An Ellipsometric Study of Manganese Oxide Films

Abstract

The electrodeposition of manganese oxide films onto a platinum substrate was investigated by means of in situ ellipsometry. In the thickness range from 0 to 150 nm, the anodic oxide behaves as an isotropic single layer with optical constants that are independent of thickness. Deviations at higher thickness are explained in terms of anisotropic properties of the film. The electroreduction of thin films up to ca. 150 nm in an alkaline electrolyte leads to a decrease in both the refractive index and the extinction coefficient and is accompanied by a thickness increase of ca. 10%. The MnIV to MnIII conversion takes place from the oxide/electrolyte interface inwards.