Tunable Thermal Anisotropy Triggered by Quasi-Ballistic Heat Transport in WS2Crystals
We investigate the influence of temperature and film thickness on the anisotropic thermal conductivity tensor of multilayer single-crystal WS<inf>2</inf>films of varying thickness (10 nm to 2.8 μm) across a wide temperature range (80–473 K). Experiments show that both in-plane (k<inf&...
| Autores: | , , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:dnet:digitalcsic_::c3128821c54eb8df816f6abe647dc9c3 |
| Acceso en línea: | http://hdl.handle.net/10261/431921 https://api.elsevier.com/content/abstract/scopus_id/105020756134 |
| Access Level: | acceso abierto |
| Palabra clave: | Frequency-domain thermoreflectance Phonon transport Thermal conductivity anisotropy WS2 |
| Sumario: | We investigate the influence of temperature and film thickness on the anisotropic thermal conductivity tensor of multilayer single-crystal WS<inf>2</inf>films of varying thickness (10 nm to 2.8 μm) across a wide temperature range (80–473 K). Experiments show that both in-plane (k<inf>r</inf>) and out-of-plane (k<inf>z</inf>) thermal conductivities increase with decreasing temperature, reaching, at 80 K in bulk WS<inf>2</inf>, values up to k<inf>r</inf>∼ 1000 W m<sup>–1</sup>K<sup>–1</sup>and k<inf>z</inf>∼ 13 W m<sup>–1</sup>K<sup>–1</sup>. The thermal anisotropy ratio η = k<inf>r</inf>/k<inf>z</inf>in bulk rises dramatically from 30 to 78 as the temperature decreases from 460 to 80 K, driven by the suppression of k<inf>z</inf>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 k<inf>z</inf>. 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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