Interpretation of Reflection and Transmission Spectra for Thin Films: Reflection

Abstract

The optical behavior of a thin film (i.e., peak positions and intensities of infrared spectra) has been discussed for reflection under a thin-film approximation. The reflection spectra of anisotropic and isotropic thin films on various substrates (transparent, dielectric and absorbing, and semi-metal) have been simulated at various angles of incidence in the infrared region for external and internal reflection. For spectral simulation, the matrix method has been used in conjunction with noise-free complex refractive indices based on dispersion theory. The peak positions in the simulated spectra have been compared with transverse optic and longitudinal optic frequencies based on macroscopic theory. The simulated peak intensities for the films have been compared with the prediction based on the thin-film approximation. The optical behavior of reflection spectra has also been examined in detail for a thin film on water or highly oriented pyrolytic graphite.