Thermal boundary conductance across rough interfaces probed by molecular dynamics

TL;DR

This study investigates how interfacial roughness affects thermal boundary conductance using molecular dynamics, revealing a transition between regimes and highlighting the importance of interface shape and asperity angle for nanoscale heat transport optimization.

Contribution

The paper provides new insights into the impact of interfacial roughness and shape on thermal boundary conductance, emphasizing the transition between conductance regimes and the role of interface geometry.

Findings

Boundary conductance is constant for small roughness, close to planar interface conductance.

Larger roughness increases conductance proportionally to interfacial area.

Rough interface conductance significantly influences superlattice heat transport.

Abstract

In this article, we report the influence of the interfacial roughness on the thermal boundary conductance between two crystals, using molecular dynamics. We show evidence of a transition between two regimes, depending on the interfacial roughness: when the roughness is small, the boundary conductance is constant taking values close to the conductance of the corresponding planar interface. When the roughness is larger, the conductance becomes larger than the planar interface conductance, and the relative increase is found to be close to the increase of the interfacial area. The cross-plane conductivity of a superlattice with rough interfaces is found to increase in a comparable amount, suggesting that heat transport in superlattices is mainly controlled by the boundary conductance. These observations are interpreted using the wave characteristics of the energy carriers. We characterize also the effect of the angle of the asperities, and find that the boundary conductance displayed by interfaces having steep slopes may become important if the lateral period characterizing the interfacial profile is large enough. Finally, we consider the effect of the shape of the interfaces, and show that the sinusoidal interface displays the highest conductance, because of its large true interfacial area. All these considerations are relevant to the optimization of nanoscale interfacial energy transport.