Modelling of Pulsed Laser Ablation in Liquid via Monte Carlo techniques: The effect of laser parameters and liquid medium on the electron cloud

Abstract

Pulsed Laser Ablation in Liquid (PLAL) is a method for nanoparticle synthesis in which electron clouds are involved in the ablation process by providing electron heating which increases ablation efficiency. To better understand and control PLAL, this process was modelled herein via the Monte Carlo technique and the pure jump algorithm approach. From this model, it was shown that picosecond lasers produce fewer electrons with lower kinetic energy density than femtosecond lasers within a typical material processing period that contains many pulses. It was found that photon energies of 100 eV resulted in a primary electron: secondary electron ratio of about 1 : 1.6 regardless of the number of simulated primary electrons. The maximum energy of the electron cloud during a 20 fs laser pulse with 100 eV photons was 0.05 keV regardless of the boundary condition (number of primary electrons). An increase in photon energy from 100 eV to 200 eV caused an increase of over 600% in electron cloud energy. Such an increase would be expected to have an influence on various materials processing applications. Repetition rates of 10–100 kHz were found to have no influence on the electron cloud dynamics originating from the related differences in temporal sequences.