Electrochemical Fabrication and Properties of Highly Ordered Fe-Doped TiO2 Nanotubes

Highly-ordered Fe-doped TiO2 nanotubes (TiO(2)nts) were fabricated by anodization of co-sputtered TiFe thin films in a glycerol electrolyte containing NH4F. The as-sputtered TiFe thin films correspond to a solid solution of Ti and Fe according to X-ray diffraction. The Fe-doped TiO(2)nts were studied in terms of composition, morphology and structure. The characterization included scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, UV/Vis spectroscopy, X-ray photoelectron spectroscopy and MottSchottky analysis. As a result of the Fe doping, an indirect bandgap of 3.0 eV was estimated using Taucs plot, and this substantial red-shift extends its photoresponse to visible light. From the MottSchottky analysis, the flat-band potential (E-fb) and the charge carrier concentration (N-D) were determined to be -0.95 V vs Ag/AgCl and 5.0 x10(19) cm(-3) respectively for the Fe-doped TiO(2)nts, whilst for the undoped TiO(2)nts, E-fb of -0.85 V vs Ag/AgCl and N-D of 6.5x10(19) cm(-3) were obtained.