Structural properties of silicon nanoparticles obtained via femtosecond laser ablation in gases at different pressures

摘要

In this paper, we report on the effect of buffer gas on silicon nanoparticle formation in femtosecond laser ablation process. For the first time the nonmonotonic dependence of the silicon nanoparticle sizes on the gas pressure is obtained. Distributions of the particles on the size received by means of atomic-force microscopy indicate reducing the Si nanoparticle diameter with pressure increase from 50 to 700 mbar for helium and nitrogen atmospheres, with the minimal nanoparticle size up to 5 nm reaching in helium. At further increase in pressure there is a growth of the nanoparticles size and distribution becomes wider. Using argon as a buffer gas results in larger nanoparticle sizes than in helium and more complicated dependence of the size distribution on the argon pressure. The electron diffraction and Raman scattering in the formed silicon nanoparticles evidence their crystallinity.