A molecular dynamics study of the thermal transport in silicon/germanium nanostructures: From cross-plane to in-plane

Thermal transport in silicon/germanium (Si/Ge) nanostructures has been widely studied in both the cross-plane and in-plane configurations. It remains unknown, however, how heat transports in the intermediate configurations. Here we conduct nonequilibrium molecular dynamics simulations to study the thermal conductance of Si/Ge nanostructures that gradually change from a cross-plane to an in-plane configuration. The thermal conductances of the cross-plane and in-plane Si/Ge nanostructures are found to be (1.57 +/- 0.01) x10(8) and (1.60 +/- 0.02) x 10(8) W/m(2)-K respectively at 300 K, both smaller than those of the intermediate nanostructures at the same temperature. As temperature increases, the thermal conductances of the nanostructures decrease, with those of the intermediate nanostructures exhibiting a stronger temperature dependence. The thermal conductances are inconsistent with the trend of the overlap of the vibrational density of states (VDOS) but agree well with the trend of the integrated VDOS in the middle region of the nanostructures.