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Mobility engineering and a metal–insulator transition in monolayer MoS2

Abstract

Two-dimensional (2D) materials are a new class of materials with interesting physical properties and applications ranging from nanoelectronics to sensing and photonics. In addition to graphene, the most studied 2D material, monolayers of other layered materials such as semiconducting dichalcogenides MoS2 or WSe2 are gaining in importance as promising channel materials for field-effect transistors (FETs). The presence of a direct bandgap in monolayer MoS2 due to quantum-mechanical confinement allows room-temperature FETs with an on/off ratio exceeding 108. The presence of high- κ dielectrics in these devices enhanced their mobility, but the mechanisms are not well understood. Here, we report on electrical transport measurements on MoS2 FETs in different dielectric configurations. The dependence of mobility on temperature shows clear evidence of the strong suppression of charged-impurity scattering in dual-gate devices with a top-gate dielectric. At the same time, phonon scattering shows a weaker than expected temperature dependence. High levels of doping achieved in dual-gate devices also allow the observation of a metal–insulator transition in monolayer MoS2 due to strong electron–electron interactions. Our work opens up the way to further improvements in 2D semiconductor performance and introduces MoS2 as an interesting system for studying correlation effects in mesoscopic systems.

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Figure 1: Fabrication of single-gated and dual-gated MoS2 devices.
Figure 2: Electron transport in single-gate monolayer MoS2 supported on SiO2.
Figure 3: Electron transport in dual-gated monolayer MoS2.
Figure 4: Ea for the top-gated monolayer MoS2 in the insulating regime.
Figure 5: Hall-effect measurements in the dual-gated monolayer MoS2 device.

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Acknowledgements

We thank W. Escoffier (LNCMI CNRS), B. Raquet (LNCMI CNRS) and S. Bertolazzi (EPFL) for useful discussions as well as J-S. Heron (EPFL) for technical support. Device fabrication was carried out in part in the EPFL Center for Micro/Nanotechnology (CMI). We thank Z. Benes (CMI) for technical support with electron-beam lithography and A. Radenovic and M. Whitwick (EPFL) for support with ALD deposition. This work was financially supported by ERC grant no. 240076, FLATRONICS: Electronic devices based on nanolayers.

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B.R. worked on device fabrication and performed the measurements. A.K. designed the experiment and initiated the research. B.R. and A.K. analysed the results and wrote the manuscript.

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Correspondence to Andras Kis.

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Radisavljevic, B., Kis, A. Mobility engineering and a metal–insulator transition in monolayer MoS2. Nature Mater 12, 815–820 (2013). https://doi.org/10.1038/nmat3687

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