Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition

Abstract

Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm3/V.s) and concentration (×1019 cm−3). XPS indicated the presence of both W6+ and W4+ in the TiO2 matrix, with the substitutional doping of W4+ inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2.

Synthesis of W‐doped TiO2 by low‐temperature hydrolysis: Effects of annealing temperature and doping content on the surface microstructure and photocatalytic activity

“…[30] By increasing the annealing temperature of pure TiO 2 and W-TiO 2 , we observed the shift of the peak E g (1) (144 cm −1 ) toward lower wavenumbers and the reduction of its intensity. [34] 2.4 | Diffuse reflectance UV-Vis spectroscopy UV-Vis spectra, in diffuse reflectance mode, were recorded to characterize the light absorption properties and determine the band gap (E g ) values ( Figure 3). The broadening is due to the generation of oxygen vacancies by the displacement of oxide ions from their normal lattice.…”

“…[34,40] The increase in oxygen vacancies generates more surface defects in the synthesized nanoparticles, shown using the XPS spectra of O 1s ( Figure 6). Bearing in mind that Ti(IV) and W(VI) are the predominant cations in the lattice of the W-TiO 2 samples, and the doping is substitutional; Ti(III) sites are generated in the lattice, as is observed from the XPS results.…”

Synthesis and characterization of nanostructured TiO2 and TiO2/W thin films deposited by co-sputtering

“…We can see a clear difference between the films with and without tungsten doping with thermal treatment, Figures 3.b and 3.d respectively. The film without tungsten doping show a brighter surface, while the other seems granular and less porous, therefore, the W addition to the film could provide it with more thermal stability [3,21]. The thickness of the films is visible in Figure 4, there we can see that both samples have less than 1 µm thick, after the annealing treatment samples rearrange into a more stable and dense structure which causes them to lose about 0.1µm of thickness.…”

“…The TiO 2 is known for its existence in three polymorphic forms: Anatase (tetragonal), rutile (tetragonal) and brookite (orthorhombic), where the tetragonal crystallographic structures, anatase and rutile, are the most used. The rutile phase has a bandgap of 3.10 eV [1,2], with a high refraction index [3,4] and a better chemical and thermal stability. The rutile phase has applications as optical coatings, solar energy converters or protective layers in microelectronics applications.…”

Doping anatase TiO2 with group V-b and VI-b transition metal atoms: a hybrid functional first-principles study

“…2 Anatase itself is a wide band gap (∼3.4 eV 3 ) semiconductor, which is low cost, nontoxic and chemically stable. On doping with group V-b elements Nb 4,5 , Ta 6 or with W (group VI-b) 7 it becomes a good transparent conducting oxide (TCO).…”