Surface nanostructuring of silicon

Irradiation with polarized laser light of 248-nm wavelength induces the formation of periodic undulations ∼10-nm-highon flat silicon substrates. The wavelength of these periodic structures is a function of the light wavelength and the angle of incidence of the laser beam. Linear arrays of silicon nanoparticles with fairly uniform size that extended up to a millimeter were formed if the irradiation was performed using polarized light. When non-polarized laser light with the same fluence was used to illuminate an initially flat surface, non-aligned nanoparticle strings were obtained. However, if part of the irradiated area was microstructured, nanoparticle linear arrays resulted in the vicinity of the microstructured region. An analysis on the evolution of these nanostructures is presented. Nanocolumns could be grown on top of every cone of a microstructured surface upon cumulative laser irradiation with non-polarized light, reaching a height of ∼3 μm and a diameter of 100–200 nm. The mechanisms of nanocolumn origin and growth are analyzed.