Electron image plane off-axis holography of atomic structures

An electron detector with small detection area for use in the final image plane of a transmission electron microscope has been commercially offered by TEM manufacturers (1). However, little has been reported about the application of such a device. In this report, the construction principle and the operation of a novel microdensitometry device is described which combines precision image point selection with versatility, high sensitivity, ease of operation, and comparatively low cost.The electron microdensitometer system consists of a transparent phosphor screen onto which the electron image is projected, a small “channeltron” electron multiplier (supplied by Galileo/Bendix) underneath, and a closed-circuit TV system (Fig.l). The screen has an effective diameter of 45 mm and contains a 2 mm concentric hole which allows a small beam of electrons to pass unobstructed to the electron multiplier. The multiplier consists of a 3 mm O.D. tube in custom L-shaped configuration and is mounted such that its collector is located outside the screen area to minimize obstruction of the image viewed on the TV monitor.

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Stem Holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179877 ◽

1990 ◽

Vol 48 (1) ◽

pp. 224-225

Author(s):

Thomas Leuthner ◽

Hannes Lichte ◽

Karl-Heinz Herrmann ◽

Jürgen Sum

Keyword(s):

Image Plane ◽

Empty Space ◽

The Other ◽

Electron Holography ◽

Detector Plane ◽

Object Plane ◽

Fourier Plane ◽

Object Structure ◽

Optical Process ◽

Electron Image

Electron optical imaging is a wave optical process. Therefore, to obtain the whole information about the object structure, one must record both amplitude and phase of the electron in the detector plane, e.g. in the Fourier plane or in the image plane. In the general case, an electron image detected only by its intensity is in principle incomplete [1]. This is true in particular in face of the lens aberrations which scramble amplitude and phase hence limit resolution and interpretability of an electron image.Following Gabor’s proposal of electron holography, these problems are being solved in the TEM [2], and in the STEM we try to tackle them in the following way [3] (fig.l): Two coherent waves, produced by means of the Mollenstedt electron biprism, are focused in the object plane. One of them is transmitted through the object and modulated in amplitude a(x,y) and phase φ(x,y) whereas the other one instead goes through empty space. Subsequently they are superimposed and give rise to an interference pattern (spatial frequency Rc) in the detector plane (coordinate u ) as

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The 'well-known' theory of electron image formation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075233 ◽

1983 ◽

Vol 41 ◽

pp. 288-289

Author(s):

M.A. O'Keefe ◽

W.O. Saxton

Keyword(s):

Image Processing ◽

Image Formation ◽

Source Profiles ◽

Electron Image

A recent paper by Kirkland on nonlinear electron image processing, referring to a relatively new textbook, highlights the persistence in the literature of calculations based on incomplete and/or incorrect models of electron imageing, notwithstanding the various papers which have recently pointed out the correct forms of the appropriate equations. Since at least part of the problem can be traced to underlying assumptions about the illumination coherence conditions, we attempt to clarify both the assumptions and the corresponding equations in this paper, illustrating the effects of an incorrect theory by means of images calculated in different ways.The first point to be made clear concerning the illumination coherence conditions is that (except for very thin specimens) it is insufficient simply to know the source profiles present, i.e. the ranges of different directions and energies (focus levels) present in the source; we must also know in general whether the various illumination components are coherent or incoherent with respect to one another.

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Electron Microscopy in Molecular Biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060027 ◽

1967 ◽

Vol 25 ◽

pp. 2-3

Author(s):

Cecil E. Hall

Keyword(s):

Electron Microscopy ◽

Molecular Biology ◽

Noise Level ◽

Molecular Structures ◽

Material Structure ◽

The Arts ◽

Shadow Casting ◽

Electron Image ◽

High Degree ◽

Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

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Resolution of a Transmitted Electron Image Formed by A Scanning Electron Microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100068928 ◽

1970 ◽

Vol 28 ◽

pp. 386-387

Author(s):

S. Takashima ◽

H. Hashimoto ◽

S. Kimoto

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Chromatic Aberration ◽

Objective Lens ◽

Specimen Thickness ◽

Probe Diameter ◽

Transmission Electron ◽

Electron Image ◽

Conventional Transmission Electron Microscope ◽

Scanning Electron

The resolution of a conventional transmission electron microscope (TEM) deteriorates as the specimen thickness increases, because chromatic aberration of the objective lens is caused by the energy loss of electrons). In the case of a scanning electron microscope (SEM), chromatic aberration does not exist as the restrictive factor for the resolution of the transmitted electron image, for the SEM has no imageforming lens. It is not sure, however, that the equal resolution to the probe diameter can be obtained in the case of a thick specimen. To study the relation between the specimen thickness and the resolution of the trans-mitted electron image obtained by the SEM, the following experiment was carried out.

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Finding the Right Problems: Some HREM Applications to Interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111938 ◽

1984 ◽

Vol 42 ◽

pp. 376-379

Author(s):

D. Cherns

Keyword(s):

Grain Boundaries ◽

High Resolution Electron Microscopy ◽

Boundary Structure ◽

Atomic Structures ◽

Grain Boundary Structure ◽

Resolution Electron ◽

Point To Point ◽

The Right ◽

New Generation ◽

Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

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Edge Penetration Effects in the Low-Loss Electron Image in the SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100103097 ◽

1988 ◽

Vol 46 ◽

pp. 202-203

Author(s):

Oliver C. Wells

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Beam Energy ◽

Secondary Electron ◽

Sharp Edge ◽

Beam Diameter ◽

Low Loss ◽

Additional Information ◽

Electron Image ◽

Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

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The DQE of an electron image recording system

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107642 ◽

1978 ◽

Vol 36 (1) ◽

pp. 100-101

Author(s):

K.-H. Herrmann ◽

D. Krahl ◽

H.-P Rust

Keyword(s):

Primary Electron ◽

Ideal Case ◽

Image Recording ◽

Main Requirement ◽

High Detection ◽

Electron Image ◽

Video Amplifier ◽

Detection Quantum Efficiency ◽

Selection Of ◽

The Ideal

The high detection quantum efficiency (DQE) is the main requirement for an imagerecording system used in electron microscopy of radiation-sensitive specimens. An electronic TV system of the type shown in Fig. 1 fulfills these conditions and can be used for either analog or digital image storage and processing [1], Several sources of noise may reduce the DQE, and therefore a careful selection of various elements is imperative.The noise of target and of video amplifier can be neglected when the converter stages produce sufficient target electrons per incident primary electron. The required gain depends on the type of the tube and also on the type of the signal processing chosen. For EBS tubes, for example, it exceeds 10. The ideal case, in which all impinging electrons create uniform charge peaks at the target, is not obtainable for several reasons, and these will be discussed as they relate to a system with a scintillator, fiber-optic and photo-cathode combination as the first stage.

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A light optical diffractometer for electron microscopical images operating in line

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107575 ◽

1978 ◽

Vol 36 (1) ◽

pp. 86-87

Author(s):

P. Bonhomme ◽

A. Beorchia

Keyword(s):

Electron Microscopy ◽

Electron Transfer ◽

Electron Microscope ◽

Image Converter ◽

Coherent Light ◽

Spatial Filters ◽

Electron Image ◽

Electron Microscopical ◽

Working Parameters ◽

Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

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