Realization and electrical characterization of ultrathin crystals of layered transition-metal dichalcogenides

Ayari, A.; Cobas, Enrique; Ogundadegbe, Ololade; Fuhrer, Michael S.

doi:10.1063/1.2407388

Cited by 562 publications

(488 citation statements)

References 20 publications

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“…S4 and in the Supplementary methods. We note that the gate capacitance in this geometry is ~20 times higher than a recent report 7 . As a result, while exhibiting the high on/off ratio expected of a semiconductor with a bandgap of 1.3 eV, a sharp SS (~80 mV per decade for Fig.…”

Section: Resultscontrasting

confidence: 51%

High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals

et al. 2012

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unlike graphene, the existence of bandgaps (1-2 eV) in the layered semiconductor molybdenum disulphide, combined with mobility enhancement by dielectric engineering, offers an attractive possibility of using single-layer molybdenum disulphide field-effect transistors in low-power switching devices. However, the complicated process of fabricating single-layer molybdenum disulphide with an additional high-k dielectric layer may significantly limit its compatibility with commercial fabrication. Here we show the first comprehensive investigation of processfriendly multilayer molybdenum disulphide field-effect transistors to demonstrate a compelling case for their applications in thin-film transistors. our multilayer molybdenum disulphide field-effect transistors exhibited high mobilities ( > 100 cm 2 V − 1 s − 1 ), near-ideal subthreshold swings (~70 mV per decade) and robust current saturation over a large voltage window. With simulations based on shockley's long-channel transistor model and calculations of scattering mechanisms, these results provide potentially important implications in the fabrication of highresolution large-area displays and further scientific investigation of various physical properties expected in other layered semiconductors.

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Section: Resultscontrasting

confidence: 51%

High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals

et al. 2012

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“…The electronic band structure of graphene has a linear dispersion near the K point, and charge carriers can be described as massless Dirac fermions, providing scientists with an abundance of new physics 2,3 . Graphene is a unique example of an extremely thin electrical and thermal conductor 4 , with high carrier mobility 5 , and surprising molecular barrier properties 6,7 .Many other 2D materials are known, such as the TMDCs 8,9 , transition metal oxides including titania-and perovskite-based oxides 10,11 , and graphene analogues such as boron nitride (BN) 12,13 . In particular, TMDCs show a wide range of electronic, optical, mechanical, chemical and thermal properties that have been studied by researchers for decades 9,14,15 .…”

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confidence: 99%

“…Many other 2D materials are known, such as the TMDCs 8,9 , transition metal oxides including titania-and perovskite-based oxides 10,11 , and graphene analogues such as boron nitride (BN) 12,13 . In particular, TMDCs show a wide range of electronic, optical, mechanical, chemical and thermal properties that have been studied by researchers for decades 9,14,15 .…”

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confidence: 99%

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

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699M any two-dimensional (2D) materials exist in bulk form as stacks of strongly bonded layers with weak interlayer attraction, allowing exfoliation into individual, atomically thin layers 1 . The form receiving the most attention today is graphene, the monolayer counterpart of graphite. The electronic band structure of graphene has a linear dispersion near the K point, and charge carriers can be described as massless Dirac fermions, providing scientists with an abundance of new physics 2,3 . Graphene is a unique example of an extremely thin electrical and thermal conductor 4 , with high carrier mobility 5 , and surprising molecular barrier properties 6,7 .Many other 2D materials are known, such as the TMDCs 8,9 , transition metal oxides including titania-and perovskite-based oxides 10,11 , and graphene analogues such as boron nitride (BN) 12,13 . In particular, TMDCs show a wide range of electronic, optical, mechanical, chemical and thermal properties that have been studied by researchers for decades 9,14,15 . There is at present a resurgence of scientific and engineering interest in TMDCs in their atomically thin 2D forms because of recent advances in sample preparation, optical detection, transfer and manipulation of 2D materials, and physical understanding of 2D materials learned from graphene.The 2D exfoliated versions of TMDCs offer properties that are complementary to yet distinct from those in graphene. Graphene displays an exceptionally high carrier mobility exceeding 10 6 cm 2 V -1 s -1 at 2 K (ref. 16) and exceeding 10 5 cm 2 V -1 s -1 at room temperature for devices encapsulated in BN dielectric layers 5 ; because pristine graphene lacks a bandgap, however, fieldeffect transistors (FETs) made from graphene cannot be effectively switched off and have low on/off switching ratios. Bandgaps can be engineered in graphene using nanostructuring [17][18][19] , chemical functionalization 20 and applying a high electric field to bilayer graphene 21 , but these methods add complexity and diminish mobility. In contrast, several 2D TMDCs possess sizable bandgaps around 1-2 eV (refs 9,14), promising interesting new FET and optoelectronic devices.TMDCs are a class of materials with the formula MX 2 , where M is a transition metal element from group IV (Ti, Zr, Hf and so on), group V (for instance V, Nb or Ta) or group VI (Mo, W and so on), and X is a chalcogen (S, Se or Te). These materials form layered structures of the form X-M-X, with the chalcogen atoms in two hexagonal planes separated by a plane of metal atoms, as shown in Fig. 1a. Adjacent layers are weakly held together to form the bulk crystal in a variety of polytypes, which vary in stacking orders and metal atom coordination, as shown in Fig. 1e. The overall symmetry of TMDCs is hexagonal or rhombohedral, and the metal atoms have octahedral or trigonal prismatic coordination. The electronic properties of TMDCs range from metallic to semiconducting, as summarized in Table 1. There are also TMDCs that exhibit exotic behaviours such as charge density waves ...

