Paper published in Nano Letters: “Manipulating thermal conductance at metal-graphene contacts via chemical functionalization”

Our paper, “Manipulating thermal conductance at metal-graphene contacts via chemical functionalization,” was recently published in Nano Letters (Nano Lett. 12, 590 (2012)).  In this work, we use plasma functionalization to manipulate the bonding environment of graphene surfaces.  We metallize the graphene with aluminum, and show that the functionalization can increase the thermal boundary conductance between the Al and the graphene by a factor of two due to change in the bonding enviornment from oxygen functionalization and subsequent Al-O bonding.  This work was performed in collaboration with Thomas Beechem, Ed Barnat and Sean Kearney at Sandia National Laboratories and Scott Walton’s group at the Naval Research Laboratories.

Abstract

Graphene-based devices have garnered tremendous attention due to the unique physical properties arising from this purely two-dimensional carbon sheet leading to tremendous efficiency in the transport of thermal carriers (i.e., phonons). However, it is necessary for this two-dimensional material to be able to efficiently transport heat into the surrounding 3D device architecture in order to fully capitalize on its intrinsic transport capabilities. Therefore, the thermal boundary conductance at graphene interfaces is a critical parameter in the realization of graphene electronics and thermal solutions. In this work, we examine the role of chemical functionalization on the thermal boundary conductance across metal/graphene interfaces. Specifically, we metalize graphene that has been plasma functionalized and then measure the thermal boundary conductance at Al/graphene/SiO₂ contacts with time domain thermoreflectance. The addition of adsorbates to the graphene surfaces are shown to influence the cross plane thermal conductance; this behavior is attributed to changes in the bonding between the metal and the graphene, as both the phonon flux and the vibrational mismatch between the materials are each subject to the interfacial bond strength. These results demonstrate plasma-based functionalization of graphene surfaces is a viable approach to manipulate the thermal boundary conductance.

This work was funded by NSF (CBET Award #1134311)