bluuebunny/crossref_metadata_2025 huggingface dataset:
Data acquisition and processing for automated electron microscopy
Authors: Krivanek O.L. , de Ruijter W.J. , Meyer C.E. , Leber M.L. , Wilbrink J.
Published: June 2020

Automated electron microscopy promises to perform many tasks better and faster than a human operator. It should also allow the operator to concentrate on the larger picture without having to worry about countless details that can be best handled by a computer. It requires three essential components: 1) data acquisition system that provides the computer with high-quality data on line, 2) computer and software able to analyze the incoming data in real time, and 3) control links that enable the computer to adjust the important microscope parameters.

An optimized system architecture is shown schematically in Fig. 1. The microscope is equipped with various microprocessors that control its hardware, and provide data processing abilities devoted to different types of signals (e.g., X-ray spectra). These microprocessors use a standardized communication protocol to communicate over a standard network (such as AppleTalk or Ethernet) with a “master computer”, which provides the user interface, as well as the computing power necessary to handle the most demanding tasks.
HVEM tomography: A new tool for the cell biologist
Authors: Frank Joachim
Published: June 2020

The technique of three-dimensional imaging with the transmission electron microscope is a new tool ready to be used by the cell biologist. By itself, the transmission microscope is not capable of producing 3D images, but it allows collection of a tilt series of projections in a wide angular range. From such a series, a 3D image can be reconstructed using established mathematical principles. The first reconstructions of this kind were obtained by Walter Hoppe’s group in 1974, but the full potential of this approach was not realized until the mid-80’s when computers with sufficient speed and memory became available.

Especially within the past three years, there has been a rapid development in the areas of instrumentation, computation, and visualization. New tilt stages meet the demands of high accuracy and wide angular coverage. Direct image readout systems and on-line control of the microscope make it possible to design automated data collection systems.
STEM measurement of subcellular water distributions
Authors: Leapman R.D. , Sun S.Q. , Shi S-L. , Buchanan R.A. , Andrews S.B.
Published: June 2020

Recent advances in rapid-freezing and cryosectioning techniques coupled with use of the quantitative signals available in the scanning transmission electron microscope (STEM) can provide us with new methods for determining the water distributions of subcellular compartments. The water content is an important physiological quantity that reflects how fluid and electrolytes are regulated in the cell; it is also required to convert dry weight concentrations of ions obtained from x-ray microanalysis into the more relevant molar ionic concentrations. Here we compare the information about water concentrations from both elastic (annular dark-field) and inelastic (electron energy loss) scattering measurements.

In order to utilize the elastic signal it is first necessary to increase contrast by removing the water from the cryosection. After dehydration the tissue can be digitally imaged under low-dose conditions, in the same way that STEM mass mapping of macromolecules is performed. The resulting pixel intensities are then converted into dry mass fractions by using an internal standard, e.g., the mean intensity of the whole image may be taken as representative of the bulk water content of the tissue.
Energy-filtered reflection electron microscopy and reflection high-energy electron diffraction on Zeiss 912 TEM
Authors: LIU JINGYUE
Published: June 2020

In reflection electron microscopy (REM) and reflection high energy electron diffraction (RHEED) the average path length of the elastically scattered electrons in the crystal ranges from 10 -100 nm and a significant portion of the electrons in the RHEED pattern spots used for imaging is inelastically scattered. The excitations of surface plasmons, bulk plasmons and valence electrons involves energy losses of 10 ∽30 eV. Thus the image contrast and resolution in REM are degraded due to chromatic aberration of the objective lens. The use of energy filters in a TEM should offer significant improvement in resolution and contrast of REM images. We present here some new results on the investigation of resolution limit and contrast mechanisms in energy filtered REM images.

The experiments were performed on a Zeiss 912 TEM fitted with an Omega magnetic imaging energy filter. Digital RHEED patterns and REM images were acquired into 1024 pixels by 1024 pixels via a Gatan 679 CCD camera fitted to the microscope.
Compositional biological mapping with x-rays in the electron microscope
Authors: LeFurgey Ann , Kopf D.A. , Ingram Peter
Published: June 2020

New ideas in microprobe analysis over the last decade have refuted the notion that electron probe xray imaging is limited to multispectral data as qualitative maps. Electron microscopy is still the most widely used technique for high resolution imaging of biological materials. The acquisition and processing of digital quantitative elemental images of one to several cells in an electron microscope is now accomplished with advanced, commonly available microcomputers. A system developed in our laboratories uses a graphics-based microcomputer to acquire spectrally filtered xray data that is fitted to standards, to display the data and images on-line and in real time, and to correct the multispectral image with regard to specimen drift. Statistics in the data acquisition is the limiting factor in both the image resolution and the ability to automatically recognize regions which need longer acquisition times.

