DETERMINATION OF THE OPTICAL DIELECTRIC FUNCTIONS OF THIN ABSORBING FILMS FROM IR REFLECTIVITY MEASUREMENTS

A method of determining the optical dielectric function of an absorbing thin film overlayed on an absorbing thick substrate by a classical oscillator fit to its experimental IR reflectivity spectra is reported. This simple method overcomes the difficulty that occurs in identifying those modes of the film with large damping. Using this method the optical dielectric function of a gamma-Al2O3 thin film overlayed on a single-crystal alpha-Al2O3 substrate is determined.