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

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.