(502e) Vanadium Doping Induced Structural and Optical Modifications in TiO2 Thin Films

In this work, we present the customized structure and morphology of vanadium (V) doped TiO₂ thin films synthesized on glass substrates a growth rate of ~ 0.6Å/s at 500^oC. The sputtering targets of pure and V doped TiO₂ with three concentrations of V (1.0, 1.5 and 2.0 atomic percentage (at.%)) were prepared from powders. XRD patterns confirmed the grown TiO₂ films had the anatase phase. In the doped TiO₂ films, the crystallite size reduced by almost half when V concentration increased from 0 to 2 at.% systematically.  Incorporation of V in the TiO2 crystal led to the enhanced growth of (211) planes, which significantly modified the grain geometry from the faceted to the elongated as observed in the SEM images. This was simulated by the use of VESTA code. Raman spectroscopy showed phonon confinement, increased nonstoichiometry and asymmetry in bonding with increased V concentration. The XPS spectra confirmed an increase in the nonstoichiometry in TiO₂ due to V substitution in the structure. It is suggested that the difference in the valance states of Ti and V produced a clear difference in the ionic radii of the two, which resulted in the augmentation of non-equilibrium (211) planes and hence resulted in the emergence of modified morphology of the synthesized TiO₂ thin films. Photoluminescence spectroscopy also revealed the effect of vanadium states on the band gap states.  Pure TiO₂ did not show any luminescence in the visible, how ever, incorporation of vanadium with different percentages clearly demonstrated its incorporation in V³⁺, V⁴⁺ and V⁵⁺ states, which were analysed quantitatly and related to structural modifications.  The modified films would be useful for photocatalysis not only structurally but for their improved optical properties.