bluuebunny/crossref_metadata_2025_split huggingface dataset:
X-Ray Safety of Electron Microscopes
Authors: Parsons D. F. , Phillips V. A. , Lally J. S. 
Published: June 2020

This investigation was initiated to provide the first assessment, from the users viewpoint, of the health hazards of X-ray leakages from conventional (40-200 Kv acceleration voltage) electron microscopes. Scanning microscopes were not considered at this point.X-rays are produced in the electron microscope when the beam strikes metal parts of the instrument. The degree of X-ray leakage depends on two factors--the intensity of the X-ray source and the amount of metal shielding surrounding it. The efficiency of total (continuous and characteristic) X-ray production is approximately proportional to the atomic number of the metal and to the acceleration voltage (platinum apertures are three times as efficient as the iron of pole pieces). However, the fraction of beam striking the metal has to be taken into account and the efficiency of the shielding. The thickness (number of Half Value Layers), the effect of absorption edges on X-ray transmission, and the cracks or openings in the shielding all have to be taken into account.
Scanning Transmission Microscopy Applied to Thick Specimen
Authors: Koike H. , Matsuo T. , Ueno K. , Suzuki M. 
Published: June 2020

Since the identification of single atoms was achieved by Crewe et al, scanning transmission microscopy has been put into pratical use. Recently they applied this method to the quantitative mass analysis of DNA.As pointed out previously the chromatic aberration which decreases the image contrast and quality, does not affect a scanning transmission image as it does a conventional transmission electron microscope image. Thus, the STEM method is advantageous for thick specimen. Further this method employs a high sensitive photomultiplier tube which also functions as an image intensifier. This detection method is effective for the observation of living specimens or easily damaged specimens. In this respect the scanning transmission microscope with high accelerating voltage is necessary.Since Uyeda's experiments of crystalline materials, many workers have been discussed how thick specimens can be observed by CTEM. With biological specimens, R. Szirmae reported on the decrease in the image contrast of rabbit psoas muscle sections at various accelerating voltages and specimen thicknesses.
SEM Correlation of Electrical Inhomogeneities and Crystal Defects in Semiconducting Si/Spinel Specimens
Authors: Norris C. B. , Thomas G. J. , Miglionico C. J. 
Published: June 2020

The use of SEM to characterize electrically inhomogeneous semiconductor specimens has numerous applications. Previous studies, however, have generally yielded results only when gross features, such as PN junctions, are present in the specimen. Here we report a sensitive technique for detecting electrical inhomogeneities in a semiconductor and establishing their relation to microscopic defects observable through SEM. A result is shown for an epitaxial Si film on a spinel substrate.Figure 1 describes the apparatus used for these studies. A JSM-II SEM is set to scan rapidly in the Y-direction, but at a much slower rate in the X-direction. The electron-beam-induced transient conductance of the contacted specimen produces a voltage at the input of a lock-in amplifier synchronized to the SEM Y-scan frequency. The demodulated amplifier output drives the Y-axis of an X-Y recorder, on which the X-axis sweep coincides with the slow X-scan of the SEM beam.
Temperature Dependence of Magnetic Domains and Wall Structures
Authors: Tsukahara Sonoko , Taoka Tadami , Nishizawa Hisao 
Published: June 2020

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.
TEM Analysis of Psuedo-Amorphous and Polycrystalline Silicon Thin Films
Authors: Anderson Ronald M. 
Published: June 2020

