TiO2 Nanotubes Film/FTO Glass Interface: Thermal Treatment Effects

  • Jelena Vujančević Institute of Technical Sciences of SASA
  • Andjelika Bjelajac University of Belgrade, Innovation Center of Faculty of Technology and Metallurgy
  • Katerina Veltruska Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science
  • Vladimir Matolin Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science
  • Zdravko Siketić Ruđer Bošković Institute
  • Georgios Provatas Ruđer Bošković Institute
  • Milko Jakšić Ruđer Bošković Institute
  • George E. Stan National Institute of Materials Physics, Laboratory of Multifunctional Materials and Structures
  • Gabriel Socol National Institute for Lasers, Plasma, and Radiation Physics, Lasers Department, Laser-Surface-Plasma Interactions Laboratory
  • Ion N. Mihailescu National Institute for Lasers, Plasma, and Radiation Physics, Lasers Department, Laser-Surface-Plasma Interactions Laboratory
  • Vladimir B. Pavlović University of Belgrade, Faculty of Agriculture
  • Djordje Janaćković University of Belgrade, Faculty of Technology and Metallurgy

Abstract

Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO samples were sintered at 450, 550 and 630oC, in ambient air. The thermal treatment did not influence the crystal phase composition, preserving in all cases the anatase single phase. As expected, the crystalline anatase quality improved with the annealing temperature. Nevertheless, slight differences in nanotubular morphology, such as the appearance of grains inside the walls, were observed in the case of the sample sintered at 630oC. Chemical analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the substrate to TiO2. For the substrate was used FTO glass whose top layer consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and Time-of-Flight Elastic Recoil Detection Analysis were carried out to study the elemental depth profile of the films. It was found that the temperature of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse towards the TiO2 NTs surface for the samples annealed at 450 and 550oC. The diffusion is however hindered in the case of the heat treatment at 630oC. Besides, the Ti diffusion into the SnO2 underlayer was observed, together with the formation of TiO2/SnO2 interfaces. One then expected but not a great difference in absorption between samples, since all contained anatase phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of Sn was however detected for the sample annealed at 550oC, which accounts for a slight red absorption shift. The importance of controlling the annealing parameters of the anodized TiO2/FTO structures was highlighted through the formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can play an essential role in increasing the photoperformances of TiO2 NTs/FTO based structures of photovoltaic cells.

Published
2022-05-03
Issue
Vol 54 No 2 (2022)
Section
Articles

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