bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multislice calculation of Kikuchi patterns
Authors: Fant G. Y. 
Published: June 2020

The diffraction of the inelastically and pseudo-elastically scattered electrons in a crystal gives rise to the diffuse background in a diffraction pattern, including Kikuchi patterns as they are known, which are very sensitive to the direction of electron incidence relative to the crystal orientation. In the exact zone orientation, i.e., when the electrons are travelling along a major zone axis, a Kikuchi-band pattern is formed which reflects the crystal symmetry about that axis; otherwise, the pattern is known as Kikuchi-line pattern (thereafter collectively referred to as K-patterns).For localized inelastic events, such as interactions of incident electrons with shell electrons and various crystal point defects, in which intra-process coherence is negligible, the K-patterns can be simulated using the method described below.An inelastic event creates a spherical wave which, however, is strongly peaked in the forward direction of electron traveling, as given by the typical form f(θ)e-kr/r, where symbols have their usual meanings.
Electron optical improvements for field emission SEMS
Authors: Moll S.H. 
Published: June 2020

The superiority of field emission electron sources for high resolution electron microscopy, as originally developed by Crewe et al, is well understood. A number of commercially available SEMs of satisfactory quality have taken advantage of the small energy spread and high relative brightness of the FE source. More recently, AMRAY has introduced high resolution field emission SEMs which take advantage of alternative configurations for the electron source and the electron optics of the column.The cold (room temperature) FE source has been replaced with ZrO/W FE sources operating in the Schottky mode. These sources have proven to be a practical alternative to cold FE for both high resolution and high incident current applications. The zirconiated source requires no periodic "flashing" to clean the emitter tip since it operates continuously at a temperature of the order of 1800° K. The ZrO/W gun current is an order of magnitude higher than that of the cold source, it exhibits even higher angular brightness, and operates stably at a vacuum of 10-9 torr, an order of magnitude poorer in pressure than that required for cold FE sources.
HREM of twin intersections in Silicon
Authors: Hetherington C.J.D. , Dahmen U. , Pirouz P. , Westmacott K.H. 
Published: June 2020

A twin band is an effective barrier to the propagation of another, noncoplanar twin band. However, under conditions of sufficiently high local stress, twin intersections are possible. The geometric configuration of intersecting twin bands has been considered in the past in the context of dislocation mechanisms and deformation behavior. Observations on plane-strain deformed Co-8wt%Fe single crystals showed that intersecting twins gave rise to highly complex local deformation structures and led to the conclusion that the strain in the region of intersection was accommodated either by slip or by (secondary) twinning. The recent discovery of hexagonal ribbons of Si in hot-indentation experiments on silicon has renewed the interest in twin intersections as an integral part of the deformation microstructure, and prompted their study by high resolution microscopy.It is frequently necessary to record high resolution images under less than optimum conditions, e.g. because of radiation damage or local distortions. It then becomes desirable to devise methods for extracting the maximum information from such imperfect images.
Structure and defect structure of recent high Tc superconductors
Authors: Tendeloo G. Van , Zandbergen H. W. , Landuyt J. Van , Amelinckx S. 
Published: June 2020

Defects in the new superconducting materials play an important role and the superconducting properties are often influenced by their presence. In this review we will not consider the “classical” 1-2-3 compounds since they will be treated in a separate contribution.The Bi2Sr2CanCun+1Ox compounds show a strong intergrowth of lamellae of each of the phases corresponding with different n-values. An experimental relationship has been established between the n-values and the critical temperature for superconductivity; n=0,1,2 corresponding respectively with Tc values of 20K, 80K and 110K. Each of these phases is moreover incommensurately modulated. The origin of this modulation is still not definitively elucidated but we have performed a number of experiments and substitutions in order to get more information on the nature of this distortion. Several models are compared; the most likely one being the presence of extra oxygen in the BiO layers and the subsequent relaxation of the atom positions.
Crystal structure and microstructure of high-Tc superconducting Bi2Sr2CanCun+1O6+2n+δ
Authors: Eibl O. 
Published: June 2020

