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 (SnO ₂) nanostructures by varying annealing temperatures. These imprinted SnO ₂ nanostructures were also used as new masters for size reduction lithography. SnO ₂ 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 350700 nm, which is high enough to make the pattern useful as a transparent SnO ₂ 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 SnO ₂ nanostructures, potentially useful in applications where ordered surface nanostructures are required, such as photonic crystals, biological sensors, and model catalysts.