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(Pb2+) = const and the concentration c(Pb2+) at U = const. The results obtained indicate that, under the experimental conditions used, the nucleation site density No 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(I I I)-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. (C) 2001 Elsevier Science Ltd. All rights reserved.