Results of the analyses of the crystal structure and crystal defects of high-Tc Bi2Sr2CanCun+1Oz ceramics are presented. Specimen were prepared in a conventional mixed oxide process. In series of electron diffraction patterns of the (n=1) phase(Tc≈ 80 K) reflections appear which are not consistent with the Bbmb space group symmetry suggested in the litterature. Extinction conditions obtained from electron diffraction patterns are compared to extinction conditions of space groups (e.g. Pbmb and Pbnb) which have a primitive Bravais lattice and are “klassengleiche” subgroups of Bbmb.Planar crystal defects on (001) planes were observed in Bi2Sr2CanCun+1Oz phases. These defects are (i) intrinsic and extrinsic (001) stacking faults forming lamellae of {n=0,1,2,3,4) phases and (ii) (001) twin boundaries. An extrinsic (001) stacking fault in the {n=1) phase is shown in fig.1. The image was obtained with a 400 kV electron beam in a microscope equippped with a pole piece with small spherical aberation (Cs= 1mm).
Twin boundary structure of a Y-Ba-Cu-O superconductor
Authors: Zhu Yimei , Suenaga Masaki , Sabatini R. L. , Xu Youwen 
Published: June 2020

The (110) twin structure of YBa2Cu3O7 superconductor oxide, which is formed to reduce the strain energy of the tetragonal to orthorhombic phase transformation by alternating the a-b crystallographic axis across the boundary, was extensively investigated. Up to now the structure of the twin boundary still remained unclear. In order to gain insight into the nature of the twin boundary in Y-Ba-Cu-O system, a study using electron diffraction techniques including optical and computed diffractograms, as well as high resolution structure imaging techniques with corresponding computer simulation and processing was initiated.Bulk samples of Y-Ba-Cu-O oxide were prepared as described elsewhere. TEM specimens were produced by crushing bulk samples into a fine powder, dispersing the powder in acetone, and suspending the fine particles on a holey carbon grid. The electron microscopy during this study was performed on both a JEOL 2000EX and 2000FX electron microscopes operated at 200 kV.
The effects of probe characteristics and specimen thickness on the spatial resolution in the AEM
Authors: Michael J. R. 
Published: June 2020

In order to interpret the high-resolution x-ray microanalytical data generated by modern Analytical Electron Microscopes (AEM), it is necessary to understand the effects of the electron probe characteristics (size, current distribution) and the specimen thickness and composition on the spatial resolution. The spatial resolution obtained in a VG HB-501 dedicated Scanning Transmission Electron Microscope (STEM) has been determined over a range of specimen thicknesses and for different probe sizes. The experimentally determined spatial resolutions are compared with calculations based on the Gaussian beam broadening technique.The spatial resolutions were measured from composition profiles obtained from specimens which had abrupt changes in composition. Suitably heat treated 40wt%Ni- 30wt%Cr-Fe specimens consisted of precipitates of 80-90wt%Cr in a matrix of 25- 29wt%Cr. Composition profiles were obtained by stepping the electron probe across a precipitate/matrix interface. Accurate probe placement was achieved by computer control of the analysis positions in conjunction with software which corrected for specimen drift. Beam broadening in the specimen degrades the abrupt step change in composition into a continuous one with a finite width.
High-spatial-resolution secondary and Auger imaging in a STEM
Authors: Drucker J.S. , Krishnamurthy M. , Hembree G.G. , Hong Luo Chuan , Venables J.A. 
Published: June 2020

Secondary electrons form the main signal in a standard SEM, and machines incorporating Auger electron spectroscopy and imaging have become widely commercialized. However, these approaches to low energy (0-2000eV) electron spectroscopy and imaging do not work at the highest spatial resolution, since there are geometrical and electromagnetic conflicts as the focal length of the probe forming lens is reduced. As discussed elsewhere in more detail, the solution is to make the magnetic probe forming lens of the SEM/STEM also function as the first stage of the electron collection and analysis system.A new lOOkV field emission STEM has been constructed for the NSF HREM facility, which incorporates provision for using these low energy electrons from both sides of a thin sample. The outline design has been described previously. The microscope, codenamed MIDAS, is of UHV construction throughout with ∽10−10 mbar at the sample position, and extensive surface preparation facilities. The region of the column concerned with secondary and Auger electrons is shown diagrammatically, but to scale, in fig. 1. This region consists of the objective lens, O, bounded by analyser chambers AC1 and AC2, onto which the electron detectors are mounted.
High-angle annular dark-field imaging on a TEM/STEM system
Authors: Otten Max T. 
Published: June 2020

