Investigation of the refractive index and dispersion parameters of tungsten oxynitride thin films

Thin films of WOxNy films were prepared by dual magnetron sputtering on glass substrates and in mixtures of argon, oxygen and nitrogen. X-ray diffraction revealed that the films are amorphous in nature. The optical transmittance and reflectance measurements were performed using spectrophotometer. The refractive indices have been evaluated in terms of envelope method, which has been suggested by Swanepoul in the transparent region. The refractive index could be extrapolated by Cauchy dispersion relationship over the whole spectra range, which extended from 300 to 2500 nm. It was observed that the refractive index increased with increasing nitrogen content over the entire spectral range. The dispersion parameters were evaluated and analyzed. The values of the tungsten effective coordination number, Nc, was estimated from the analysis of the dispersion of the refractive index.