Influence of laser beam profile on morphology and optical properties of silicon nanoparticles formed by laser ablation in liquid

In this study, silicon nanoparticles (NPs) were produced by pulsed laser ablation in a liquid, aiming to investigate the influence of a laser beam profile on the properties of the resultant NPs. Morphology, inner structure, and phase composition of the formed NPs were characterized by means of ultraviolet-visible spectroscopy, high-resolution transmission electron microscopy, and Raman and photoluminescence spectroscopies, and the correlation of the NP properties with the laser beam profile was studied. Three different beam profiles were selected, namely, a Bessel beam produced using an axicon, an annular profile formed using a combination of an axicon and a converging lens, and a Gaussian beam focused on the surface of a Si target using the same converging lens. In all the schemes, a nanosecond Nd³⁺:YAG laser with a pulse duration of 10 ns operating at its fundamental harmonic (1064 nm) was used as an ablation source. The beam profile has been shown to be a crucial factor significantly influencing morphology and composition of the nanostructures produced. Namely, the conditions generated using a Bessel beam profile favored the production of nanostructures having elongated filament-like morphology. The synthesized colloidal Si NPs are suggested for applications as a component of electrode materials in supercapacitors and batteries.