Vis-IR black nano-silicon produced by wet femtosecond-laser nanotexturing/hyperdoping and nanosecond-laser annealing

Compared to conventional oven-based annealing in ambient air of a silicon surface layer nanotextured and hyperdoped in CS2 fluid by femtosecond laser (black nano-silicon), low-intensity nanosecond laser annealing facilitated its delicate recrystallization, preserving quasi-regular nanoscale topography and high n-doping concentration by sulfur donor impurities. The retained and recrystallized topography of the laser-annealed nanosilicon with a few-percent doping level exhibits broadband optical absorption in the visible-near-infrared (vis-NIR) range, rendering this optical material promising for photovoltaic and IR-photonic applications.