Compressive stress in nano-crystalline titanium dioxide films by aerosol deposition

Abstract

Aerosol deposition is a kinetic energy, particle impacting process to produce dense ceramic films or coatings at room temperature, and thus results in high residual compressive stress. The purpose of this work was to determine the stress and its thickness dependence in titanium dioxide, TiO2, films. Aerosol deposition was used to produce films, 1 to 22 μm thick, on glass substrates. A scanning interferometric optical profiler was used to generate surface maps and measure curvature values of the substrates before and after deposition. The Stoney equation was used to calculate average film stress from the measured thickness and radius of curvature. The effect of substrate shape was also investigated by using square and beam substrates in the deposition experiments. Surface maps of the square and beam substrates after deposition showed an increasing trend towards spherical curvature as the film thickness increased. Average (compressive) stress measured for square samples was 0.37 GPa, while the average for beams was 0.52 GPa. The beam-shaped sample data showed good linearity between curvature and film thickness, and fitting to the simple Stoney formula resulted in an intrinsic stress value of 0.50 GPa.