Formation of copper electrodeposits on an untreated insulating substrate

We report here the electrodeposition of copper on an insulating glass substrate without introducing additives into the electrolyte and/or metallic clusters on the surface of the substrate. The deposit morphology, which varies from compact film to dense-branching patterns, can be achieved by changing the concentration and pH of the electrolyte, and the electric current in electrodeposition. The grain size of the electrodeposits is analysed for various growth conditions. We find that finer copper grains can be easily achieved at large electric current, high pH and low electrolyte concentration. We explain, using the theory of nucleation, why a metallic layer may develop horizontally over an insulating glass plate.