Study On The Electronic Structure Properties Of Two-dimensional Heterostructure Based On α-tellurene

In 2004,the physicists of the University of Manchester,Andre Geim and Konstantin Novoselov,successfully separated graphene from graphite by mechanical exfoliation,which opened the door to the world of two-dimensional（2D）atomically thin materials.After that,many new 2D materials,including silicene,hexagonal boron-nitride,transition metal dichalcogenides（TMDs）,phosphorene and even a-tellurene,have also been studied in theory and experiment because of their intriguing mechanical,optical and electronic properties in nano-devices.Nevertheless,no single 2D material possesses perfect properties for practical applications.For instance,the zero band gap of graphene limits its application in logic circuits;the poor stability of phosphorene restrains its use under open air and water environment.Hence,it is especially important to combine together the advantages of disparate single-layer materials.Studies have demonstrated that the van der Waals heterostructure（vdWH）composed of 2D GeSe and SnS can not only retain the direct band gap of the monolayer GeSe,but also increase the optical absorption coefficient from the visible light to the near ultraviolet region.More recently,a-tellurene,a new 2D material composed of only one element,has been theoretically predicted and soon fabricated experimentally.It has a stable1T-MoS₂-like structure with higher electron and hole mobility and significant light absorption properties than MoS₂.Based on these excellent properties of a-tellurene,this paper studied the electronic structure properties of the bilayer a-tellurene/MoS₂vdWH and the trilaminar MoS₂/a-tellurene/WS₂ vdWH by first-principles method,and we have a controllable modulation of their electronic properties by interlayer coupling,biaxial strain and external electric field（E-field）,which can maximize their use in electronic and optoelectronic devices.The main research contents are as follows:（1）Construct the a-tellurene/MoS₂ vdWH and regulate its electronic properties.The calculation results show that the interlayer coupling can effectively tune the band gap values of the heterostructure,and with the enhancement of the interlayer coupling,the a-tellurene/MoS₂ vdWH can be changed from type-I band alignment to type-II band alignment.In addition,applying an external E-field in both positive and negative directions can also alter its band alignment from type-I to type-II,further increasing the strength of the E-field can cause the heterostructure to be converted from semiconductor to metal.（2）Construct the MoS₂/a-tellurene/WS₂ vdWH and regulate its electronic properties.The calculation results show that applying biaxial strain can effectively tune the band gap values of the heterostructure,and the appropriate compressive strain can change the heterostructure from the indirect band gap to direct band gap,which is helpful to extend its application in optoelectronic devices.Besides,exerting an external E-field in both positive and negative directions to the heterostructure can cause the transition from type-Ⅰ band alignment to type-Ⅱ band alignment,and continuing to increase the intensity of the E-field can cause the heterostructure to be converted from semiconductor to metal.