Electrodeposition of Cu from acidic sulphate solutions in the presence of polyethylene glycol and chloride ions

A surface-enhanced Raman scattering (SERS) spectroelectrochemical investigation has been carried out during Cu electrodeposition from an acidic sulphate solution in the presence of Polyethylene glycol (PEG) and chloride ions. PEG-related bands are clearly visible at the open circuit potential (OCP) and during the electroplating process, showing that the polymer is stably adsorbed on the Cu surface in a wide cathodic potential window. Our experimental range was limitated by the occurrence of fluorescence at potentials more cathodic then -200 mV versus Ag/AgCl, indicating the formation of fluorescent species by electrodic reaction. A tentative reactivity scheme for PEG is provided. The co-adsorption of chloride and sulphate species from copper (II) sulphate and sulphuric acid was highlighted as well.