A NEMD STUDY OF THE THERMAL CONDUCTIVITY AND SURFACE ROUGHNESS OF SILICON THIN FILMS

TM Chang and CC Weng and MJ Huang, MicroNano2008-2nd International Conference on Integration and Commercialization of Micro and Nanosystems, Proceedings, 459-465 (2008).

The nonequilibriurn molecular dynamics (NEMD) approach is adopted in this work to calculate the in-plane lattice thermal conductivity of Silicon thin films. In the simulation, the Stillinger-Weber (SW) potential is employed to capture both two-body and three-body interactions. The periodic boundary conditions are applied in the in- plane directions of a thin film. An additional surface potential is added to atoms that a re near the surfaces. This surface potential imposes a force normal to the plane to prevent atoms from evaporation. A constant heat flux is generated by injecting energy into the system somewhere and withdrawing energy somewhere else via the velocity rescaling method. After a sufficiently long simulation time, the time- averaged temperature distribution is calculated and then the thermal conductivity can be obtained by the Fourier's law. When the average temperature of the system is lower than the Debye temperature (theta(D) = 645 K for Si), quantum corrections to both the MID temperature and the thermal conductivity are carried out. To speed up the computation, the present MID tool is parallelized based on a spatial decomposition technique. In this study, we attempt to investigate the relationship among the model parameters of the surface potential, the surface roughness, and the specular reflection fraction at the boundary that is often used in many theoretical studies.

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