bluuebunny/crossref_metadata_2025_split huggingface dataset:
Introduction to electron holography
Authors: McCartney M. R. 
Published: June 2020

Electron holography is an imaging method in the transmission electron microscope (TEM) whereby the phase and amplitude of the electron wavefront can be obtained separately, unlike the conventional image which represents the intensity of the electron wave without any direct phase information. In particular, the phase image allows for the possibility of directly imaging the electric and magnetic potentials within a sample on the basis of phase changes produced on the incident electron wavefront. There are many advantages to directly imaging the phase structure and specific examples of the unique information available will be shown. For example, once the phase image is obtained it is possible to correct for the phase changes imposed by the transfer function of the objective lens by directly applying an inverse phase plate.Electron holography was originally proposed in 1949 by Gabor as a means of improving the resolution of electron micrography by correction of spherical aberration but was never fully utilized due to inadequate electron sources. In recent years, the availability of reliable field emission guns as coherent electron sources has stimulated renewed interest in the technique.
On-line image readout in CTEM
Authors: Herrmann K.-H. , Rau W. D. , Sikeler R. 
Published: June 2020

Quantitative recording of electron patterns and their rapid conversion into digital information is an outstanding goal which the photoplate fails to solve satisfactorily. For a long time, LLL-TV cameras have been used for EM adjustment but due to their inferior pixel number they were never a real alternative to the photoplate. This situation has changed with the availability of scientific grade slow-scan charged coupled devices (CCD) with pixel numbers exceeding 106, photometric accuracy and, by Peltier cooling, both excellent storage and noise figures previously inaccessible in image detection technology. Again the electron image is converted into a photon image fed to the CCD by some light optical transfer link. Subsequently, some technical solutions are discussed using the detection quantum efficiency (DQE), resolution, pixel number and exposure range as figures of merit.A key quantity is the number of electron-hole pairs released in the CCD sensor by a single primary electron (PE) which can be estimated from the energy deposit ΔE in the scintillator,
A global electronic imaging and distribution system employing a computer network
Authors: Palatini Dennis J. 
Published: June 2020

BACKGROUND Conventional silver halide photography has been used successfully for over one hundred years and remains unsurpassed in quality and fidelity for recording and displaying image information. During the past decade the impact of computers on all fields of information sciences has been both profound and widespread. Recently, personal computers have been acknowledged as effective and efficient tools for assuming the role of conventional photography. A simple, rapid, and well-established system was in place at Unilever to distribute the written word (electronic mail), however, no system was available to manage and distribute scientific images. An inordinate amount of time was elapsing between the time images were formed and when our colleagues viewed them Also, imaging scientists were spending an excessive amount of time in the darkroom developing and printing images. The Unilever Global Electronic Imaging and Distribution System was developed to address these growing problems.SYSTEM CONFIGURATION The configuration of the Unilever System is depicted in Figure 1. It consists of a restricted LAN (local area network) which isolates imaging traffic for optimal speed. This communication network still allows communication to the site LAN via the hub and Ethernet backbone and vice versa. The hub is an intelligent network controller that isolates network traffic.
Ultra-high resolution column for the scanning electron microscope
Authors: Drexel V. , Weimer E. , Martin J.-P. 
Published: June 2020

1.IntroductionThe demands made on the design of a high-performance SEM column are multiple and contradictory. It should provide outstanding image resolution at all beam energies with samples of all sizes and at any (reasonable) tilt angle. It should also allow excellent signal detection under all operating conditions and a high x ray take-off angle at a working distance suitable for high-resolution microscopy. A novel design concept for the electron optics of the SEM has been implemented in a new high-performance instrument (named DSM 982 GEMINI) in order to meet these goals.2.Advanced electron-optical columnA Schottky field emission source is used in the new SEM. This gun type exhibits the ideal point-source properties for a high-performance instrument. Optimum conservation throughout the column of the very high beam brightness (107 A/cm2.sr.kV) and the very low beam energy spread (0.4 eV) supplied by the gun is achieved by the implementation of a new electron optical principle: a high beam energy is maintained throughout the column (regardless of of the electron probe energy selected by the operator) and any beam cross-over is avoided (Fig. 1).
Advanced electron optics for micro- and nano-analysis in the TEM
Authors: Benner G. , Bauer R. , Probst W. , Weimer E. , Martin J.-P. 
Published: June 2020

