Fabrication of self-organized TiO2 nanotubes from columnar titanium thin films sputtered on semiconductor surfaces

Self-organized nanotube arrays of TiO2 have been grown from titanium (Ti) thin films deposited on p-type Si(1 0 0) substrates. Structural and morphological characterizations carried out by X-ray diffraction and scanning electron microcopy indicate that the sputtered crystalline Ti thin films used for subsequent anodization are hexagonally closed packed (hcp-Ti) and show a columnar morphology. Electrochemical anodization of the Ti films was carried out by potentiostatic experiments in 1 M H3PO4 + 1 M NaOH + 0.5 wt% HF electrolyte at room temperature. The TiO2 nanotubes on a semiconductor substrate have an average tube length of approximately 560 nm, diameter in the order of 80 nm and wall thickness approximately 20 nm.