Fe-N thin films were fabricated using a direct current magnetron sputtering process assisted by a radio-frequency (rf) field. The effect of the rf field on the phase composition of the films was investigated. The results indicate that with the assistance of the rf field, various kinds of iron nitrides can be obtained in the films, including alpha'-Fe-N, alpha"-Fe16N2, xi-Fe2N, epsilon-Fe3N, and gamma"-FeN with ZnS structure. It was found that the rf field greatly benefits the formation of iron nitrides in the Fe-N films. (c) 2006 American Vacuum Society.