A new electrochemical lithography - Fabrication of self-organized titania nanostructures on glass by combined anodization

Self-organized anodic titania nanostructures (nanoporous films, nanodot, or nanorod arrays) were fabricated by a combined anodization from superimposed Al/Ti layers sputter-deposited on glass substrates. The specimens were first anodized in a constant potential mode to form nanoporous anodic alumina films with different pore sizes and intervals, which worked as electric filters and rendered a through-mask anodization to the underlying titanium layer on glass. In the successive anodization, either transparent nanoporous titania films with parallel cylindrical pores (phi 20-40 nm, 50-75 nm interval, 980-1100 nm thick) or patterned titania nanoreliefs (quantum nanodot or nanorod arrays; phi 20-100 nm, 30-260 nm, height, 50-380 nm interval) were fabricated on glass substrates, depending on the anodizing characteristics of titanium in different electrolytes. Particularly, X-ray photoelectron spectroscopy analysis suggested that the nanoporous anodic titania films were composed of titanium oxide (Ti-IV) and a small amount of titanium nitride (Ti-III) included with dissociated nitrogen. The transparent nanoporous titania films were amorphous in as-anodized state and transferred into polycrystalline tetragonal anatase after heating at 873 K, both exhibiting an elevated transmittance throughout the ultraviolet and visible light range. (c) 2005 The Electrochemical Society. All rights reserved.