Effect Of Electron Beam Irradiation On The Properties Of Two-dimensional Materials And Their Heterostructures

Various irradiation sources exist in people's living environment.For example,there is ultraviolet radiation,X ray irradiation,or electron beam irradiation in sterilization of hygienic food,medical examination,or operations of lots of specific equipment such as transmission electron microscope?TEM?and scanning electron microscope?SEM?.In the outer space,radiation is more common due to the existence of a large number of high-energy rays.However,there are some scientific and technical issues needed to be addressed,e.g.,whether electronic devices can operate as usual under such irradiation environments,and whether people can develop anti-radiation electronic devices.In recent years,2-dimensional?2D?materials and devices are hot topics in scientific research.As electron beam is a widely existing radiation source,in my thesis,I present a systematic study upon the effects of electron beam irradiation on the properties of 2D materials and devices.Graphene has attracted a wide attention in industry and academia because of the unique and excellent properties since its discovery.However,the lack of an intrinsic band gap has limited its applications in electronic and opto-electronic devices.Therefore another type of graphene-like material??transition metal dichalcogenides?TMDCs?becomes hotspots.Further stacking of vertical 2D heterostructures greatly extends the functions of single materials,which makes the heterostructures have improved electronic properties in a variety of their applications as optoelectronic components,laser diodes,and field-effect transistors?FETs?.However,it is still lack of systematic and in-depth research on the structural and electrical evolutions of heterostructures in irradiated environments.In this thesis,monolayer molybdenum disulfide?MoS₂?and graphene are used to build a MoS₂/graphene heterostructure,and the electron beam is used to irradiate the sample.The changes in the optical,electrical properties and work function of the materials and devices at different irradiation doses are compared with the corresponding results of single materials.We discover that the use of heterogeneous stacking can hinder the performance degradation of MoS₂ caused by electron beam irradiation.Under the same dose of electron beam irradiation,by inserting a monolayer graphene between MoS₂ and substrate,the photoluminescence?PL?intensity of the heterostructure area is always greater than the monolayer MoS₂.Moreover,the PL energy of MoS₂/graphene heterostructure region is more stable than the pure monolayer MoS₂.We attribute this improvement to the shielding effect of graphene:the presence of single-layer graphene inhibits the effects of the substrate on MoS₂.We also systematically reveal the effects of electron beam irradiation on the other properties of MoS₂/graphene heterostructures,for example,Raman spectra as well as transfer and output characteristic curves of samples.In general,our research not only deepens the cognition of the radiation effects on the 2D heterostructures,but also opens a new way to the design of novel anti-radiation devices.