Coupled Maxwell equations and semiclassical electronic and molecular dynamics simulation for analyzing laser ablation of silicon thin films

A coupled simulation scheme combining Maxwell equations with semiclassical electronic and molecular dynamics based on the electron force field model has been developed to enable the description of interaction dynamics among electrons, ions in a condensed matter, and electromagnetic waves at a practical computational cost. This method is applied to investigate laser ablation of a silicon thin film induced by intense 100-fs pulsed laser irradiation. The simulation with normal incidence shows that a highly elevated electron temperature caused by light absorption leads to the initial ejection of electrons from a surface after the pulse has passed, facilitated by enhanced thermal fluctuations and a destabilized structure at the surface induced by energy relaxation. Subsequently, the positive net charges at the disordered surfaces, resulting from missing electrons, cause a Coulomb explosion of the surface ions accompanied by electrons. The explosive expansion of the vapor leads to the formation of small cavities and further inhomogeneous vapor-vacuum separation during the phase explosion process. Thus, the presented simulation provides a comprehensive microscopic understanding based on interaction dynamics among electrons, ions, and light within the semiclassical framework.