1. IntroductionIn the materials sciences as well as in the life sciences energy-dispersive x-ray microanalysis (EDX) in the transmission electron microscope (TEM) is now established as a routine investigation method allowing high-sensitivity qualitative and quantitative element detection. The accuracy of the results obtained and the measurement time needed are largely determined by the following properties of the TEM used: shape of the objective lens pole-piece and design of the illumination system, collimation of the beam path and operation flexibility of the illumination system.2. Optimized X-ray detectionIn the EM 910 the design concept of the objective lens allows the x-ray detector to be placed closer to the specimen than usual (Fig. 1). Therefore an extremely high solid angle (i. e. 0.192 sr) of the x-ray signal can be intercepted by a 30 mm2-detector at a take-off angle of 20°. As a result, x-ray spectra can be acquired with a high countrate and a clearly improved signal-to-noise ratio. Element distribution maps with much improved information density can be acquired in the usual registration times.
Performance of the Philips CM200 FEG
Authors: Otten Max T. 
Published: June 2020

Since its introduction four years ago the Philips Field Emission 200 kV microscope has undergone a number of changes enhancing its performance. It has also become possible to quantify its performance more accurately.New developments are the introduction of the SuperTWIN-α and UltraTWIN objective lenses and the CompuStage goniometer. The SuperTWIN-α objective lens has a higher maximum tilt angle (±40° instead of ± 15°) while the point resolution remains 0.24 nm. The UltraTWIN lens has a point resolution of 0.19 nm and a maximum tilt of ±24°. Better specimens for determining the information limit have resulted in proven information limits of < 0.15 nm and ≤0.13 nm for the SuperTWIN-α and UltraTWIN lenses, respectively. The CompuStage, a five-axis motorised and computer-controlled goniometer, improves performance with regard to safety (no danger of damage to specimen holder or pole pieces), maximum accessible tilt, accuracy of movement, control and drift. The accessibility of the CompuStage to external computer control makes this goniometer ideal for developments in automation such as tomography or computer-assisted tilting for diffraction.
X-ray mapping without STEM
Authors: Brock Judith M. , Otten Max T. 
Published: June 2020

A knowledge of the distribution of chemical elements in a specimen is often highly useful. In materials science specimens features such as grain boundaries and precipitates generally force a certain order on mental distribution, so that a single profile away from the boundary or precipitate gives a full description of all relevant data. No such simplicity can be assumed in life science specimens, where elements can occur various combinations and in different concentrations in tissue. In the latter case a two-dimensional elemental-distribution image is required to describe the material adequately. X-ray mapping provides such of the distribution of elements.The big disadvantage of x-ray mapping hitherto has been one requirement: the transmission electron microscope must have the scanning function. In cases where the STEM functionality – to record scanning images using a variety of STEM detectors – is not used, but only x-ray mapping is intended, a significant investment must still be made in the scanning system: electronics that drive the beam, detectors for generating the scanning images, and monitors for displaying and recording the images.
Microscopy of stress-induced morphological development and dislocation nucleation during semiconductor epitaxy
Authors: Jesson D. E. , Chen K. , Pennycook S. J. , Baribeau J.-M. , Houghton D. C. 
Published: June 2020

