Ellipsometric changes produced by oxidation—reduction potential cycles applied to cadmium in sodium hydroxide solutions

• Autores: Zerbino, Jorge Omar; Saidman, S. B.; Vilche, Jorge Roberto; Arvia, Alejandro Jorge
• Año de publicación: 1990
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Química; Oxidation; Cadmium; Sodium hydroxide solutions
• Institución: Universidad Nacional de La Plata

Ellipsometry data obtained for the Cd-NaOH solution interface under the influence of potential cycles in the potential window where the Cd(OH)₂-CdO layer can be electroformed and electroreduced, are particularly sensitive to both the layer thickness and the upper electroformation potential limit. The best fitting of the experimental results is obtained for two limiting situations. For thin anodic layers (d ⩽ 6 nm) the ellipsometric data fit the equation ñ=1.55−i 0.005, whereas for relatively thicker anodic layers (d > 7 nm) data can be adjusted through the equation ñ=2.6−i 0.10. These equations are consistent with the electroformation of a hydrous cadmium oxide layer at low potentials, and a cadmium oxide layer with a lower water content which grows beneath the former one at high potentials. Otherwise, the electroreduction of the anodic oxide layer yields a cadmium overlayer which exhibits a shift of the corresponding ellipsometric data as compared to the starting cadmium surface. This shift is presumably related to the development of different metal surface textures resulting from the different electroreduction conditions.
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas