Infrared reflection-absorption spectra of plasma-enhanced chemical vapor deposition (PECVD) amorphous TiO2 thin films on aluminum were obtained with s- and p-polarized light and oblique incidence angles. Such spectra were analyzed by means of spectral simulations based on a Fresnel equation for a three-layered system. The optical constants used in the simulations were obtained through the Kramers–Krönig analysis of the reflectance spectra of a pellet of powdered amorphous TiO2. LO-TO energy-loss functions were also calculated from these optical constants, and a splitting was observed. A good qualitative agreement between experimental and simulated spectra was achieved, and the Berreman effect was observed in both cases when p-polarized light was used. It was shown, therefore, that the Berreman effect makes infrared reflection-absorption spectroscopy a successful technique for the characterization of an amorphous TiO2 thin layer on aluminum.
Laboratory spectra through the mid-infrared have been used to calculate the optical constants (n and k) for a variety of pure and mixed molecular ices. The ices studied were H2O, CH3OH, CO2, OCS, CH4, CO2+CH4, CO2+OCS, CO+CH4, CO+OCS, O2+CH4, O2+OCS, N2+CH4, N2+OCS, H2O+CH4, H2O+OCS, and H2O+CH3OH+CO+NH3.
The thickness dependence of the Berreman effect for naturally grown oxide films on chrome is analyzed theoretically and experimentally. The shift of the spectral position of the Berreman minimum can be described by the Fuchs–Kliewer theory of virtual modes. Both the absorption and the shift of the position can be used for thickness determination. The experimental results compared with calculated values based on different optical constants for Cr2O3 indicate their influence on the position and the absorption of the Berreeman minimum.
Mid-infrared plasmonic platform based on heavily doped epitaxial Ge-on-Si: Retrieving the optical constants of thin Ge epilayers
