Abstract

Titanium dioxide (TiO₂) thin films produced by conventional physical vapor deposition (PVD) techniques such as reactive electron beam evaporation typically have reduced packing density and refractive index. The porous and columnar microstructure of these films cause deterioration of their performance in varied environmental conditions primarily due to adsorption of water vapor. It has also been found that process variations adversely affect the reproducibility of TiO₂ coatings much more severely than that of other films such as SiO₂ and ZrO₂. An inter-laboratory study conducted in 1986 and 1987 established that different processes and starting materials result in widely differing properties of TiO₂ films.¹ Such variations and rather non-controllable properties of TiO₂ films present a tremendous challenge in manufacturing environment. As TiO₂ is a highly useful material for multilayer optical coatings because of its high refractive index, a reproducible deposition process would be highly desirable.

© 1992 Optical Society of America