Ultraviolet femtosecond, picosecond and nanosecond laser microstructuring of silicon: structural and optical properties

Abstract

The effect of laser pulse duration on the morphology, composition, crystallinity and optical properties of self-organized Si microcones fabricated using 248 nm laser pulses (500 fs, 5 ps and 15 ns) in an SF(6) atmosphere, is presented in this paper. Despite distinct differences in the morphology, the Si cones show similar structure and composition independently of the laser pulse duration used: a core of single-crystalline Si, covered by a few hundred nanometer thick, sulfur-doped nanocrystalline Si layer, where no amorphous Si is present. The obtained features exhibit strong below-bandgap absorptance, making them excellent candidates for Si based photodetectors with improved spectral response.