Tunable Thermal Conductivity of Two-Dimensional SiC Nanosheets by Grain Boundaries: Implications for the Thermo-Mechanical Sensor

Two-dimensional SiC has been successfully prepared in an experiment (Phys. Rev. Lett 2023, 130, 076203), which provides new material candidates for power devices. In this work, molecular dynamics simulations are employed to investigate the tunable thermal transport properties of the SiC monolayer by grain boundaries (GBs). The thermal conductivity of SiC shows a pronounced dependence on the number and angle of the GBs interfaces. The inherent pentagon-heptagon structure at GBs induces atomic forces between atoms at the GBs, leading to a certain out-of-plane displacement of these atoms at the interface. Appropriate external strain can flatten the GB interface, thereby enhancing the thermal conductivity. However, further increasing the strain will decrease the thermal conductivity due to enhanced phonon anharmonicity. Moreover, the interface thermal conductance at the GBs also exhibits obvious dependence on the angle of GBs and temperature, which is explained by the atomic stress at the GBs interface. Furthermore, using phonon packet analysis, we found that the phonon interface scattering at GBs differs from that in the two-dimensional heterostructure. This finding reveals the intrinsic thermo-mechanical coupling mechanism governing thermal conduction in two-dimensional SiC, also suggesting its application in thermal management in the thermo-mechanical sensor.