Fabrication of Well-Ordered High-Aspect-Ratio Nanopore Arrays in TiO2 Single Crystals

In this work a successful method for producing high-aspect-ratio nanopatterned single-crystal TiO 2 is presented. The method used is based on nanolithography involving swift heavy ion bombardment through a porous anodic alumina mask. Nanopatterning of large areas allows for fabrication of new devices, for example, photonic crystals and electrodes for energy storage and conversion. Crystalline TiO 2 also presents optimal characteristics for optical and catalysis applications. Samples were irradiated by MeV Br 7+ ions with fluencies ranging from 7.9 × 10 13 to 1.2 × 10 15 cm -2 . The high-energy Br 7+ ions induce latent tracks of amorphous material into the TiO 2 crystal suitable for selective etching by hydrofluoric acid. High-aspect-ratio (16) nanopatterned areas, up to 4 mm 2, were obtained in a single radiation spot onto single-crystalline TiO 2 .