【摘要】 采用耦合一维双温模型的分子动力学方法研究了纳米级的铝膜在飞秒激光辐照下的熔化机制.这种方法不仅能够在原子水平上展现金属膜的各种微观行为,还能有效地描述金属膜的激光能量吸收、传递和金属电子热传导等过程.模拟结果表明,与其它金属相比,铝膜在飞秒激光辐照下的电子温度、晶格温度以及内部压力等呈现出不同的变化.铝膜在较高强度激光辐照下会很快发生全局一致的熔化,这与镍膜上下非均匀的熔化不同.并且由于铝的电子-声子耦合强度较高导致铝膜较镍膜和金膜熔化得更快.模拟结果显示,铝膜的熔化时间与实验测量的超快激光诱导的铝膜熔化时间一致.进而从理论上支持激光诱导的铝膜熔化是一个热力学熔化过程.更多还原

【Abstract】 A coupled computational technique, which combines the one dimensional two-temperature model and molecular dynamics, was used to study the melting dynamics of a nanoscale aluminum film irradiated by a femtosecond laser pulse. The model is capable of providing an atomic-level depiction of fast microscale processes in metals and gives an adequate description of laser light absorption, energy transfer, and fast electron heat conduction in metals. The simulation revealed that the electron temperature, lattice temperature, and laser induced pressure of the Al film were significantly different from those of Ni and Au films. The Al film melts globally soon after laser radiation and this is different from the Ni film, which goes through a step melting process. In addition, the Al film shows a much faster melting process than the Ni and Au films because of strong electron-phonon coupling. The melting time of the Al film by an ultrafast laser pulse is consistent with recent experimental observations, which supports the assertion that the laser induced melting of an Al film is a thermal process.更多还原