Mechanical stresses in oxide thin films

Abstract

This paper presents a description of the mechanical stresses in TiO 2 and Al 2O 3 thin films. The different oxides were deposited in a high vacuum system on a sodalime substrate. Deposition of the coatings was carried out in the reactive atmosphere of O 2. Although the literature quotes values for the stresses in films, actual strains are measured. Quantitative analysis of the stresses in oxide thin films is given, which is based on deformations of the substrate and on interferometric measurements. On thin substrates, oxide thin films cause substrate curvature. Since the final substrate curvature depends on parameters, such as the initial substrate curvature, it is measured three times: the substrate without films at room temperature; the substrate without films, which was treated previously at the temperature of the films' deposition; and the substrate with deposited films. On the basis of experimental work, the strain analysis of a thin oxide film is given depending on the substratum temperature, the film thickness and the stoichiometric structure of the film materials.