Femtosecond laser surface structuring of silicon in dynamic irradiation conditions

The process of surface structuring of silicon in dynamic irradiation conditions is investigated by analyzing the features of the surface structures generated on a target moving at different scanning velocities under the irra-diation by a 1030 nm femtosecond laser beam. Scanning electron microscopy analysis of the shallow linear craters produced in different experimental conditions allows characterizing the dependence of threshold fluence for the formation of surface structures (ripples and grooves) as well as their spatial periods on the effective number of laser pulses. Moreover, the effect of the accumulated laser fluence dose has been also addressed. Our findings evidence clear trends of the morphological features of the surface structure on the effective number of laser pulses as well as the existence of interesting differences in their characteristics when processing occurs at the same value of the accumulated laser fluence dose achieved by appropriate selection of laser pulse energy and scanning speed.