Modifying Surface Energy of Graphene via Plasma-Based Chemical Functionalization to Tune Thermal and Electrical Transport at Metal Interfaces

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 (ρ_C). Conversely, functionalization with fluorine has no impact on h_K, yet ρ_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.