LINE FOCUS ACOUSTIC MICROSCOPY TO MEASURE ANISOTROPIC ACOUSTIC PROPERTIES OF THIN-FILMS

Propagation characteristics of surface acoustic waves on thin film coated elastic materials have been investigated by the use of an acoustic microscope with a line focus beam. Measurements were carried out for thin films of various thicknesses deposited on the (001) plane of cubic crystals. The phase velocities measured as functions of the angle of propagation display the anisotropy and confirm the advantage of directional measurement by the line focus acoustic microscope. Dispersion curves of surface waves propagating along the symmetry axes were obtained for various film thicknesses and frequencies. A systematic inversion of surface wave data based on a comparison of theoretical and experimental results has been used to obtain the thin film material constants.