Investigation of liquid droplets, plume deflection, and a columnar structure in laser ablation of silicon

Abstract

The formation of a columnar structure, different expansion directions of the luminous (monomers) and obscure (droplets) plume species, and gradual deflection of the luminous plume are found to be interrelated in special experiments on pulsed laser deposition of Si. The obscure species always expands in the direction of incidence, which leads to a characteristic skewed angular distribution of the deposition rate. These observations are explained by the change of the microscopic mechanism of laser ablation from monomer evaporation at low local fluences to phase explosion at higher local fluences.