Showing papers on "Electron tomography published in 1982"

Charge collection scanning electron microscopy

Abstract: This review encompasses the application of the scanning electron microscope to the study and characterization of semiconductor materials and devices by the Electron Beam Induced Conductivity (EBIC) method. In this technique, the charge carriers generated by the electron beam of the microscope are collected by an electric field within the material and sensed as a current in an external circuit. When employed as the video signal of the SEM, this collected current image reveals inhomogeneities in the electrical properties of the material. The technique has been used to determine carrier lifetime, diffusion length, defect energy levels, and surface recombination velocities. Charge collection images reveal the location of p‐n junctions, recombination sites such as dislocations and precipitates, and the presence of doping level inhomogeneities. Both the theoretical foundation and the practical aspects of these effects are discussed in a tutorial fashion in this review.

Electron microscope studies of the structure and propagation of the Pd2Si/(111)Si interface

Abstract: The structure of the epitaxial Pd2Si/(111)Si interface has been investigated by transmission electron microscopy. Observations normal to the interface using the weak-beam technique demonstrate the presence of misfit dislocations and support a model where atomically smooth regions of the interface are coherent and where misfit dislocations are associated with interfacial steps. High-resolution lattice images of (110) cross-sectional specimens are consistent with this model, showing characteristic image features which may be explained using theoretical multislice image simulations. It is shown that there are additional image features attributable to palladium-rich surface overlayers present on the cross-sections. The determination of the atomic structure of the interface is discussed.

High resolution electron microscopy and microanalysis

Abstract: While high resolution electron microscopy has been in use for many years, with steadily improving image resolution, most modern microscopes can provide complementary information on the chemical composition of very small volumes of material. This advance is very important and enormously extends the range of practical applications for the electron microscope. This review describes the basic principles and techniques of high resolution imaging and analysis, in both the conventional and scanning electron microscope, noting in each case the resolution that may be achieved.

Energy-filtered transmission electron microscopy of ferritin

Abstract: The focusing properties of a magnetic-sector spectrometer are shown to be suitable for forming high-spatial-resolution, energy-filtered transmission electron microscope images. Filtered images of ferritin molecules by using electrons scattered from the characteristic iron M2,3 and carbon K absorption edges clearly distinguish the 75-A iron core and 120-A protein shell. The minimum detectable mass is estimated to be 0.84 X 10(-20) g for Fe for an electron dose of 18 C/cm2 and 99% confidence.

One‐dimensional antiphase structure of Au22Mn6 studied by high‐voltage, high‐resolution electron microscopy

Abstract: Au-Mn alloys near the composition of 20% Mn have been investigated by the superstructure imaging technique using a 1 MV electron microscope A new superstructure, Au22Mn6, was proposed directly from the high-resolution images The structure is based on the Au4Mn structure of Ni4Mo (D1a) type and consists of parallel columns with a width of three Mn-atom rows, and the columns are separated by one-dimensional antiphase boundaries parallel to the (210) plane of the fundamental fcc structure Structural modulation and local disorder were also revealed at the atomic scale

Gold in electron microscopy

Abstract: The techniques of transmission and scanning electron microscopy have found unique application in the study of the microstructure of surfaces. In this application, the use of gold and its alloys has proved indispensable in producing images of the required contrast and detail. A brief survey is given here of the origin of contrast in these techniques and of how gold can be used to improve the quality of electron microscope images.

9. Electron Microscopy

Abstract: Publisher Summary This chapter examines the advancement in the developments in methods of electron microscopy. The electron microscope is an optical instrument, which permits the direct visual observation of structure at very high resolution. High-resolution images can only be obtained, however, if the specimen materials are prepared in a suitable form. Among the requirements that must be met, is that the specimens should be very thin, that they can be placed into a vacuum of 10−6. Electron microscopes have traditionally been designed to be operated at energy of 100 keV. It is the spherical and chromatic aberration of the objective lens and not the electron wavelength, which limit the resolution, because the electron optical lens aberrations cannot be corrected in the same way as, is possible in light optical systems. Radiation damage is the fundamental limitation in the overall effort to obtain high-resolution images of biological materials. The empirical studies of the radiation damage effect under electron microscope conditions are also presented.

X-ray and electron microscopy studies of polysulphur nitride

Abstract: (SN) x crystals have been studied by a combination of scanning electron microscopy, transmission electron microscopy and rotating crystal X-ray diffraction. The studies reveal a structure of considerable complexity. The size of individual crystallites is typically a few nanometres by a few tens of nanometres, and their crystal structure is as previously reported by Mikulski and co-workers rather than that reported by Boudeulle. In bulk crystals there is a mosiac spread of approximately 10° in and about the fibre axis. A new twin mode is proposed where crystals twin about a plane perpendicular to the plane defined by individual chains arid is referred to as a (¯102)* mode. The possibility of the existence of at least two other twin modes is also discussed. An alternative orientation relationship between the precursor dimer phase and the final polymer is presented.

Analysis of Periodic Structure in Model Subcellular Macromolecular Arrays by Fourier Processing of Single Line Video Signals in Scanning Transmission Electron Microscopy

Abstract: Fourier processing of single line video signals in scanning transmission electron microscopy (STEM) is a convenient and relatively objective method for the demonstration and characterization of the periodic structure present in thick sections of biological material where order cannot be readily determined by methods such as optical diffraction of transmission electron micrographs (TEM). Following alignment of the STEM scan vector with a prominent specimen axis, the video line signals, as visualized and focused in y-mode on the video monitor, were usually recorded on a digital signal processor for evaluation. The STEM line was frequency filtered, amplified, digitized, and subjected to fast forward Fourier transformation (FFT). Frequency space was examined by producing a power spectrum. Reverse Fourier transformations of the FFT, with appropriate frequency windowing, allowed separation of inherent specimen periodicities from background noise arising from various irregularities in the specimen and other sources. Pursuant to our studies on the neuroplasmic lattice of axons in neural tissue, we present here the results obtained with three model systems having spacings in the range of most interest with respect to subcellular macromolecular arrays (5-100 nm). Systems chosen were: 1) the lamellar structure of myelin sheath in cross section, 2) the lattice structure of tropomyosin crystals in thin sections, and 3) the cross-bridge lattice in longitudinal sections of squid mantle muscle fibers. These model tests show that information regarding periodic structure of materials can be obtained from economical single line scans rather than whole picture analysis.

A low-cost image analysis system for scanning transmission electron microscopy low-dose images.

Abstract: An image processing system is described which has been used to analyze STEM images of biological macromolecules. The system has the inherent virtues of being inexpensive, easy to program and self-contained. The operating procedures are described using a particular molecule (earthworm hemoglobin) as an example. We show the versatility of the system by describing addition, Fourier filtration, background subtraction, gray-scale expansion, y-deflection, and contouring of images. Color images are also produced but cannot be reproduced here.

Instant scanning electron microscopy in teaching.

Abstract: Cold stage techniques in scanning electron microscopy enable specimens to be viewed with a minimum of preparation. This means that teachers of embryology can use the scanning electron microscope in a dissecting class to help students to visualize small structural details in three dimensions. The technique is demonstrated with reference to two areas of application.