提出了一种将激光烧蚀制备的纳米Si晶粒按尺寸大小进行分离的新方法。在10 Pa高纯环境气体Ar下,采用波长为308 nm的XeCl准分子激光器,固定激光单脉冲能量密度为3 J/cm2,激光烧蚀电阻率为3000 Ω·cm的高纯单晶Si靶,在等离子羽轴线正下方2.0 cm处平行放置一系列单晶Si或玻璃衬底来收集纳米Si晶粒。拉曼(Raman)谱测量结果显示,在距靶平行距离为0.5～2.8 cm范围内,所制备的薄膜中均有纳米Si晶粒形成。利用扫描电子显微镜(SEM)观察了样品的表面形貌,对图中的纳米Si晶粒统计分析表明,随着离靶平行距离的增大,所形成的纳米Si晶粒的平均尺寸逐渐减小。从烧蚀动力学角度对实验结果进行了定性解释,因为不同尺寸的纳米Si晶粒获得了不同的水平速度,所以在重力作用下实现了尺寸的自然分离。

A new method dispersed Si nanoparticles in the process of pulsed laser ablation (PLA) was proposed in this paper. A single crystalline Si target with high resistivity of 3000 Ω·cm was ablated by a XeCl excimer laser (wavelength: 308 nm, laser fluence: 3 J/cm2) in high-pure Ar gas at the ambient pressure of 10 Pa, and the Si nanoparticles were systemically deposited on glass or single crystalline Si substrates located at a distance of 2.0 cm under the plume. The Raman spectra indicate that Si nanoparticles were obtained in the samples at different horizontal distances, 0.5～2.8 cm, from Si target. The scanning electron microscopy (SEM) images show that the average size of Si nanoparticles gradually decreased with increasing the distance from the target. The experimental results were explained by ablation dynamics. Because Si nanoparticles with different masses gained the different horizontal velocity, Si nanoparticles were dispersed according to their sizes under gravitation.