The perturbative approach applied to the characterization of TiO2 films for SAW sensor applications

A TiO2 film has been deposited onto the propagation surface of different piezoelectric substrates in order to measure the elastic constants of the layer. The relative change of the SAW phase velocity before and after the film deposition is expressed, using the perturbation theory, in function of the material density and elastic constants of the film. A comparison between the relative velocity change obtained by exact calculations, the approximate theory and the experimental values allowed us to evaluete the physical constants of TiO2 films to be used as sensitive membranes in relative humidity sensors appluications.