Raman scattering and high resolution electron microscopy studies of metal-organic chemical vapor deposition-tungsten disulfide thin films

Chung, Jin Woo; Adib, A.; Dai, Z. R.; Adib, Kourosh; Ohuchi, Fumio S.

doi:10.1016/s0040-6090(98)00954-7

Cited by 19 publications

(12 citation statements)

References 17 publications

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“…The downward shift was attributed to weaker metal sulfur bonds caused by the low stacking degree in the catalysts and the concomitant weak van der Waals forces, which allow atom displacement . The asymmetry of the bands of A 1g and E 1 2g modes was concluded to be caused by highly bent slabs, which influenced the symmetry selection rules leading to a second‐order Raman signal, which overlapped with A 1g and E 1 2g bands …”

Section: Resultsmentioning

confidence: 99%

“…[28] The asymmetry of the bands of A 1g and E 1 2g modesw as concludedt ob ec aused by highly bent slabs, which influenced the symmetry selection rules leading to as econd-order Raman signal, which overlappedw ith A 1g and E 1 2g bands. [29] The spectrum of NiMoWS( Figure2(e)) appears to be ac ombination of the spectra of the bimetallic catalysts. The band at 410 cm À1 is assigned to the A 1g mode of Mo-W composite species.…”

Section: Composition and Crystallinitymentioning

confidence: 95%

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Distribution of Metal Cations in Ni‐Mo‐W Sulfide Catalysts

et al. 2015

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The distribution of metal cations and the morphology of unsupported NiMo, NiW, and NiMoW sulfide catalysts were explored qualitatively and quantitatively. In the bi‐ and trimetallic catalysts, Mo(W)S2 nanoparticles are deposited on Ni sulfide particles of varying stoichiometry and sizes (crystalline Ni9S8, and Ni3S4 were identified). These nanoparticles are stacks of Mo(W)S2 slabs with varying size, degrees of bending and mismatch between the slabs. High resolution electron microscopy and X‐ray absorption spectroscopy based on particle modeling revealed a statistical distribution of Mo and W within individual layers in sulfide NiMoW, forming intralayer mixed Mo1−xWxS2. Ni is associated with MoS2, WS2, and Mo1−xWxS2 creating Ni‐promoted phases. The incorporation of Ni at the edges of the slabs was the highest for sulfide NiMoW. This high concentration of Ni in sulfide NiMoW, as well as its long bent Mo1−xWxS2 slabs, were paralleled by the highest activity for nitrogen and sulfur removal from model hydrocarbons such as o‐propylaniline and dibenzothiophene.

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Section: Resultsmentioning

confidence: 99%

Section: Composition and Crystallinitymentioning

confidence: 95%

Distribution of Metal Cations in Ni‐Mo‐W Sulfide Catalysts

et al. 2015

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“…The in-phase and outof-phase vibrational pattern of the A 1g /B 1u pair in bulk WS 2 finds its counterpart in the variety of in-and outof-phase vibrations observed in FL-WS 2 . In WS 2 nanomaterials, the B 1u mode gains in Raman intensity and its evolvement can be followed in WS 2 nanomaterials under pressure [29,36], in different layer orientation in thin films [37] and in different diameter WS 2 nanotubes [29,38]. In these cases, a strong resonance behavior is observed as well, much like in FL-WS 2 : the modes not allowed in a first-order Raman process appear most strongly when the excitation energy is in or close to resonance with the optical transitions.…”

Section: Discussionmentioning

confidence: 99%

Splitting of monolayer out-of-planeA1′Raman mode in few-layerWS2

et al. 2015

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We present Raman measurements of mono-and few-layer WS2. We study the monolayer A 1 mode around 420 cm −1 and its evolution with the number of layers. We show that with increasing layer number there is an increasing number of possible vibrational patterns for the out-of-plane Raman mode: in N -layer WS2 there are N Γ-point phonons evolving from the A 1 monolayer mode. For an excitation energy close to resonance with the A excitonic transition energy, we were able to observe all of these N components, irrespective of their Raman activity. Density functional theory calculations support the experimental findings and make it possible to attribute the modes to their respective symmetries. The findings described here are of general importance for all other phonon modes in WS2 and other layered transition metal dichalcogenide systems in the few layer regime.

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“…The as-deposited coating only exhibited a very small peak at ~326 cm -1 attributed to WO 3 bending vibrations and a large broad peak at 660-1100 cm -1 related to stretching vibrations of WO 3 (717 and 807 cm -1 ) [28]. Raman spectra of the wear track and the transfer film showed peaks representing wellordered tungsten disulfide (including second-order peak at ~535 cm -1 ) [29], which are absent in the as-deposited spectrum (Fig. 6).…”

Section: Analysis Of the Worn Surfacesmentioning

confidence: 99%

Ultra-low friction W–S–N solid lubricant coating

Gustavsson

Jacobson

Cavaleiro

et al. 2013

Surface and Coatings Technology

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W-S-N films were deposited by reactive magnetron sputtering from WS2 target in Ar/N2 atmosphere. Besides the standard evaluation of composition, structure, morphology, hardness and cohesion/adhesion, the core objective of this paper was to analyze coating tribological behavior. The chemical composition was 34 at.% N, 12 at.% O, 29 at.% W and 25 at.% S and the as-deposited films were completely amorphous. The film thickness was 2.3 µm including the approximately 300 nm thick adhesion improving titanium interlayer. The friction coefficient was lower than 0.003 when sliding in dry nitrogen. The coating showed remarkable wear resistance surviving more than 2 million laps on pin-on-dics. The excellent friction properties were attributed to the formation of a thin tungsten disulfide tribofilm on the top of the wear track of the coating and on the counterpart surface. Moreover, the coating showed ability to replenish damaged areas with solid lubricant. We demonstrated that a

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Raman scattering and high resolution electron microscopy studies of metal-organic chemical vapor deposition-tungsten disulfide thin films

Cited by 19 publications

References 17 publications

Distribution of Metal Cations in Ni‐Mo‐W Sulfide Catalysts

Distribution of Metal Cations in Ni‐Mo‐W Sulfide Catalysts

Splitting of monolayer out-of-planeA1′Raman mode in few-layerWS2

Ultra-low friction W–S–N solid lubricant coating

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