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Zn-doped TiO2 nanotubes were fabricated by nanolaminated packing of alternating layers of TiO2 and ZnO by atomic layer deposition (ALD) using a polycarbonate (PC) membrane as a template. With 400 cycles of ALD, the nanotubes with a thickness of 28 nm and an outer diameter of 220 nm were obtained after removing the PC membrane by annealing at 450 °C. The doping concentration of ZnO in TiO2 depends on the precursor cycle ratio of ZnO to TiO2. With the precursor cycle ratio of ZnO : TiO2 at 0.04, a uniform bulk solubility of ∼8 at% is obtained, and the surface concentration of Zn is even higher, ∼16 at%. From the depth profiles measured by secondary ion mass spectrometry, Zn is uniformly distributed across the thickness, which is further confirmed by analyses of X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. Additionally, from the transmission electron microscopic observation, the highly doped anatase TiO2 exhibits some regions of severe deformation that results in localized solid-state amorphization.

Conformal parallel arrays of Al-doped TiO 2 nanotubes were fabricated by atomic layer deposition. TiO 2 /Al 2 O 3 bilayered shells were grown on a polycarbonate template by various cyclic sequences of TiO 2 and Al 2 O 3 . The doping level of Al could be tuned by the fraction of cycle number of Al 2 O 3 . From the depth profiles measured by second ion mass spectrometry, Al is uniformly distributed across the thickness, which is also supported by the analyses of X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. A uniform bulk solubility of~7 at.% and the surface concentration of~18 at.% were observed with the cycle ratio of Al 2 O 3 : TiO 2 at 0.04.

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