【摘要】 研究了高能短脉冲激光薄膜制备的整个烧蚀过程.首先建立了基于超热理论的烧蚀模型,然后利用较为符合实际的高斯分布表示脉冲激光输入能量密度,给出了考虑蒸发效应不同阶段的烧蚀状态方程.结合适当的边界条件,以Si靶材为例,利用有限差分法得到了靶材在各个阶段温度随时间和烧蚀深度的演化分布规律及表面蒸发速度与烧蚀深度在不同激光辐照强度下随时间的演化规律.结果表明,在脉冲激光辐照阶段,靶材表面的蒸发效应使得靶材表面温度上升显著放缓;在激光辐照强度接近相爆炸能量阈值时,蒸发速度与蒸发厚度的变化由于逆流现象将显著放缓.还得到了考虑了熔融弛豫时间及蒸发效应的固-液界面随时间的演化方程,这一结论较先前工作更具有普适性.更多还原

【Abstract】 The whole ablation process of target during the pulsed laser preparation of thin films is studied in this paper. An ablation model of targets in which the vaporization is taken account is present based on the superheated theory. Different heat flux equations for different stages are then established. Finally, as using Si as the target, a finite difference method is employed to simulate the space- and time-dependence of temperature in the target. Vaporization velocity and vaporization thickness evolutions with different laser fluence are investigated. The dependence of solid-liquid interface location S(t) on time which takes into account the melting relaxation time is derived too. The results show that the vaporization strongly affects the surface temperature in the pulsed laser ablation. When the laser intensity reaches near the phase explosion energy threshold, the vaporization velocity and ablation depth will evidently decrease because of the gas dynamic effects. This result is more appropriate than that obtained in previous works.更多还原