The Gas Sensing Performance Of Two-dimensional Borophene/MoS₂ Heterostructure

Since the monitoring and detection of harmful gas is closely related to public health and safety,it has attracted widespread attention in daily life.With the widespread applications of gas sensors,people's demand has gradually increased,and the functional requirements have become more diverse.Because traditional gas sensors have reached their physical limits,people have turned their attention to nano-gas-sensing devices.When choosing materials,in order to achieve excellent performances,nanomaterials could be used to build nano-gas-sensing devices.Excellent gas sensors require high sensitivity,high chemical stability and short response time.Two-dimensional(2D)nanomaterials can be used as candidates for constructing new gas sensors.Borophene is a 2D nanomaterial and has been synthesized on sliver surface recently.The single-layered borophene can be regarded as the lightest 2D metal,and has outstanding electrical conductivity and mechanical properties.Unlike graphene,all boron atoms of borophene are not completely in the same plane,which has strong anisotropy.Due to its superior properties,on the one hand,borophene has been used to design different nanodevices.On the other hand,borophene on the silver surface has greater stability,making it more suitable for practical applications.Nevertheless,there is a major challenge in trying to make nanodevices using the borophene on the silver substrate,i.e.the silver substrate will short-circuit borophene,causing serious problems.For this problem,a better solution is to construct heterostructure.This can increase the stability of borophene and is also an effective method to modify the properties of borophene,for producing ideal functional nanodevices.In order to overcome the short-circuit problem of borophene on the silver surface,the semiconductor MoS₂ was selected as the substrate here to theoretically construct a borophene/MoS₂ heterostructure,and the sensing performances have been discussed.In this paper,using density functional theory,we firstly discussed the adsorption behavior of common inorganic and organic gas molecules on the borophene surface in the borophene/MoS₂ heterostructure,including the adsorption configurations,adsorption energies and electronic properties.The obtained results show that the adsorption types for these molecules can be divided into two categories,namely,chemisorption:CO,NO,NO₂,NH₃,C₂H₂,HCHO and physisorption:CO₂,CH₄,C₂H₄,CH₃OH.In addition,using the non-equilibrium Green's function method,we calculated the transmission properties of the molecules with chemisorption,and analyzed the sensing performances.We found that the 2D heterostructure is very sensitive to NO,C₂H₂ and HCHO molecules.This indicates that the borophene/MoS₂ heterostructure is expected to be an excellent candidate for gas sensors.In the first chapter,we mainly introduced the contents of 2D nanomaterials,the related heterostructures and gas sensors.In the second chapter,we briefly explained the theoretical methods used here.In the third chapter,the obtained results for inorganic gas molecules were discussed,while the related results for organic gas molecules are presented in the fourth chapter.In the fifth chapter,we gave a brief research summary and the perspectives to borophene-based gas sensors.