Temperature dependence of the double-resonance Raman bands in bilayer WSe2

Santos, E.P. dos; Silva, Fabio L.R.; Gontijo, Rafael N.; Alves, Juliana M.; Ammar, Mohamed‐Ramzi; Fantini, C.

doi:10.1016/j.vibspec.2020.103117

Cited by 9 publications

(7 citation statements)

References 44 publications

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“…With increasing temperature, Raman features for iB, monolayer and 30°tB WSe 2 shift towards lower frequency together with a broadening of the FWHM, which is in good agreement with what was reported in Refs. [49,50]. The most interesting observation in Fig.…”

Section: Twisted Homo-bilayersmentioning

confidence: 76%

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Pan,

Li,

Rahaman

et al. 2022

Preprint

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Twisted 2D bilayer materials are created by artificial stacking of two monolayer crystal networks of 2D materials with a desired twisting angle θ. The material forms a moiré superlattice due to the periodicity of both top and bottom layer crystal structure. The optical properties are modified by lattice reconstruction and phonon renormalization, which makes optical spectroscopy an ideal characterization tool to study novel physics phenomena. Here, we report a Raman investigation on a full period of the twisted bilayer (tB) WSe2 moiré superlattice (i.e. 0°≤ θ ≤ 60°). We observe that the intensity ratio of two Raman peaks, B2g and E2g/A1g correlates with the evolution of moiré period. The Raman intensity ratio as a function of twisting angle follows an exponential profile matching the moiré period with two local maxima at 0°and 60°and a minimum at 30°. Using a series of temperature-dependent Raman and photoluminescence (PL) measurements as well as ab initio calculations, the intensity ratio IB 2g /I E 2g /A 1g is explained as a signature of lattice dynamics in tB WSe2 moiré superlattices. By further exploring different material combinations of twisted hetero-bilayers, the results are extended for all kinds of Mo-and W-based TMDCs.

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Section: Twisted Homo-bilayersmentioning

confidence: 76%

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Pan,

Li,

Rahaman

et al. 2022

Preprint

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“…28,103−107 In B-WSe 2 , the spectra show a split for the E 1 2g and A 1g modes due to a red (blue) shift in the E 1 2g (A 1g ) mode with increasing N. 104−106 The broad peak ∼260 cm −1 can be deconvolved into 2LA(M) and A(M) bands. 105,107 The 2LA(M) mode ∼262 cm −1 corresponds to the overtone of the LA phonon branch at the M point of the Brillouin zone (BZ), 105,107 whereas the A(M) mode ∼258 cm −1 corresponds to the A-symmetry optical branch at the M point of the BZ. 105,107 The E(M) mode ∼242 cm −1 creates an asymmetry in the lower energy shoulder of E 1 2g +A 1g .…”

Section: Resultsmentioning

confidence: 99%

“…105,107 The 2LA(M) mode ∼262 cm −1 corresponds to the overtone of the LA phonon branch at the M point of the Brillouin zone (BZ), 105,107 whereas the A(M) mode ∼258 cm −1 corresponds to the A-symmetry optical branch at the M point of the BZ. 105,107 The E(M) mode ∼242 cm −1 creates an asymmetry in the lower energy shoulder of E 1 2g +A 1g . 105,107 This mode red shifts with increasing N. 104−106 Figure 2a is an AFM image of the 1L−ML-WSe 2 LMJ.…”

Section: Resultsmentioning

confidence: 99%

“…105,107 The E(M) mode ∼242 cm −1 creates an asymmetry in the lower energy shoulder of E 1 2g +A 1g . 105,107 This mode red shifts with increasing N. 104−106 Figure 2a is an AFM image of the 1L−ML-WSe 2 LMJ. The line profiles taken in two different parts of the LMJ (Figures.…”

Section: Resultsmentioning

confidence: 99%

“…Figure c plots the high-frequency (200–300 cm –1 ) Raman spectra. For 1L-WSe 2 , a single peak is observed ∼250 cm –1 , associated with the two degenerate, first-order A and E Raman modes. ,− In B-WSe 2 , the spectra show a split for the E 1 2g and A 1g modes due to a red (blue) shift in the E 1 2g (A 1g ) mode with increasing N . − The broad peak ∼260 cm –1 can be deconvolved into 2LA(M) and A(M) bands. , The 2LA(M) mode ∼262 cm –1 corresponds to the overtone of the LA phonon branch at the M point of the Brillouin zone (BZ), , whereas the A(M) mode ∼258 cm –1 corresponds to the A-symmetry optical branch at the M point of the BZ. , The E(M) mode ∼242 cm –1 creates an asymmetry in the lower energy shoulder of E 1 2g +A 1g . , This mode red shifts with increasing N . − …”

