IR surface polariton spectroscopy as a method for studying the optical properties of ultra thin films

Experimental results of investigation of optical properties of MgO thin films (thickness 10, 30, 100 and 300 nm) and AlN films (thickness 40 and 400 nm) on sapphire substrate are discussed. The optical phonon frequencies of these films are located in frequency region of surface polariton of sapphire. Due to the resonance between them the splitting and the shift of absorption spectra of sapphire surface polariton appear. From these experimental data it is possible to reconstruct all constants of the permittivity of both the film and substrate, the film thickness, and to specify its structure.