Thermal conductivity modeling of periodic two-dimensional nanocomposites

In this paper, the phonon Boltzmann equation model is established to study the phonon thermal conductivity of nanocomposites with nanowires embedded in a host semiconductor material. Special attention has been paid to cell--cell interaction using periodic boundary conditions. The simulation shows that the temperature profiles in nanocomposites are very different from those in conventional composites due to ballistic phonon transport at nanoscale. Such temperature profiles cannot be captured by existing models in literature. The general approach is applied to study silicon wire/germanium matrix nanocomposites. We predict the thermal conductivity dependence on the size of the nanowires and the volumetric fraction of the constituent materials. At constant volumetric fraction the smaller the wire diameter, the smaller is the thermal conductivity of periodic two-dimensional nanocomposites. For fixed silicon wire dimension, the lower the atomic percentage of germanium, the lower the thermal conductivity of the nanocomposites. Comparison is also made with the thermal conductivity of superlattices. The results of this study can be used to direct the development of high efficiency thermoelectric materials.