Room-temperature ferromagnetism in p-type nitrogen-doped ZnO films

Ferromagnetism in p-type N-doped ZnO films, deposited on (0001) sapphire substrates by radio frequency (rf) reactive magnetron sputtering at different N2/O2 ratios, has been observed at room temperature. Both the p-type conduction and ferromagnetism are originated from the substitution of O with N. At the N2/O2 ratio of 15:15, the film displays the maximum hole density and the minimum resistivity as well as the maximum Ms. The transition from n-type to p-type strongly depends on both the substitutional nitrogen on the oxygen site (NO) and oxygen vacancy (VO) concentrations. The observed ferromagnetism of p-type ZnO:N films is intrinsic and strongly related to both the NO and VO content and can be interpreted by the bound magnetic polarons (BMPs) model.