The effect of ion neutralization processes on interfacial energy of stationary contacts

Practical utilization of direct measurements of the electrical energy stored at the interface of mechanically contacted metals has been used as a tool to demonstrate experimentally the effect of ion neutralization processes at the interface. Due to the presence of surface asperities, interfacial cavities filled with the gas from the surrounding space may play an important role in charge transport processes, since they provide additional current paths between the non ideally contacted spots of current carrying metallic interfaces. Measurements of the electrical energy stored at the interface were performed in stationary OFHC and silver based alloy contacts in a high vacuum environment (total pressure below 10⁻⁵ mbar). The composition of the surrounding space could be determined in situ by employing quadrupole mass spectrometry. The effect of small quantities of nitrogen, oxygen or SF6 on the overall interfacial electrical energy has been investigated for the case of a contact operated at a constant current mode. The obtained experimental results demonstrate convincingly variations of the interfacial electrical energy depending on the composition of the surrounding space and the important role of the non ohmic transport processes across metallic interfaces operating under high charge injection rates.