A Novel Non-Contact Technique for Dynamic Loading of Thin Film Materials Using Finite Amplitude Mechanical Stress Waves

本项目旨在开发一种新的基于激光的技术，用于产生有限振幅的表面声应力波。所提出的技术将有助于理解薄膜材料在超声频率下的非线性弹性响应。这一发展将导致定量测量的各种非线性弹性性能，包括;脱粘和断裂强度的薄膜界面，使用非线性弹性应力波。该技术使用聚焦成线的激光源在样品表面上通过热弹性效应产生平面表面声应力波。激光产生的应力波监测使用的路径稳定的迈克尔逊干涉仪。通过将激光线源以表面波的相速度在样品表面上扫描，应力波振幅随距离不断放大。该技术将使加载薄膜材料的应变幅度的数量级为0.01，应变速率大于每秒一百万。 该技术的非接触性质允许应力波的产生和传播过程的精确建模，从而可靠地提取薄膜材料properties.If该项目是成功的，所提出的技术将能够定量评估的机械可靠性和基于薄膜的小规模结构，包括MEMS和NEMS设备的稳定性。这些特性对于它们成功集成到更复杂的微电子器件中至关重要。此外，该项目还与各种教育活动相结合，包括研究生课程充实、研究生培训和面向高中生的外联活动。

This project seeks to develop a new laser based technique for the generation of finite amplitude surface acoustic stress waves. The proposed technique would facilitate the understanding of the nonlinear elastic response of thin film materials at ultrasonic frequencies. This development would lead to quantitative measurement of various nonlinear elastic properties including; decohesion and fracture strength of thin film interfaces, using nonlinear elastic stress waves. The technique uses a laser source focused to line on a sample surface to generate plane surface acoustic stress waves through the thermoelastic effect. The laser generated stress waves are monitored using a path stabilized Michelson interferometer. By scanning the laser line source on the sample surface at the phase velocity of the surface wave, the stress wave amplitude is amplified continuously with distance. The technique would enable loading thin film materials with strain amplitudes of the order of 0.01 with strain rates greater than one million per second. The contact-free nature of the technique allows for accurate modeling of the processes of stress wave generation and propagation, leading to reliable extraction of thin film material properties.If the project is successful, the proposed technique would enable the quantitative assessment of the mechanical reliability and stability of film based small scale structures including MEMS and NEMS devices. These properties are critical to their successful integration into more complex microelectronic devices. Furthermore, the project is integrated with various educational activities including, graduate course enrichment, graduate student training, and outreach activities to high school students.