CATHODIC REDUCTION OF OXIDES FORMED ON COPPER AT ELEVATED-TEMPERATURES

Cathodic stripping is used to determine the oxide thickness on copper. For copper oxidized at elevated temperatures the potential-time curve at constant cathodic current density features two distinct regions, c orresponding to the reduction of two different oxides. The sequence in which the oxides are reduced at constant current density has been exa mined here using potential-time measurements and electron spectroscopy for chemical analysis. The results show that the top layer of cupric oxide, if continuous, is cathodically reduced first at a higher potent ial, followed by reduction of the inner layer of cuprous oxide at a lo wer potential. This conclusion is at variance with a reduction model u sed in measurements of the oxide thickness in the industry and accepte d as part of a standard specification.