Performance Modulation Of Two-dimensional Transition Metal Dichalcogenides And Its Heterostructures

Two-dimensional（2D）transition metal dichalcogenides（TMDCs）and their van der Waals（vd Ws）heterostructures are potential candidates for the construction of next-generation electronic devices.Tuning their electronic band structure and carrier transport characteristics is crucial for realizing electronic devices with desired performances and functions.In this thesis,self-terminated surface monolayer oxidation process for TMDCs was developed by applying oxygen plasma,which is compatible with traditional semiconductor processing technology.Carrier modulation in TMDCs is achieved via the charge transfer between surface oxides and underlying TMDCs.By further utilizing the material selectivity of this oxidation process,we also achieved the regulation of its heterostructure band structure and carrier transport.In addition,based on the modulation effect of material thickness on the energy band of TMDCs,diodes with different functions were fabricated.Main achievements are listed as follows:（1）By changing the process parameters,the oxygen plasma self-terminated oxidation process can modulate the hole carrier concentration of the WSe₂channel and the contact resistance at the metal-WSe₂contact interfaces.A high-performance p-type WSe₂Schottky transistor is achieved with appropriate plasma doping concentration.（2）Degenerately p-doped contacts at the intrinsic n-type WSe₂channel is achieved by oxygen plasma with a h-BN vd W capping mask.Subsequently,WSe₂p-MOSFET based on back-to-back p-n junctions is demonstrated with excellent performances.（3）The modulation of band structure and carrier transport in vertical Mo Te₂/Mo S₂heterostructure is presented via thickness engineering and oxygen plasma selective-doping.A variety of devices and functions such as non-rectifying n-n junction diodes,p-n junction diodes with high rectification characteristics,and low-power tunneling diodes have been obtained.The proposed doping method is simple,controllable,and compatible with traditional semiconductor processes,it can be ultilized as universal strategy for the performance modulation of TMDCs and their heterostructures.In the follow-up work,we will further explore the improvement of devices performance.