bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.