The Department of Physics and its cooperation team of the National People's Congress won an important breakthrough in the field of two -dimensional iron electricity materials!

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New results of the Department of Physics!

Recently, Professor Ji Wei of the Department of Physics at Renmin University of China and Professor Liu Shiping of Hong Kong Polytechnic University and Professor Manish Chhowalla of Cambridge University in the United Kingdom won important breakthroughs in the field of low -dimensional polarization materials.

The relevant research results are published in the world -rear science and technology journal published on May 27, 2022, " Science.

[Science 376, 973-978 (2022)

Doi: 10.1126/science.abm5734]

Brief introduction and related background

In October 2020, Professor Ji Wei of the Department of Physics at Renmin University of China and the cooperation team found the world's first single -molecule station GD@C82 through theoretical calculation and experimental measurement. After the year, the physical size compressed to the ultimate single molecular level (~ 1 nm, one billionth of one meter).

This time, through theoretical calculations and experimental measurements, they found the piezoelectric and iron electrical effects in the non -rotating two -dimensional heterogeneous knot with only 6 atomic layers thick, which are the first international internationally. The result deepened the understanding of the novelty of the two -dimensional materials and expanded the family members of the iron electrical materials, and demonstrated the potential of the two -dimensional iron electrical materials in future information storage applications.

Principles and applications of iron electricity materials

Ferroelectricity is usually in a special type of electronics material. The geometric structure of this type of material breaks the spatial counterpart symmetry, so that the positive and negative charges of the system will not be over again, and the spontaneous polarization intensity will be generated. This spontaneous polarization direction can be flipped through an external electric field, and there is a stagnation line similar to the iron magnetic material. Therefore, the properties of this properties and iron magnetic analogy are called iron electrical. In the iron electrical material, the two electrical states of the polarization strength vector may correspond to "0" and "1" in computer binary languages, respectively. Because the electrical status can be repeatedly read and write and long -term preservation, iron electrical materials are widely used in many fields such as iron electrical memory, iron electric tunnel knot, iron electric capacitor, and iron electrical diode. Traditional iron electrical materials are mainly ABO3 perovskite -type body phase material. Under the trend of miniaturized and integrated electronic equipment, exploring small -sized and foldable new iron electrical materials has become a cutting -edge hotspot problem in international related fields. In the traditional iron electrical materials, when its thickness is reduced to several nanometer levels, the surface degeneration effect of the material is significant, and the iron electrical properties of the material will be significantly weakened or even disappeared. This is the critical size effect of iron electrical materials. Therefore, how to design and prepare high -performance iron electrical films in low -dimensional and small -sized sizes has become one of the major challenges in this field.

In recent years, two -dimensional materials represented by graphene and transition metal sulfur compounds have shown a lot of novelty that is different from the body phase material, and opened a new door to find low -dimensional iron electricity materials. However, due to the difficulty of breaking the absence of the outer structure of the absence of the other, most two -dimensional iron electrical materials can only produce the spontaneous polarization inside and outside the surface, and the actual technical application disorders are large. Thanks to the opposite sex of the mechanical strength unique to the two -dimensional materials, that is, the strong internal price bonds and weaker inter -layer non -common price interactions have been successfully realized. Construct a Moore hyper crystal, and the center of the center of the central break is backward, and the centers of the center are symmetrical, generating a switching iron electrical category, and exploring a new way to prepare a new iron electric ultra -thin material at the atomic scale. For example, in 2021, "Science" reported the corner double -layer six -square boron -nitride (Science 2021, Doi: 10.1126/Science.abe8177, 10.1126/Science.abd3230). Nature Nanotech. 2022, 10.1038/S41565-021-01059-Z).

However, the iron electrical properties in these structures are caused by the introduction of local symmetry from the corner of the layer. The controllability of the rotation angle is insufficient. The application of the device proposes an incredible challenge, and it also puts forward an urgent need for the large -scale non -rotating -angle -electrical off -sideways that explore and design a large -scale non -rotating surface.

Significance and exploration process

Recently, the research team of Professor Ji Wei of the Department of Physics of Renmin University of China and the experimental cooperation team at home and abroad found the iron electricality in the two -layer MOS2/WS2 heterogeneous knot in the non -turning corner, and showed the iron and electric tunnel knot. High -opening comparison capabilities, the iron electrical film was successfully reduced to 1 NM scale.

