Plasma-based chemical functionalization of graphene independently controls both electrical and thermal interface resistances – Congrats Brian Foley for this publication in Nano Letters!

We have demonstrated the ability to independently control the electrical contract resistance and thermal boundary resistance at Au/graphene interfaces by functionalizing the graphene via an atmospheric plasma-based approach.   The modification of surface energy either oxygen, nitrogen or fluorine adsorbates leads to varying interactions at the Au/graphene interface.  Where the bonding at this interface affects thermal transport, the change in surface energy and resulting electrical interactions lead to modifications in electrical transport.  This work, in which Brian Foley was first author, was recently published in Nano Letters (Nano Letters 15, 4876-4882 (2015)), and was in collaboration with Dr. Scott Walton from the Naval Research Labs.

Abstract

The high mobility exhibited by both supported and suspended graphene, as well as its large in-plane thermal conductivity, has generated much excitement across a variety of applications. As exciting as these properties are, one of the principal issues inhibiting the development of graphene technologies pertains to difficulties in engineering high-quality metal contacts on graphene. As device dimensions decrease, the thermal and electrical resistance at the metal/graphene interface plays a dominant role in degrading overall performance. Here we demonstrate the use of a low energy, electron-beam plasma to functionalize graphene with oxygen, fluorine, and nitrogen groups, as a method to tune the thermal and electrical transport properties across gold-single layer graphene (Au/SLG) interfaces. We find that while oxygen and nitrogen groups improve the thermal boundary conductance (h_K) at the interface, their presence impairs electrical transport leading to increased contact resistance (rho_C). Conversely, functionalization with fluorine has no impact on h_K, yet rho_C decreases with increasing coverage densities. These findings indicate exciting possibilities using plasma-based chemical functionalization to tailor the thermal and electrical transport properties of metal/2D material contacts.

Acknowledgements

P.E.H. appreciates funding from the Office of Naval Research Young Investigator Program (N00014-13-4-0528). B.M.F is grateful for support from the Army Research Office (W911NF- 13-1-0378) and the ARCS Foundation Metro Washington Chapter. This work was partially supported by the Naval Research Laboratory Base Program. This work was performed in part at the Center for Atomic, Molecular, and Optical Science(CAMOS) at the University of Virginia.

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