A New Method for the Determination of the Optical Constants of Thin Films

The optical constants of weakly absorbing thin films, deposited on thick nonabsorbing substrates, are determined from reflectance and transmission data. The fit of the theoretical expressions with the experimental data yields a large number of values of the refractive index which become closer to each other as the ratio of the film thickness to the wavelength of the radiation increases. A new approximative method is suggested in order to overcome the ambiguity of the multiple solutions. This method is then applied to the exact determination of the refractive index, the absorption coefficient, and the thickness of a YTG film.