THE ELECTROCHEMICAL-BEHAVIOR OF COPPER IN ALKALINE-SOLUTIONS CONTAINING FLUORIDE, STUDIED BY IN-SITU ELLIPSOMETRY

In situ ellipsometry has been used to reveal a number of interesting f eatures in the growth of passivating films on Cu in 0.1 M KOH containi ng KF. Fluoride ions are shown to affect the growth of the oxide layer and enhanced dissolution of copper as the Cu-II species occurs as a r esult of stress corrosion cracking. A restructuring of the oxide film within the passive region is attributed to loss of water and this effe ct becomes less distinct with increasing F- ion concentration in the e lectrolyte and disorder in the oxide layer. The enhanced reduction of the conductively inhibited bulk CuO/Cu(OH)(2) layer back to copper fou nd in alkaline solutions containing fluoride would indicate that the f ormation of this layer is the dominant one for passivation of copper i n this medium. The difference between the start and the end Delta-Psi values of the metal surface of the cyclic voltammogram at -1.5 V versu s SCE indicates either roughening arising from the oxide formation/red uction or the presence of a residual surface oxide. (C) 1998 Elsevier Science B.V. All rights reserved.