(452b) Formation of Submicron/Nanoscale Features in Polymeric Or Colloidal Monolayers

The potential applications of two-dimensional order in submicron features have stimulated the development of cheap and fast fabrication techniques in recent years.  We have shown that electrohydrodynamic patterning of polymer films can produce features as small as 350 nm quickly and economically but dielectric breakdown imposes a fundamental limit at that scale.  To overcome that limit we turned to colloidal assembly via flow coating with nanoparticles of 50-100 nm diameters. Control of the deposition to achieve large areas of a uniform film is straightforward, but creating extensive crystalline domains in a close-packed monolayer is not. That motivated deposition of crystalline dispersions created by deionizing the solutions. The deposition followed faithfully a process model accounting for a power-law viscosity, but high shear rates disrupted the initial order producing domains similar to those achieved at dilute concentrations.  At low shear rates order was partially preserved but the domain sizes were still not extensive.  The most successful effort to create long-range order was achieved via the Langmuir-Blodgett process by adding excess free ligands to dispersions of gold nanoparticles. The excess ligands, oleylamine, not only improve the order upon deposition, but also anneal a poorly ordered array to form an ordered monolayer of 20,000 particles [C.Y. Lau, et al. Langmuir 27 3355 (2011)].