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Calculations have been performed on the contrast available in thick specimens. Ten modes of operation have been considered, six in the conventional electron microscope (CEM) and four in the scanning transmission electron microscope (STEM). Electrons passing through the specimen fall into four categories, elastically scattered, inelastically scattered, unscattered, and those scattered both elastically and inelastically. For the various operation modes these groups are taken in combinations to form practical signal intensities. In the calculation of practical intensities, the angular distribution of plurally scattered electrons is considered. The fraction of each scattered group passing through the microscope aperture has been calculated for various types of illumination. The practical intensities are used to calculate the contrast available in stained and unstained specimens. For very thick specimens bright field offers the best combination of contrast and signal intensity. Other contrast modes show a reve...

1. The selection of transmission or scanning electron microscopes depends on the goal of the investigation and the object investigated. 2. The use of the transmission electron microscope is expedient in studying the characteristics of the fine structure which are revealed at large magnifications and require a high resolving capacity. 3. It is expedient to use the scanning electron microscope to study the characteristics of the structure which can be revealed by the three-dimensional picture in a large range of magnifications. 4. It is possible to determine the character of fracture from the fine structure (ductile, brittle, intergranular, and fatigue fractures) with scanning and transmission electron microscopes, since the microfractographic patterns obtained with both instruments are identical. 5. It is of considerable interest to analyze the characteri of fracture with the scanning electron microscope with use of stereoscopic images, which permit the most complete analysis of the structure. The method of preparing and analyzing stereoscopic images is of great practical interest, since it opens up additional possibilities for quantitative analysis of fractures.

The tope electrodes of silver or copper from which electron emission occurs, are studied for M-I-M structures of AgSiO/B[2]O3Cu and AgSiO/B2O3Ag while the specimens are contained in the chamber of a scanning electron microscope and subjected to bias voltages. Electroforming of the samples and their subsequent operation as negative resistance and electron-emitting devices lead to characteristic disturbances of the top electrodes which are consistent with the idea of filamentary conduction processes.

The characteristics of an accelerating lens system composed of three anodes in the scanning electron microscope are described. The main advantages of this accelerating lens system are that the working distance can be changed freely or the accelerating voltage can be changed over a wide range (about 0.3–100 kV) without changing the working distance, by adjusting only the control voltage of the second anode. Some problems in the manufacturing and operating conditions are also discussed.

A new type edge effect has been observed with a field emission scanning electron microscope. Contrary to a conventional edge penetration effect which is caused by the scattering of the primary electron, this new type edge effect is directly related to the mean free path of the secondary electrons produced in a specimen, and the width of the edge flaring in secondary electron image is of the order of the magnitude of the escapable distance of secondary electrons, i.e. about several tens of angstroms. Using a field emission scanning electron microscope recently constructed, this edge effect is experimentally observed by means of a cleaved edge of galena, and the effect is theoretically explained by applying the Monte Carlo technique.

Dislocation images in the high resolution scanning electron microscope with conventional filament have been obtained in transmission and back scattering modes from thin molybdenite crystals. Thick crystals show overwhelming topology contrast from surface steps and imperfections.

Thinning various materials for transmission electron microscopy (TEM) by ion machining has been discussed in the literature. Christie et al. [1] have listed many of these materials and briefly discussed a method of their preparation for T E M through ion machining. Sample dimensional requirements prior to ion machining are brought out by Barber [2], but nowhere in the literature are the techniques required for sample preparation of ceramic materials discussed. Reducing bulk materials to thin usable samples ( ~ 25/~m) can consume 50% of the total sample preparation time, including ion machining. To minimize sample preparation time, it is essential to have a simple reduction technique that produces high yields. This paper discusses a technique that has been successfully used to prepare alumina (A1208) samples for TEN[ work. An I M M I I I I 1 ion-milling machine was used for all of the experiments. The multihole anode and cathode was used, however, the single hole anode and cathode presently available would probably reduce the ion-machining time. The electron microscope used was a JE1V[-7, ~ operated at 100 KeV. The first step in preparing ceramic material for ion machining is to reduce the bulk material to a size and shape adaptable to both the ion machine and TE1V[ stages. The starting material for this study was 12.7 mmX 12.7 m m × 1.6 ram. The sample was mounted on a steel plate (measuring about 50 mm × 75 mm x 6 mm) with a high-temperature wax ~ (see Fig. 1). The plate was heated to a temperature just sufficient to allow the wax to run smoothly. The sample was pressed firmly into the wax, down to the plate, and subsequently cooled.

