Polarization-Dependent and Ellipsometric Infrared Microscopy for Analysis of Anisotropic Thin Films

Dielectric functions and anisotropic thin film properties such as electronic conductivity or molecular orientations are of high technological importance for engineering efficient optical, electronic, and sensing devices. This work demonstrates for the first time how full-scale polarization-dependent Fourier-transform infrared (FTIR) microscopy may be used for quantitative determination of polarized reflection coefficients of thin film samples with thicknesses down to a few nanometers. Out-of-plane and in-plane optical properties of thin silicon oxide, indium tin oxide (ITO), and polyimide films are measured and characterized quantitatively with respect to anisotropy and thickness. Sample homogeneity is accessed using FTIR microscopic mapping. By performing measurements at multiple polarizer azimuths we demonstrate the technique of ellipsometric microscopy. Exemplarily ellipsometric measurements of a polyimide film are presented and discussed. We describe how introducing a retarder into the optical path would enable sensitive phase measurements via generalized infrared ellipsometric microscopy.