Characterization of 36°YX-LiTaO3 wafers byline-focus-beam acoustic microscopy

摘要

Application of line-focus-beam (LFB) acoustic microscopy isnextended to characterization of substrates for SH-type SAW devices.nTheoretical and experimental studies on a wave mode for characterizationnare carried out on 36°Y-cut LiTaO3 wafers. AnRayleigh-type mode of leaky surface acoustic waves (LSAWs) must benemployed instead of an SH-type mode of leaky pseudo-surface wavesn(LPSAWs). Experimental results show that the LSAW propagation should bendirected along the X-axis because the LSAW velocities are more sensitivento chemical composition and elastic inhomogeneities. The relations amongnthe LSAW velocities, densities, and Curie temperatures are determined.nThe LSAW velocity increases linearly at the rate of 0.52 m/s/°C withnthe Curie temperature. A chemical composition change of 0.03 Li2nO-mol%, corresponding to temperature resolution of better thann0.3°C, is easily detected by the velocity measurements. Elasticninhomogeneities due to residual multi-domains, produced during thenpoling process during wafer fabrication, are interpreted quantitativelynby this ultrasonic technology