Semiconductor films subjected to misfit stresses are unstable to the formation of surface undulations or waves. Atoms located in close proximity to the peaks of the undulations can relax and significantly lower the elastic energy of the film. Provided that the wavelength of the undulation is sufficiently large, this more than compensates for the associated increase in surface energy, leading to a morphological instability of the flat surface.An interesting feature of this instability is that although atomic planes near the peaks of the undulations can relax, stress concentrations develop at the undulation valleys. These stresses can be very large, even for rather shallow surface perturbations. The question, therefore, naturally arises as to the subsequent effect of these stresses on the evolving surface morphology and in particular, whether the magnitude of the stress is large enough to influence the nucleation of misfit dislocations. In order to study these issues experimentally, we have utilized Z-contrast imaging , atomic force microscopy (AFM), and plan-view transmission electron microscopy (TEM) to image the stress-induced surface evolution of SixGe1-x alloys which are compressively strained on Si(100).
Topography studies of magnetic-head pole-tip areas using atomic-force microprobe
Authors: Veisfeld Nina 
Published: June 2020

Atomic Force Microscopy (AFM) has made it possible to quantify an important phenomenon regarding magnetic head characterization, known as pole tip recession. The pole tip area of thin film magnetic heads, considered one of the critical regions in the head/disk interaction, became the subject of increasing concern within the past several years because of the rapid decrease of the flying heights (typical present values are ∽300 Å). The area of interest includes plated permalloy pole tips and the surrounding alumina matrix, sputter deposited onto a ceramic substrate. The complex topography of thearea is associated with the hardness differences between the materials in multiple layers compsiring the head.AFM analysis revealed significant variations in the topography of different thin film heads. Figure 1 presents a typical example of the pole tip area topography. In this AFM image the two pole tips are elevated above the surrounding matrix. A dark area above the upper pole (recessed by ∽190Å vs. the poles) and slightly brighter (elevated by ∽160Å) symmetrically positioned areas on both sides of the poles are clearly outlined.
Texture measurements in Al2O3 using BEKP
Authors: Vaudin M. D. , Cline J. P. 
Published: June 2020

The study of preferred crystallographic orientation (texture) in ceramics is assuming greater importance as their anisotropic crystal properties are being used to advantage in an increasing number of applications. The quantification of texture by a reliable and rapid method is required. Analysis of backscattered electron Kikuchi patterns (BEKPs) can be used to provide the crystallographic orientation of as many grains as time and resources allow. The technique is relatively slow, particularly for noncubic materials, but the data are more accurate than any comparable technique when a sufficient number of grains are analyzed. Thus, BEKP is well-suited as a verification method for data obtained in faster ways, such as x-ray or neutron diffraction. We have compared texture data obtained using BEKP, x-ray diffraction and neutron diffraction. Alumina specimens displaying differing levels of axisymmetric (0001) texture normal to the specimen surface were investigated.BEKP patterns were obtained from about a hundred grains selected at random in each specimen.
TEM investigations of surface residual stress relaxation in A12O3 and Al2O3-SiC nanocomposite
Authors: Fang J. , Chan H. M. , Harmer M. P. 
Published: June 2020

It was Niihara et al. who first discovered that the fracture strength of Al2O3 can be increased by incorporating as little as 5 vol.% of nano-size SiC particles (>1000 MPa), and that the strength would be improved further by a simple annealing procedure (>1500 MPa). This discovery has stimulated intense interest on Al2O3/SiC nanocomposites. Recent indentation studies by Fang et al. have shown that residual stress relief was more difficult in the nanocomposite than in pure Al2O3. In the present work, TEM was employed to investigate the microscopic mechanism(s) for the difference in the residual stress recovery in these two materials.Bulk samples of hot-pressed single phase Al2O3, and Al2O3 containing 5 vol.% 0.15 μm SiC particles were simultaneously polished with 15 μm diamond compound. Each sample was cut into two pieces, one of which was subsequently annealed at 1300° for 2 hours in flowing argon. Disks of 3 mm in diameter were cut from bulk samples.
AEM characterization of SiC fiber/AIN composites
Authors: Park K. , Sung C. 
Published: June 2020