Except in routine clinical or diagnostic situations, specimen preparation requires the tissues or cells to be rapidly frozen in a viable state in order to preserve their inherent elemental and anatomical integrity.
Nano-probe microanalysis of grain boundary chemistry in YBa2Cu4O8 and its relationship to weak-link behavior
Authors: Wang Z.L. , Brynestad J. , Kroeger D.M. , Sun Y.R. , Thompson J.R. , Williams R.K.
Published: June 2020

Weak-link behavior in high temperature superconductors limits bulk applications of polycrystalline high Tc compounds. Possible sources of the effect include grain boundary (GB) disorder, microcracks and nonstoichiometric material at grain boundaries. Recently, electron energy-loss spectroscopy (EELS) studies of YBa2Cu3O7-x (Y123) have shown that grain boundary oxygen deficiency is correlated with the crystallographic misorientations of between the Y123 grains. Studies of grain boundary chemistry in YBa2Cu4O8 (Y124) by nano-probe energy dispersive X-ray spectroscopy (EDS) and EELS are reported in this paper. Transmission electron microscopy (TEM) studies were performed at 100 kV in a Philips EM400 TEM/STEM equipped with a field emission gun (FEG), which generates an electron probe smaller than 2 nm in diameter. The cation composition was determined by EDS and the O:Ba composition was determined using EELS. Kikuchi patterns were recorded from both sides of the grain boundaries to determine the misorientation of the two adjacent grains.

The observation of a pre-edge peak (Fig. 1) near the oxygen K ionization edge (O K) is related to the hole states produced by the O 2p state and Cu 3d states.
Simultaneous high-resolution SEM and STEM of organic compounds and biological macromolecules
Authors: Apkarian R.P. , Robinson K.A. , Yamasaki Y. , Menger F.M.
Published: June 2020

A simple spray mounting preparation of hydrocarbon based macromolecules onto coated grids or Si chips was employed for secondary electron (HRSEM) or in tandem with scanning transmission electron (STEM) imaging. The grid specimens were staged in the lens of a Topcon DS-130 SEM equipped with a Schottky field emission (SFE) source. A 1 nm probe, created at 25 kV, elicited low radiation damage to the molecules on the formvar support. Molecules on grids were stabilized with heavy metal stains and contrast enhanced by a 1 nm fine-grain Cr film. The strategy was to generate sufficient SE-I electrons for above-lens detection simultaneous with the collection of transmitted electrons by the below specimen STEM detector.

The bromine salt of a synthetic amphiphile, N-tetracosanyl-tetraethylenepentaammonium pentabromide was produced as a preliminary micelle solution of [10mM]. After vigorous sonication the solution was diluted to [1mM] with dH2O, filtered through 0.65μm polycarbonate membrane, and mixed vol./vol. with 2% uranyl acetate (freshly prepared and filtered through 0.2μm PC membrane).
Data acquisition as a design parameter in the modern AEM
Authors: Zaluzec Nestor J.
Published: June 2020

Data is the essential component of all scientific investigations. From this information we, as experimentalists, formulate ideas, test theories, derive conclusions and design new experiments to continue our explorations of materials both in the physical and life sciences. Clearly without it we would be left with literally nothing to do. With that thought in mind it should be intuitively obvious that there are two essential aspects of all studies. The first is a well formulated experiment whose results will provide relevant data and second that the methodology/instrument we choose to utilize to collect the data has the ability to acquire the information we need to obtain about an object or phenomenon. By extension one would assume that having chosen an instrument that it was designed with the thought in mind to maximize the amount and quality of information for which it is being employed.

We can break down any experimental system into the following areas: the environment and manipulation of the specimen in the instrument, the probe used to investigate the specimen, the detectors used to measure information, and finally the transfer of data from the experiment to the outside world.
Electron crystallography of helical protein assemblies
Authors: Caspar D.L.D. , DeRosier D.J. , Diaz R. , Morgan D.G. , Melanson L.A. , Owen C. , Ranck J-L. , Ruiz T.
Published: June 2020

Electron cryomicroscopy provides structural information on two dimensional crystals. Several membrane proteins have been solved to better than 4Å resolution. This class of structure has been difficult to attack by x-ray diffraction. Another class of structures that is difficult to solve by x-ray diffraction but may be amenable to electron microscopy is the helical protein assembly. Most of our knowledge of this class has come from electron microscopy although generally the work has revealed detail to a modest resolution of about 20 Å and in two special cases to about 10Å resolution. We have been trying to extend the methods for all helical structures in a manner analogous to those used for two dimensional crystals. The difference is that the scattered electron beams from helices are much weaker than those from two dimensional crystals and the signal-to-noise ratio is poorer. We have developed methods for automatically processing large numbers of particles to extract signal from noise.
Bravais lattice determination from a single CBED pattern
Authors: Zuo J. M.
Published: June 2020

