Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition

Liu, Zheng; Amani, Matin; Najmaei, Sina; Xu, Quan; Zou, Xiaolong; Zhou, Wu; Yu, Ting; Qiu, Caiyu; Birdwell, A. Glen; Crowne, F. J.; Vajtai, Róbert; Yakobson, Boris I.; Xia, Zhaoqiang; Dubey, Madan; Ajayan, Pulickel M.; Lou, Jun

doi:10.1038/ncomms6246

Cited by 480 publications

(549 citation statements)

References 43 publications

(57 reference statements)

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“…We find that for both excitons the value of the valley g factor is approximately independent of the temperature. In CVD grown samples, strain is naturally induced by the growth at high temperatures [30,31]. Our results demonstrate that the strain induced by the different coefficients of thermal expansion of the TMD and the sapphire substrate has a negligible influence on the electronic properties.…”

Section: Introductionmentioning

confidence: 74%

Magnetoexcitons in large area CVD-grown monolayerMoS2andMoSe2on sapphire

et al. 2016

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Magnetotransmission spectroscopy was employed to study the valley Zeeman effect in large area monolayer MoS 2 and MoSe 2 . The extracted values of the valley g factors for both A and B excitons were found to be similar with g v −4.5. The samples are expected to be strained due to the CVD growth on sapphire at high temperature (700• C). However, the estimated strain, which is maximum at low temperature, is only 0.2%. Theoretical considerations suggest that the strain is too small to significantly influence the electronic properties. This is confirmed by the measured value of the valley g factor, and the measured temperature dependence of the band gap, which are almost identical for CVD and mechanically exfoliated MoS 2 .

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Section: Introductionmentioning

confidence: 74%

Magnetoexcitons in large area CVD-grown monolayerMoS2andMoSe2on sapphire

et al. 2016

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“…36 Moreover, the tailored PL intensity is also related to the band structure change via an extra-strain effect induced by merged defects. 37 The broadened and redshifted PL spectrum of the hexagonal monolayer compared to that of the triangular monolayer indicates the possible involvement of defect-assisted quenching in the PL emission. 36 In fact, the activity of those defect states can be diminished using a nonoxidizing organic superacid, such as bis(trifluoromethane)sulfonimide, providing a drastic enhancement of the PL emission.…”

Section: Synthesis Of Multi-stacked Mos 2 Crystalsmentioning

confidence: 99%

Stacking-controllable interlayer coupling and symmetric configuration of multilayered MoS2

et al. 2018

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The stacking order in layered transition-metal dichalcogenides (TMDCs) induces variations in the electronic and interlayer couplings. Therefore, controlling the stacking orientations when synthesizing TMDCs is desirable but remains a significant challenge. Here, we developed and showed the growth kinetics of different shapes and stacking orders in as-grown multi-stacked MoS 2 crystals and revealed the stacking-order-induced interlayer separations, spin-orbit couplings (SOCs), and symmetry variations. Raman spectra in AA(A…)-stacked crystals demonstrated blueshifted out-of-plane (A 1g ) and in-plane (E 2g 1 ) phonon frequencies, representing a greater reduction of the van der Waals gap compared to conventional AB(A…)-stacking. Our observations, together with first-principles calculations, revealed distinct excitonic phenomena due to various stacking orientations. As a result, the photoluminescence emission was improved in the AA(A…)-stacking configuration. Additionally, calculations showed that the valence-band maxima (VBM) at the K point of the AA(A…)-stacking configuration was separated into multiple sub-bands, indicating the presence of stronger SOC. We demonstrated that AA(A…)-stacking emitted an intense second-harmonic signal (SHG) as a fingerprint of the more augmented non-centrosymmetric stacking and enabled SOC-induced splitting at the VBM. We further highlighted the superiority of four-wave mixing-correlated SHG microscopy to quickly resolve the symmetries and multi-domain crystalline phases of differently shaped crystals. Our study based on crystals with different shapes and multiple stacking configurations provides a new avenue for development of future optoelectronic devices.

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“…The flakes are equilateral triangles, as it is a commonly synthesized shape. [40][41][42][43] In this case, carriers are confined in the two directions of space and we must numerically solve the coupled differential equations in two variables in order to find eigenvalues and eigenfunctions of the Hamiltonian. In the results that follow, Fig.…”

Section: B Mos2 Triangular Quantum Dotsmentioning

confidence: 99%

Edge states in dichalcogenide nanoribbons and triangular quantum dots

2016

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The electronic structure of monolayer MoS2 nanoribbons and quantum dots have been investigated by means of an effective k · p two-band model. Both systems with borders exhibit states spatially localized on the edges and with energies lying in the band gap. We show that the conduction and valence band curvatures determine the presence/absence of these states whose origin has been related to the marginal topological properties of the MoS2 single-valley Hamiltonian.

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Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition

Cited by 480 publications

References 43 publications

Magnetoexcitons in large area CVD-grown monolayerMoS2andMoSe2on sapphire

Magnetoexcitons in large area CVD-grown monolayerMoS2andMoSe2on sapphire

Stacking-controllable interlayer coupling and symmetric configuration of multilayered MoS2

Edge states in dichalcogenide nanoribbons and triangular quantum dots

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