Ag/AgCl/KCl micro-electrodes as O2-insensitive reference tips for dynamic scanning Kelvin probe measurement

The metals commonly used as reference tip in scanning Kelvin probe (SKP) devices experience a change in their work function when initially present in inert atmosphere and then exposed to oxygen. This change in work function biases the signal measured on a substrate submitted to a variation in environmental O2 partial pressure and prohibits a wide range of kinetic investigations on reactional mechanisms involving oxygen. In this paper, reference probes based on the Ag/AgCl/KCl reference electrode structure are described and validated in regards to their use for SKP measurements in humid atmosphere. A validation example is presented where such a silver reference tip is used to measure on a gold substrate the potential change induced by introduction of oxygen in the investigation atmosphere.