Regulation of thermal conductivity of bilayer graphene nanoribbon through interlayer covalent bond and tensile strain

Abstract

The interlayer bonding of graphene is a method of modifying graphene, which can change the mechanical property and conductivity of graphene, but also affect its thermal properties. In this paper, the non-equilibrium molecular dynamics method is used to study the thermal conductivity of bilayer graphene nanoribbon which is local carbon sp³ hybridization (covalent bond formed between layers) under different concentration and angle of interlayer covalent bond chain and different tensile strain. The mechanism of the change of the thermal conductivity of bilayer graphene nanoribbon is analyzed through the density of phonon states. The results are as follows. The thermal conductivity of bilayer graphene nanoribbon decreases with the increase of the interlayer covalent bond concentration due to the intensification of phonon scattering and the reduction of phonon group velocities and effective phonon mean free path. Moreover, the decrease rate of thermal conductivity depends on the distribution angle of covalent bond chain. With the increase of interlayer covalent bond concentration, when the interlayer covalent bond chain is parallel to the direction of heat flow, the thermal conductivity decreases slowest because the heat transfer channel along the heat flow direction is gradually affected; when the interlayer covalent bond chain is at an angle with respect to the direction of heat flow, the thermal conductivity decreases more rapidly, and the larger the angle, the faster the thermal conductivity decreases. The rapid decline of thermal conductivity is due to the formation of interfacial thermal resistance at the interlayer covalent bond chain, where strong phonon-interface scattering occurs. In addition, it is found that the thermal conductivity of bilayer graphene nanoribbon with interlayer bonding will be further reduced by tensile strain due to the intensification of phonon scattering and the reduction of phonon group velocity. The results show that the thermal conductivity of bilayer graphene nanoribbon can be controlled by interlayer bonding and tensile strain. These conclusions are of great significance in designing and thermally controlling of graphene based nanodevices.