• Journal of the Korean Society for Precision Engineering
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• v.29 no.5
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• pp.554-562
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• 2012

Processing of Scanning electron microscope imaging has been analyzed in both secondary electron (SE) imaging and backscattered electron (BSE) image. Because of unique characteristics of both secondary electron and backscattered electron image, mechanism of imaging process and image quality are quite different each other. For the sake of characterize imaging process, Monte Carlo simulation code have been developed. It simulates electron penetration and depth profile in certain material. In addition, secondary electron and backscattered electron generation process as well as their spatial distribution and energy characteristics can be simulated. Geometries that has fundamental feature have been imaged using the developed Monte Carlo code. Two, SE and BSE images generation process will be discussed. BSE imaging process can be readily used to discriminate in both material and geometry by simply changing position and direction of BSE detector. The developed MC code could be useful to design BSE detector and their position. Furthermore, surface reconstruction technique is possibly developed at the further research efforts. Basics of Monte Carlo simulation method will be discussed as well as characteristics of SE and BSE images.

• Applied Microscopy
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• v.46 no.4
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• pp.244-252
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• 2016

This paper describes a new design of carbon nanotube tip. $Nanocly^{TM}$ NC 7000 Thin Multiwall Carbon Nanotubes of carbon purity (90%) and average diameter tube 9.5 nm with a high aspect-ratio (>150) were used. These tips were manufactured by employing a drawing technique using a glass puller. The glass microemitters with internal carbon nanotubes show a switch-on effect to a high current level (1 to $20{\mu}A$). A field electron microscope with a tip (cathode)-screen (anode) separation at ~10 mm was used to characterize the electron emitters. The system was evacuated down to a base pressure of ${\sim}10^{-9}$ mbar when baked at up to ${\sim}200^{\circ}C$ overnight. This allowed measurements of typical Field Electron Emission characteristics; namely the current-voltage (I-V) characteristics and the emission images on a conductive phosphorus screen (the anode). Fowler-Nordheim plots of the current-voltage characteristics show current switch-on for each of these emitters.

• Applied Microscopy
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• v.47 no.1
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• pp.55-62
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• 2017

This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.95-102
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• 2007

The scanning electron microscope (SEM) is one of the most popular instruments available for the measurement and analysis of the micro/nano structures. It is equipped with an electron optical system that consists of an electron beam source, magnetic lenses, apertures, deflection coils, and a detector. The magnetic lenses playa role in refracting electron beams to obtain a focused spot using the magnetic field driven by an electric current from a coil. A SEM column usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present work concerns finite element analysis for the electron magnetic lenses so as to analyze their magnetic characteristics. To improve the performance of the magnetic lenses, the effect of the excitation current and pole-piece design on the amount of resulting magnetic fields and their peak locations are analyzed through the finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.92-98
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• 2009

The scanning electron microscope (SEM) contains an electron optical system in which electrons are emitted and moved to form a focused beam, and generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present study covers the design and analysis of an objective lens for a thermionic SEM. A finite element (FE) analysis for the objective lens is performed to analyze its magnetic characteristics for various lens designs. Relevant beam trajectories are also investigated by tracing the ray path of the electron beams under the magnetic fields inside the objective lens.

• Development and Reproduction
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• v.17 no.2
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• pp.121-132
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• 2013

Ultrastructural characteristics of the germ cells and accessory cells in testis during spermatogenesis and taxonomic values of mature sperm morphology of Ruditapes philippinarum were investigated by the transmission electron microscope and scanning electron microscope observations. The testis is the diffuse organ that consists of branching acini containing developing germ cells and accessory cells associated with spermatogenesis. The morphology of the spermatozoon is of the primitive type and is somewhat different to those of other bivalves. The morphologies of the sperm nucleus type and the acrosome shape of this species have a cylinderical type and a modified cone shape, respectively. As some ultrastructural characteristics of the acrosomal vesicle, the peripheral parts of two basal rings show electron opaque part, while the apex part of the acrosome shows electron lucent part. These characteristics of sperm belong to the family Veneridae in the subclass Heterodonta, unlike a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part. In particular, a cylinder-like nucleus of the sperm is curved. The spermatozoon is approximately $48-51{\mu}m$ in length, including a long acrosome (about $2.4{\mu}m$ in length), a curved sperm nucleus (about $3.40{\mu}m$ in length), and a tail flagellum. The axoneme of the sperm tail shows a 9+2 structure.

• Applied Microscopy
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• v.46 no.4
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• pp.227-237
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• 2016

This investigation deals with the process of field electron emission from composite microemitters. Tested emitters consisted of a tungsten or carbon-fiber core, coated with a dielectric material. Two coating materials were used: (1) Clark Electromedical Instruments Epoxylite resin and (2) Epidian 6 Epoxy resin (based on bisphenol A). Various properties of these emitters were measured, including the current-voltage characteristics, which are presented as Fowler-Nordheim plots, and the corresponding electron emission images. A field electron microscope with a tip (cathode) to screen (anode) distance of 10 mm was used to electrically characterize the emitters. Measurements were carried out under ultra-high vacuum conditions with a base pressure of $10^{-6}$ Pascal ($10^{-8}$ mbar).

• Journal of Ginseng Research
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• v.25 no.2
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• pp.82-88
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• 2001

This study was carried out to investigate a point of difference between normal and inferior Korean red ginseng (Naeback red ginseng = red ginseng with white part of clear boundary in phloem and/or xylem of ginseng body, saengnaeback red ginseng red ginseng with white part of indistinct boundary). White part with clear or indistinct boundary in center of ginseng body was observed in inferior red ginseng (naeback and saengnaeback red ginseng), and the differences in the internal color intensity was also found with naked eye. In hunter color values of normal and inferior parts of red ginseng in accordance with particle size, L value was increased with a diminishment in particle size, while a and b value were decreased. Absorbance at visible spectrum did not differ from water and 70% ethanol extract from normal and inferior parts of red ginseng, but absorbance in UV spectrum of extract from naeback part showed higher than those of normal and saengnaeback part. In comparison of intrastructure by electron microscope, the horizontal and vertical section of cortex and pith layer from normal part showed the very dense state, but small holes were found in naeback part of red ginseng by naked eye and electron microscope. The specific surface area of normal, naeback and saengnaeback part appeared 3.02, 3.33 and 6.55 ㎡/g, respectively. From above results, we consider saengnaeback red ginseng is red ginseng in the intermediate process which normal red ginseng changes to naeback red ginseng.

• ALGAE
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• v.25 no.3
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• pp.121-131
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• 2010

Thalassiosira species were collected from October 2007 to January 2009 in an attempt to better understand species diversity of the genus Thalassiosira in Korean coastal waters. A total of 5 Thalassiosira species (T. concaviuscula, T. oceanica, T. partheneia, T. simonsenii and T. nanolineata) were identified here. Most species in this study were of small size, and 5 species were recorded for the first time in Korean coastal waters. Using a scanning electron microscope (SEM), we described distinctive characteristics of fine structure that proved to be important diagnostic characteristics for the identification of each species. The most important diagnostic characteristics for Thalassiosira species identification were the marginal strutted processes, the position of labiate processes, and the areolation. The differential characteristics of the species studied were: T. concaviuscula has a double layered external tubes on the marginal strutted processes; T. oceanica shows marginal ridges that are interlinked between the marginal strutted processes; the valve face of T. partheneia is fairly convex and its labiate process is positioned midway between two strutted processes; T. simonsenii is characterized by two labiate processes and somewhat coarse areolae; and, T. nanolineata has several central strutted processes and linear areolation.

• 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.