Thickness-dependent in-plane thermal conductivity of suspended MoS2 grown by chemical vapor deposition

Abstract

The in-plane thermal conductivities of suspended monolayer, bilayer, and multilayer MoS₂ films were measured in vacuum by using non-invasive Raman spectroscopy. The samples were prepared by chemical vapor deposition (CVD) and transferred onto preformed cavities on a Au-coated SiO₂/Si substrate. The measured thermal conductivity (13.3 ± 1.4 W m⁻¹ K⁻¹) of the suspended monolayer MoS₂ was below the previously reported value of 34.5 ± 4 W m⁻¹ K⁻¹. We demonstrate that this discrepancy arises from the experimental conditions that differ from vacuum conditions and small absorbance. The measured in-plane thermal conductivity of the suspended MoS₂ films increased in proportion to the number of layers, reaching 43.4 ± 9.1 W m⁻¹ K⁻¹ for the multilayer MoS₂, which explicitly follows the Fuchs–Sondheimer suppression function. The increase in the thermal conductivity with the number of MoS₂ layers is explained by the reduced phonon boundary scattering. We also observe that the Fuchs–Sondheimer model works for the thickness-dependent thermal conductivity of MoS₂ down to 10 nm in thickness at room temperature, yielding a phonon mean free path of 17 nm for bulk.