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Numerical modeling of laser-induced picosecond ultrasound in micro-nano thin films |
1.Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2.School of Mechanical Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China |
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Abstract Based on two temperature model(TTM) and thermalelastic theory, finite element numerical model of femtosecond laser-induced picosecond ultrasound was applied in investigating laser interaction of Al/Si3N4 and Al/Si3N4/Si multilayer thin films. The temperature fields of electron and lattice in Al film were caculated by the finite element method to analyze the surface displacement response and strain in thin films. The computational result from TTM theory was compared with that from classical fourier heat transfer theory. The comparison indicates that TTM theory is suitable for picosecond ultrasonic investigation. According to numerical analysis, the strain amplitude is small with wide waveform. The peaks of displacement response spectrum on Al surface are induced by ultrasound reflection within the interface of films.
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