Nonlinear distortion voltage testing of contact surfaces

Contact resistance, second-order distortion voltages, and DC vias voltages, which minimize distortion, are measured on a copper surface for studying surface film conditions. Platinum contact members to a copper rod and a polished surface of a single copper crystal are tested. The results are statistically indicated and shown with histograms in order to compare the contact resistance to the DC bias voltage. The results, obtained using a dual-frequency method and DC source, suggest that the second-order distortion (result of rectification) would be caused by a potential difference (difference of work functions of the contact metals) through layers, since the second-order distortion is strongly influenced by a DC bias voltage and approaches zero at a characteristic value for the combination of metals.<>