Non-Fourier Energy Transport in Silicon Thin Films during Femtosecond Laser Heating
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摘要: 在双曲双步输运模型基础上建立数值模型，针对超短脉冲激光作用下硅薄膜的微观能量输运过程展开理论研究。针对电子、晶格超快温升响应过程的数值模拟结果表明，电子作为主要能量载子在几皮秒内主导了能量输运过程。电声子之间的能量耦合系数主要依赖于电子温度，而不是晶格温度。能量耦合过程由于非平衡电子的弹道式输运而呈现非局域性。热波的传播速度与电子能量传播速度有相同量级，而大于硅材料中的声子平均速度。模型预测与相关实验结果吻合。Abstract: A numerical model which is based on the hyperbolic two-step model is developed to investigate the microscopic energy transport in silicon thin films during ultra-fast laser heating. It is observed that, electrons dominate energy transport within a few picoseconds. The coupling processes between electrons and phonons are non-local due to the ballistic transport of electrons, and the coupling coefficient is found to be much more strongly dependent on electron temperature than lattice temperature. The speed of heat wave propagation is the same magnitude as that of the electron energy transport. Predictions from the numerical model agree with available experimental data during ultra-fast laser heating.
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Key words:
- femtosecond laser /
- non-Fourier transport /
- numerical simulation /
- silicon thin films
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