Fabrication And Transport Properties Of Two-dimensional MoTe₂ And Its Van Der Waals Heterojunction

In recent years,2D transition-metal dichalcogenides(TMDs)have attracted large attentions because of their layered structure,crystal-thickness dependent physical characteristics and wide variety of novel properties.MoTe₂as an important member of TMDs,is a potential building block for assembling high performance logic and optoelectronic devices due to its suitable bandgap(?1.0 e V)and excellent transport properties.What's more,van der Waals heterojunctions formed by stacking different2D materials in vertical direction provides crucial platform for exploring novel physical properties.Hence,MoTe₂and its van der Waals heterojunctions are the research objects in this paper,and the research contents and results are as follows.The influence of electron beam lithography(EBL)process on the electron transport performance of MoTe₂field effect transistors is investigated.It was found that MoTe₂flake annealed in air with high temperature can lead to p-type doping,and the hole mobility is close to 11.4 cm²V^-1s^-1;MoTe₂flake with electron beam irradiation can introduce n-type doping,and the electron mobility is close to 1.34cm²V^-1s^-1.This n/p type doping method is simple,controllable and reversible.In addition,polymethyl methacrylate(PMMA),which is commonly used in EBL process,was found to be ineffective in preventing electron beam-induced electron doping.The above results show that the EBL process has a significant effect on the performance of MoTe₂devices.Furthermore,MoTe₂/ReS₂and MoTe₂/Bi₂O₂Se van der Waals heterojunctions were constructed and their electron transport and optical properties were studied.The results show that the performance of ReS₂crystals is very stable,but the transport properties of MoTe₂is sensitive to the annealling in air.Therefore,the transport characteristics of MoTe₂/ReS₂heterojunction device could be effectively modulated by heat treatment.The application of this heterojunction in logic circuits and other fields is expanded.What's more,multilayer Bi₂O₂Se crystals and MoTe₂/Bi₂O₂Se van der Waals heterojunction were prepared.The electron transport properties of Bi₂O₂Se devices and MoTe₂/Bi₂O₂Se heterojunction were studied by using ionic liquid as the top gate.The heterojunction device has excellent photoelectric response characteristics,and the light/dark current ratio reaches 90.These results indicate that MoTe₂and its van der Waals heterojunctions have important potential applications in electronic devices and photodetectors.