Study On The Electronic Structure And Gas Sensing Characteristics Of Nonmetallic Doped Black Phosphorene And Adsorbed Gas

In this paper,the first principle calculation method based on density functional theory is used to systematically study the adsorption characteristics of CO₂,NO₂ and SO₂ molecules on intrinsic（or defective）black phosphene.The gas sensing mechanism of the gas sensor was analyzed by comparing the energy,adsorption parameters,electronic structure and magnetic properties of the most stable adsorption system after optimization,as well as the differential charge density and Bader charge transfer amount.By introducing non-metallic atoms（B,C,N,O,Si,S）doped with black phosphene（or defective black phosphene）to explore the changes in the electronic structure and magnetic properties of black phosphene,and analyze whether non-metallic atoms（N,Si,S）doped with black phosphene（or defective black phosphene）can help improve the adsorption properties of CO₂,NO₂ and SO₂ molecules.The main research content and results of this article are:（1）Intrinsic black phosphorene is a non-magnetic P-type direct bandgap semiconductor;After introducing P atomic defects,the system exhibits ferromagnetic metallic properties due to slight orbital splitting.Firstly,the adsorption of CO₂,NO₂,and SO₂ molecules on intrinsic（or defective）black phosphorene was studied.The results showed that the gas molecules CO₂,NO₂,and SO₂ had smaller adsorption energy,charge transfer,and larger adsorption distance on the intrinsic black phosphorus,exhibiting physical adsorption.After adsorbing NO₂ and SO₂molecules,the energy band of the system significantly decreases,resulting in a significant increase in its adsorption sensitivity;After adsorbing NO₂ molecules,the system undergoes orbital splitting,making the black phosphorus adsorbing NO₂ system magnetic.After adsorbing CO₂ molecules,the energy band of the system remained almost unchanged,indicating that the adsorption sensitivity of black phosphorus to CO₂ molecules was relatively low.The results of the adsorption of gas molecules CO₂,NO₂,and SO₂ on defective black phosphenes indicate that the cleavage of the 3p orbital of the P atom is intensified after the adsorption of CO₂ and SO₂molecules,resulting in a larger magnetic moment in the system.The CO₂ and SO₂ adsorption system transitions from ferromagnetic gold properties to ferromagnetic semiconductor properties.After adsorbing NO₂,the system transforms into ferromagnetic semi metallic properties and the p-orbitals of both P atoms and NO₂ molecules undergo splitting,resulting in an increase in the magnetic moment of the system.Based on the density of states,differential charge density and Bader charge transfer,the internal mechanism of the interaction between gas molecules and the substrate was analyzed.There is a strong coupling effect between the electronic states of CO₂ molecules and the electronic states of P atoms in defective black phosphenes.Therefore,defect treatment of black phosphenes can effectively improve the adsorption sensitivity of CO₂ molecules.（2）For non-metallic atoms（B,C,N,O,Si,and S）doped with black phosphorene,the B,N,O,and S doped systems still exhibit semiconductor properties.Among them,the O and S doped systems exhibit ferromagnetic properties due to the significant cleavage of the p-orbitals of P atoms;The C doped system exhibits non-magnetic metal properties;The Si doping system transforms from a non-magnetic semiconductor to a ferromagnetic metal property.The results show that the electronic structure and magnetic properties of black phosphorene doped with non-metallic atoms can be effectively adjusted.Subsequently,the adsorption of CO₂,NO₂,and SO₂ molecules on N,Si,and S doped black phosphorene was studied.The results showed that NO₂ molecules exhibited significant chemical adsorption on Si doped black phosphorene due to their high adsorption energy,charge transfer,and small adsorption distance;Other doping systems exhibit physical adsorption due to their smaller adsorption energy,charge transfer,and larger adsorption distance.For the N-doped system,after adsorbing NO₂ molecules,the majority of the magnetic moment is provided by NO₂ molecules,which transforms the system from ferromagnetic to semi metallic properties.After adsorbing NO₂ molecules,the Si doped system transitions from ferromagnetic gold properties to non-magnetic semi metallic properties;After adsorbing SO₂ molecules,the spin orbitals of the system are completely symmetrical,leading to the disappearance of magnetism.Among all adsorption systems,the N-doped system has high adsorption sensitivity for NO₂ and SO₂ molecules,and the time required for molecular resolution is also very short.The Si doped system has high adsorption sensitivity to NO₂ molecules and requires a longer time for molecular resolution.In short,the S doped black phosphorene gas sensor has good gas sensitivity to CO₂ molecules;N.Si and S doped black phosphorene gas sensors exhibit good adsorption performance for NO₂ molecules;The N-doped black phosphorene gas sensor has good adsorption performance for SO₂ molecules.（3）Based on the above non-metallic atom doped black phosphorus,we further studied the electronic structure and magnetic properties of non-metallic atom doped defect black phosphorus,as well as the adsorption characteristics of CO₂,NO₂,SO₂ molecules.The results indicate that the flaw-b-C,flaw-s-Si,and flaw-b-S systems exhibit a non-magnetic state due to complete orbital symmetry;Among them,flaw-b-S exhibits semiconductor properties,while the other systems exhibit metallic properties.After the adsorption of gas molecules,the electronic structure and magnetic properties of the system have changed.The flaw-b-Si system undergoes a transition from ferromagnetic metal properties to non-magnetic semiconductor properties after adsorbing CO₂ molecules;The flaw-s-Si system undergoes a transition from metallic to semiconductor properties after adsorbing NO₂ molecules.Similarly,the adsorption of NO₂ molecules on flaw-s-N results in the disappearance of magnetic properties due to the complete symmetry of spin orbitals.The flaw-b-S system has high adsorption sensitivity for CO₂,NO₂,and SO₂,indicating its suitability for the detection of CO₂,NO₂,and SO₂ molecules.Therefore,non-metallic element doped defect black phosphorene is expected to be applied in the sensing and detection of CO₂,NO₂,and SO₂.