Design And Study On The Adsorption Of WSe₂ Gas Doped With Group Ⅴ And Ⅶ Atoms Based On The First Principle

Two dimensional transition metal dichlorides（TMDs）have attracted extensive attention due to their large direct band gap,ultra-thin body,good electron mobility and multifunctional electronic structure.Its adjustable band gap,large specific surface area and high surface activity make it have high research value in the field of gas sensing.As a material under the classification of TMDs,this paper is based on single-layer WSe₂,and the main research contents are as follows:1.Based on the first principle density functional theory,the electronic and structural properties of single-layer WSe₂and its adsorption capacity for different gases were studied.The energy band diagram of single-layer WSe₂is calculated,and the bonding mechanism between W and Se atoms in single-layer WSe₂is analyzed by charge population and charge density diagram.Five gases are selected to determine the optimal adsorption position by changing the adsorption distance and molecular orientation,calculate the adsorption performance of single-layer WSe₂for these gases,and analyze the structural changes and partial density of states of single-layer WSe₂after adsorption.The results show that the single-layer WSe₂has obvious adsorption for SO₂and NO₂,and the adsorption capacity for other gases is weak.2.The electronic structure and properties of V-group atoms doped single-layer WSe₂were studied,and the adsorption energy of doped structure to gas was calculated.The electronic properties of group V atoms doped with P,N and As are calculated.The formation energy results show that a stable As doped single-layer WSe₂cannot be obtained.The energy band diagrams show that the P and N doped structure is a p-type doping.The bonding mechanism between doped atoms and W atoms is analyzed by charge population and differential charge density,and the adsorption response of the two doped structures to gas is calculated.It is found that the adsorption response of the two doped structures to gas is stronger than that of single-layer WSe₂,and the response of P and N doped WSe₂to NO₂gas is significantly greater than that of other gases.The adsorption energy is-1.98 e V and 1.46 e V respectively.From the perspective of bonding type,it is a kind of chemical adsorption.3.The electronic structure and properties of group VII atom doped single-layer WSe₂were studied,and the adsorption energy of doped structure to gas was calculated.The electronic properties of group VII atoms doped with Cl,F and Br are calculated.The results show that the formation energy of Br doped structure is positive.According to the formation energy formula,the formation energy greater than 0 e V cannot remain stable in energy.The energy band diagram shows that Cl and F doped structure is a n-type doping.The charge distribution,differential charge density and adsorption response of Cl and F doped structure to gas are calculated.The results show that the single-layer WSe₂with Cl doped structure is a kind of physical adsorption without bonding to gas,and the adsorption effect of Cl doped structure on NO₂and NH₃is the best.The F doped system is also physical adsorption when adsorbing gas,but it highlights the adsorption effect on SO₂gas.