Showing papers on "Electron tomography published in 1980"

Ultrasonic imaging in scanning electron microscopy

Abstract: A new type of microscopy is described here which uses a focused, modulated electron beam to generate ultrasonic waves at the front surface of a specimen and a piezoelectric transducer to detect these waves at the rear surface. The transducer output is used to form a scanned, magnified image of the specimen. A unique feature of this technique is that image contrast comes primarily from spatial variations in thermal and elastic properties. Images of integrated circuits have been obtained with ∼4 µm resolution. In thin film specimens 0.1 µm resolution should be possible.

Time-dependent images in transmission electron microscopy associated with the phase transitions of NbSe3

Abstract: Strandlike domains have been observed in Nb${\mathrm{Se}}_{3}$ at temperatures below 144 K by imaging in one of the satellite reflections produced by the phase transition. These appear to twinkle rapidly with many strands in the field of view lighting up and switching off in periods of a few seconds. In addition, fringes along these strands have been observed.

Study of single-electron excitations by electron microscopy II. Cathodoluminescence image contrast from localized energy transfers

Abstract: Observations of cathodoluminescence in ZnS single crystals using scanning transmission electron microscopy exhibit a dependence on crystal orientation indicating that about 20% of the signal originates in localized excitations. This figure can be explained in terms of energy transfer to valence excitations from energetic secondary electrons ejected from inner shells. Similar effects may operate in electron-beam-induced-conductivity images, X-ray production and other processes.

High‐Resolution Transmission Electron Microscopy Re‐examined as a Tool in Solid State Chemistry

Abstract: Transmission electron microscopy (TEM) can be used with crystalline solids to obtain direct images of small structural groups comprising a few coordination polyhedra with resolution nearly down to atomic scale (“lattice imaging”). More exact knowledge of the conditions required for direct imaging, as well as improvements in the instruments themselves, have now made it possible to examine very small defect regions (microdomains), faults in the stacking sequence of structural groups or atom layers (planar or Wadsley defects), and isolated defects in narrowly delimited areas that may actually be below the dimensions of the unit cell. The structural principle of the very smallest ordered regions can even be determined when X-ray structure analysis proves unable to do this. “Block structures” are particularly suitable as models for the testing and further development of the high-resolution method; the detection of three-dimensional, two-dimensional, and one-dimensional defects has been studied on such structures.

Scanning Electron Microscopy of Vibrating Quartz Crystals-A Survey

Abstract: Absfracr-A survey of past work done on the examination of surfaces of vibrating quartz crystals using scanning electron microscopy (SEMI is given. Some new observations are described. Details about the formation of electron contrast in the surface patterns of vibrating crystals and the application of SEM for measurement of amplitude of tangential vibrations and the design of crystal resonators for energy trapping are

Optimal imaging techniques in the scanning transmission electron microscope: applications to biological macromolecules.

Abstract: We show applications of the optimal imaging method to stained biological macromolecules. This optimal imaging method involves the following basic procedures: (i) for any given resolution, which is represented by the electron probe size in the scanning transmission electron microscope, a preferred magnification is used; (ii) the micrographs taken at the condition described above are then spatially filtered by using a low-pass filter (nu < 1/2d, in which d is the space between scan lines) to optically reconstruct the final optimal image. It is found that the micrographs obtained by using the optimal imaging method clearly show an improvement in contrast.

The many-beam theory of lattice image formation in transmission electron microscopy

Abstract: The Bloch-wave formulation of dynamical theory of electron diffraction has been used to obtain an analytic expression for the intensity profile of lattice images from perfect crystals when two or more beams are admitted by the objective aperture. The resulting equation takes into account the effects on the image of lens aberrations and defocusing as well as crystal orientation and thickness. By means of this equation, all the calculations may be carried out in the object space thus obviating the need for Fourier transformations.

On image contrast from single-electron excitation

Abstract: The diffraction-contrast preservation through various inelastic scattering processes has been studied with a 1·5 MV conventional transmission electron microscope fitted with an electron energy filter, for the case of thickness fringes and bend contours. Inelastic images due to plasmon, core electron excitation or multiple scattering in the energy-loss range up to 1700 eV are compared with elastic or unfiltered images. Attention has been drawn to the K-loss signal. Images show that inelastic mechanisms preserve contrast effects. In the inner-shell mechanisms, localization effects are not significant for the energy transfers and scattering angles typical in electron microscopy.

A real‐time optical image projection system for electron microscopy

Abstract: SUMMARY The Hughes liquid crystal light valve has been coupled to a transmission electron microscope using a fibre optics plate and transmission phosphor. This system makes it possible to reconstruct in real time, electron images in coherent or incoherent light of arbitrary intensity outside the vacuum. The experimental results reported are used to estimate the design parameters of an on-line coherent optical diffractometer for high resolution work.

Electron Holography by Field Emission Electron Microscope

Abstract: A 100 kV field emission electron microscope has been developed which has lattice resolution of 0.62 A. Electron holography was put to practical use utilizing the high coherence of this electron beam. The coherence of the electron beam was demonstrated by photographing 3, 000 bi-prism interference fringes, which is an order of magnitude greater than the number obtained previously. Spherical aberration of the electron lens, which has been the main obstacle to improving the performance of electron microscopes, was compensated for in the optical reconstruction stage of holography. Furthermore, an interference microscope was realized by means of holography. The electron microscopic image of an object contains information on object thickness in the phase of the electron beam which is not expressed in usual electron microscopic images photographed on film. Using the interference electron microscopy, the thickness distribution of fine polyhedron particles could be derived and their three-dimensional shapes determined.

An image intensifier for electron microscopy of polymers

Abstract: A unique manipulator for a channel electron multiplier array (CEMA) is described. It allows for easy installation into the viewing chamber of a transmission electron microscope. This device, through a series of motions, positions the CEMA normal to the electron beam, thus amplifying the electron flux while preserving its image. This increase in image brightness permits operation of the microscope with a greatly reduced flux of electrons passing through the sample, thereby decreasing radiation damage while simultaneously extending the time available for examination of the specimen. The manipulator can then move the CEMA to a remote area of the chamber, thus returning the microscope to its normal operating mode.

Transfer functions and electron microscope image formation

Abstract: Two types of electron microscope are capable of providing high-resolution information and it is only as the limit of resolution is approached that it is useful to discuss transfer theory These are the conventional transmission electron microscope, in which an extended area of the specimen is illuminated with electrons, which subsequently form a magnified image of this area, and the scanning transmission electron microscope, in which a very small probe is scanned over the specimen in a regular raster and the image is formed point by point, all the incident electrons contributing to each image point (pixel) In the conventional instrument, the image contrast is generated by two mechanisms which, though not independent, may be conveniently treated separately In order to understand these, we briefly recapitulate some practical aspects of electron microscopes (See also the chapter by Wade in this volume)