Abstract
The effects of divacancy, including isolated defects and extended line defects (ELD), on the thermal transport properties of graphene nanoribbons (GNRs) are investigated using the Nonequilibrium Green’s function method. Different divacancy defects can effectively tune the thermal transport of GNRs and the thermal conductance is significantly reduced. The phonon scattering of a single divacancy is mostly at high frequencies while the phonon scattering at low frequencies is also strong for randomly distributed multiple divacancies. The collective effect of impurity scattering and boundary scattering is discussed, which makes the defect scattering vary with the boundary condition. The effect on thermal transport properties of a divacancy is also shown to be closely related to the cross section of the defect, the internal structure and the bonding strength inside the defect. Both low frequency and high frequency phonons are scattered by 48, d5d7 and t5t7 ELD. However, the 585 ELD has almost no influence on phonon scattering at low frequency region, resulting in the thermal conductance of GNRs with 585 ELD being 50% higher than that of randomly distributed 585 defects. All these results are valuable for the design and manufacture of graphene nanodevices.
Highlights
Due to its excellent mechanical, electrical and thermal properties, graphene has broad application prospects in many fields [1,2,3,4,5]
We find that when the extended line defects (ELD) is perpendicular to the transport direction, it will greatly reduce the thermal conductance of the graphene nanoribbons (GNRs), resulting in a decrease of about 33% to 47% of the total, the results are in accordance with the previous work [55], where the largest decline are caused by the d5d7 and t5t7 ELDs
We find that the thermal conductance of GNRs can be greatly reduced by divacancy defects, the influence of divacancies on the thermal transport properties of AGNRs is greater than that of ZGNRs, and the scattering of phonons when a divacancy is in the center region of GNR is stronger than that at the ribbon edge
Summary
Due to its excellent mechanical, electrical and thermal properties, graphene has broad application prospects in many fields [1,2,3,4,5]. It is important to study the effect of divacancies on the performance of graphene. It has been found that divacancies can affect the mechanical [12,13,14,15], electrical [16,17,18], magnetic [19,20] and chemical [21,22] properties of graphene. Some of these effects can provide some useful performance qualities. In order to take advantage and employ divacancies, we will intentionally introduce them into graphene
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