Traditional methods for Bravais lattice determination of unknown materials using electron diffraction involve symmetry determination from several low index zone axis diffraction patterns, measuring the distances between spots or disks and indexing them by trial and error method. Such methods are ofte repetitive, error prone and difficult, if not impossible, for low-symmetry crystals. Thus a simpler, accurate, and automated method for lattice determination is highly desirable in electron diffraction. Here new method of Bravais lattice determination using an arbitrary single convergent beam diffraction (CBED pattern is summarized. A full description of the method has been submitted for elsewhere. The method uses the deficiency lines of high order and high order Laue zone (HOLZ) reflections to measure the primitive cell of the zone axis, and use the standard Krivy and Gruber procedure to reduce this arbitrary primitive cell to a unique Niggli cell, and thus the Bravais cell.
A streamlined procedure for acquisition and measurement of electron-diffraction patterns
Authors: Dufner D.C. , Ehrman J.M.
Published: June 2020

Electron diffraction is one of the most widely used techniques in the characterization of materials in the TEM. There are a number of computer programs used for measuring, indexing, and simulating electron diffraction patterns (EDP’s), but many are stand-alone programs and require significant user interaction. For example, EDP’s obtained on the JEOL 2010 in the Texas A&M Electron Microscopy Center can be measured with the Electron Diffraction Pattern Analysis software provided with the Oxford Instruments eXL system. A separate program is used to acquire the pattern from the TV camera output, while the EDP Analysis program requires the user to select the transmitted and diffracted beams for measurement. Only two values of d-spacings are calculated by this program, which places an additional burden on the user to select other spots in order to get a more complete measurement of the pattern.

In this work, we propose a more streamlined approach in acquiring, saving, and measuring EDP’s on a PC-based computer system. A schematic of the hardware/software configuration is shown in Figure 1.
Bicrystallography and electron diffraction
Authors: Dravid Vinayak P.
Published: June 2020

Traditionally grain (or phase) boundaries have been modelled using coincidence site lattice (CLS)-type geometrical treatments. However, CSL utilizes only the latticetranslational symmetry of the crystals and is not applicable to nonsymmorphic crystals or in cases where the point group symmetry elements are important. Pond and coworkers, in an elegant series of papers proposed a complete geometric description of bicrystal containing an interface, i.e. bicrystallography. The use and application of bicrystallography has important implications for interface/surface structure, thin film growth and small particle studies.

Theoretical development of bicrystallography (or tricrystallography..etc.) is rather complete. However, same is not the case for experimental bicrystallography. There two important methods for bicrystal diffraction experiments: one is the plan-view technique, while the other involves edge-on interface parallel to the electron beam. Plan-view CBED can determine loss of symmetry due to RBT as demonstrated by Eaglesham et al. Dravid et al. used plan-view CBED to probe the symmetry of NiO-ZrO2(CaO) eutectic interfaces.
Rapid preservation of biological specimens for light and electron microscopy and for immunohistochemical and immunocytochemical studies using microwave fixation
Authors: Login Gary R. , Dvorak Ann M.
Published: June 2020

The use of microwave fixation for biological specimens is very promising and may provide unique biological insights and methodological advantages over standard chemical and physical fixation approaches. Microwave fixation methods are fast (e.g., completed in seconds or less) and they make analysis of fast cellular events such as vesicle formation and fast reorganization of vitamin D receptors possible or more precise. This newly developed, rapidly emerging technology is playing an increasingly important role in providing new insights into cell biology.

Microwave fixation is used by many investigators as an all encompassing description of a variety of methods where microwave irradiation is used in the fixation process. Certain limitations and possible advantages are associated with different microwave fixation methods. For example, the use of aldehydes during irradiation may influence the preservation of antigenicity of cellular macromolecules. Therefore, it is useful to classify microwave fixation methods according to the following criteria: a) chemical environment around the specimen during irradiation, b) duration of microwave exposure, and c) the temporal relationship between the use of microwave irradiation and the use of other chemical or physical fixation modalities.
Analytical Electron Microscopy of bimetallic Pt-Rh Alloy Catalysts
Authors: Lakis Rollin E.
Published: June 2020

The goal of this investigation is to correlate the catalyst preparation procedure and the resulting particle microstructures with catalytic performance. The Pt-Rh system was selected because it is widely utilized in pollution control and for its potential application in the low temperature reduction of nitric oxide.

Two bimetallic catalysts were prepared for this study. They were both made by the aqueous impregnation of the respective metal chlorides into γ-alumina and contain approximately 0.5 wt% Pt and 0.5 wt% Rh. Catalyst A was prepared by a method which is designed to promote intimate mixing of the two metals after reduction. PtCl4 was impregnated in the support material and air dried at room temperature for 24 hours. This material was then oxidized at 500°C in flowing O2 for 15 hours. Following oxidation, the Rh was deposited, air dried, and reduced at 300°C for 15 hours, in flowing H2. Catalyst B was made by first impregnating the Rh, and after drying, oxidizing the material at 500°C in flowing O2 for 15 hours.
Analysis of small particles via HRTEM lattice images: Contrast mechanisms and effects of particle shape
Authors: Barry John C.
Published: June 2020

It is well known that because of their large surface area, small particles possess unusual physical properties. What is not so well known is that small particles often exhibit unusual diffraction behaviour. The diffraction behaviour of small particles is a function of their size, shape and chemical composition. This diffraction behaviour is essentially the same for small precipitates within a parent matrix as it is for small particles dispersed on the surface of a thin film.
The unusual diffraction behaviour of small particles falls into two categories.

