Formation of conical silicon tips with nanoscale sharpness by localized laser irradiation

Abstract

The formation of conical silicon tips with nanoscale sharpness as a result of single-pulse localized laser irradiation is presented in this work. A Q-switched neodymium doped yttrium aluminum garnet nanosecond-pulse laser, emitting at its fourth harmonic of 266 nm, and a mask projection technique were used to generate circular laser spots, several microns in diameter. The irradiation of silicon-on-insulator films was performed in ambient, vacuum, or argon atmospheres, with the resulting structures and underlying substrate examined via atomic force microscopy and scanning electron microscopy. The laser fluence range within which tip formation occurs is strongly dependent on the irradiated spot size. Within this range, the height of the resulting tip increases with the fluence level, while nearly preserving the aspect ratio. The formation mechanism of these structures is briefly discussed in view of these results and other, related published work.