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 Si O2 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 λNN2. For films of thickness h0 >2 nm, λNN2 h0 12 while the particle radius varies as rp2 h0 12. This scaling behavior is consistent with pattern formation by a thermocapillary flow and a Rayleigh-like instability. For h0 ≤2 nm, a hydrodynamic instability of a spinodally unstable film leads to the formation of nanoparticles.