Biaxila strain modulated high anisotropic gas-sensing performance of C 5 N-based two-dimensional devices: A first-principles study

Two-dimensional carbon nitride materials have been widely used in many applications such as device fabrication, gas adsorption and separation due to their abundant element resources, high physicochemical stability and excellent electronic properties. In this paper, density functional theory and non-equilibrium Green ' s function method are used to study the electronic structure, transport characteristics and gas sensitivity of C 5 N-based structures. The results show that the electron transport exhibits obvious anisotropy, in which the electron transport in the armchair direction is more conductive than that in the zigzag direction. It is worth noting that the negative differential resistance effect exists in both directions. Furthermore, the transport and sensing characteristics of inorganic molecules (NO, CO, NO 2 , SO 2 , and NH 3 ) adsorbed on the C 5 N monolayer are studied. The results show that CO, SO 2 and NH 3 exist on the surface of C 5 N in the form of physical adsorption, while NO and NO 2 adhere to the surface of C 5 N in the form of chemical adsorption. The designed C 5 N gas sensor exhibits high sensitivity to NO and NO 2 molecules, reaching 81 % sensitivity to NO 2 at a 0.1 V bias voltage. Finally, the effect of strain on the adsorption properties of gas sensing devices is studied. Studies have shown that the application of -4 % strain in the armchair direction significantly increases the current of NO and NO 2 , significantly improving the performance of the gas sensor. Whether strain is applied to the device or gas adsorption, C 5 N materials always maintain significant anisotropy. This study shows that C 5 N is a highly anisotropic and sensitive two-dimensional material, which has broad application potential in the field of electronic properties and gas sensing.