The role of surface oxygen vacancies upon WO3 conductivity

Gillet, M.; Lemire, Céline; Gillet, E.; Aguir, Khalifa

doi:10.1016/s0039-6028(03)00477-1

Cited by 139 publications

(98 citation statements)

References 29 publications

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“…The conductivity is calculated from the experimentally determined resistance R, which is monitored during the three heating and cooling cycles. The activation energy of conduction, E A , was frequently interpreted using the Arrhenius equation between 300 and 700 K. Our results are compatible with the principle results of conductivity of WO 3−x thin films [19][20][21][22][23][24][25][26]. It is obtained from the following formula:…”

Section: Resultssupporting

confidence: 86%

Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling

Mohammad

2009

Acta Phys. Pol. A

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Reduction processes of WO 3 nanopowder either with carbon or with hydrogen were observed using X-ray powder diffraction and transmission electron microscope. The phase transformations, separation, grain size and electrical conductivity of WO 3−x nanopowder during reductions via partial pressure high energy ball-milling have been studied. During the carbon-reduction process the monoclinic WO3 structure transforms to nonstoichiometric Magneli phases W40O118, WO2.9 and finally to WO2 and W mixed phases. The Magneli WO3−x phases exhibit specific fringe contrast imaging of well-ordered crystallographic shear planes. In comparison, the monoclinic WO3 structure transforms to hydrate WO3·1/3H2O, hexagonal WO3, non-stoichiometric WO2.7 and finally to WO2 and W mixed phases during the hydrogen-reduction process. The inclusion of hydrogen atoms between the WO6 octahedral structure shifts the reduction steps to lower milling times. It demonstrates that the formation of hydrate WO3 phases enhances the amenability of the system to reduction. The activation energy for conduction was deduced from the Arrhenius equation and was found to depend on oxygen partial pressure or presence of the hydrogen atoms. The defect band model was used for interpretation of these behaviors. It supposes that the surface oxygen vacancies introduce donor levels in the gap of semiconductor, so free electrons are produced by reduction.

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Section: Resultssupporting

confidence: 86%

Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling

Mohammad

2009

Acta Phys. Pol. A

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“…Annealing the implanted samples at 300°C for 10 min leads to a drastic increase in resistivity, the resistivity increases to the range 10 7 Ωcm. The increase in resistivity upon annealing at temperatures higher than 70ºC is attributed to the oxidation of some oxygen vacancies [19]. Possibly the borosilicate substrate degrades upon annealing for long time and affects the resistivity.…”

Section: Electrical Propertiesmentioning

confidence: 99%

Physical properties of erbium implanted tungsten oxide films deposited by reactive dual magnetron sputtering

Mohamed

Anders

2007

Thin Solid Films

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Amorphous and partially crystalline WO 3 thin films were prepared by reactive dual magnetron sputtering and successively implanted by erbium ions with a fluence in the range from 7.7 × 10 14 to 5 × 10 15 ions/cm 2 . The electrical and optical properties were studied as a function of the film deposition parameters and the ion fluence. Ion implantation caused a strong decrease of the resistivity, a moderate decrease of the index of refraction and a moderate increase of the extinction coefficient in the visible and near infrared, while the optical band gap remained almost unchanged. These effects could be largely ascribed to ion-induced oxygen deficiency. When annealed in air, the already low resistivities of the implanted samples decreased further up to 70ºC, whereas oxidation, and hence a strong increase of the resistivity, was observed at higher annealing temperatures.

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“…According to Gillet et al [35] the conductivity of WO 3 is governed by the non-stoichiometry which originates from oxygen vacancies. The high resistivity value stayed almost constant upon increasing to 0.840.…”

Section: Lbnl-59900mentioning

confidence: 99%

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Mohamed

Anders

2006

Surface and Coatings Technology

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Thin films of tungsten oxynitrides were prepared by dual magnetron sputtering of tungsten using argon/oxygen/nitrogen gas mixtures with various nitrogen/oxygen ratios.The presence of even relatively small amounts of oxygen led to close-to-stoichiometric WO 3 , with little incorporation of nitrogen, therefore the films were labeled as WO x (N y ). Oxygen had a great effect not only on the composition but on the structure of WO x (N y ) films, as shown by Rutherford backscattering and x-ray diffraction, respectively. Significant incorporation of nitrogen occurred only when the nitrogen partial pressure exceeded 89% of the total reactive gas pressure. Sharp changes in the stoichiometry, deposition rate, room temperature resistivity, electrical activation energy and optical band gap were observed when the nitrogen/oxygen ratio was high. The deposition rate increased from 0.31 to 0.89 nm/s, LBNL-59900 1 the room temperature resistivity decreased from 1.65 × 10 8 to 1.82 × 10 -2 Ωcm, the electrical activation energy decreased from 0.97 to 0.067 eV, and the optical band gap decreased from 3.19 to 2.94 eV upon nitrogen incorporation into the films. WO x (N y ) films were highly transparent as long as the nitrogen incorporation was low, and were brownish (absorbing) and partially reflecting as nitrogen incorporation became significant.

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The role of surface oxygen vacancies upon WO3 conductivity

Cited by 139 publications

References 29 publications

Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling

Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling

Physical properties of erbium implanted tungsten oxide films deposited by reactive dual magnetron sputtering

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

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The role of surface oxygen vacancies upon WO3 conductivity

Cited by 139 publications

References 29 publications

Synthesis, Separation and Electrical Properties of WO3-xNanopowders via Partial Pressure High Energy Ball-Milling

Synthesis, Separation and Electrical Properties of WO3-xNanopowders via Partial Pressure High Energy Ball-Milling

Physical properties of erbium implanted tungsten oxide films deposited by reactive dual magnetron sputtering

Structural, optical, and electrical properties of WOx(Ny) films deposited by reactive dual magnetron sputtering

Contact Info

Product

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Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling

Synthesis, Separation and Electrical Properties of WO_3-xNanopowders via Partial Pressure High Energy Ball-Milling