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Screening Effects in Probing the Electric Double Layer by Scanning Electrochemical Potential Microscopy

R.F. Hamou[1], P.U. Biedermann[1], A. Erbe[1], and M. Rohwerder[1]
[1]Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

A computational method is developed to study probing the electric double layer by Scanning Electrochemical Potential Microscopy. The model is based on a modified Poisson- Boltzmann equation, which takes into account steric effects. We investigated the effect of metallic apex protrusion and the Open Circuit Potential (OCP) of the tip on the probed potential. A clear electrostatic screening effect was observed when varying the OCP of the probe. Steeper potential profiles were noticed for high OCPs, which is due to screening effect. The dependence of the measured potential on the metallic apex shape was also observed.