Synthesis and characterization of TiO2 nanotube film on fluorine-doped tin oxide glass

• A transparent ordered 12.5 μm-thick TiO2 nanotube film has been obtained.
• The structure zone model of Ti film has been presented.
• TiO2 nanotube film has a high transmittance in the visible light range
• The impedance of fluorine-doped tin oxide is responsive to light.

Highly ordered TiO2 nanotube array films were fabricated on conducting fluorine-doped tin oxide (FTO) glass substrate in NH4HF2/glycol electrolyte via anodization of Ti film, which was deposited by direct current magnetron sputtering. Ti films obtained by direct current magnetron sputtering method have three growth regions and that deposited at 410 °C has smooth surface which is favorable for the anodization. The anodization voltage affects the diameter of TiO2 nanotube and the reason has been discussed. A 12.5 μm-thick TiO2 nanotube array film has been obtained and exhibits a high transmittance of 32% in the visible light range. The bandgap of the thin film is calculated to be 3.08 eV based on the UV–vis transmission spectra, and its tail extends to 2.94 eV. The electrochemical impedance spectroscopy indicates that the impedance TiO2 nanotube film decreases after light illumination.