• Applied Microscopy
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• 제35권3호
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• pp.105-112
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• 2005

고분해능 TEM 영상 이론의 결맞음 조사에서의 결맞음에 관한 개념을 소개하였다. 현미경에서 부분 결맞음 파동으로 인한 transfer function과 envelope의 발생을 설명하고 현미경의 분해능과 관련된 passband와 Scherzer 초점 조건을 소개하였다.

• 한국재료학회지
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• 제32권8호
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• pp.345-353
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• 2022

In this study, using deep learning, super-resolution images of transmission electron microscope (TEM) images were generated for nanomaterial analysis. 1169 paired images with 256 × 256 pixels (high resolution: HR) from TEM measurements and 32 × 32 pixels (low resolution: LR) produced using the python module openCV were trained with deep learning models. The TEM images were related to DyVO₄ nanomaterials synthesized by hydrothermal methods. Mean-absolute-error (MAE), peak-signal-to-noise-ratio (PSNR), and structural similarity (SSIM) were used as metrics to evaluate the performance of the models. First, a super-resolution image (SR) was obtained using the traditional interpolation method used in computer vision. In the SR image at low magnification, the shape of the nanomaterial improved. However, the SR images at medium and high magnification failed to show the characteristics of the lattice of the nanomaterials. Second, to obtain a SR image, the deep learning model includes a residual network which reduces the loss of spatial information in the convolutional process of obtaining a feature map. In the process of optimizing the deep learning model, it was confirmed that the performance of the model improved as the number of data increased. In addition, by optimizing the deep learning model using the loss function, including MAE and SSIM at the same time, improved results of the nanomaterial lattice in SR images were achieved at medium and high magnifications. The final proposed deep learning model used four residual blocks to obtain the characteristic map of the low-resolution image, and the super-resolution image was completed using Upsampling2D and the residual block three times.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.74-74
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• 1999

TEM(투과전자현미경, Transmission Electron Microscop)은 결정재료뿐 아니라 비정질 재료까지도 원자단위의 구조를 연구하는데 매우 유용한 도구이다. 특히 200kV의 가속전압 투과전자현미경에 FEG(Field Emission Gun) 전자총이 장착되기 시작하면서 TEM은 비정질 구조 연구에 하나의 핵심적인 도구로서의 역할이 크게 기대되는 장비가 되었다. 본 연구에서는 TEM의 microanalysis accessary인 EELS(Electron Energy Loss Spectroscopy)technique을 주로 이용하던 기존의 방법대신 고 분해능(HRTEM(High Resolution Transmission Electron Microscopy)의 image로부터 비정질 정량묘사의 유일한 도구인 원자분포함수(RDF(Radial Distribution Function))로의 Reconstruction을 Simulation을 이용하여 시도하였다. 비정질 HRTEM image의 정량분석을 통하여 이 분야에서의 TEM의 한계를 이해하기 위하여 몇 모델을 제시하고 사용하였다. 또한 비정질 구조를 정량적으로 묘사하는 도구인 원자분포함수를 알아보고 비정질재료를 보다 물리적으로 모델링하기 위하여 가능한 모델 제시 후 첫 단계로서 HRTEM image에서 원자분포함수를 이끌어내기 위한 모델링을 수행하고 비정질 게르마늄(a-Ge) film에 대하여 실제로 적용하여 보았다. 마지막으로 실험적인 접근으로 200kV FE-TEm (poingt resolution 0.14nm) 으로 비정질 Ge의 image를 solw Scan CCD를 이용한 Elastic image를 Through Focus로 얻었으며 수치적인 정량비교를 역격자 공간에서 출발한 가장 물리적인 구조 모델을 이용하여 수행하였다. 모든 정량비교는 image의 Fourier 변환인 Diffractogram으로 하였다. 결론적으로, 많은 복잡한 수치 처리과정을 거쳐야 하지만 HRTEM의 image로부터 구조에 대한 정보(RDF)는 명확하게 얻을 수 있었다.

• Applied Microscopy
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• 제36권1호
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• pp.1-6
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• 2006

고분해능 TEM 영상 이론의 결맞음 조산에서의 결맞음에 관한 개념을 소개하였다. 현미경에서 부분 결맞음 파동으로 인한 transfer function과 envelope의 발생을 설명하고 현미경의 분해능과 관련된 passband와 Scherzer 초점 조건을 소개하고 결맞음 특성에 관하여 소개하였다.

• Applied Microscopy
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• 제44권4호
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• pp.138-143
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• 2014

Transmission electron microscope (TEM) is an excellent tool for studying the structure and properties of nanostructured materials. As the development of $C_s$-corrected TEM, the direct analysis of atomic structures of nanostructured materials can be performed in the high-resolution transmission electron microscopy (HRTEM). Especially, fast Fourier transform (FFT) technique in image processing is very useful way to determine the crystal structure of HRTEM images in reciprocal space. To apply FFT technique in HRTEM analysis in more reasonable and friendly manner, we made a new circular region of interest (C-ROI) FFT script and tested it for several HRTEM analysis. Consequentially, it was proved that the new FFT application shows more quantitative and clearer results than conventional FFT script by removing the streaky artifacts in FFT pattern images. Finally, it is expected that the new FFT script gives great advantages for quantitative interpretation of HRTEM images of many nanostructured materials.

