Elastic properties of SnO2 films

SnO₂ films have been recently used as reactive materials in gas sensors based on change of the electrical resistivity under gas exposure. In view of potential application of these films to surface acoustic waves (SAW) sensors, knowledge of their elastic properties is of current interest. We report here on results of the elastic characterization of SnO₂ films, with thicknesses in the range between 0.2 and 3 μm, prepared by reactive magnetron sputtering. Brillouin light spectroscopy has been exploited in older to determine the phase velocity of both surface and bulk acoustic modes on films deposited on (001)-Si substrates. Moreover, an ultrasonic technique has been used to measure the group velocity of the Rayleigh wave in layered structures consisting of a piezoelectric plate (quartz or LiNbO₃) coveted with a SnO₂ overlayer. The whole information gained by use of these two techniques has been used for determining the effective elastic constants and the mass density of the SnO₂ films. SAW attenuation and temperature coefficient of delay on the film material have been also evaluated