Thin polycrystalline Si films are used in certain aspects of the fabrication of integrated circuits in the electronics industry. To date, analysis of Si films has been confined to thick films (10-50μ) deposited and/or heat-treated at temperatures over 800°C. The pyrolytic decomposition of silane gas in nitrogen or hydrogen carriers is the most common deposition technique in the industry. In the present work, thin Si films, e-beam evaporated at 300°C onto SiO2 and Si3N4 substrates and subsequently heat-treated at temperatures from 450°C to 1040°C are compared to films deposited onto SiO2, Si3N4 and Al2O3 by the pyrolytic decomposition of silane gas at temperatures from 500°C to 900°C with no further heat-treatment.The evaporated films are psuedo-amorphous as-deposited and remain so after subsequent heat-treatments up to 600°C for one hour. A psuedo-amorphous diffraction pattern is seen in Fig.1; the first diffuse ring occurs at the Si (111) radius and the second broad diffuse ring spans the radii of the Si (220) and (311) reflections.
The Crystallography and Morphology of Epitaxial PtSi on Si Substrates
Authors: Anderson Ronald M. 
Published: June 2020

PtSi is used as an ohmic contact metallurgy and in Schottky Barrier diodes in the electronic component industry. Several points are considered in this paper that were not addressed in an earlier analysis of PtSi on Si due to the early PtSi's inability to grow on a Si substrate with an epitaxial relationship to the Si. These points are: what is the epitaxial relationship of PtSi to Si and why does PtSi not act as a barrier to the easy diffusion of subsequently deposited metals through the PtSi to the Si?An understanding of the epitaxial relationships of PtSi to Si can only come after the ambiguous SAD pattern of the PtSi is indexed. PtSi has an orthorhombic unit cell which would preclude the normal observation of diffraction symmetries greater than two-fold. However, the diffraction pattern in Fig. 1, of PtSi epitaxial on (001) Si, exhibits anomalous four-fold symmetry.
Effect of Diffraction Geometry on Lattice Images of Dislocations
Authors: Phillips Victor A. 
Published: June 2020

It was shown recently that the number of terminating fringes and fringe bending at inclined dislocations in germanium were sensitive to the diffraction geometry. The present experiments were designed to explore the situation for dislocations nearly normal to the foil.Germanium was selected since dislocations are immobile at room temperature A (110) oriented crystal slice was chemically thinned in a 95/5 mixture of nitric and hydrofluoric acids. Foils were examined in the high resolution stage of a Philips EM300 microscope modified to give a maximum magnification of one million. The specimen was oriented to give a strong zone of {111} systematic reflections, and {111} lattice images (3.27Å spacing) produced by the 2-beam tilt technique. The electromagnetic beam deflector was set-up so that the tilt switch could be used to switch from the +g to -g image. It was found possible to do this at one million magnification without appreciable change in image quality, field or focus, permitting pairs of images (Fig. 1) to be recorded.
Compensation of Lens Aberrations by Single-Sideband Holography
Authors: Downing Kenneth H. 
Published: June 2020

Single-sideband holography has been suggested as a method for extending the resolution of the electron microscope, since it produces contrast for all object spacings simultaneously and avoids the oscillations of the contrast transfer function characteristic of normal imaging. Image processing is still required to compensate for the effects of spherical aberration and defocus, which now show up in lateral shifts of image components. The method involves use of a semicircular objective aperture to stop out half of the scattered electrons. One finds, however, that a charge builds up on or around the aperture soon after it is positioned, introducing still another image defect.In order to compensate for the image defects, one needs to determine the wave aberration corresponding to the point spread function or contrast transfer function. In the case of normal (double-sideband) imaging one can determine the transfer function from measurements of the oscillations of the fourier transform of the micrograph (Fig. 1e).
Contrast and Resolution in Alfresco Microscopy and Thick Specimens
Authors: Sellar J. R. , Cowley J. M. 
Published: June 2020

Current interest in high voltage electron microscopy, especially in the scanning mode, has prompted the development of a method for determining the contrast and resolution of images of specimens in controlled-atmosphere stages or open to the air, hydrated biological specimens being a good example. Such a method would be of use in the prediction of microscope performance and in the subsequent optimization of environmental cell design for given circumstances of accelerating voltage, cell gas pressure and constitution, and desired resolution.Fig. 1 depicts the alfresco cell of a focussed scanning transmission microscope with a layer of gas L (and possibly a thin window W) between the objective O and specimen T. Using the principle of reciprocity, it may be considered optically equivalent to a conventional transmission electron microscope, if the beams were reversed. The layer of gas or solid material after the specimen in the STEM or before the specimen in TEM has no great effect on resolution or contrast and so is ignored here.
Characteristics of an Electrostatic Phase Plate
Authors: Krakow William , Siegel Benjamin 
Published: June 2020

