Electrodeposition of Pb on n-Si(111)

Electrodeposition of lead was studied in the system n-Si(lll)/Pb2+, ClO4-, H+ using cyclic voltammetry, chronoamperometry, ex situ optical microscopy and in situ scanning probe microscopy (SPM). Comparative studies were also performed in the system HOPG(0001)/Pb2+, ClO4-, H+. No underpotential deposition (UPD) of 2D Pb phases could be observed in the investigated systems indicating a weak substrate-deposit interaction. In both systems Pb deposition occurs in the overpotential range (OPD) via a 3D island growth on an unmodified substrate according to the Volmer-Weber growth mechanism. At relatively low overpotentials the electrodeposition reaction is mainly initiated on substrate surface inhomogeneities such as steps. The initial deposition kinetics in the OPD range is controlled by a progressive nucleation on active sites and a hemispherical diffusion towards the growing Pb clusters. The nucleation rate and the number of atoms in the critical cluster (nucleus) are determined from the analysis of the kinetic data. Results are compared with previous data for 3D Pb phase formation on UPD modified silver single crystal substrates. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.