Hafnium dioxide films have been produced by plasma ion assisted electron beam evaporation, utilizing argon or xenon as working gases. The optical constants of the layers have been investigated by spectrophotometry, while X-ray reflection measurements (XRR), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) have been performed with selected samples. The correlation between structural and optical properties is discussed. With respect to optical quality, the application of xenon as working gas results in coatings with higher refractive index and smaller surface roughness than the application of argon. This effect is attributed to a more efficient momentum transfer from high energetic working gas ions or atoms to hafnium atoms during deposition.