Effect of silicon target porosity on laser ablation threshold: molecular dynamics simulation

Ablation of a porous silicon target under irradiation with ultrashort laser pulse is simulated by means of the molecular dynamics approach. The number of ablated atoms is calculated for targets with different porosity under irradiation with wavelengths in ultraviolet (UV) and visible spectral ranges, which correspond to stronger and weaker absorption coefficient, respectively. An increase of the porosity to 80% leads to 1.5–3 times decrease of the ablation threshold compared to the bulk silicon, while a decrease of pores size from 2.5 to 1.2 nm leads to the stronger ablation threshold drop and the effect is stronger for the UV irradiation. The results are useful for laser processing of silicon-based targets and nanofabrication. (letter)