Multilayer inverse synthesis techniques for the analysis of mixed-mode inhomogeneities in composite and co-deposited dielectric coatings

Abstract

It has been well established in recent times that mixed composite materials provide optical, mechanical, and stability advantages over pure dielectrics and ceramics. Such materials include fluoride and oxide compound mixtures that are co-evaporated or sputtered from pure or solid solutions of the composite starting materials. Mixed mode inhomogeneities are very typical to the growth of these composite and co-deposited films. When such conditions exist, the transmittance and reflectance spectra and even ellipsometric measurements get considerably modulated and extraction of optical constants from these measurements becomes extremely difficult. In these situations multilayer inverse techniques become the more appropriate and powerful approaches to derive not only various constants but also growth-dependent compositions in these films. In this work, a special multilayer inverse technique based on a powerful geometric approach along with the needle technique has been described to characterize such mixed-mode inhomogeneities.