Quantitative Determination of the Band Gap of WS<sub>2</sub> with Ambipolar Ionic Liquid-Gated Transistors

Braga, Daniele; Lezama, Ignacio Gutiérrez; Berger, H.; Morpurgo, Alberto F.

doi:10.1021/nl302389d

Cited by 501 publications

(501 citation statements)

References 55 publications

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“…[10][11][12][13][14] These materials are of great interest due to their potential applications in optoelectronics. 11,13,15,16 Recently we discussed a new member of this family: atomically thin layers of hexagonal gallium chalcogenides, 17 which are indirect-band-gap semiconductors with unusual, sombrero-shaped valenceband edges and optical absorption spectra that are dominated by zone-edge transitions. In this work we study closely related materials: 2D crystals of indium chalcogenides (In 2 X 2 , where X is S, Se, or Te).…”

Section: Introductionmentioning

confidence: 99%

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

2014

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We use density functional theory to calculate the electronic band structures, cohesive energies, phonon dispersions, and optical absorption spectra of two-dimensional In2X2 crystals, where X is S, Se, or Te. We identify two crystalline phases (α and β) of monolayers of hexagonal In2X2, and show that they are characterized by different sets of Raman-active phonon modes. We find that these materials are indirect-band-gap semiconductors with a sombrero-shaped dispersion of holes near the valence-band edge. The latter feature results in a Lifshitz transition (a change in the Fermi-surface topology of hole-doped In2X2) at hole concentrations nS = 6.86×10 13 cm −2 , nSe = 6.20×10 13 cm −2 , and nTe = 2.86 × 10 13 cm −2 for X=S, Se, and Te, respectively, for α-In2X2 and nS = 8.32 × 10 13 cm −2 , nSe = 6.00 × 10 13 cm −2 , and nTe = 8.14 × 10 13 cm −2 for β-In2X2.

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Section: Introductionmentioning

confidence: 99%

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

2014

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“…This class of layered materials with chemical composition of MX 2 , where M and X correspond to the transition metal and the chalcogen elements, respectively, crystallizes in a hexagonal structure like graphene in which the M-atom layer is covalently bonded and sandwiched between the two X-atom layers. Among LTMD materials, MoS 2 and WS 2 monolayers with a direct bandgap configuration have been extensively investigated because of many intriguing physical and chemical properties [3][4][5] . These compounds can be synthesized through various methods, such as mechanical exfoliation 6 , chemical vapor deposition 7 , and intercalation techniques 8 .…”

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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“…Furthermore, the 1T phase MoS 2 is thermally unstable above 100 o C. The availability of a variety of semiconducting TMDs such as MoSe 2 , WS 2 and WSe 2 with different band structures and charge neutrality levels offers additional distinct properties and opportunities for device applications. 5,6,8,9,13,[26][27][28][29][30][31][32][33][34][35][36][37] However, the variation of electron affinity, band gap, and band alignments also presents significant challenges to contact engineering. To unlock the full potential of TMDs as channel materials for high-performance thin-film transistors, highly effective and versatile contact strategies for making low-resistance ohmic contacts are needed.…”

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Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors

et al. 2016

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We report a new strategy for fabricating 2D/2D low-resistance ohmic contacts for a variety of transition metal dichalcogenides (TMDs) using van der Waals assembly of substitutionally doped TMDs as drain/source contacts and TMDs with no intentional doping as channel materials. We demonstrate that few-layer WSe 2 field-effect transistors (FETs) with 2D/2D contacts exhibit low contact resistances of ~ 0.3 kΩ µm, high on/off ratios up to > 10 9 , and high drive currents exceeding 320 µA µm -1 . These favorable characteristics are combined with a two-terminal field-effect hole mobility μ FE ≈ 2×10 2 cm 2 V -1 s -1 at room temperature, which increases to >2×10 3 cm 2 V -1 s -1 at cryogenic temperatures. We observe a similar performance also in MoS 2 and MoSe 2 FETs with 2D/2D drain and source contacts. The 2D/2D low-resistance ohmic contacts presented here represent a new device paradigm that overcomes a significant bottleneck in the performance of TMDs and a wide variety of other 2D materials as the channel materials in post-silicon electronics.

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Quantitative Determination of the Band Gap of WS₂ with Ambipolar Ionic Liquid-Gated Transistors

Cited by 501 publications

References 55 publications

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

Atomic defect states in monolayers of MoS2 and WS2

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors

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Quantitative Determination of the Band Gap of WS2 with Ambipolar Ionic Liquid-Gated Transistors

Cited by 501 publications

References 55 publications

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

Electrons and phonons in single layers of hexagonal indium chalcogenides fromab initiocalculations

Atomic defect states in monolayers of MoS2 and WS2

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe2, MoS2, and MoSe2 Transistors

Contact Info

Product

Resources

About

Quantitative Determination of the Band Gap of WS₂ with Ambipolar Ionic Liquid-Gated Transistors

Low-Resistance 2D/2D Ohmic Contacts: A Universal Approach to High-Performance WSe₂, MoS₂, and MoSe₂ Transistors