Native defects in bulk and monolayer<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>from first principles

Komsa, Hannu‐Pekka; Krasheninnikov, Arkady V.

doi:10.1103/physrevb.91.125304

Cited by 486 publications

(458 citation statements)

References 141 publications

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“…These defects play a decisive role in determining the optical, electrical, and magnetic properties of the material. 10 A comprehensive knowledge about the type and concentration of the defects is essential for understanding the structure of the material. Moreover, this knowledge is also indispensable to recognize a suitable defect passivation mechanism to modify the local properties of TMDCs which result in novel functionalities of 2D devices.…”

Section: Introductionmentioning

confidence: 99%

A DFT study of intrinsic point defects in monolayer MoSe2

2017

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This study is a computational investigation of the electronic structure of the eight most-frequently observed intrinsic point-defect configurations in monolayer Molybdenum diselenide (m-MoSe2); analyzed using the Amsterdam Density Functional (ADF) BAND package. Pristine m-MoSe2 is an intrinsic semiconductor with a direct band gap of 1.44 eV. MoSe2 is defect-sensitive due to the similar orbital character of the Valence Band Maximum (VBM) and Conduction Band Minimum (CBM), with deep states induced in the structure by the defects. These states can be attributed solely to the metal d and chalcogen p states, which spring enhanced photoluminescence, making MoSe2 a potential candidate for optoelectronic applications. Band-gap narrowing is proportional to the number of chalcogen vacancies. All defect configurations cause shifting of the Fermi-level, with metal vacancies shifting the semiconducting character of pristine m-MoSe2 to metallic. Only the antisite defect configuration of MoSe2 and Mo-vacancies at a large distance could introduce spin in the structure, with spin attributed to the metal d and chalcogen p states. These findings suggest the possible application of m-MoSe2 for fabricating DMS by defect engineering.

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Section: Introductionmentioning

confidence: 99%

A DFT study of intrinsic point defects in monolayer MoSe2

2017

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“…Furthermore, exfoliated MoS 2 usually exhibits an intrinsic n doping, which has been attributed to Re impurities [19]. For these reasons, in the calculations reported below we have chosen to pin ε F to the conduction band.…”

Section: Sampling Impurity Configurationsmentioning

confidence: 99%

“…The formation energies and thermodynamics of these defects have been thoroughly studied [19], but their influence on transport and optical properties remains largely unexplored. Modeling the effects of disorder from first principles is a challenging task in general, but there are noteworthy examples where the AHC in ferromagnetic materials has been calculated using the coherent potential approximation [20][21][22][23][24][25]; also, an ab initio implementation of the side-jump contribution to the AHC has been carried out assuming scattering centers with δ-function potentials [26].…”

Section: Monolayers Of Mosmentioning

confidence: 99%

Valley Hall effect in disordered monolayerMoS2from first principles

Olsen

Souza

2015

Phys. Rev. B

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Electrons in certain two-dimensional crystals possess a pseudospin degree of freedom associated with the existence of two inequivalent valleys in the Brillouin zone. If, as in monolayer MoS 2 , inversion symmetry is broken and time-reversal symmetry is present, equal and opposite amounts of k-space Berry curvature accumulate in each of the two valleys. This is conveniently quantified by the integral of the Berry curvature over a single valley-the valley Hall conductivity. We generalize this definition to include contributions from disorder described with the supercell approach, by mapping ("unfolding") the Berry curvature from the folded Brillouin zone of the disordered supercell onto the normal Brillouin zone of the pristine crystal, and then averaging over several realizations of disorder. We use this scheme to study from first principles the effect of sulfur vacancies on the valley Hall conductivity of monolayer MoS 2 . In dirty samples the intrinsic valley Hall conductivity receives gating-dependent corrections that are only weakly dependent on the impurity concentration, consistent with side-jump scattering and the unfolded Berry curvature can be interpreted as a k-space resolved side jump. At low impurity concentrations skew scattering dominates, leading to a divergent valley Hall conductivity in the clean limit. The implications for the recently observed photoinduced anomalous Hall effect are discussed.