The image deblurring method given by Stroke and Halioua (1972a) for incoherent image forming conditions is shown to be valid for high-resolution images obtained in the scanning transmission electron microscope using a large annular electron detector. Coherent imaging is obtained only in the case of a small detector.

Summary A direct analysis of phagocytical substances in the alveolar macrophages in semi-thin sections of experimental silicosis of the guinea pig and of human biopsy material, is described. The observation of semi-thin sections in scanning transmission enables a good orientation of the section to be made. Using a large solid angle detector for backscattered electrons, the sections can be observed in the reflection mode of the scanning electron microscope (SEM) with good contrast similar to that of the scanning transmission electron microscopic-mode (STEM). Under these conditions phagocytic substances can be exactly localized in the cell and diagnosed by energy dispersive X-ray analysis.

There are three possible modes by which the incident primary beam in a scanning electron microscope releases the secondary electrons that are detected. Secondary electrons may be released as the beam passes through the final aperture. These do not contribute any information about the specimen, instead they contribute only additional noise and background signal which reduces the contrast range available. From the specimen itself, there are two sources which contribute information about the specimen: namely the secondary electron signal released by the surface interaction of the incident primary beam, and the secondary electron signal released as the back-scattered electrons pass out of the specimen. This latter signal constitutes approximately 80% of the secondary electron signal strength from the specimen.

Six modes of transmission electron microscopy (TEM) are compared by a numerical simulation of the image formation. The comparison includes five modes of the conventional electron microscope (CEM) (axial bright field, Unwin's phase plate, central stop dark field, tilted beam dark field, conical illumination dark field) and the annular detector mode of the scanning transmission electron microscope (STEM). It is assumed that the illumination is perfectly coherent and that the interaction between electron beam and specimen may be described as an entirely elastic event. Furthermore, the influence of radiation damage and noise is neglected. The restrictions due to these approximations are discussed and shown to be unessential to the conclusions. Recent results from single‐atom scattering theory are used to describe the specimen, a one‐dimensional model of a thin carbon film carrying six osmium atoms. The calculated through‐focus series demonstrates the nonlinearity of most modes of the CEM, which generates inte...

An electron microscope imaging method is described which makes use of an electrostatic device, analogous in function to the absorbing phase plate of light microscope, to produce strong contrast in biological specimens. This device is situated at the back focal plane of the objective lens in place of a normal objective aperture. The images created provide an especially realistic representation of the specimen structure and contain information about it that would not necessarily be able to be detected by the conventional bright field method of observation.

A simple and versatile electron biprism of the Mollenstedt type is presented, which allows the conversion of a Siemens Elmiskop 101 electron microscope for use as an interference microscope or as an electron interferometer. The microscope's performance with the biprism inserted at the level of the selector aperture plane is investigated both theoretically and experimentally.

A simple plate-like electrostatic energy filter with large dimensions (electrode distances 30 mm, thickness and bore dimensions of the middle electrode 20 and 6×50 or 2×50 mm) is designed for use in electron diffraction and electron microscopy. This design makes the construction, insulation and adjustment of the system easy. Both dispersive and non-dispersive operation can be used. Although the theoretical resolution of this filter is 30 mV, the practical resolution is limited to 1.5–3 eV because of the slit width and the beam divergence at the filter entrance required to give high intensity. The maximum operating voltage is higher than 75 kV.

A brief review of recent advances in the quantitative capabilities of the scanning electron microscope is presented. Special emphasis is placed on scanning transmission electron microscopy, X-ray techniques, secondary ion mass analysis, selected area electron channeling patterns, and image processing techniques. A systems approach to the development of the SEM as a research tool is recommended.

On the basis of a theoretical and experimental study of the properties of a filter, the optimal arrangement of an energy selecting electron microscope with a double magnetic prismelectrostatic mirror filtering system is designed.

The beam-induced conductive-mode and cathodoluminescence mode have been used in the study of GaAs and InP epitaxial layers and Gunn devices. The paper outlines the techniques used.

Ten specimens of plagioclase feldspars (An100 to An25) have been examined by transmission electron microscopy using dark field and direct lattice imaging. The specimens are classified into two groups: (i) those that have been quenched from the melt (synthetic An100, An95, An66 and An50) and (ii) those that have been cooled relatively slowly (An94, An77, An75, An52, An32 and An26).

