Kinetic Monte Carlo Simulation of Underpotential Deposition of Cu on Au(111)

The electrochemical deposition of metals on foreign substrates is a complex process which includes a number of phase formation phenomena. The first step of the electrodeposition of a metal(Me) on a foreign substrate(S) is the formation of single Me-adatoms. The adatom-substrate(Me-S) binding energy and the misfit between the crystal lattices of the foreign substrate and the deposit are the most important factors determining the mechanism of the subsequent 2-D and 3-D phase formation processes. In experiments there are electrodes attached to the substrate, providing electrical potential to assist the deposition. A simple physical consideration tells that if the binding energy of Me-adatms on the foreign substrate(Ψ M e−S) is much lower than the adatom binding energy on the own substrate(Ψ M e−M e), the formation of the 3-D Me-bulk phase in over-potential deposition(OPD) range(the electrode potential E is negative to the value E M e/M e z+ which characterizes the equilibrium between the 3-D Me-bulk phase an the elec-trolyte) takes place at relatively low adatom concentrations according the well known " island growth " mechanism independent of the deposit-substrate crystallographic misfit. However, if Ψ M e−S >> Ψ M e−M e , one or several Me-monolayers can be adsorbed in the so-called under-potential deposition(UPD) range(E > E M e/M e z+).