• Applied Microscopy
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• 제41권3호
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• pp.215-222
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• 2011

We discuss the experimental procedure for extracting reliable phase information from a defocus series of transmission electron microscopy (TEM) dark-field images using the transport of intensity equation (TIE). Taking InGaN/GaN multi-quantum well light-emitting diode as a model system, various factors affecting the final result of reconstructed phase such as TEM sample preparation, TEM imaging condition, image alignment, the correction of defocus values and the use of high frequency pass filter are evaluated. The obtained phase of wave function was converted to the geometric phase of the corresponding lattice planes, which was then used for the two-dimensional mapping of lattice strain following the dark-field inline holography (DIH) routine. The strain map obtained by DIH after optimized image processing is compared with that obtained by the geometric phase analysis of high resolution TEM (HRTEM) image, manifesting that DIH yields more accurate and reliable strain information than HRTEM-based GPA.

• Applied Microscopy
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• 제40권1호
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• pp.47-51
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• 2010

The capability of real-time observation in TEM is quite useful to study dynamic phenomena of materials in a certain variable ambience. In performing the experiment, the choice of video recording program is an important factor to obtain high quality of movie streaming. Window Movie Maker (WMM) is generally recommended as a default video recording program if one uses "DV Capture" function in DigitalMicrograph$^{TM}$ (DM) software. However, the image quality does not often satisfy the condition for high-resolution microscopic analysis since the severe information loss in the final result occurs during the conversion process. As a good candidate to overcome this problem, Virtual-Dub is highly recommended since the information loss can be minimized through the streaming process. In this report, we demonstrated how useful VirtualDub works in a high-resolution movie recording. Quantitative comparison of the information quality between the images recorded by each software, WMM and VirtualDub, was carried out based on histogram analysis. As a result, the image recorded by VirtualDub was improved ~13% in brightness and ~122% in contrast compared with the image obtained by WMM at the same imaging condition. Remarkably, the gray gradation (meaning an amount of information) becomes wider up to ~115% than that of the WMM result.

• 한국재료학회지
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• 제22권3호
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• pp.130-135
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• 2012

We present a method of graphene synthesis with high thickness uniformity using the thermal chemical vapor deposition (TCVD) technique; we demonstrate its application to a grid supporting membrane using transmission electron microscope (TEM) observation, particularly for nanomaterials that have smaller dimensions than the pitch of commercial grid mesh. Graphene was synthesized on electron-beam-evaporated Ni catalytic thin films. Methane and hydrogen gases were used as carbon feedstock and dilution gas, respectively. The effects of synthesis temperature and flow rate of feedstock on graphene structures have been investigated. The most effective condition for large area growth synthesis and high thickness uniformity was found to be $1000^{\circ}C$ and 5 sccm of methane. Among the various applications of the synthesized graphenes, their use as a supporting membrane of a TEM grid has been demonstrated; such a grid is useful for high resolution TEM imaging of nanoscale materials because it preserves the same focal plane over the whole grid mesh. After the graphene synthesis, we were able successfully to transfer the graphenes from the Ni substrates to the TEM grid without a polymeric mediator, so that we were able to preserve the clean surface of the as-synthesized graphene. Then, a drop of carbon nanotube (CNT) suspension was deposited onto the graphene-covered TEM grid. Finally, we performed high resolution TEM observation and obtained clear image of the carbon nanotubes, which were deposited on the graphene supporting membrane.

• 진공이야기
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• 제4권4호
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• pp.18-22
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• 2017

Transmission electron microscopy (TEM) is a versatile and powerful technique that enables direct visualization of biological samples of sizes ranging from whole cell to near-atomic resolution details of a protein molecule. Thanks to numerous technical breakthroughs and monumental discoveries, 3D electron microscopy (3DEM) has become an indispensable tool in the field of structural biology. In particular, development of cryo-electron microscopy(cryo-EM) and computational image processing played pivotal role for the determination of 3D structures of complex biological systems at sub-molecular resolution. Here, basis of TEM and 3DEM will be introduced, especially focusing on technical advancements and practical applications. Also, future prospective of constantly evolving 3DEM field will be discussed, with an anticipation of great biological discoveries that were once considered impossible.

• Applied Microscopy
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• 제28권1호
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• pp.121-126
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• 1998

Detailed studies of high resolution TEM inages on the modulated structure caused by Zn vacancy ordering along [110] direction in BZT sintered at $1400^{\circ}C$ for 90 hours had revealed that the images which had hexagonal patterns were similar to those obtained from the structure which had no modulation, These images had appeared over the wide ranges from -30 nm to -42 nm in defocus values and from 2 nm to 20 nm in thickness. The computer simulated images showed that the modulation due to Zn vacancy ordering had made a small change in contrast in the interior of hexagonal pattern, which was very difficult to differenciate in experiments. The image which demonstrated the modulated structure very well was the one which obtained at -52 nm in defocus value and 16 nm in thickness.