Summary In Scanning Transmission Electron Microscopy (STEM) details at the top of thick specimens can be imaged with a better resolution than those at the bottom, because the scanning electron probe is broadened by multiple scattering. For quantitative measurement we used a test specimen consisting of a substrate film with an island-structured indium film and coated with polystyrene spheres of different diameters up to 1.1 μm. The fine detail contained in the indium film was observed and the beam broadening was that caused by the polystyrene spheres. This specimen was imaged with the spheres both above and below the layer, in a JEOL 100B electron microscope with a scanning device. Electron energies from 20 to 100 keV were used. Images with the sphere below show a higher resolution than those with the sphere above and also those of conventional electron microscopical images at 100 kV and 200 kV. The broadening of the edges on the photographic film was recorded with a microdensitometer. The results can be compared with theoretical calculations by a Monte Carlo method. There is a good agreement with the experiments if one uses an effective aperture obtained by transmission experiments.

Parallel striations in thin foils of UO2 single crystals introduced by pulse beam heating in the electron microscope have been studied by electron microscopy and electron diffraction. The observations are consistent with the view that both parallel (110) surfaces of the thin foil transform during heating into sets of parallel {111} faces.

The first published micrograph of a biological specimen photographed in a high voltage electron microscope (HVEM) appeared in a paper by Van Dorsten et al. in 1947, and it is consequently surprising that the HVEM does not play a greater role in biology 27 yr later. There are various reasons for this. The first prototypes were developed with the aim of enabling the investigator to examine thicker specimens than could be viewed at 100 kV. At the same time, however, the thin-sectioning technique was becoming established and consequently none of these early prototypes led to a commercial instrument (Glauert, 1972). Subsequently, the development of the HVEM was determined more by the needs of metallurgists and materials scientists rather than the needs of biologists, although the 1.5-MV microscope in Toulouse was constructed in the hope that it would make possible the examination of living cells (Dupouy et al., 1960). Results in this field have proved disappointing; even the best micrographs obtained so far reveal very little more internal detail of cells than can be seen with an ultraviolet microscope, and damage to living organisms during irradiation in the electron microscope is so fatal that any process that is observed is more correctly described as 'dying' than 'living'. In spite of the apparently insuperable problems in obtaining electron micrographs of living cells, the HVEM still has great potentiality in biology, arising from its capability to produce high resolution images of thick specimens. This capability enables the examination of much thicker sections than can be viewed in conventional instrumerits operating up to 100 kV and, in combination with stereo viewing, has restored the third dimension in studies of a great range of biological material. Examining very thin sections over more than 25 yr has led microscopists to think of biological structures in terms of thin slices: the term 'mitochondrion' summons up the vision of the cross-sectional view rather than of a threedimensional cylinder composed of interconnected membrane systems. This restoration of the third dimension in the appreciation of biological organization has been the major contribution of the HVEM so far. The other promising line of investigation is the examination of hydrated (not living) specimens in the HVEM. Water is an essential constituent of all biological structures, and consequently it is of paramount importance to be able to examine specimens in the wet state, particularly when considering the molecular level of organization. Rapid progress has been made during the past few years in the development of suitable preparative and imaging techniques, and in the design of 'environmental cells', and there is no doubt that further advances in this field will soon be reported. At present the few biologists who are using the HVEM are not all bringing the most fruitful problems to the microscope. For example, there is no point in obtaining a stereo view of a thick section unless an understanding of the threedimensional structure of the embedded material will make a real contribution to the solution of a particular problem. The primary aim of this review is to indicate the capabilities of the HVEM and to

The applications of and the problems encountered in the use of field electron emitters as cold cathode sources for electron beam devices have been reviewed. The possibility of using an etched carbon fibre as a cold electron source in such devices has been examined. A simple scanning electron microscope using a carbon-fibre field emitter has been constructed and produced stable pictures with a resolution of approximately 0·2 μm at a system pressure of 10−5 Pa. Unlike tungsten, the fibres will emit electrons for many thousands of hours at estimated current densities of the order of 105 A cm−2. Recently emission currents as high as 1 mA at applied voltages of approximately 3·5 kV have been obtained without any sign of breakdown after running continuously for 100 h.

