6K-3 Super Low Velocity Thin Film Gratings/Piezoelectric Substrate Structure with High Reflectivities and Applications for SAW Resonator Filters, Unidirectional SAW Transducers and Bulk Acoustic

In this paper, the propagation characteristics and reflectivities of TeO₂ grating/128deg Y-X LiNbO₃, 36deg Y-X LiTaO₃ and 5deg Y-X LiNbO₃ are analyzed and applied to resonators, conventional and dispersive unidirectional transducers and solidary mounted bulk wave resonators. Theoretical results of thin film gratings show the large reflectivity, for examples, thin film gratings gives r = 0.95 at the thickness of H/lambda = 0.01, for 128deg Y-X LiNbO₃. The experimental results of IDT resonator of thin film (H/lambda= 0.01)/Al/128deg Y-X LiNbO₃ with N = 80,W = 20 lambda have admittance of -5 dB, compared with -14 dB without thin films. The experimental unidirectional transducer filter using thin film (H/lambda = 0.015)/Al/128deg Y-X LiNbO₃ showed the 1.6 dB insertion loss at 500 MHz without matching. Also flat wide band low loss nondispersive filter characteristics are developed using dispersive unidirectional IDT. Finally, thin film bulk acoustic wave resonator (SMR) of ZnO/W/TeO₂ thin film//W/TeO₂ thin film/Si substrate structure showed the 30 dB at resonance and -60 dB at anti-resonance