Electronic properties of the MoS<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>-WS<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>heterojunction

Kośmider, K.; Fernández-Rossier, J.

doi:10.1103/physrevb.87.075451

Cited by 462 publications

(368 citation statements)

References 49 publications

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“…Due to the type-II band alignment of the MoSe 2 -WSe 2 HS [18][19][20] , as shown in Fig. 2c, photoexcited electrons and holes will relax (dashed lines) to the conduction band edge of MoSe 2 and the valence band edge of WSe 2 , respectively.…”

Section: Mosementioning

confidence: 99%

“…Therefore, an intriguing possibility is to stack different TMD monolayers on top of one another to form 2D HSs . Firstprinciple calculations show that heterojunctions formed between monolayer tungsten and molybdenum dichalcogenides have type-II band alignment [18][19][20] . Recently, this has been confirmed by X-ray photoelectron spectroscopy and scanning tunnelling spectroscopy 21 .…”

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confidence: 99%

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Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures

et al. 2015

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Van der Waals bound heterostructures constructed with two-dimensional materials, such as graphene, boron nitride and transition metal dichalcogenides, have sparked wide interest in device physics and technologies at the two-dimensional limit. One highly coveted heterostructure is that of differing monolayer transition metal dichalcogenides with type-II band alignment, with bound electrons and holes localized in individual monolayers, that is, interlayer excitons. Here, we report the observation of interlayer excitons in monolayer MoSe 2 -WSe 2 heterostructures by photoluminescence and photoluminescence excitation spectroscopy. We find that their energy and luminescence intensity are highly tunable by an applied vertical gate voltage. Moreover, we measure an interlayer exciton lifetime of B1.8 ns, an order of magnitude longer than intralayer excitons in monolayers. Our work demonstrates optical pumping of interlayer electric polarization, which may provoke further exploration of interlayer exciton condensation, as well as new applications in two-dimensional lasers, light-emitting diodes and photovoltaic devices.

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Section: Mosementioning

confidence: 99%

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confidence: 99%

Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures

et al. 2015

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“…These compounds can be synthesized through various methods, such as mechanical exfoliation 6 , chemical vapor deposition 7 , and intercalation techniques 8 . In addition, they have quite similar lattice constants which also enable the synthesis of MoS 2 -WS 2 heterostructures with minimum interfacial defects [9][10][11][12][13] .…”

Section: Introductionmentioning

confidence: 99%

Atomic defect states in monolayers of MoS2 and WS2

Salehi

Saffarzadeh

2016

Surface Science

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The influence of atomic vacancy defects at different concentrations on electronic properties of MoS 2 and WS 2 monolayers is studied by means of Slater-Koster tight-binding model with non-orthogonal sp 3 d 5 orbitals and including the spin-orbit coupling. The presence of vacancy defects induces localized states in the bandgap of pristine MoS 2 and WS 2 , which have potential to modify the electronic structure of the systems, depending on the type and concentration of the defects. It is shown that although the contribution of metal (Mo or W) d orbitals is dominant in the formation of midgap states, the sulphur p and d orbitals have also considerable contribution in the localized states, when metal defects are introduced. Our results suggest that Mo and W defects can turn the monolayers into p-type semiconductors, while the sulphur defects make the system a n-type semiconductor, in agreement with ab initio results and experimental observations.

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“…Contrary to known exciton systems, here the exciton lifetime is long at the energy minimum while optical injection and probe are allowed at finite velocities, suggesting unique opportunities to study exciton dynamics and condensation phenomena. For lattice matching heterobilayers of AA-like (0 • twist) or AB-like (60 • twist) stacking, all light cones merge into a single one, and the quantum interference leads to dependence of the brightness and the polarization selection rules on the translation between the layers.The optically active interlayer excitons are the ones with electrons (holes) from the ±K (±K) valleys in MoX 2 (WX 2 ), where layer-hybridization is substantially quenched by the large band offsets between the layers [3,[30][31][32][33][34][35]. The term light cones here refer to the exciton phase space regions where interconversion with photon is directly allowed (without phonon or impurity assistance).…”

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Anomalous Light Cones and Valley Optical Selection Rules of Interlayer Excitons in Twisted Heterobilayers

et al. 2015

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We show that, because of the inevitable twist and lattice mismatch in heterobilayers of transition metal dichalcogenides, interlayer excitons have six-fold degenerate light cones anomalously located at finite velocities on the parabolic energy dispersion. The photon emissions at each light cone are elliptically polarized, with major axis locked to the direction of exciton velocity, and helicity specified by the valley indices of the electron and the hole. These finite-velocity light cones allow unprecedented possibilities to optically inject valley polarization and valley current, and the observation of both direct and inverse valley Hall effects, by exciting interlayer excitons. Our findings suggest potential excitonic circuits with valley functionalities, and unique opportunities to study exciton dynamics and condensation phenomena in semiconducting 2D heterostructures.PACS numbers: 74.78. Fk, 78.67.Pt, 72.25.Fe Monolayers of group-VIB transition metal dichalcogenides (TMDs) have recently emerged as a new class of direct-gap semiconductors in the two-dimensional (2D) limit [1][2][3][4][5]. These hexagonal 2D crystals have exotic properties associated with the valley degeneracy of the band edges, including the valley Hall effect [6,7], the valley magnetic moment [8][9][10][11], and the valley optical selection rules [6,[12][13][14][15][16], leading to rich possibilities for valley-based device applications. The visible range bandgap further makes these 2D semiconductors ideal platforms for optoelectronics. Due to the strong Coulomb interaction, the optical response is dominated by excitons, the hydrogen-like bound state of an electron-hole pair. The demonstrated electrostatic tunability and optical controllability of valley configurations of excitons in monolayer TMDs have implied new optoelectronic device concepts not possible in other material systems [13][14][15][16][17].Stacking different TMDs monolayers to form van der Waals heterostructures opens up a new realm to extend their already extraordinary properties [18]. MoX 2 /WX 2 (X=Se, S) heterobilayers have been realized [19][20][21][22][23][24][25], which feature a type-II band alignment with the conduction (valence) band edges located in MoX 2 (WX 2 ) layer. Exciton then has the lowest energy in an interlayer configuration (i.e. electron and hole in different layers), from which luminescence is observed [19][20][21]. Due to the spatially indirect nature, interlayer excitons in MoSe 2 /WSe 2 heterobilayers have shown long lifetime exceeding nanosecond, repulsive interaction, and electrostatically tunable resonance [19], all of which are highly desirable for the realization of excitonic circuits and condensation [26][27][28][29]. An unprecedented aspect of this interlayer exciton system is that the heterobilayers in general have incommensurate structures due to lattice mismatch and twist in the stacking which, together with the valley physics inherited from the monolayers, bring in radically new properties.Here we discover anomalous light coupling prope...

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Electronic properties of the MoS2-WS2heterojunction

Cited by 462 publications

References 49 publications

Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures

Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures

Atomic defect states in monolayers of MoS2 and WS2

Anomalous Light Cones and Valley Optical Selection Rules of Interlayer Excitons in Twisted Heterobilayers

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