Electronic Structure Of Two-Dimensional Semiconductor Phosphorene And Antimonene

Black phosphorene and antimonene,two-dimensional VI group elements semiconductors,have attained much attention after graphene and transition metal dichalcogenides.Phosphorene can be applied in nanoelectronics devices based on its direct band gap and high carrier mobility.Antimonene has a band gap of 2.0 eV,which has potential applications in optoelectronic devices working at blue or UV light and mechanical sensors.It is important to study the electronic structure of novel two-dimensional materials modified by doping and interface recombination.In this dissertation,the electronic structure of phosphorene doped by nonmagnetic atoms?B,C,N,O,F,S,Se?,phosphorene/CrO₂ interface,antimonene doped by 3d-transition metal atoms?Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu Zn?,antimonene with vacancy,and antimonene/Co interface are studied by using density functional theory.The electronic structure and magnetic properties of monolayer phosphorene doped by nonmagnetic atoms are studied.O,S and Se impurities induce the magnetism.O dopant makes phosphorene become a spingapless semiconductor,but S and Se induce a half-metallic characteristic.B acts as an n-type dopant and F results in a p-type semiconductor.C induces a metallic characteristic and N has little effect on phosphorene.The magnetism of phosphorene doped by two O atoms strongly depends on the doping sites and distance between two O atoms.The electronic structure and magnetic properties of the phosphorene/CrO₂?001?interface are investigated.The charge transfers from phosphorene into CrO₂ at the interface.Furthermore,the p-type conduction of phosphorene appears with Fermi level shifting down and crossing the valence maximum of CrO₂/phosphorene.At the interface,the phosphorene preserves its original band structure and CrO₂ preserves its half-metallic characteristic.The electronic structure and magnetic properties of antimonene doped by3d-transition metal are calculated using spin-polarized first-principles calculations.Strong orbital hybridization exhibits between 3d-transition metal d and Sb p ortitals.Sc-doped system is the most stable one.Ti,V,Cr,Mn and Fe result in the magnetism.Cr-doped antimonene becomes the spin-polarized semiconductor,while half-metallic characteristic appears by doping Ti,V and Mn.Meanwhile,Sc and Co-doped systems still preserve its semiconductor characteristic.The geometry,electronic structure and spin splitting in antimonene with monovacancy?MV?and divacancy?DV?are studied using first-principles calculations.Different vacancies influence the electronic properties and cause different geometric structures with or without inversion symmetry.MV antimonene shows a metallic characteristic.However,four DV antimnoene models preserve the semiconducting characteristic except for narrowing the band gap.The inversion asymmetry and spin-orbit coupling lead to the spin splitting in MV and two DV models.The geometry,electronic structure and magnetic properties of the antimonene/Co?0001?interfaces with monolayer,bilayer and trilayer antimonene are investigated.The Co d,Sb s and p orbitals show a strong hybridization near Fermi level,and strong chemical bonds form between Co and Sb atoms at the interface.Antimonene shows a spin polarization of 12%at the 1H interface.After the contact,a high Schottky barrier forms and the barrier height can be tuned by different Co/antimonene stacking patterns.With the increased number of layers of antimonene,the barrier height decreases.