In this paper experiments with reactive evaporation of the starting materials Ti, TiO, Ti(2)O(3), Ti(3)O(5), and TiO(2) to obtain nonabsorbing TiO(2) films are under discussion. For the starting materials TiO and Ti(3)O(5) the dependence of the TiO(2) film refractive index on the substrate temperature, oxygen pressure, and deposition rate was measured. For TiO dispersion curves of the resulting TiO(2) films as a function of the substrate temperature during film formation were determined. The successive evaporation of the different starting materials resulted in the formation of lambda/4 TiO(2) films with different refractive indices. This phenomenon was most obvious during the first evaporation. It disappeared after several evaporations in two groups of TiO2 films with different refractive indices. From the beginning only the starting materials Ti and Ti(3)O(5) resulted in TiO(2) films with constant refractive indices. The first material produced a high, the latter a lower film index. Depending on the number of evaporations performed, both types of TiO(2) films can be obtained with TiO. The films and residues in the crucibles were also subjected to chemical analyses. An attempt was made to explain the optical properties of the resulting TiO(2) films with regard to crystal structure, chemical composition, packing density influenced by the molecular composition of the vapor beam, chemical reaction with the crucible, substrate temperature, O(2) pressure, and deposition rate.

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There is a wide choice of starting materials for the production of titanium dioxide films by reactive electron-beam evaporation. We have investigated the specific merits of these materials in terms of refractive index, stress, and abrasion resistance of the resultant titanium dioxide films. The suboxides TiO, Ti2O3, and Ti3O5 as well as titanium dioxide and titanium metal were reactively evaporated, and titanium dioxide films free of absorption were obtained on substrates at 25 and 250 degrees C. On unheated substrates the refractive index, which varies from 2.06 to 2.22, the stress, and the abrasion resistance all depend on the starting material used. On substrates heated to 250 degrees C the refractive indices of all films lie closely about 2.4, and all films show high tensile stress and good abrasion resistance.

The titanium suboxides TiO, Ti2O, and Ti3O5 are widely used to produce films of titanium dioxide by reactive evaporation. If they are evaporated in high vacuum, however, they yield absorbing TiO(x) films with a transmission color varying between blue and gray. We investigated the specific properties of these TiO(x) film. TiO, Ti2O3, Ti3O5, and titanium metal were evaporated in high vacuum upon glass substrates at 25 degrees and 250 degrees C. Differences in chemical composition, transmission and reflection, color, stress, and abrasion resistance of these fims, depending on the starting material and the substrate temperature, were evaluated.

This paper, presented at the February 1976 OSA Topical Meeting on Optical Interference Coatings, discusses the chemical aspects of the production of thin films and the packing density effects in dielectric films. Useful materials are briefly surveyed, current trends are reviewed, and some examples of applications are given.