Homogeneity of amorphous GdCo films prepared by bias sputtering

Abstract

In preparing amorphous Gd–Co films by dc‐ and rf‐bias sputtering, systematic variations are found of the composition both in the direction of the film normal and in the film plane. Therefore, the bias sputtering process is analyzed in terms of a simple mass balance model. The formation of a target surface layer whose composition depends on the sputtering yields of Co and Gd and on the bias voltage can lead to the growth of a Co‐enriched initial layer in the film. The homogeneity in the film plane is determined by the radial variation of the transfer coefficient and of the ion current density at the substrate. The composition distribution in the plane is found to be different for dc‐ and rf‐bias sputtering due to different influences of the bias voltage on the ion currents.