<i>In situ</i>
            investigations of the phase change behaviour of tungsten oxide nanostructures

Thummavichai, Kunyapat; Wang, Nannan; Xu, Fang; Rance, Graham A.; Xia, Yongde; Zhu, Yan

doi:10.1098/rsos.171932

Cited by 65 publications

(65 citation statements)

References 30 publications

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“…[27,45,47] Blue arrow labelled peaks located at 128.8 cm -1 and 135.4 cm -1 were assigned to fully oxidised WO3, while the peaks at 156.1 cm -1 and 301.9 cm -1 were assigned to substoichiometric WO3-x, indicating the presence of oxygen vacancies in edge tungsten oxides. [48][49][50][51] It has been widely studied that air-exposure caused significant influence on oxygen deficiency in TMOs. [28,32,52] For example, only one-hour air-exposure led to sharply reduced WF of MoOx accompanied with obviously increased oxygen vacancies, nonetheless our six-month air-exposure.…”

Section: Resultsmentioning

confidence: 99%

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Han

Liu

et al. 2019

Adv Materials Inter

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Transition metal oxides (TMOs) with high work function (WF) show promising properties as unipolar p-type contacts for transition metal dichalcogenides. Here, ambipolar field-effect transistors (FETs) enabled by bilayer WSe2 with self-assembled TMOs (WO2.57) as contacts are reported. Systematic material characterizations demonstrated the formation of WO2.57/WSe2 heterojunctions around nanoflake edges with Se atoms substituted by O atoms after air-exposure, while pristine properties of WSe2 almost sustained in inner domains. As-fabricated FETs exhibited both polarities, implying WO2.57 with lowered WF at edges can serve as both the p-type and n-type contact for inner WSe2. Noteworthy, greatly reduced contact resistance and enhanced channel current were achieved, compared to the devices without WO2.57 contacts. Linear drain-source current relationship from 77 K to 300 K indicated the ohmic contact between edge WO2.57 and inner WSe2. Density functional theory calculations further revealed the WO2.57/WSe2 heterojunction formed a barrier-less charge distribution. These nm-scale FETs possessed remarkable electrical conductivity up to ~ 2600 S/m, ultra-low leakage current down to ~ 10-12 A, robustness for high voltage operation and air stability, which even outperformed pristine WSe2 FETs. Theoretical calculations revealed the high conductivity was exclusively attributed to the air-induced WO2.57 and its further carrier injection to WSe2.

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Section: Resultsmentioning

confidence: 99%

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Han

Liu

et al. 2019

Adv Materials Inter

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“…High-resolution TEM images confirm the crystallinity and the size of pristine and Nb-WO 3 materials (Figure 3). The nanowire appears as a single crystal of monoclinic WO 3 , as confirmed by selected area electron diffraction (SAED) analysis [55]. We were not able to detect any secondary phases in the presence of niobium.…”

Section: Morphologic and Structural Investigationsmentioning

confidence: 68%

The Influence of Nb on the Synthesis of WO3 Nanowires and the Effects on Hydrogen Sensing Performance

Zappa

2019

Sensors

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Hydrogen sensing is becoming one of the hottest topics in the chemical sensing field, due to its wide number of applications and the dangerousness of hydrogen leakages. For this reason, research activities are focusing on the development of high-performance materials that can be easily integrated in sensing devices. In this work, we investigated the influence of Nb on the sensing performances of WO3 nanowires (NWs) synthetized by a low-cost thermal oxidation method. The morphology and the structure of these Nb-WO3 nanowires were investigated by field emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD), Raman and X-ray photoelectron (XPS) spectroscopies, confirming that the addition of Nb does not modify significantly the monoclinic crystal structure of WO3. Moreover, we integrated these NWs into chemical sensors, and we assessed their performances toward hydrogen and some common interfering compounds. Although the hydrogen sensing performances of WO3 nanowires were already excellent, thanks to the presence of Nb they have been further enhanced, reaching the outstanding value of more than 80,000 towards 500 ppm @ 200 °C. This opens the possibility of their integration in commercial equipment, like electronic noses and portable devices.

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“…From the s5m sample annealed at 500 °C, additional low intensity peaks located around 142, 304, 668, and 677 cm −1 rise, which can be due to the partial oxidation of tungsten, which provokes the formation of non-stoichiometric tungsten oxide (WO 3−x ) [57,58,59].…”

Section: Resultsmentioning

confidence: 99%

Study of the Thermal Annealing on Structural and Morphological Properties of High-Porosity A-WO3 Films Synthesized by HFCVD

et al. 2019

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High-porosity nanostructured amorphous tungsten OXIDE (a-WO3) films were synthesized by a Hot Filament Chemical Vapor Deposition technique (HFCVD) and then transformed into a crystalline WO3 by simple thermal annealing. The a-WO3 films were annealed at 100, 300, and 500 °C for 10 min in an air environment. The films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and UV–vis spectroscopy. Results revealed that the a-WO3 films were highly porous, composed of cauliflower-like structures made of nanoparticles with average sizes of 12 nm. It was shown that the effect of annealing on the morphology of the a-WO3 films leads to a sintering process. However, the morphology is conserved. It was found that at annealing temperatures of 100 °C, the a-WO3 films are of an amorphous nature, while at 300 °C, the films crystallize in the monoclinic phase of WO3. The calculated bandgap for the a-WO3 was 3.09 eV, and 2.53 eV for the film annealed at 500 °C. Finally, the results show that porous WO3 films preserve the morphology and maintain the porosity, even after the annealing at 500 °C.

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In situ investigations of the phase change behaviour of tungsten oxide nanostructures

Cited by 65 publications

References 30 publications

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

The Influence of Nb on the Synthesis of WO3 Nanowires and the Effects on Hydrogen Sensing Performance

Study of the Thermal Annealing on Structural and Morphological Properties of High-Porosity A-WO3 Films Synthesized by HFCVD

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In situ investigations of the phase change behaviour of tungsten oxide nanostructures

Cited by 65 publications

References 30 publications

Ambipolar and Robust WSe2 Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Ambipolar and Robust WSe2 Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

The Influence of Nb on the Synthesis of WO3 Nanowires and the Effects on Hydrogen Sensing Performance

Study of the Thermal Annealing on Structural and Morphological Properties of High-Porosity A-WO3 Films Synthesized by HFCVD

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Product

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About

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides

Ambipolar and Robust WSe₂ Field‐Effect Transistors Utilizing Self‐Assembled Edge Oxides