High carrier mobility in graphene doped using a monolayer of tungsten oxyselenide

Choi, Min Kyung; Nipane, Ankur; Kim, Brian S. Y.; Ziffer, Mark E.; Datta, Ipshita; Borah, Abhinandan; Jung, Younghun; Kim, Bumho; Rhodes, Daniel; Jindal, Apoorv; Lamport, Zachary A.; Lee, Myeong-jin; Zangiabadi, Amirali; Nair, Maya Narayanan; Taniguchi, Takashi; Watanabe, Kenji; Kymissis, Ioannis; Pasupathy, Abhay; Lipson, Michal; Zhu, Xiaoyang; Yoo, Won Jong; Hone, James; Teherani, James T.

doi:10.1038/s41928-021-00657-y

Cited by 57 publications

(41 citation statements)

References 49 publications

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“…demonstrated monolayer or few‐layer WSe 2 covered graphene devices with 1D edge contacts by using the PCL transfer technique. [ 55 ] Despite the semiconducting nature of WSe 2 , its contribution to carrier transport at the edge of WSe 2 appeared to be negligible, as the carrier accumulation in the layers is much weaker than that in graphene. As alternatives to hBN, other insulating materials such as PMMA and hydrogen silsesquioxane (HSQ) have been tested for their ability to form edge contacts to graphene.…”

Section: Recent Development Of Edge Contact Methodsmentioning

confidence: 99%

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

et al. 2022

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It is therefore becoming increasingly important to analyze the electronic properties of nanometer scale semiconductors from the quantum mechanical perspective. Due to their atomic thickness, 2D materials (2DMs) are considered to be the best candidates for revealing the quantum mechanical properties when used as semiconducting channel materials in electronic devices, thus representing alternatives to the conventional semiconducting materials such as Si and GaAs. [1] However, the use of 2DMs leads to large contact resistance (R C ) when they are in contact with metallic electrodes, since they form a metallic interface that depends on van der Waals (vdW) bonding, which induces the vdW gap and generates metalinduced gap states, ultimately resulting in Fermi-level pinning (FLP). [2,3] As a result, the electronic mobility of the metal-contacted 2DM based devices is found to be much lower than the theoretically expected value, thus preventing their quantum properties from being observed. Therefore, minimizing the R C of the devices using 2DMs represents the most important challenge for exploring the novel quantum electronic properties of the devices. In this regard, there have been substantial efforts to reduce the R C by using novel contact strategies. [4,5] Clean vdW contacts either by transferring metal/ semimetal electrodes or depositing indium on 2D semiconductors have been proposed to obtain high-quality metal-semiconductor (MS) interfaces without generating metallization induced defects. [6][7][8][9][10][11] High density doping achieved by chemical dopants, substitutional doping, solid oxides, and semimetals has also been utilized to reduce the R C significantly. [12][13][14][15][16][17][18][19][20] However, such contacts were typically placed onto the vdW surface of 2D semiconductors resulting in the formation of vdW tunneling barriers as well as the limitation in lateral scaling of the devices. Here, the 1D edge contact methods have been studied intensively as a very suitable technique for achieving a vdW gap-free electrical contact in scaled 2D devices.Edge-contacted 2D devices were first demonstrated for the purpose of suppressing scattering from the surface of 2DMs by encapsulating graphene with 2D hBN. [21] Following this initial report, the 1D edge contact method became more widely employed due to its additional advantages in the operation of 2D devices: the realization of Fermi-level depinning Recent studies have intensively examined 2D materials (2DMs) as promising materials for use in future quantum devices due to their atomic thinness. However, a major limitation occurs when 2DMs are in contact with metals: a van der Waals (vdW) gap is generated at the 2DM-metal interfaces, which induces metal-induced gap states that are responsible for an uncontrollable Schottky barrier (SB), Fermi-level pinning (FLP), and high contact resistance (R C ), thereby substantially lowering the electronic mobility of 2DMbased devices. Here, vdW-gap-free 1D edge contact is reviewed for use in 2D devices with substantially su...

