Electrical and mechanical contact between rough gold surfaces in air

An original coupling of electrical and mechanical measurements is reported; it concerns the phenomena arising from the interaction between two very close macroscopic electrodes, one a sphere and the other a plane, studied in air. The current-distance and current-voltage curves clearly attest to a tunnelling transfer mechanism, and prove to be in very good agreement with theoretical predictions taking into account the roughness of surfaces. Both electrical and mechanical interpretations coherently indicate the existence of an intermediate substance in the interface, plausibly condensed water with the addition of organic contaminant(s).