Thermal Conduction Across Graphene Cross-Linkers

Controlling the thermal conduction across graphene layers is of great importance for their applications in nanoscale thermal management. However, how to quantitatively control the thermal conduction across the graphene layers is still largely unknown. Here, we performed molecular dynamics simulations to investigate the thermal transport across a junction formed by covalent cross-linkers between two graphene nanoribbons (GNRs). We find that the cross-linkers are effective for transmitting the out-of-plane phonon modes of GNRs, but ineffective for the in-plane modes. Each cross-linker possesses a constant thermal conductance, and there is little thermal coupling between them. Interestingly, the total heat current across the junction is not linearly dependent on the number of cross-linkers; instead, it increases sublinearly initially, and then levels off to about 50% of that of the same size single-layer GNR. A theoretical model is proposed to explain this surprising observation. Our work reveals important new insights into the fundamental principles governing the thermal conduction across chemically cross-linked junctions and provides useful guidelines for the applications of graphene in practical heat management.