Published April 10, 2024 | Version v1
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Van der Waals epitaxy of Weyl-semimetal T d -WTe 2

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Epitaxial growth of WTe2 offers significant advantages, including the production of high-qualityfilms, 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 fewtens 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) graphenereaching a mean flake size of ≃110nm, which is, on overage, more than three time larger thanprevious results. WTe2 films thicker than 5nm have been successfully synthesized and exhibit theexpected Td-phase atomic structure. We rationalize epitaxial growth of Td-WTe2 and propose asimple model to estimate the mean flake size as a function of growth parameters that can be appliedto other transition metal dichalcogenides (TMDCs). Based on nucleation theory and Kolmogorov-Johnson-Meh-Avrami (KJMA) equation, our analytical model supports experimental data showinga critical coverage of 0.13ML above which WTe2 nucleation becomes negligible. The quality ofmonolayer WTe2 films is demonstrated from electronic band structure analysis using angle-resolved photoemission spectroscopy (ARPES) in agreement with first-principle calculationsperformed on free-standing WTe2 and previous reports.

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https://hal.science/hal-04542981
URN
urn:oai:HAL:hal-04542981v1

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UNICA