The formation of patterns of electrochemical deposits in an ultra-thin layer of CuSO4 solution

The mechanisms governing pattern formation and selection are important scientific issues for non-equilibrium interfacial growth. In this article, an experimental study of electrochemical deposition was carried out in an ultra-thin layer of CuSO4 solution. Using an unique experimental setup, the convectional interferences in the deposit growth process are effectively restrained. Subjected to different growth driving forces (deposition current), the deposits aggregating in the forms of microcrystalline and nanocrystalline Cu and Cu2O exhibit film and branching morphologies respectively. In particular, the lower the driving force, the larger the width of the deposit and meanwhile the probability of forming film like or finger like morphology becomes great. Whereas in case of high driving force, the deposits turn to be tenuous and appear in quasi-linear filaments arrays due to the growth competition between the adjacent branches. Based on the morphological analysis of deposits, the processes of the nucleation and aggregation for the microcrystallines were deduced. In addition, the effects of electrical migration and diffusion of the Cu2+ cations in the growth front were discussed.