Tunable Thermal Anisotropy Triggered by Quasi-Ballistic Heat Transport in WS Crystals
We investigate the influence of temperature and film thickness on the anisotropic thermal conductivity tensor of multilayer single-crystal WS2 films of varying thickness (10 nm to 2.8 μm) across a wide temperature range (80-473 K). Experiments show that both in-plane (kr) and out-of-plane (kz) therm...
| Autores: | , , , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Autònoma de Barcelona |
| Repositorio: | Dipòsit Digital de Documents de la UAB |
| Idioma: | inglés |
| OAI Identifier: | oai:dnet:uabarcelona_::22a32ce4b4e7ae253b812b53d573420e |
| Acceso en línea: | https://ddd.uab.cat/record/327512 https://dx.doi.org/urn:doi:10.1021/acs.nanolett.5c04514 |
| Access Level: | acceso abierto |
| Palabra clave: | Phonon transport Thermal conductivity anisotropy Frequency-domain thermoreflectance WS |
| Sumario: | We investigate the influence of temperature and film thickness on the anisotropic thermal conductivity tensor of multilayer single-crystal WS2 films of varying thickness (10 nm to 2.8 μm) across a wide temperature range (80-473 K). Experiments show that both in-plane (kr) and out-of-plane (kz) thermal conductivities increase with decreasing temperature, reaching, at 80 K in bulk WS2, values up to kr ∼ 1000 W m-1 K-1 and kz ∼ 13 W m-1 K-1. The thermal anisotropy ratio η = kr/kz in bulk rises dramatically from 30 to 78 as the temperature decreases from 460 to 80 K, driven by the suppression of kz due to phonon transport entering the quasi-ballistic regime. We further analyze the cumulative thermal conductivity as a function of phonon mean free path (MFP), showing that phonons with MFPs < 200 nm contribute to 70% of the total kz. This work provides fundamental insight into the interplay between dimensionality, temperature, and anisotropic phonon transport in two-dimensional materials, where thermal anisotropy can be strategically leveraged for performance optimization. |
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