Research On Two-dimensional Van Der Waals Ferroelectric Materials

Since the discovery of graphene in 2010,the family of 2D materials has continued to grow.The stable layered structure of 2D layered materials,the chemical properties of surface saturation,and the weak interactions between the layers are important for realizing various excellent physical properties,such as electrical conductivity,topological properties,ferromagnetism,and iron,at the limit thickness of the atomic scale.The electrical properties have laid a solid foundation,and also provided a new platform for the development of new functional devices.The main focus of this thesis is on the ferroelectricity of 2D materials.In the traditional ferroelectric field,as the thickness of ferroelectric materials continues to decrease,the out-of-plane ferroelectric polarization is easily disturbed by the gradually increasing depolarization field,which affects the stability of the ferroelectric domain structure,so there is a so-called thickness limit.However,in recent years,a lot of single-layer ferroelectrics have appeared in new van der Waals materials,such as WTe₂,Cu In P₂S₆ andα-In₂Se₃,etc.These two-dimensional ferroelectric materials are used for the preparation of pure two-dimensional nonvolatile Sexual ferroelectric memory offers some new possibilities.This paper mainly studies the ferroelectric field effect transistor devices prepared by few-layer graphene andα-In₂Se₃ with 2H structure.It is found thatα-In₂Se₃ with 3R structure has the same ferroelectric control performance,and the ferroelectric field is greatly improved by changing the preparation method.Resistivity of the effect tube.It is foreseen that layered two-dimensional ferroelectric materials will provide new possibilities for the further development of micro-nano devices in the future.The main research contents of this paper are as follows:Chapter 1:First,the background of ferroelectric research is reviewed,and several properties that must be paid attention to in ferroelectric research,such as Curie temperature,hysteresis loop,etc.,are briefly introduced.The theoretical and experimental research progress of two-dimensional ferroelectric materials is briefly introduced.The application of ferroelectric materials in electronic devices.Chapter 2:The first part introduces the techniques used in the experiment,including the exfoliation of 2D materials,the preparation of heterojunctions by the transfer of 2D materials,electron beam exposure and metal evaporation to prepare metal electrodes,etc.The second part is the sample characterization methods,including atomic force microscopy,piezoelectric force microscopy and Raman spectroscopy.Chapter 3:The research progress ofα-In₂Se₃,the difference between 2H structure and 3R structure and the research status are introduced,and then the Raman spectrum,PFM and other characterizations of theα-In₂Se₃ we use and the preparation method of Fe FET are introduced.Finally,the test and data of Fe FET are carried out.analyze.Chapter 4:The device preparation method in Chapter 3 has been improved,and the regulation of the graphene conduction channel has achieved a more significant effect by using the common polarization effect of deionized water andα-In₂Se₃.This chapter mainly introduces the differences in device fabrication methods and the significant improvement in the regulation effect.Chapter 5:Summarizes the research results of the experimental part of the paper and prospects for the future.