TY - JOUR
T1 - High-frequency dielectric characterization of electronic defect states in co-sputtered W-doped TiO2
AU - Delegan, N.
AU - Teranishi, T.
AU - El Khakani, M. A.
N1 - Funding Information:
The authors would like to acknowledge financial support from the NSERC (the Natural Science and Engineering Research Council of Canada) and the FRQNT (Le Fonds de Recherche du Québec-Nature et Technologies) through its strategic Network “Plasma-Québec.”
Publisher Copyright:
© 2019 Author(s).
PY - 2019/5/28
Y1 - 2019/5/28
N2 - Tungsten-doped titanium dioxide (TiO2:W) has been reported to have increased photocatalytic performance as compared to undoped TiO2. The exact mechanism behind this has been debated. Consequently, the purpose of this work is twofold: (i) synthesize TiO2:W films with improved optoelectronic properties and (ii) refine the understanding of photocharge properties in tungsten-doped TiO2. An in situ radio frequency magnetron-sputtering deposition process was used to fabricate undoped (TiO2), oxygen deficient (TiO2-x), and tungsten-doped (TiO2:W) films with varying dopant levels. X-ray photoelectron spectroscopy measurements showed the presence of both WTi″ and WTix type dopants that led to significantly reduced oxygen vacancy (VO) densities. These observations were corroborated by X-ray diffraction analysis, which revealed that the improved stoichiometry resulted in a marked enhancement of the rutile phase as compared to the sub-stoichiometric (VO-doped) samples. Critically, high-frequency dielectric spectroscopy measurements revealed an optimal tungsten doping level of ∼2.5 at. %. This point showed the greatest tungsten induced reduction in the 2[TiIII]-[VO″] defect pair ϵ′ contribution, i.e., almost two orders of magnitude. Finally, this dielectrically observed reduction in VO was correlated to an increase in photocharge decay lifetimes. In other words, photocharge lifetimes increased in accordance with the reduction of VO defects brought on by tungsten doping.
AB - Tungsten-doped titanium dioxide (TiO2:W) has been reported to have increased photocatalytic performance as compared to undoped TiO2. The exact mechanism behind this has been debated. Consequently, the purpose of this work is twofold: (i) synthesize TiO2:W films with improved optoelectronic properties and (ii) refine the understanding of photocharge properties in tungsten-doped TiO2. An in situ radio frequency magnetron-sputtering deposition process was used to fabricate undoped (TiO2), oxygen deficient (TiO2-x), and tungsten-doped (TiO2:W) films with varying dopant levels. X-ray photoelectron spectroscopy measurements showed the presence of both WTi″ and WTix type dopants that led to significantly reduced oxygen vacancy (VO) densities. These observations were corroborated by X-ray diffraction analysis, which revealed that the improved stoichiometry resulted in a marked enhancement of the rutile phase as compared to the sub-stoichiometric (VO-doped) samples. Critically, high-frequency dielectric spectroscopy measurements revealed an optimal tungsten doping level of ∼2.5 at. %. This point showed the greatest tungsten induced reduction in the 2[TiIII]-[VO″] defect pair ϵ′ contribution, i.e., almost two orders of magnitude. Finally, this dielectrically observed reduction in VO was correlated to an increase in photocharge decay lifetimes. In other words, photocharge lifetimes increased in accordance with the reduction of VO defects brought on by tungsten doping.
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U2 - 10.1063/1.5087061
DO - 10.1063/1.5087061
M3 - Article
AN - SCOPUS:85066120310
VL - 125
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 20
M1 - 205103
ER -