Thermal Conductivity of Monolayer MoSe2 and MoS2

Two-dimensional (2D) MoSe2 and MoS2 monolayers, two prototype transition metal dichalcogenides (TMDCs) materials, have attracted growing interest as promising 2D semiconductors. In this work, thermal conductivity (kappa) of the monolayer MoSe2 is computed using largescale classical nonequilibrium molecular dynamics (NEMD) simulations for the first time. The predicted kappa. of monolayer MoSe2 with infinite length (or MoSe2 2D sheets) are 43.88 +/- 1.33 and 41.63 +/- 0.66 W/(m.K) in armchair and zigzag directions, respectively. These simulation results are further confirmed by independent simulations using the Green-Kubo method (GKM), which yield computed kappa of 44.38 +/- 2.08 and 44.63 +/- 2.50 W/(m.K), respectively. For 2D MoS2 sheet, the computed ic based on the NEMD method are 101.43 +/- 1.13 and 110.30 +/- 2.07 W/(m.K), respectively, in armchair and zigzag directions, whereas those based the GKM are 102.32 +/- 6.05 and 108.74 +/- 6.68 W/(m.K), respectively. The predicted kappa values of MoS2 monolayer are 2 times larger than those of MoSe2 monolayer. Both types of 2D monolayers exhibit isotropic properties in thermal conduction. Effects of system dimensions, heat flux, and temperature on x are investigated comprehensively. The predicted kappa. value increases monotonically with the system length but decreases with temperature.