单晶硅薄膜法向热导率分子动力学研究

MOLECULAR DYNAMIC SIMULATION ON THE OUT-OF PLANE THERMAL CONDUCTIVITY OF SINGLE-CRYSTAL SILICON THIN FILMS

采用非平衡分子动力学方法（NEMD）研究了平均温度为 500K、厚度为 2～32nm的单晶硅薄膜的法向热导率。模拟结果表明,薄膜热导率显著低于对应温度下的体硅单晶的实验值,并随膜厚度减小以接近线性的规律减小。用声子气动力论模型的分析结果与NEMD模拟相一致,表明纳米单晶硅薄膜中声子平均自由程显著减小。

The nonequilibrium molecular dynamics (NEMD) approach is adapted to simulate the out-of plane thermal conductivity of single crystal silicon films. In the simulation, the thickness of the thin films ranges from 2 to 32 nanometer and the average temperature is 500 K. The simulation results reveal that the out-of plane thermal conductivity of silicon films is significantly lower than that of bulk silicon crystal and decreases almost linearly with the decrement of film thickness. The analytical results of the thermal conductivity based on the kinetic theory of phonon gas model agrees well with the result of NEMD simulation, which indicates that the phonon mean free path in nanoscale silicon films is significantly decreased.