High-Angle Annular Dark-Field (HAADF) imaging is a technique that brings out compositional contrasts with a sensitivity about 106 times higher than X-ray images, thereby allowing image recording in normal STEM exposure times (a matter of minutes) instead of the time required for X-ray images (usually several hours). The technique uses those electrons that have undergone high-angle scattering. These have Z dependence and are therefore very effective in bringing out compositional contrasts.Much of the HAADF work to date has been performed on dedicated STEMs. However, the technique can be performed as well with the annular Dark-Field detector on several types of TEM/STEM systems. Such systems have the added advantage of camera-length flexibility, providing a range of images with different kinds of information from the same detector.
High-spatial-resolution x-ray microanalysis of Al-2wt.% Cu aluminum thin films
Authors: Romig A. D. , Frear D. R. , Headley T. J. 
Published: June 2020

Aluminum - 2 wt.% copper alloys are commonly used in thin film form as interconnect metallization lines for integrated circuits. Experience has shown that the addition of the Cu to the Al, albeit at a decrease in conductivity, makes the metallizations more resistant to failure by electromigration. However, the mechanism by which Cu increases the resistance to electromigration has never been positively identified. One theory proposes that Cu coats the Al grain boundaries (boundaries are enriched in Cu) and retards grain boundary diffusion thereby reducing electromigration. Another theory suggests that a continuous thin layer of CuAl2 forms along the boundaries also reducing grain boundary transport and therefore the tendency to electromigrate. Recently, Frear et al. have reported on a detailed set of experiments to examine these theories from a microstructural viewpoint. Here, the details of the high spatial resolution microanalysis done to support the study of Fear, et al. are reported.Al- 2wt.% Cu was magnetron sputtered onto a borosilicate glass (BSG) coated (100) Si wafer. The Al-Cu films were sputtered at room temperature from a single source under an argon atmosphere at a deposition rate of 100 nm/min. Films 400 and 800 nm thick were prepared. The films were annealed under a 15% hydrogen forming gas (reducing) at 425°C for 35 min.
The role of secondary hardening dispersions in the ductile failure of an ultrahigh-strength steel
Authors: Hayzelden Clive 
Published: June 2020

Ultrahigh strength (UHS) steel is often achieved only at the expense of toughness. High hardness martensitic steels used for structural applications involving significant tensile loading and therefore requiring a KIC fracture toughness of 50 MPa., are limited to a Rockwell C hardness (Rc) of 50-55. In UHS steels the failure mechanism is predominantly that of plastic shear instability in which flow localization leads to the formation of intense shear bands. The underlying cause of the flow localization is investigated here in an UHS (Rc 55-56) 4340 steel.Azrin et al. have recently investigated the critical strain for shear localization in UHS 4340 steel under conditions of isothermal and adiabatic shear. The air melt 4340 steel of composition (wt.%): Fe-1.71Ni-0.75Mn-0.4lC-0.79Cr-0.25Si-0.24Mo-0.13Cu-0.011S-0.005P, was normalized at 910°C for one hour then austenitized at either 840°C or 1100°C for one further hour. Following austenitization, the specimens were stage I tempered at l60°C for one hour to form epsilon carbide and produce a peak hardness in the range Rc 55-56. The fracture surfaces of the double linear shear test specimens were examined in a JEOL 35U SEM and the alloy microstructures were investigated using a combination of CBED, EDS and EELS on both jet electropolished thin foils and carbon extraction replicas in a Philips EM 420T S(T)EM.
Microanalysis of a thin native oxide layer on silicon surfaces by parallel EELS
Authors: Kim M.J. , Carpenter R.W. 
Published: June 2020

