bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscope investigations on ion damage in platinum
Authors: Schindler R. 
Published: June 2020

Modern electron microscopes with lift- and tilt-stages allow small defect clusters in different samples to be investigated under nearly identical imaging conditions, especially with respect to magnification and excitation error. Taking advantage of these identical imaging conditions and applying statistical averages of may defects, it is possible to obtain very accurate mean sizes of defect clusters. Recent contrast calculations which consider both the depth positions and the actual sizes of the defects (l) make it possible to obtain the actual sizes of the observed defects from their images rather precisely. It is thus possible to detect very small changes in the mean cluster sizes as functions of different parameters, e.g., irradiation temperature Tirr at which the defects have been created, or their annealing treatment. Electron microscopy thus can provide data on the kinetics of point defects in addition to more conventional methods, e.g., resistivity-recovery and damage-rate measurements.This paper reports on electron microscopy investigations on the temperature dependence of ion-damage in platinum.
Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope
Authors: Okamoto P. R. , Lam N.Q. , Lyles R. L. 
Published: June 2020

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.
Defects in ion implanted silicon
Authors: Lambert J.A. , Dobson P.S. 
Published: June 2020

The defect structure of ion-implanted silicon, which has been annealed in the temperature range 800°C-1100°C, consists of extrinsic Frank faulted loops and perfect dislocation loops, together with‘rod like’ defects elongated along <110> directions. Various structures have been suggested for the elongated defects and it was argued that an extrinsically faulted Frank loop could undergo partial shear to yield an intrinsically faulted defect having a Burgers vector of 1/6 <411>.This defect has been observed in boron implanted silicon (1015 B+ cm-2 40KeV) and a detailed contrast analysis has confirmed the proposed structure.
Preferred inclinations of <100> grain boundaries in epitaxially grown bicrystalline thin films of gold
Authors: Cosandey F. , Komem Y. , Bauer C. L. 
Published: June 2020

Energy and concomitant structure of grain boundaries are related to inclination of the boundary plane as well as misorientation of grains defining the boundary. Although increasing information is becoming available on variation of grain boundary energy with misorientation, still relatively little is known about variation of grain boundary energy with inclination. The purpose of this research is to examine preferred inclinations of preselected grain boundaries in gold by transmission electron microscopy (TEM) in order to identify principal structural elements and to relate these elements to the energy of special grain boundary configurations.Grain boundaries examined in this research are produced by a new technique involving vapor deposition of gold on common (001) surfaces of bicrystalline substrates of NaCl, characterized by preselected rotation about a common [001] axis, and subsequent epitaxial growth to form a bicrystalline thin film. These films are then removed from their substrates and examined by TEM. The principal advantage of this technique is that the grain boundary is formed during the deposition and growth process, thus resulting in a more perfect boundary structure while eliminating necessity of a separate bonding operation.
Decoration technique and surface physics
Authors: Bethge H. 
Published: June 2020

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.
TEM study of the influence Of O2-pressure on the oxidation rate of pure aluminium foils
Authors: Kritzinger S. , Ronander E. 
Published: June 2020

Initial stage oxidation of pure aluminium foils was studied by prismatic dislocation loop annealing. If the oxide film on a metal or alloy grows by the outward diffusion of the metal ions by either an interstitial or a vacancy mechanism through the oxide to the oxide/oxygen interface, vacancies are injected into the underlying matrix at the metal/oxide interface, creating a vacancy supersaturation in the matrix. The annealing rate of a prismatic loop, radius r and Burgers vector b, under the influence of a vacancy supersaturation, ΔC/Cₒ, is given by 1:where E is a constant at a given temperature which involves the diffusion coefficient and geometrical factors, and the term αb/r is related to the line tension of the dislocation. If αb/r > (ΔC/Cₒ), the loop shrinks and vice versa. The rate of vacancy production due to oxidation can thus be studied by observing the growth or shrinkage rate of perfect loops in the transmission electron microscope, based on Eq. (1).
Oxidation of dilute Al-Mg foils in an O2-atmosphere as revealed by TEM
Authors: Kritzinger S. , Ronander E. 
Published: June 2020

