Direct imprinting of high resolutionTiO2 nanostructures

Abstract

We demonstrate a different approach to direct nanoimprint lithography of oxides, in particularTiO2, using the metal methacrylate route which not only gives very high resolution (∼20 nm) but alsoprovides yields of ∼ 100% over areas > 1 cm × 1 cm.TiO2 was imprinted using apolymerizable liquid ‘TiO2 resin’ consisting of a mixture of titanium methacrylate, ethylene glycoldimethacrylate, and azobis-(isobutyronitrile). The resin underwentfree radical polymerization when imprinted using a silicon mold at110 °C with pressures as low as 10 bar. Polymerization strengthens the imprinted structures, thereby giving ∼ 100% yield after demolding. Heat-treatment of the imprinted structures at400 °C resulted in the loss of organics and their subsequent shrinkage (∼75%) without the loss of integrity or aspect ratio, and converted them toTiO2 nanostructuresas small as ∼ 20 nm wide. Furthermore, our method demonstrates that large imprinted areas of sub-100-nmfeatures can be achieved by sub-micron molds which translate into huge cost savings withthe added flexibility of direct patterning of unary as well as multi-component oxides.