Femtosecond laser-induced periodic surface structures formation on bismuth thin films upon irradiation in ambient air

Abstract

The formation of laser-induced periodic surface structures (LIPSS) on a bismuth thin film with a femtosecond laser is reported for the first time. The surface structures were generated at normal incidence in air environment with fluence below the ablation threshold. The effect of the number of pulses on the LIPSS morphology and on their chemical composition was investigated. The results show the generation of low spatial frequency LIPSS (LSFL), accompanied by regularly distributed nanoparticles. The LIPSS are oriented perpendicular to the laser polarization with a period ΛLSFL that doesn't show a significant variation with the number of pulses (∼1µm). In contrast to previous studies for LIPSS formation on bismuth films under ns laser irradiation [Opt. Mater. Express 7, 1777 (2017)], in the present case no oxidation was observed.