High gas sensing performance of inorganic and organic molecule sensing devices based on the BC₃N₂ monolayer

Recently, a novel two-dimensional (2D) BC₃N₂ monolayer has gained a lot of attention due to its graphene-like structure, and it was first reported by using the particle swarm optimization algorithm and ab initio calculations. Combining density functional theory with the non-equilibrium Green's function method, a 2D BC₃N₂-based nanodevice has been theoretically constructed and the gas sensing performance of the BC₃N₂ monolayer for inorganic and organic molecules has been extensively investigated. The results revealed that the BC₃N₂ monolayer remains metallic with thermodynamic stability. Meanwhile, the results of sensing performance analysis show that the inorganic molecules CO, NO, and NO₂ and organic molecules C₂H₂ and HCHO have strong chemical interactions with BC₃N₂ and were chemically adsorbed onto BC₃N₂. In contrast, the interactions between NH₃, SO₂, CH₄, C₂H₄ and CH₃OH and BC₃N₂ are very weak and these molecules adopt physical adsorption. In the case of chemisorption, the electronic transport behaviors of the 2D BC₃N₂ devices are sensitive to molecules, and the gas sensitivity of BC₃N₂ is strongly anisotropic, especially for organic C₂H₂ with the gas sensing ratios from 7.30 to 10.43 (from 2.51 to 2.79) under different bias voltages along the zigzag (armchair) direction. For inorganic molecules, the gas sensing device is not particularly sensitive, and the maximum gas sensing ratio is only 1.36 for CO. Meanwhile, the large anisotropic gas sensitivity can reach up to 2.66/6.22 for electron transport along the armchair and zigzag directions for CO/C₂H₂ in the BC₃N₂-based sensing devices. Accordingly, the high gas sensitivity can be disclosed by displaying the scattering state around the Fermi level at different bias voltages during the transport process. As a result, BC₃N₂ could be used in 2D gas sensing devices, especially for sensing organic molecule C₂H₂.