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 curr ent transient measurements. The substrate surface was modified to n-Ge(111) -H or n-Ge(111)-OH applying appropriate experimental and polarization routi nes. In transient experiments, the driving force for nucleation, the supers aturation, was varied by both changing the electrode potential U at c(Pb2+) = const and the concentration c(Pb2+) at U = const. The results obtained i ndicate that, under the experimental conditions used, the nucleation site d ensity 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 instantan eous and progressive nucleation. Nucleation kinetics were found to be more inhibited on n-Ge(I I I)-OH. The experimental results show that the differe nt nucleation behavior of H- and OH-terminated n-Ge(111) surfaces can be ex plained by different densities of Ge-. surface free radicals acting as nucl eation sites. Problems connected with an application of electrodeposition f or metallization of micro- and nanostructures are discussed. (C) 2001 Elsev ier Science Ltd. All rights reserved.