Abstract

MgF₂ and TiO₂ are the most common used low and high refractive-index coating materials, respectively, for optical applications. However, the characteristics of MgF₂ and TiO₂ films depend on the fabrication methods. MgF₂ and TiO₂ thin films deposited by conventional thermal evaporation processes at an ambient temperature typically have inferior optical, structural, mechanical, and chemical properties compared with the bulk materials, which is attributed to the moisture absorption due to the columnar structure and low packing density. Thess problems can be remedied by raising the substrate temperatures or by high energy ion bombardment. It has been shown that TiO₂-MgF₂ composite films prepared by reactive ion-assisted coevaporation (IAC) do offer the potential of improving performance by optimizing their properties.¹ The aim of this paper is to study the optical, structural, and mechanical properties of TiO₂-MgF₂ composite films prepared by electron-beam coevaporation (EBC) at the substrate temperature of 280 °C. The comparison of the properties on these films with those obtained by reactive IAC is also presented.

© 1995 Optical Society of America