Resolving the Vibrational and Electronic Contributions to Thermal Conductivity of Silicon Near the Solid-Liquid Transition: Molecular Dynamics Study
Christopher H. Baker, Chenping Wu, Richard N. Salaway, Leonid V. Zhigilei and Pamela M. Norris
Although thermal transport in silicon is dominated by phonons in the solid state, electrons also participate as the system approaches, and exceeds, its melting point. Thus, the contribution from both phonons and electrons must be considered in any model for the thermal conductivity of silicon near the melting point. In this work, the phononic contribution to the bulk thermal conductivity of silicon is determined for the Stillinger-Weber potential in equilibrium and non-equilibrium molecular dynamics simulations for temperatures ranging from 1400 K to 2000 K . It is found that, although the contribution of electron-hole pair diffusion to high temperature conductivity of solid silicon is not included in classical molecular dynamics simulations, the Stillinger-Weber potential overestimates the vibrational contribution to thermal conductivity and, incidentally, reproduces quite well the total thermal conductivity of the solid phase up to the melting temperature. As for the liquid phase conductivity, the Stillinger-Weber potential agrees with theoretical treatment of the phononic thermal transport and predicts a minor phononic contribution of about 3% to the total liquid phase thermal conductivity. Thus, atomistic modeling of thermal transport in liquid phase silicon must include a description of the electronic contribution, e.g., through a combination of the molecular dynamics method with the continuum treatment of the electronic thermal conductivity within the two-temperature model.
Keywords: Molecular dynamics simulation, silicon, high temperature, thermal conductivity.