The dual role of interlayer crosslinks leads to an abnormal behavior of interlayer thermal resistance in multilayer graphene

Abstract

Understanding and controlling the interlayer thermal resistance (ITR) are crucial to the cross-plane thermal transport in multilayer graphene (MLG). Using non-equilibrium molecular dynamics simulations, we show that the ITR of MLG can be effectively tuned by in-plane defects, sp2 and sp3 C–C bond crosslinks. Specifically, with the increase of the in-plane defect density, the ITR initially increases sharply and then almost saturates; while with the increase of the crosslink density, the ITR initially also increases sharply, then peaks and subsequently decreases rapidly to a level that can be even lower than that of pristine MLG. The underlying mechanism for this unexpected variation of ITR with crosslink density is explored through the analyses of the phonon density of states (DOS) and spectral transmission function. It was found that the crosslinks play a dual role: the crosslink-generated in-plane defect enhances phonon scattering and leads to an increase in the ITR, while the interlayer bonding gives rise to a fast phonon transmission pathway and decreases the ITR. An effective medium approximation (EMA) model was proposed to describe the dual role of the crosslinks. This work provides new insight into the thermal transport behavior of crosslinks, which is useful for modulating the cross-plane thermal transport of MLG for the thermal management of MLG-based nanodevices.