Surface-phonon dispersion of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MoS</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Bertrand, P. A.

doi:10.1103/physrevb.44.5745

Cited by 138 publications

(76 citation statements)

References 9 publications

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“…The in-plane E 1 2g peak results from opposite vibration of two S atoms with respect to the Mo atom while the A 1g peak is associated with the out-of-plane vibration of only S atoms in opposite directions. 53,54 The intensity of A 1g peak arises from the resonance Raman (RR) scattering, because the incident laser is in resonance with the direct bandgap (~1.96 eV) at the K point. The asymmetric 2LA(M) peak is associated with second-order zoneedge phonon (LA(M)) and a first order optical phonon peak (A 2u ).…”

Section: Resultsmentioning

confidence: 99%

MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

2014

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We study the synthesis, electrochemical and mechanical performance of layered freestanding papers composed of acid exfoliated few layer molybdenum disulfide (MoS 2 ) and reduced graphene oxide (rGO) flakes for use as a self-standing flexible electrode in sodium ion batteries. Synthesis was achieved through vacuum filtration of homogenous dispersions consisting of varying wt. % of acid treated MoS 2 flakes in GO in DI water, followed by thermal reduction at elevated temperatures. The electrochemical performance of the crumpled composite paper (at 4 mg.cm -2 ) was evaluated as counter electrode against pure Na foil in a half-cell configuration. The electrode showed good Na cycling ability with a stable charge capacity of approx.230 mAh.g -1 with respect to total weight of the electrode with coulombic efficiency reaching approx. 99 %. In addition, static uniaxial tensile tests performed on crumpled composite papers showed high average strain to failure reaching approx. %.KEYWORDS: TMDC, sodium battery, freestanding electrode, graphene, MoS 2 2 Lithium ion batteries (LIBs) have been extensively studied for energy-storage applications like portable electronic devices and electric vehicles. [1][2][3] However, concerns over the cost, safety and availability of Li reserves 4 for large-scale applications involving renewable energy integration and the electrical grid have to be answered. In this regard, sodium ion batteries (SIBs) have drawn increasing attention because in contrast to lithium, 5-7 sodium resources are practically inexhaustible and evenly distributed around the world while the ion insertion chemistry is largely identical to that of lithium. Also, from electrochemical point of view, sodium has a very negative redox potential (-2.71 V, vs. SHE) and a small electrochemical equivalent (0.86 gAh -1 ), which make it the most advantageous element for battery applications after lithium. However, many challenges remain before SIBs can become commercially competitive with LIBs. For instance, Na ions are about 55% larger in radius than Li-ions, which makes it difficult to find a suitable host material to allow reversible and rapid ion insertion and extraction. 8 To this end, researchers have proposed a number of high-capacity sodium host materials (negative electrode) involving either carbon or group IVA and VA elements that form intermetallic compounds with Na. [9][10][11][12][13] The alloying compounds demonstrate high first cycle Na-storage capacities, such as Na 15 Sn 4 (847 mAhg -1 ), Na 15 Pb 4 (485 mAhg -1 ), Na 3 Sb (600 mAhg -1 ) and Na 3 P (2560 mAhg -1 ), respectively. However, this comes at the cost of very high volume change upon Na-insertion (as much as 500 % in some cases), resulting in formation of internal cracks, loss of electrical contact, and eventual failure of the electrode (particularly for thick electrodes). 14 Novel nanostructured designs that can accommodate large volumetric strains need further exploration. [15][16][17][18] For carbon-based electrode materials, much of the emphasis ...

