Schottky Barrier Based On Two-dimensional Janus Material Heterojunction By First-principles Study

Since 2004,the emergence of graphene has attracted the attention of scientists.Because of its excellent physical properties,especially its outstanding electrical conductivity,graphene has been widely used in many fields.With the gradual development of graphene technology,more two-dimensional semiconductor materials have been found on the basis of graphene.For example,phosphorene is a two-dimensional material with extremely high hole mobility,Mo S₂is a kind of transition metal disulfide with a large specific surface area and atomic exposure.This makes them profoundly important for field-effect transistors,catalysis,and energy storage.The fabrication of two-dimensional materials inevitably leads to atomic defects,which will affect the electrical,thermal,mechanical,chemical,and even magnetic properties of the material itself.So structural defects are also a way of improving the two-dimensional material itself.In most two-dimensional layered materials,the force between adjacent layers is mainly van der Waals force.Under the action of this force,two two-dimensional materials with different properties can form van der Waals heterojunction at a low lattice mismatch rate,so as to meet people's needs for two-dimensional composite materials with various excellent properties.The Schottky barrier occurs when the metallic two-dimensional monolayer and the semiconductor two-dimensional monolayer integrate into a heterostructure through van der Waals interaction.Due to the metallic properties of graphene,the heterojunction materials with graphene can be effectively applied to the study of the Schottky barrier.In this paper,first principles were used to analyze the magnetic properties of the phosphene nanostrips with defects,and the regulation of the Schottky barrier of Janus material/graphene heterojunction was investigated.The main innovative results obtained are as follows:Chapter 3:Based on first-principles calculations,this chapter systematically studied the performance of the Van der Waals heterostructure formed by the Janus In₂SSe monolayer in contact with graphene.Two graphene/In₂SSe heterostructures are related to the Schottky potential.The height of the barrier and the type of contact can be changed by adjusting the distance between the control layers and applying an external electric field.Reduce the height of the n-type Schottky barrier by increasing the distance between the layers.By changing the distance between the layers or applying an external electric field,the contact type of the heterostructure Schottky barrier can be changed from n-type Schottky to p-type Schottky.This research results show that the heterostructures of In₂SSe and graphene are suitable for applications that require an adjustable Schottky barrier height.Chapter 4:Based on first-principles calculations,this chapter studied the structure of the two heterojunctions formed by WSe Te/graphene and the electronic properties of the contact interface.In this research,found an interesting phenomenon.When Te WSe is in contact with graphene,Te WSe changes from semiconducting to metallic.By reducing the interlayer spacing,a gradually larger n-type Schottky barrier can be formed.When Se WTe is in contact with graphene,a p-type Schottky barrier is formed.When reducing the layer spacing,the p-type Schottky barrier will gradually become smaller.When increasing the distance between layers,we will find that the Schottky barrier of the heterostructure will change from p-type contact to n-type contact.These findings can provide physical guidance for the design of high-performance controllable Schottky nanodevices.Chapter 5:First-principles calculations based on density functional theory.This chapter studied phosphorene nano stripe SV-(5|9)single defect and double defects due to the special properties of the quantum confinement effect.These defects are easily produced in phosphorene with higher surface density.The study found that when the SV-(5|9)defects exist,due to the defects existing in the hanging with a key of the atoms,so phosphorene bandgap will be the basis of introducing did not occupy the local state,half gold properties,used by the semiconductor makes it a conductor.