基于压电光子学效应的声表面波可视化研究

Surface acoustic wave (SAW) technologies have been extensively used as micro actuators for pumping or mixing of fluids and manipulation of micrometer sized objects, such as microparticles, droplets, and biological cells, which is highly desirable for many applications in biology, chemistry and engineering. The visualization of SAW is essential for characterizing the acoustic field in these operations, as well as for designing and testing interdigital transducers (IDTs). However, probing the acoustic propagation in these applications remains expensive, time-consuming, and often difficult to perform in situ. Technologies such as laser vibrometry, laser heterodyne interferometry, scanning acoustic force microscopy, and stroboscopic topography, do not allow direct access to close systems, as would be the case inside a channel, and are impractical for an in situ and rapid analysis. In this proposal, we demonstrate that the propagation path of SAWs excited with IDTs can be visualized by coupling acoustic field to piezophotonic effect. Piezophotonic effect, known as a two-way coupling effect between piezoelectricity and photoexcitation properties, is proposed to initiate the mechanoluminescence (ML) during the conversion process between mechanical strain and light emission. According to the piezophotonic effect, the interaction of the acoustic wave with the ML film gives rise to ML film deformations and results in light emission. We will study the influences of the characterizations of ML films and SAWs on the piezophotonic luminescence. The physical mechanism of the acoustic field induced ML and the theoretical model to describe the light emission induced by coupling acoustic field to piezophotonic effect will be proposed. Moreover, the method not only enables the visualization of the SAW path itself, but it also provides the information of the acoustic radiation pressure, which could improve the performance of visualized SAW-based actuator prototypes.

声表面波微驱动技术在生物医学和化学分析等领域具有广阔的应用前景，近年来引起了学界极大的关注。能够原位实时地检测声表面波的传播特性对于声表面波在微驱动领域的应用具有重要意义。当前的检测方法面临仪器精密昂贵，运行费用高，对环境振动敏感，检测费时费力，不能实现原位实时快速检测等诸多问题。压电光子学效应能够实现机械应力到发光的转换。申请人研究组在国际上较早开展压电光子学效应研究。本项目拟在前期工作基础上，将应力发光薄膜与声表面波器件集成，基于压电光子学效应实现声表面波的可视化。研究工作预期将掌握应力发光薄膜特性以及声表面波参数对声波驱动应力发光性能的影响规律，理解声表面波耦合动态调制应力发光的物理机制，建立相应的物理模型。拟研发的新型可视化声表面波微驱动原型器件将验证新引入的发光功能不仅满足声表面波的现场快速可视化检测，而且有助于提高声表面波技术在微驱动和微操控领域的性能。

作为声学、电子学、材料学、信息科学以及微机电系统（MEMS）等领域交叉的新兴技术，声表面波在移动通信、传感检测、微驱动器等领域具有广阔的应用前景。本项目主要围绕声表面波的可视化和声表面波增强功能器件展开研究。按照研究计划，展开基于压电光子学效应的应力发光薄膜的可控制备，频率响应特性及相关机理研究。研究发现应力发光性能与发光薄膜自身特性以及外加应力条件（包括应力强度、频率、施加方式等）密切相关。应力发光材料ZnS:Mn高频驱动下的宽带近红外发光来自于 Mn2+离子团聚，而高频应力激发下ZnS:Mn应力发光的频率截止现象与应力发光的动力学过程密切相关。应力产生的压电势调节压电半导体能带结构，激发被陷阱俘获的电子从陷阱中逸出以非辐射跃迁方式与空穴复合，并将能量传递给掺杂金属离子实现应力发光。在高频激发下，释放电子后的缺陷无法重新捕捉填充电子，导致高频激发下的应力发光饱和与截止现象。研究了声表面波耦合调控稀土离子发光的物理规律。研究了脉冲激光沉积过程沉积温度、氧压、激光能量、脉冲频率等参数对稀土离子掺杂铁电薄膜微观结构和光电特性的影响。声表面波耦合调控稀土离子发光归因于声表面波传播所引起的铁电基质晶格畸变，局域晶体场改变稀土离子受迫电偶极跃迁几率。基于稀土离子掺杂铁电薄膜与传播的声表面波所伴随的应变和压电场的相互作用，通过监测稀土离子发光特性实时反映声表面波的振幅、频率、损耗等参数，实现声表面波的可视化检测。声表面波的压电场效应会导致光生载流子电子空穴对发生空间分离，并进行极性传输，从而能有效地提升半导体光电器件性能。研究了基于非晶氧化镓基异质结和氧化镓基单极势垒日盲雪崩探测器的制备与性能测试，探索了声表面波增强氧化镓基日盲紫外探测器的规律，加深对声表面波增强氧化镓基探测器工作机制的理解。通过本项目的研究，共发表SCI收录论文16篇（含中科院1区论文11篇，2区论文3篇）。申请发明专利2项。培养研究生8名。