Enhanced Thermal Conduction Through Nanostructured Interfaces

Abstract

Interfaces dominate heat conduction in nanostructured systems, and much work has focused on methods to enhance interfacial conduction. These approaches generally address planar interfaces, where the heat flux vector is everywhere normal to the interface. Here, we explore a nanostructured interface geometry that uses nonplanar features to enhance the effective interfacial conductance beyond what is possible with planar interfaces. This interface consists of interdigitating Al pillars embedded within SiO 2 with characteristic feature size ranging from 100 nm to 800 nm. The total sidewall surface area is modulated to highlight the impact of this additional channel by changing the pillar-to-pillar pitch ! between 1.6 µm and 200 nm while maintaining the same Al:SiO 2 fill fraction. Using optical pump-probe thermoreflectance measurements, we show that the effective conductance of a ~65 nm thick fin layer monotonically increases with decreasing ! , and that the conductance for ! = 200 nm is more than twice the prediction for a layered stack with the same volume ratio and a planar interface. Through a combination of Boltzmann transport modeling and finite element calculations, we explore the impact of the pitch ! and the pillar aspect ratio on effective thermal conductance. This analysis suggests that the concept of nanostructured interfaces can be extended to interfaces between diffusive and quasi-ballistic media in highly scaled devices. Our work proposes that the controlled texturing of interfaces can facilitate interfacial conduction beyond the planar interface regime, opening new avenues for thermal management at the nanoscale.

A Review of Experimental and Computational Advances in Thermal Boundary Conductance and Nanoscale Thermal Transport across Solid Interfaces

“…Experimental works have demonstrated that nonplanar features of nanofabricated fin‐like projections with characteristic length scales of ≈100 nm can substantially increase the interfacial heat flow through an increase in the overall contact area . Similarly, MD studies have also shown that these types of features (even down to sub‐nanometer length scales) can be used to achieve an increase in h K .…”

“…Kapitza conductance is extremely dependent on the structural details of the interface at the nanoscale since the characteristic dimensions are comparable to or less than the vibrational mean‐free paths. Nanostructuring at the interface has been efficiently used to tune the energy transport pathways across interfacial regions either by introducing roughness, nonplanar features, interface mixing, or by functionalizing the interface to alter the stiffness of the bonds …”

“…Kapitza conductance is extremely dependent on the structural details of the interface at the nanoscale since the characteristic dimensions are comparable to or less than the vibrational mean-free paths. Nanostructuring at the interface has been efficiently used to tune the energy transport pathways across interfacial regions either by introducing roughness, [78,90,137,138] nonplanar features, [139][140][141] interface mixing, [137,142] or by functionalizing the interface to alter the stiffness of the bonds. [143][144][145][146][147][148][149][150][151] Experimental works have demonstrated that nonplanar features of nanofabricated fin-like projections with characteristic length scales of ≈100 nm can substantially increase the interfacial heat flow through an increase in the overall contact area.…”

“…[143][144][145][146][147][148][149][150][151] Experimental works have demonstrated that nonplanar features of nanofabricated fin-like projections with characteristic length scales of ≈100 nm can substantially increase the interfacial heat flow through an increase in the overall contact area. [139,140] Similarly, MD studies have also shown that these types of features (even down to sub-nanometer length scales) can be used to achieve an increase in h K . [78,141,152] This idea of nanopillars that increase the area for heat flow is analogous to the implementation of macroscale fin arrays used to increase the contact area of solids with the fluid environment.…”

Ab initio and nuclear inelastic scattering studies of Fe3Si/GaAs heterostructures

“…Other effects related to finite sizes and reduced dimensionality also influence atomic vibrations [16]. These modifications of lattice dynamics in nanosystems lead to new phenomena such as phonon folding [17], phonon localization and confinement [18][19][20] as well as coherent and enhanced heat con- * e-mail: olga.sikora@ifj.edu.pl ductivity [21][22][23]. Further studies on these effects may pave the way to phonon engineering [24,25] and efficient thermal management in nanoscale devices [26,27].…”