Electrodeposition of granular Cu-Co alloys

Electrodeposition characteristics of Cu-Co films were studied for the formation of heterogeneous alloys for giant magnetoresistance applications. In situ scanning tunneling microscopy, Auger electron spectroscopy (AES), and high resolution scanning electron microscopy studies showed that rough films with a low concentration of cobalt [Cu92.5-Co7.5] (atom %) were deposited mainly due to a higher deposition rate of copper than of cobalt toward the end of the deposition process, and due to the formation of copper grains after the electrodeposition process by chemical exchange between copper ions in the solution and with the cobalt in the deposit. AES analysis revealed that the Cu-Co film is not homogeneous; the bulk of the film is richer in Co while the surface and the bottom of the film are Co-poor. X-ray diffraction showed that the electrodeposition is a topotaxial crystallization process and that the as-deposited film is composed of two phases, a solid solution of face centered cubic Cu-Co with preferred orientation of {111} planes, and a hexagonal close packed Co phase. Scanning electron microscopy micrographs and energy dispersive spectroscopy indicated the segregation of cobalt grains resulting from thermal treatments, according to the phase diagram of Cu-Co.