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Journal Articles ACS Applied Materials & Interfaces Year : 2024

Van der Waals epitaxy of Weyl-semimetal Td-WTe2

Bertrand Kierren
Geoffroy Kremer
François Bertran
Yannick Fagot-Revurat

Abstract

Epitaxial growth of WTe2 offers significant advantages, including the production of high-quality films, possible long range in-plane ordering and precise control over layer thicknesses. However, the mean island size of WTe2 grown by molecular beam epitaxy (MBE) in litterature is only a few tens of nanometers, which is not suitable for an implementation of devices at large lateral scales. Here we report the growth of Td -WTe2 ultrathin films by MBE on monolayer (ML) graphene reaching a mean flake size of ≃110nm, which is, on overage, more than three time larger than previous results. WTe2 films thicker than 5nm have been successfully synthesized and exhibit the expected Td-phase atomic structure. We rationalize epitaxial growth of Td-WTe2 and propose a simple model to estimate the mean flake size as a function of growth parameters that can be applied to other transition metal dichalcogenides (TMDCs). Based on nucleation theory and Kolmogorov-Johnson-Meh-Avrami (KJMA) equation, our analytical model supports experimental data showing a critical coverage of 0.13ML above which WTe2 nucleation becomes negligible. The quality of monolayer WTe2 films is demonstrated from electronic band structure analysis using angle-resolved photoemission spectroscopy (ARPES) in agreement with first-principle calculations performed on free-standing WTe2 and previous reports.
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Dates and versions

hal-04542981 , version 1 (12-04-2024)

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Alexandre Llopez, Frédéric Leroy, Calvin Tagne-Kaegom, Boris Croes, Adrien Michon, et al.. Van der Waals epitaxy of Weyl-semimetal Td-WTe2. ACS Applied Materials & Interfaces, 2024, 16 (16), pp.20878-20885. ⟨10.1021/acsami.4c00676⟩. ⟨hal-04542981⟩
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