It is known that a thin layer of so-called “native oxide” is formed immediately on clean silicon surfaces upon exposure to air at room temperature. The composition of native oxide, SiOx, is uncertain. Various experimental methods have yielded values less than 2 for x. Parallel energy loss spectrometers fitted to analytical electron microscopes with field emission sources provide sufficient spatial resolution (≤4nm) for direct quantitative analysis of native oxide films. In this note we report the first EELS analysis of native oxide on silicon.CZ Si {001} wafers, HF etched at room temperature and rinsed in doubly deionized water, were exposed to air until placed in an UHV chamber. A thin layer of Au wasthen deposited on Si surfaces, so that the native oxide layer was preserved between Si substrate and deposited Au film. Cross section TEM specimens were made in the usual way.
Sublattice occupancies of Pd in Cu0.5Au0.5−xPdx alloys by ALCHEMI
Authors: Bentley J. , Hisatsune K. 
Published: June 2020

The composition dependence of the lattice parameters of Cu0.5Au0.5−xPdx (0<x<0.25) alloys with the face-centered tetragonal ordered L10 structure has been measured by X-ray diffraction. The results confirm the behavior reported earlier by Nakahigashi et al. Whereas the unit cell volume decreases monotonically with increasing palladium content, the axial ratio c/a exhibits a maximum at about 4 at. % Pd, corresponding to local minimum and maximum values for a and c, respectively. In theoretical modelling of this behavior it was assumed that Pd atoms were randomly interchangeable with only Au atoms. Several techniques, including the ALCHEMI method, are being used to measure directly the sublattice occupancy of palladium.Electropolishing with various solutions failed to produce good quality specimens for analytical electron microscopy (AEM). Ion milling of specimens previously electropolished with an electrolyte of 10% perchloric acid in acetic acid was more successful. Analyses were performed with Philips EM400T/FEG and CM12/STEM instruments and EDAX 9100/70 and 9900 energy dispersive X-ray microanalysis systems.
Materials science of cells: Electron probe x-ray microanalysis and x-ray mapping in biology
Authors: Somlyo Andrew P. 
Published: June 2020

The general aims of Electron Probe X-ray Microanalysis (EPMA) in Biology is similar to that in Materials Science: the determination of composition at sub-micron resolution. Special requirements include stringent precautions for specimen preparation, high sensitivity for detecting low concentrations of elements avoidance, and if not possible, quantitation and control of radiation damage, and spatial resolution of at least tens of nanometers.Special precautions for specimen preparation are dictated by the fact that biological materials exist in an aqueous milieu, and one of the most common objectives of biological EPMA is the localization and quantitation of diffusible elements. Therefore, specimen preparatory techniques must include handling of live tissues in a manner that maintains normal physiological states, and rapid freezing to trap diffusible elements in their physiological compartments. In order to obtain high spatial resolution, ultrathin cryosections have to be obtained, freeze dried and transferred to the microscope under conditions that prevent elemental translocations. Specimen temperatures during cryo-sectioning are usually at about -100°centigrade.
Fibrillin molecules aggregate to form an extendible beaded structure which is a major component of “Elastin Associated” microfibrils
Authors: Keene Douglas R. , Maddox B. Kerry , Spurgin Marie B. , Sakai Lynn Y. , Glanville Robert W. 
Published: June 2020

A mouse monoclonal antibody was used to identify beaded aggregates found in guanidine extracts of human amnion as assemblies of fibrillin molecules. These aggregates were also shown to be a major component of extracellular matrix microfibrils. We further demonstrated that the periodicity of these aggregates can be increased when subjected to mechanical stress.Human amnion was extracted with guanidine and the extracted material purified using ion exchange and molecular sieve chromatography. A high molecular weight fraction was precipitated by dialyzing against dilute acetic acid. Part of the precipitate was suspended in 0.2 M ammonium bicarbonate buffer and rotary shadowed. A second portion was resuspended in culture medium containing antibody which recognizes matrix microfibrils, diluted 1:5 in ammonium bicarbonate and reacted for 120 minutes at room temperature. Antibody labeled precipitate was washed by repeated pelleting and resuspension in buffer and then incubated in Janssen GAM 5 nm gold conjugate for 60 minutes at room temperature.
Higher-order assembly of gastropodan hemocyanins as revealed by Scanning Transmission Electron Microscopy (STEM)
Authors: Hamilton M.G. , Rodriguez R.R. , Herskovits T.T. , Wall J.S. 
Published: June 2020

