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Van der Waals epitaxy of tunable moirés enabled by alloying

Nature Materials volume 23, pages 339–346 (2024)Cite this article

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Abstract

The unique physics in moiré superlattices of twisted or lattice-mismatched atomic layers holds great promise for future quantum technologies. However, twisted configurations are thermodynamically unfavourable, making accurate twist angle control during growth implausible. While rotationally aligned, lattice-mismatched moirés such as WSe2/WS2 can be synthesized, they lack the critical moiré period tunability, and their formation mechanisms are not well understood. Here, we report the thermodynamically driven van der Waals epitaxy of moirés with a tunable period from 10 to 45 nanometres, using lattice mismatch engineering in two WSSe layers with adjustable chalcogen ratios. Contrary to conventional epitaxy, where lattice-mismatch-induced stress hinders high-quality growth, we reveal the key role of bulk stress in moiré formation and its unique interplay with edge stress in shaping the moiré growth modes. Moreover, the superlattices display tunable interlayer excitons and moiré intralayer excitons. Our studies unveil the epitaxial science of moiré synthesis and lay the foundations for moiré-based technologies.

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Fig. 1: Growth of moiré vdW heterostructures.
Fig. 2: Tunable moiré pattern in WSySe2–y/WSxSe2–x vdW HSs.
Fig. 3: Moiré growth mechanisms.
Fig. 4: Moiré uniformity.
Fig. 5: Excitons in grown moiré vdW HSs.

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Data availability

Source data are provided with this paper. Other supporting data and very large files are available from the corresponding authors upon reasonable request.

Code availability

The codes that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

STEM images were collected by A. Penn. M.F.-D. acknowledges support from the Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de Recherche du Québec (FRQNT). M.F.-D. and F.X. acknowledge the partial support from the Government of Israel and Yale University. K.W. and T.T. acknowledge support from Japan Society for the Promotion of Science KAKENHI (grant nos 19H05790, 20H00354 and 21H05233).

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Authors and Affiliations

  1. Department of Electrical Engineering, Yale University, New Haven, CT, USA

    Matthieu Fortin-Deschênes & Fengnian Xia

  2. Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan

    Kenji Watanabe

  3. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan

    Takashi Taniguchi

Authors
  1. Matthieu Fortin-Deschênes
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  2. Kenji Watanabe
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  3. Takashi Taniguchi
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  4. Fengnian Xia
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Contributions

M.F.-D. conceived and carried out the experiments and simulations. M.F.-D. and F.X. analysed the results and wrote the manuscript. K.W. and T.T. synthesized the hBN crystals.

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Correspondence to Matthieu Fortin-Deschênes or Fengnian Xia.

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Nature Materials thanks Lain-Jong Li, David Geohegan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–17 and Discussion.

Source data

Source Data Fig. 2

Plot of moiré lattice parameter versus ΔSe.

Source Data Fig. 3

Simulation results.

Source Data Fig. 4

Histograms.

Source Data Fig. 5

PL data.

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Fortin-Deschênes, M., Watanabe, K., Taniguchi, T. et al. Van der Waals epitaxy of tunable moirés enabled by alloying. Nat. Mater. 23, 339–346 (2024). https://doi.org/10.1038/s41563-023-01596-z

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