Tuning thermal conductance across sintered silicon interface by local nanostructures

Abstract

A large reduction of heat conduction through silicon-silicon sintered interface by local oxide nanostructures is quantitatively demonstrated by a newly developed method to directly measure thermal boundary conductance across bonded interfaces. Together with the theoretical analysis that relates the thermal boundary conductance to thermal conductivity of densely-packed bulk nanocrystalline silicon, we identify a route to significantly reduce the thermal conductivity from the state-of-art value, even to approach the amorphous silicon value. The finding is useful for designing nanostructured bulk silicon thermoelectrics

Effects of defects on thermoelectric properties of carbon nanotubes

“…Since electron contribution to thermoelectric properties is determined by Θ(E) as shown in Eqs. (2)- (7), the change in Θ(E) due to defects are discussed here. Figure 3 shows Θ(E) of 100-nm CNTs for (a) vacancies and (b) SW defects with σ varying from 0.0% (blue line) to 0.1% (red line) with the equal interval of σ (corresponding to Ndef = 0 to 9).…”

Ultimate Confinement of Phonon Propagation in Silicon Nanocrystalline Structure

“…In this sense, Casimir limit is no longer an appropriate reference since it does not account for frequency dependent phonon transmission/reflection at the interface that can be strongly altered by the interfacial structures. Thermal transport across a sintered Si-Si interface has been investigated by Sakata et al 14 , and SiOx nano-precipitates formed at the interface were found to give rise to an order-of-magnitude controllability. Hence, there is a room to further reduce thermal conductivity by nanometer sized grains and precisely controlled interfaces, however, sintering, being a high energy process, has limitation due to the grain growth and interfacial diffusion/mixing.…”

Effective phonon mean free path in polycrystalline nanostructures

“…29 The value of c is determined so as to match model and experiment for the thermal boundary conductance, G, which is a measurable quantity for instance by the time domain thermoreflectance method. 42 From the Landauer formula, G can be expressed as 25,43 …”

“…Using the measured thermal boundary conductance of sintered silicon interfaces ranging from around 100 to 1000 MWm À2 K À1 depending on the sintering conditions, 42 we obtain the lower and upper bounds of c, 2.40 and 26.8.…”