Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS<sub>2</sub> probed by Raman scattering

Kumar, Deepu; Singh, Birender; Kumar, Pawan; Viswanath, B.; Kumar, Pradeep

doi:10.1088/1361-648x/ab3fec

Cited by 24 publications

(24 citation statements)

References 45 publications

(110 reference statements)

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“…To understand the temperature evaluation of the phonon self-energy parameters such as frequency behavior. Similar anomalies in the linewidth are also reported for different families of TMDCs [48][49] attributed to the mismatch between expansions coefficients of the underlying substrate. is the change in frequency due to anharmonic effect at finite 14 temperature.…”

Section: Temperature Dependence Of the Phonon Modessupporting

confidence: 79%

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂

et al. 2021

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We present comprehensive temperature dependent Raman measurements for chemical vapor deposition grown horizontally aligned layered MoS2 in a temperature range of 4–330 K under a resonance condition. Our analysis of temperature dependent phonon frequency shift and linewidth suggests a finite role of three and four phonon anharmonic effect. We observe Davydov splitting of the out-of-plane (A 1g ) and in-plane ( E 2 g 1 ) modes for both three layer (3L) and few layer (FL) systems. The number of Davydov splitting components are found more in FL compared to 3L MoS2, which suggests that it increases with an increasing number of layers. Further, Davydov splitting is analyzed as a function of temperature. Temperature evaluation of the Raman spectra shows that the Davydov splitting, especially for A 1g mode, is very strong and well resolved at low temperature. We observe that A 1g mode shows the splitting at low temperature, while E 2 g 1 mode is split even at room temperature, which suggests a prominent role of A 1g mode in the interlayer interaction at low temperature. Further, an almost 60-fold increase in the intensity of the phonon modes at low temperature clearly shows the temperature dependent tuning of the resonance effect.

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Section: Temperature Dependence Of the Phonon Modessupporting

confidence: 79%

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂

et al. 2021

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“…The induced strain due to TEC mismatch may affect the weak van der walls forces, leading to the slippage, realignment or change in surface morphology of MoSe2 films on the substrate and forming of wrinkles or ripples into the system, which may affect the frequency of the modes. Similar anomalies are also observed in the case of other MX2 systems[38,40]. For bilayer, we observed a decrease in the mode frequency (seeFig 4(b) and Fig 5 (b)) below ~ 100 K.…”

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confidence: 87%

Electron-phonon coupling, thermal expansion coefficient, resonance effect, and phonon dynamics in high-quality CVD-grown monolayer and bilayer MoSe2

Kumar

et al. 2022

Phys. Rev. B

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Probing phonons, quasi-particle excitations and their coupling has enriched our understanding of these 2D materials and proved to be crucial for developing their potential applications. Here, we report comprehensive temperature, 4-330 K, and polarization-dependent Raman measurements on mono and bilayer MoSe2. Phonon's modes up to fourth-order are observed including forbidden Raman and IR modes, understood considering Fröhlich mechanism of exciton-phonon coupling.Most notably, anomalous variations in the phonon linewidths with temperature pointed at the significant role of electron-phonon coupling in these systems, especially for the out-of-plane ( 1g A ) and shear mode ( 2 2 g E ), which is found to be more prominent in the narrow-gaped bilayer than the large gapped monolayer. Via polarization-dependent measurements, we deciphered the ambiguity in symmetry assignments, especially to the peaks around ~ 170 cm -1 and ~ 350 cm -1 .Temperature-dependent thermal expansion coefficient, an important parameter for the device performance, is carefully extracted for both mono and bilayer by monitoring the temperaturedependence of the real-part of the phonon self-energy parameter. Our temperature-dependent indepth Raman studies provide a pave for uncovering the deeper role of phonons in these 2D layered materials from a fundamental as well as application point of view.

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“…The change in the phonon mode frequency considering the above effect may be given as ( ) ( ) ( )  is mode frequency at T = 0 K and c is a constant. To extract the thermal expansion coefficient above 60 K, we have fitted the mode frequency using the following equation [10][11][12]:…”

Section: Resultsmentioning

confidence: 99%

Anomalous phonon renormalization in single crystal of silicon

Himanshi¹,

Singh²,

Kumar³

2020

Dae Solid State Physics Symposium 2019

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The temperature dependence of the first-order phonon mode of single crystal of Silicon (Si) is determined by Raman scattering in a broad temperature range of 4-623 K. Our studies reveal the anomalous red-shift of the Raman active phonon mode at temperature (~ 50 K) attributed to the anomalous expansion of Si in the low temperature region. Silicon shows negative thermal expansion below 120 K, however, odd behaviour is also observed at very low temperatures i.e., softening of the Si crystal is detected below 40 K. This peculiar behaviour of Si is described by the anomalous phonon anharmonicity observed at low temperature.

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Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS₂ probed by Raman scattering

Cited by 24 publications

References 45 publications

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂

Electron-phonon coupling, thermal expansion coefficient, resonance effect, and phonon dynamics in high-quality CVD-grown monolayer and bilayer MoSe2

Anomalous phonon renormalization in single crystal of silicon

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Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS2 probed by Raman scattering

Cited by 24 publications

References 45 publications

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS2

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS2

Electron-phonon coupling, thermal expansion coefficient, resonance effect, and phonon dynamics in high-quality CVD-grown monolayer and bilayer MoSe2

Anomalous phonon renormalization in single crystal of silicon

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Product

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Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS₂ probed by Raman scattering

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂

Davydov Splitting, Resonance Effect and Phonon Dynamics in Chemical Vapor Deposition Grown Layered MoS₂