Air-stable and efficient electron doping of monolayer MoS<sub>2</sub> by salt–crown ether treatment

Ogura, Hiroto; Kaneda, Masahiko; Nakanishi, Yusuke; Nonoguchi, Yoshiyuki; Pu, Jiang; Ohfuchi, Mari; Irisawa, Toshifumi; Lim, Hong En; Endo, Takahiko; Yanagi, Kazuhiro; Takenobu, Taishi; Miyata, Yasumitsu

doi:10.1039/d1nr01279g

Cited by 14 publications

(10 citation statements)

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“…Multilayer Nb x Mo 1– x S 2 and WSe 2 flakes were prepared by mechanical exfoliation of bulk crystals on SiO 2 (285 nm)/Si substrates. MoS 2 was grown via salt-assisted CVD using a lab-made setup with two electric furnaces. ,, The exfoliated Nb x Mo 1– x S 2 or WSe 2 flakes on SiO 2 /Si substrates were placed in a quartz tube, and MoO 2 powder (40–70 mg), KBr powder (3–8 mg), and sulfur flakes (2–3 g) were placed 1, 2, and 30 cm upstream from the substrates, respectively. The quartz tube was then filled with N 2 gas at flow rates of 150–300 sccm.…”

Section: Experimental Methodsmentioning

confidence: 99%

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

et al. 2023

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In-plane heterostructures of transition metal dichalcogenides (TMDCs) have attracted much attention for high-performance electronic and optoelectronic devices. To date, mainly monolayer-based in-plane heterostructures have been prepared by chemical vapor deposition (CVD), and their optical and electrical properties have been investigated. However, the low dielectric properties of monolayers prevent the generation of high concentrations of thermally excited carriers from doped impurities. To solve this issue, multilayer TMDCs are a promising component for various electronic devices due to the availability of degenerate semiconductors. Here, we report the fabrication and transport properties of multilayer TMDC-based in-plane heterostructures. The multilayer in-plane heterostructures are formed through CVD growth of multilayer MoS2 from the edges of mechanically exfoliated multilayer flakes of WSe2 or Nb x Mo1–x S2. In addition to the in-plane heterostructures, we also confirmed the vertical growth of MoS2 on the exfoliated flakes. For the WSe2/MoS2 sample, an abrupt composition change is confirmed by cross-sectional high-angle annular dark-field scanning transmission electron microscopy. Electrical transport measurements reveal that a tunneling current flows at the Nb x Mo1–x S2/MoS2 in-plane heterointerface, and the band alignment is changed from a staggered gap to a broken gap by electrostatic electron doping of MoS2. The formation of a staggered gap band alignment of Nb x Mo1–x S2/MoS2 is also supported by first-principles calculations.

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Section: Experimental Methodsmentioning

confidence: 99%

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

et al. 2023

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“…We would like to show a representative approach to the stable doping of MoS 2 monolayer and its full characterization. Miyata and colleagues have recently reported that MoS 2 monolayer doped with the compexes of potassium hydroxide and crown ether shows air-stable, metallic conduction [48]. They found a dramatic increase in current density in MoS 2 field effect transistors upon the supramolecular doping.…”

Section: Molecularly and Supramolecularly Doped N-type Transition-met...mentioning

confidence: 99%

Molecular electron doping to single-walled carbon nanotubes and molybdenum disulfide monolayers

2022

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Carrier doping is an essential way to modulate the transport properties of electronic materials. While the substitution of heteroatoms essentially modulates the band structure of most semiconducting materials, chemical (molecular) doping can achieve relatively reliable carrier concentration modulation, particularly for nanocarbons and two-dimensional semiconductors. Compared to p-type counterparts, the stabilization of n-type carbon materials has been a challenge not only for basic science but also for various electronic device applications. This Mini-Review describes rational concepts for, and the results of, a stable n-type doping technique mainly for carbon nanotubes using molecular reactions and interactions. The stable n-type carbon nanotubes with controlled carrier concentration are implemented in complementary circuits and thermoelectric energy harvesters. The molecular and supramolecular n-type doping is not limited for carbon nanotubes, but is utilized in the fabrication of conducting transition metal dichalcogenides such as a molybdenum disulphide (MoS2) monolayer.

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“…Surface charge transfer doping has been employed to tune a wide range of carrier concentrations in TMDCs on metal-oxide-semiconductor FETs (MOSFETs). This doping method causes no damage to the lattice, and the doping level is available to a degenerate state at 10 13 cm –2 in both n- and p-types in TMDCs. − One of the strongest modulating agents is an organic dopant, the benzyl viologen (BV) molecule, because it has a high reduction potential. , Previously, BV molecules have achieved electron doping into MoS 2 MOSFETs over the 10 13 cm –2 range in a multilayer flake . The postdoped MOSFETs showed a small gate voltage ( V G ) dependence, indicating a degenerately doped state in the channel MoS 2 . ,, This level of high carrier concentrations would further induce metallic or quantum phase transformations.…”

Section: Introductionmentioning

confidence: 99%

Metallic Transport in Monolayer and Multilayer Molybdenum Disulfides by Molecular Surface Charge Transfer Doping

Matsuyama

Aoki

Miura

et al. 2022

ACS Appl. Mater. Interfaces

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Carrier modulation in transition-metal dichalcogenides (TMDCs) is of importance for applying electronic devices to tune their transport properties and controlling phases, including metallic to superconductivity. Although the surface charge transfer doping method has shown a strong modulation ability of the electronic structures in TMDCs and a degenerately doped state has been proposed, the details of the electronic states have not been elucidated, and this transport behavior should show a considerable thickness dependence in TMDCs. In this study, we characterize the metallic transport behavior in the monolayer and multilayer MoS2 under surface charge transfer doping with a strong electron dopant, benzyl viologen (BV) molecules. The metallic behavior transforms to an insulative state under a negative gate voltage. Consequently, metal–insulator transition (MIT) was observed in both monolayer and multilayer MoS2 correlating with the critical conductivity of order e 2/h. In the multilayer case, the BV molecules strongly modulated the topmost surface layer in the bulk MoS2; the transfer characteristics suggested a crossover from a heterogeneously doped state with a doped topmost layer to doping in the deep layers caused by the variation in the gate voltage. The findings of this work will be useful for understanding the device characteristics of thin-layered materials and for applying them to the controlling phases via carrier modulation.

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Air-stable and efficient electron doping of monolayer MoS₂ by salt–crown ether treatment

Abstract: To maximize the potential of transition-metal dichalcogenides (TMDCs) in device applications, the development of a sophisticated technique for stable and highly efficient carrier doping is critical. Here, we report the...

Cited by 14 publications

References 47 publications

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

Molecular electron doping to single-walled carbon nanotubes and molybdenum disulfide monolayers

Metallic Transport in Monolayer and Multilayer Molybdenum Disulfides by Molecular Surface Charge Transfer Doping

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Air-stable and efficient electron doping of monolayer MoS2 by salt–crown ether treatment

Abstract: To maximize the potential of transition-metal dichalcogenides (TMDCs) in device applications, the development of a sophisticated technique for stable and highly efficient carrier doping is critical. Here, we report the...

Cited by 14 publications

References 47 publications

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics

Molecular electron doping to single-walled carbon nanotubes and molybdenum disulfide monolayers

Metallic Transport in Monolayer and Multilayer Molybdenum Disulfides by Molecular Surface Charge Transfer Doping

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Air-stable and efficient electron doping of monolayer MoS₂ by salt–crown ether treatment