Effect of Zr doping on the structural and electrical properties of spray deposited TiO2 thin films

Doping is an effective material re-engineering technique, which provides a possibility of improving properties of materials for different applications. Herein, a Zr-doped TiO2 thin film was deposited applying the chemical spray pyrolysis method and the influence of varying zirconium dopant concentrations on the properties of the film was studied. Morphological studies showed that the Zr–TiO2 films were homogeneous with smaller grain sizes compared to the undoped TiO2 films. As-deposited Zr–TiO2 films were amorphous while the undoped TiO2 films were crystalline with anatase structure as revealed by both X-ray diffraction and Raman spectroscopy studies. The optical band gap of the Zr–TiO2 film was higher (3.44 eV) than that of the undoped TiO2 films (3.13 eV) showing a strong dependence on the phase composition. As revealed by energy dispersive spectroscopy analysis, the Zr/Ti ratio in the film increased from 0.014 to 0.13 as the doping concentration in the spray solution was increased from 5 to 40 mol%. The current–voltage (I–V) characteristic revealed a reduction of the leakage current in the Zr-doped TiO2 film (6.06 × 10–5 A) compared to the undoped TiO2 films (1.69 × 10–3 A) at 1 forward bias voltage. The dielectric relaxation response at the oxide–electrode interface dipole was strongly influenced by the Zr doping concentration in the film.