Electrochemical studies on the deposition process of electroless CoNiP films with graded magnetic properties

In order to clarify the origin of the graded magnetic properties by the substrate rotational speed for electroless CoNiP films, electrochemical characteristics such as mixed potential and polarization behaviors were investigated. The results of mixed potential analysis revealed that the cathodic and anodic partial reactions in this system were diffusion- and reaction-controlled state, respectively. It was shown that the mixed potential of the CoNiP deposition with the substrate rotational speed was dominated mainly by the deposition reaction of Co. The results of the polarization curves for each metal ion clarified that the Co deposition is in the diffusion-controlled state, whereas such a tendency did not appear for the deposition of Ni. This suggests that such a difference in deposition behaviors between Co and Ni with respect to the rotational speed of the substrate results in the formation of graded film properties.