脉冲激光烧蚀中电声弛豫时间的确定

Numerical calculation of the electron-phonon coupling relaxation time in pulse laser ablation

为了提高脉冲激光制备薄膜的质量,准确掌握电声弛豫时间是关键,它对脉冲激光脉宽和能量密度的选取起着决定性的作用.文中以铝靶材为例,利用经典的双温方程通过时域有限差分法(FDTD)得到电子、离子亚系统的温度随时间和位置演化的图像,进而得到电声弛豫时间的准确值.这样便能准确划分热烧蚀和非平衡烧蚀,从而更好地控制激光的烧蚀过程.同时找出了电声弛豫时间随激光脉宽以及能量密度变化的规律.

The key to improving the quality of thin film prepared by pulse laser deposition, is to properly control the electron-phonon coupling relaxation time which determines the pulse duration and the laser fluence. Taking the aluminum targets as an example, we obtain the evolution temperature of electron subsystem and ion subsystem by solving the standard two temperature equation using the finite-difference time-domain （FDTD） method. Then, we obtain the electron-phonon coupling relaxation time, which can distinguish between the thermal ablation and the non-equilibrium ablation to ensure that we can control the process of pulse laser ablation well. In addition, we find out how does the electron-phonon coupling relaxation time change with the pulse duration and the laser fluence.