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    Moiré Fringe Method via Scanning Transmission Electron Microscopy
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    Abstract:
    Abstract Moiré fringe, originated from the beating of two sets of lattices, is a commonly observed phenomenon in physics, optics, and materials science. Recently, a new method of creating moiré fringe via scanning transmission electron microscopy (STEM) has been developed to image materials’ structures at a large field of view. Moreover, this method shows great advantages in studying atomic structures of beam sensitive materials by significantly reduced electron dose. Here, the development of the STEM moiré fringe (STEM‐MF) method is reviewed. The authors first introduce the theory of STEM‐MF and then discuss the advances of this technique in combination with geometric phase analysis, annular bright field imaging, energy dispersive X‐ray spectroscopy, and electron energy loss spectroscopy. Applications of STEM‐MF on strain, defects, 2D materials, and beam‐sensitive materials are further summarized. Finally, the authors′ perspectives on the future directions of STEM‐MF are presented.
    Keywords:
    Moiré pattern
    Recent advances in electron microscopy techniques have led to a significant scale up in volumetric imaging of biological tissue. The throughput of electron microscopes, however, remains a limiting factor for the volume that can be imaged in high resolution within reasonable time. Faster detection methods will improve throughput. Here, we have characterized and benchmarked a novel detection technique for scanning electron microscopy: optical scanning transmission electron microscopy (OSTEM). A qualitative and quantitative comparison was performed between OSTEM, secondary and backscattered electron detection and annular dark field detection in scanning transmission electron microscopy. Our analysis shows that OSTEM produces images similar to backscattered electron detection in terms of contrast, resolution and signal-to-noise ratio. OSTEM can complement large scale imaging with (scanning) transmission electron microscopy and has the potential to speed up imaging in single-beam scanning electron microscope.
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    Abstract Recent developments in transmission electron microscopy (TEM) sample preparation have greatly reduced the time and cost for preparing thin samples. In this paper, a method is demonstrated for viewing thin samples in transmission in an unmodified scanning electron microscope (SEM) using an easily constructed sample holder. Although not a substitute for true TEM analysis, this method allows for spatial resolution that is superior to typical SEM imaging and provides image contrast from material structure that is typical of TEM images. Furthermore, the method can produce extremely high resolution x-ray maps that are typically produced only by scanning transmission electron microscope (STEM) systems.
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    The chapter contains sections titles: Introduction Scanning Transmission Electron Microscopy Imaging Modes Scanning Transmission Electron Microscopy Theory Inelastic Scattering and Secondary Radiations Conver gent-Beam and Nanodiffraction Coherent Nanodiffraction, Electron Holography, Ptychology Holography STEM Instrumentation Applications of Scanning Transmission Electron Microscopy References
    Electron holography
    Abstract Transmission electron microscopy (TEM) with low-energy electrons has been recognized as an important addition to the family of electron microscopies as it may avoid knock-on damage and increase the contrast of weakly scattering objects. Scanning electron microscopes (SEMs) are well suited for low-energy electron microscopy with maximum electron energies of 30 keV, but they are mainly used for topography imaging of bulk samples. Implementation of a scanning transmission electron microscopy (STEM) detector and a charge-coupled-device camera for the acquisition of on-axis transmission electron diffraction (TED) patterns, in combination with recent resolution improvements, make SEMs highly interesting for structure analysis of some electron-transparent specimens which are traditionally investigated by TEM. A new aspect is correlative SEM, STEM, and TED imaging from the same specimen region in a SEM which leads to a wealth of information. Simultaneous image acquisition gives information on surface topography, inner structure including crystal defects and qualitative material contrast. Lattice-fringe resolution is obtained in bright-field STEM imaging. The benefits of correlative SEM/STEM/TED imaging in a SEM are exemplified by structure analyses from representative sample classes such as nanoparticulates and bulk materials.
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    We demonstrate that high-angle annular dark-field imaging in scanning transmission electron microscopy allows for quantification of the number and location of all atoms in a three-dimensional, crystalline, arbitrarily shaped specimen without the need for a calibration standard. We show that the method also provides for an approach to directly measure the finite effective source size of a scanning transmission electron microscope.
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    The prelims comprise: Introduction Scanning Transmission Electron Microscopy Imaging Modes Scanning Transmission Electron Microscopy Theory Inelastic Scattering and Secondary Radiations Conver gent-Beam and Nanodiffraction Coherent Nanodiffraction, Electron Holography, Ptychology Holography STEM Instrumentation Applications of Scanning Transmission Electron Microscopy References
    Electron holography
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