| Graphene has excellent characteristics such as high flexibility,light weight and easy preparation in large areas,and has stimulated the interest of researchers to explore two-dimensional materials.However,the discovered two-dimensional materials face many problems,for example,the level of preparation of the materials is far from the standard for optoelectronic device applications,the instability of phosphorene,and the lack of band gap in graphene and stanene are their fatal drawbacks.According to the demand,the electronic properties of two-dimensional materials must be improved.Doping,adsorption,defects,heterojunctions and discovering new two-dimensional materials are effective methods.Based on the above problems,in this paper,we investigated the electronic structures of two-dimensional materials such as stanene and blue phosphorene based on first principles calculations,and modulated their electronic properties by means of adsorption,doping,defects and heterojunctions.Then,the electronic structure and optical properties of novel two-dimensional materials with C3N-like configuration are predicted,mainly including the following four aspects.1.The effects of adsorption of 12 transition metal atoms on the electronic structure and magnetic properties of stanene were explored.When Ni,Ru and Pd atoms adsorbed on stanene,the Dirac cone of stanene is opened with band gaps of 109.4 meV,69.6 meV and 32.4 meV,respectively.And the adsorption energy of stanene to foreign atoms is as high as 6.241 eV,which is better than that of phosphorene and graphene.Moreover,Fe,Co,Ru,Rh and Os atoms adsorbed on stanene,which induced magnetic moments of 3.144?B,2.024?B,2.028?B,1.007?B and 1.995 ?B,respectively.More interestingly,when Rh and Os atoms adsorbed on the stanene,the system shows semi-metallic properties.This provides a reference for the design and application of spintronic devices based on stanene.2.Four kinds of vacancy defects and six kinds of heteroatomic doping of stannene have been systematically studied.The results shown that both defects and heteroatom dopes can modulate the bandgap of blue phosphorene,and makes the transition from indirect bandgap to direct bandgap of blue phosphorene.Magnetic properties can be induced by introducing defects and doping in blue phosphorene.It is expected to provide a theoretical reference for the design of electronic devices based on blue phospholene.3.Two models of stanene and blue phosphorene heterostructure were constructed,and it found that the A configuration is the most stable configuration of stanene/blue phosphorene heterostructure,and the heterostructure is most stable when the interlayer distance is 3.75 A.Finally,applied electric field,tensile and compressive strain can be used to tune the electronic properties of stanene/blue phosphorene heterostructure.It is expected that the heterostructure can be applied in nano-electronic and optoelectronic devices.4.Three novel two-dimensional materials,C3P,Si3N and Si3P,were constructed by using monolayer C3N as the prototype.The corresponding phonon spectrum shown that all three structures have no imaginary frequency.Moreover,the total potential energy of the novel two-dimensional material only fluctuates above and below a constant magnitude after annealing at 300 K and 500 K under molecular dynamics simulation,and the structures are not reconstructed,which indicates that the high dynamic and thermal stability of the systems.Considering the effect of biaxial tensile strain on the new two-dimensional material,the phonon spectrum at a maximum stress of 11%has no imaginary frequency,indicating the mechanical stability of the novel material.The results shown that C3P,Si3N and Si3P exhibit excellent optical absorption in the visible range.And the biaxial tensile and compressive strains can effectively modulate their optical properties,and the findings may provide theoretical guidance for the design and application of semiconductor electronic and optical devices. |
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