Section: Resultsmentioning

confidence: 99%

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Ultrafast Charge Transfer and Recombination Dynamics in Monolayer–Multilayer WSe₂ Junctions Revealed by Time-Resolved Photoemission Electron Microscopy

Xu,

Barden,

Alexeev

et al. 2024

ACS Nano

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The ultrafast carrier dynamics of junctions between two chemically identical, but electronically distinct, transition metal dichalcogenides (TMDs) remains largely unknown. Here, we employ time-resolved photoemission electron microscopy (TR-PEEM) to probe the ultrafast carrier dynamics of a monolayer-to-multilayer (1L-ML) WSe 2 junction. The TR-PEEM signals recorded for the individual components of the junction reveal the sub-ps carrier cooling dynamics of 1L-and 7L-WSe 2 , as well as few-ps exciton−exciton annihilation occurring on 1L-WSe 2 . We observe ultrafast interfacial hole (h) transfer from 1L-to 7L-WSe 2 on an ∼0.2 ps time scale. The resultant excess h density in 7L-WSe 2 decays by carrier recombination across the junction interface on an ∼100 ps time scale. Reminiscent of the behavior at a depletion region, the TR-PEEM image reveals the h density accumulation on the 7L-WSe 2 interface, with a decay length ∼0.60 ± 0.17 μm. These charge transfer and recombination dynamics are in agreement with ab initio quantum dynamics. The computed orbital densities reveal that charge transfer occurs from the basal plane, which extends over both 1L and ML regions, to the upper plane localized on the ML region. This mode of charge transfer is distinctive to chemically homogeneous junctions of layered materials and constitutes an additional carrier deactivation pathway that should be considered in studies of 1L-TMDs found alongside their ML, a common occurrence in exfoliated samples.

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Twist Angle-Dependent Phonon Hybridization in WSe₂/WSe₂ Homobilayer

Bera,

Solanki,

Mandal

et al. 2024

ACS Nano

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The emerging moirésuperstructure of twisted transition metal dichalcogenides (TMDs) leads to various correlated electronic and optical properties compared to those of twisted bilayer graphene. In such a versatile architecture, phonons can also be renormalized and evolve due to atomic reconstruction, which, in turn, depends on the twist angle. However, observing this reconstruction and its relationship to phonon behavior with conventional, costeffective imaging methods remains challenging. Here, we used noninvasive Raman spectroscopy on twisted WSe 2 /WSe 2 (t-WSe 2 ) homobilayers to examine the evolution of phonon modes due to interlayer coupling and atomic reconstruction. Unlike in the natural bilayer (NB), ∼0°as well as ∼60°t-WSe 2 samples, the nearly degenerate A 1g /E 2g mode in the twisted samples (1−7°) split into a doublet in addition to the nondegenerate B 2g mode, and the maximum splitting is observed around 2−3°. Our detailed theoretical calculations qualitatively capture the splitting and its dependence as a function of the twist angle and highlight the role of the moirépotential in phonon hybridization. Additionally, we found that around the 2°twist angle, the anharmonic phonon−phonon interaction is higher than the natural bilayer and decreases for larger twist angles. Interestingly, we observed anomalous Raman frequency softening and line-width increase with the decreasing temperature below 50 K, pointing to the combined effect of enhanced electron−phonon coupling and cubic anharmonic interactions in moirésuperlattice.

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Temperature dependence of the double-resonance Raman bands in bilayer WSe2

Cited by 9 publications

References 44 publications

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Ultrafast Charge Transfer and Recombination Dynamics in Monolayer–Multilayer WSe₂ Junctions Revealed by Time-Resolved Photoemission Electron Microscopy

Twist Angle-Dependent Phonon Hybridization in WSe₂/WSe₂ Homobilayer

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Temperature dependence of the double-resonance Raman bands in bilayer WSe2

Cited by 9 publications

References 44 publications

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Signature of lattice dynamics in twisted 2D homo/hetero-bilayers

Ultrafast Charge Transfer and Recombination Dynamics in Monolayer–Multilayer WSe2 Junctions Revealed by Time-Resolved Photoemission Electron Microscopy

Twist Angle-Dependent Phonon Hybridization in WSe2/WSe2 Homobilayer

Contact Info

Product

Resources

About

Ultrafast Charge Transfer and Recombination Dynamics in Monolayer–Multilayer WSe₂ Junctions Revealed by Time-Resolved Photoemission Electron Microscopy

Twist Angle-Dependent Phonon Hybridization in WSe₂/WSe₂ Homobilayer