ELECTRODEPOSITION OF ZINC-COBALT ALLOYS - TAPPING MODE AFM TECHNIQUE APPLIED TO STUDY THE INITIAL-STAGES OF DEPOSITION

The first stages of electrodeposition of zinc-cobalt alloys on highly oriented pyre-graphite are studied by tapping mode atomic force micros copy (AFM), scanning electron microscopy, and electrochemical analysis . Low Zn(II)/Co(II) ratio (1/9) solutions are selected for this study. Potentiostatic deposition begins through the formation of randomly di stributed zinc-rich nuclei on the surface, showing exclusion areas aro und the larger nuclei and preferential nucleation at the kink sites. A t long deposition times an incipient dendritic growth, related to the intiation of pure cobalt deposition is observed. A simple AFM tip deco nvolution model is used to obtain the actual dimensions of both the ti p itself and the deposited nuclei. The nuclei growth mechanism observe s lateral diffusion and aggregation and the formation of emerging nucl ei on top of yet consolidated nuclei.