The thin film stage oxidation of Al-Mg in O2 was studied by TEM, utilising the prismatic dislocation loop annealing technique. Thin foils were prepared conventionally from oil-quenched sheets of Al-1.5 wt % Mg and oxidised ex situ in a special vacuum system1.Generally it was found that oxidising at ∽ 170˚C and above, created a vacancy supersaturation large enough to cause prismatic loops to grow (Fig. 1). The growth rate increased with increasing O2-pressure. Even at 10-6 torr the larger loops still grew, while smaller ones shrank. Although a linear relationship between loop radius and annealing time was occasionally observed, the growth rate generally increased with time during an isothermal anneal at constant O2 partial pressure, and also varied from loop to loop. Small black spots appeared on almost all the micrographs after an annealing time of approximately half an hour and more (Fig. 2(a)).
SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system
Authors: Annamalai V. , Murr L.E. 
Published: June 2020

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.
Quantitative X-ray analysis of thin samples in Tem
Authors: Pozsgai I. , Ilyinxx N.P. 
Published: June 2020

The intensity of characteristic x-rays /IiX/ from thin self-supporting samples depends not only on the concentration /c/ of the excited element but also on the mass thickness /ƍD/ of the film:The ki factors can be determined on thin etalon films of known thickness. So as to carry out quantitative analysis of thin samples, it is necessary to measure the local ƍ D independently of the measurement of x-ray intensities.In this paper a method is described to determine the mass thickness of thin samples by electron transmission and their chemical composition by combining the x-ray intensity and electron transmission measurements.It is known that some polycrystalline films e.g. Au, Ag, Sb, Bi and Cu films, exhibit anomalous behaviour in the exponential dependence of electron transmission on ƍD. Therefore we have developed a method for the measurement of electron transmission which overcomes the influence of Bragg reflection electrons.
Aspects of microanalysis in a transmission electron microscope
Authors: Sinclair R. , Jacobson B.E. 
Published: June 2020

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3. Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).
Lateral resolution of the electron microbeam analysis
Authors: Dudek H.J. 
Published: June 2020

The chemical inhomogenities in modern materials such as fibers, phases and inclusions, often have diameters in the region of one micrometer. Using electron microbeam analysis for the determination of the element concentrations one has to know the smallest possible diameter of such regions for a given accuracy of the quantitative analysis.In th is paper the correction procedure for the quantitative electron microbeam analysis is extended to a spacial problem to determine the smallest possible measurements of a cylindrical particle P of high D (depth resolution) and diameter L (lateral resolution) embeded in a matrix M and which has to be analysed quantitative with the accuracy q. The mathematical accounts lead to the following form of the characteristic x-ray intens ity of the element i of a particle P embeded in the matrix M in relation to the intensity of a standard S
Phase determination from superposed diffraction patterns
Authors: Kunath W. 
Published: June 2020

The strong prefield of the single-field condenser-objective permits the demagnified imaging of a small field-1imiting aperture stop and thus diffraction from small crystalline areas [1], An additional biprism within the field-1imiting aperture splits the beam, resulting in two coherent plane waves in the crystal plane. Both waves produce a diffraction pattern which, in principle, can--by properly adjusting the biprism-- be superposed coherently in such a way that every two spots of different diffraction order interfere (Fig. 1). This allows the phase determination of structure factors [2]. Quantitative considerations and difficulties are reported.In order to get sufficient information for the phases at least two exposures are needed with a relative translation of the source opposite to the crystal between them. Recently, encouraging light optical experiments have been performed with an extended source resulting in extended diffraction spots with intensity modulations (Fig. 2). The simplest model for explaining these modulations is shown in Fig. 3.
Intercalation of layer structures in the T. E. M. - modified charge density waves or artefacts?
Authors: Tat Lock G.J. 
Published: June 2020

