The change in thickness and other optical properties of ultraviolet irradiated silicon oxide films

Many of the optical properties of irradiated silicon oxide films, relevant to the employment of the films as phase compensating layers for Fabry-Perot surface defects, are determined. Ultraviolet radiation induces complementary changes in thickness and refractive index but does not increase the surface roughness of the films. Partially irradiated films exhibit inhomogeneity of refractive index, and a film model is proposed. The optical properties change with age, but the effects are sometimes small. For example, a step of height 8 nm, induced by irradiating a 143-nm film, changed height by about 0.2 nm over a period of three months.