Modeling electronic, mechanical, optical and thermal properties of graphene-like BC$_6$N materials: Role of prominent BN-bonds

Abstract

We model monolayer graphene-like materials with BC$_6$N stoichiometry where the bonding between the B and the N atoms plays an important role for their physical and chemical properties. Two types of BC$_6$N are found based on the BN bonds: In the presence of BN bonds, an even number of $π$-bonds emerges indicating an aromatic structure and a large direct bandgap appears, while in the absence of BN bonds, an anti-aromatic structure with an odd-number of $π$-bonds is found resulting a direct small bandgap. The stress-strain curves shows high elastic moduli and tensile strength of the structures with BN-bonds, compared to structures without BN-bonds. Self-consistent field calculations demonstrate that BC$_6$N with BN-bonds is energetically more stable than structures without BN-bonds due to a strong binding energy between the B and the N atoms, while their phonon dispersion displays that BC$_6$N without BN-bonds has more dynamical stability. Furthermore, all the BC$_6$N structures considered show a large absorption of electromagnetic radiation with polarization parallel to the monolayers in the visible range. Finer detail of the absorption depend on the actual structures of the layers. A higher electronic thermal conductivity and specific heat are seen in BC$_6$N systems caused by hot carrier--assisted charge transport. This opens up a possible optimization for bolometric applications of graphene based material devices.