Thermal conductivity of fivefold twinned silicon-germanium heteronanowires

Abstract

The thermal transport properties of five-fold twinned (5FT) germanium–silicon (Ge–Si) heteronanowires (h-NWs) with varying cross-sectional areas, germanium (Ge) domain ratios and heterostructural patterns are investigated using homogeneous nonequilibrium molecular dynamics (HNEMD) simulations. The results demonstrate a distinctive behavior in the thermal conductivity (κ) of 5FT-NWs, characterized by a “flipped” trend at a critical cross-sectional area. This behavior is attributed to the hydrodynamic phonon flow, arising from the normal three-phonon scattering process in the low-frequency region. In addition, the composition ratio of 5FT-NWs has a significant impact on reducing the κ of 5FT-NWs and suppressing the hydrodynamic effect. Intriguingly, as the homogeneous element domains are separated, stronger phonon hydrodynamic flows are observed in comparison to the adjacent homogeneous element domains. By analyzing various phonon properties, including phonon dispersion, three-phonon scattering rate, and phonon mean free path, critical insights into the origin of the differential κ in different 5FT-NW structures are provided. The findings deepen the understanding of the thermal transport properties of nanomaterials and hold implications for the design and development of nanoelectronics and thermoelectric devices.