Interfacial thermal resistance across graphene/Al2O3 and graphene/metal interfaces and post-annealing effects

Abstract

Chemical vapor deposited (CVD) graphene together with a superior gate dielectric such as Al2O3, are promising materials for next-generation high-speed field-effect transistors. Using the differential 3ω method, we have characterized the interfacial thermal resistance (ITR) across CVD graphene/Al2O3 and graphene/metal (Al, Ti, Au) interfaces from 100 to 330 K and investigated the effects of post-annealing on the interfacial thermal coupling for effective thermal management of those graphene-based devices. It was found that the ITR of graphene/Al2O3 is almost 5 times higher than the literature values for graphene/SiO2 interfaces while ITRs for graphene/metal, however, are much lower than that of graphene/Al2O3. It was also observed that ITR for graphene/Ti interface could be reduced by up to 40% through post-annealing. This reduction is attributed to the annealing-induced Ti-C covalent bonding on the interfaces. To explain the discrepancy between the experiments and conventional ITR models, we proposed a modified Diffuse Mismatch Model considering the interface coupling strength, which implies that the phonon transmission at the graphene interfaces is generally poor while annealing-induced bonding can improve the transmission. This work shows a scalable and inexpensive technique to improve graphene/metal thermal contacts.