Layer‐dependent resonant Raman scattering of a few layer MoS<sub>2</sub>

Chakraborty, Biswanath; Matte, H. S. S. Ramakrishna; Sood, Anil K.; Rao, C. N. R.

doi:10.1002/jrs.4147

Cited by 429 publications

(417 citation statements)

References 29 publications

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“…The resonance Raman spectra show that multiple modes are shifted from the first-order Raman frequencies, which suggests that the electronic transitions are strongly coupled with phonon modes. There are several reports of this resonant Raman scattering phenomenon in MoS2 [78,79,86,91,93,[98][99][100]. All of these studies are in general agreement on the attribution of the peaks observed in the resonant Raman scattering spectrum, which suggests coupling between vibrational modes and longitudinal acoustic phonon modes.…”

Section: Resonant Raman Scatteringsupporting

confidence: 69%

“…The dispersion of the LA, TA, and ZA modes flatten at the border of the Brillouin zone near the high-symmetry M point. Even though it is hard to observe in bulk MoS2 as shown in Figure 8, this LA (M) mode has been observed in MoS2 nanoparticles [79], MoS2 monolayer [101], few layers [93], and their aqueous suspension [21]. Hence the peak at ~230 cm −1 is related to the structural defect-induced scattering in MoS2 [93].…”

Section: Resonant Raman Scatteringmentioning

confidence: 94%

“…Even though it is hard to observe in bulk MoS2 as shown in Figure 8, this LA (M) mode has been observed in MoS2 nanoparticles [79], MoS2 monolayer [101], few layers [93], and their aqueous suspension [21]. Hence the peak at ~230 cm −1 is related to the structural defect-induced scattering in MoS2 [93]. Lack of this feature may confirm relatively good crystal quality for the natural MoS2 sample [102].…”

Section: Resonant Raman Scatteringmentioning

confidence: 94%

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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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Section: Resonant Raman Scatteringsupporting

confidence: 69%

Section: Resonant Raman Scatteringmentioning

confidence: 94%

Section: Resonant Raman Scatteringmentioning

confidence: 94%

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

et al. 2015

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“…However, in this case the high-frequency peak largely dominates the oX-mode feature for N ≥ 6. These intriguing observations, together with the observation of the iX and oMX bulk modes, and a particularly intense oX-mode feature in monoloayer MoTe 2 at E L = 1.96 eV (see Supporting Information and Ref.[37]) provide a strong impetus for a quantitative analysis of resonant, symmetry-dependent exciton-phonon coupling [10,14,40,46,47] in N -layer MX 2 .Conclusion Using micro-Raman spectroscopy, we have reported a unified description of the optical phonon modes in a N -layer 2H-transition metal dichalcogenide crystal (here, MoTe 2 ), between the bulk (threedimensional) and monolayer (quasi-two-dimensional) limits. The manifolds of low-frequency interlayer shear and breathing modes, and of the mid-frequency modes involving out-of-phase intralayer motion of the chalcogen atoms are well understood using classical theories of coupled oscillators.…”

mentioning

confidence: 97%

“…[37]) provide a strong impetus for a quantitative analysis of resonant, symmetry-dependent exciton-phonon coupling [10,14,40,46,47] in N -layer MX 2 .…”

mentioning

confidence: 99%

Unified Description of the Optical Phonon Modes in N-Layer MoTe₂

et al. 2015

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N -layer transition metal dichalcogenides provide a unique platform to investigate the evolution of the physical properties between the bulk (three dimensional) and monolayer (quasi two-dimensional) limits. Here, using high-resolution micro-Raman spectroscopy, we report a unified experimental description of the Γ-point optical phonons in N -layer 2H-molybdenum ditelluride (MoTe2). We observe a series of N -dependent low-frequency interlayer shear and breathing modes (below 40 cm −1 , denoted LSM and LBM) and well-defined Davydov splittings of the mid-frequency modes (in the range 100 − 200 cm −1 , denoted iX and oX), which solely involve displacements of the chalcogen atoms. In contrast, the high-frequency modes (in the range 200 − 300 cm −1 , denoted iMX and oMX), arising from displacements of both the metal and chalcogen atoms, exhibit considerably reduced splittings. The manifold of phonon modes associated with the in-plane and out-of-plane displacements are quantitatively described by a force constant model, including interactions up to the second nearest neighbor and surface effects as fitting parameters. The splittings for the iX and oX modes observed in N -layer crystals are directly correlated to the corresponding bulk Davydov splittings between the E2u/E1g and B1u/A1g modes, respectively, and provide a measurement of the frequencies of the bulk silent E2u and B1u optical phonon modes. Our analysis could readily be generalized to other layered crystals.Keywords: Two-dimensional materials, layered crystals, transition metal dichalcogenides, MoTe2, Raman spectroscopy, interlayer breathing and shear modes, force constants, Davydov splitting, surface effects.Introduction In the wake of graphene, a vast family of layered materials is attracting tremendous attention [1]. Now available in the form of N -layer crystals, the latter exhibit peculiar physical properties that complement the assets of graphene and offer exciting perspectives to design van der Waals heterostructures [1]. Semiconducting transition metal dichalcogenides (MX 2 , with M = Mo, W and X = S, Se, Te) are among the most actively investigated layered crystals [2]. Indeed, although bulk MX 2 exhibit indirect bandgaps, monolayer MX 2 are direct bandgap semiconductors [3,4] with remarkable spin, valley [5] and optoelectronic properties [6]. More Generally, N -layer MX 2 crystals provide an ideal platform to uncover the impact of symmetry breaking and interlayer interactions on the electronic, optical and vibrational properties, from the bulk (three-dimensional) to the monolayer (quasi two-dimensional) limit.In particular, in N -layer MX 2 , interlayer interactions result in a splitting of all the monolayer phonon modes [7][8][9][10][11][12][13][14][15][16] (see Table I). The latter effect is known as the Davydov splitting [17] and is closely related to the force constants that govern the vibrational properties of MX 2 [9]. The Davydov splitting has been previously studied in polyaromatic molecules [18], thin films [19], and bulk layered crystals, ...

