OXIDATION FILMS ON COPPER IN ALKALINE MEDIA - INTENSITY MODULATED PHOTOELECTROCHEMICAL AND RAMAN-SPECTROSCOPY STUDIES

The composition of thin surface layers on copper oxidized in alkaline media has been determined by combining in situ intensity modulated photocurrent measurements and laser Raman spectroscopy with cyclic voltammetry. Photocurrent measurements showed that the high intensity (less-than-or-equal-to 250 W/cm2) laser Raman probe beam facilitated reduction of the oxidized surface. Laser-facilitated reduction was used to identify the presence of CuO and Cu2O and, when combined with Raman spectroscopy, to differentiate between the formation of CuO and Cu(OH)2 films. Raman spectra confirmed that a thin Cu2O film formed as oxidation of the copper surface was initiated. Increasing the potential produced a Cu(OH)2 layer on top of the Cu2O film. Further oxidation at higher potentials converted the Cu2O film to a CuO underlayer that coexisted with the Cu(OH)2 overlayer.