First-principles analysis of phonon thermal transport properties of two-dimensional WS<sub>2</sub>/WSe<sub>2</sub> heterostructures*
Zheng Chang, Kunpeng Yuan, Zhehao Sun, Xiaoliang Zhang, Yufei Gao, X. G. Gong, Dawei Tang
Abstract
The van der Waals (vdW) heterostructures of bilayer transition metal dichalcogenide obtained by vertically stacking have drawn increasing attention for their enormous potential applications in semiconductors and insulators. Here, by using the first-principles calculations and the phonon Boltzmann transport equation (BTE), we studied the phonon transport properties of WS 2 /WSe 2 bilayer heterostructures (WS 2 /WSe 2 -BHs). The lattice thermal conductivity of the ideal WS 2 /WSe 2 -BHs crystals at room temperature (RT) was 62.98 W/mK, which was clearly lower than the average lattice thermal conductivity of WS 2 and WSe 2 single layers. Another interesting finding is that the optical branches below 4.73 THz and acoustic branches have powerful coupling, mainly dominating the lattice thermal conductivity. Further, we also noticed that the phonon mean free path (MFP) of the WS 2 /WSe 2 -BHs (233 nm) was remarkably attenuated by the free-standing monolayer WS 2 (526 nm) and WSe 2 (1720 nm), leading to a small significant size effect of the WS 2 /WSe 2 -BHs. Our results systematically demonstrate the low optical and acoustic phonon modes-dominated phonon thermal transport in heterostructures and give a few important guidelines for the synthesis of van der Waals heterostructures with excellent phonon transport properties.