【摘要】 研究了用脉冲激光制备薄膜时激光烧蚀靶材的的全过程.从能量平衡原理出发,考虑气化带走热量的影响,分阶段地建立了含有气化项与热源项的适合于不同烧蚀阶段的热流方程,给出了相应的初始条件和边界条件.以单晶硅为例,用有限差分法进行模拟计算,得到了靶材在各个阶段温度随时间以及气化速度随时间的演化规律.结果表明,靶材熔融前(0<t≤τm),在固定位置,温度随时间推移而升高,且距离靶面越近,变化率越大.在同一时刻不同位置,温度随着热扩散距离增加而下降;靶材熔融后(τm<t≤τ),靶材表面的蒸发效应使得表面温度显著低于未考虑蒸发效应的计算结果;在激光辐照强度接近相爆炸能量豫值时,蒸发速度随时间的变化由于气体动力学效应和逆流现象将显著放缓.更多还原

【Abstract】 The whole ablation process of target during the pulsed laser preparation thin films is studied. Based on the energy conservation theory, the considered vaporization effect, the heat flux equations are presented, including heat resource and vaporization team for different ablation stages, and the corresponding initial and boundary conditions are given. A finite difference method is employed to make simulation calculation. Taken Si target as an example, the evolvement of temperature and the vaporization characteristics are obtained, the results shower that during the period of 0<t≤τ_m, at a fixed location, the temperature increased with the ablation time t. the less the heat diffusion distance x, the faster the variety rate of the temperature is. At the same time, in different location the temperature decreases gradually along with the increase of the heat diffusion distance. When the vaporization happens on the tartan surface, the surface temperature is far lower than that without considering the vaporization effect. When the laser intensity reaches the value near the phase explosion energy threshold, increased ratio of the vaporization velocity, and will evidently decrease because of the gas dynamic effects and strong back streaming.更多还原