Ellipsometry of nickel-oxides and -hydroxides in alkaline electrolyte

The growth and oxidation of thin Ni(OH)2 films deposited on Ni were investigated by ellipsometry. The refractive indices of α-Ni(OH)2, β-Ni(OH)2 and γ2-NiOOH were obtained at the wavelength 546.1 nm. Furthermore, the anodic oxidation of Ni in 0.1 M KOH was studied. The passive oxide layer is initially NiO.x H2O. Repeated anodic and cathodic potential cycling change the optical properties of this layer and leads to the growth of a low density oxide layer.