Quasiparticle band-edge energy and band offsets of monolayer of molybdenum and tungsten chalcogenides

Liang, Yufeng; Huang, Shouting; Soklaski, Ryan; Yang, Li

doi:10.1063/1.4816517

Cited by 149 publications

(147 citation statements)

References 42 publications

(60 reference statements)

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“…3b. Figure 3b clearly demonstrates that a type-II staggered gap heterojunction with a nanoscale built-in potential distribution was formed at the interface9142526. This is the first observation of the electronic structure of a TMD heterojunction.…”

Section: Resultsmentioning

confidence: 67%

Microscopic basis for the band engineering of Mo1−xWxS2-based heterojunction

Yoshida

Kobayashi

Sakurada

et al. 2015

Sci Rep

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Transition-metal dichalcogenide layered materials, consisting of a transition-metal atomic layer sandwiched by two chalcogen atomic layers, have been attracting considerable attention because of their desirable physical properties for semiconductor devices, and a wide variety of pn junctions, which are essential building blocks for electronic and optoelectronic devices, have been realized using these atomically thin structures. Engineering the electronic/optical properties of semiconductors by using such heterojunctions has been a central concept in semiconductor science and technology. Here, we report the first scanning tunneling microscopy/spectroscopy (STM/STS) study on the electronic structures of a monolayer WS2/Mo1−xWxS2 heterojunction that provides a tunable band alignment. The atomically modulated spatial variation in such electronic structures, i.e., a microscopic basis for the band structure of a WS2/Mo1−xWxS2 heterojunction, was directly observed. The macroscopic band structure of Mo1−xWxS2 alloy was well reproduced by the STS spectra averaged over the surface. An electric field of as high as 80 × 106 Vm−1 was observed at the interface for the alloy with x = 0.3, verifying the efficient separation of photoexcited carriers at the interface.

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Section: Resultsmentioning

confidence: 67%

Microscopic basis for the band engineering of Mo1−xWxS2-based heterojunction

Yoshida

Kobayashi

Sakurada

et al. 2015

Sci Rep

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“…Previous research has calculated the electronic structure of different TMD heterostructures [38][39][40][41][42][43][44][45][46]. The conduction and valence band edges in 1L MoS 2 are predicted to be lower than those in 1L WSe 2 and 1L MoSe 2 , giving rise to type II band alignment with staggered gap in their heterojunction [38,39] The strong PL suppression (up to two orders of magnitude) observed in our samples indicates that the charge transfer rate is close to the rate of exciton generation under our continuous laser excitation. Such high transfer efficiency is consistent with the remarkable transfer time scale (<50 fs) determined by ultrafast studies [11].…”

Section: Resultsmentioning

confidence: 99%

Observation of interlayer phonon modes in van der Waals heterostructures

Lui¹,

Ye²,

Ji³

et al. 2015

Phys. Rev. B

190

200

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Abstract:We have investigated the vibrational properties of van der Waals heterostructures of monolayer transition metal dichalcogenides (TMDs), specifically MoS 2 /WSe 2 and MoSe 2 /MoS 2 heterobilayers as well as twisted MoS 2 bilayers, by means of ultralow-frequency Raman spectroscopy. We discovered Raman features (at 30 ~ 40 cm -1 ) that arise from the layerbreathing mode (LBM) vibrations between the two incommensurate TMD monolayers in these structures. The LBM Raman intensity correlates strongly with the suppression of photoluminescence that arises from interlayer charge transfer. The LBM is generated only in bilayer areas with direct layer-layer contact and atomically clean interface. Its frequency also evolves systematically with the relative orientation between of the two layers. Our research demonstrates that LBM can serve as a sensitive probe to the interface environment and interlayer interactions in van der Waals materials.2

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“…The calculated K c − K v1 quasiparticle G 0 W 0 gap amounts to 2.45 eV, which is smaller by 0.3-0.5 eV to reported values. [141,140,160] This difference is attributed to structural and computational details: A G 0 W 0 calculation performed with the experimental crystal structure and a reduced k mesh of 8×8×2 yields 2.86 eV. Liang et alreported a direct band gap of 1L-MoS 2 of 2.75 eV, [160] which was obtained by G 0 W 0 calculations taking into account a Coulomb interaction truncation to avoid spurious interlayer interaction between the periodically repeated monolayers, but using the generalized plasmonpole model (GPP) for the dynamical screening and omitting SOC.…”

Section: Performance Of Different Methodologiesmentioning

confidence: 99%

“…[141,140,160] This difference is attributed to structural and computational details: A G 0 W 0 calculation performed with the experimental crystal structure and a reduced k mesh of 8×8×2 yields 2.86 eV. Liang et alreported a direct band gap of 1L-MoS 2 of 2.75 eV, [160] which was obtained by G 0 W 0 calculations taking into account a Coulomb interaction truncation to avoid spurious interlayer interaction between the periodically repeated monolayers, but using the generalized plasmonpole model (GPP) for the dynamical screening and omitting SOC. The issues of the Coulomb interaction truncation, k-point sampling, and vacuum layer thickness were also addressed by Hüser et al [161], who argued that the band gap values converged with respect to k-point sampling and slab distance are rougly 0.4 eV too small compared to the free standing monolayer (including Coulomb truncation).…”

Section: Performance Of Different Methodologiesmentioning

confidence: 99%

Vibrational and optical properties of MoS2: From monolayer to bulk

Molina-Sánchez

Hummer

Wirtz

2015

Surface Science Reports

208

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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Quasiparticle band-edge energy and band offsets of monolayer of molybdenum and tungsten chalcogenides

Cited by 149 publications

References 42 publications

Microscopic basis for the band engineering of Mo1−xWxS2-based heterojunction

Microscopic basis for the band engineering of Mo1−xWxS2-based heterojunction

Observation of interlayer phonon modes in van der Waals heterostructures

Vibrational and optical properties of MoS2: From monolayer to bulk

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