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Atomically Thin MoS₂: A Versatile Nongraphene 2D Material

Subbaiah

Saji

Tiwari

2016

Adv Funct Materials

245

131

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Two-dimensional inorganic materials are emerging as a premiere class of materials for fabricating modern electronic devices. The interest in 2D layered transition metal dichalcogenides is especially high. Particularly, 2D MoS 2 is being heavily researched due to its novel functionalities and its suitability for a wide range of electronic and optoelectronic applications. In this article, the progress in mono/few layer(s) MoS 2 research is reviewed by focusing primarily on the layer dependent evolution of crystal, phonon, and electronic structure. The review includes extensive detail into the methodologies adapted for single or few layer(s) MoS 2 growth. Further, the review covers the versatility of 2D MoS 2 for a broad range of device applications. Recent advancements in the fi eld of van der Waals heterostructures are also highlighted at the end of the review. Unlike zero-band gap graphene (semimetal), [ 8 ] and large band gap hBN (insulator), [ 9 ] the 2D transition metal dichalcogenides (sulfi des and selenides) have band gaps comparable to conventional Si or GaAs, and thus present a tantalizing prospect of scaling all semiconductor science and technology down to a truly atomic scale. Although these transition metal dichalcogenides (TMDCs) are quite well known for the past few decades for their applications in solid state lubricants, [ 10 ] photovoltaic devices, [ 11,12 ] and rechargeable batteries, [ 13 ] the recent methodologies and concepts evolved from graphene research like exfoliation, transfer, and manipulation of 2D materials have driven interest toward the exploration of layered TMDCs. TMDCs possess hexagonal layers of transition metal atoms (M) sandwiched between two layers of chalcogen atoms (X) with an MX 2 stoichiometry. Depending on the different combinations of chalcogen (typically S, Se, or Te) and transition metal (mainly Mo and W) elements, several different kinds of TMDCs are possible. Among the various combinations of TMDCs, MoS 2 is the most promising 2D material as its elemental constituents are abundant, nontoxic, and amenable for easy mono/few layer(s) synthesis when compared to their analogous selenides and tellurides. DOIDespite graphene's exceptionally high carrier mobility, [ 14 ] fi eld-effect transistors (FETs) made from graphene cannot effectively function as electronic switches due to the absence of an electronic band gap. [ 15,16 ] 2D MoS 2 possesses a relatively high mobility up to 200 cm 2 (V-s) −1 with a high on/off current ratio of ≈10 8 at room temperature, [17][18][19][20] and has a layer dependent band gap with a crossover from indirect (1.2 eV) to direct (1.9 eV) at the bulk to monolayer transition, making this a promising material for effi cient electronic, [ 17,21 ] and optoelectronic devices. [22][23][24] The unique electronic band structure and optical properties of monolayer MoS 2 are suitable for a wide range of novel functional devices and hence has triggered exhaustive research on this nongraphene material during the last few years. [ 2,7,[25][26][27][28][29][30]...

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Layer‐dependent resonant Raman scattering of a few layer MoS₂

Cited by 429 publications

References 29 publications

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

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

Unified Description of the Optical Phonon Modes in N-Layer MoTe₂

Atomically Thin MoS₂: A Versatile Nongraphene 2D Material

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Layer‐dependent resonant Raman scattering of a few layer MoS2

Cited by 429 publications

References 29 publications

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

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

Unified Description of the Optical Phonon Modes in N-Layer MoTe2

Atomically Thin MoS2: A Versatile Nongraphene 2D Material

Contact Info

Product

Resources

About

Layer‐dependent resonant Raman scattering of a few layer MoS₂

Unified Description of the Optical Phonon Modes in N-Layer MoTe₂

Atomically Thin MoS₂: A Versatile Nongraphene 2D Material