In the 1930s, theoretical physicist Lev Landau theoretically proved that ideal 2D crystals (that is, suspended 2D crystals) are thermodynamically unstable. The most ideal 2D crystal is a suspended structure that completely eliminates any substrate support. Although researchers have a very clear understanding of the unique advantages of suspended 2D crystals, the preparation of suspended 2D crystals has been very challenging for a long time.

Recently, the team of Professor Huang Yuan and Wang Yeliang of Beijing Institute of Technology has achieved research results in the suspension structure of 2D materials, realizing the efficient preparation of suspended 2D materials. The team cooperated with Peking University, Renmin University of China, Institute of Physics, Chinese Academy of Sciences and Nanjing University, and published the title of An efficient route to prepare suspended monolayer for feasible optical and electronic characterizations of two-dimensional materials on InfoMat (DOI: 10.1002 /inf2.12274, impact factor 25.405).

Fig. 1 The preparation route of the suspended structure of 2D materials (a) and the 2D materials after cleavage (b-d). The suspended WSe2 after cleavage exhibits good fluorescence properties (e). (f) is the fluorescence imaging picture of suspended WSe2 prepared by optimizing the cleavage process after the substrate is patterned (zodiac pattern).

The researchers selectively removed part of the substrate material by patterning the substrate with a hole array. For different material systems, two preparation methods of 2D material suspension structures are proposed (Fig. 1). By means of Raman spectroscopy, fluorescence spectroscopy, low-energy electron diffraction, second-harmonic imaging, and transport measurements, it was systematically confirmed that the suspended structure has more excellent physical properties. This suspended 2D material does not conflict with Landau's theory, because the 2D material is fixed at a finite boundary, thus suppressing the thermodynamic instability of the 2D material. This work can be said to unlock the suspension code of two-dimensional materials, and more novel properties are expected to make breakthroughs in suspension structures, providing an ideal platform for studying more intrinsic physical properties.

In this study, Professor Huang Yuan of the Advanced Research of Multidisciplinary Sciences of Beijing Institute of Technology is the first author, and Researcher Gao Yunan, Professor Ji Wei, Zhou Xingjiang and Professor Wang Yeliang, Dean of the School of Integrated Circuits and Electronics, Beijing Institute of Technology are the co-corresponding authors.

Link to the paper:

https://onlinelibrary.wiley.com/doi/full/10.1002/inf2.12274

About the authors:

Huang Yuan, professor and doctoral supervisor of the Advanced Research of Multidisciplinary Sciences of Beijing Institute of Technology. The main research areas focus on the preparation, characterization, device processing and physical property measurement/regulation of 2D materials. He has published more than 70 SCI papers in Nature Physics, Nature Communications, Physical Review Letters, etc., including more than 30 articles by the first author (including one) and corresponding authors, with a total of more than 3,700 citations. He presided over the National Key R&D Program (Youth Project), the Outstanding Youth Fund and General Program of the National Foundation of China, and the Chongqing Outstanding Youth Fund Project. In 2019, he was selected as a member of the Youth Promotion Association of the Chinese Academy of Sciences. In 2020, he was awarded the honorary title of "China's Top Ten New Talents in Science and Technology" by the China Association for Science and Technology. He served as reviewer of Physical Review Letters, Nature Communications, Advanced Functional Materials, ACS Nano, Nano Letters, Journal of Physics and other well-known journals at home and abroad; he served as the young editorial board member of Physics, Chinese Physics Letters, Infomat and materials.

Wang Yeliang, professor, doctoral supervisor, dean of the School of Integrated Circuits and Electronics, Beijing Institute of Technology, Director of the Key Laboratory of Low-Dimensional Quantum Structures and Devices of the Ministry of Industry and Information Technology. He is a director of the Chinese Vacuum Society and a member of the Semiconductor Physics Professional Committee of the Chinese Physical Society, member of the 8th Academic Degree Committee of the State Council Disciplinary Evaluation Group, winner of Hu Gangfu Physics Prize of Chinese Physical Society. He has long been engaged in the preparation and application of new electronic materials and devices. The main research results include 1 paper in Nat. Matser., 1 paper in Nat. Elect., 1 paper in Nat. Phys., 3 papers in Nat. Commun., 5 papers in Adv. Mater., 6 papers in Nano Lett., 4 papers in ACS Nano, 2 papers in Phys. Rev. Lett., 3 papers in J. Am. Chem. Soc. His articles have been cited more than 8,000 times, of which a single paper has been cited more than 1,000 times. Many of his works have been reported by Nature and its sub-journals as research highlights. He has been invited to report more than 30 times in important international academic conferences. 18 national patents have been applied and 8 have been authorized. He undertakes the key research and development projects of the Ministry of Science and Technology, the National Outstanding Youth Fund Project/Key Project, and the Beijing Key Project.