Applied Optics

Combined optical second harmonic generation/quartz crystal microbalance study of underpotential deposition processes: Copper electrodeposition on polycrystalline gold

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Optical second harmonic generation and quartz crystal microbalance techniques are used as in situ probes of copper underpotential deposition on polycrystalline gold surfaces in sulfuric acid electrolyte. The second harmonic signal from a polished bulk gold substrate is observed to decrease by >60% as a result of copper underpotential deposition on gold. Also, the mass of an underpotentially deposited copper adlayer is monitored in situ by an oscillating quartz crystal microbalance, yielding an estimated coverage of ˜8.0 X 10-10 mol cm-2 and an electrosorption valency of 1.5 for a copper adlayer on the surface of vapor-deposited polycrystalline gold. © 1990 Optical Society of America.