Electrodeposition of copper on a copper single crystal (111) face in the presence of chloride ions

Observations were made of copper electrodeposited on to the (111) plane of copper from a highly purified solution of copper sulphate containing known concentrations of HCl (from 10^-10 to 10^-1 mol/l concentration of chloride ions). In the presence of HCl, triangular and hexagonal pyramids change to layers and then to a polycrystalline deposit. At higher concentrations of HCl, precipitation of cuprous chloride occurs in the form of triangular pyramids. The transition from triangular and hexagonal pyramids to layers and then to a polycrystalline deposit occurs at all current densities used, but the critical concentration of HCl for the transition depends upon the current density.