• Title/Summary/Keyword: Scanning Electron Microscope

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A Study on Design and Analysis for Magnetic Lenses of a Scanning Electron Microscope using Finite Element Method (유한요소법을 사용한 주사전자 현미경의 전자렌즈 설계 및 해석에 관한 연구)

  • Park, Keun;Jung, Hyun-Woo;Park, Man-Jin;Kim, Dong-Hwan;Jang, Dong-Young
    • 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.

The Behavior of Secondary Electrons and Optimal Mounting Position of a Secondary Electron Detector in SEM with a Numerical Analysis (수치해석을 통한 SEM 챔버내의 이차전자 거동해석 및 이차전자 검출기의 최적 장착 위치 선정)

  • Boo, Kyeung-Seok;Jeon, Jong-Up
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.4
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    • pp.15-21
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    • 2008
  • Secondary electron detectors used in scanning electron microscope accept secondary electrons emitted from the specimen and convert them to an electrical signal that, after amplification, is used to modulate the gray-level intensities on a cathode ray tube, producing an image of the specimen. In order to acquire images with good qualities, as many secondary electrons as possible should be reached to the detector. To realize this it is very important to select an appropriate mounting position and angle of the detector inside the chamber of scanning electron microscope. In this paper, a number of numerical simulations are performed to explore the relationships between detection rates of secondary electrons and the values of some parameters, such as distances between the detector and sample, relative mounting positions of scintillator positioned inside the detector with respect to detector cover, two types of mounting angles of the detector. The relationships between detection rates and applied voltages to corona ring and faraday cage, and energies of secondary electrons are investigated as well.

Performance evaluation of METAMIC neutron absorber in spent fuel storage rack

  • Kim, Kiyoung;Chung, Sunghwan;Hong, Junhee
    • Nuclear Engineering and Technology
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    • v.50 no.5
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    • pp.788-793
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    • 2018
  • High-density spent fuel (SF) storage racks have been installed to increase SF pool capacity. In these SF racks, neutron absorber materials were placed between fuel assemblies allowing the storage of fuel assemblies in close proximity to one another. The purpose of the neutron absorber materials is to preclude neutronic coupling between adjacent fuel assemblies and to maintain the fuel in a subcritical storage condition. METAMIC neutron absorber has been used in high-density storage racks. But, neutron absorber materials can be subject to severe conditions including long-term exposure to gamma radiation and neutron radiation. Recently, some of them have experienced degradation, such as white spots on the surface. Under these conditions, the material must continue to serve its intended function of absorbing neutrons. For the first time in Korea, this article uses a neutron attenuation test to examine the performance of METAMIC surveillance coupons. Also, scanning electron microscope analysis was carried out to verify the white spots that were detected on the surface of METAMIC. In the neutron attenuation test, there was no significant sign of boron loss in most of the METAMIC coupons, but the coupon with white spots had relatively less B-10 content than the others. In the scanning electron microscope analysis, corrosion material was detected in all METAMIC coupons. Especially, it was confirmed that the coupon with white spots contains much more corrosion material than the others.

Design and Analysis of an Objective Lens for a Scanning Electron Microscope by Coupling FE Analysis and Ray Tracing (유한요소해석과 광선추적을 연계한 주사전자 현미경 대물렌즈의 설계 및 해석)

  • Park, Keun;Lee, Jae-Jin;Park, Man-Jin;Kim, Dong-Hwan;Jang, Dong-Young
    • 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.

Mechanical Properties of Elastomer TPVs due to Injection Molding Conditions (엘라스토머 TPV의 사출성형조건에 따른 기계적 물성)

  • Han, Seong-Ryeol;Jeong, Yeong-Deug
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.5 no.1
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    • pp.27-32
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    • 2006
  • Thermoplastic elastomer(TPE) has many advantages such as high flexibility, high elasticity and high elongation, etc. TPE is easily molded as plastic materials, therefore, many TPE parts are applied as home appliances and mechanical parts. However, its mechanical properties would be changed by injection molding conditions such as melt temperature, mold temperature, injection pressure and holding pressure, etc. In this study, the influences of the injection molding condition on the mechanical properties as tensile strength, hardness of thermoplastic vulcanizates(TPVs), which is one of the TPE, were investigated. By the injection molding experiment, the molding's tensile strength and hardness was influenced on the melt temperature and composition ratio of PP and EPDM. The morphology of moldings were shown by the scanning electron microscope.

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Influence of Angle Ply Orientation on the Flexural Strength of Basalt and Carbon Fiber Reinforced Hybrid Composites

  • Mengal, Ali Nawaz;Karuppanan, Saravanan
    • Composites Research
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    • v.28 no.1
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    • pp.1-5
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    • 2015
  • In this paper the influence of fiber orientation of basalt and carbon inter-ply fabrics on the flexural properties of hybrid composite laminates was experimentally investigated. Four types of basalt/carbon/epoxy inter-ply hybrid composite laminates with varying angle ply orientation of reinforced basalt fiber and fixed orientation of carbon fiber were fabricated using hand lay-up technique. Three point bending test was performed according to ASTM 7264. The fracture surface analysis was carried out by scanning electron microscope (SEM). The results obtained from the four laminates were compared. Lay-up pattern of $[0B/+30B/-30B/0C]_S$ exhibits the best properties in terms of flexural strength and flexural modulus. Scanning electron microscopy results on the fracture surface showed that the interfacial de-bonding between the fibers and epoxy resin is a dominant fracture mode for all fiber lay-up schemes.

Fabrication and Linear & Nonlinear Optical Characterization of Photonic Crystals (포토닉 밴드갭 광결정의 제작과 선형 및 비선형 광학 특성 연구)

  • Ha Na Yeong;U Yeon Gyeong;Hwang Ji-Su;Jang Hye-Jeong;Park Byeong-Ju;U Jeong-Won
    • Proceedings of the Optical Society of Korea Conference
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    • pp.162-163
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    • 2002
  • 1-D photonic band-gap structure is identified in a cholesteric liquid crystal system. The optical transmission spectrum is measured and compared with the theoretical analysis. Nonlinear transmission is measured near the band edge. Also 3-D photonic band-gap structures are fabricated from dielectric colloidal polystyrene beads through a centrifuge method. The fabricated photonic crystals exhibit opalescent colors under white light and show a clear diffraction peak dependent on the incident angle of the light beam. Also the scanning electron microscope image was taken to verify the face-centered cubic crystal structure. Bragg's law and Snell's law are employed to describe the position of angle resolved diffraction peaks. It was shown that the optically deduced effective refractive index and lattice constants were in good agreement with the crystal structure identified by scanning electron microscope.

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