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

The in-plane thermal conductivities of suspended monolayer, bilayer, and multilayer MoS 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 SiO/Si substrate. The measured thermal conductivity (13.3 ± 1.4 W m K) of the suspended monolayer MoS was below the previously reported value of 34.5 ± 4 W m K. 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 MoS films increased in proportion to the number of layers, reaching 43.4 ± 9.1 W m K for the multilayer MoS, which explicitly follows the Fuchs-Sondheimer suppression function. The increase in the thermal conductivity with the number of MoS 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 MoS down to 10 nm in thickness at room temperature, yielding a phonon mean free path of 17 nm for bulk.