First-principles Study Of The Electronic Properties Of 3d Transition-metal Doped MoTe₂ Monolayer And MoTe₂/WTe₂ Lateral Heterostructures

Stimulated by the prominent achievement of graphene,two-dimensional layered materials at atomic scale have attracted extensive attention.As one kind of its inorganic analogs,two-dimensional transition metal dichalcogenides?TMDCs?with the chemical formula MX₂ has a good prospect of application in the next generation of nano-electronic equipment production and development due to its excellent optical,electronic and catalytic properties.As a typical TMD material,MoTe₂ monolayer has been successfully synthesized experimentally.Because of the quantum confinement effect,it changed from an indirect bandgap semiconductor to a direct bandgap semiconductor with a size of 1.10 eV,which laid a foundation for its application in optoelectronic devices.In addition,the diversified phase structure of MoTe₂monolayer?H phase with semiconductor properties,T phase with metal properties and T'phase with semimetal properties?enables it to have more abundant physical properties.Therefore,it has become our research goal to modify and manipulate MoTe₂ monolayer properly,so as to develop more potential application.In this article,the first-principles calculation has been performed based on density functional theory using the vasp package.Taking MoTe₂ monolayer as the main research object,we studies the electronic properties by doping and constructing lateral heterostructure.The main work and innovation points are summarized as follows:1.We investigated the magnetic performance of MoTe₂ monolayer doped by transition metal?TM?Ti,V,Cr,Mn,Fe,Co and Ni atoms as well as straining effects.The dopants of Ti,V,Mn,Fe,Co and Ni atoms can induce magnetism in MoTe₂ monolayer and the magnetic moments mainly originate from the localizing unpaired TM-3d electrons.Mn and Fe-doped MoTe₂ nanostructures show the half-metallic character with 100%spin polarization near the Fermi level.The elastic strain applied on TM-doped MoTe₂monolayer systems leads to the redistribution of the electrons in TM-3d states,which results in the magnetic states transition in doped systems.The magnetic moments of Ti,Co,and Ni-substituted MoTe₂sheets monotonously increase with the increase of strain,while the magnetic moment of V-substituted MoTe₂ sheet has an oscillatory variation with the increase of strain.The research results offer an important theoretical support for further application of strain-driven spin devices on MoTe₂ nanostructures.2.Lateral two-dimensional?2D?heterostructures with the formation of one-dimensional interfaces have opened up unprecedented opportunities in modern electronic device and material science.In this work,electronic properties of size-dependent MoTe₂/WTe₂ lateral heterostructures?LHSs?are investigated through the first-principles density functional calculations.The constructed periodic multi-interfaces patterns can also be defined as superlattice structures.Consequently,for H-MoTe₂/WTe₂,the direct band gap character is remained in all considered LHSs without any external modulation,while the gap size changes within little difference range with the building blocks increased.As a result of band folding,the location of CBM and VBM will change from P-point to?-point when m plus n is a multiple of 3 for A-mn LHSs.The band gap located at the high symmetry?-point is convenient for electron excitation,which might be useful to optoelectronic device and could be achieved by band engineering.Electrons and holes would be separated on the opposite side of the LHSs,forming type-II band alignment which would decrease the recombination rate of the charge carriers and facilitate the quantum efficiency.Moreover,external biaxial strain leads to efficient bandgap engineering for not only H-MoTe₂/WTe₂ but als T'-MoTe₂/WTe₂.Our results show that MoTe₂/WTe₂ LHSs can serve as potential candidates for next-generation electronic and optoelectronic devices.