High-resolution core-level study of hexagonal WC(0001)

Håkansson, K. L.; Johansson, H. I. P.; Johansson, L. I.

doi:10.1103/physrevb.49.2035

Cited by 47 publications

(19 citation statements)

References 20 publications

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“…However, for metallic tungsten, it has been shown that this asymmetric parameter is very small and the approximation of using symmetrical gaussian-lorentzian functions is very small and the approximation of using symmetrical gaussian-lorentzian functions is very good [23], [27]. The position of this peak is not compatible with any tungsten oxide compound (the highest binding energy is 35.8 eV for WO , being W the highest oxidation state), or to the presence of tungsten carbide (WC, 31.8 eV [28]), as could be supposed because in all the samples a very small amount of carbon is present. It can not be also assigned to any thermal broadening, because its presence has been also observed in spectra acquired at liquid nitrogen temperature [29].…”

Section: Discussionmentioning

confidence: 87%

Surface and in depth chemistry of polycrystalline WO/sub 3/ thin films studied by X-ray and soft X-ray photoemission spectroscopies

et al. 2003

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The chemical composition of surface and underneath layers of WO 3 thin films, deposited by thermal evaporation and annealed in air at different temperatures, has been studied by means of soft X-ray and X-ray photoemission spectroscopies. Both the W 4f and valence band spectra have been analyzed. The analysis has been performed on samples as inserted and after an annealing process in an ultra high vacuum. The results have shown that the surface always presents a nonstoichiometric WO 3 compound, whose spectral components do not depend on the sample preparation. Instead, the study of the underneath layers has shown that the WO 3 films annealed in air at 500 C are highly stoichiometric and stable, while the samples heated in air at 300 C are much more sensitive to the vacuum thermal treatment showing the presence of reduced WO phases, whose intensity and chemical states change after the in vacuum annealing procedure.

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Section: Discussionmentioning

confidence: 87%

Surface and in depth chemistry of polycrystalline WO/sub 3/ thin films studied by X-ray and soft X-ray photoemission spectroscopies

et al. 2003

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“…The remaining carbon most likely originates from CO incorporated in the film during deposition. The shift in the C1s peak to lower energies may be due to the formation of tungsten carbide 35 along with the tungsten oxide. Evidence of carbide formation is also seen in the W peaks, and is discussed below.…”

Section: X-ray Photoelectron Spectroscopymentioning

confidence: 95%

Tungsten hexacarbonyl and hydrogen peroxide as precursors for the growth of tungsten oxide thin films on titania nanoparticles

et al. 2014

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W(CO) 6 and H 2 O 2 were used in an atomic layer deposition (ALD)-like process to grow thin WO x films onto TiO 2 powders in a fluidized bed reactor. Carbonyl precursors are not widely used in this application, so that deviations from an ideal ALD process, previously not examined with W(CO) 6 , were identified. The resulting WO x films were a result of both ALD-like and chemical vapor deposition-based growth modes. A chemical reaction mechanism incorporating a combination of these two growth modes was inferred. As the move to expand the range of ALD precursors meets with the desire to scale up these processes, the simultaneous appearance of both these growth modes is likely to become more and more common, and so understanding the interaction of these two types of surface reactions is key to progress in the field. The films were observed to inhibit the anatase-to-rutile phase transformation in the TiO 2 powders upon high temperature annealing, while crystallization of the amorphous WO 3 was also not observed. Changes in the local bonding within the WO 3 were observed and associated with changes in the structural nature of the film and its interface to the substrate.

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“…A comparison of the XPS C1 spectra of the initial nanotubes and the WC1-x/MWCNT composite (Figure 9a) shows a strong additional low-intensity details M (282.9 eV) and B' (287.5 eV) in the WC1-x/MWCNT spectrum. The energy position of the peak M corresponds to the C1 binding energy in tungsten carbides [80][81][82]. Therefore, its appearance is associated with transitions in carbon atoms of the WC1-x coating layer.…”

Section: Xps Research Of the Nanocomposites And Initial Mwcntsmentioning

confidence: 97%

Studies of Buried Layers and Interfaces of Tungsten Carbide Coatings on the MWCNT Surface by XPS and NEXAFS Spectroscopy

et al. 2020

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Currently, X-ray photoelectron spectroscopy (XPS) is widely used to characterize the nanostructured material surface. The ability to determine the atom distribution and chemical state with depth without the sample destruction is important for studying the internal structure of the coating layer several nanometers thick, and makes XPS the preferable tool for the non-destructive testing of nanostructured systems. In this work, ultra-soft X-ray spectroscopy methods are used to study hidden layers and interfaces of pyrolytic tungsten carbide nanoscale coatings on the multi-walled carbon nanotube (MWCNT) surfaces. XPS measurements were performed using laboratory spectrometers with sample charge compensation, and Near Edge X-ray Absorption Fine Structure (NEXAFS) studies using the Russian–German dipole beamline (RGBL) synchrotron radiation at BESSY-II. The studied samples were tested by scanning and transmission electron microscopy, X-ray diffractometry, Raman scattering and NEXAFS spectroscopy. It was shown that the interface between MWCNT and the pyrolytic coating of tungsten carbide has a three-layer structure: (i) an interface layer consisting of the outer graphene layer carbon atoms, forming bonds with oxygen atoms from the oxides adsorbed on the MWCNT surface, and tungsten atoms from the coating layer; (ii) a non-stoichiometric tungsten carbide WC1-x nanoscale particles layer; (iii) a 3.3 nm thick non-stoichiometric tungsten oxide WO3-x layer on the WC1-x/MWCNT nanocomposite outer surface, formed in air. The tungsten carbide nanosized particle’s adhesion to the nanotube outer surface is ensured by the formation of a chemical bond between the carbon atoms from the MWCNT upper layer and the tungsten atoms from the coating layer.

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High-resolution core-level study of hexagonal WC(0001)

Cited by 47 publications

References 20 publications

Surface and in depth chemistry of polycrystalline WO/sub 3/ thin films studied by X-ray and soft X-ray photoemission spectroscopies

Surface and in depth chemistry of polycrystalline WO/sub 3/ thin films studied by X-ray and soft X-ray photoemission spectroscopies

Tungsten hexacarbonyl and hydrogen peroxide as precursors for the growth of tungsten oxide thin films on titania nanoparticles

Studies of Buried Layers and Interfaces of Tungsten Carbide Coatings on the MWCNT Surface by XPS and NEXAFS Spectroscopy

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