Networked nanoconstrictions: An effective route to tuning the thermal transport properties of graphene

Tuning the thermal transport properties of graphene is under intense investigation to achieve novel material functionalities. Here we propose a strategy of networked nanoconstrictions to maintain the ultrahigh thermal conductivity like in design of graphene-based integrated circuits, or to reduce to the minimum for thermoelectrics of energy conversion. By using molecular dynamics simulations, we study the thermal transport behavior in the 18.2-nm-long graphene sheet and firstly report the characteristics of the thermal resistance arising from single-nanoconstriction, inversely proportional to the constriction width and independent of geometry shapes, which agrees well with the derived two-dimensional ballistic resistance model. After the nanoconstrictions are networked, the results elucidate a parallel relationship between ballistic resistances in parallel systems, and especially, a complicated superimposed effect of arrangement mode on ballistic resistances in series systems governed by the phonon localization and corresponding change of phonon transmission angle. Such anomalous phenomenon causes a decrease or further increase in the total ballistic resistance, e.g., tuning the thermal transport property of graphene as much as or more than 96% with specific nanoconstriction networks. We believe this feasible and versatile route will effectively expand potential applications of two-dimensional graphene and also pave the way for three-dimensional materials in the future.