Electronic Structure And Magnetic Properties Of Two Dimensional Zr Based MXenes

Two-dimensional（2D）MXene material is a new type of transition metal carbide or nitride,which has important potential applications in the field of microelectronic devices due to numerious MXenes’types and good material properties.Zr-MXenes with different functionalizations have different electronic properties,which can be tuned by doping and interfacial recombination.This kind of material has the potential applications in nanosacle electromagnetic devices.In this dissertation,the electronic and magnetic properties of 2D Zr-MXenes are mainly investigated by using the first-principles calculation based on density functional theory,and the main results are as follows:Zr₂C monolayer is a magnetic metal,and Zr₂CCl₂monolayers（Zr₂C with Cl functional group）still maintain the metallic property,while its magnetism disappears.The band structure of Zr₂CCl₂-III monolayer shows a Dirac-like cone with a small band gap below Fermi level.The in-plane biaxial strain can tune the electronic properties of Zr₂CCl₂-III monolayer,the electronic structure of Zr₂CCl₂-III moves upward with the increase of compressive strain.The Dirac-like cone in Zr₂CCl₂-III moves to Fermi level at a compression strain of-0.9%,thus Zr₂CCl₂-III monolayer becomes a semiconductor with 7.4 me V band gap.Meanwhile,by considering spin orbit coupling,the band gap of Zr₂CCl₂-III monolayer increases to 32.3 me V.2D Zr₂CT₂（T=F,O）monolayers have various electronic properties,but they are not magnetic.However,2D Zr₇Fe C₄T₈（T=F,O）monolayers formed by doping Fe atom in Zr₈C₄T₈show magnetism and have different properties.Among them,Zr₂CO₂-I is a semiconductor,while Zr₇Fe C₄O₈-I is a magnetic half metal with in-plane magnetic anisotropy（IMA）.Ab initio molecular dynamics simulation proved the stability of Zr₇Fe C₄O₈-I structure.The electronic properties and magnetic anisotropy of Zr₇Fe C₄O₈-I can be tuned by the in-plane biaxial strain.At 6%tensile strain,the magnetic anisotropy of Zr changes from IMA to perpendicular magnetic anisotropy（PMA）.The 2D Zr₂CO₂/H-Fe Cl₂van der Waals（vd W）heterostructure is an indirect semiconductor with a band gap of 0.548 e V,which shows IMA.The in-plane biaxial strain can tune the band gap and interface potential difference of Zr₂CO₂/H-Fe Cl₂heterostructures.In addition,the properties of Zr₂CO₂/H-Fe Cl₂heterostructure can also be tailored by external electric field.Zr₂CO₂/H-Fe Cl₂heterostructure has IMA at negative electric fields,while it has PMA at positive electric fields,which can provide the theoretical basis for its application in low dimensional spintronics devices.