Effect of morphology on the phonon thermal conductivity in Si/Ge superlattice nanowires

We used nonequilibrium molecular dynamics to investigate the role of morphology in the phonon thermal conductivity of 〈100〉, 〈110〉, 〈111〉 and 〈112〉-oriented Si/Ge superlattice nanowires at 300 K. Such nanowires with 〈112〉 growth direction were found to possess the lowest values of the thermal conductivity [1.6 W/(m·K) for a Si and Ge segment thickness of ∼3 nm] due to the lowest average group velocity and highly effective {113} facets and Si/Ge(112) interface for phonon-surface and phonon-interface scattering, respectively. Comparison with homogeneous and core/shell Si and Ge nanowires showed that the superlattice morphology is the most efficient to suppress the thermal conductivity.