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    Home > New progress in the study of two-dimensional ferroelectric tunnel junctions with vertical external polarization

    New progress in the study of two-dimensional ferroelectric tunnel junctions with vertical external polarization

    • Last Update: 2020-02-04
    • Source: Internet
    • Author: User
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    Recently, the research team of Zheng Xiaohong, Institute of solid state, Chinese Academy of Sciences, has made new progress in the study of quantum transport of two-dimensional ferroelectric tunnel junctions DFT + NEGF method is used to calculate the transport properties of graphene / in2se 3 van der Waals heterostructure in two-dimensional ferroelectric tunnel junctions, and 108% of the electric resistance ratio is achieved The results were published in Physical Review B (Phys Rev B 2020, 101, 014105) Ferroelectric tunnel junctions (ftjs) use ferroelectric materials as the center tunneling barrier and metal or semiconductor as the electrode Because of their potential application in nonvolatile memory devices, they have been widely studied in experiments and theories The ratio of tunneling electric resistance (TER) is a very important parameter to characterize the data storage performance of ftjs So far, there are many researches on how to design high performance ftjs with large ter ratio However, most attention is still focused on the 3D ftjs using three-dimensional (3D) ferroelectric thin films as tunnel barriers As we all know, due to the charge accumulation on the surface, the critical thickness of 3D ferroelectric materials used to observe spontaneous polarization is limited, which contradicts the requirement of miniaturization of devices Therefore, how to reduce the critical thickness of ferroelectric thin films is a key problem in the further development of high-performance ftjs In recent years, a new research direction of ferroelectric materials is the study of two-dimensional (2D) ferroelectric materials, which provides a natural choice for the construction of devices with atomic thickness If 2D ferroelectric materials can be used to construct high performance ftjs with large ter ratio, it will greatly reduce the scale of ftjs devices In fact, the application of 2D ferroelectric materials in ftjs has attracted extensive attention of researchers in recent years For this reason, Zheng Xiaohong's team designed 2D ftjs with van der Waals vertical heterostructure (graphene / in2se 3) based on the fact that two surfaces of two-dimensional ferroelectric materials with out of plane polarization have different work functions By using density functional theory and non-equilibrium Green function method, a large ter ratio of 1 × 108% is obtained, which is higher than that of most 3D ftjs The reason is that there is a great difference between the work functions of two surfaces of in 2SE 3 layer (about 2.396 EV), and the work function of graphene is close to that of one surface Therefore, when graphene contacts with its different surfaces, graphene will show electron transfer or non transfer to in 2SE 3, so that in 2SE 3 will show two different states of conducting and non conducting The relevant research shows that for 2D ferroelectric materials with out of plane ferroelectric polarization, it is convenient to design high-performance 2D ftjs by only considering the work function At the same time, it also shows that two-dimensional ferroelectric materials, especially the ferroelectric materials with out of plane polarization, have important application potential in the construction of two-dimensional ferroelectric tunnel junction, the realization of giant electric resistance effect and ferroelectric storage The work was supported by the National Natural Science Foundation of China, and all calculations were completed in Hefei Branch of the Supercomputing Center of the Chinese Academy of Sciences.
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