High intrinsic lattice thermal conductivity in monolayer MoSi2N4

Very recently, a novel two-dimension (2D) MXene, MoSi₂N₄, was successfully synthesized with excellent ambient stability, high carrier mobility, and moderate band gap (2020 Science 369 670). In this work, the intrinsic lattice thermal conductivity of monolayer MoSi₂N₄ is predicted by solving the phonon Boltzmann transport equation based on the first-principles calculations. Despite the heavy atomic mass of Mo and complex crystal structure, the monolayer MoSi₂N₄ unexpectedly exhibits a quite high lattice thermal conductivity over a wide temperature range between 300 to 800 K. At 300 K, its in-plane lattice thermal conductivity is 224 Wm^-1 K^-1. The detailed analysis indicates that the large group velocities and small anharmonicity are the main reasons for its high lattice thermal conductivity. We also calculate the lattice thermal conductivity of monolayer WSi₂N₄, which is only a little smaller than that of MoSi₂N₄. Our findings suggest that monolayer MoSi₂N₄ and WSi₂N₄ are potential 2D materials for thermal transport in future nano-electronic devices.