Theoretical Research On Optical And Electronic Properties Of Two-dimensional SnS₂-based Heterostructures

Since the successful synthesis of graphene in 2004,more and more attention has been paid to explore other graphene-like materials due to the excellent properties of graphene,such as high carrier mobility,good conductivity and quantum hall effect at room temperature.There are many kinds of two-dimensional?2D?materials,which can be divided into metals,semiconductors,insulators.For example,boron nitride?BN?,transition-metal dichalcogenides?TMD?,black phosphorus?BP?and other compounds cover most of the elements in the periodic table,and thus exhibit unique optical,electronic and magnetic properties,indicating that they can be applied in the fields of optoelectronics,spinelectronics and so on.Moreover,constructing the van der Waals heterostructures?vdWHs?can effectively modulate the properties of 2D materials and broaden their applications fields.For example,the MoS₂/g-C₃N₄ heterostructure can overcome the corrosion resistance of MoS₂ and improve the light absorption coefficient.In this thesis,we study a series of SnS₂-based heterostructures,including SnS₂/n-BN multilayer heterostruture,GeSe/SnS₂?SnSe₂?p-n junctions and SnS₂/polyphenylene heterostruture based on density functional theory.The main results are as follows:Firstly,our theoretical results predicate that the SnS₂/n-BN multilayer heterostructure possess type-II band alignment with direct band gap.Moreover,the results show that the band gap and work function decrease with the increase of the layer BN for the SnS₂/n-BN multilayer heterostructure;In addition,the the SnS₂/n-BN multilayer heterostructure can be transformed from the type-II band alignment to the type-I band alignment under the external electric field,and the direct band gap also can be tuned to indirect band gap effectively.Secondly,we predict that the GeSe/SnS2?SnSe2?p-n junction exhibits the type-III band alignment with band to band tunneling mechanism?BTBT?.Moreover,when applying the negative external electric field,the p-n junction can retain the type-III band alignment and enlarge the tunneling window.However,the positive electric field can transfer the GeSe/SnS₂?SnSe₂?p-n junction from the type-III to the type-II or type-I band alignment.Our findings indicate that the GeSe/SnS2?SnSe2?p-n junction has potential applications in tunneling field effect transistors.Finally,the SnS₂/polyphenylene heterostructure exhibits the type-II band alignment,and possesses high absorption coefficient in the visible and ultraviolet region.In addition,the electronic properties for the SnS₂/polyphenylene heterostructure is sensitive to the interlayer distance.The external electric field not only can transform the type-II band alignment to the type-I or type-III band alignment,but also tune the band gap effectively.Our results offer useful information for the SnS₂/polyphenylene heterostructure has potential applications in nano-optoelectronic devices fields.