Role of surface states in electrodeposition of Pb on n-Ge(111)

The influence of surface states on the kinetics of the initial stages of Pb electrodeposition on n-Ge(111) was studied by cyclic voltammetric and current transient measurements. The substrate surface was modified to n-Ge(111)H or n-Ge(111)OH applying appropriate experimental and polarization routines. In transient experiments, the driving force for nucleation, the supersaturation, was varied by both changing the electrode potential U at c Pb 2+ =const and the concentration c Pb 2+ at U=const. The results obtained indicate that, under the experimental conditions used, the nucleation site density N 0 remains constant with the electrode potential and thus, does not influence the initial nucleation kinetics. The nucleation rate, the density of nucleation sites and the number of atoms N crit in critical nuclei were obtained analyzing current transients on the basis of models for instantaneous and progressive nucleation. Nucleation kinetics were found to be more inhibited on n-Ge(111)OH. The experimental results show that the different nucleation behavior of H- and OH-terminated n-Ge(111) surfaces can be explained by different densities of Ge surface free radicals acting as nucleation sites. Problems connected with an application of electrodeposition for metallization of micro- and nanostructures are discussed.