The Role of Benzotriazole in Electrodeposition of Cu1-xNix Alloys (0.05 < x < 0.15) on Cu and Ni Substrates

We investigated the benzotriazole enabled growth of low Ni content (5–15 at.%) CuNi alloy deposits by characterisation of its morphology and elemental composition as a function of substrate metal (Cu and Ni), charge density, current density, and potential-time response measured during electrodeposition. Alloy deposition starts in favor of Cu, forming a Cu-rich layer on a Ni substrate and Cu-rich islands on a Cu substrate after which aggregates only form on a Cu substrate, due to the ability of benzotriazole (BTAH) to chemically bond to Cu but not to a Ni surface. Furthermore, Ni deposits preferably on grain boundaries, BTAH gets incorporated in the deposit and forms a thin layer between the Cu substrate and the alloy deposit. Based on our findings a growth model for BTAH enabled CuNi growth is proposed which describes that the BTAH working mechanism is twofold. First, the additive shifts the onset potential of Cu2+ reduction closer to the Ni2+ reduction potential by forming a chemisorbed BTAH layer, thereby enabling Cu and Ni co-deposition and, secondly, during deposition it specifically interacts with Cu, thus inhibiting Cu dendrite formation.