Theoretical and experimental results on two-port resonators fabricated on 36° lithium tantalate

The 36° rotated Y-cut of lithium tantalate (LiTaO₃) (36-LTA) offers an essentially pure shear horizontal (SH) leaky surface acoustic wave (SAW) exhibiting minimal bulk wave radiation losses. Because of the polarization of the wave displacements, 36°-LTA is a viable candidate for liquid phase sensing applications. These devices have demonstrated excellent mass sensitivity. Unfortunately, reproducibility of packaging and the inability to employ oscillator-based measurement techniques have impeded commercialization of biochemical and environmental sensors employing this substrate. The current work explores the behavior of two-port leaky SAW resonators employing aluminum gratings and transducers with a nominal design frequency of 420 MHz. A SAW coupling of modes (COM) model is employed in the design of the leaky SAW resonators. Experimental devices have been designed, manufactured and measured. The behavior of the device with various non-conducting liquid loads is studied. Mass sensitivity (via viscosity-density loading) and dielectric sensitivity are measured