1)

The apparent lattice fringe spacing may differ significantly from the actual lattice parameter for particles of irregular shape.

2)

One of the surprises of dynamical diffraction is that structures with heavy atoms do not necessarily give strong scattering into Bragg beams. For small particles this means that light elements are often visible on the surfaces of heavy-atom particles.

In this paper an analysis of small particles is made with reference to the microscopic diamonds found in oxidized acid residues from carbonaceous chondrite meteorites.
The Three-Dimensional shape of carbon nanotubes by High Resolution Electron Microscopy
Authors: Li Z. G. , Liang L. , Fagan P.J. , van Kavelaar M.
Published: June 2020

Following the discovery of a large scale synthesis of fullerenes, the existence of the related carbon nanotubes was suggested by high resolution electron microscopy (HREM). Larger scale syntheses of these nanotube-rich materials has now been reported and has sparked interest worldwide. Because the HREM technique essentially observes the projection of a three dimensional object onto a two-dimensional plane, the three dimensional shape of the object is usually not apparent in typical HREM images. However, as we report here, by rotating along the axis of single carbon nanotube, and recording the images in succession by HREM, the non-cylindrical nature of these tubes is revealed, especially near the sealed ends of the nanotubes. In addition, from electon diffraction and X-ray diffraction, we find the spacing between the planes to be 3.398(8) Å on average. This is in contrast to earlier reports which suggested an interlayer distance of 3.35 Å, similar to the graphite interplanar spacing.
High-resolution microscopy of carbon nanotubes
Authors: McKernan Stuart , Kotula Paul G. , Owens Dale W. , Barry Carter C. , Weaver J. H.
Published: June 2020

The presence of fullerenes and carbon nanotuhes in the residue of plasma discharge electrodes has recently been documented. The occurrence of 5-fold and 7-fold coordinated carbon rings in otherwise 6-fold coordinated graphene sheets apparently provides sufficient variation of the familiar graphite morphology to form spheres and cylinders. The spherical structure of the fullerenes has been studied in relatively more depth than the cylindrical structure of the carbon nanotubes.

Carbon nanotubes may be considered as individual graphene sheets rolled up into cylinders. These cylinders are stacked concentrically with a spacing between the layers analogous to the stacking of sheets in graphite of c=3.4 Å . This spacing imposes geometrical constraints on the circumference of the cylinders. Variations of the cylinder diameter from the value required to give the exact spacing may be expected, due to the discrete nature of the sheets. For large cylinders this variation may not be very noticeable, and may be accommodated as small strains within the tube.
Facet crystallography by electron diffraction in the SEM
Authors: Sutliff J.A.
Published: June 2020

The study of fracture in engineering materials often involves an analysis of the crystallography of the fracture surface. In particular, the question is often asked, "What, if any, low index plane corresponds to the plane of a particular fracture surface facet?" To determine the crystallographic plane of a surface facet, it is necessary to determine the orientation of the grain and the orientation of the facet plane relative to the grain. For example, if a euhedral crystal of known orientation is fractured, an optical reflection goniometer can be used to measure the angles between a facet and known crystal faces in order to deduce the direction of the facet normal. Laue x-ray diffraction patterns taken from well aligned facets can also be analyzed to determine the orientation of the crystal normal to the facet. In many engineering materials, the facets are small, usually as a result of a small grain size in the material, and it becomes impractical to use these techniques.
Approaching an absolute with SEM metrology
Authors: McAfee George H.
Published: June 2020

The Scanning Electron Microscope remains one of the most universal tools in the semiconductor industry. While it gained prominence in the areas of inspection and analysis, it is also a very capable metrology tool. There is a wide selection of S.E.M.′s available that are dedicated to line width measuring; however, this article discusses film thickness measuring during cross-sectional S.E.M. analysis.

As with any metrology system, a process should begin with a certified and traceable measurement standard. N.I.S.T. SRM 484f was the standard employed for this experiment. A gauge and capability study was first performed on a Nanometrics CWIKSCAN II FE S.E.M.. Long range repeatability was calculated at 1.57% Figures 1 and 2 show the micrograph and video signal data respectively from the N.I.S.T. standard. Note the cursor position and measurement value on figure 2. The 1.072μm value agrees very well with the certified value of 1.067μm.

