The structure and optical properties of sol-gel derived transparent titanium dioxide thin films doped with niobium

Niobium doped TiO₂ thin films ((TiO₂)_1-x(Nb₂O₅)_x, x=0, 0.2%, 0.4%, 0.6%, 0.8%) were prepared on ITO-coated substrates by sol-gel method and spin coating technology followed by rapid thermal annealing treatment (RTA). The effects of various processing parameters, including Nb content (x=0-0.8%) and annealing temperature, on the growth and properties of thin films were investigated. Structural characteristics by X-ray diffraction analysis indicated that the doping of Nb₂O₅ in the TiO₂ without change the anatase structure of TiO₂ thin films. The absorption coefficient shows energy gap were decreased with increasing Nb₂O₅ content from 3.29 eV for x=0 to 3.2 eV for x=0.8%. Doping TiO₂ with Nb₂O₅ can lower its band gap and shift its optical response to the visible region. It should be effective as a visible-light-driven photocatalyst.