Growth and on-line stress evaluation of TiO₂ and SiO₂ films

Here we addressed the on-line stress evaluation of the TiO₂ and SiO₂ films, grown by ion beam assisted deposition (IBAD) and electron beam evaporation on glass substrates, respectively. The impacts of ion energy and film thickness on variations in the stress distribution during the film growth were characterized on-line with a lab-built stress measurement setup, based on Hartmann sensor. The results show that the ion sputtering significantly affects the stress and distributions of both the TiO₂ and SiO₂ films. For example, the tensile stress of the IBAD TiO₂ film is 40 MPa lower than that of the electron-beam evaporated films. Moreover, as the ion energy increased, the tensile stress gradually changed into the compressive stress; and its refractive index increased, with a peak of 2.56. In case of SiO₂ film growth, the ion beam assistance affects more strongly the stress and microstructures. The ion sputtering results in a dominance of the tensile stress, whereas compressive stress prevailed in electron-beam evaporated SiO₂ films. Besides, an increasing ion-energy roughens its surface, and reduces its refractive index.