Ellipsometric Study of Ni–P Film Surfaces

Abstract

Ellipsometric measurements were performed on the surfaces of freshly deposited, hydrogen annealed, and thermally oxidized electroless Ni–P deposits. Conventional interpretation of the parameters ψ and Δ for the oxidized samples, in terms of a homogeneous surface oxide film, was found possible only for a certain class of samples. For the remainder, the results suggested that changes of the surface region of the metal were caused by absorption and desorption of gases, rather than by a surface oxide formation. To facilitate better interpretation of ψ and Δ for all samples, the spectral reflectance of both surfaces of the deposits were measured with a spectrophotometer in the photon energy range 0.5–4 eV. An attempt was also made to establish the optical constants and the film thickness of totally oxidized films, to be used as a check on the ellipsometer results, without success. The results suggest a rather complicated oxidation process for Ni–P deposits with an inhomogeneous surface oxide film.