• It is important to note that the aspect ratio on most CRT screens is not 1:1. Therefore, if any electronic manipulation of the image is required for cursor alignment, the system calibration must be performed at the same orientation where the measurements will be taken.
Electron microscopy of defects in silicon-on-insulator structures formed by selective epitaxial growth
Authors: Weng-Sieh Z. S. H. , Lou J. C. , Oldham W. G. , Gronsky R.
Published: June 2020

In the interest of obtaining increased integrated circuit device density, a relatively new technology known as selective epitaxial growth (SEG) of silicon is being explored, especially for improved isolation of devices including possible three dimensional (vertical) integration. This technology involves the deposition and selective nucleation and growth of silicon from the vapor phase, seeded by the silicon substrate. The process is “selective” because nucleation and growth occurs on the silicon substrate but is prohibited on the oxide. The epitaxial silicon proceeds to grow upward and laterally over the oxide.

Silicon deposition was performed in a horizontal hot-walled low pressure chemical vapor deposition (LPCVD) reactor. A dry thermal oxide was grown on the substrates, patterned, and etched to create seed windows. A 900 °C prebake was performed at a pressure of 6 torr in a hydrogen ambient for a period of 15 minutes, with in some cases, a small concentration (approximately 0.025%) of dichlorosilane (DCS) gas, and deposition was performed at 850 °C through the decomposition of DCS gas: SiH2Cl2 -> Si(s)+ 2HCl(g).
Formation of β-FeSi2, by thermal annealing of Fe-implanted (001) Si
Authors: Lin X.W. , Liliental-Weber Z. , Washburn J. , Desimoni J. , Bernas H.
Published: June 2020

Epitaxy of semiconducting β-FeSi2 on Si is of interest for optoelectronic device technology, because of its direct bandgap of ≈0.9 eV. Several techniques, including solid phase epitaxy (SPE) and ion beam synthesis, have been successfully used to grow β-FeSi2 on either Si (001) or (111) wafers. In this paper, we report the epitaxial formation of β-FeSi2 upon thermal annealing of an Fe-Si amorphous layer formed by ion implantation.

Si (001) wafers were first implanted at room temperature with 50-keV Fe+ ions to a dose of 0.5 - 1×1016 cm−2, corresponding to a peak Fe concentration of cp ≈ 2 - 4 at.%, and subsequently annealed at 320, 520, and 900°C, in order to induce SPE of the implanted amorphous layer. Cross-sectional high-resolution electron microscopy (HREM) was used for structural characterization.

We find that the implanted surface layer ( ≈100 nm thick) remains amorphous for samples annealed at 320°C for as long as 3.2 h, whereas annealing above 520°C results in SPE of Si, along with precipitation of β-FeSi2.
Conduction edge strain splitting in Ge-Si quantum wells using EELS
Authors: Batson P.E. , Morar J.F.
Published: June 2020

Ge/Si quantum well structures show a high hole mobility as the heavy hole bands are shifted to lower energy under bi-axial strain produced by lattice mismatch between the well and the Si substrate. This strain can also split and shift the conduction band edge in the well to below that of Si, producing a Type I quantum well capable of photo-luminescence. In previous work, we have shown that the conduction bandstructure can be obtained using EELS in the relaxed Ge/Si alloy system. Also, we have noticed that the heterojunction band offset can be obtained from EELS because the Si 2p core level is a constant energy reference level throughout the alloy composition. In this report, we show that a detailed fitting of the shape of the Si L2,3 edge can obtain the bi-axial strain splitting of the conduction band edge as a function of position inside a quantum well. This information can then be correlated with annular dark field images of the cross sectioned well.
EELS study of NiSi2Si(111) interface in STEM
Authors: Wong Kaikee , Batson P. E. , Silcox John
Published: June 2020

Experimental studies of the NiSi2/Si(111) interface are difficult since the interface is only 3 Å wide and separating the interfacial signals from bulk signals is hard. When equipped with an EELS detector, a STEM becomes a powerful tool in studying the electronic properties of an interface. By locating the electron probe at the interface, at bulk Si and at bulk silicide, the electronic properties of the NiSi2/Si(111) interface can be identified.

An A-type NiSi2 template was grown using Tung's scheme. To increase the film thickness to 200 Å, 60 Å of Ni was deposited on the template and annealed at 550°C for 10 min. A cross-section TEM sample was prepared by dimpling and ion-milling. Within 70 Å of the interface, the specimen stoichiometry was found to be that of NiSi2 with TEM lattice imaging and x-ray EDS. Beyond that the concentration of Ni increased and approached that of NiSi. EELS measurements were carried out at the IBM VG HB501 STEM operating at 120 keV equipped with a CCD EELS detection system and a Wien filter.
Applications of atom-probe field-ion microscopy to the study of interfaces
Authors: Burke M.G. , Miller M.K.
Published: June 2020

The near-atomic resolution and elemental sensitivity of the atom probe field-ion microscope (APFIM) permit the detailed microstructural and microchemical analysis of phases and interfaces in a variety of materials. To overcome the limitation of this technique in terms of volume of material sampled, it is frequently necessary to perform complementary microstructural studies by other techniques such as analytical electron microscopy (AEM) or auger electron spectroscopy (AES). With such complementary data, the microstructural significance of the APFIM data can be exploited. In addition to specifically evaluating segregation at interfaces, the high spatial resolution of the APFIM technique can be used to determine microcompositional fluctuations in the vicinity of interfaces. In this overview, some selected examples illustrating the application of the APFIM technique to the evaluation of segregation to interfaces are presented.

