c轴倾斜的压电薄膜结构中的体声波研究

The bulk acoustic waves in piezoelectric thin film structures of hexagonal crystal system with tilted c-axis, such as ZnO, AlN, play an important role and have promising application prospect in the fields of biosensing and chemical sensors. Based on piezoelectric theory, combined with viscoelastic mechanics and liquid mechanics, we will investigate the propagation properties of bulk acoustic waves in piezoelectric thin film with tilted c-axis, develop the analytical method for bulk acoustic waves, and study the effects of crystal structure and symmetry, properties of materials, thickness of electrodes, and interfacial conditions on modes, frequency, electromechanical factor, quality factor and impedance combination with the experimental analysis and numerical simulation. The influencing factors of pure shear-mode will be investigated for piezoelectric thin film structures with tilted c-axis. The bulk acoustic waves in multilayered piezoelectric thin film structures will be analyzed with consideration of Brag reflection, interface and electrodes. Furthermore, we will probe into the effects of adsorption membrane with viscoelasticity and functionally graded changes on bulk acoustic waves. The vibration of thin film carrying distributed and nonuniform mass loading will be investigated thoroughly. We will also make clear the effects of acceleration and initial stresses on propagation of bulk acoustic waves. Through all these work, we will bring forward the useful and important analytical method for the design of piezoelectric thin film bulk acoustic wave resonators with tilted c-axis.

c轴倾斜的ZnO、AlN等六方晶系（6mm）压电薄膜结构中的体声波在生物化学传感领域具有重要应用前景。本项目依据压电弹性理论，结合粘弹性力学和流体力学，深入研究c轴倾斜的压电薄膜结构中体声波传播特性，建立体声波传播的分析方法并探究晶体对称性、材料性能、电极厚度、界面条件等对模态、频率、机电耦合系数、品质因数和阻抗等的影响；分析c轴倾斜的压电薄膜结构中纯剪切体波模态的影响因素以及Zig-Zag或其他形式的多层压电薄膜结构的体声波和Brag反射层、复杂界面、金属电极对体声波传播的作用；深入探究液体环境中压电薄膜结构中的体声波及其与吸附膜的相互作用并考虑吸附膜性质的粘弹特性和梯度变化；进一步研究分布质量载荷、非均匀质量载荷对薄膜体声波的影响；分析加速度和初应力等因素对谐振器体声波传播模态和频率的效应，从而为c轴倾斜的压电薄膜体声波谐振器设计提供重要的分析方法和参考依据。

本项目研究了多种复杂因素作用下压电薄膜结构中体声波传播特性，为压电薄膜体声波谐振器的设计提供重要参考依据。研究了均匀分布的阵列微直梁对c轴倾斜的ZnO压电薄膜结构中体声波的作用，获得了其谐振频率，揭示了微直梁的几何参数变化对谐振特性的影响。我们提出了一种新的压电陀螺仪结构，由c轴倾斜的两层AlN构成，其输出电压对多个参数敏感，分析了角速度对振动频率的影响。AlN和ZnO薄膜有利于做出比石英晶体和铌酸锂晶体更小的陀螺仪。研究了具有粘性流体的c轴倾斜的压电薄膜结构中体声波特性，获得粘性系数与体声波频率特性之间的关系，其结果有助于研制高灵敏度流体传感器。研究了具有粘弹性吸附膜的压电薄膜结构对体声波效应，采用Kelvin模型描述粘弹性层的本构关系。进一步考虑了压电材料的粘性对振动频率的影响，发现材料粘弹性显著影响体声波振动特性。研究了具有布拉格反射层的固体装配型的薄膜体声波谐振器体波特性，分析了布拉格反射层以及电极对于振动频率的作用。研究了具有叉指电极的薄膜体声波滤波器的振动特性，滤波器由硅基体上的AlN或者ZnO薄膜构成，具有接地电极和驱动电极，工作于厚度伸展振动模态。分析得到了谐振频率和模态等振动特征，揭示了几何参数对振动特性的影响，发现对适当设计的滤波器存在能陷模态，其振动在电极附近较强，而随着远离电极振动衰减。进一步研究了考虑电极效应的AlN压电薄膜硅基体结构中的剪切波，研究了非均匀厚度的石英晶体板厚度剪切和厚度扭转振动，以及瞬态热效应对谐振器频率和振幅的影响。本项目研究深化了对压电薄膜结构体声波特性的认识，揭示了多种复杂因素作用下谐振器频率特性的变化规律，获得了不同结构参数和材料特性对压电薄膜结构体声波的影响，为有关压电薄膜体声波谐振器的设计提供重要参考依据。