| AVS 59th Annual International Symposium and Exhibition | |
| Advanced Surface Engineering | Monday Sessions |
| Session SE+NS-MoA |
| Session: | Nanostructured Thin Films and Coatings II: Multifunctional Properties |
| Presenter: | P.V. Braun, University of Illinois at Urbana Champaign |
| Authors: | M.D. Losego, University of Illinois at Urbana Champaign M. Grady, University of Illinois at Urbana Champaign N.R. Sottos, University of Illinois at Urbana Champaign D.G. Cahill, University of Illinois at Urbana Champaign P.V. Braun, University of Illinois at Urbana Champaign |
| Correspondent: | Click to Email |
Compared with our ability to precisely control the flow of electrons or light within a material, our capacity to design the flow of heat, particularly at the nano-scale, is rather rudimentary. For example, billions of microscopic transistors with coordinated electronic transport are routinely fabricated for computers, cell phones, and iPods. In contrast, thermal management is largely limited to macroscopic solutions (e.g. fans, insulation). Examples of confining and controlling heat with precision at micro- or nanometer length scales are relatively rare
Crucial to nanoscale thermal management is an understanding of interfacial heat transport. Interfaces between two materials act as a barrier to heat flow. For nano-scale systems, interfacial heat conduction and not just bulk thermal conductivity is important and possibly dominant in controlling heat transfer. However, thermal transport across interfaces is still not well understood. Historically, differences in bulk acoustic properties and/or phonon densities of states have been used to explain the interfacial thermal boundary resistance. However, more recently, atomic level structural features, such as interfacial roughness and interfacial bonding, have been proposed as contributors to the thermal boundary resistance.
This talk will describe experimental work that attempts to validate recent molecular dynamics (MD) simulations suggesting that interfacial thermal conductance can be strongly modulated by adjusting the strength of interfacial bonds. Our experimental system consists of self-assembled monolayers (SAMs) on SiO2 substrates having either methyl or mercapto terminations. Gold films are transfer printed onto these surfaces forming either a van der Waals or covalent bond respectively. The interfacial thermal conductance across the Au/SAM interface is measured via time-domain thermoreflectance (TDTR) and found to increase by nearly 2x when the interface is switched between a van der Waals interaction and a covalent bond. The interfacial bond stiffness is independently measured using picosecond acoustics. Together these experiments represent the first clear demonstration of how changing the stiffness of a single atomic-scale interfacial bonding layer affects thermal conductance.
To further elucidate the mechanism for this change in interfacial thermal conductance, we will present temperature dependent thermal conductance measurements. This data reveals that high frequency phonon modes cannot traverse interfaces with lower stiffness. Finally, we will show proof-of-concept experimental results that outline a scheme for designing materials with specified values of interfacial thermal conductance.