Considerable research has been performed on low alloy steels, particularly those such as A533B which are used in the pressure vessels of nuclear reactors.
Characterization of sheared liquid crystalline polymers by light microscopy
Authors: Viney Christopher , Putnam Wendy S.
Published: June 2020

It is widely observed that nematic and cholesteric liquid crystalline materials develop a one-dimensional periodic microstructure during and/or after a uniaxial draw or simple shear (Fig. 1). This property is common to lyotropic and thermotropic examples of both small-molecule and polymeric liquid crystals. The periodic microstructure gives rise to a banded texture between crossed polars (Fig 2).

A material under load will extend more readily if the microstructure contains crimps that can be straightened, compared to the extension that is achieved if covalent backbone bonds are highly aligned along the direction of load. The microstructure in Fig. 1 therefore is regarded as a stiffness-reducing defect. Two classes of stiff polymer that are produced from lyotropic solutions do not exhibit banded textures: the highest modulus variant of poly(p-phenyleneterephthalamide) (Kevlar), and various natural silk fibers. However, a banded texture is present in the less stiff variants of Kevlar, and also in silk fibers that have been drawn by hand from natural secretions, which demonstrates that the defect is not intrinsic to liquid crystalline molecular order, but is related to processing.
Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions
Authors: Talmon Yeshayahu
Published: June 2020

To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.

To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.
Polymer-induced wormlike-to-spherical micelle transition in surfactant solutions
Authors: LIN ZUCHEN
Published: June 2020

In various applications important to chemical, pharmaceutical, petroleum, and mineral processing industries, surfactant molecules are present in solution not alone but along with synthetic or biological macromolecules. The presence of polymer molecules gives rise to changes in the solution and its interfacial properties as compared to the corresponding polymer-free systems.

The interaction between surfactant and polymer results in association of the two, which affect many properties of the system, especially the rheological ones. Recently, a polymer induced transition from non-Newtonian to Newtonian behavior was observed in the CTAB/NaSal system. This effect was attributed to a polymer-induced break-up of the worm-like micelles into spherical ones. This interpretation can be tested directly by microscopic observation.

In this study, interactions between poly(vinylmethylether) (PVME) or poly(propyleneoxide) (PPO) (Aldrich, WI) and the nonionic surfactant pentaethylene glycol mono-dodecyl ether (C12E5) (Nikkol, Japan) or the cationic surfactant cetyltrimethylammonium bromide (CTAB) (Aldrich) with presence of sodium salicylate (NaSal) (Mallinkordt, MO) were examined by cryo-TEM and rheometry.
Real-time cryo-deformation of polypropylene and impact-modified polypropylene in the transmission electron microscope
Authors: Cieslinski Robert C. , Craig Silvis H. , Murray Daniel J.
Published: June 2020

An understanding of the mechanical behavior polymers in the ductile-brittle transition region will result in materials with improved properties. A technique has been developed that allows the realtime observation of dynamic plane stress failure mechanisms in the transmission electron microscope. With the addition of a cryo-tensile stage, this technique has been extented to -173°C, allowing the observation of deformation during the ductile-brittle transition.

The technique makes use of an annealed copper cartridge in which a thin section of bulk polymer specimen is bonded and plastically deformed in tension in the TEM using a screw-driven tensile stage. In contrast to previous deformation studies on solvent-cast films, this technique can examine the frozen-in morphology of a molded part.

The deformation behavior of polypropylene and polypropylene impact modified with EPDM (ethylene-propylene diene modified) and PE (polyethylene) rubbers were investigated as function of temperature and the molecular weight of the impact modifier.
TEM and image analysis to quantitatively describe the phase behavior in copolymer/homopolymer/homopolymer blends: Effect of the copolymer sequence distribution
Authors: Winey Karen I. , Galvin Mary E.
Published: June 2020

Polymers are typically immiscible with one another, that is phase separated, in the absence of specific favorable intermolecular interactions, because the combinatorial entropy of mixing is small. Copolymers, polymer molecules containing more than one type of monomer unit, are frequently used to induce miscibility in homopolymer mixtures. Extensive work has previously established the importance of the copolymer composition, though the sequence of monomers within the copolymer has received less attention. Copolymers with random and with alternating sequences of monomers have been synthesized and mixed with homopolymers to evaluate the importance of the sequence distribution on blend miscibility. Blend miscibility determinations using differential scanning calorimetry and visual inspection can be erroneous when the glass transition temperatures of the phases are similar or the domains are small compared to the wavelength of light. Thus, we have used transmission electron microscopy to study the phase behavior of these polymer blends.

