First Principles Study Of Physicochemical Properties Of Two-Dimensional Materials Modified By Single Atom

In recent years,two-dimensional materials have received intense attention due to their unique physical and chemical properties and their wide application in nanoelectronic devices,spintronic devices,optoelectronic devices,and catalysts.However,in order to obtain better characteristics to meet the needs of practical applications,it is often necessary to physically or chemically regulate the physicochemical properties of the materials.In order to realize practical applications in spintronic devices,it is necessary to introduce magnetic properties therein and to regulate them.Doping,adsorption,introduction of defects,application of strain,etc.can cause non-magnetic two-dimensional materials to be magnetic.Among them,single atom chemical modification and doping have been reported in a large number of studies.From an application point of view,it can significantly regulate its physicochemical properties.From the perspective of basic research,monoatomic modification may bring new interesting physics.We know that most two-dimensional materials are intrinsically non-magnetic.Based on the first-principles calculation of density functional theory,the two new types of InSe and C3 N are respectively determined by single atom doping and adsorption.The electronic properties,magnetic properties,and adsorption activities of the materials have been studied and many interesting results have been found.The main research work and conclusions are as follows:1.We studied the behavior of non-metallic elements hydrogen(H),boron(B),carbon(C),nitrogen(N),oxygen(O),and fluoran(F)adsorbed on a two-dimensional InSe monolayer.Studies have found that adsorption C and F have non-zero magnetic moments and good stability.Importantly,the magnetic properties of the C and F modified InSe monolayers are entirely derived from the p-electrons that adsorb the atoms and the substrate.The strength of the magnetic exchange interaction can be controlled by varying the coverage of the adsorbate.This p-electron magnetic material has significant advantages over conventional d or f electronic magnets.Our research is of great significance for the practical application of spintronics and two-dimensional magnetic semiconductor devices.2.Due to the large atomic spacing in the crystal of the two-dimensional InSe single layer,interstitial doping is possible,which is clearly not possible in graphene and MoS2 and many other two-dimensional materials.Therefore,we used boron atom as an example to study the effect of interstitial doping on the electron and magnetic properties of InSe single layer.For comparison,substitutional doping was also considered,in which B was replaced by B.It is found that the doping method will qualitatively differ in the regulation of magnetic properties.Interstitial doping can induce non-zero magnetic moments,while substitution doping cannot induce magnetism.The doping concentration will produce a quantitative difference in the regulation of magnetism.These results contribute to the design of future InSe-based spintronic devices.3.By studying the bonding strength of VIIIB(Ni,Pd,Pt)and IB(Cu,Ag,Au)metal to C3 N substrate(while considering the graphene substrate as a comparison),it is found that the bonding strength shows obvious regularity.The binding energy of the two groups of metals on the C3 N substrate is larger than that on the graphene substrate.The binding energy of the 5d metal(Au,Pt)is greater than that of the 3d(Cu,Ni)and 4d(Ag,Pd)metals,and the 5d metal performance The most significant dependence on the substrate.By screening the binding energy,we first selected the Pt-loaded C3 N as an example to study its stability,charge state and magnetic properties.It has been found that on graphene,Pt atoms are prone to aggregation,while on C3 N substrates,Pt atoms can always remain separated from each other in a single atomic state.Pt is positively charged on the graphene substrate,whereas Pt is negatively charged on the C3 N substrate.Pt in different charge states will significantly affect the adsorption activity of gas molecules.In addition,it was confirmed that the Pt-modified defective graphene and C3 N have different magnetic properties.The former is paramagnetic;on the contrary,the latter has a non-zero magnetic moment.These results have implications for the design of monoatomic catalysts and spintronic devices.4.Based on the laws found in the above studies,we have also studied the case of Au-loaded C3 N substrates.It is found that,unlike the stability of Pt,Au aggregates on the C3 N substrate to form clusters.In response to this problem,two effective solutions have been proposed,namely: first: introducing defects;second: by unilateral oxygen modification.It is well known that the charge state of Au will significantly affect its catalytic activity.This work shows that defects in the substrate can cause reversal of the charge states of the monoatomic Au(Au+ and Au-),where the defect-induced hole pocket plays a crucial role.Regarding magnetism,studies have shown that Au modification plays a dual role,and the introduction of monoatomic Au can enhance or eliminate the magnetic moment of defective C3 N.This work provides new ideas for experimentally and theoretically stable monoatomic states,and provides theoretical guidance for the design of spintronic devices.