High Figure-of-Merit 36Y-Cut LiNbO₃ Lamb Wave Resonators With Dissipation Loss Optimization

In this work, we present the development of high figure-of-merit (FOM) symmetric Lamb wave (S0) mode resonators using 36Y-cut single-crystal lithium niobate (LiNbO3) thin films. This study enhances the quality factor ( ${Q}_{s}$ ) through optimization of anchor dimensions and in-plane rotated angle ( $\alpha $ ). A periodic relationship between ${Q}_{s}$ and $\alpha $ was observed, which is attributed to the anisotropic viscosity coefficient ( $ \eta $ ) of the S0 mode in 36Y-cut LiNbO3. A method of acoustic delay lines (ADLs) for evaluating $ \eta $ related to the anisotropic intrinsic loss mechanism is proposed on this platform. In this method, the experimental results indicate an inverse correlation between $ \eta $ and $ {Q}_{s} $ . Notably, our findings explicitly demonstrate that the condition for minimal acoustic loss does not universally correspond to $\text {PFA}=0$ , emphasizing the necessity of a quantitative $\eta $ analysis. Our optimized resonator exhibits an electromechanical coupling coefficient ( ${k}_{t}^{2}$ ) of 12.3% and a significant ${Q}_{s}$ of 2273 at 323.6 MHz, resulting in an FOM of approximately 280. The reported platform can potentially deliver high-performance radio frequency (RF) applications.Index Terms- Acoustic propagating angle, high figure-of-merit (FOM), lamb wave resonators, lithium niobate.