Blend samples (∼30 mg) of poly(styrene-co-methyl methacrylate) (PS-PMMA), homopolystyrene (PS), homopoly(methyl methacrylate) (PMMA) were prepared by casting from tetrahydrofuran and annealing at 150°C for 7 days.
Microwave-stimulated heavy metal staining of polymer blends for TEM
Authors: Wood Barbara A.
Published: June 2020

Microwave methods for fixation and staining of biological samples for microscopy have been under development for a decade. While microwave ovens are routinely used in the synthetic polymer field for sample digestion and ashing, potential microwave staining techniques for TEM of polymers have yet to be thoroughly investigated. Preliminary experiments have demonstrated that copper grids do not cause arcing problems in the microwave, and that most types of polymer sections can be safely and conveniently stained in an industrial microwave oven. The staining agent used was ruthenium tetroxide vapor generated from ruthenium trichloride. Improvements in the speed and selectivity of staining are attributed in part, but not entirely, to the increased reaction rates at higher temperatures compared to standard room temperature vapor staining techniques. Stringent waste disposal regulations make microwave staining an attractive method from the industrial hygiene point of view, with a minimum of toxic waste generation compared to staining with RuO4/CCl4 solutions.
Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ
Authors: Wang J.-Y. , Zhu Y. , King A.H. , Suenaga M.
Published: June 2020

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.

Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).
Grain boundaries in ceramics for solid oxide fuel cells
Authors: Tsai F. , Cowley J. M. , Jiang S. S. , Wagner J. B.
Published: June 2020

Calcia stabilized zirconia(CSZ) and ceria(CeO2) doped with rare-earth oxides have been used as electrolytes in solid oxide fuel cells(SOFC). Such ceramics are usually good ionic conductors for oxygen ions at elevated temperatures. A few studies have attempted to correlate the microstructures with ionic conductivity. It was suggested that the grain boundaries play a role in depressing the ionic conductivity. In their study, it was found that continuous “thick” boundary layers of secondary phases existed on the grain boundaries and blocked ion transport.

In the present studies, high resolution transmission electron microscopy has been used to investigate the microstructures of grain boundaries in zirconia doped with calcia (ZrO2 + 13%CaO) and ceria ceramics doped with calcia (CeO2 + 10% CaO). The ceramics was made in our Solid State Ionics Laboratory. Transport number measurements on zirconia samples showed that the transport number tO2- =1 from PO2 = 10-17 atm to PO2 =1 atm.
Bayesian removal of noise for increased sensitivity in vector pattern recognition lattice imaging of interfaces
Authors: Fei L. , Fraundorf P.
Published: June 2020

Interface structure is of major interest in microscopy. With high resolution transmission electron microscopes (TEMs) and scanning probe microscopes, it is possible to reveal structure of interfaces in unit cells, in some cases with atomic resolution. A. Ourmazd et al. proposed quantifying such observations by using vector pattern recognition to map chemical composition changes across the interface in TEM images with unit cell resolution. The sensitivity of the mapping process, however, is limited by the repeatability of unit cell images of perfect crystal, and hence by the amount of delocalized noise, e.g. due to ion milling or beam radiation damage. Bayesian removal of noise, based on statistical inference, can be used to reduce the amount of non-periodic noise in images after acquisition. The basic principle of Bayesian phase-model background subtraction, according to our previous study, is that the optimum (rms error minimizing strategy) Fourier phases of the noise can be obtained provided the amplitudes of the noise is given, while the noise amplitude can often be estimated from the image itself.
Recent advances and opportunities in magnetic recording materials
Authors: Kryder Mark H.
Published: June 2020

Recording densities in magnetic recording products manufactured today are of the order of 200 Mbit/in. However, it is projected that densities as high as 10 Gbit/in will be achieved in the future. To achieve this, substantial improvements in the thin film magnetic materials used for magnetic heads and media are required.

To support higher recording density in thin film media, it is necessary to increase the coercivity, while simultaneously achieving small grain size and small intergranular coupling. To achieve high coercivity, materials with large magnetocrystalline anisotropy are used, while to achieve small, well-isolated grains, special materials are used and deposited under conditions which promote either heavily voided grain boundaries or the segregation of non-magnetic species to the grain boundaries. It is also thought to be important to control the orientation of the crystallites so that a preferred axis of magnetization lies parallel to the direction of recording.
Correlation of microstructural and magnetic properties of longitudinal recording media using TEM
Authors: Nolan T. P. , Sinclair R. , Yamashita T. , Ranjan R.
Published: June 2020

Cobalt alloy on chromium thin film media are used in industry because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic properties depend strongly on processing conditions and, as will be shown, the resulting microstructure.

