A Molecular Dynamics Study of Silicon Nanowire/Silica Aerogel Nanocomposite Thermal Conductivity

Growing demand for waste heat recycling technology have accelerated research in efficient thermoelectric materials. Because silicon has a large Seebeck coefficient, can be easily doped to be both n-type and p-type and has high Earth abundance, research has focused on methods for reducing the lattice thermal conductivity of this material through nanostructuring techniques. In this work, Reverse Non-Equilibrium Molecular Dynamics (RNEMD) is applied to study the thermal conductivity of silicon-silica aerogel nanocomposites. Embedding the silicon nanowire in an aerogel is found to result in significant reductions to the lattice thermal conductivity of the nanowire when the surface of the nanowire is a major source of phonon scattering. These results can be explained based on the diffuse mismatch model of phonon transport at interfaces and point to a possible path to independently optimize the electronic components of a thermoelectric material from that of its lattice vibration components.