Microstructuring of silicon with femtosecond laser pulses

Abstract

We report that silicon surfaces develop an array of sharp conical spikes when irradiated with 500 laser pulses of 100-fs duration, 10-kJ/m² fluence in 500-Torr ${\mathrm{SF}}_{\mathrm{6}}$ or ${\mathrm{Cl}}_{\mathrm{2}}.$ The spikes are up to 40-μm tall, and taper to about 1-μm diam at the tip. Irradiation of silicon surfaces in ${\mathrm{N}}_{\mathrm{2}},$ Ne, or vacuum creates structured surfaces, but does not create sharp conical spikes.