We report on spectro-ellipsometric investigations of reactively sputtered tantalum nitride (TaNx/SiO2) and vanadium nitride (VN/Si) films. Several TaNx layers with different deposition temperatures (200-400 °C) and a VN layer were prepared optically thick and analyzed using the bulk formula. For thin TaNx layers prepared with the same temperatures as thick layers, the Drude-Lorentz parameterization of dielectric functions was used by simultaneous fitting of ellipsometric and optical transmittance spectra. VN pseudo-dielectric functions show strong metallic character, which is typical for other transition metal nitrides. In contrast, the TaNx dielectric constants obtained here range from a metallic to a non-metallic character depending on substrate temperature, but independent of the film thickness. This substrate temperature dependence may be due to multiple phases in the TaNx films.
- Optical properties