Kapitza conductance of symmetric tilt grain boundaries in graphene
AJ Cao and JM Qu, JOURNAL OF APPLIED PHYSICS, 111, 053529 (2012).
Non-equilibrium molecular dynamics simulations were employed to study the Kapitza conductance of symmetric tilt grain boundaries in the monolayer graphene sheet. Both armchair and zig-zag oriented bicrystal graphene were investigated. The Kapitza conductance of the interface shows length dependence up to 300 nm, which arises from the fact that long-wavelength phonons allowed in large-size graphene are able to transmit through the interface contributing to the Kapitza conductance. The Kapitza conductance exhibits monotonic increase with temperature, opposite to the trend of thermal conductivity of bulk graphene above room temperature. We found that the Kapitza conductance is inversely proportional to the number of dislocations per length of grain boundaries. The facts that the phonon density of states (DOS) shows no difference between the two crystals separated by the grain boundary and the vibrational DOS of grain boundary region atoms deviates from that of bulk atoms reveal that the interfacial thermal resistance arises from the structure defects, causing additional phonon scattering for the mismatched phonon spectrum of defects. The predicted length-independent Kapitza conductance ranges from 19 to 47GW/Km(2), which is larger than that of any other interfaces reported in the literature. Finally, theoretical analysis was carried out to explain why the thermal resistance scales with the number of defects per unit length. (C) 2012 American Institute of Physics. http://dx.doi.org/10.1063/1.3692078
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