Excimer laser induced thermal evaporation and ablation of silicon carbide

Abstract

It is well known that the ablation of material from a solid target exhibits a threshold behaviour. The ablation of material is usually performed at laser fluences significantly above the threshold and considerably high ablation rates are achieved. No particular effort has been devoted to the study of the low energy range, near the ablation threshold. This regime is of particular interest in what it might give insight on the reason for the presence of a threshold and then on the physical processes underlying the ablation itself. We have measured the ablation rate of silicon carbide single crystal targets induced by XeCl laser pulses as function of the laser fluence over a wide range, from below to well above the threshold. We have investigated the angular distribution of the emitted material through the measurements of the thickness of the deposited films; also, the morphology of the craters left in the irradiated targets as a function of the laser fluence has been monitored. We have modelled the surface heating and melting due to the absorption of the laser light, and calculated the surface temperature as function of time by using the well known “thermal model” often used for the laser annealing. Thermal evaporation from the liquid surface can then be calculated for each laser pulse energy and compared to the observed ablation rates.