Micro- and Nanoscale Heat Transfer in Femtosecond Laser Processing of Metals
Micro- and Nanoscale Heat Transfer in Femtosecond Laser Processing of Metals
复制标题
金属飞秒激光加工中的微米级和纳米级传热
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. K. Chen
中科院分区：
文献类型：
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作者：
Yuwen Zhang;D. Tzou;J. K. Chen
超快激光材料加工已经受到了极大的关注，由于在微米和纳米尺度的微型化设备的制造的需求不断增长。传统的唯象定律（例如傅里叶热传导定律）在微尺度范围内受到挑战，应该采用双曲或双相滞后模型。在超快激光与金属相互作用过程中，电子和晶格处于不平衡状态。提出了各种可用于描述非平衡传热的双温模型。本文还提出了一个半经典的两步加热模型来研究超短激光加热引起的金属热输运。半经典和唯象双温模型之间的主要区别在于前者包括电子漂移的影响，这可能导致与后者在更高强度和更短脉冲激光加热下显着不同的电子和晶格温度响应。在较高的激光能量密度和/或短脉冲下，晶格温度可以超过熔点并且发生熔化。当晶格通过传导热量而冷却时，液相将重新凝固。研究了金薄膜和金微粒的超快熔化和再凝固。在更短的脉冲宽度下，飞秒激光对金属的加热产生亚皮秒范围内的热电子的爆炸力，该爆炸力沿着非平衡热流作用于金属晶格。我们的工作，采用抛物两步加热模型来研究热电子爆炸的多层金属薄膜的效果也被提出。
Ultrafast laser material processing has received significant attention due to a growing need for the fabrication of miniaturized devices at micro- and nanoscales. The traditional phenomenological laws, such as Fourier's law of heat conduction, are challenged in the microscale regime and a hyperbolic or dual phase lag model should be employed. During ultrafast laser interaction with metal, the electrons and lattices are not in equilibrium. Various two-temperature models that can be used to describe the nonequilibrium heat transfer are presented. A semi-classical two-step heating model to investigate thermal transport in metals caused by ultrashort laser heating is also presented. The main difference between the semiclassical and the phenomenological two-temperature models is that the former includes the effects of electron drifting, which could result in significantly different electron and lattice temperature response from the latter for higher-intensity and shorter-pulse laser heating. Under higher laser fluence and/or short pulse, the lattice temperature can exceed the melting point and melting takes place. The liquid phase will be resolidified when the lattice is cooled by conducting heat away. Ultrafast melting and resolidification of the thin gold film and microparticles were investigated. At even shorter pulse width, femtosecond laser heating on metals produces a blasting force from hot electrons in the sub-picosecond domain, which exerts on the metal lattices along with the non-equilibrium heat flow. Our work that employs the parabolic two-step heating model to study the effect of the hot-electron blast in multi-layered thin metal films is also presented.