硅纳米薄膜法向热导率的进一步分析

应用非平衡分子动力学方法进一步研究了平均温度为300K、厚度为2.715nm-43.44nm的单晶硅薄膜的法向热导率,模拟结果表明,薄膜热导率低于同温度下单晶硅的实验值,存在显著的尺寸效应,当膜厚度在20nm以下时,法向热导率随尺度减小而线性减小,当膜厚度大于20nm时法向热导率随尺度呈现二阶多项式变化。法向热导率的变化规律与面向热导率的变化规律类似,表明薄膜厚度和表面晶格结构对声子传热影响的复杂性。

FURTHER ANALYSIS ON THE OUT-OF-PLANE THERMAL CONDUCTIVITY MOLECULAR DYNAMICS SIMULATION OF SILICON FILMS AT NANOSCALE

The nonequilibrium molecular dynamics method is adopted to study the out-of-plane thermal conductivity of single crystal silicon films at nanoscale. The average temperature of silicon films is 300 K and the thickness ranges from 2.715 to 43.44 nanometer. The simulation results reveal that the thermal conductivity of silicon film is significantly lower than that of bulk silicon crystal and decreases with the decrease of film thickness. The results indicate that the out-of-plane thermal conductivity linearly increases with film thickness when the film thickness is less than 20 nm and increases in a second-order polynomial increase with scales for the larger thickness region. The variation law of out-of-plane thermal conductivity is similar to variation law of in-plane thermal conductivity, which indicates the complexity of heat transfer of phonon influenced by the film thickness and surface construction influence.