Single- and multishot femtosecond laser ablation of silicon and silver in air and liquid environments: Plume dynamics and surface modification

The experimental study of the single-shot 1030-nm femtosecond laser ablation of bulk silicon and silver in air and liquid media (deionized water, isopropyl alcohol) is reported. The main laser ablation mechanisms were studied via analysis of the resulting microcrater surface morphology and elemental composition in single- and multi-shot (number of pulses N = 10, 100) regimes by scanning electron microscopy with a built-in module for energy-dispersive X-ray spectroscopy. It was concluded, that multi-shot ablation in liquids leads to the lesser extent of the processed surface oxidation, than in dry conditions. The monitoring of the ablative plumes dynamics was implemented with the use of time-resolved emission spectroscopy in the non-filamentation regime, corresponding to the formation of nanoparticles without fragmentation of the ablation products. It was demonstrated, that the lifetime of the plume emission in liquid is significantly shorter, than in air: 5 and 15 ns, correspondingly, for silicon, and 10 and 30 ns for silver.