Remarkable thermal conductivity reduction in metal-semiconductor nanocomposites

Abstract

Remarkable reduction in thermal conductivity, by ∼2 orders of magnitude compared to the bulk counterpart, is observed in a metal-semiconductor nanocomposite consisting of silver (Ag) and silicon (Si) nanostructures. The variation of thermal conductivity with temperature and with volume fraction of metallic inclusion exhibits counter-intuitive behavior. Contrary to bulk composites, thermal conductivity decreases with the increase in the volume fraction of Ag nanocrystals (at least till 0.067 experimented) and increases with temperature over the range of 303-473 K. This remarkable reduction in the thermal conductivity of the nanocomposite is due to the interplay of size-dependent reduction in thermal conductivity of the individual nanostructures, increased contribution of phonon scattering at the interfaces between nanoparticles, and electron-phonon coupling inside metallic nanocrystals and across metal-semiconductor interface. Such hybrid metal-semiconductor nanostructures with reduced thermal conductivity offer immense potential for developing high efficiency thermoelectric materials.