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Tsang CS, Zheng X, Ly TH, Zhao J. Recent progresses in transmission electron microscopy studies of two-dimensional ferroelectrics. Micron 2024; 185:103678. [PMID: 38941681 DOI: 10.1016/j.micron.2024.103678] [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: 04/19/2024] [Revised: 06/03/2024] [Accepted: 06/13/2024] [Indexed: 06/30/2024]
Abstract
The rich potential of two-dimensional materials endows them with superior properties suitable for a wide range of applications, thereby attracting substantial interest across various fields. The ongoing trend towards device miniaturization aligns with the development of materials at progressively smaller scales, aiming to achieve higher integration density in electronics. In the realm of nano-scaling ferroelectric phenomena, numerous new two-dimensional ferroelectric materials have been predicted theoretically and subsequently validated through experimental confirmation. However, the capabilities of conventional tools, such as electrical measurements, are limited in providing a comprehensive investigation into the intrinsic origins of ferroelectricity and its interactions with structural factors. These factors include stacking, doping, functionalization, and defects. Consequently, the progress of potential applications, such as high-density memory devices, energy conversion systems, sensing technologies, catalysis, and more, is impeded. In this paper, we present a review of recent research that employs advanced transmission electron microscopy (TEM) techniques for the direct visualization and analysis of ferroelectric domains, domain walls, and other crucial features at the atomic level within two-dimensional materials. We discuss the essential interplay between structural characteristics and ferroelectric properties on the nanoscale, which facilitates understanding of the complex relationships governing their behavior. By doing so, we aim to pave the way for future innovative applications in this field.
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Affiliation(s)
- Chi Shing Tsang
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China; Department of Chemistry and Center of Super-Diamond & Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong, China
| | - Xiaodong Zheng
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China
| | - Thuc Hue Ly
- Department of Chemistry and Center of Super-Diamond & Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong, China; Department of Chemistry and State Key Laboratory of Marine Pollution, City University of Hong Kong, Hong Kong, China; City University of Hong Kong Shenzhen Research Institute, Shenzhen, China.
| | - Jiong Zhao
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, China; The Research Institute for Advanced Manufacturing, The Hong Kong polytechnic University, Hong Kong, China.
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Martis J, Susarla S, Rayabharam A, Su C, Paule T, Pelz P, Huff C, Xu X, Li HK, Jaikissoon M, Chen V, Pop E, Saraswat K, Zettl A, Aluru NR, Ramesh R, Ercius P, Majumdar A. Imaging the electron charge density in monolayer MoS 2 at the Ångstrom scale. Nat Commun 2023; 14:4363. [PMID: 37474521 PMCID: PMC10359339 DOI: 10.1038/s41467-023-39304-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 06/06/2023] [Indexed: 07/22/2023] Open
Abstract
Four-dimensional scanning transmission electron microscopy (4D-STEM) has recently gained widespread attention for its ability to image atomic electric fields with sub-Ångstrom spatial resolution. These electric field maps represent the integrated effect of the nucleus, core electrons and valence electrons, and separating their contributions is non-trivial. In this paper, we utilized simultaneously acquired 4D-STEM center of mass (CoM) images and annular dark field (ADF) images to determine the projected electron charge density in monolayer MoS2. We evaluate the contributions of both the core electrons and the valence electrons to the derived electron charge density; however, due to blurring by the probe shape, the valence electron contribution forms a nearly featureless background while most of the spatial modulation comes from the core electrons. Our findings highlight the importance of probe shape in interpreting charge densities derived from 4D-STEM and the need for smaller electron probes.
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Affiliation(s)
- Joel Martis
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Sandhya Susarla
- The National Center for Electron Microscopy (NCEM), The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, USA
| | - Archith Rayabharam
- Department of Mechanical Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Cong Su
- Department of Physics, University of California Berkeley, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA
- Kavli Energy NanoScience Institute, University of California Berkeley, Berkeley, CA, USA
| | - Timothy Paule
- Department of Physics, University of California Berkeley, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA
- Kavli Energy NanoScience Institute, University of California Berkeley, Berkeley, CA, USA
| | - Philipp Pelz
- The National Center for Electron Microscopy (NCEM), The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Cassandra Huff
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Xintong Xu
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Hao-Kun Li
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Marc Jaikissoon
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Victoria Chen
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Eric Pop
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Krishna Saraswat
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Alex Zettl
- Department of Physics, University of California Berkeley, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA
- Kavli Energy NanoScience Institute, University of California Berkeley, Berkeley, CA, USA
| | - Narayana R Aluru
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA
| | - Ramamoorthy Ramesh
- Department of Physics, University of California Berkeley, Berkeley, CA, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA
| | - Peter Ercius
- The National Center for Electron Microscopy (NCEM), The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Arun Majumdar
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
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Xiao Y, Xiong C, Chen MM, Wang S, Fu L, Zhang X. Structure modulation of two-dimensional transition metal chalcogenides: recent advances in methodology, mechanism and applications. Chem Soc Rev 2023; 52:1215-1272. [PMID: 36601686 DOI: 10.1039/d1cs01016f] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Together with the development of two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) have become one of the most popular series of model materials for fundamental sciences and practical applications. Due to the ever-growing requirements of customization and multi-function, dozens of modulated structures have been introduced in TMDs. In this review, we present a systematic and comprehensive overview of the structure modulation of TMDs, including point, linear and out-of-plane structures, following and updating the conventional classification for silicon and related bulk semiconductors. In particular, we focus on the structural characteristics of modulated TMD structures and analyse the corresponding root causes. We also summarize the recent progress in modulating methods, mechanisms, properties and applications based on modulated TMD structures. Finally, we demonstrate challenges and prospects in the structure modulation of TMDs and forecast potential directions about what and how breakthroughs can be achieved.
