Modulation Of The Electrical Properties Of Two-dimensional Materials And The Development Of Heterojunction Hot-electronic Transistors

Since Geim,Konstantin and their collaborators successfully produced graphene by mechanical stripping for the first time in 2004,two-dimensional nanomaterials have attracted more and more researchers'attention.Due to the excellent electronic and magnetic properties,they are predicted that they could be applied in the field of optoelectronics such as solar cells,light-emitting diodes and spin devices.Two-dimensional nanomaterials have shown more and better physical and chemical properties,especially the two-dimensional nanomaterials represented by graphene-like hexagon honeycomb structure,which have achieved fruitful results in theory and experiment.In this paper,the first-principles calculation method based on density functional theory is used to study the electronic structures,magnetic and optical properties of 1T-ZrS₂doped by transition metal(TM)atom and non-magnetic atoms.At the same time,the transistor with BP/MoS₂heterogeneous substrate is studied to explore its electrical performance in experiment.The related results are mainly described as follows.First,the effects of N doping and(Mn,N)co-doping on the electrical properties and magnetic properties of single-layer ZrS₂are studied.In the case of single doping of N atoms,ZrS₂monolayer shows the properties of non-magnetic metals.But in the case of(Mn,N)co-doping of ZrS₂monolayer,the whole system will show the properties of magnetic materials.First nearest neighbor(Mn,N)doped ZrS₂monolayer(N-Mn-N small triangle structure)have the properties of metal materials.the second nearest neighbor(Mn,N)is doped with ZrS₂monolayer(N-Mn-N triangle structure),which has the magnetic properties of semiconductor materials.the third nearest neighbor(Mn,N)co-doping of ZrS₂monolayer(N-Mn-N linear structure)has the properties of magnetic metal.This is because the manganese atom induces a highly localized state in the band gap.The polarization charge mainly comes from Mn-3d orbital,less from N-2p orbital and S-3p orbital.The Zr-4d orbital has almost no effect on the polarized charge.We also found that hybrid Mn-3d and S-3p lead to ferromagnetic coupling,but hybrid Mn-3d and N-2p lead to anti-ferromagnetic coupling.This work provides a method to generate magnetic properties of ZrS₂monolayer for spintronic applications.The application of ZrS₂in spin devices has a theoretical method.Seconed,the development of thermoelectronic transistor based on BP/MoS₂ van der Waals heterojunction.Due to the backscattered parasitic current from the barriers,the current gain of the widely used amplifier is far from ideal.In this work,we demonstrate a vertical Au/Al₂O₃/BP/MoS₂tunneling hot-electron transfer amplifier with a hot-electron emitter-base junction and a p-n junction as the base-collector barrier.Fairly monoenergetic electrons traverses through the ultrathin Al₂O₃dielectric via tunneling,which are accelerated and shifted to the collector region.The devices exhibit a high current on-off ratio of>10⁵and a high current density(J_C)of?1000 A/cm²at the same time.Notably,this work demonstrates a common-emitter current gain(?)value of 1384 with a nanowatt power consumption at room temperature,which is a record high value among the all 2D based hot-electron transistors.Furthermore,the temperature dependent performance is investigated,and the?value of 1613 is obtained at150 K.Therefore,this work presents the potential of 2D based transistors for high-performance applications.