The optical band and optical constants of non-crystalline WO3 thin films doped with Ti deposited by dip coating in sol-gel

The optical constants and optical band gaps of the non-crystalline tungsten oxide (WO3) thin films doped with Ti deposited by dip coating method onto glass substrates with different atomic concentrations of Ti have been investigated by optical characterization method. The films were annealed at 160 ͦC to guarantee maximum transparency. The amorphous crystal structure of the as grown and annealed films were revealed by XRD. The optical data of WO3 thin film have revealed a direct allowed transition band gap of 3.1 eV, which increases slightly up to 3.6 eV by increasing Ti concentration due to the formation of TiO2 new phase that may be introduced within the amorphous structure. The effect of Ti concentration on the film thickness and optical constants (refractive index, absorption coefficient and dielectric constants) of these films has been also investigated. The films thickness was found to increase with increasing doping concentration from 0.373 to ≈ 0.7µm due to the increase in the liquid viscosity, as expected. The room temperature refractive index, which was calculated from the reflectance and transmittance data, allowed the identification of the dispersion and oscillator energies lattice dielectric constant and static dielectric constant of these films, which show that WO3 thin films doped with Ti can be used as UV sensors, where 10% Ti doping is the best sensor.