Modulating the Residual Stress of Ion-Assisted TiO2 Films during Annealing with Film Thickness and Substrate Temperature

Titanium dioxide (TiO2) films were prepared using ion-beam-assisted deposition on glass substrates with different film thicknesses and substrate temperatures. The effects of thermal annealing temperatures ranging from 100 to 300 degrees C on the residual stress of these films were investigated. The residual stress in the as-deposited films can be changed from compression to tension stress simply by increasing film thickness when the substrate temperatures are 150 degrees C. However, the residual stress in the as-deposited films can vary from tension to compression stress by increasing the substrate temperature when the film thickness was 600 nm. The residual stress, optical properties, and X-ray diffraction were investigated for TiO2 films during thermal annealing. The residual stress was gradient distribution in the film along the depth direction from the surface to the substrate. An annealing temperature of 200 degrees C is the key temperature when the TiO2 thin films will have the lowest residual stresses and highest refractive indices. However, the deposition only modulated the proper conditions of film thickness, substrate temperature, and annealing temperature to obtain the low residual stress and high refractive index for the TiO2 films. (C) 2011 The Japan Society of Applied Physics