The growth of β‐SiC films on Si by reaction of a Si single crystal with C2H2 has been studied for the conditions 10−7 ≤PC2H2≤5×10−4 Torr, 800≤T≤1100°C, in both high‐ and ultrahigh‐vacuum chambers. At C2H2 pressures below approximately 10−5 Torr, linear growth kinetics were observed over the temperature range investigated and the reaction probability was determined as 0.02–0.03. In this pressure range growth occurs by the diffusion of Si through porous defects incorporated in the growing film. We have studied in detail the structure of defected films formed under various growth conditions by scanning electron microscopy, scanning transmission electron microscopy, and transmission electron microscopy. We conclude that the occurrence of defects is intrinsic to the mechanism of film growth. The predominant defect type consists of a shallow (∼ 2000 A) pit in the Si substrate, over which the growing SiC assumes a porous polycrystalline morphology. The number and areal densities of these defects are proportional to the C2H2 partial pressure and the SiC film thickness, respectively. The defects act as sources of Si for reaction, and film growth occurs via diffusion of Si from the substrate through the porous overgrowth to the epitaxial SiC/vacuum interface, where reaction occurs. For C2H2 pressures exceeding approximately 10−5 Torr the porous defects are sealed off at an early stage in the growth and further reaction is virtually arrested due to the extremely small bulk and/or grain boundary diffusivity for Si in SiC over the experimental temperature range. No significant effect on growth rate due to the type of vacuum system used was found.

The intensity distribution on the specimen was computed by using the pupil function in terms of electron wave optics, and the spot size (defined as 80% of the total electron beam spread) was precisely obtained from this intensity distribution. From the computer simulation data the following results were obtained. (1) The spot size determined by the conventional method was generally over-estimated. (2) The difference in the optimum aperture size determined by the conventional method and by the electron wave optical method was of very small order of magnitude.

A system has been devised to provide direct observation of frozen biological tissue in the scanning electron microscope. Both transmission and secondary electron methods of signal collection have been obtained. In combination with energy elective fluorescent x‐ray analysis, the elemental constituents of subcellular regions less than 1000 A in diameter have been analyzed in the transmission mode of operation. Transmission scanning electron micrographs of frozen muscle shows significant microstructural differences with conventionally obtained electron micrographs although dark bands, possibly corresponding to z zones of classically observed spacing, are seen.

ZnS platelets crossed by two orthogonal sets of striations were examined. Nomarski optical interference micrographs and scanning electron microscope (SEM) secondary electron micrographs showed that both sets of striations had associated surface topographical features. One set consisted of polytype or faulted bands, the other of thickness variations (“linear markings”). SEM cathodoluminescence micrographs showed that in some specimens certain lines in both sets were strong light sources. In other specimens only polytype interfaces were linear cathodoluminescent sources. SEM charge collection micrographs showed that many of the polytype or faulted bands could produce contrast possibly due to the separation of electron-hole pairs by internal electric fields associated with these defects. Transmission electron microscopy showed that there could be several different types of faulted stacking structures in areas a micron square in striated ZnS.

The relative intensities of large angle single scattering processes which may contribute to scanning electron microscope contrast are calculated for cobalt. The degree to which these processes act selectively on the strongly absorbed Bloch wave of the two-beam approximation is also investigated. It is concluded that the low energy electrons should give orientation contrast which is similar to but weaker than that obtained using the higher energy electrons.

Detailed experimental procedures are described for the preparation and examination of keratin-fibre sections by transmission scanning electron microscopy. By using these techniques, relatively large (160-nm-thick) sections of fibre bundles can be scrutinized as a routine in magnification ranges from 20 × to 50,000 × with a maximum practical resolution of about 15 nm.

Ferroelectric domains in single‐crystal tetragonal barium titanate have been observed in the scanning electron microscope. Contrast in the image results primarily from the surface topography associated with domains; thus it is possible to observe surface structure associated with 90° domains under high magnification. In the scanning microscope one can observe the disappearance of domain structure above the Curie temperature, as well as domain growth and movement produced by intense electron bombardment. Scanning electron micrographs of as‐grown BaTiO2 have revealed surface structure which may correspond to the permanent surface layer which exists on BaTiO3.

A universal electron diffraction microscope, as we call it, consists of three stage electron lens and two specimen chambers and functions both as an electron microscope and as an electron diffraction unit. This instrument can be used in the following seven ways:(1) Electron microscope; range of magnification between 800 and 20 000 times can be covered continuously.(2) Electron microdiffraction unit; electron diffraction pattern characteristic of any small area of a specimen under microscopic observation can be revealed by a switch.(3) Dark‐field electron microscopic image.(4) High‐resolution electron diffraction unit.(5) Effective camera length of electron diffraction is variable from 0 to 250 cm.(6) Shadow micrographs of the specimen used in (4) can be directly obtained.(7) Shadow microdiffraction (probe diffraction); dark‐field microscopic image appears in each diffraction spot.The specimen in the second chamber can be heated at any temperature up to about 800°C and on which two kinds of substances can ...

