Properties of Co-N, Co-Fe-N, and Co-Zr-N films prepared by rf sputtering in nitrogen-argon gas mixtures

The structure and properties of Co-N, Co-Fe-N, and Co-Zr-N films, prepared by rf reactive sputtering using nitrogen and argon gases, have been studied. The resistivity and coercivity of Co-N, Co-Fe-N, and Co-Zr-N films were determined as a function of nitrogen partial pressure. It was found that the properties of Co-N and Co-Fe-N films were very similar where the properties were determined mainly by the nitride phases in these films. The resistivity of both Co-N and Co-Fe-N films increased with the increase of nitrogen pressure. The coercivity of both films decreased with an initial increase of nitrogen pressure, then increased with a further increase of pressure so that there is a region of nitrogen pressures where the coercivity is at its lowest value. The low coercivity is attributed to the formation of the Co4N phase in Co-N films and both Co4N and Fe4N phases in Co-Fe-N films. For Co-Zr-N films, resistivity first decreased with an increase of nitrogen pressure, then increased with a further increase of pressure, indicating the presence of a Zr-N phase in these films. The coercivity increased with an increase of nitrogen pressure. The Zr-N phase was not observed in the x-ray diffraction measurements due to the low concentration of Zr in these films.