Surface states induced by metal atoms at the Si/electrolyte interface

Abstract

Metal atoms have been chemically deposited on n-Si and p-Si and the obtained deposits have been characterized with Auger electron spectroscopy. The obtained samples have been used as electrodes in acetonitrile electrolyte. The electrochemical studies heve been performed using classical current-voltage, impedance and Schottky-Mott measurements, and also subgap photocurrent spectroscopy of the surface states. It appears that the deposited metal atoms do induce surface states on the silicon surface. These surface states have a weak effect on the flatband potential (i.e. no strong pinning of the Fermi level is observed even for monolayer coverage) but the subgap photoyield is increased by several orders of magnitude. The shape of the quantum yield versus photon energy curve points to surface states widely distributed through the bandgap. These experiments finally confirm the ability of the subgap photocurrent technique to distinguish between the two kinds of optical processes that may occur between the surface states and the semiconductor bands.