Heat transport in disordered network forming materials: Size effects and existence of propagative modes

Abstract We show that in nanoscale disordered networks the thermal conductivity reduces with respect to the bulk value in a way remindful of the analogous behavior in nanocrystalline systems. Our rationale is based on the analogy with nanostructured crystalline silicon and is substantiated by results obtained (experimentally, analytically and by atomic scale modelling) on crystalline Si, amorphous Si, glassy SiO2 and glassy GeTe4. We point out the implication of such findings on the potential performances of nanoscale heat devices.