Figure 1. MOS2/WS2 dual -layer heterogeneous knot (A) Double -layer heterogeneous optical microscopy image (b) two different stack structures corresponding to two different stacking structures corresponding to two different stacks (c) Plane SEM Images, the area of ​​the two yellow rectangular boxes corresponds to the (D-E) horizontal cross-section scanning transmission electron microscopy image specific. They use chemical gas deposition method (CVD) to grow. MOS2/WS2 heterogeneous knot. This heterogeneous knot also has two stacking structures: 2H and 3R, which breaks the disappearance of the two -layer film. The measurement results of the voltage power microscope (PFM) indicate that the material has the iron electricality of the surface, and the obvious iron electrical delay linearity is displayed in the measurement of the external field direction (see Figure 2). -2.09 PM/V, this value is about 6 times the single layer of α-in2se3 values ​​with the highest surface of the two-dimensional iron electrical material in the previous two-dimensional iron electrical material.

Figure 2. MOS2/WS2 double -layer heterogeneous knot (A) (d) the electrical stagnation line obtained by the voltage power microscope when the DC electric field is turned off and turns on (B) (E) the measurement of the voltage power microscope obtained The phase diagram and amplitude diagram (C) (f) the tunnel through the tunnel through the different polarization state -DC partial pressure relationship and its iron electric tunnel penetration model diagram

In addition, the iron -electrical film is also constructed into an iron -electric tunnel knot, showing a 103 -dimensional switch ratio. The first principles of the principles set up a double -layer heterogeneous knot with the same stacking structure as the experiment, explored the calculation method of reliable two -dimensional material surface, and obtained the calculation value of 2.28 ~ 2.40 pm/v, and as the experimental results with the experimental results Highly consistent. The calculation results show that the non -zero -polarization intensity of the noodles in the double -layer heterogeneous knot comes from intervertebral charge transfer (see Figure 3), and under the induction of the electric field, only the power of 16 MEV/F.U needs to be overcome. Compared with the atomic sliding in the surface, the direction of interlayer charging can be changed to achieve a polarized direction flip, indicating that this heterogeneity is a kind of iron -electrical film material.

Figure 3. MOS2/WS2 Double-layer heterogeneous micro-sources (A) The structural schematic diagram (B-C) before slipping before slipping (D-F) surface (D-F) Sliding structure after slippery and intervertebral charges transfer diagram

The research work does not need to use complex corner regulation to achieve macro -iron electricality in the non -rotating two -dimensional heterogeneity. It provides a new way to prepare high -performance QRECE materials for high -performance two -dimensional iron electrical materials, which has opened up. New members of the Two -dimensional Railway Materials Family.

"Science" science again!

The research results were published on May 27 with the title of "Ferroelectronicity in Untwisted Heterobilayers of Transition Metal Dichalcogenides" as the title in the Science journal. Common author of the paper. Professor Ji Wei of the Department of Physics, Professor Liu Shiping of Hong Kong Polytechnic University, and Professor Manish Chhowalla of Cambridge University in the United Kingdom as the communication author of the paper. The theoretical calculation part of the work is completed by Renmin University of China, and the experimental part is completed by the cooperation unit. The work completed at Renmin University has been funded by the National Key R & D Plan, the National Natural Science Foundation of China, the basic scientific research business fee of the central university, the strategic research project of the Chinese Academy of Sciences, and the Renmin University of China Scientific Research Fund.

It is reported that this is the third time that the Teachers of the People's Congress as (common) communication authors published original research papers in the journal of Science (REPORTS and Research Article), and the first two also came from the Department of Physics. After more than ten years of construction, the Department of Physics has initially built a base for the cultivation and scientific research base with important influence at home and abroad, and has two undergraduate majors, a PhD in physics first discipline, 3 The doctoral point of the second -level discipline and the corresponding master's degree, two innovation teams in the Ministry of Education and a key laboratory in Beijing. He has won 1 National Natural Science Science Award, First Prize of Natural Sciences of the Ministry of Education, Ye Enterprise Sun Physics, and International Bourin Awards. There are 37 teachers in the post college, including 1 academician of dual -hired academicians, 2 selected for the national high -level talent award plan, and 9 national youth talent programs or fund selected. The Department of Physics was approved by the “national first -class undergraduate majors” construction point, and was selected as a national basic discipline top student training plan 2.0 base. About 70%of undergraduate graduates enter first -class universities at home and abroad to continue their master's and doctoral degrees. 66%of doctoral graduates are employed by double -class universities or Chinese Academy of Sciences. Essence

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Source: Department of Physics, Academy

Design: Yi Ran Gu Xiaobai

School pair: Sun Kun

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