Influence of organic additives on electrodeposition of Co–Cu alloys from sulphate bath

Abstract

In this work, the authors report on the influence of additives on the onset of deposition, the current efficiency (CE) and the nucleation growth mechanism of Co–Cu alloys electrodeposited on n-Si(100) substrate from sulphate solution with an addition of sodium citrate (SC) and citric acid (CA). The study was carried out by means of cyclic voltammetry, chronoamperometry methods using the Scharifker–Hills model for the determination of nucleation and growth mechanism and some kinetic parameters for nucleation. The CV curves indicate that the deposition potential of Cu(II) is shifted to more negative potentials while additive anion is added in the solution. Also, the results show that the additives do not improve the CE. For all baths, electrodeposited Co–Cu alloy follows instantaneous nucleation and three-dimensional (3D) diffusion limited growth. The nucleation density in the solutions without additive and with SC increases exponentially with the potential whereas in solution containing CA additive, it is no longer possible to consider exponential increase, indicating the existence of a reaction in addition to the 3D nucleation mechanism in the Co–Cu electrodeposition process.