Colour in Electron Microscopy and Radiography

Orthodox radiographs and electronmicrographs are in monochrome. Methods are described for producing these in colour using high, medium and low kilovoltage records as colour separation negatives to give a single picture in colour.     

Electron Diffraction Using Transmission Electron Microscopy

Electron diffraction via the transmission electron microscope is a powerful method for characterizing the structure of materials, including perfect crystals and defect structures. The advantages of electron diffraction over other methods, e.g., x-ray or neutron, arise from the extremely short wavelength (≈2 pm), the strong atomic scattering, and the ability to examine tiny volumes of matter (≈10 nm³). The NIST Materials Science and Engineering Laboratory has a history of discovery and characterization of new structures through electron diffraction, alone or in combination with other diffraction methods. This paper provides a survey of some of this work enabled through electron microscopy.     

扫描电镜中的电子反射镜像现象及应用

观察非导电样品在扫描电镜（SEM）中产生的电子镜现象。研究了电子镜出现的条件，监测了电子镜像出现过程中表面电势Es和吸收电流Ia的变化。结果表明，当Es达到7kV～9kV时出现了电子镜像。当电子总发射产额σ≌1，Es≌4kV，及Ia≌0时，形成了稳定而无畸变的电子镜像。利用电子镜现象可确定电子散射率及入射电子能量的临界值E2，以及评价非导电样品导电性能。     

扫描近场光学显微技术在半导体材料表征领域应用的研究进展

半导体材料及其光电器件如激光器、探测器以及高速微波器件有着广阔的应用前景。半导体材料的结构和缺陷特性对器件性能起着至关重要的影响,然而对材料进行纳米尺度下的检测、表征无论是理论上还是技术和设备上都需要深入研究和发展,因此扫描近场光学显微技术在半导体材料表征领域有着无可替代的地位。扫描近场光学显微技术突破了传统光学显微技术的衍射分辨率极限的限制,具有超高空间分辨率、超高探测灵敏度等特点,并且是一种非接触性探测,具有无损伤性。简要介绍了扫描近场光学显微镜的原理及在半导体材料研究中的应用,包括量子阱结构中的位错及缺陷的表征,半导体器件的表面复合速率及扩散长度的纳米表征,以及半导体薄膜中的缺陷分布的检测。探讨了目前相关研究领域存在的主要问题,并对其发展趋势和前景进行了展望。     

Film-thickness Determination in Electron Microscopy: The Electron Backscattering Method

Investigations of the properties of electron backscattering are surveyed with respect to the application for thickness determination of self-supporting films and of surface films (top layers) on bulk materials, e.g., in electron microscopy.     

The Image Holography Method in Electron Microscopy

Abstract

In this paper, the process of image formation in electron holography is calculated based on a simplified model. The results have shown that the extension of the electron-beam source can cause a decrease in the electron-holography resolution. On the other hand, the unfavourable effects due to source extension can be eliminated by using the electron-image holography method.     

Study of Fullerenes,Nanotubes and Nanowires by Transmission Electron Microscopy

Abstract

The arc discharge reactor developped by Kratschmer et al^l produces a variety of new carbonaceous solids, including fullerenes and different kinds of graphitic cages of nanometric size, which can be hollow or filled with various materials. Complementary to neutron and X ray diffraction techniques, transmission electron microscopy rapidly appeared among the most important techniques for studying the structures of fullerenes and fullerites^2?6. Very generally, it allows us to obtain diffraction patterns of micronic size crystallites and the different imaging modes provide an unique tool to investigate in real space the morphology of the crystallites, structural defects faults at microscopic and nanometric scales^6?8. It is possible to perform very local chemical analysis and to study chemical environments in order to determine the nature of chemical bonds⁹. Futhermore, it is possible to study phase transitions through in situ experiments^5,10–12 and the behaviour of fullerites upon electron irradiation¹³. The interest of this technique has appeared even more crucial with the discovery of narotubes¹⁴ and their ability to be filled¹⁵ since, because of their nanometric size, the electron microscopy is at the moment the unique tool allowing their study and is therefore a challenge in the development of these new materials for applications in nanotechnology.     

