Study of Relationship between Cut Angle of Substrate and Characteristics of Surface Acoustic Wave Resonators with Shape-Controlled SiO2

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This study provides the relationship between cut angles of the rotated Y--X LiTaO3 (LT) substrate and characteristics of surface acoustic wave (SAW) resonators with shape-controlled SiO2 in the SiO2/Al/LT system. The 32--48° Y-cut of LT is well known as the leaky-SAW (LSAW) cut of LT. The propagation characteristics of an LSAW are affected by the surface condition of the substrate, and the optimum cut of LT should be determined with respect to such condition. In this study, we investigated the dependence of SAW resonator characteristics on the shape of SiO2 and on the cut angle of LT by simulation and experiment. The dependence of the reflection coefficient and coupling factor on the shape of SiO2 is not changed by the cut angle of LT, but the dependence of the quality factor (Q-factor) on the shape of SiO2 is changed by the cut angle of LT. Additionally, the dependence of the Q-factor on the cut angle at resonance frequency was different from that at antiresonance frequency. It was shown that LT with the rotation angle of 39--42° gives the optimal balance in this system.
2012-07-25