Resonance Properties of Leaky SAW Harmonics on Bonded Dissimilar-Material Structures

Abstract

The propagation and resonance properties of leaky surface acoustic wave (LSAW) harmonics of a bonded dissimilar-material structure, such as LiTaO3(LT)/quartz and LiNbO3 (LN)/quartz, were investigated theoretically and experimentally. Using a finite element method, when the metallization ratio of the interdigital transducer $a/p$ was set to be 0.8, the fractional bandwidth for the third harmonic on 36°Y-cut X-propagating LT (36°YX-LT)/AT-cut 90°X-propagating quartz (AT90°X-quartz) with normalized film thickness $h/\lambda=0.06 (\lambda$ : wavelength) and 27°YX-LN/AT90°X-quartz with $h/\lambda=0.1$ were simulated to be 1.6% and 3.5%, respectively, which were larger than those of the single LT and LN. For an LSAW resonator with $a/p=0.8$ fabricated on 36°YX-LT/AT0°X-quartz, the measured fractional bandwidth, admittance ratio, and resonance $Q$ factor increased to 1.4%,63 dB, and 1,770 from 0.8%, 31 dB, and 480 for the single LT, respectively. The $h/\lambda$ dependence of the measured temperature coefficient of frequency for the resonance frequency on 36°YX-LT/AT0°X-quartz was in good agreement with the calculated value.