[ Instrument Network Instrument Development ] Recently, Zheng Xiaohong, a researcher at the Institute of Solid State Physics, Hefei Institute of Material Science, Chinese Academy of Sciences, made new progress in the study of quantum transport of two-dimensional ferroelectric tunnel junctions, using density functional theory + non-equilibrium Green's function. Methods The transport properties of two-dimensional ferroelectric tunnel junctions of graphene/BiP van der Waals heterostructures were calculated, and the electro-resistance ratio of 623% was achieved. The results were published on Nanoscale under the title of Realizing giant tunneling electroresistance in two-dimensional graphene/BiP ferroelectric tunnel junction.
Ferroelectric tunnel junctions have important application potentials in non-volatile memories due to the presence of electro-resistance effects. The most researches are currently using metal or semiconductor as the two-terminal electrodes, and the ferroelectric layer with perovskite structure as the central scattering. The three-dimensional ferroelectric tunnel junction of the area. In such a tunnel junction, the ferroelectric layer cannot be made too thin due to the depolarization effect caused by the accumulation of charges at the interface between the electrodes at the both ends and the central region, which makes it difficult for the three-dimensional ferroelectric tunnel junction to meet the requirements for minimizing the size of the device. Since the two-dimensional material has only the thickness of the atomic layer itself, the construction of the ferroelectric tunnel junction by using the two-dimensional ferroelectric material can greatly reduce the size of the ferroelectric tunnel junction memory, and thus has been widely concerned. Theorists have predicted a large number of two-dimensional ferroelectric materials, such as: the fourth main group of sulfides (SnS, SnSe), the fifth main group of elements of the black phosphorus-like structure (BiP) and the silylene-like structure (SbN) Etc., even two-dimensional ferroelectric material In2Se3 with vertical in-plane polarization has been experimentally prepared. However, how the electro-resistance effect of the two-dimensional ferroelectric tunnel junction is better than the three-dimensional ferroelectric tunnel junction needs further study.
To this end, Zheng Xiaohong's group used the first-principles density functional theory combined with the non-equilibrium Green's function method to calculate the transport properties of two-dimensional ferroelectric tunnel junctions with two-dimensional van der Waals heterostructures (graphene/BiP). . As a result, it was found that by incorporating B atoms in the graphene layer of the left electrode and N atoms in the graphite layer of the right electrode, an electro-resistance ratio (TER) of 623% can be obtained, and a three-dimensional ferroelectric tunnel junction is obtained. Resistivity ratio. According to previous research work, the electrical resistance ratio of the three-dimensional ferroelectric tunnel junction is approximately in the range of 300% to 800%. It was found that the resulting high electro-resistance ratio was derived from the significantly different shielding effects of the left and right electrodes and the resulting significant change in the tunneling barrier height before and after the ferroelectric reversal. The results show that the two-dimensional ferroelectric materials have important application potential in constructing two-dimensional ferroelectric tunnel junctions, achieving giant electric resistance effects and ferroelectric storage.
The work was funded by the National Natural Science Foundation of China, and all calculations were completed at the Hefei Sub-center of the Chinese Academy of Sciences Supercomputing Center.
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