Thermal conductivity of 2D diamond superstructures in interlayer-bonded twisted bilayer graphene

We report results from a systematic analysis of thermal transport in 2D diamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) based on molecular-dynamics simulations. We find that the introduction of interlayer C–C bonds in these bilayer structures causes an abrupt drop in the thermal conductivity of pristine, non-interlayer-bonded bilayer graphene, while further increase in the interlayer C–C bond density (2D diamond fraction) leads to a monotonic increase in the thermal conductivity of the resulting superstructures with increasing 2D diamond fraction toward the high thermal conductivity of 2D diamond (diamane). We also find that a similar trend is exhibited in the thermal conductivity of interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) as a function of interlayer C–C bond density, but with the thermal conductivity of the IB-TBG 2D diamond superstructures consistently exceeding that of RD-IBGs at a given interlayer bond density. We analyze the simulation results employing effective medium and percolation theories and explain the predicted thermal conductivity dependence on interlayer bond density on the basis of lattice distortions induced in the bilayer structures as a result of interlayer bonding. Our findings demonstrate that the thermal conductivity of IB-TBG 2D diamond superstructures and RD-IBGs can be precisely tuned by controlling interlayer C–C bond density and have important implications for the thermal management applications of interlayer-bonded few-layer graphene derivatives.