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Section: Recent Development Of Edge Contact Methodsmentioning

confidence: 99%

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

et al. 2022

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“…Recently, the formation of solid‐state non‐stoichiometric tungsten oxide (WO x ) using oxygen plasma or UV–ozone treatments, which induces a strong p‐doping effect on the underlying TMD layer, has been studied to overcome the drawbacks of TMDs by improving R C of the 2D TMDs FETs. [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ] Furthermore, protection of the underlying layer by the self‐limiting nature of the oxidation process has been demonstrated. [ 24 ] However, a lack of area‐selective doping leading to a degenerately doped channel leads to poor gate tunability of the 2D FETs, which is unfavorable for logic devices.…”

Section: Introductionmentioning

confidence: 99%

Selective Electron Beam Patterning of Oxygen‐Doped WSe₂ for Seamless Lateral Junction Transistors

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Surface charge transfer doping (SCTD) using oxygen plasma to form a p‐type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field‐effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p‐type (p+)‐doped WSe2 FETs via electron beam (e‐beam) irradiation is reported. The effect of the selective e‐beam irradiation is confirmed by the gate‐tunable optical responses of seamless lateral p+–p diodes. The OFF state of the devices by inducing trapped charges via selective e‐beam irradiation onto a desired channel area in p+‐doped WSe2, which is in sharp contrast to globally p+‐doped WSe2 FETs, is realized. Selective e‐beam irradiation of the PMMA‐passivated p+‐WSe2 enables accurate control of the threshold voltage (Vth) of WSe2 devices by varying the pattern size and e‐beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high‐performance WSe2 p‐FETs with a saturation current of −280 µA µm−1 and on/off ratio of 109 are achieved. This study's technique demonstrates a facile approach to obtain high‐performance TMD p‐FETs by e‐beam irradiation, enabling efficient switching and patternability toward various junction devices.

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“…Polariton momentum and dissipation, quantified by real and imaginary , respectively, were extracted from observed wavelengths and propagation lengths (Methods). We used oxidized tungsten diselenide (WO x ) to dope graphene 26 by a charge transfer process (Methods). Doping graphene using thin high-work-function materials like WO x or α-RuCl 3 has proven to be nondetrimental to s-SNOM imaging 27 , 28 .…”

Section: Resultsmentioning

confidence: 99%

Surface plasmons induce topological transition in graphene/α-MoO3 heterostructures

et al. 2022

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Polaritons in hyperbolic van der Waals materials—where principal axes have permittivities of opposite signs—are light-matter modes with unique properties and promising applications. Isofrequency contours of hyperbolic polaritons may undergo topological transitions from open hyperbolas to closed ellipse-like curves, prompting an abrupt change in physical properties. Electronically-tunable topological transitions are especially desirable for future integrated technologies but have yet to be demonstrated. In this work, we present a doping-induced topological transition effected by plasmon-phonon hybridization in graphene/α-MoO3 heterostructures. Scanning near-field optical microscopy was used to image hybrid polaritons in graphene/α-MoO3. We demonstrate the topological transition and characterize hybrid modes, which can be tuned from surface waves to bulk waveguide modes, traversing an exceptional point arising from the anisotropic plasmon-phonon coupling. Graphene/α-MoO3 heterostructures offer the possibility to explore dynamical topological transitions and directional coupling that could inspire new nanophotonic and quantum devices.

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High carrier mobility in graphene doped using a monolayer of tungsten oxyselenide

Cited by 57 publications

References 49 publications

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Selective Electron Beam Patterning of Oxygen‐Doped WSe₂ for Seamless Lateral Junction Transistors

Surface plasmons induce topological transition in graphene/α-MoO3 heterostructures

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High carrier mobility in graphene doped using a monolayer of tungsten oxyselenide

Cited by 57 publications

References 49 publications

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Recent Progress in 1D Contacts for 2D‐Material‐Based Devices

Selective Electron Beam Patterning of Oxygen‐Doped WSe2 for Seamless Lateral Junction Transistors

Surface plasmons induce topological transition in graphene/α-MoO3 heterostructures

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Selective Electron Beam Patterning of Oxygen‐Doped WSe₂ for Seamless Lateral Junction Transistors