The Investigation of the Mechanism of Formation of Passive Layers on Metals by Means of Ellipsometry

摘要

Electrochemically induced passivity of cobalt in contact with aqueous solution of pH 8.3 was observed by electrochemical and optical measurements. Dissolution rate of cobalt was reduced by a factor of about ten by passivation at the potentials between -0.3 and +0.6 volts vs. SCE. A new method of extended ellipsometry, in which reflectivity as well as the polarization states of reflected light were measured and used for the calculations of thickness and optical constants of a thin film, was developed. The passivating film formed at -0.08V vs. SCE was found, by application of the extended ellipsometry, to have thickness of 12 A and optical constants of 3.0-i0.25. (Author)