Enhancing interfacial thermal conductance in Si/Diamond heterostructures by phonon bridge

TL;DR

This paper demonstrates that inserting a silicon carbide interlayer in Si/Diamond heterostructures significantly enhances interfacial thermal conductance by facilitating phonon transport, with an optimal thickness around 40 nm.

Contribution

It introduces a phonon bridge mechanism using SiC interlayers and identifies the optimal thickness for maximizing thermal conductance in Si/Diamond heterostructures.

Findings

SiC interlayer increases interfacial thermal conductance by 46.6%.

Optimal SiC interlayer thickness is approximately 40 nm.

SiC is the most effective interlayer material among candidates.

Abstract

This study investigates the mechanism of enhancing interfacial thermal transport performance in Silicon/Diamond (Si/Diamond) heterostructures using the phonon bridge. A heat transfer model for three-layer heterostructures is developed by combining First-principles calculations with the Monte Carlo method. The temperature distribution, spectral heat conductance, and interfacial thermal conductance are compared for Si/Diamond heterostructures with and without a silicon carbide (SiC) interlayer. The results show that the SiC interlayer effectively bridges low-frequency phonons in Si with mid-to-high-frequency phonons in Diamond, which forms a specific phonon bridge, significantly improving interfacial phonon transport. The influence of SiC interlayer thickness is further studied, revealing a size-dependent phonon bridge enhancement. For thin interlayers, intensified phonon boundary scattering weakens the bridging effect. Conversely, excessively thick interlayers increase the bulk thermal resistance, reducing overall interfacial thermal conductance. Thus, an optimal interlayer thickness exists, identified as 40 nm for SiC. Thirteen candidate interlayer materials, including SiC, AlN, {\alpha}-Si3N4, \b{eta}-Si3N4, and AlxGa1-xN (x ranges from 0.1 to 0.9), are compared at various thicknesses. SiC emerges as the most effective interlayer material, increasing interfacial thermal conductance by 46.6% compared to the bilayer heterostructure. AlN ranks second, improving thermal conductance by 21.9%. These findings provide essential insights into the phonon bridge mechanism at heterogeneous interface thermal transport and offer valuable theoretical guidance for designing heterostructures with enhanced thermal transport performance.