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Affiliation(s)
- Yao Xiao
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Chengyi Xiong
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Miao-Miao Chen
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Shengfu Wang
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
| | - Lei Fu
- The Institute for Advanced Studies (IAS), Wuhan University, Wuhan 430072, P. R. China. .,College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China.
| | - Xiuhua Zhang
- Collaborative Innovation Centre for Advanced Organic Chemical Materials Co-Constructed by the Province and Ministry, Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, College of Chemistry and Chemical Engineering, Hubei University, Wuhan 430062, P. R. China.
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ab initio description of bonding for transmission electron microscopy. Ultramicroscopy 2021; 231:113253. [PMID: 33773844 DOI: 10.1016/j.ultramic.2021.113253] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 02/12/2021] [Accepted: 02/20/2021] [Indexed: 01/10/2023]
Abstract
The simulation of transmission electron microscopy (TEM) images or diffraction patterns is often required to interpret their contrast and extract specimen features. This is especially true for high-resolution phase-contrast imaging of materials, but electron scattering simulations based on atomistic models are widely used in materials science and structural biology. Since electron scattering is dominated by the nuclear cores, the scattering potential is typically described by the widely applied independent atom model. This approximation is fast and fairly accurate, especially for scanning TEM (STEM) annular dark-field contrast, but it completely neglects valence bonding and its effect on the transmitting electrons. However, an emerging trend in electron microscopy is to use new instrumentation and methods to extract the maximum amount of information from each electron. This is evident in the increasing popularity of techniques such as 4D-STEM combined with ptychography in materials science, and cryogenic microcrystal electron diffraction in structural biology, where subtle differences in the scattering potential may be both measurable and contain additional insights. Thus, there is increasing interest in electron scattering simulations based on electrostatic potentials obtained from first principles, mainly via density functional theory, which was previously mainly required for holography. In this Review, we discuss the motivation and basis for these developments, survey the pioneering work that has been published thus far, and give our outlook for the future. We argue that a physically better justified ab initio description of the scattering potential is both useful and viable for an increasing number of systems, and we expect such simulations to steadily gain in popularity and importance.
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Blackburn AM, McLeod RA. Practical implementation of high-resolution electron ptychography and comparison with off-axis electron holography. Microscopy (Oxf) 2020; 70:131-147. [PMID: 32986121 DOI: 10.1093/jmicro/dfaa055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/04/2020] [Accepted: 09/14/2020] [Indexed: 11/13/2022] Open
Abstract
Ptychography is a coherent diffractive imaging technique that can determine how an electron wave is transmitted through an object by probing it in many small overlapping regions and processing the diffraction data obtained at each point. The resulting electron transmission model describes both phase and amplitude changes to the electron wave. Ptychography has been adopted in transmission electron microscopy in recent years following advances in high-speed direct electron detectors and computer algorithms which now make the technique suitable for practical applications. Its ability to retrieve quantitative phase information at high spatial resolution makes it a plausible alternative or complement to electron holography. Furthermore, unlike off-axis electron holography, it can provide phase information without an electron bi-prism assembly or the requirement of a minimally structured region adjacent to the region of interest in the object. However, it does require a well-calibrated scanning transmission electron microscope and a well-managed workflow to manage the calibration, data acquisition and reconstruction process to yield a practical technique. Here we detail this workflow and highlight how this is greatly assisted by acquisition management software. Through experimental data and modelling we also explore the similarities and differences between high-resolution ptychography and electron holography. Both techniques show a dependence of the recovered phase on the crystalline orientation of the material which is attributable to dynamical scattering. However, the exact nature of the variation differs reflecting fundamental expectations, but nonetheless equally useful information is obtained from electron holography and the ptychographically determined object transmission function.
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Affiliation(s)
- Arthur M Blackburn
- Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada
| | - Robert A McLeod
- Nano Accessories Product Group, Hitachi High Technologies Canada, Inc., Etobicoke, ON M9W 6A4, Canada
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