Acoustic Loss of GHz Higher-Order Lamb Waves in Thin-Film Lithium Niobate: A Comparative Study

Abstract

This work reports a comparative study of acoustic loss between different Lamb waves at GHz in thin-film lithium niobate (LiNbO 3 ). The propagation loss (PL) of higher-order Lamb waves in thin-film LiNbO 3 is studied for the first time using acoustic delay line (ADL) testbeds. The acoustic wave attenuation and quality factors ( Q) of different Lamb waves are extracted, showing higher Qs for higher-order Lamb modes than fundamental modes in air and vacuum at room temperature. The extracted Qs are higher than those reported in thin-film LiNbO 3 resonators, implying the electrode and anchor-induced loss as the dominant loss factors. The ADL-based loss analysis framework is readily extendable to acoustic damping study in other microwave acoustic platforms.

Micromachined piezoelectric Lamb wave resonators: a review

“…Meanwhile, phase velocities and electromechanical coupling efficiencies depend on piezoelectric material characteristics and it is challenging to find piezoelectric materials having both high phase velocities and high electromechanical coupling efficiencies simultaneously. It can be seen that AlN or Al x Sc 1−x N with high phase velocities only show moderate electromechanical coupling efficiencies [210], while high-coupling-efficiency piezoelectric material such as LiNbO 3 suffers from relatively low phase velocities [211]. Specifically, there is a trade-off between phase velocity and coupling efficiency in deciding normalized thicknesses and piezoelectric materials.…”

Modal-Transition-Induced Valleys of K2 in Piezoelectric Bilayer Laterally Vibrating Resonators

“…However, the FBARs operate in thickness extensional mode, so the resonant frequency is determined by the thickness of the piezoelectric plate, making it impossible to integrate a multi-band filter onto a single chip through lithography technology. On the other hand, Laterally Vibrating Resonators (LVRs) operate in the lateral strain resonant mode induced by the electric field in the thickness direction, and the resonant frequency is mainly determined by the in-plane dimensions, enabling wafer-level multi-band filters [ 6 , 7 , 8 , 9 ]. One major disadvantage of LVRs compared to FBARs is the moderate electromechanical coupling coefficient ( ) due to the limited piezoelectric coefficient of piezoelectric material, such as AlN.…”