外加氩气流下脉冲激光烧蚀制备纳米硅晶粒成核生长动力学研究

为研究纳米硅晶粒成核生长动力学过程,采用脉冲激光烧蚀(PLA)技术,在室温,50～200 Pa的氩气氛围中,通过引入垂直于烧蚀羽辉轴线的外加气流,在水平放置的衬底上沉积了一系列纳米Si晶薄膜.扫描电子显微镜( SEM)、拉曼(Raman)散射和X射线衍射(XRD)检测结果表明,未引入气流时,衬底上相同位置处晶粒尺寸随气体压强的增大逐渐减小；在距靶1 ～2cm范围内引入气流后,尺寸变化规律与未引入气流时相反.通过分析晶粒尺寸及其在衬底上的位置分布特点,结合流体力学模型和热动力学方程,分析得出在激光能量密度一定的条件下,环境气体压强、烧蚀粒子温度和密度共同影响着纳米晶粒的成核生长.

Dynamics of Nucleation and Growth of Si Nanocrystal Grains Prepared by Pulsed Laser Ablation with Extra Ar Gas Flow

In order to study dynamics of nucleation and growth of nanocrystal grains,the silicon crystal thin films were deposited on horizontal substrate by pulsed laser ablation through introducing extra gas flow that vertical to plume axis at room temperature,pressure of Ar was 50-200 Pa.Results of SEM,Raman and XRD indicated the size of grains deposited on the same position of substrates decrease gradually as gas pressure increasing without gas flow.After the gas flow was introduced at 1-2 cm apart from target,the variation law of grains’ size was contrary.Based on analyzing the size and distribution position of grains on substrates,when laser fluence is constant,nucleation and growth of grains are common effected by gas pressure,temperature and density of ablated atoms combining with hydrodynamics model and thermokinetic equation.