Periodic lattice distortions (PLD) linked to charge density waves have been shown to give rise to the formation of a variety of superlattices in the diffraction patterns of layer structures. Foreign atoms or molecules may also be inserted in the Van der Waals gaps in these materials by intercalation and this changes the form of the observed superlattices. In this paper we present new experimental results for the in situ intercalation of a variety of layer structures with hydrazine (N2H4) in the electron microscope. Although these results are interpreted in terms of scattering from modified PLD, it is suggested that some previously published results should be reinterpreted in terms of double diffraction between rotated crystallites or other artefacts.Layer structures such as TaS2 or NbSe2 may exist in a variety of polytypes depending on the stacking of the layers along the c axis.
Kikuchi patterns of a non-centrosymmetrical crystal: tellurium
Authors: Le Goff J.-J. , Faivre G. 
Published: June 2020

Kikuchi patterns of crystals of low-symmetry exhibit features which cannot be observed in common crystals. Two kinds of effects have been studied on Te crystals ; these crystals have a 3 atoms basis and belong to the enantiomotphous space-groups D3(fig- 1).1. “UNUSUAL” BANDSSystematic diffractions may be classified according to the profile of their Kikuchi band at 100 kV.In the “usual” case, to which the quasi-totality of the diffractions belong, the band at 100 kV has its principal maxima near the first Bragg position (at ± ) and has no central maximum (at the O-position). We call this type of diffractions A-type.For the “unusual” cases, we define two extreme situations which have been observed in Te (fig. 3 and 4) :(i) A'-type [Te-]. The band presents at 100 kV a profile similar to those which are observed at higher voltage for diffractions of the “usual” type : a strong central maximum and principal maxima at n (n >1).
In Situstudies of fracture in solids
Authors: Narayan J. , Ohr S. M. 
Published: June 2020

Problems of crack nucleation and propagation associated with fracture in solids have been the subject of numerous experimental and theoretical investigations in the past, but the basic mechanism of the phenomena is not well understood at present. One of the difficulties stems from the fact that detailed microscopic information on the physical processes occurring at the crack tip is lacking. This is particularly true with respect to the formation of plastic zones involving the generation and motion of dislocations. In the present study, we have examined by transmission electron microscopy the propagation of cracks duringin situtensile deformation of stainless steel, molybdenum and magnesium oxide representing ductile, semi-brittle and brittle solids.Single crystal specimens suitable for electron transmission were prepared by dimpling and polishing from one side. With this geometry, the specimens could be deformed in pure tension in a bending holder. As the stress was applied, the cracks were initiated at the edge of the holes in the thinned foils.
High temperature studies of steels in the photo-emission electron microscope
Authors: Burnett B. , Parker K.E. , Baker A.J. 
Published: June 2020

The Photo-Emission Electron Microscope (PEEM) provides a unique facility for the direct examination of high temperature metallurgical reactions. However, considerable experience and care is required in the interpretation of the images obtained since they differ greatly from those produced in other types of electron microscopy. Furthermore, the morphology of products and the rates of reactions may be influenced by the fact that they occur at the free surface of a material. These effects are particularly important in the study of precipitation reactions in steels, where the interpretation of features of the image involves a consideration of the interplay between solute supersaturation, surface orientation and surface reactivity. A Balzers KE3 PEEM has been used to examine the behaviour of a variety of experimental and commercial alloy steels under high temperature conditions.Figure 1 illustrates the precipitation of an alloy carbide from austenite at low supersaturation. The precipitate is V5C6 and has formed at 850°C during cooling at 5°C/min from the 1050° C solution treatment temperature.
The use of STEM microdiffraction for the study of misorientation between subgrains
Authors: Ball M. D. , Morris P. L. 
Published: June 2020

While there have been studies of the relationship between misorientation in worked structures and the development of recrystallisation nuclei, most have lacked accuracy owing to the positional uncertainty of selected area diffraction. However the fine electron probe forming capability required for STEM operation enables diffraction information to be obtained from regions of the order of 20 nm or less in diameter. We have applied this technique to an examination of recrystallisation in situ, where the early stages of grain development are arrested by the presence of particles.The microdiffraction studies were carried out on specimens prepared from an Al-6% Ni alloy which had been given various rolling and annealing treatments. A JEOL JEM 100C/ASID-4D electron microscope was used in the STEM mode with the operating conditions such that the spot size was about 20 nm with a beam divergence of 10-3 rad.For each of the specimens studied, a suitably thin region with a typical subgrain structure was selected and photographed.
Structure and crystallization of amorphous metal oxide films
Authors: Shiojiri M. , Miyano T. , Kaito C. 
Published: June 2020

