Stress relaxation and optical characterization of TiO2 and SiO2 films grown by dual ion beam deposition

TiO2 and SiO2 films are deposited by dual ion beam deposition with the objective to minimize the film stress. The influence of different parameters (energy and flux) of an assisting Ar+ or Xe+ ion beam on the film stress and on the optical properties is investigated by measuring the curvature of the samples and by spectroscopic ellipsometry, respectively. It is shown that the stress can be reduced considerably by the assisting ion bombardment. The most important parameter is found to be the ion energy. Ion flux and ion species have only a minor effect. The refractive index of the SiO2 films decreases slightly with ion bombardment, whereas the refractive index of the TiO2 is reduced by similar to 0.1-0.2. However, no absorption is introduced for the TiO2 and SiO2 films upon ion bombardment, which makes the stress-optimized dielectric films promising candidates for advanced optical applications. (c) 2008 Elsevier B.V. All rights reserved.