SiC fiber (15 vol. %)/AlN composites were fabricated by hot pressing at 1650°C and 17.6 MPa using a 4Ca(OH)2·Al2O3 sintering aid under vacuum atmosphere. Creep tests for the composites were conducted at compressive stress of 50 MPa and at 1120°C for 48 hours under oxygen atmosphere. Cross-sectional TEM samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector. Selected area diffraction (SAD), convergent beam electron diffraction (CBED), and energy dispersive X-ray spectroscopy (EDXS) were used to identify the microstructure and microchemistry of the matrix, fiber, and matrix/fiber interface of the composites.Generally, the AIN matrix contained a liquid phase at grain boundaries and a high density of dislocations within the grains (Fig. 1(a)). Most of the additives were present at the grain boundaries. Fig. 1(b) shows a SAD pattern from the liquid phase at the grain boundaries. The liquid phase was identified as Ca12Al14O33 with a cubic structure (a = 1.198 nm).
Investigation of a washer embedded in an orbiter vehicle tile
Authors: Kim H. S. , Cummings V. J. 
Published: June 2020

At NASA’s Kennedy Space Center (KSC), an engineering debris team performs a post-landing inspection of the space shuttle orbiter for debris and for anomalies in the thermal protection system. The areas of inspection and debris sampling include the orbiter windows, lower surface orbiter tiles, reinforced carbon-carbon panels of the orbiter wings, and the external tank (ET)/orbiter umbilicals.On October 18, 1989, the space shuttle Atlantis was launched from launch pad 39B at KSC. Atlantis landed on runway 23 at Edwards Air Force Base, California on October 23, 1989. During the post-landing inspection performed October 23-24, 1989, a washer, approximately 1/2 inch in diameter, was found embedded in one of the lower surface tiles forward of the LH2 ET/orbiter umbilical area. The washer was oriented perpendicular to the airflow, and approximately half of the washer protruded into the aerodynamic flow.The washer was submitted to the NASA KSC microchemistry laboratory for examination and elemental and phase analysis.
Quantitative TEM analysis of microstructural anisotropy
Authors: Dahmen U. , Thangaraj N. , Kilaas R. 
Published: June 2020

Preferred orientation of grain boundaries or interfaces in solids is an important indicator of anisotropy in boundary energy or kinetics. The present study is part of an ongoing investigation of faceting in thin films with the mazed bicrystal microstructure which possesses several unique features that are difficult to measure with standard parameters such as grain size distribution. One of the important characteristics of this microstructure is the degree and type of anisotropy. Figure 1 shows a micrograph with a typical mazed bicrystal microstructure. Only two grain orientations with about equal volume fraction are seen in black and white contrast, respectively. It is apparent that unlike a normal polycrystalline thin film, individual grains in this microstructure have unusual convoluted shapes with both concave and convex regions.The standard stereological method to measure microstructural anisotropy is the rose plot generated from a count of intersections with a reference grid overlaid on the micrograph at different angles.
Diffraction analysis of HREM images from a plasma-deposited iron carbide film
Authors: Siriwardane H. , Fraundorf P. , Pringle O. A. , James W. J. , Newkirk J. W. 
Published: June 2020

The selected area diffraction information in a single HREM image (Fig. 1) of iron carbide, plasma-deposited onto a carbon support film at 300°C is examined. By “selected area diffraction information” we mean power spectra of selectively digitized regions of the negative. The amount of post microscope diffraction analysis that can be done from a single HREM negative is thus illustrated. It is important for us to know whether these crystals belong to a single phase or whether mixtures of phases are present in these films. X-ray characterization of films deposited on glass substrates at the above deposition temperature have always indicated only Fe7C3. Auger depth profiling data from such films on glass and on carbon support films, along with electron diffraction data from these specimens have indicated the presence of some Fe3O4 in these films as well.Six areas of the negative that showed cross-fringes were digitized and are shown in Fig. 2.
HREM study of tetragonal zirconia in Al2O3/ZrO2 multilayers
Authors: Gajdardziska-Josifovska M. , McCartney M. R. , de Ruijter W. J. , Scanlan C. M. , Aita C. R. 
Published: June 2020