Unwin has used a metallized non-conducting thread in the back focal plane of the objective lens that stops out a portion of the unscattered beam, takes on a localized positive charge and thus produces an additional phase shift to give a different transfer function of the lens. Under the particular conditions Unwin used, the phase contrast image was shifted to bright phase contrast for optimum focus.We have investigated the characteristics of this type of electrostatic phase plate, both analytically and experimentally, as functions of the magnitude of charge and defocus. Phase plates have been constructed by using Wollaston wire to mount 0.25μ diameter platinum wires across apertures ranging from 50 to 200μ diameter and vapor depositing SiO and gold on the mounted wires to give them the desired charging characteristics. The net charge was varied by adjusting only the bias on the Wehnelt shield of the gun, and hence the beam currents and effective size of the source.
Reduction of Contamination Rates in Electron Microscopes
Authors: Greene G. M. , Sprys J. W. , Melvin C. D. 
Published: June 2020

In scanning and transmission electron microscopes anti-contamination coldfingers at the specimen are usually limited in design or use because of available space. An anti-contamination device has been developed which takes advantage of the space provided by the long evacuation pipes employed on many SEMs and TEMs. This device consists of a long U shaped copper tube inserted into the vacuum line used to evacuate the emission chamber and column. Liquid nitrogen is circulated through the copper tube for cooling. The cooled tube provides a trapping surface for contamination with a minimum restriction to gas flow. A “top hat” configuration, as shown in the figure, was used to prevent freezing of-the o-ring. The purpose of the cup is to increase the heat conduction path between the feed-thru and the o-ring.Two such devices were installed in electron microscopes; one in a JSM II SEM and one in a Philips EM 200 TEM.
Refinements to a Polyvinyl Alcohol Replication Technique
Authors: Plummer H. K. 
Published: June 2020

Many techniques for the replication of polymer fractures for study in the transmission electron microscope have evolved through the years. If the surface of interest is to be retained for further study a two stage replication technique, which does not alter the original surface, must be used.Since the materials of interest in our laboratory were polymethyl methacrylate and polystyrene, a water soluble replicating material, such as gelatin, polyvinyl acetate, or polyvinyl alcohol had to be used. Organic solvents commonly used for other replicating materials have swollen or dissolved the fracture surfaces.Because of the excellent results reported in the literature for polyvinyl alcohol (PVA) with rough fracture surfaces it was decided this technique would best fit our needs.According to Prestridge (E. M. S.A., 1962, p. 278) the supernatant liquid from a saturated solution of PVA (approx. 13%w/v) was placed on the fracture surface and allowed to dry.
Contrast Effects at Grain Boundary Ledges in 304 Austenitic Stainless Steel
Authors: McDonald R. C. , Ardell A. J. 
Published: June 2020

Grain boundary ledges and/or dislocations have been observed in a wide variety of materials by a number of investigators using transmission electron microscopy (TEM) techniques. These defects can be expected to have interesting implications in terms of grain boundary precipitation reactions and creep behavior. In this paper we describe some of our TEM observations of grain boundary ledges in a specimen of type 304 stainless steel which was solution treated at 1040°C, quenched, cold worked 2%, and aged for 15 minutes at 850°C.The configuration of the ledges can be observed in Fig. 1. For the diffracting conditions in Fig. 1 both bright and dark contrast effects are associated with many of the ledges. Strong contrast of this sort has been observed by other investigators. This strong contrast is not typical, however, as can be seen on comparison with Figs. 2 and 3, which show the same grain boundary under different diffracting conditions.
Temperature Coefficient for Twin Boundary Free Energy in 304 Stainless Steel: An Electron Microscope Study
Authors: Murr L.E. , Horylev R.J. 
Published: June 2020

