Two Novel Semiconducting B2co Monolayers With High Carrier Mobilities

The design of new two-dimensional (2D) materials with moderate band gaps and high carrier mobility is an important aspiration for materials innovation. Recent studies have shown that boron and oxygen atoms can be integrated into the graphene lattice to form a stable B-C-O monolayer structure. To search for the most energetically stable configuration for 2D B-C-O, here, we theoretically propose two new 2D B-C-O crystal structures with a stoichiometric ratio of 2:1:1, namely monolayer (1 L) C-3v- and C-2v-B2CO. Two configurations have 0.09 and 0.03 eV/unit cell lower energies than the reported 1 L C-s-B2CO configuration (Nanoscale 2016, 8, 8910). This result is further confirmed by particle swarm optimization (PSO) calculations. According to the chemical bonding analysis, 1 L C-3v-B2CO with a quasi-planar configuration has the lowest energy, which is consisted of three strong B '-O sigma-bonds, three B ''-C sigma-bonds, and one B '-C sigma-bond. As a result, 2D B2CO has an ultra-high mechanical strength of similar to 366 J m(-2), comparable to graphene similar to 352 J m(-2). In addition, 1 L C-3v-B2CO is a semiconductor with an HSE06 bandgap of 2.57 eV, and it has a high electron mobility of up to similar to 150 cm(2) v(-1) s(-1). The high kinetic and thermodynamic stabilities of both 1 L C-3v- and C-2v-B2CO were confirmed according to phonon dispersion and molecular dynamic simulation. Comparable to that of crystalline silicon, 1 L C-3v-B2CO also shows a high light absorption intensity in the 400-550 nm region. Therefore, 2D C-3v-B2CO will have promising applications in semiconductor devices and photodetectors.