Voltage noise across a metal/metal sliding contact as a probe of the surface state

Abstract

We report a complete experimental study and a physical modelling of the long-term evolution of the main electrical properties of a metal ring/wire sliding contact, the wire, and the ring being coated with a thin Au film. The long-term evolution of the Au/Au sliding contact was characterized through the measurement and tracking of relevant quantities such as the voltage noise across the contact, revealing the ageing of the contact. A phenomenological approach to the sliding contact, coupling both electrical and mechanical aspects, allows a sensible interpretation of the experimental results. This approach retains three contributions to the voltage noise operating at different scales, namely the rings surface geometry, chemical composition fluctuations of the coated rings, and the mesoscopic structure of the contact. A fundamental distinction between these sources is established, owing to their effects relying on either the mechanical contact losses or resistance fluctuations. We finally show that the determination and tracking of these noise sources using reasonable specific indexes lead to reliable criterions of the electrical contact quality.