Abstract
Inhomogeneity of a thin film, rough interfaces of the film with air and substrate and non-parallelism of these interfaces severely affect reflectance and transmittance. Neglecting these film imperfections could give rise to erroneous optical characterisation of the film from measured spectra. Each one of these imperfections, considered alone, has its own characteristic influence on the interference fringes of the reflectance and transmittance spectra. In this work, a model of an inhomogeneous thin film bounded by rough, unparallel interfaces is introduced for calculating reflectance and transmittance at normal incidence. The effects on the spectra due to roughness as predicted by the proposed model are compared with those evaluated by an approach involving the effective-medium approximation (EMA). In this latter approach, a thin transition layer replaces the rough interface, but it proves inadequate for reproducing the transmittance spectrum. Finally, the model is successfully applied to the characterisation of a LiF film thermally evaporated on a glass substrate.
Published Version
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