Effect of Interface Curvature at The Axial Junction in Silicon-Germanium (Si-Ge) Nanowires

Due to a wide array of potential applications, such as thermal management, thin-film technologies, microelectronics, and semiconductor and optical devices, thermal transport in silicon-germanium (Si-Ge) materials, including nanowires, is an area of continued interest. Thermal transport in small-scale heterogeneous systems is controlled by interfacial thermal resistance but the relative contributions of different transport mechanisms (e.g., elastic and inelastic phonon scattering) remain elusive. Our work is expected to further our understanding of phonon thermal transport and the role of boundary scattering at the interfaces of low-dimensional materials. The curvature and sharpness of the interface at the heterojunctions in Si-Ge nanowires depend on their growth environment. Herein, we evaluate the effect of interfacial curvature at the axial junctions in Si-Ge nanowires. We employ the non-equilibrium molecular dynamics (NEMD) Muller-Plathe method (with the Tersoff potential) to model thermal transport in nanowires with lengths between 100 nm and 1.3 μm and varying interfacial curvatures. Boundary resistance is probed for directional transport between both Si and Ge and Ge and Si. We have observed an overall weak dependence of thermal conductivity on curvature, and that the effect of curvature on thermal transport is dependent on nanowire length. The evolution of the wave-packet kinetic energies during the course of a simulation provides a more comprehensive picture of the wave behavior of phonons across the Si-Ge interface.