Influnce Of Vacancy And Strain On Electronic Structures In Two-dimensional Semiconductor Materials

Recently,two-dimensional?2D?semiconductor materials have attracted considerable attention.Some 2D layer materials like the transitional metal dichalcogenides?TMDC?,the black phosphorene and the arsenene etc have been studied widely.As we all know,TMDC and black phosphorene show a direct band gap,and the arsenene single layer is an indirect band gap semiconductor.More important,all of them show the good electronic and optical properties,and the black phosphorene has high electron mobility.Due to demand of electronic device in the engineering field,the controlled electronic properties appear increasingly important.Previous studies have shown that strain can modulate not only the band structure of single-layer MoS2,black phosphorene and arsenene,but also the effective mass.Meanwhile,the vacancy defects can also change the band structures of two-dimensional semiconductor.In this dissertation,the structure model and the band structure of transitional metal dichalcogenides?TMDC?,black phosphorene and two kinds of arsenene have been investigated by using the first principles method.The effects of the vacancies and the biaxial strain on the electronic structures for the buckled arsenene,the single-layer MoS2,the black phosphorene have been discussed in detail.By considering the different vacancies in the arsenene,it is found that no matter where vacancy is,the band gap is always smaller than band gap of a perfect arsenene.Biaxial strain does not change the gap type of black phosphorene,just change the width of the band.Both kinds of the arsenene structures with the biaxial strain are all changed from indirect band gap into direct band gap.Biaxial compressive strain can induce a transition of the band gap from indirect to direct for the monolayer MoS2.Biaxial tensile can induce an inverse transition of the band gap in the monolayer MoS₂.