TiO2 nanotubes:: Tailoring the geometry in H3PO4/HF electrolytes

In the present work, we investigate the formation of self-organized titanium oxide nanotube layers at different fluoride concentrations and potentials in H3PO4 electrolytes. We demonstrate that in optimized phosphate/HF electrolytes, in contrast to other electrolytes the tube length and diameter can be controlled over a wide range by the applied potential. It was found that for potentials between 1 and 25 V tubes could be grown with any desired diameter ranging from 15 to 120 nm combined with tube length from 20 nm to 1 mu m. The diameter and the length depend linearly on the voltage. These findings represent an unprecedented level of control in the geometry of anodic TiO2 nanotubes. (c) 2006 Elsevier B.V. All rights reserved.