Electrochemical deposition of silicon from a sulfolane-based electrolyte: effect of applied potential

As a low-cost, non-volatile, highly polar and chemically stable solvent, sulfolane has a high implementation potential for electroplating in organic media. This is the first report of the electrodeposition of silicon from sulfolane-based electrolytes. Voltammetric and chronoamperometric techniques, coupled with a quartz crystal microbalance, have been used to perform and characterize the process. Resonance frequency, f, damping, w, and apparent molar mass, Mapp are used as sensitive parameters for the evaluation of the silicon layer formation. Si electrodeposition displays a strong dependence on the applied potential. Close to theoretical values for Mapp and minimal w are observed at low deposition overpotentials, which allow an in situ quantitative mass evaluation. At higher overpotentials the process efficiency decreases due to simultaneous electrolyte decomposition. The electrodeposition of elemental Si (approx. 60% of the entire Si content) is evidenced by X-ray photoelectron spectroscopy. Additionally, the formation of a binary metal compound with the Cu substrate might be a key factor in the very good adhesion and mechanical stability of the layer.