Self-organized metal nanostructures through laser-interference driven thermocapillary convection

Here the authors investigate self-organization and the ensuing length scales when Co films (1-8 nm thick) on SiO2 surfaces are repeatedly and rapidly melted by nonuniform (interference) laser irradiation. Pattern evolution produces periodic nanowires, which eventually breakup into nanoparticles exhibiting spatial order in the nearest-neighbor (NN) spacing lambda(NN2). For films of thickness h(0)>2 nm, lambda(NN2)proportional to h(0)(1/2) while the particle radius varies as r(p2)proportional to h(0)(1/2). This scaling behavior is consistent with pattern formation by a thermocapillary flow and a Rayleigh-like instability. For h(0)<= 2 nm, a hydrodynamic instability of a spinodally unstable film leads to the formation of nanoparticles. (C) 2007 American Institute of Physics.