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Molybdenum disulfide transistors with enlarged van der Waals gaps at their dielectric interface via oxygen accumulation

Nature Electronics volume 5, pages 849–858 (2022)Cite this article

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Abstract

Two-dimensional molybdenum disulfide (MoS2) is a potential alternative channel material to silicon for future scaled transistors. Scaling down the gate dielectric and maintaining a high-quality interface is challenging with such materials, because the atomic thickness of MoS2 makes it sensitive to defects common in amorphous gate oxides such as hafnium oxide (HfOx). Here we show that a van der Waals gap of 5.3 Å can be formed between HfOx and MoS2 via the ozone treatment of a hafnium disulfide (HfS2)/MoS2 stack. The ozone treatment converts the HfS2 flake into a HfOx dielectric, and excess oxygen accumulation at the interface widens the van der Waals gap. Experimental results and density functional theory calculations show that the increased gap decouples the interaction between the HfOx dielectric and MoS2 channel, allowing the intrinsic properties of the MoS2 semiconductor to be preserved. The resulting MoS2 van der Waals-gap-gated transistors exhibit a negligible hysteresis of 10 mV and average subthreshold slope of 63.1 mV dec−1, which is close to the physical Boltzmann limit of 60.0 mV dec−1. We also show that the transistors can be used to construct NOT, OR and AND logic gates.

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Fig. 1: Schematic and vdW gap at the dielectric/channel interface.
Fig. 2: DFT results of the contact structures after melt-and-quench simulation.
Fig. 3: Electrical performance of top-gate MoS2 VGG transistors.
Fig. 4: Stability of MoS2 VGG transistors.
Fig. 5: Logic gates made with MoS2 VGG transistors.

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Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors on reasonable request.

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Acknowledgements

This work was supported by the National Key Research and Development Program of Ministry of Science and Technology (no. 2018YFA0703700), China National Funds for Distinguished Young Scientists (grant 61925403), China National Funds for Outstanding Young Scientists (grant 62122024), the National Natural Science Foundation of China (grant nos. 62274060, 12174094, 51872084 and 51991341) and Natural Science Foundation of Hunan Province (grant nos. 2021JJ20028 and 2020JJ1002), and partly by the Key Research and Development Plan of Hunan Province (grant nos. 2022WK2001 and 2018GK2064).

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Authors and Affiliations

  1. Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha, China

    Pengfei Luo, Chang Liu, Jun Lin, Xinpei Duan, Wujun Zhang, Chao Ma, Yawei Lv, Xuming Zou, Yuan Liu, Wenjing Qin, Lei Liao & Xingqiang Liu

  2. State Key Laboratory for Chemo/Biosensing and Chemometrics, College of Semiconductors (College of Integrated Circuits), Hunan University, Changsha, China

    Pengfei Luo, Xuming Zou, Lei Liao & Xingqiang Liu

  3. FG Mikro- und Nanoelektronische Systeme, Institut für Mikro- und Nanoelektronik, TU Ilmenau, Ilmenau, Germany

    Frank Schwierz

  4. School of Physics and Electronics, Key Laboratory for Matter Microstructure and Function of Hunan Province, Key Laboratory of Low-dimensional Quantum Structures and Quantum Control, Hunan Normal University, Changsha, China

    Wenjing Qin

  5. Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan, China

    Jun He

  6. School of Physics, Henan Normal University, Xinxiang, China

    Xingqiang Liu

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  1. Pengfei Luo
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Contributions

P.L. and C.L. contributed equally to this work. L.L. and X.L. conceived and designed the experiments. P.L. fabricated the VGG transistors, measured the electrical performance and prepared the manuscript. C.L. and J.L. designed the schematic and prepared the TEM samples. X.D. completed the current–voltage measurements. W.Q. finished the Raman measurements and MD simulations. W.Z. completed the TEM analysis using the protocols provided by C.M. Y.Lv. provided the DFT analysis. X.Z., Y.Liu., F.S. and J.H. presented the suggestions for improving the quality of this work and revised the manuscript. All the authors examined and commented on the manuscript.

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Correspondence to Wenjing Qin, Lei Liao, Jun He or Xingqiang Liu.

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Nature Electronics thanks Theresia Knobloch and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Luo, P., Liu, C., Lin, J. et al. Molybdenum disulfide transistors with enlarged van der Waals gaps at their dielectric interface via oxygen accumulation. Nat Electron 5, 849–858 (2022). https://doi.org/10.1038/s41928-022-00877-w

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