Combined Ellipsometric and Reflectance Measurements for Characterization of Films Formed on Electrodes

Abstract

The conventional form of ellipsometry has difficulty in characterizing a light-absorbing film, because there are only two equations for three unknown properties of the film at a fixed angle of incidence and at fixed wavelength. The three unknown properties are the real and imaginary parts of the dielectric constant and the thickness of the film.⁽¹⁾ In order to overcome this difficulty, supplementary measurements are necessary. However, since these supplementary measurements are often nonoptical or nonsimultaneous with the optical measurements, they are not suitable for in situ monitoring of the formation of thin films on electrode surfaces. The reflectance-ellipsometry technique, or three-parameter ellipsometry as it is often called, in which the ellipsometric parameters and reflectance are simultaneously measured, has proved to be applicable without such difficulties for thin films formed on electrode surfaces.^(2–5) With this technique, transient reflectance-ellipsometry measurements become possible and can be used to characterize the films as functions of time during film formation and during the early stage of growth and change of the films.