Effect of high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>κ</mml:mi></mml:math>gate dielectrics on charge transport in graphene-based field effect transistors

Konar, Aniruddha; Tian, Fang; Jena, Debdeep

doi:10.1103/physrevb.82.115452

Cited by 280 publications

(221 citation statements)

References 41 publications

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“…Engineering the dielectric environment can enhance mobilities 106 , as has been demonstrated for graphene 107,108 and for MoS 2 (ref. 34).…”

Section: Electrical Transport and Devicesmentioning

confidence: 72%

“…The top-gated geometry allows for a reduction in the voltage necessary to switch the device while allowing the integration of multiple devices on the same substrate. The high-k dielectric used in this device, HfO 2 , also gave the additional benefit of improving the mobility of monolayer MoS 2 owing to dielectric engineering as discussed earlier 106,107,116,117 . Topgating with a high-k dielectric was also used in a p-type FET with an active channel made of a monolayer flake of WSe 2 , which exhibited room-temperature performance of ~250 cm 2 V -1 s -1 hole mobility, ~60 mV per decade subthreshold swing and 10 6 on/off ratio 118 .…”

Section: Electrical Transport and Devicesmentioning

confidence: 99%

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Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

et al. 2012

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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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“…Engineering the dielectric environment can enhance mobilities 106 , as has been demonstrated for graphene 107,108 and for MoS 2 (ref. 34).…”

Section: Electrical Transport and Devicesmentioning

confidence: 72%

Section: Electrical Transport and Devicesmentioning

confidence: 99%

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

et al. 2012

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“…Moreover, charged impurity scattering in these devices can be damped using high k dielectrics (dielectric engineering) [24][25][26] . Effects such as remote phonon scattering could limit this improvement 27 . As the current experimental values are far below limits expected of remote phonon scattering, there is ample room for improvement.…”

Section: Resultsmentioning

confidence: 99%

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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“…For example, samples with the commonly used SiO 2 substrate replaced by hexagonal boron nitride (h-BN) which has a lattice constant very close to that of graphene and an almost atomically flat surface with strongly reduced disorder, 12,13 have shown highly improved transport characteristics with mobilities approaching that of suspended graphene. 8,14,15 Furthermore, the high energy of the surface-optical phonons of h-BN results in a significant reduction of surface-optical phonon scattering [16][17][18] that for commonly used gate oxides starts to dominate the mobility around T ∼ 150-200 K. 5,7 When the mobility is dominated by acoustic phonon scattering, two transport regimes separated by the Bloch-Grüneisen (BG) temperature T BG = 2hk F c ph /k B can be identified. 19 Here, k F is the Fermi wave vector, c ph the sound velocity, and k B the Boltzmann constant (T BG ∼ 57 K √ n for the longitudinal acoustic phonon with the two-dimensional carrier density n measured in units of 10 12 cm −2 ).…”

Section: Introductionmentioning

confidence: 99%

Unraveling the acoustic electron-phonon interaction in graphene

2012

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Using a first-principles approach we calculate the electron-phonon couplings in graphene for the transverse and longitudinal acoustic phonons. Analytic forms of the coupling matrix elements valid in the long-wavelength limit are found to give an almost quantitative description of the first-principles matrix elements even at shorter wavelengths. Using the analytic forms of the coupling matrix elements, we study the acoustic phonon-limited carrier mobility and quasiparticle lifetime observable in photoemission spectroscopy for temperatures 0-200 K and high carrier densities of 10 12 -10 13 cm −2 . We find that the intrinsic effective acoustic deformation potential of graphene is eff = 6.8 eV and that the temperature dependence of the mobility μ ∼ T −α in the Bloch-Grüneisen regime increases beyond an α = 4 dependence even in the absence of screening when the true coupling matrix elements are considered. The α > 4 temperature dependence of the mobility is found to originate in a similar temperature dependence of the relaxation time at the Fermi level. The large disagreement between our calculated deformation potential and those extracted from experimental measurements (18-29 eV) indicates that additional or modified acoustic phonon-scattering mechanisms are at play in experimental situations.

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Effect of high-κgate dielectrics on charge transport in graphene-based field effect transistors

Cited by 280 publications

References 41 publications

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides

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

Unraveling the acoustic electron-phonon interaction in graphene

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