Periodically Poled Piezoelectric Single-Layered and Multilayered Lithium Niobate for Thickened High-Order Lamb Wave Acoustic Devices

Unlike the state-of-the-art approach of thinning films for high-frequency applications, this work focuses on developing the thickest films for X-band acoustic devices, with the aim of simultaneously reducing the mechanical loss, maximizing the electromechanical coupling, increasing capacitance density, minimizing parasitic effects, and enhancing thermal stability. This article presents a comprehensive theoretical and experimental analysis of the Lamb wave acoustic devices utilizing periodically poled piezoelectric single- and multi layered lithium niobate (LN) thin films. This work demonstrates the flexibility of higher order mode excitation within different layers of LN by adjusting the poling directions, number of layers, and the thickness ratio among layers. With the perfect thickness matching, the fabricated bilayer and trilayer periodically poled piezoelectric film (P3F) resonators present k²_t values comparable with the single-layer resonator without multiple parasitic overtones and a significant improvement in mechanical quality factor ( Q_m. Notably, Q_m of the third- and fourth-order Lamb wave modes improves threefold, highlighting P3F’s potential in high-frequency and high-Q resonance applications. In addition to the resonators, this work exhibits fabricated filters based on various layers of LN. The filter based on a single P3F LN exhibits a center frequency ( f_c ) of 6.2 GHz, a bandwidth of 1.04 GHz, and a minimum insertion loss (IL) of the first design has an f_c of 9.1 GHz, a bandwidth of 1.7 GHz, and a minimum IL of 1.2 dB, while the second design has an f_c of 8.9 GHz, a bandwidth of 1.58 GHz, and a minimum IL of 2.2 dB. The measured temperature coefficient of frequency (TCF) of bilayer and trilayer P3F resonators are −40 and −33 ppm/°C, respectively, highlighting the potential of thermal stability enhancement provided by the multilayer structure. These findings emphasize the considerable promise of P3F LN devices for next-generation wireless communication applications.