• Applied Microscopy
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• 제21권1호
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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.

• Applied Microscopy
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• 제32권3호
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• pp.185-193
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• 2002

Texture electron diffraction pattern을 이용한 결정구조 해석 이론은 러시아어로 씌여졌거나, 영문판 저서의 일부에 간단히 소개 되어있어 이해에 어려움이 있다. 이들의 이론은 벡터의 이론과 관련된 여러 관계식을 이용해서 설명될 수 있으며, 이로서 몇 개의 식에 포함된 오류를 수정하였다.

• Applied Microscopy
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• 제47권4호
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• pp.223-225
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• 2017

Cryo-electron microscopy (cryo-EM) is arguably the most powerful tool used in structural biology. It is an important analytical technique that is used for gaining insight into the functional and molecular mechanisms of biomolecules involved in several physiological processes. Cryo-EM can be separated into the following three groups according to the analytical purposes and the features of the biological samples: cryo-electron tomography (cryo-ET), cryo-single-particle reconstruction, and cryo-electron crystallography. Cryo-tomography is a unique EM technique that is used to study intact biomolecular complexes within their original environments; it can provide mechanistic insights that are challenging for other EM-methods. However, the resolution of reconstructed three-dimensional (3D) models generated by cryo-ET is relatively low, while single-particle reconstruction can reproduce biomolecular structures having near-atomic resolution without the need for crystallization unless the samples are large (>200 kDa) and highly symmetrical. Cryo-electron crystallography is subdivided into the following two categories according to the types of samples: one category that deals with two-dimensional (2D) crystalline arrays and the other category that uses 3D crystals. These two categories of electron-crystallographic techniques use different diffraction data obtained from still diffraction and continuous-rotation diffraction. In this paper, we review crystal-based cryo-EM techniques and focus on the recently developed 3D electron-crystallographic technique called microcrystal-electron diffraction.

• 한국분말재료학회지
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• 제24권4호
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• pp.285-291
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• 2017

We propose a custom analysis technique for the dark field (DF) image based on transmission electron microscopy (TEM). The custom analysis technique is developed based on the $DigitalMicrograph^{(R)}$ (DM) script language embedded in the Gatan digital microscopy software, which is used as the operational software for most TEM instruments. The developed software automatically scans an electron beam across a TEM sample and records a series of electron diffraction patterns. The recorded electron diffraction patterns provide DF and ADF images based on digital image processing. An experimental electron diffraction pattern is recorded from a IrMn polycrystal consisting of fine nanograins in order to test the proposed software. We demonstrate that the developed image processing technique well resolves nanograins of ~ 5 nm in diameter.

• Applied Microscopy
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• 제41권1호
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• pp.75-79
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• 2011

For quantitative analysis of nano-crystal structure, we reported the accuracy improvement method of lattice parameters measured from electron diffraction. For calculation of Au lattice parameters used as a standard crystal structure, it was considered two different acquisition methods (detector and enegy-filter) and three different calculation methods (conventional, least-square and regression fit). As a result, the measurement reliability could be enhanced by using CCD camera which gives higher performance, while energy-filtering did not affect the improvement the camera constant accuracy. Also, the accuracy of lattice parameters could be improved up to $10^{-4}$ order by regression fitting with correction formula. Finally, it is expected that the combination of regression fitting and intensity extraction from energy-filtered precession electron diffraction gives a solution of quantitative structure analysis for unknown nano-crystals.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.183-187
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• 2009

The structure of nano-crystalline $MnFe_2O_4$ was determined and refined with electron powder diffraction data employing the Rietveld refinement technique. A nano-crystalline sample (with average crystal size of about 10.9 nm) was characterized by selected area electron diffraction in an energy-filtering transmission electron microscope operated at 120 kV. All reflection intensities were extracted from a digitized image plate using the program ELD and then used in the course of structure refinements employing the program FULLPROF for the Rietveld analysis. The final structure was refined in space group Fd-3m (# 227) with lattice parameters a=8.3413(7) $\AA$. The reliability factors of the refinement are $R_F$=7.98% and $R_B$=3.55%. Comparison of crystallographic data between electron powder diffraction data and reference data resulted in better agreement with ICSD-56121 rather than with ICSD-28517 which assumes an initial structure model.

• Applied Microscopy
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• 제39권4호
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• pp.341-348
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• 2009

본 연구에서는 평균 입자크기가 100 nm인 $BaTiO_3$ 나노 결정체의 결정 구조를 전자회절을 이용하여 분석하였다. 전자회절을 이용하여 구조분석을 수행하기 위해 PED 장치의 실험인자를 보정한 후, PED와 일반적인 SAED를 이용하여 전자회절도형을 획득하여 비교 분석을 수행하였다. $BaTiO_3$ 나노 결정체에 대해 PED를 이용한 구조분석을 수행한 결과, $BaTiO_3$ 나노입자는 상온에서 입방정계와 정방정계의 구조가 혼합되어 존재함을 알 수 있었다. 또한 이론적 계산을 통해 두 상이 혼재된 $BaTiO_3$ 나노입자는 입방정계의 구조가 약 8.5nm의 표면을 형성하고 있는 coreshell 구조를 이루고 있음을 예측할 수 있었다. 이러한 $BaTiO_3$ 나노입자에 대한 입방정계와 정방정계 구조의 각각의 격자상수는 a=3.999${\AA}$과 a=3.999${\AA}$, c=4.022${\AA}$이었다. 이와 같이 일반적인 SAED에 비해 뛰어난 공간분해능과 다중산란 효과를 억제할 수 있는 PED 기법은 복합 나노 구조체의 결정구조분석에 보다 유용한 분석 기술로 활용할 수 있을 것으로 기대된다.

• Applied Microscopy
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• 제35권4호
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• pp.1-9
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• 2005

이 논문에서 Al-Cu-Mg 합금의 미세 석출 입자의 S-상 ($Al_2CuMg$) 결정구조에 대해 전자회절실험에 의한 포괄적인 연구 결과가 보고 되어 있다. 이 실험에는 한 S-상 입자를 포함하는 최소 영역의 일정 zone축의 회절패턴(SAED) 관찰과 이에 대응되는 운동학적 이론을 기초로 한 패턴의 시물레이션과의 비교 분석, 그리고 관측된 회절 패턴 필름으로부터 각 Bragg회절 점의 강도의 정량적 데이터 추출과 운동학적 및 동역학적 회절 강도 계산과의 비교 검토의 과정을 포함하고 있다. 이러한 연구의 한 결과 S-상의 결정구조는 일찍이 X-ray 방법으로부터 얻은 PW 모델결정(Perlitz and Westgren, 1943)과 일치함을 보여주고 있고, HREM 방법에 의해 새로이 구한 RaVel (Radmilovic et al., 1999) 모델과는 전혀 맞지않음이 판명되었다.

• 한국주조공학회지
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• 제43권2호
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• pp.88-91
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• 2023

• 한국결정성장학회지
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• 제6권4호
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• pp.543-551
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• 1996

단결정 표면 및 에피 증착증 표면에 대한 연구가 많아지면서 고에너지전자회절 및 반사전자현미겨의 이용도 늘고 있다. 국내에서는 아직 보편화 되지 않은 이들 두 기술을 위한 시편분비 과정을 요약하였고, 고에너지전자회절 연구시 매우 유용하게 쓰이는 연속 고에너지전자회절 패턴 지도 작성법에 대해 설명하고 그 예를 제시하였다.