Interactions And Electronic Structures Of Two-dimensional Semiconductor MXene-Metal Contact

In recent years,the technology of low-dimensional materials has been extensively investigated,and two-dimensional semiconductor materials become the focus of material research.A two-dimensional material named MXene has been widely used in Lithium ion battery,supercapacitor and catalysts.However,the study of contact between MXene and metal electrodes is rather limited,although it is of great importance in the electronic and optoelectronic devices.Of course,the electrical properties and electronic structures of the interface between metal substrate and MXene are the critical research point in this field.In this paper,first-principles calculation was performed to study the interactions and electronic structures of MXene-metal contact.The main work and conclusions are as follow:Firstly,MXene-metal contact models were built and the structures were optimized by VASP software package.According to the matching degree of different MXene and metal base models,we selected the suitable and flat metal substrates,and set up supercell and unit cell contact models respectively,so that the mismatch is less than 5%for all contact models.The stabilities of the contact structures were studied to ensure the rationality of the contact structure.Secondly,the band structures of MXene-metal contact were calculated and analyzed.Our calculation results indicate that most contacts show indirect bandgap characteristics mainly contributed by MXene,which are not beneficial to high-performance devices.However,it is out of expectation that the contact models of Ag-Sc₂CO₂ and Au-Sc₂CO₂exhibit direct bandgap characteristics,and the n-type Schottky barriers are calculated to be 0.122 and 0.763eV,respectively.Furthermore,the metal-induced gap states?MIGSs?are found in Zr₂CO₂ system,which produces strong Fermi level pinning and leads to lower Schottky barrier heights?0.124eV,0.163eV?in n-type ohmic contacts?Ag-,Pd-?and n-type Schottky contacts?Au-,Pt-?.The tunnel barriers of MXene-metal contact were calculated and analyzed.Tunnel barrier is another obstacle for devices to reach high electrical performance.Via analysis of the calculated electrostatic potential,we found that only the structures of Hf contacting with Hf₂CO₂,Zr₂CO₂ and Ti₂CO₂ have no tunnel barrier,and all other contacts show some certain size of contact barriers,which would be guidance for design of the devices.In addition,we also explored the properties and potential applications of a new structure,aMXene,contacted with TMDC.The possibility of preparation and stability of aMXene/mTMDC structures were investigated.The strong built-in electric field in the contacts,and novel electronic band structures offer the possibility of application in microelectrical devices and energy conversion catalysis.