单晶硅薄膜面向热导率分子动力学研究

采用非平衡分子动力学方法(NEMD)研究了室温(300 K)下厚度为2～32 nm的单晶硅薄膜的沿膜平面方向的热导率,并使用Debye-Einstein模型对模拟温度进行了量子修正。模拟表明薄膜面向热导率小于相应的大体积值,并随膜厚度减小而减小,具有显著的尺寸效应。在模拟范围内膜面向热导率略大于其法向热导率;与声子气动力论的定性结果一致。晶体的表面弛豫和表面重构现象导致了MD模拟中体系总内能的升高。

MOLECULAR DYNAMICAL SIMULATION OF THERMAL CONDUCTIVITY ALONG THE FILM PLANE IN SINGLE-CRYSTAL SILICON FILMS

The thermal conductivity of single crystal silicon films in the direction along the film plane is investigated by the non-equilibrium molecular dynamics (NEMD) method. The Debye-Einstein model is applied in the quantum correction of the simulated local temperature in silicon crystal. This investigation is specified to single crystal silicon films with thickness of 2-32 nm at temperature 300 K. The result reveals the significant size effect that the conductivity of silicon films along the film plane is lower than that value in bulk silicon crystal at corresponding temperature and decreases with the decreasing of film thickness. The conductivity in the direction along the film plane is a little bit larger than that in the direction perpendicular to the film plane. The kinetic theory analysis basis on phonon gas model announces similar conclusion. The surface relaxation and reconstruction are reproduced in the NEMD computational approach, which leads to the increase of system energy during simulation.