It has been recently shown that, as generally assumed, the coherent twin boundary free energy and the intrinsic stacking fault free energy in fee pure metals are approximately related by a factor of 2 at constant temperature, i. e.,In the case of pure metals, the temperature coefficient assumes a simple Gibbs form for a general interface (stacking fault or twin boundary):where S is the interfacial entropy per unit area of interface. It is noted in Eq. (2) that the temperature coefficient for an idealized pure metal is always negative. Thus, in the absence of interfacial adsorption of vacancies or impurities [assumed in Eq. (2)], the stacking fault and twin boundary free energies will increase with increasing temperature, and will be related by Eq. (1).In the case of multicomponent (alloy) systems, the temperature coefficient becomes a complex function of component entropy contributions, surface adsorption and desorption, and their temperature dependence:
The Analysis of Dislocations Using a Symmetry Criterion
Authors: Ingram J. C. , Strutt P. R. , Tzeng Wen-Shian 
Published: June 2020

The invisibility criterion which is the standard technique for determining the nature of dislocations seen in the electron microscope can at times lead to erroneous results or at best cause confusion in many cases since the dislocation can still show a residual image if the term is non-zero, or if the edge and screw displacements are anisotropically coupled, or if the dislocation has a mixed character. The symmetry criterion discussed below can be used in conjunction with and in some cases supersede the invisibility criterion for obtaining a valid determination of the nature of the dislocation.The symmetry criterion is based upon the well-known fact that a dislocation, because of the symmetric nature of its displacement field, can show a symmetric image when the dislocation is correctly oriented with respect to the electron beam.
Fractographic Studies of Fatigue Fracture of Metals
Authors: Koterazawa Ryoichi 
Published: June 2020

1. Correlation between crack growth rate and fracture surface topography.This section describes a part of the result of a co-operative investigation of Subcommittee on Fractography of Japan Society of Mechanical Engineers which is now under way with the aim of correlating microscopic fracture surface topography of different materials to macroscopic parameters. Materials studied are carbon steels, low alloy steels, stainless steels, cast steels, aluminum alloys, titanium alloys, copper alloys, bearing steels, case hardening steels and sintered alloys. Roughly speaking, fairly good correlation was obtained between spacing of fatigue striations and macroscopic crack growth rate with ductile materials in the range of growth rate around 0.03--3 microns/cycle (Fig.1). There was a tendency of striation spacing being larger than macroscopic rate in the range of lower growth rate and smaller in the range of higher growth rate. Above this range, dimples or stretched surfaces were predominant and, below this range, irregular striation-like markings(Fig.2) were main feature of the fracture surface, cleavage-like markings or grain boundary fracture being found occasionally.
The Effects of Impurities on Void Formation in α-Iron
Authors: Sprague J. A. 
Published: June 2020

A number of previous observations of the void formation induced in a variety of metals by fast neutrons or other bombarding particles have indicated that the degree of metal purity can have a significant effect on the void production rate. Increasing impurity content seems, in general, to reduce void formation, but some cases have been reported in which low concentrations of certain impurities significantly increased void production over that seen for the pure metal.In the current investigation, zone-refined iron and five low-concentration alloys of zone-refined iron were studied following irradiation with 8.8 × 1020 neutrons per cm2 < 0.18 MeV at 280°C. The five alloys contained 0.3 at-% Cu, 0.3 at-% Ni, 0.3 at-% V, 0.3 at-% P, and 0.1 at-% C, respectively. Since the voids produced by these irradiation conditions were very small, the out-of-focus observation technique suggested by Ruhle was employed in this study.
Radiation Damage Study of Type 304 Austenitic Stainless Steel by High Voltage Electron Microscopy
Authors: Das Gopal , Mitchell Terence E. 
Published: June 2020

