A First-principles Study On The Electronic Structure Of Ti, V, Co, Ni Doped Two-dimensional CrSi₂ Materials

Two-dimensional materials have shown excellent optical,mechanical thermal or magnetic properties,and have promising applications in the high performance electronic,optical,spintronic devices and energy transfer and energy storage,etc.Monolayer transition metal silicide CrSi₂has shown ferromagnetism and metal properties in previous studies,and is expected to become a new two-dimensional material.Ti,V,Co,Ni doped two-dimensional CrSi₂were researched with different doping concentration by using the VASP software,and electronic structure,magnetic and optical properties were calculated and analyzed.The electronic structures,phonon spectrum,magnetic and optical properties of intrinsic CrSi₂were calculated,and the results show that the intrinsic two-dimensional CrSi₂has no lattice wave in the negative frequency range after calculating the phonon spectrum,which proves that the structure of two-dimensional CrSi₂is stable at the temperature of absolutely zero.The density of states in the two-dimensional CrSi₂system is asymmetric,and the crystal cells have obvious ferromagnetism with a magnetic moment of3.55?B.The density of states near the Fermi level in the two-dimensional CrSi₂system is mainly composed of Cr-3d orbital electrons.The contribution of Cr-3p electrons and Si-3p electrons to the total state density of the system is limited.The magnetic moment is mainly derived from the Cr-3d orbital electrons in the spin-up state.Two-dimensional CrSi₂has strong absorptivity and reflectivity in the far infrared and ultraviolet range,showing excellent optical properties.The electronic structures and magnetic properties of Ti-,V-,Co-or Ni-doped CrSi₂with different concentrations were calculated and analyzed,and the results show that the magnetic moment of the two-dimensional CrSi₂varies after doping different elements at the doping concentration of 11.1 at%.After doping Ti,the magnetic moment of the system changes to 0?B at the doping concentration of 11.1 at%,showing an indirect semiconductor.After doping V,the magnetic moment becomes smaller at the doping concentration of 11.1 at%,and the system has two degrees of freedom:electron charge and spin,showing the properties of diluted magnetic semiconductors.After doping Ni,the band gap E_g=0.09 e V appears in the spin-up band of the system at the doping concentration of 11.1 at%,while the spin-down band is metallic,and the system shows semi-metallic properties.The magnetic moment changes to 3.71?B after doping Ti at the doping concentration of 22.2 at%.After doping Co and Ni,the magnetic moment of the system becomes smaller at the doping concentration of 22.2at%,and the spin-down 3d orbital electrons of ferromagnetic elements take the dominant position.After doping Ni,the magnetic moment becomes0.37?B at the doping concentration of 22.2 at%.After doping Ti,the magnetic moment becomes 2.79?B at the doping concentration of 33.3 at%,after doping V,the magnetic moment becomes 2.27?B,and the degree of spin becomes weaker at the doping concentration of 33.3 at%.After doping Co,the magnetic moment becomes 1.81?B at the doping concentration of33.3 at%.The magnetic moment becomes 1.5?B after doping Ni at the doping concentration of 33.3 at%,which proves that the spin-up d orbital has less electronic contributes to the magnetic moment.The energy band range of each system is enlarged,and the interaction between atoms is enlarged,and the energy level splitting energy is enlarged at the doping concentration of 33.3 at%,which indicates that the effective mass of the system becomes smaller,the mobility of carriers becomes stronger,and the metallization of materials becomes stronger.The optical properties of Ti-,V-,Co-or Ni-doped CrSi₂with different concentrations were calculated and analyzed,and the results show that the two-dimensional CrSi₂before and after doping systems have good optical properties.The optical properties of most systems increase and blue shift at the doping concentration of 11.1 at%and 22.2 at%,but the absorption peak has red shift at the doping concentration of 33.3 at%.By studying the properties of doped two-dimensional CrSi₂,it is found that the two-dimensional CrSi₂has excellent electronic structure and optical properties,and the electronic structure,magnetic and optical properties of the two-dimensional CrSi₂can be effectively changed by doping.Two-dimensional CrSi₂is expected to be a promising material for preparing new high reliability and high stability spintronic devices,and the research provides effective theoretical basis for developing the devices based on the two-dimensional CrSi₂.