LiNbO3 Plate Bonded to Quartz as a Substrate for High Frequency Wideband SAW Devices

Bonded wafers combining a thin LiNbO3 plate with a quartz substrate were studied numerically as potential substrate materials for high frequency wideband SAW devices. Longitudinal leaky waves propagating with velocities up to 7000 m/s were investigated, and the multilayered structure was optimized to combine high velocity, high electromechanical coupling and negligible propagation losses. In the optimized structures non-attenuated waves can propagate with velocities V=5500-6200 m/s and coupling up to 18%. Examples of simulated admittances of SAW resonators demonstrate that in some optimal LiNbO₃/quartz structures high quality factors Q>5000 can be achieved simultaneously at resonant and antiresonant frequencies if duty factor of electrode structure varies between 0.48 and 0.65. Due to sufficiently large optimal plate and electrode thicknesses, 40% and 5% of a wavelength, respectively, the found structures can be employed in SAW resonators operating at high frequencies, up to 5 GHz.