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Sc(2)O(3) and Y(2)O(3) films were prepared by evaporation from resistance heated boats in a residual gas atmosphere of oxygen. Films of much lower absorptance were obtained than from coatings produced in high vacuum. The short wavelength limit of high transparency was between 300 nm and 400 nm, while the long wavelength absorption edge was reached at about 11 microm. Refractive indices of 1.8-2.0 were measured for both oxides. The influence of annealing on the optical- properties of the films was investigated. The films were amorphous and proved to be mechanically very stable and water resistant. Electron micrographs showed smooth and uniform surfaces. By antireflection coatings of yttria the transmittance of silicon was increased from 52% to 99.4% at the maximum. Possible advantages by the application of Sc(2)O(3) and Y(2)O(3) instead of SiO for antireflection coatings on GaAs laser surfaces are discussed.

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By conventional reactive evaporation techniques, films with a certain deviation from stochiometric composition and, therefore, increased absorptance and dielectric losses were obtained. By ionization of the residual gas a considerable increase of reactivity has been achieved. The construction of a discharge tube with a region of high current density for ionization is described. The tube was arranged inside a bell jar. The ionized gas emerged from a nozzle in the wall of the tube directly into the high vacuum region. Production parameters for SiO(2), SiO(x)N(y), and TiO(2) films were evaluated. On unheated substrates SiO(2) films, which are practically free of absorptance down to 190 nm, and TiO(2) films with refractive indices up to 2.3, were obtained.