Studies of lattice dynamics in 2HTaS2 by Raman scattering

Sugai, S.; Murase, K.; Uchida, S.; Tanaka, Satoru

doi:10.1016/0038-1098(81)90847-4

Cited by 50 publications

(46 citation statements)

References 19 publications

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“…The liquid‐phase exfoliated 2H‐MoS 2 shows characteristic Raman shifts at 382, 408, and 454 cm −1 corresponding to the in plane E 2g 1 , out‐of‐plane A 1g , and longitudinal acoustic phonon modes, respectively. Characteristic Raman shifts at 196 cm −1 (E 1g ), 288 cm −1 (E 2g 1 ), and 404 cm −1 (A 1g ) were observed for 2H‐TaS 2 . Similarly, three distinctive Raman active vibrational modes were expected at 243 cm −1 (E 1g ), 303 cm −1 (E 2g 1 ), and 383 cm −1 (A 1g ) for 1T‐TaS 2 .…”

Section: Resultsmentioning

confidence: 73%

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Exfoliated 2D Transition Metal Disulfides for Enhanced Electrocatalysis of Oxygen Evolution Reaction in Acidic Medium

Liu

Chatterjee

et al. 2016

Adv Materials Inter

152

121

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The scarcity of inexpensive and efficient electrocatalyst for acid water oxidation to molecular oxygen presents the development of nonprecious catalysts for water oxidation a scientific priority. For water splitting, transition‐metal dichalcogenides have attracted great interest as advanced catalysts for hydrogen evolution reaction, but there has been no sincere attention to generate significant anodic current density of oxygen evolution reaction (OER) with these materials. Addressing this unmet need, here, the outstanding catalytic performance of MoS2 and TaS2 in OER is demonstrated. Chemically exfoliated 2D thin sheets of MoS2 and TaS2, in both of their 1T and 2H polymorph, have been employed for OER catalysis in acid medium. The best performance for oxygen evolution, which is also comparable to benchmark IrO2, comes out from 1T‐MoS2 followed by 1T‐TaS2, 2H‐MoS2, and 2H‐TaS2. Theoretical study reveals that the dominant catalytic activity is on edge sites instead of surface and corroborates the experimental results of polymorphic dependence of electrocatalytic activity. The materials have also shown moderate durability in the harsh acidic medium. The study brings up new set of electrocatalyst for oxygen evolution in acid regime that hitherto has remained largely unrevealed.

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Section: Resultsmentioning

confidence: 73%

“…Similarly, three distinctive Raman active vibrational modes were expected at 243 cm −1 (E 1g ), 303 cm −1 (E 2g 1 ), and 383 cm −1 (A 1g ) for 1T‐TaS 2 . In addition to that, a two‐phonon mode was shown at 124 cm −1 for 1T‐TaS 2 …”

Section: Resultsmentioning

confidence: 99%

Exfoliated 2D Transition Metal Disulfides for Enhanced Electrocatalysis of Oxygen Evolution Reaction in Acidic Medium

Liu

Chatterjee

et al. 2016

Adv Materials Inter

152

121

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“…Band calculations were made by the APW [64] and the layer method [145]. Experiments were performed on electric resistivity [l, 124, 146 to 1481, Shubnikov-de Haas effect [148], magnetic susceptibility [124], specific heat [144, 1491, Raman scattering [15], and so on. shows the temperature dependence of the phonon energy.…”

Section: Zh-tasementioning

confidence: 99%

Lattice Vibrations in the Charge‐Density‐Wave States of Layered Transition Metal Dichalcogenides

Sugai

1985

Physica Status Solidi (b)

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“…This suggests that an additional electronic or structural ordering in MoS 2 at low temperatures and high pressures. It is common for TMDs with both major structural types 2H and 1T to demonstrate CDW phenomena, which lower the symmetry of their quasi-2D structures [24][25][26][27][28]. It has been noticed that the presence of CDW indicates the proximity of superconducting state emerging at lower temperatures.…”

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Nontrivial metallic state of MoS2

Cao

Goncharov

et al. 2018

Phys. Rev. B

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The electrical conductivity and Raman spectroscopy measurements have been performed on MoS2 at high pressures up to 90 GPa and variable temperatures down to 5 K. We find that the temperature dependence of the resistance in a metallic 2H a phase has an anomaly (a hump) which shifts with pressure to higher temperature. Concomitantly, a new Raman phonon mode appears in the metallic state suggesting that the electrical resistance anomaly may be related to a structural transformation. We suggest that this anomalous behavior is due to a charge density wave state, the presence of which is indicative for a possibility for an emergence of superconductivity at higher pressures. PACS numbers: 73.90.+f, 71.30.+h, 71.45.Lr Two-dimensional (2D) materials are characterized by a strong anisotropy of the intra-versus inter-layer bonding. This remarkable difference brings up unique notions such as 2D materials which can be exploited for practical applications [1]. One of the most exposed materials of such a kind is graphene [1,2], which also brought the interests to inorganic materials with unique electronic [3], optical [4] attributes and high mobility [5]. However, graphene is a gapless (semimetallic) material which restricts its possible applications. In contrast, the transition-metal dichalcogenides (TMDs), quasi-2D material with distinct structures and unique physical properties [6-10], possess a non-zero band gap that could also be tuned. Therefore, TMDs are currently attracted enormous research interests. MoS 2 is one of the most extensively investigated member of TMDs, and it can be prepared as a 2D material via mechanical exfoliation [4,11]. By varying the number of layers, MoS 2 can be transformed from an indirect band-gap semiconductor to a direct band-gap semiconductor [11]. Monolayer MoS 2 has mechanical properties almost as good as graphene, but unlike graphene, possesses a direct bandgap. Thus, MoS 2 shows an excellent potential to replace graphene in the next generation nanoelectronics applications [12][13][14][15][16]. Furthermore, doping of 2D MoS 2 has been shown to change the electronic and structural properties dramatically that results to metallization, formation of the charge density wave (CDW) [17] and eventually superconducting states [18,19]. Similar structural effects related to 2H to 1T transition (from trigonal to octahedral TM coordination) have been found in other doped TMDs (MoTe 2 ), confirmed by Raman spectroscopy measurements [20] including the case when 1T phase has been stabilized by pressure and superconductivity appears accordingly [21].The application of external pressure is an alternative (to doping) way to tune the electronic as well as crystal structure. MoS 2 transforms from 2H c to 2H a phase (through a sliding of the layers) above 20 GPa along with a metallization [22,23]. However, the resistivity measurements show that the temperature dependence of the resistivity is not monotonous in both semiconducting and metallic regimes revealing a pressure dependent hump in the resistivity−te...

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Studies of lattice dynamics in 2HTaS2 by Raman scattering

Cited by 50 publications

References 19 publications

Exfoliated 2D Transition Metal Disulfides for Enhanced Electrocatalysis of Oxygen Evolution Reaction in Acidic Medium

Exfoliated 2D Transition Metal Disulfides for Enhanced Electrocatalysis of Oxygen Evolution Reaction in Acidic Medium

Lattice Vibrations in the Charge‐Density‐Wave States of Layered Transition Metal Dichalcogenides

Nontrivial metallic state of MoS2

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