Fabrication of zinc oxide nanostructures using solvent-assisted capillary lithography

Abstract

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 byspin coating on a solid substrate and subsequently a nanopatterned PUA mold wasbrought into conformal contact with the substrate under slight physical pressure(∼3.5 bar). Afterannealing at 230 °C for 4 h, well-defined ZnO nanostructures formed with feature size down to∼50 nm, aided by capillary rise and solvent evaporation. It was found that the height ofcapillary rise depended highly on the applied pressure. A simple experimental setup wasdevised to examine the effects of pressure, revealing that the optimum pressure ranged from3.5 bar to 5 bar. Also, ZnO nanorods could be selectively grown on patterned regions usingthe seed layer as a pseudocatalyst when the width of the seed layer was larger than∼200 nm.