Photoelectric Properties And Carrier Transport Control Of Two-dimensional Layered Molybdenum Selenide

Microelectronic technology has become a core technology current,and been applied in every aspect of our life,and every great improvement in the performance of microelectronics basically comes from the technological innovation of semiconductor materials.Scientists have been trying to improve the performance of semiconductor devices by looking for new materials and exploring new physical mechanisms of semiconductor materials.Among them,layered van der Waals materials with two-dimensional morphology can be an outstanding representative of new semiconductor materials.And 2D transition metal chalcogenide(2D-TMDs)are one of the best and have attracted much attention from researchers,especially the most layer 2D transition metal dichalcogenide show bright and clean the surface of the semiconductor,has the high carrier mobility,and optical band gap width at optical wavelengths,make its have potential use in the next generation of nanoscale electronic devices.In this paper,a typical two-dimensional layered molybdenum selenide(MoSe₂)was selected as the research object.High quality MoSe₂ single crystal and Te replaced by Se MoSe_2xTe2-2x alloy were synthesized by chemical vapor transport.The synthesized materials were measured by A variety of characterization methods,and The photoelectric response and carrier transport properties of the field effect transistor are studied,here are the main works:1.MoS2 single crystal was synthesized by chemical vapor deposition and chemical vapor transport,and the photoelectric field effect transistor with MoS2 as channel was constructed by mechanical stripping and micro-nano processing methods.The electrical characteristics of the device were measured,and the doping effect of air on channel and the contact effect of electrode metal were proved.The results show that the carrier mobility of MoSe₂ is 5.3 cm2 V-1 s-1,the electronic switching ratio(Ion/Ioff)is 106,the photoelectric switching ratio(Ip/IARK)is 103,the optical responsiveness is 58 mAW-1,and the external quantum efficiency is 1.58%.In addition,it is found that the air has obvious n-type doping effect on the MoS2 channel,which can be removed by vacuum annealing at 200?.The Schottky barrier formed when Ti electrode as an adhesive layer contacts with MoS2 is the smallest,which is close to ohmic contact.2.The ternary layered alloy MoSe_2xTe2-2x(x=0?1)with 2H phase was synthesized by chemical vapor transfer method using the strategy of Te replacing Se atom in MoS2.The results show that with the increase of x value,the conduction characteristics of the electronic transistors constructed on the MoSe_2xTe2-2x thin layer(6?7 layers)show an abnormal change from bipolar to N-type,which is attributed to the hole current restricted by the widening of the Schottky barrier.The optical band gaps of MoSe_2xTe2-2x single crystals(x=0,0.18,0.38,0.67,0.83,1)are in the range of 1.6 eV(red light)to 1.1 eV(near infrared).The phototransistor based on MoSe0.37Te1.63 shows an electrical switching ratio of 107(Ion/Ioff),a photoelectric switching ratio of 105(Ip/Idark),an optical response of 100 mAW-1(RI)and an external quantum efficiency of 2.38%(EQE).