不同能量密度下脉冲激光烧蚀制备纳米Si晶粒成核生长动力学研究

Nucleation and Growth Kinetics for Si Nano-crystallites Prepared by Pulsed Laser Ablation under Different Energy Density

在室温、10 Pa氩气环境下,采用脉冲激光烧蚀(PLA)技术,通过改变激光能量密度,在烧蚀点正下方、与烧蚀羽辉轴线平行放置的衬底上沉积制备了一系列纳米Si晶薄膜。采用SEM、Raman散射谱和XRD对纳米Si晶薄膜进行了表征。结果表明:沉积在衬底上的纳米Si晶粒分布在距靶一定的范围内,晶粒尺寸随与靶面距离的增加先增大后减小;随着激光能量密度的增加,晶粒在衬底上的沉积范围双向展宽,但沉积所得最大晶粒尺寸基本保持不变,只是沉积位置随激光能量密度的增加相应后移。结合流体力学模型、成核分区模型和热动力学方程,通过模拟激光烧蚀靶材的动力学过程,对纳米Si晶粒的成核生长动力学过程进行了研究。

Abstract：A series Si nano-crystallites films were deposited on the substrates by pulsed laser ablation in Ar gas with fixed pressure of 10 Pa at room temperature through changing laser energy density, and the substrates were placed under the ablation spot and paralleled to the plume axis. The prepared Si nano- crystallites was charaterized by Scaning Electron Microscope （ SEM）, Raman （Raman） scattering spectraand X-ray Diffraction （XRD） . The results indicated that the position of nano-crystallites deposited on the substrates in an area from target, and the size increased first, and then decreased as the distance from target increasing. As the laser energy density increasing, the position distribution of Si nanoparticlesbecame broader bidirectional, that is, as the disappear position backward shifted, the initial position of nanoparticles appeared on substrates moved toward ablated spot at the same time. The maximum size of nanoparticles deposited on substrate did not change obviously, furthermore, the corresponding depositposition backward shifted. Combining with hydrodynamics model, nucleation division model and thermokinetic equation, the dynamics of nucleation and growth of nanoparticles were analyzed by simulating the dynamics process of laser ablated target.