Facile Size-Tunable Fabrication of Functional Tin Dioxide Nanostructures by Multiple Size Reduction Lithography

A novel ultraviolet (UV)-assisted imprinting procedure that employs photosensitive tin(II) 2-ethylhexanoate is presented for the facile size-tunable fabrication of functional tin dioxide (SnO2) nanostructures by varying annealing temperatures. These imprinted SnO2 nanostructures were also used as new masters for size reduction lithography. SnO2 lines down to 40 nm wide were obtained from a silicon master with 200 nm wide lines by simply performing size reduction lithography twice. This leads to 80 and 87.5% reduction in the width and height of imprinted lines, respectively. An imprinted pattern annealed at 400 °C demonstrated transmittance greater than 90% over the range of 350–700 nm, which is high enough to make the pattern useful as a transparent SnO2 mold. This demonstrated approach allows the accessibility to size-tunable molds, eliminating the need for conventional expensive imprinting masters with very fine structures, as well as functional SnO2 nanostructures, potentially useful in applications where ordered surface nanostructures are required, such as photonic crystals, biological sensors, and model catalysts.