Distance tunnelling characteristics of solid/liquid interfaces: Au(111)/Cu²⁺/H₂SO₄

Abstract

This study examined the liquid part of solid/liquid interfaces at the atomic level. By measuring distance tunnelling characteristics the height of the potential barrier between the tip and the sample, i.e., the potential energy field the tunnelling electrons are exposed to, can be obtained, and this provides direct access to double layer properties. We found exponential IS-characteristics for the bare and the oxidised Au(111) surface, while non-exponential behaviour was obtained in the presence of ordered adlayers. The influence of the local environment just within the Helmholtz layer is strong enough to perturb the tunnelling process significantly. The electrolyte properties in the Gouy region do not change with electrode potential, the liquid in the tunnelling gap has only an average effect by lowering the barrier height.