• Title, Summary, Keyword: transmission electron microscope

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Applications of the Scanning Electron Microscope (주사형(走査型) 전자현미경(電子顯微鏡)의 응용분야(應用分野))

  • Kim, Yong-Nak
    • Applied Microscopy
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    • v.2 no.1
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    • pp.39-46
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    • 1972
  • There are many kinds of microscopes suitable for general studies; optical microscopes(OM), conventional transmission electron microscopes (TEM), and scanning electron microscopes(SEM). The optical microscopes and the conventional transmission electron microscopes are very familiar. The images of these microscopes are directly formed on an image plane with one or more image forming lenses. On the other hand, the image of the scanning electron microscope is formed on a fluorescent screen of a cathode ray tube using a scanning system similar to television technique. In this paper, the features and some applications of the scanning electron microscope will be discussed briefly. The recently available scanning electron microscope, combining a resolution of about $200{\AA}$ with great depth of field, is favorable when compared to the replica technique. It avoids the problem of specimen damage and the introduction of artifacts. In addition, it permits the examination of many samples that can not be replicated, and provides a broader range of information. The scanning electron microscope has found application in diverse fields of study including biology, chemistry, materials science, semiconductor technology, and many others. In scanning electron microscopy, the secondary electron method. the backscattererd electron method, and the electromotive force method are most widely used, and the transmitted electron method will become more useful. Change-over of magnification can be easily done by controlling the scanning width of the electron probe. It is possible. to continuously vary the magnification over the range from 100 times to 1.00,000 times without readjustment of focusing. Conclusion: With the development of a scanning. electron microscope, it is now possible to observe almost all-information produced through interactions between substances and electrons in the form of image. When the probe is properly focused on the specimen, changing magnification of specimen orientation does not require any change in focus. This is quite different from the conventional transmission electron microscope. It is worthwhile to note that the typical probe currents of $10^{-10}$ to $10^{-12}\;{\AA}$ are for below the $10^{-5}$ to $10^{-7}\;{\AA}$ of a conventional. transmission microscope. This reduces specimen contamination and specimen damage due to heatings. Outstanding features of the scanning electron microscope include the 'stereoscopic observation of a bulky or fiber specimen in high resolution' and 'observation of potential distribution and electromotive force in semiconductor devices'.

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Hole Defects on Two-Dimensional Materials Formed by Electron Beam Irradiation: Toward Nanopore Devices

  • Park, Hyo Ju;Ryu, Gyeong Hee;Lee, Zonghoon
    • Applied Microscopy
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    • v.45 no.3
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    • pp.107-114
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    • 2015
  • Two-dimensional (2D) materials containing hole defects are a promising substitute for conventional nanopore membranes like silicon nitride. Hole defects on 2D materials, as atomically thin nanopores, have been used in nanopore devices, such as DNA sensor, gas sensor and purifier at lab-scale. For practical applications of 2D materials to nanopore devices, researches on characteristics of hole defects on graphene, hexagonal boron nitride and molybdenum disulfide have been conducted precisely using transmission electron microscope. Here, we summarized formation, features, structural preference and stability of hole defects on 2D materials with atomic-resolution transmission electron microscope images and theoretical calculations, emphasizing the future challenges in controlling the edge structures and stabilization of hole defects. Exploring the properties at the local structure of hole defects through in situ experiments is also the important issue for the fabrication of realistic 2D nanopore devices.

Anatomical Observation of Somatic Embryogenesis in Oenanthe javanica ($B^{L}.$) DC. (미나리 체세포 배발생과정의 해부학적 관찰)

  • Gab Cheon KOH;Chang Soon AHN
    • Korean Journal of Plant Tissue Culture
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    • v.22 no.6
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    • pp.323-327
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    • 1995
  • This experiment was carried out to observe the origin and developmental pattern of somatic embryos of Oenanthe javanica ($B^{L}.$) DC. The experiment included observation of embryogenic cells and their development stages by light microscope, transmission electron microscope and scanning electron microscope. The embryogenic cells, which were smaller than non-embryogenic cells in size with expanded nucleus and dense cytoplasm. When stained with hematoxylin, the embryogenic cells were readily distinguished from the non-embryogenic cells of which cell walls were stained with safranin. It was observed at somatic embryos developed from single cells on the epidermis of developing embryos or in the surface or inside of embryogenic clumps by segmentation pattern. Observation with a transmission electron microscope revealed that the embryogenic cells had dense cytoplasm expanded nucleus, small vacuoles, large amyloplasts containing starch grains, and abundant organelles including lipid bodies. Under a scanning electron microscope, embryogenic callus was shown to consist of very smaller cells than non-embryogenic cells in an orderly arrangement and covered with a net-like structure, while the non-embryogenic callus consisted of large cells, irregular in size and arrangement, and covered with a gelatin-like material.