In recent years high voltage electron microscopy has found widespread application to simulate the kind of damage produced by neutrons in potential nuclear reactor materials and to study ‘in-situ’ the nucleation and growth of defect clusters, such as dislocation loops and voids.In this investigation AISI Type 304 stainless steel has been used as a prototype to study electron irradiation damage as a function of accelerating voltage, irradiation time and temperature. A preliminary result on such studies will be reported here. 0.4 mm thick discs were cut from as-received 3 mm rods. They were sand-ground to 0.2 mm and most of them were encapsulated in a quartz tube under a vacuum of 10−5torr and subsequently annealed at 1100°C for 7 hours. Electron transparent foils were made from annealed and as-received discs by a two-step process of jet dimpling and electropolishing.
Three Surface TEM Observations of Cold Rolled 1100 Aluminum
Authors: Rohr D. L. , Hecker S. S. 
Published: June 2020

As part of an on-going study of 1100 Al at large plastic strains, we have examined cold-rolled samples from three orientations; through the sheet surface, and in the thickness direction along the rolling direction (RD) and transverse to the RD. Cell and subgrain sizes were determined in the same manner as for the earlier work.The starting plates of 1100 Al were annealed at 500 C and then rolled at room temperature to various thicknesses. These rolled plates were used to produce final samples rolled to 0.5 mm thickness with 62, 80, and 90% reductions. Thin foils were produced by lapping and jet electropolishing. A method was developed to make thin foils perpendicular to the sheet by lapping small pieces of sheet (1 mm wide) edgewise from both edges. This produces sheet 0.25 mm thick by 0.5 mm wide which were mounted between two 0.25-mm-thick 1100 Al disks 3 mm in dia. These disks had been slitted in the center to have slits ≪ 0.5 mm wide.
Comparison of Substructures Between Uniaxial and Biaxial Deformation in 1100-0 Aluminum
Authors: Rohr D. L. , Hecker S. S. 
Published: June 2020

As part of a comprehensive study of microstructural and mechanical response of metals to uniaxial and biaxial deformations, the development of substructure in 1100 A1 has been studied over a range of plastic strain for two stress states.Specimens of 1100 aluminum annealed at 350 C were tested in uniaxial (UT) and balanced biaxial tension (BBT) at room temperature to different strain levels. The biaxial specimens were produced by the in-plane punch stretching technique. Areas of known strain levels were prepared for TEM by lapping followed by jet electropolishing. All specimens were examined in a JEOL 200B run at 150 and 200 kV within 24 to 36 hours after testing.The development of the substructure with deformation is shown in Fig. 1 for both stress states. Initial deformation produces dislocation tangles, which form cell walls by 10% uniaxial deformation, and start to recover to form subgrains by 25%. The results of several hundred measurements of cell/subgrain sizes by a linear intercept technique are presented in Table I.
Microstructural Evolution in Reduced TiO2
Authors: Donlon W. T. , Shinozaki S. , Logothetis E. M. , Kaizer W. 
Published: June 2020

Since point defects have a limited solubility in the rutile (TiO2) lattice, small deviations from stoichiometry are known to produce crystallographic shear (CS) planes which accomodate local variations in composition. The material used in this study was porous polycrystalline TiO2 (60% dense), in the form of 3mm. diameter disks, 1mm thick. Samples were mechanically polished, ion-milled by conventional techniques, and initially examined with the use of a Siemens EM102. The electron transparent thin foils were then heat-treated under controlled atmospheres of CO/CO2 and H2 and reexamined in the same manner.The “as-received” material contained mostly TiO2 grains (∼5μm diameter) which had no extended defects. Several grains however, aid exhibit a structure similar to micro-twinned grains observed in reduced rutile. Lattice fringe images (Fig. 1) of these grains reveal that the adjoining layers are not simply twin related variants of a single TinO2n-1 compound. Rather these layers (100 - 250 Å wide) are alternately comprised of stoichiometric TiO2 (rutile) and reduced TiO2 in the form of Ti8O15, with the Ti8O15 layers on either side of the TiO2 being twin related.