Effects Of Surface Regulation And Substrate On Two-dimensional Materials Of Pnictogens

With the development of human society,microelectronic technology is approaching its‘limit'by the increasing demand of information.Therefore,searching for new alternative materials is the focus of current research in materials science,and the two-dimensional crystalline materials,thanks to their superior electrical characteristics,are considered as the future direction of new semiconductor materials research.In this thesis,using first principle calculations based on the density functional theory?DFT?,we investigate the effects of surface regulation and substrate on two-dimensional materials of pnictogens,and hoping that these studies would provide theoretical support for future experimental research on such materials.The main results are as follows:1.A systematic study has been carried out to investigate the structure,the electronic property,and the stability of full hydrogenated and fully halogenated?F,Cl,Br,I?arsenene and antimonene.We find that arsenene and antimonene transform wide band gap semiconductors into Dirac materials after fully hydrogenated and fully halogenated,and the Dirac cone is located at K point in first Brillouin zone.Furthermore,the obtained Dirac cones in these system are?-type Dirac cone formed by s,p_x and p_y orbits of As?Sb?atoms,which is different form the?-type Dirac cone formed by pz orbit in graphene.Stability studies show that both full hydrogenated and fully halogenated arsenene and antimonene are highly stable.The Dirac cones in these systems will lead to high carrier mobility,which may have important applications in electronic devices.2.A systematic study has been carried out to investigate the structure,electronic property and stability of two types of systems:the semi-hydrogenated semi-halogenated arsenene and antimonene?H-As-F,H-Sb-F?,and the fully hydrogenated or fully fluorinated AsP,SbAs and BiSb.We find that in these systems is no Dirac cone but a band gap at the Fermi surface because of the destruction of the spatial inversion symmetry,thus the systems turn from wide band gap semiconductors into narrow direct-gap semiconductors.The energy band near the K points,however,still have good linear dispersion.Stability studies show that fF-AsP,fH-SbAs,fF-SbAs,fH-BiSb,and fF-BiSb are highly stable.These five materials,plausibly with high carrier mobility,could be synthesized in experiment,and applied in electronic devices.3.A systematic study has been carried out to investigate the structure,electronic property and stability of arsenene,antimonene and bismuthene positioned on Si?111?,Ge?111?,Sb₂Te₃,Bi₂Se₃ and Bi₂Te₃ substrates.We find that chemical absorption emerges when the arsenene,antimonene,or bismuthene layer is grown on the Si?111?or Ge?111?substrate,and the strong interaction will have great influence on the electronic structure of the arsenene,antimonene,or bimuthene.Meanwhile,physical absorption occours when an antimonene or bismuthene is grown on the Sb2Te3,Bi₂Se₃ or Bi₂Te₃ substrate,and the interaction between the substrate and the antimonene/bismuthene are of van der Waals type.The characteristics of Fermi surface in these systems depend on the p orbits of the Sb or Bi atoms in the antimonene or bismuthene layer.