On the role of the interface in the mechanical and electronic properties of BCN monolayers

BCN monolayers are heterostructures composed of graphene and hexagonal boron nitride (h-BN) connected in-plane by covalent bonds. Previous research revealed that altering the proportion of graphene and h-BN enables the control of the resulting material's properties. However, less attention has been devoted to the role of the bonds that constitute the interface. In this work, we employ Density Functional Theory calculations to investigate the interface. We first characterize the force response of the CC, BN, CN, and BC bond types that comprise the material. Our results reveal that the CB bond is the weakest of the four, leading us to design monolayers with and without CB bonds. Results from stress-strain calculations show that removing the CB bond increases the material's stiffness. On the other hand, the ultimate strength of the BCN monolayer with a modified interface increased or decreased depending on the elongation direction, as stress can become concentrated in the stiff CN bonds. Regarding the electronic properties, the composition changes at the interface shifted the Fermi energy, transforming the hybrid structure from a semiconductor to a metal. This work shows the importance of the bond types at the graphene/h-BN interface to the mechanical and electronic properties of the resulting BCN monolayer, revealing another tool that can be employed to manipulate the properties of two-dimensional materials.