Thermal boundary conductance across rough interfaces probed by molecular dynamics

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.

Boundary scattering of phonons: Specularity of a randomly rough surface in the small-perturbation limit

“…Many of these studies involve detailed models of a rough surface or interface at the atomic level and use either lattice dynamics calculations based on Green's functions analysis [25][26][27][28][29] or molecular dynamics simulations [32][33][34][35]. These advanced studies heavily rely on numerical computations; hence it is difficult to generalize their results beyond specific systems considered in each particular paper.…”

“…In recent years, a number of advanced and sophisticated models of boundary scattering have been applied to the analysis of thermal transport in nanostructures [25][26][27][28][29][30][31][32][33][34][35]. Many of these studies involve detailed models of a rough surface or interface at the atomic level and use either lattice dynamics calculations based on Green's functions analysis [25][26][27][28][29] or molecular dynamics simulations [32][33][34][35].…”

Phononic thermal resistance due to a finite periodic array of nano-scatterers

“…We observe that the two commonly applied models, the acoustic mismatch model (AMM) and diffuse mismatch model (DMM), do not necessarily lead to values that are comparable to the available experimental data [1,15,17,18]. In all cases, it is clear that the shapes of embedded elements and/or interfaces have an important impact on the TBR [5], [6], [10] [19], [20].…”

“…For silicon,  =2331 kgm -3 , C 11 = 16.57×10 10 Nm -2 and C 44 = 7.956×10 10 Nm -2 [36]. The longitudinal velocity v l and the transverse one v t are defined by the materials properties: We solve numerically Eq.…”

“…Adding carbon nanotubes to the metal/metal interface [3,4], or including self-assembled nanoparticles embedded in the material [5] [6] are some experimental examples that can be used to tune the TBR, as well as chemical etching [7][8][9]. Other strategies have been highlighted, such as the addition of a new material to the solid/solid coupling or modulating the roughness [10]. Lattice dynamics [11,12], Green"s functions [13] and molecular dynamics are often employed for the calculations [14][15][16].…”