Study of Fullerenes, Nanotubes and Nanowires by Transmission Electron Microscopy

The arc discharge reactor developped by Kratschmer et al^l produces a variety of new carbonaceous solids, including fullerenes and different kinds of graphitic cages of nanometric size, which can be hollow or filled with various materials. Complementary to neutron and X ray diffraction techniques, transmission electron microscopy rapidly appeared among the most important techniques for studying the structures of fullerenes and fullerites^2-6. Very generally, it allows us to obtain diffraction patterns of micronic size crystallites and the different imaging modes provide an unique tool to investigate in real space the morphology of the crystallites, structural defects faults at microscopic and nanometric scales^6-8. It is possible to perform very local chemical analysis and to study chemical environments in order to determine the nature of chemical bonds⁹. Futhermore, it is possible to study phase transitions through in situ experiments^5,10-12 and the behaviour of fullerites upon electron irradiation¹³. The interest of this technique has appeared even more crucial with the discovery of narotubes¹⁴ and their ability to be filled¹⁵ since, because of their nanometric size, the electron microscopy is at the moment the unique tool allowing their study and is therefore a challenge in the development of these new materials for applications in nanotechnology.     

Characterization of Dynamics in Materials Using Time-Resolved Electron Microscopy Incorporating Electron Counting and Electron Correlation Spectroscopy

Time-resolved electron microscopy incorporating electron counting and electron correlation spectroscopy can be used to quantify the dynamics in materials faster than the shot noise limit of the real-time observation in conventional transmission electron microscopy. An imaging electron beam current, temporally modulated by the dynamics of the specimen, is selected by the aperture in the image plane, and is measured by means of an electron counting technique. Applications of the method to the study of the dynamics of superconducting vortices and to the observation of nanovibrations of materials associated with elastic properties are discussed.     

Imaging Beam-Sensitive Materials by Electron Microscopy

Electron microscopy allows the extraction of multidimensional spatiotemporally correlated structural information of diverse materials down to atomic resolution, which is essential for figuring out their structure–property relationships. Unfortunately, the high-energy electrons that carry this important information can cause damage by modulating the structures of the materials. This has become a significant problem concerning the recent boost in materials science applications of a wide range of beam-sensitive materials, including metal–organic frameworks, covalent–organic frameworks, organic–inorganic hybrid materials, 2D materials, and zeolites. To this end, developing electron microscopy techniques that minimize the electron beam damage for the extraction of intrinsic structural information turns out to be a compelling but challenging need. This article provides a comprehensive review on the revolutionary strategies toward the electron microscopic imaging of beam-sensitive materials and associated materials science discoveries, based on the principles of electron–matter interaction and mechanisms of electron beam damage. Finally, perspectives and future trends in this field are put forward.     

High Resolution Electron Microscopy of Crystals

It is now possible to resolve the basic periodicity of the arrangement of atoms or molecules in crystal lattices using the electron microscope. Examples are given of lattices resolved directly (including superlattices), and indirectly (by means of moiré patterns) and of other periodic phenomena associated with crystal lattices (domains in ordered alloys). The basic principles of image formation in periodic objects are considered in terms of simple diffraction theory and some indications given of limiting factors in this type of investigation.     

Advanced Electron Microscopy for Advanced Materials

The idea of this Review is to introduce newly developed possibilities of advanced electron microscopy to the materials science community. Over the last decade, electron microscopy has evolved into a full analytical tool, able to provide atomic scale information on the position, nature, and even the valency atoms. This information is classically obtained in two dimensions (2D), but can now also be obtained in 3D. We show examples of applications in the field of nanoparticles and interfaces.     

Electron Microscopy of High Tc Superconductors

A review is given of structural defects occurring in different high Tc superconductors. The analysis of these defects, which is performed using electron microscopy and electron diffraction, has led in several cases to the successful synthesis of new superconducting compounds. Some of these defects also affect the superconducting properties either in a negative way (weak links) or in a positive way (flux pinning).

In this review particular attention is paid to the YBa₂Cu₃O_{7 − x} superconductor, where the detailed geometry of twin boundaries, shear planes, and dislocations is discussed together with the structural aspects of different superstructures associated with oxygen deficiency.     

Digital Electron Microscopy on Advanced Materials

Digital electron microscopy has been developed and applied to the structure analysis of advanced materials such as semiconductors and alloys. First of all, quantitative high-resolution electron microscopy was carried out on a Z-type faulted dipole in GaAs with the through-focus method. Through the quantitative analysis of the high-resolution images, the atomic displacement around the stacking fault was accurately evaluated. In the analysis of electron diffraction patterns of a Cu_0.725Pd_0.275 alloy, an energy filter was utilized to obtain electron diffraction patterns with a small background removing the inelastically scattered electrons. From the analysis of diffuse scattering of the Cu_0.725Pd_0.275 alloy, the short-range order parameters were quantitatively evaluated. Finally, it is pointed out that, based on the digital data of electron microscope images, the construction of the data base such as “EMILIA” (Electron Microscope Image Library and Archive: http://asma7.iamp.tohoku.ac.jp/EMILIA) is quite important for the future research of advanced materials characterization.