The hemocyanins of gastropods consist of aggregates of a cylindrical decameric subparticle that assembles into di-, tri-, tetra-, penta-, and larger multi-decameric particles with sedimentation coefficients of ca. 105 S, 130 S, 150 S, 170 S, and higher values. We are using STEM to measure the masses of individual particles and analytical ultracentrifugation to determine the distribution of sedimenting components.Hemocyanins were isolated from freshly collected hemolymph by gel filtration on BioGel A-5m columns. Samples were analyzed with schlieren optics in a Beckman Madel E ultracentrifuge. Specimens were diluted into 0.1 M HEPES, pH 8.0, 0.01 M MgC12 to a final concentration of 100 ug/mL and freeze-dried for STEM analysis. The STEM instrument was operated at 40 kV using a -140 °C cold stage. The elastically scattered electron signal from the STEM large angle annular detector was used to form the images. The specimens were imaged with 10 A pixels at a dose of 6-10 e/A2. Molecular weights of individual particles were measured as previously described.
Crystal structure-size relationship in ultrafine metallic particles
Authors: Liu Jun , Sarikaya Mehmet , Aksay Ilhan A. 
Published: June 2020

Ultrafine particles usually have unique physical properties. This study illustrates how the lattice defects and interfacial structures between particles are related to the size of ultrafine crystalline gold particles.Colloidal gold particles were produced by reducing gold chloride with sodium citrate at 100°C. In this process, particle size can be controlled by changing the concentration of the reactant. TEM samples are prepared by transferring a small amount of solution onto a thin (5 nm) carbon film which is suspended on a copper grid. In this work, all experiments were performed with Philips 430T at 300 kV.With controlled seeded growth, particles of different sizes are produced, as shown in Figure 1. By a careful examination, it can be resolved that very small particles have lattice defects with complex interfaces. Some typical particle structures include multiple twins, resulting in a five-fold symmetry bicrystals, and highly disordered regions. Many particles are too complex to be described by simple models.
Solidification of alternative phases in submicron spheres of nickel-chromium
Authors: Lin Hong-Ming , Kelly Thomas F. 
Published: June 2020

Kelly et. al. have processed submicron spherical particles of iron-nickel alloys and pure elements by using electrohydrodynamic (EHD) atomization. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-5 Pa. Each droplet is a separate nucleation experiment in which the droplet diameter is readily determined. Both high cooling rates and extreme isolation of heterogeneous catalytic sites are realized in the EHD process. Thus, rapid quenching of submicron spherical particles by using EHD process in Ni-Cr alloy may provide an opportunity to produce segregation-free alternative crystal phases (ACP) with low chromium contents.In this study, Ni-10, 20 and 30 at%Cr alloys were atomized and several samples of each composition were prepared for scanning transmission electron microscopy (VG HB501 STEM) analysis. EDS spectra from about ten different sphere sizes were recorded for each sample. Table I shows the average composition and standard deviation of the EDS measurements. The results indicate that each sphere composition deviates less than two percent. The X-ray counting times of chromium peak are greater than 1000 times in each sampling.
SEM study of humid air effect on fatigue of aluminum alloy 2024-T351
Authors: Jahn M. T. , Voris H. C. 
Published: June 2020

There is general agreement that the fatigue life of high strength aluminum alloys is reduced in humid environment. However, there are also data supporting the theory that humidity plays an insignificant role in the reduction of the fatigue life of aluminum alloy 2024-T351. In this study we examined the effects of stress level and water vapor density on the fatigue life of aluminum alloy 2024-T351 using scanning electron microscope (SEM). SEM evidence of the deleterious effect of humid air on the fatigue life of specimens cycled at intermediate stress level was presented. Discrepancies between this study and others were explained.Commercial aluminum alloy 2024-T35l (4.40Cu-1.45Mg-0.70Mn-0.23 Fe-0.15Si-0.13Zn) extruded bars were fatigue tested in reversed bending. The cycling was conducted in an environmentally controlled chamber. Ten specimens were machined for each fatigue stress level of 248, 276, 290, 317 and 359 MPa. Five specimens fran each stress level were cycled in desicated air at a relative humidity less than 45%.