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Transmission Electron Microscope Specimen Preparation of Si-Based Anode Materials for Li-Ion Battery by Using Focused Ion Beam and Ultramicrotome

  • Chae, Jeong Eun;Yang, Jun Mo;Kim, Sung Soo;Park, Ju Cheol
    • Applied Microscopy
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    • v.48 no.2
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    • pp.49-53
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    • 2018
  • A successful transmission electron microscope (TEM) analysis is closely related to the preparation of the TEM specimen and should be followed by the suitable TEM specimen preparation depending on the purpose of analysis and the subject materials. In the case of the Si-based anode material, lithium atoms of formed Li silicide were removed due to ion beam and electron beam during TEM specimen preparation and TEM observation. To overcome the problem, we proposed a new technique to make a TEM specimen without the ion beam damage. In this study, two types of test specimens from the Si-based anode material of Li-ion battery were prepared by respectively adopting the only focused ion beam (FIB) method and the new FIB-ultramicrotome method. TEM analyses of two samples were conducted to compare the Ga ion damage of the test specimen.

Precise Analysis of the Surface Oxidation Layer on Cu Powders Using FE-TEM Techniques (전계방출 투과전자현미경 분석기술을 이용한 Cu 입자 표면산화층의 정밀평가)

  • Lee, Tae Hun;Yoo, Jung Ho;Hyun, Moon Seop;Yang, Jun-Mo;Seong, Mi-Ryn;Kwon, Jinhyeong;Lee, Caroline Sunyong;Kim, Jeong-Sun;Baik, Kyeong Ho
    • Korean Journal of Metals and Materials
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    • v.48 no.1
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    • pp.57-61
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    • 2010
  • Nanosized surface structures of Cu powders were investigated at the atomic scale by field-emission transmission electron microscope techniques. The nanoscale surface oxide layer on the Cu powder was analyzed to be the $CU_2O$ phase by electron diffraction pattern and electron energy-loss spectroscopy. In addition, it was found from high-resolution transmission electron microscopy study that there are formed no surface oxide layers on the surface of alkanethiol coated Cu powders.

NANO-STRUCTURAL AND NANO-CHEMICAL ANALYSIS OF NI-BASE ALLOY/LOW ALLOY STEEL DISSIMILAR METAL WELD INTERFACES

  • Choi, Kyoung-Joon;Shin, Sang-Hun;Kim, Jong-Jin;Jung, Ju-Ang;Kim, Ji-Hyun
    • Nuclear Engineering and Technology
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    • v.44 no.5
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    • pp.491-500
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    • 2012
  • The dissimilar metal joints welded between Ni-based alloy, Alloy 690 and low alloy steel, A533 Gr. B with Alloy 152 filler metal were characterized by using optical microscope, scanning electron microscope, transmission electron microscope, secondary ion mass spectrometry and 3-dimensional atom probe tomography. It was found that in the weld root region, the weld was divided into several regions including unmixed zone in Ni-base alloy, fusion boundary, and heat-affected zone in the low alloy steel. The result of nanostructural and nanochemical analyses in this study showed the non-homogeneous distribution of elements with higher Fe but lower Mn, Ni and Cr in A533 Gr. B compared with Alloy 152, and the precipitation of carbides near the fusion boundary.

Formation Dynamics of Carbon Atomic Chain from Graphene by Electron Beam Irradiation

  • Park, Hyo Ju;Lee, Zonghoon
    • Applied Microscopy
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    • v.48 no.4
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    • pp.126-127
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    • 2018
  • Carbon has numerous allotropes and various crystalline forms with full dimensionalities such as diamond, graphite, fullerenes, and carbon nanotubes leading a wide range of applications. Since the emerge of graphene consisting of a single atomic layer of carbon atoms, a fabrication of all-carbon-based device with combination of one-, two-, and three-dimensional carbons has become a hot issue. Here, we introduce an ultimate one-dimensional carbon atomic chain. Carbon atomic chains were experimentally created by removing atoms from monolayer graphene sheet under electron beam inside transmission electron microscope (TEM). A series of TEM images demonstrate the dynamics of carbon atomic chains over time from the formation, transformation, and then breakage.

Principles and Analysis of Electron Diffraction Patterns in Transmission Electron Microscopy : Utilization of Microcomputers (전자회절도형의 원리와 분석 : Microcomputer의 이용)

  • Sung, Chang-Mo
    • Applied Microscopy
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    • v.21 no.1
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    • pp.108-120
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    • 1991
  • Principles of electron diffraction patterns in transmission electron microscope are described for beginners in terms of reciprocal lattices and Ewald sphere. Analysis of both ring patterns and spot patterns are illustrated with practical examples as well as basic calibrations of TEM. Especially convergent beam electron diffraction method is emphasized for the determination of lattice parameters, microstrains, and thickness of thin foil followed by a review of microcomputer programs for the electron diffraction analyses explained in this paper.

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