超短脉冲激光辐照硅膜的热弹性
Thermoelasticity effect on Si film irradiated by ultra-short pulse laser
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摘要: 考虑到热电子崩力的影响，在基于玻耳兹曼理论弛豫时间近似的非线性自相关模型基础上，将晶格温度与应变速率相耦合，建立了超短脉冲激光作用下半导体材料的超快热弹性模型。在单轴应变条件下，利用有限差分法模拟了500 fs脉冲激光作用下2 μm厚硅膜内的载流子温度、晶格温度、载流子数密度、热应力和热电子崩力等的变化情况。结果表明：在低能量密度激光条件下，热弹性效应对半导体材料的影响很小；载流子温度达到峰值的时间比激光强度达到峰值的时间早，随后载流子数密度达到峰值，以及激光脉冲作用5 ps以后硅膜趋于总体热平衡；在脉冲辐照早期，非热平衡阶段形成的热电子崩力在超快损伤过程中起主要作用。Abstract: An ultrafast thermoelasticity model for the thermomechanical behaviors in semiconductors irradiated by ultra-short pulse laser is presented based on the complete self-consistent model. It accounts for the coupling effect between lattice temperature and strain rate, as well as for the hot-electron-blast effect in momentum transfer. A finite difference method is developed for solving the coupled, nonlinear, transient differential equations under uniaxial strain condition. Numerical analysis is performed for a 2 μm silicon film heated by a 500 fs laser pulse to obtain the temporal and spatial evolution of the carrier temperature and density, the lattice temperature, the thermal stress and the hot-electron blast force. The results show that the ultrafast thermoelasticity effect has very littl
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