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“…[1][2][3][4][5] However, over the last few years, it has become clear that a range of other inorganic layered compounds can be mechanically exfoliated in small quantities to give 2-dimensional nanosheets with interesting properties. [6][7][8][9][10] For example, exfoliated hexagonal boron nitride has been used as a dielectric support in graphene-based transistors 11 while MoS 2 has been fabricated into sensors 10,12 , transistors [13][14][15] and integrated circuits. 16 The availability of a wide range of 2-dimensional materials is important as it allows access to a broad palette of physical and chemical properties.…”

Section: Toc Figmentioning

confidence: 99%

Solvent Exfoliation of Transition Metal Dichalcogenides: Dispersibility of Exfoliated Nanosheets Varies Only Weakly between Compounds

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Abstract:We have studied the dispersion and exfoliation of four inorganic layered compounds, WS 2 , We found that the dispersed concentration of each material falls exponentially with  as predicted by solution thermodynamics. This work shows that solution thermodynamics and specifically solubility parameter analysis can be used as a framework to understand the dispersion of 2-dimensional materials. Finally, we note that in good solvents such as 2 cyclohexylpyrrolidone, the dispersions are temporally stable with >90% of material remaining dispersed after 100 hours. ToC figOver the last decade, 2-dimensional nanomaterials have become one of the most studied subfields of nanoscience. These developments have been spearheaded by research into graphene, a material that is unique due to its combination of thermal, electronic, optical and mechanical properties. 1-5 However, over the last few years, it has become clear that a range of other inorganic layered compounds can be mechanically exfoliated in small quantities to give 2-dimensional nanosheets with interesting properties. 6-10 For example, exfoliated hexagonal boron nitride has been used as a dielectric support in graphene-based transistors 11 while MoS 2 has been fabricated into sensors 10, 12 , transistors 13-15 and integrated circuits. 16 The availability of a wide range of 2-dimensional materials is important as it allows access to a broad palette of physical and chemical properties. A good example is provided by the family of transition metal dichalcogenides (TMDs). These materials have the chemical composition MX 2 where M is a transition metal (commonly, but not limited to Ti, Nb, Ta, Mo, W) and X is a chalcogen (i.e. S, Se, Te). As in graphite, these atoms are covalently bonded into nanosheets which stack into 3-dimensional crystals by van der Waals interactions. These materials are of particular interest because, depending on the combination of metal and chalcogen, the material can be semiconducting or metallic. 17 In addition, the bandgap can vary from a few hundred meV to a few eV, 17 suggesting these materials have potential as versatile electronic device materials.Furthermore, these materials have interesting electrochemical properties which make them suitable for applications such as battery electrodes. 18,19 As with graphene, many applications will require relatively large quantities of material suggesting that a solution processing route is required. 20 A number of possibilities exist. For example, it has been known for many years that materials such as MoS 2 can be exfoliated by 3 lithium intercalation. 21 However, such a route tends to result in structural deformations in some TMDs leading to considerably altered electronic properties. 22 Alternatively, TMDs can be synthesised in the liquid phase. 7,8 Probably the simplest route to liquid exfoliation of layered compounds is sonication assisted exfoliation in solvents [23][24][25][26][27][28][29] or aqueous surfactant solutions. 19,[30][31][32] Here, sonication results in the exfoliation of the ...

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Realization and electrical characterization of ultrathin crystals of layered transition-metal dichalcogenides

Cited by 562 publications

References 20 publications

High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals

High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

Solvent Exfoliation of Transition Metal Dichalcogenides: Dispersibility of Exfoliated Nanosheets Varies Only Weakly between Compounds

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