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Köster J, Kretschmer S, Storm A, Rasper F, Kinyanjui MK, Krasheninnikov AV, Kaiser U. Phase transformations in single-layer MoTe 2stimulated by electron irradiation and annealing. NANOTECHNOLOGY 2024; 35:145301. [PMID: 38096582 DOI: 10.1088/1361-6528/ad15bb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 12/14/2023] [Indexed: 01/16/2024]
Abstract
Among two-dimensional (2D) transition metal dichalcogenides (TMDs), MoTe2is predestined for phase-engineering applications due to the small difference in free energy between the semiconducting H-phase and metallic 1T'-phase. At the same time, the complete picture of the phase evolution originating from point defects in single-layer of semiconducting H-MoTe2via Mo6Te6nanowires to cubic molybdenum has not yet been reported so far, and it is the topic of the present study. The occurring phase transformations in single-layer H-MoTe2were initiated by 40-80 kV electrons in the spherical and chromatic aberration-corrected high-resolution transmission electron microscope and/or when subjected to high temperatures. We analyse the damage cross-section at voltages between 40 kV and 80 kV and relate the results to previously published values for other TMDs. Then we demonstrate that electron beam irradiation offers a route to locally transform freestanding single-layer H-MoTe2into one-dimensional (1D) Mo6Te6nanowires. Combining the experimental data with the results of first-principles calculations, we explain the transformations in MoTe2single-layers and Mo6Te6nanowires by an interplay of electron-beam-induced energy transfer, atom ejection, and oxygen absorption. Further, the effects emerging from electron irradiation are compared with those produced byin situannealing in a vacuum until pure molybdenum crystals are obtained at temperatures of about 1000 °C. A detailed understanding of high-temperature solid-to-solid phase transformation in the 2D limit can provide insights into the applicability of this material for future device fabrication.
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Affiliation(s)
- Janis Köster
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Silvan Kretschmer
- Institut of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
| | - Alexander Storm
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Fabian Rasper
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Michael K Kinyanjui
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
| | - Arkady V Krasheninnikov
- Institut of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01328 Dresden, Germany
- Department of Applied Physics, Aalto University, PO Box 14100, FI-00076 Aalto, Finland
| | - Ute Kaiser
- Electron Microscopy Group of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany
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Zhao W, Xu WW, Jiang J, Zhao X, Duan X, Sun Y, Francisco JS, Zeng XC. Evidence of Formation of Monolayer Hydrated Salts in Nanopores. J Am Chem Soc 2022; 144:18976-18985. [PMID: 36197785 DOI: 10.1021/jacs.2c07372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Despite much effort being devoted to the study of ionic aqueous solutions at the nanoscale, our fundamental understanding of the microscopic kinetic and thermodynamic behaviors in these systems remains largely incomplete. Herein, we reported the first 10 μs molecular dynamics simulation, providing evidence of the spontaneous formation of monolayer hexagonal honeycomb hydrated salts of XCl2·6H2O (X = Ba, Sr, Ca, and Mg) from electrolyte aqueous solutions confined in an angstrom-scale slit under ambient conditions. By using both the classical molecular dynamics simulations and the first-principles Born-Oppenheimer molecular dynamics simulations, we further demonstrated that the hydrated salts were stable not only at ambient temperature but also at elevated temperatures. This phenomenon of formation of hydrated salt in water is contrary to the conventional view. The free energy calculations and dehydration analyses indicated that the spontaneous formation of hydrated salts can be attributed to the interplay between ion hydration and Coulombic attractions in the highly confined water. In addition to providing molecular-level insights into the novel behavior of ionic aqueous solutions at the nanoscale, our findings may have implications for the future exploration of potential existence of water molecules in the saline deposits on hot planets.
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Affiliation(s)
- Wenhui Zhao
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Wen Wu Xu
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Jian Jiang
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.,Department of Materials Science & Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Xiaorong Zhao
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Xiangmei Duan
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Yunxiang Sun
- Department of Physics, Ningbo University, Ningbo 315211, China
| | - Joseph S Francisco
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Xiao Cheng Zeng
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.,Department of Materials Science & Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
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Yuan B, Hua Z, Jia S, Lu Y, Shi E, Yu Y. Graphene protection improves the stability of two-dimensional halide perovskites under the electron irradiation. Microsc Res Tech 2022; 85:3582-3588. [PMID: 35880591 DOI: 10.1002/jemt.24209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/09/2022] [Accepted: 07/09/2022] [Indexed: 11/10/2022]
Abstract
The crystal structure of two-dimensional (2D) organic-inorganic halide perovskites undergoes fast structural collapse under the electron beam irradiation, hindering high-resolution transmission electron microscopy imaging. Graphene protection is an effective solution to mitigate the damage of electron-beam irradiation and has been applied in 2D materials such as MoS2 . However, the effectivity of graphene protection has not been demonstrated in 2D halide perovskites yet, as traditional wet-transfer of graphene with aqueous solution would cause serious degradation for moisture-sensitive halide perovskites. Here, we verified that graphene protection plays a protection role and developed a method using nonpolar solvent to transfer the graphene layer atop the perovskite nanosheets. With this method, the perovskite nanosheets might be well protected by graphene encapsulation. HIGHLIGHTS: Transfer method of graphene on moisture-sensitive 2D halide perovskites using nonpolar solvents was developed. Graphene substrate is proven to be able to mitigate electron-beam damage to 2D halide perovskites. Encapsulation structure of graphene/halide perovskite/graphene was demonstrated.
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Affiliation(s)
- Biao Yuan
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.,Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University, Shanghai, China
| | - Ziyi Hua
- School of Engineering, Westlake University, Hangzhou, China
| | - Shunhan Jia
- School of Engineering, Westlake University, Hangzhou, China.,CAS Key Laboratory of Colloid and Interface and Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Yuan Lu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.,Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University, Shanghai, China
| | - Enzheng Shi
- School of Engineering, Westlake University, Hangzhou, China
| | - Yi Yu
- School of Physical Science and Technology, ShanghaiTech University, Shanghai, China.,Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University, Shanghai, China
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