Near-zero TCF 11.6-GHz lamb wave resonator based on 128°Y-cut LiNbO3

In this paper, a high-frequency lamb wave resonator (LWR) with near zero temperature coefficient of frequency (TCF) is designed, fabricated, and measured. The reported resonator is of a bi-layer structure consisting of lithium niobate (LiNbO3 or LN) and silicon dioxide (SiO2), and lithographically patterned aluminum (Al) inter-digitated electrode fingers on top of the bi-layer structure. By adjusting the thickness ratio of LN and SiO2 layers, both the electromechanical coupling ( k2) and the TCF, including both TCF at resonant frequency (TCFr) and TCF at anti-resonant frequency (TCFa), of the thickness shear (TS) type LWR are optimized. Experimental results, which are in excellent agreement with theoretical analysis, show that the fabricated 11.6-GHz LWR achieves a k2 of 12.2%, with TCFr and TCFa being -4.2 and -5.4 ppm/K over a temperature range from 30 degrees C to 85 degrees C, respectively, demonstrating huge potential in applications for future wireless communication systems above 10 GHz.