An Ellipsometric Study of the Anodic Deposition of Iron Oxide Films

Abstract

Films of iron oxide were deposited on iron, platinum, and gold substrates by the anodic oxidation of ferrous ions contained in neutral electrolytes. The film growth was followed optically to thicknesses of several thousand angstroms with a following ellipsometer. The films deposited from borate electrolyte onto iron and platinum substrates were found to have a real refractive index equal to 1.7 at a wavelength of 6328Aå. The films deposited onto a gold substrate from borate electrolyte were found to have a refractive index with a real component of 1.7 and a small but nonzero absorption coefficient. The films deposited onto a platinum substrate from perchlorate electrolyte were found to have a real refractive index equal to 1.93. We conclude that films with index 1.7 have an amorphous structure, films with index 1.93 are crystalline, and films deposited on gold substrates have trace amounts of gold incorporated in the film.