Investigation on the reproducibility of optical constants of TiO_2, SiO_2, and Al_2O_3 films, prepared by plasma ion assisted deposition

Abstract

Titanium dioxide, aluminum oxide, and silicon dioxide layers have been prepared by plasma ion assisted electron beam evaporation employing the Advanced Plasma Source (APS). The refractive indices have been determined by spectrophotometry in order to quantify their reproducibility. Standard deviations in the refractive index turned out to be highest for titanium dioxide, and lowest for silicon dioxide. The refractive index reproducibility of titanium dioxide could be improved by replacing the commonly used BIAS voltage control concept by a novel alternative approach concerning ion beam power, termed JE. All these findings are discussed in terms of a model that considers the real oxide film as a binary mixture of a solid fraction with a small amount of pores, within the limits provided by the Wiener bounds.