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Section: Resultsmentioning

confidence: 99%

MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

2014

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“…This is consistent with surface phenomenon measurements investigated by P. A. Bertrand, who reported the surface phonon dispersion of MoS2 as measured by high resolution electron-energy-loss spectroscopy (HREELS). It was found that the peak energy of the A1g optical mode for thin layers is 3.1(±0.2) meV lower than the related bulk phonon [92]. In fact, the red shift of the E2g 1 peak with the increase in layer thickness is due to the fact that thinner…”

Section: Lattice Dynamic: Raman Scattering and Ir Absorptionmentioning

confidence: 87%

Recent Advancement on the Optical Properties of Two-Dimensional Molybdenum Disulfide (MoS2) Thin Films

et al. 2015

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Abstract:The emergence of two-dimensional (2D) materials has led to tremendous interest in the study of graphene and a series of mono-and few-layered transition metal dichalcogenides (TMDCs). Among these TMDCs, the study of molybdenum disulfide (MoS2) has gained increasing attention due to its promising optical, electronic, and optoelectronic properties. Of particular interest is the indirect to direct band-gap transition from bulk and few-layered structures to mono-layered MoS2, respectively. In this review, the study of these properties is summarized. The use of Raman and Photoluminescence (PL) spectroscopy of MoS2 has become a reliable technique for differentiating the number of molecular layers in 2D MoS2.

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“…Earlier studies of bulk MoS 2 using Raman and infrared spectroscopy [53,54] as well as Neutron scattering [55] and electron-energy-loss spectroscopy [56] had already well characterized the phonons at Γ and the phonon dispersion. In the recent years, a large number of Raman studies on mono-and few-layer systems has emerged [57,58,59,60,61,62,63,64,65].…”

Section: Introductionmentioning

confidence: 99%

Vibrational and optical properties of MoS2: From monolayer to bulk

Molina-Sánchez

Hummer

Wirtz

2015

Surface Science Reports

206

167

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Molybdenum disulfide, MoS 2 , has recently gained considerable attention as a layered material where neighboring layers are only weakly interacting and can easily slide against each other. Therefore, mechanical exfoliation allows the fabrication of single and multi-layers and opens the possibility to generate atomically thin crystals with outstanding properties. In contrast to graphene, it has an optical gap of 1.9 eV. This makes it a prominent candidate for transistor and opto-electronic applications. Single-layer MoS 2 exhibits remarkably different physical properties compared to bulk MoS 2 due to the absence of interlayer hybridization. For instance, while the band gap of bulk and multi-layer MoS 2 is indirect, it becomes direct with decreasing number of layers. In this review, we analyze from a theoretical point of view the electronic, optical, and vibrational properties of single-layer, few-layer and bulk MoS 2 . In particular, we focus on the effects of spinorbit interaction, number of layers, and applied tensile strain on the vibrational and optical properties. We examine the results obtained by different methodologies, mainly ab initio approaches. We also discuss which approximations are suitable for MoS 2 and layered materials. The effect of external strain on the band gap of single-layer MoS 2 and the crossover from indirect to direct band gap is investigated. We analyze the excitonic effects on the absorption spectra. The main features, such as the double peak at the absorption threshold and the high-energy exciton are presented. Furthermore, we report on the phonon dispersion relations of single-layer, few-layer and bulk MoS 2 . Based on the latter, we explain the behavior of the Raman-active A 1g and E 1 2g modes as a function of the number of layers. Finally, we compare theoretical and experimental results of Raman, photoluminescence, and optical-absorption spectroscopy.

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Surface-phonon dispersion ofMoS2

Cited by 138 publications

References 9 publications

MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

Recent Advancement on the Optical Properties of Two-Dimensional Molybdenum Disulfide (MoS2) Thin Films

Vibrational and optical properties of MoS2: From monolayer to bulk

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Surface-phonon dispersion ofMoS2

Cited by 138 publications

References 9 publications

MoS2/Graphene Composite Paper for Sodium-Ion Battery Electrodes

MoS2/Graphene Composite Paper for Sodium-Ion Battery Electrodes

Recent Advancement on the Optical Properties of Two-Dimensional Molybdenum Disulfide (MoS2) Thin Films

Vibrational and optical properties of MoS2: From monolayer to bulk

Contact Info

Product

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MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes