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Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputteringIn this work, we present preferred (004) texturing of sputter deposited titanium dioxide (TiO 2 ) films on glass substrates as a consequence of Nd doping at very slow growth rate. Nd concentration was varied from 0.0 to 2.0 atomic percent (at. %) in TiO 2 thin films deposited under identical growth conditions, i.e., the growth rate of 0.6 Å /s and at 500 C. At 2 at. % Nd, complete texturing along (004) plane was observed, as indicated by the X-ray diffraction analyses. Morphology of the deposited TiO 2 films from pure to 2 at. % Nd doped TiO 2 films showed faceted to planar growth. Visualization of electrical and structural analysis (VESTA) software revealed that the change in the morphology was due to preferential growth in (004) orientation. Raman spectroscopy highlighted the phonon confinement in the Eg mode, and a red shift was observed due to an increase in the anti-symmetry in bonding with increased Nd concentration. XPS results confirmed the variation in oxygen vacancy concentration along with the reduction of Ti and Nd valance states with the change in the dopant concentration. Our experiments confirmed that the substitution of Nd at Ti sites was responsible for texturing in (004) orientation and this was possible by growing films at a very slow rate. V C 2012 American Institute of Physics. [http://dx.

In this work, we present the customized modifications in the morphology and optical properties of vanadium (V) doped TiO 2 thin films sputter deposited on glass substrates at a growth rate of ∼0.6 Å/s at 500 °C. The sputtering targets of pure and V doped TiO 2 with three concentrations of V (1.0, 1.5, and 2.0 atomic percentage (at. %)) were prepared from powders. XRD patterns confirmed the grown TiO 2 films were anatase. In the doped TiO 2 films, the crystallite size reduced by almost half when the V concentration increased from 0 to 2 at. % systematically. Incorporation of V in the TiO 2 host lattice 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 and confirmed by structural simulation using VESTA code. The confinement of phonon modes was observed in the Raman spectra, which was attributed to the increased nonstoichiometry and enhanced asymmetry in bonding with increased V concentration. XPS spectra confirmed that the enhancement in the nonstoichiometry in TiO 2 was due to V substitution in the structure. It was suggested that the difference in the valence states of Ti and V resulted in the suppression of equilibrium (101) planes and augmentation of nonequilibrium (211) planes, which modified the grain morphology of the TiO 2 thin films. Photoluminescence (PL) spectroscopy clearly demonstrated the interplay of V defect states and O vacancy states. Pure TiO 2 showed mainly green luminescence related to oxygen vacancies; however, addition of V clearly demonstrated orange and red emission bands due to incorporation in V 3+ and V 5+ states, which increased at a much faster rate than oxygen vacancies on further addition of V. The PL results complimented the XPS findings.