Synthesis and characterization of structural, optical and electrical properties of chromium and nickel doped titanium dioxide thin films

Abstract

Un-doped TiO2 and TiO2 with 2, 4, 6, and 8 atomic (at.)% Cr and Ni doped thin films have been successfully deposited by a simple and cost-effective spray pyrolysis deposition (SPD) technique. The surface morphology of the films was observed by the FE-SEM images and found that 6 and 8 at.% TiO2:Cr films display fibrous pattern with diameter 0.65 and 1.10 μm, respectively and the rest of all the films consist of agglomerated particles. From X-ray diffraction analysis, the TiO2 thin films were found to have tetragonal anatase crystal structure up to 6 at.% Cr doping and for 2, 4, 6, and 8 at.% Ni doping. For 8 at.% Cr doping anatase-rutile mixed crystalline phase was found. Un-doped TiO2 film has a crystallite size of 35 nm and for TiO2:Cr films, 46 to 35 nm and TiO2:Ni films conceded with 45 to 63 nm, respectively. Fizeau fringe technique was used to determine the thickness of un-doped TiO2 film 165 nm and 165 to180 nm for TiO2:Cr films and 170 to190 nm for TiO2:Ni films, respectively. UV-Vis data were used to determine absorbance, transmittance, refractive index, dielectric constant, optical conductivity, and optical band gap of the films. The optical band gap values are decreased from 3.40 to 2.70 eV for TiO2:Cr, and the band gap values are increased from 3.38 to 3.58 eV for TiO2:Ni thin films. The temperature dependent resistivity has been studied using the 4-point probe technique and it is decreased with rising temperature. The resistivity of the films is decreased with Cr content, in contrast to Ni content.