Surface microstructuring and long-range ordering of silicon nanoparticles

Pulsed-laser irradiation was used to induce the formation of linear arrays of nanoparticles that can extend over millimeter distances. On flat surfaces, the irradiation induces the fragmentation and clustering of a thin silicon film pulsed-laser deposited on silicon into nanoparticles that grow to 30-40 nm in diameter. The nanoparticles aggregate into clusters that migrate, forming short curvilinear groups that exhibit a short-range ordering. If a region containing a microscopic roughness is introduced, the nanoparticles are forced to align into long and remarkably straight lines with line spacing very close to the laser wavelength. A close connection is established between the nanoparticle alignment and the evolution of laser-induced periodic surface structures. The microscopic roughness solely serves as a trigger to produce the alignment.