A complete structure-processing-properties analysis requires effective measurement of both magnetic and microstructural properties. Direct micromagnetic-microstructural comparison is not yet readily available, but bulk hysteresis loop parameters are reproducible and highly correlated with both desired recording characteristics and microstructures, and so provide a valuable, albeit indirect comparison. Signal to noise (S/N) measurements are also used as a more direct measure of usefulness in a high density disk drive. The nanoscale microstructural features which dramatically affect these bulk magnetic properties are difficult to observe. However, careful combination of TEM techniques, including bright-field, dark-field, high-resolution, selected area diffraction and elongated-probe microdiffraction can determine the subtle microstructural differences.
Co-Thickness dependence of the microstructure of Pt/Co multilayers
Authors: Li Z.G. , Carcia P.F.
Published: June 2020

For Co layer thicknesses less than about 12 Å, Pt/Co multilayers have perpendicular magnetic anisotropy . However, the best magnetic properties are obtained when Co is only ∼4 Å thick, or nearly two atomic layers, and the Pt layer at least twice as thick. We have revealed the microstructure dependence of the Pt/Co multilayers on the Co thicknesses by using high resolution electron microscopy.

We found that for thin Co (∼ 4 Å), Pt/Co multilayers had (111)-fcc texture and a coherent lattice with interplanar spacing of ∼ 2.2 Å. The lattice coherence depended only on the Co thickness and was independent of the film preparation method. However, multilayers synthesized by vapor-deposition or Xe-sputtering, which impart less energy to the growing film, consisted of a larger single crystal volume of Pt/Co superlattice, and also had better (111) texture than Ar- or Ne-sputtered multilayers. Fig. 1) and Fig. 2) illustrate these points with atomic resolution images of Ne-sputtered and vapor-deposited multilayers.
Signal transfer efficiency of slow-scan CCD cameras
Authors: de Ruijter W.J. , Mooney P.E. , Krivanek O.L.
Published: June 2020

Slow-scan CCD cameras are helping transmission electron microscopy and electron holography become increasingly quantitative. Accurate characterization of the performance of the cameras can extend this trend by making it possible to extract weak signals from noisy images with optimal precision. The property to be characterized is die performance of the camera in transferring a particular spatial frequency contained in the input electron image to the output image captured by a computer, as a function of the input intensity. Using the concepts and notation of standard signal processing theory, we characterize this performance by introducing signal transfer efficiency (STE) defined as:

where SNRin(K) and SNRout(K) are signal-to-noise ratios at the input and the output of the image detector as a function of spatial frequency k. Signal-to-noise ratio is defined as SNR(K)=SII(K)/Snn(K) where SII(k) and Snn(k) denote the power spectra of the signal and the noise. STE could be regarded as an extension of the use of detection quantum efficiency as a figure of merit for electron image detectors.
Electron holography of vortex lattices in superconductors
Authors: Bonevich J.E. , Harada K. , Matsuda T. , Kasai H. , Yoshida T. , Pozzi G. , Tonomura A.
Published: June 2020

The recent success in observing magnetic vortices in superconductors by means of transmission electron microscopy techniques has opened a new window to investigate the behavior of vortex lattices. We report the first direct observation of 2-D vortex lattices in niobium thin films taking advantage of the high resolution and sensitivity of electron holography.

The experiments were conducted in a 300 keV field emission electron microscope equipped with a cold stage that allows magnetic fields to be applied while the specimen can be maintained from 30 K down to 4.5 K. The Nb specimen is tilted by 45° to the electron beam and the magnetic field is applied in the horizontal direction. The microscope also has a rotatable electron biprism used to form holograms. The thin (70±20 nm) foil specimens were prepared by chemically polishing 2 mm × 2 mm × 30 μm sections of Nb that had been annealed to ∼2000°C in a vacuum of 10-6 Pa.
TiO2 on MgO by PLD: The effect of the substrate treatment
Authors: King Simon , Barry Carter C.
Published: June 2020

The recent demonstration of the epitactic growth of YBa2Cu3O7-x (YBCO) onto (100) MgO passivated by a layer of the inverse spinel Mg2TiO4, combined with the large number of possible reaction products of” widely differing structure (normal spinel (Ti3+), inverse spinel, pseudo-brookite, perovskite) make the MgO-TiO2 system one of the more interesting, and complex, currently under examination.

Over the last few years, Hesse, Bethge and co-workers (see 1 for refs), have applied various microscopal techniques to the study of e-beam evaporated TiO2 onto MgO. The present paper extends this investigation to pulsed-laser deposited (PLD) TiO2 onto MgO. Unlike almost all previous studies of PLD films, pre-characterized “TEM-ready” substrates are used, a technique pioneered by Norton et al, thereby circumventing the possibility of affecting the film morphology during the thinning process. This technique also allows the imaging in the TEM of identical areas both before and after deposition.