Large reduction in thermal conductivity for SiGe alloy nanowire wrapped with a Ge nanoparticle-embedded SiO₂ shell

We demonstrate silicon germanium (SiGe) alloy nanowires (NWs) with Ge nanoparticles (GeNPs) embedded in a SiO₂ shell as a material for decreasing thermal conductivity. During thermal oxidation of SiGe NWs to form SiGe–SiO₂ core–shell structures, Ge atoms were diffused into the SiO₂ shell to relax the strain in the SiGe core, and agglomerated as a few nanometer-sized particles. This structure leads to a large reduction in thermal conductivity due to the GeNP–phonon interaction, while electrical conductivity is sustained because the core of the SiGe alloy NW provides a current path for the charged carriers. The thermal conductivity of the SiGe alloy NWs wrapped with a GeNP-embedded SiO₂ shell is 0.41 W m⁻¹ K⁻¹ at 300 K. (paper)