Study On Acoustic Wave Properties Of LiNbO₃ Thin Film With Multilayer Structure

With the rapid growth of communication technology,the development of high-frequency devices is very fast.The development of micro-nano processing technology and piezoelectric film technology has made miniaturization of high-frequency devices possible.Lithium niobate piezoelectric films have excellent acoustic properties.The multilayer structures formed by the combination of lithium niobate piezoelectric films and different substrate materials have been widely used in the preparation of high-frequency broadBand devices.In this paper,the acoustic wave device of lithium niobate single crystal thin film multilayer structure is taken as the research object,and the wave propagation characteristics in surface acoustic wave device and bulk acoustic wave resonator are analyzed and studied.In this paper,the surface acoustic wave device based on LiNbO3 single crystal thin film with multilayer structure is analyzed by simulation.The modal and frequency response analysis shows that the resonant frequency of this new type of SAW device is about 320MHz,and the electromechanical coupling coefficient is 2.55%.As one of the most important components of surface acoustic wave devices,the design parameters of interdigital transducers are important factors that affect the device performance.The resonant frequency and phase velocities of the devices at different electrode thicknesses and metallization rates of the interdigital transducers were investigated and analyzed.With the increase of the electrode thickness and metallization rate,the resonant frequency and the phase velocity were simultaneously reduced.It can be seen that electrode thickness and metallization ratio are factors that need to be considered when designing surface acoustic wave devices.Based on the research of surface acoustic wave devices,the working principle of the surface acoustic wave gas sensor is simulated.The polyisobutylene gas sensing membrane has good frequency-concentration characteristics in the air in the adsorbed air.The frequency shift of the sensor is obtained by simulation which about 1.412 ppm/Hz.With the increasing requirement of radio frequency,bulk acoustic wave resonators have great research value because of their frequency filters used in communication applications.In this paper,the finite-element simulations show that bulk acoustic wave resonators based on LiNbO₃single-crystal thin-film multilayer structures have multi-mode resonance characteristics in the wide frequency range of 2³ GHz,resonance frequency at about 2.535 GHz,quality factor up to 2863,and the k_eff is about 5%,with the advantages of high frequency,high quality factor and high electromechanical coupling coefficient.Different sizes,materials,and effective electrode areas of the top electrode have an effect on the resonant frequency and frequency response of the resonator.The resonators with different top electrode sizes were experimentally tested,and the results obtained from the simulation results were similar,and the influence trends were consistent.