Biblio

Expanding techniques for chip-scale acoustic wave focusing would open doors for advancements in signal processing and quantum electromechanical microsystems. In this paper, we present a method for acoustic wave focusing and wavefront shaping at radio frequencies (RF), validated with thin-film lithium niobite on a low-loss and high coupling silicon carbide (LiNbO3-on-SiC) testbed. By depositing a metal layer, we can mitigate the piezoelectric stiffening effect, and reduce the acoustic wave speed in a patterned area. Employing a design analogous to geometric optical systems, efficient acoustic wave focusing is experimentally observed. With more development, this technique could be employed in emerging acoustic microsystems.

In this paper, an acoustic resonator with frequency \textbackslashtextgreater 5 GHz is designed, implemented, and measured with electromechanical coupling exceeding 15% and low temperature dependence compared to conventional Lamb-wave resonators. The acoustic resonator is optimized for the S4 mode Lamb waves in a bi-morph composed of Lithium Niobate and Silicon Dioxide. The resonator optimization is based on adjusting the thickness of different materials in the bimorph to maximize the coupling and minimize temperature dependence simultaneously. The achieved specifications are adequate for 5G sub-6 GHz frequency band n46 in addition to Wi-Fi new bands between 5 and 6 GHz.

Surface acoustic wave devices based on LiNbO3/interlayer/substrate layered structure have attracted great attention due to the high electromechanical coupling coefficient (K2) of LiNbO3 and the energy confinement effect of the layered structure. In this study, 30° YX-LiNbO3 (LN)/SiO2/Si multilayered structure, which can excited shear-horizontal surface acoustic wave (SH-SAW) with high K2, was proposed. The optimized orientation of LiNbO3 was verified by the effective permittivity method based on the stiffness matrix. The phase velocity, K2 value, and temperature coefficient of frequency (TCF) of the SH-SAW were calculated as a function of the LiNbO3 thickness at different thicknesses of the SiO2 in 30° YX-LiNbO3/SiO2/Si multilayer structure by finite element method (FEM). The results show that the optimized LiNbO3 thickness is 0.1 and the optimized SiO2 thickness is 0.2λ. The optimized Al electrode thickness and metallization ratio are 0.07 and 0.4, respectively. The K2 of the SH-SAW is 29.89%, the corresponding phase velocity is 3624.00 m/s and TCF is about 10 ppm/°C with the optimized IDT/30° YX-LiNbO3/SiO2/Si layered structure.