Fabrication of regular TiO ₂ nanoporous films derived by combining nanoimprint technique with sol-gel method

In this paper, honeycomb-like regular TiO ₂ nanoporous films deposited on different substrates including ITO glass and silicon wafer are fabricated by combining a nanoimprint technique with a sol-gel method. A novel soft polymer mold containing a thin layer of polymethylmethacrylate and a thicker layer of polydimethylsiloxane, which is obtained from an anodic aluminum oxide template, is carried out for the nanoimprint process. TiO ₂ precursor solution prepared by the sol-gel processing is used as the nanoimprinted material. After imprinting, the polydimethylsiloxane back layer is easily peeled off before the polymethylmethacrylate mold is chemically removed to avoid any demolding problem. The SEM images show that the honeycomb-like regular nanostructure of the initial anodic aluminum oxide template can be preserved completely on TiO ₂ via this method, and the XRD results indicate that there is a crystalline transition from amorphous to anatase of TiO ₂ after 450 °C heat treatment.