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“…The formation energy of a S vacancy in a MoS 2 monolayer has been theoretically estimated in the 1.3 eV-1.5 eV range. 52, 53 We consider these as upper bounds for the energy barrier of the transfer of a S atom to fill a Se vacancy in MoSe 2 , because this is not a static 6 process but a transfer between two neighbouring layers.We have also calculated the band structures of a perfect MoSe 2 monolayer, MoSe 2 monolayer with one Se vacancy, and MoSe 2 monolayer with one Se−→S substitution. We observe that Se vacancies introduce strongly localized states in the bandgap of MoSe 2 , 0.92 eV above the top of the valence band (see Fig.…”

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confidence: 99%

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures

et al. 2017

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Monolayer transition metal dichalcogenides (TMDC) grown by chemical vapor deposition (CVD) are plagued by a significantly lower optical quality compared to exfoliated TMDC. In this work we show that the optical quality of CVD-grown MoSe 2 is completely recovered if the material is sandwiched in MoS 2 /MoSe 2 /MoS 2 trilayer van der Waals heterostructures. We show by means of density-functional theory that this 1 arXiv:1703.00806v2 [cond-mat.mes-hall] 14 Jun 2017 remarkable and unexpected result is due to defect healing: S atoms of the more reactive MoS 2 layers are donated to heal Se vacancy defects in the middle MoSe 2 layer. In addition, the trilayer structure exhibits a considerable charge-transfer mediated valley polarization of MoSe 2 without the need for resonant excitation. Our fabrication approach, relying solely on simple flake transfer technique, paves the way for the scalable production of large-area TMDC materials with excellent optical quality. KeywordsChemical Vapor Deposition, transition metal dichalcogenides, van der Waals heterostructures, defect healing, charge transfer mediated valley polarization Monolayer transition metal dichalcogenides (TMDC) have a direct bandgap situated in the visible range, which makes them ideal building blocks for novel electronic and optoelectronic devices. [1][2][3][4][5][6][7][8][9][10] The bandgap of monolayer TMDCs occurs at the inequivalent (but degenerate) K and K' points of the hexagonal Brillouin zone. The broken inversion symmetry of a TMDC monolayer combined with the time reversal symmetry imposes opposite magnetic moments at the K and K' valleys. This in turn determines the characteristic circular dichroism exhibited by these materials, wherein each valley can be addressed separately with circularly polarized light of a given helicity. 11-13 Additionally, optical spectra are influenced by the strong spin-orbit coupling, which lifts the degeneracy of band states at the valence band edges, resulting in well-resolved A and B resonances, as observed in reflectivity or absorption spectra. 2,14-16 The interplay of spin-orbit coupling with broken inversion symmetry and time reversal symmetry locks the valley and spin degrees of freedom, making TMDC attractive candidates for valleytronics. 17 The spin-valley index locking along with the large 2 distance in the momentum space between K and K' valleys preserves the valley polarization observed in the degree of circular polarization (DCP) in helicity resolved photoluminescence emission. [18][19][20][21][22] Applications require a scalable fabrication platform providing high-quality large-area monolayer TMDC. Unfortunately, the most promising approach today, namely chemical vapor deposition (CVD) growth 23-27 struggles to compete with exfoliated TMDC in terms of sample quality. Low temperature PL spectroscopy of CVD-grown MoS 2 and MoSe 2 reveals broad emission from defect bound excitons, which is significantly more intense than the free exciton peak [28][29][30] and is related to chalcogen vacancies induced...

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Native defects in bulk and monolayerMoS2from first principles

Cited by 486 publications

References 141 publications

A DFT study of intrinsic point defects in monolayer MoSe2

A DFT study of intrinsic point defects in monolayer MoSe2

Valley Hall effect in disordered monolayerMoS2from first principles

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures

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Native defects in bulk and monolayerMoS2from first principles

Cited by 486 publications

References 141 publications

A DFT study of intrinsic point defects in monolayer MoSe2

A DFT study of intrinsic point defects in monolayer MoSe2

Valley Hall effect in disordered monolayerMoS2from first principles

Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS2/MoSe2/MoS2 Trilayer van der Waals Heterostructures

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Defect Healing and Charge Transfer-Mediated Valley Polarization in MoS₂/MoSe₂/MoS₂ Trilayer van der Waals Heterostructures