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Grieb T, Krause FF, Mehrtens T, Mahr C, Gerken B, Schowalter M, Freitag B, Rosenauer A. GaN atomic electric fields from a segmented STEM detector: Experiment and simulation. J Microsc 2024; 295:140-146. [PMID: 38372408 DOI: 10.1111/jmi.13276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 01/31/2024] [Indexed: 02/20/2024]
Abstract
Atomic electric fields in a thin GaN sample are measured with the centre-of-mass approach in 4D-scanning transmission electron microscopy (4D-STEM) using a 12-segmented STEM detector in a Spectra 300 microscope. The electric fields, charge density and potential are compared to simulations and an experimental measurement using a pixelated 4D-STEM detector. The segmented detector benefits from a high recording speed, which enables measurements at low radiation doses. However, there is measurement uncertainty due to the limited number of segments analysed in this study.
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Affiliation(s)
- Tim Grieb
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Florian F Krause
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Thorsten Mehrtens
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Christoph Mahr
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Beeke Gerken
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Marco Schowalter
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Bert Freitag
- Thermo Fisher Scientific, Eindhoven, The Netherlands
| | - Andreas Rosenauer
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
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2
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Groll M, Bürger J, Caltzidis I, Jöns KD, Schmidt WG, Gerstmann U, Lindner JKN. DFT-Assisted Investigation of the Electric Field and Charge Density Distribution of Pristine and Defective 2D WSe 2 by Differential Phase Contrast Imaging. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2311635. [PMID: 38703033 DOI: 10.1002/smll.202311635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 04/02/2024] [Indexed: 05/06/2024]
Abstract
Most properties of solid materials are defined by their internal electric field and charge density distributions which so far are difficult to measure with high spatial resolution. Especially for 2D materials, the atomic electric fields influence the optoelectronic properties. In this study, the atomic-scale electric field and charge density distribution of WSe2 bi- and trilayers are revealed using an emerging microscopy technique, differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). For pristine material, a higher positive charge density located at the selenium atomic columns compared to the tungsten atomic columns is obtained and tentatively explained by a coherent scattering effect. Furthermore, the change in the electric field distribution induced by a missing selenium atomic column is investigated. A characteristic electric field distribution in the vicinity of the defect with locally reduced magnitudes compared to the pristine lattice is observed. This effect is accompanied by a considerable inward relaxation of the surrounding lattice, which according to first principles DFT calculation is fully compatible with a missing column of Se atoms. This shows that DPC imaging, as an electric field sensitive technique, provides additional and remarkable information to the otherwise only structural analysis obtained with conventional STEM imaging.
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Affiliation(s)
- Maja Groll
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Julius Bürger
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Ioannis Caltzidis
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Klaus D Jöns
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Wolf Gero Schmidt
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Uwe Gerstmann
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
| | - Jörg K N Lindner
- Department of Physics, University of Paderborn, Warburger Straße 100, 33098, Paderborn, Germany
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Chao HY, Venkatraman K, Moniri S, Jiang Y, Tang X, Dai S, Gao W, Miao J, Chi M. In Situ and Emerging Transmission Electron Microscopy for Catalysis Research. Chem Rev 2023. [PMID: 37327473 DOI: 10.1021/acs.chemrev.2c00880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Catalysts are the primary facilitator in many dynamic processes. Therefore, a thorough understanding of these processes has vast implications for a myriad of energy systems. The scanning/transmission electron microscope (S/TEM) is a powerful tool not only for atomic-scale characterization but also in situ catalytic experimentation. Techniques such as liquid and gas phase electron microscopy allow the observation of catalysts in an environment conducive to catalytic reactions. Correlated algorithms can greatly improve microscopy data processing and expand multidimensional data handling. Furthermore, new techniques including 4D-STEM, atomic electron tomography, cryogenic electron microscopy, and monochromated electron energy loss spectroscopy (EELS) push the boundaries of our comprehension of catalyst behavior. In this review, we discuss the existing and emergent techniques for observing catalysts using S/TEM. Challenges and opportunities highlighted aim to inspire and accelerate the use of electron microscopy to further investigate the complex interplay of catalytic systems.
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Affiliation(s)
- Hsin-Yun Chao
- Center for Nanophase Materials Sciences, One Bethel Valley Road, Building 4515, Oak Ridge, Tennessee 37831-6064, United States
| | - Kartik Venkatraman
- Center for Nanophase Materials Sciences, One Bethel Valley Road, Building 4515, Oak Ridge, Tennessee 37831-6064, United States
| | - Saman Moniri
- Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Yongjun Jiang
- Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, China
| | - Xuan Tang
- Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, China
| | - Sheng Dai
- Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, China
| | - Wenpei Gao
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jianwei Miao
- Department of Physics and Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Miaofang Chi
- Center for Nanophase Materials Sciences, One Bethel Valley Road, Building 4515, Oak Ridge, Tennessee 37831-6064, United States
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Seki T, Khare K, Murakami YO, Toyama S, Sánchez-Santolino G, Sasaki H, Findlay SD, Petersen TC, Ikuhara Y, Shibata N. Linear imaging theory for differential phase contrast and other phase imaging modes in scanning transmission electron microscopy. Ultramicroscopy 2022; 240:113580. [DOI: 10.1016/j.ultramic.2022.113580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 11/17/2022]
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