CHARACTERIZATION OF 36-DEGREES-YX-LITAO3 WAFERS BY LINE-FOCUS-BEAM ACOUSTIC MICROSCOPY

Application of line-focus-beam (LFB) acoustic microscopy is extended t o characterization of substrates for SH-type SAW devices, Theoretical and experimental studies on a wave mode for characterization are carri ed out on 36 degrees Y-cut LiTaO3 wafers, A Rayleigh-type mode of leak y surface acoustic waves (LSAWs) must be employed instead of an SH-typ e mode of leaky pseudo-surface waves (LPSAWs), Experimental results sh ow that the LSAW propagation should be directed along and the X-axis b ecause the LSAW velocities are more sensitive to chemical composition and elastic inhomogeneities. The relations among the LSAW velocities, densities, and Curie temperatures are determined, The LSAW velocity in creases linearly at the rate of 0.52 m/s/degrees C with the Curie temp erature. A chemical composition change of 0.03 Li2O-mol%, correspondin g to temperature resolution of better than 0.3 degrees C, is easily de tected by the velocity measurements. Elastic inhomogeneities due to re sidual multi-domains, produced during the poling process during wafer fabrication, are interpreted quantitatively by this ultrasonic technol ogy.