Platinum Deposition onto Si Single Crystal Surfaces I. Chemical, Electronic, and Morphological Surface Processes under Depletion Conditions

Abstract

The initial stages of Pt electrodeposition from solutions on Si(111) surfaces were investigated by standard electrochemical techniques and atomic force microscopy. It was found that under depletion conditions the reduction of Pt species shows a potential dependence that results from the discharging of surface states. The Pt deposition rate increases with the surface state density. Injection of holes from the redox level leads to formation of an ultrathin silicon oxide layer, which takes place simultaneously as a chemical process. Capacitance–voltage measurements show that the potential-dependent Pt deposition increases the concentration of surface states, related to the solvolytic oxidation of Si surface defect sites. The topographical analysis of the surface shows initial Pt deposition on the tips of atomic terraces that extends to deposition along step edges for higher coverage. Also, step bunching is observed with a step height increase to 2–5 nm.