Mechanical and thermal properties of grain boundary in a planar heterostructure of graphene and hexagonal boron nitride

Abstract

In this study, the mechanical properties of grain boundaries (GBs) in planar heterostructures of graphene and hexagonal boron nitride (h-BN) were studied using the molecular dynamics method in combination with the density functional theory and classical disclination theory. The hybrid interface between graphene and h-BN grains was optimally matched by a non-bisector GB composed of pentagon-heptagon defects arranged in a periodic manner. GB was found to be a vulnerable spot to initiate failure under uniaxial tension; moreover, the tensile strength was found to anomalously increase with an increase in the mismatch angle between graphene and h-BN grains, i.e., the density of pentagon-heptagon defects along the GBs. The disclination theory was successfully adopted to predict the stress field caused by lattice mismatch at the GB. Comparison between stress contours of GBs with different mismatch angles demonstrates that the arrangement of 5-7 disclinations along the GB is crucial to the strength, and the stress concentration at the GB decreases with an increase in disclination density; this results in an anomalous increase of strength with an increase in the mismatch angle of grains. Moreover, the thermal transfer efficiency of the hybrid GB was revealed to be dependent not only on the mismatch angle of grains but also on the direction of the thermal flux. Thermal transfer efficiency from graphene to h-BN is higher than that from h-BN to graphene. Detailed analyses for the phonon density of states (PDOS) of GB atoms were carried out for the mismatch angle-dependence of interfacial conductance. Our results provide useful insights for the application of two-dimensional polycrystalline heterostructures in next-generation electronic nanodevices.

An insight into thermal properties of BC3-graphene hetero-nanosheets: a molecular dynamics study

“…Li et al . 29 reported a similar nonlinearity in temperature profile for graphene-boron nitride heterostructure having 5–7 defects along the grain boundaries. In another MD simulation, Mayelifartash et al 39 reported a temperature drop at the C3N and BC3 nanosheets interface in the hybrid C 3 N-BC 3 nanosheets.…”

“…In this regard, several theoretical studies attempted to predict the thermal properties of the heterostructure nanosheets. For example, Li et al 29 studied the thermal properties of heterostructure nanosheet composed of graphene and hexagonal BN using molecular dynamics (MD) simulation. They modeled several graphene-BN heterostructures having grain boundaries with various defect densities of heptagons and pentagons.…”

Robustness of topological insulating phase against vacancy, vacancy cluster, and grain boundary bulk defects

“…The VA size distribution for two scenarios clearly shows that the averaged cluster size in the system with VCs is larger than that with VA alone, which contains predominantly the mono-VAs [29]. Two typical symmetrical GBs in honeycomb lattice with misorientation angles 21.8° (GBI) and 32.2° (GBII) [29,[44][45][46][47][48][49] were constructed and a pair of GB dipoles were induced to resume periodic boundary condition (PBC) as needed.…”

Temperature Dependence of Interfacial Bonding and Configuration Transition in Graphene/Hexagonal Boron Nitride Containing Grain Boundaries and Functional Groups

“…In addition, a certain number of topological defects inevitably occur in the process of material synthesis due to polymorphism and different bonding geometry in planar heterostructures [22,23]. These topological defects affect the physical and material properties of planar heterostructures [24,25].…”