Electrodeposition of lead was studied in the system n-Si(111)/Pb2+, ClO4
ÿ, 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
ÿ, 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 unmodi®ed 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 di€usion 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 modi®ed silver single crystal
substrates. # 1998 Published by Elsevier Science Ltd. All rights reserved

electrodeposition, semiconductors, phase formation