The bulk zirconia-alumina system is a model ceramic composite whose fracture toughness is increased via martensitic transformation: i.e. metastable tetragonal zirconia (t-ZrO2) transforms to its stable monoclinic form (m-ZrO2) upon application of stress. To achieve this desirable property it is important to retain a high volume fraction of t-ZrO2 at room temperature. In bulk synthesis this is accomplished by adding dopants, such as yttrium. Recently we have demonstrated that multilayer sputter deposition enables stabilization of tetragonal zirconia without the use of dopants.Amorphous alumina layers were used as termination and restart surfaces for the polycrystalline zirconia layers, as well as an elastic constraint for the t → m transition which involves an anisotropic volume expansion. Double angle X-ray diffraction (XRD) was used to explore the deposition parameters under which t-ZrO2 is retained in the nanolaminate. The zirconia layer thickness was found to be the crucial parameter. The tetragonal phase was detected in all multilayers with ZrO2 layer thickness <20nm.
High-resolution Electron Microscopy characterization of chemically derived titanium aluminide nanomaterials
Authors: Pan Y.-M. , Paul P. P. , Schwab S. T. 
Published: June 2020

Titanium aluminides are a class of intermetallics whose application to a variety of advanced structures may yield substantial improvements in system performance. Before titanium aluminides can realize their full potential, a number of deficiencies such as lack of ductility must be overcome through improved processing. Difficulties inherent in traditional methods have prompted the development of the ultrastructure approach to materials processing. Chemical processing has best potential for ultrastructure control because articles are constructed from atomic level up. The availability of nanostructured materials may be essential to the development of intermetallics with acceptable levels of ductility. The focus of this work is to use high resolution electron microscopy (HREM) techniques to characterize the structure and chemistry of the chemically-derived, nanocrystalline intermetallic powders that have potential to enable ultrastructure processing of advanced intermetallics and alloys.In an attempt to produce salt-free TiAl3, a dilute hexane solution of Ti[N(SiMe3)2]3 was combined with an excess of (AIH3) at room temperature to yield a very fine, steel-gray powder.
Quantitative in situ hot-stage high-resolution Transmission Electron
Microscopy
Authors: Howe J. M. 
Published: June 2020

In situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the dynamics of interfaces at the atomic level. Such information complements detailed static observations and calculations of interfacial structure, and is essential for understanding interface theory and solid-state phase transformations. This paper provides a brief description of particular requirements for performing in situ hot-stage HRTEM and illustrates the use of this technique to obtain quantitative data on the atomic mechanisms and kinetics of interface motion during precipitation of {111} θ phase in an Al-Cu-Mg-Ag alloy.The specimen and microscope requirements for in situ hot-stage HRTEM are not much different from those of static HRTEM, except that one must have a heating holder and equipment for recording and analyzing dynamic images. At present, most HRTEMs are equipped with a TV-rate camera, possibly combined with a charge-coupled device camera. An inexpensive way to record in situ HRTEM images is to send the output from the TV-rate camera directly into a standard VHS format videocassette recorder (VCR).
Characterization of a monolayer graphitic structure
Authors: Lin X. , Wang X. K. , Dravid V. P. , Ketterson J. B. , Chang R. P. H. 
Published: June 2020

For small curvatures of a graphitic sheet, carbon atoms can maintain their preferred sp2 bonding while allowing the sheet to have various three-dimensional geometries, which may have exotic structural and electronic properties. In addition the fivefold rings will lead to a positive Gaussian curvature in the hexagonal network, and the sevenfold rings cause a negative one. By combining these sevenfold and fivefold rings with sixfold rings, it is possible to construct complicated carbon sp2 networks. Because it is much easier to introduce pentagons and heptagons into the single-layer hexagonal network than into the multilayer network, the complicated morphologies would be more common in the single-layer graphite structures. In this contribution, we report the observation and characterization of a new material of monolayer graphitic structure by electron diffraction, HREM, EELS.The synthesis process used in this study is reported early. We utilized a composite anode of graphite and copper for arc evaporation in helium.