High resolution electron microscopic observations have been made on amorphous and crystalline metal oxide films. The specimen films were prepared by vacuum-evaporation of metal oxide powder from alumina coated tungsten basket onto clean glass substrates at room temperature. The films were deposited to a thickness of 100 Å, monitored with quartz crystal oscillating microbalance. The films were wet-stripped from the substrates and then mounted on gold holey films which were supported by standard gold electron microscope grids. Transmission electron micrographs were taken with JEM 100-C electron microscope under axial illumination. The microscope was equipped with an objective lens with Cs=1.8 mm and operated at 100 kV.Figure 1 shows an electron micrograph and an electron diffraction pattern of as-deposited WO3 film. The thickness of the film is assumed to be less than 50 Å, since the 100 Å thick film was floated on the distilled water for 20 minutes for thinning by dissolution.
Structure of chromium-chromium oxide films
Authors: Smith P. J. , Wildman H. S. , Wilson H. 
Published: June 2020

The percentage of chromium oxide in chromium films has been measured by Auger spectroscopy and related to structure and to electrical properties. Previous work had shown that depositing chromium films in increasing partial pressures of oxygen caused increases in resistivity and decreases in the temperature coefficient of resistivity (TCR).Blanket chromium films, 1200Å thick, were deposited on SiO2. The system was evacuated into the 10-7 Torr range and backfilled with water vapor to produce films containing from 1% to 30% of chromium oxide. The volume percentage was determined by profiling the oxygen and chromium in each film by Auger spectroscopy (assuming that all the oxygen was present as Cr2O3) and averaging over the thickness of the film. The TCR, measured in the temperature range 60°-160°C, was found to vary linearly with oxide content in the range from 5% to 30%.The TCR was +370 ppm/°C for a film with 2% oxide, whereas it was reported as +1200 ppm/°C for ultrahigh vacuum chromium.
Propane-jet freezing of muscle fibers for freeze fracture
Authors: Cantino M. E. , Pollack G. H. 
Published: June 2020

Recent advances in freezing techniques have intensified interest in freeze fracture for the study of nonmembranous cellular structures. We describe here a method for freezing single skinned (demembranated) muscle fibers in a dual propane jet freezing device.The freezing apparatus we used, developed by J. Gilkey and A. Staehelin (Univ. of Colo.), is based on the design by Müller. To adapt this device to studies of skinned relaxed and activated muscle fibers, we built the sample holder shown in Figure 1. The holder is separable into two parts (at the arrow) to allow mounting of fibers under relaxing solution. A modified Balzers freeze fracture support, with the back hollowed out and a groove milled in the top (figure 2) is placed between the hooks. A skinned frog semitendinosus fiber (F) is mounted over the support, between the fixed hook (right) and the moving hook (left). Fiber length is adjusted by moving the lever (L). To activate samples, the holder is removed from the bath and several drops of activating solution (relaxing solution plus calcium) are flooded over the fiber.
Glomangioma of the sella turcica
Authors: Asa S. L. , Horvath E. , Kovacs K. , Ezrin C. , Weiss M. H. 
Published: June 2020

Glomangiomas arise from specialized smooth muscle cells surrounding arteriovenous anastomoses (1), and occur most commonly in the sites where glomera are numerous, especially in the skin of nail beds, hands and feet. We report here a glomangioma in an unusual site, the sella turcica.A 42-year-old man complained of headaches and decreased visual acuity. Investigations revealed an intrasellar tumor with upward extension. There was no evidence of hormonal abnormality. After partial operative resection of the tumor, radiation therapy was administered. Two further surgical procedures were required for relief of symptoms caused by recurrent tumor.By light microscopy, the tumor was composed of sheets of epithelial cells and vascular channels lined by flat endothelium. Tumor cells had round, vesicular nuclei and homogeneous acidophilic cytoplasm. Mitotic figures were rare.