In the transmission electron microscope, as shown in figure 1 (Nixon 1962), the electron gun at the top illuminates the specimen with the beam angle controlled by the condenser lens. The lenses below the specimen are used to magnify the image of the specimen which is viewed on the final screen at many thousand times magnification. If a second electron gun is placed below the fluorescent screen at the bottom of the column and the electron beam is projected upwards through the same lenses this second electron source will be reduced in size by the same amount that the specimen image is magnified. This effect can be observed with both electron guns on at the same time and demonstrates the reversibility of rays through electron lens systems. In this way the resolved point in the specimen image on the fluorescent screen or on the photographic plate is equal to the focused electron probe in the plane of the specimen.

Electron channelling patterns in the scanning electron microscope (Coates 1967, Booker, Shaw, Whelan and Hirsch 1967) have been generated on bulk ferromagnetic crystals, including cobalt, iron, Fe3Al and barium ferrite. In cobalt, distortions have been detected in the patterns, and are attributed to the effect of the; demagnetizing fields outside the specimen surface on the incident beam. It is suggested that the distortions may be used to estimate the strength of the demagnetizing fields.

It was shown that the radiation collection system collecting the transmitted radiation through the specimen from the back side (i.e., the side opposite the surface struck by the electron beam) was effective for the formation of cathodoluminescent (CL) images in SEM. This system provided an image resolution of the order of the electron beam spot size (~500 A) for a CaWO4 crystal at an accelerating voltage of 20 kV. This collection system was also especially useful for the formation of spectroscopic CL images with a monochromator. The spectroscopic images of the mixed powder specimen of CaWO4 and ZnS were obtained separately in consequence of differences in their characteristic spectral components.

A simple electrostatic device has been constructed which, when inserted in the optical system of an electron microscope, functions as an absorbing phase plate. Its operation depends on the central portion of a thin poorly conducting thread generating a stable potential under the influence of the electron beam and creating a particular form of electric field. An electron interference technique is employed to study the stabilizing mechanism and to develop a method for achieving the required magnitude of potential. The performance of this device is gauged by optical diffraction of electron micrographs of a thin carbon film; its application is illustrated by examining some negatively stained biological specimens. The results indicate that such an ‘electrostatic phase plate’ can provide significant improvements in contrast and signal/noise ratio over normal bright field images without loss in resolution.

The design, advantages and applications of automatic electron diffractometers are discussed with reference to an improved system. The power to measure electron scattering profiles from which loss electrons are virtually eliminated is the fundamental difference between the new instruments and traditional photography of electron diffraction patterns. The basic limitations of the diffractometers are discussed. A new treatment of the electron gun is given, based on angular distributions of current which prove to be Gaussian. The treatment is necessary when maximum signal intensity is required. A number of improvements in electronic circuitry are described which include servostabilization of the gun emission; automatic two-dimensional scanning, and control of CRT display brightness or of xy writing rate in accordance with the intensity of the peaks. The fields of application where the now diffractometers have advantages are when accurate, that is filtered, intensities must be determined, and when grow...

The paper is concerned primarily with the electron guns employed in electron microscopy.The position of the image of the cathode, the magnification, and the divergence of the beam leaving the anode are calculated for a three‐electrode electron gun with plane electrodes and circular apertures both for zero and battery bias. The simplifying assumption is made that the electrostatic lenses are thin. The results are compared with the experiments of Johannson. The extension of the results to the gun used in the transmission electron microscope is considered with the aid of electrolytic trough measurements. The case of a gun biased by a cathode resistor is also discussed.

A two‐dimensional surface chemical analysis over an area on a metal specimen has been accomplished by means of high‐spatial‐resolution Auger electron spectroscopy in a computerized scanning electron microscope. The experimental results are presented in graphic form by the new method of Auger electron imaging.

An electron microscope equipped with conventional electron optics can be used as a `diffractometer' for structure research on individual aperiodic objects. The resolution limit of the electron microscope is not the resolution limit of the `diffractometer' and electron structure research with atomic resolution is possible. The advantage is that a diffractometer of this type can measure amplitudes and phases. The theory is developed in the language of the crystallographer, mainly using the concept of modifying functions. It is shown that, as in crystallography, redundancies in structures can be used in the analysis.