Fabrication of zinc oxide nanostructures using solvent-assisted capillary lithography

We present a simple solvent-assisted capillary molding method to fabricate zinc oxide (ZnO) nanostructures using an ultraviolet (UV) curable polyurethane acrylate (PUA) mold. A thin film of the ZnO sol-gel precursor solution in methyl alcohol was prepared by spin coating on a solid substrate and subsequently a nanopatterned PUA mold was brought into conformal contact with the substrate under slight physical pressure (similar to 3.5 bar). After annealing at 230 degrees C for 4 h, well-defined ZnO nanostructures formed with feature size down to similar to 50 nm, aided by capillary rise and solvent evaporation. It was found that the height of capillary rise depended highly on the applied pressure. A simple experimental setup was devised to examine the effects of pressure, revealing that the optimum pressure ranged from 3.5 bar to 5 bar. Also, ZnO nanorods could be selectively grown on patterned regions using the seed layer as a pseudocatalyst when the width of the seed layer was larger than similar to 200 nm.