Multilayer Graphene-Based Thermal Rectifier with Interlayer Gradient Functionalization

As a counterpart of electrical and optical diodes with asymmetric transmission properties, the nanoscale thermal rectifier has attracted huge attention. Graphene has been expected as the most promising candidate for the design and fabrication of high-performance thermal rectifiers. However, most reported graphene-based thermal rectification has been achieved only within the plane of the graphene layer, and the efficiency is heavily limited by the lateral size, restricting the potential applications. In this paper, we propose a design of multilayer graphene-based thermal rectifier (MGTR) with interlayer gradient functionalization. A unique thermal rectification along the vertical direction without lateral size limitation is demonstrated by molecular dynamics simulations. The heat flux prefers to transport from a fully hydrogenated graphene layer to a pristine graphene layer. The analysis of phonon density of states reveals that the mismatch between dominant frequency domains plays a crucial role in the vertical thermal rectification phenomenon. The impacts of temperature and strain on the rectification efficiency are systematically investigated, and we verify the interlayer welding process as an effective approach to eliminate the degradation induced by out-of-plane compression. In addition, compared with uniform hydrogenation at average H-coverage, an anomalous enhancement of in-plane thermal conductivity of multilayer graphene with interlayer gradient hydrogenation is observed. The proposed MGTR has great potential in designing devices for heat management and logic control.