Surface plasmon-polariton study of the optical dielectric function of titanium nitride

This work presents the first detailed study of the optical dielectric function of optically thick TiNx films using grating coupling of radiation to surface plasmon-polaritons. Angle-dependent reflectivities are obtained in the wavelength range 500-875 nm and by comparison with grating modelling theory, we determine both the imaginary and the real parts of the dielectric function. This method provides an alternative to traditional characterization techniques (e.g. Kramers-Kronig analysis) that may require additional information about film thickness, or the sample's optical properties in other parts of the electromagnetic spectrum. We have fitted the determined dielectric function to a model based on a combination of interband absorptions and free-electron response evaluating both the plasma energy and the relaxation time.