-assisted molecular beam epitaxy, and p-type ZnO:(Li, N) shows the strongest RTFM. Positron annihilation spectroscopy and low temperature photoluminescence measurements indicate that the RTFM in ZnO:(Li, N) is attributed to the defect complex related to V-Zn, such as V-Zn and Li-i-NO-V-Zn complex, well supported by first-principles calculations. The incorporation of NO can stabilize and enhance the RTFM of ZnO:(Li, N) by combining with Li-i to form Li-i-NO complex, which restrains the compensation of Li-i for V-Zn and makes the ZnO:(Li, N) conduct in p-type. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3657412]