Non-destructive evaluation of thin ZnO shear wave transducer by Brillouin scattering

Elastic properties of thin ZnO shear wave transducers have been investigated. These transducer films were fabricated by magnetron sputtering. They are almost composed of unidirectional ZnO crystallites, which were confirmed by X-ray diffraction measurements. The elastic properties of the film seem difficult to evaluate by conventional mechanical measurements. We have then applied a Brillouin scattering technique, which enables the measurement of the hypersonic wave velocity in the GHz range. In spite of the thickness of several micrometers and problems with transparency, we have performed the precise measurement of velocity with estimated errors of 0.5%, which was sufficiently small to evaluate the film.