Ultra flexible pseudo-lamb wave RF resonators based on ZnO/PI and AlN/PI structures

A novel strategy has been proposed to implement high-performance ultra flexible RF resonators operated in the pseudo-Lamb wave modes. By integrating piezoelectric thin film (ZnO and AlN) with flexible polyimide (PI) substrate and using surface interdigital electrodes to excite acoustic waves, flexible RF resonators have been fabricated. Two-dimensional finite element analysis has been performed to study the mode shapes of the resonators and it is verified that these resonators are working in the pseudo-Lamb anti-symmetrical (A₀) and symmetrical (S₀) wave modes. Furthermore, the dispersive characteristics of the resonators have been theoretically calculated by using transfer matrix methods. The experimental results are in good agreement with the simulation results and theoretical calculations. As for the flexible resonator working in the S₀ mode based on ZnO/PI structure, a center frequency up to 800MHz and a high quality (Q) factor up to 1000 have been obtained.