The Influence of Various Parameters on the Refractive Index of Evaporated Dielectric Films

The influence of residual gas pressure and of deposition rate on the refractive index of Na(3)AlF(6) and ThF(4) films was investigated. Transition from high to medium deposition rates causes a distinct decrease of the refractive index, but a further reduction of the deposition rate gives practically no additional change. Increasing the residual gas pressure from 2 or 4 x 10 (-6) to 2 x 10 (-5) torr has no influence on the refractive Index although at 2 x 10 (-4) torr a lower value was measured. The refractive indices of Na(3)AlF(6), ThF(4), and ZnSe coatings deposited on Ag and Al films were found to be essentially the same as those obtained on dielectric multilayers.