Surface and interface acoustic waves in SiO2/Y X-LiNbO3

For Y-cut lithium niobate, a leaky shear horizontal (SH) surface wave is known to propagate along the X axis. When an SiO2 film is deposited on the LiNbO3 surface, the SH wave is found experimentally to have low loss and theoretical calculations show the wave to be closely confined to the surface. Two additional acoustic modes are observed in the SiO2/YX-LiNbO3 configuration. One mode is a Rayleigh-type surface wave and the other a generalized Stoneley wave. Experimental measurements and theoretical predictions of the wave velocities versus film thickness to wavelength ratio (h/λ) are presented. Measurements of the temperature coefficient of time delay are given for the SH wave showing a zero first order coefficient at h=0.42λ. The sensitivity of this wave to bending strains is also presented.