Preparation and properties of high refractive index tantalum pentoxide coatings deposited by plasma ion assisted deposition with xenon or argon assistance

Tantalum pentoxide films have been prepared by plasma ion assisted electron beam evaporation, utilizing argon or xenon as the working gases. The optical constants of the layers have been investigated by spectrophotometry, while X-ray reflection measurements and energy dispersive X-ray spectroscopy have been performed to get information about the density and noble gas content of the layers. The correlation between the level of plasma ion assistance and the layer properties is discussed. With respect to optical quality, the application of xenon as the working gas results in coatings with higher refractive index than the application of argon. This effect is attributed to a more efficient momentum transfer from high energetic working gas ions or atoms to tantalum atoms during deposition.