Electrochemical growth process of Zn-Co alloys with different crystalline structures

Abstract

This work presents a study of the nucleation and growth of Zn-Co films produced by electrochemical deposition on Cu substrates. Using potentiostatic deposition at –1.4 V (vs. Ag/AgCl), both crystalline and amorphous structures were obtained by controlling the metallic ions concentrations in the electrolyte. The deposits are crystalline when Zn ions are predominant in the solution and tend to be amorphous when Co ions are in the far majority in the solutions. The process can be classified as anomalous deposition, and it is deeply affected by the initial number of electroactive sites for nucleation, which is much larger for Zn than Co. The electrodeposition has been analyzed with both static and rotating disk electrodes. The models of Scharifker-Hills and Koutechký-Levich were used in the analysis for current-time transients, and current versus the electrode rotating velocity, respectively. The results permit the inference of multi-step mechanisms for the reduction and deposition of the ions. An alternative approach with two Scharifker-Hills curves for the current-time transients is presented. Furthermore, images from scanning electron microscopy and samples composition were evaluated throughout the deposition process.