bluuebunny/crossref_metadata_2025_split huggingface dataset:
A project for on-line remote control of a high-voltage TEM
Authors: Parvin B. , Agarwal D. , Owen D. , O'Keefe M.A. , Westmacott K.H. , Dahmen U. , Gronsky R. 
Published: June 2020

On-line microscopy commenced with demonstrations for biological and SEM applications. For materials science, a project has recently been established to provide users of the NCEM with remote online access to a 1.5MeV Kratos EM-1500 high-voltage transmission electron microscope via existing wide area networks. Within this project we are developing and implementing a set of tools, protocols, and interfaces to bring transmission electron microscopy on-line for collaborative research. Initially applied to the Kratos, the project will provide increased utilization of this unique instrument with its heretofore restricted access due to its sensitive components and demand for sophisticated operator skills. Additionally, the project will provide computer tools for capturing and manipulating real-time audio and video signals. These tools will be integrated into a standardized user interface that may be used for remote access to any transmission electron microscope equipped with a suitable control computer.Dynamic study of a specimen in an electron microscope requires continuous adjustment of specimen position and orientation under the beam, illumination conditions, focus adjustments, and corrections for aberrations, all based upon the video signal coming from the imaging system.
Further advances in orientation imaging microscopy
Authors: Dingley D.J. 
Published: June 2020

Orientation Imaging Microscopy, OIM, is a relatively new technique which provides an image of the surface of polycrystalline material in which the grains are distinguished by their orientation differences, by the strain within them and the type of grain boundaries that separate them. The technique evolved from the work of Dingley and Venables on application of electron backscatter diffraction EBSD in the scanning electron microscope. In OIM, electron backscatter diffraction patterns are obtained successively at regularly spaced points on a sample surface. At each point, the diffraction pattern is captured, transferred to a computer and automatically indexed. Crystal orientation and diffraction line width are measured. Recent advances have been concerned with post data collection image processing.In the following illustration orientation imaging microscopy was used to investigate the microstructure of submicron aluminium, vapour deposited onto single crystal silicon coated with silicon dioxide. The experimental procedure described in reference 2 was adapted using a Philips XL 30 SEM fitted with a tungsten electron gun.
High-resolution and diffraction contrast imaging of linear islands formed during molecular beam epitaxy
Authors: Loretto D. , Ross F. M. , Lucas C. A. 
Published: June 2020

There is currently a great deal of interest in the growth and properties of 'one-dimensional' structures. This is motivated by scientific curiosity and by the practical urge to fabricate faster, smaller and more efficient electronic and optical devices. It has recently been reported that under certain conditions linear islands can form spontaneously during growth. In this work we investigate linear CaF2 islands which form on Si during molecular beam epitaxy. By combining low resolution diffraction contrast images from plan-view specimens with high resolution images from cross-section specimens we determine that these islands are extremely uniform in width, can be as narrow as 5 nm, and extend over many 10s of μm. We postulate a mechanism for the formation of these novel features based on surface energy minimization.The experimental conditions have been reported in detail elsewhere. Briefly, CaF2 is deposited from an effusion cell onto a Si substrate at 700°C in a vacuum of 1010 Torr.
Interpretation of secondary electron contrast from negative electron affinity diamond surfaces
Authors: Malta D.P. , Posthill J.B. , Humphreys T.P. , Markunas R.J. 
Published: June 2020

Diamond is a wide band-gap semiconductor with many unique physical properties that make it an attractive technological material. One such property is the negative electron affinity (NEA) behavior of the surface when properly terminated with hydrogen or a thin metal layer. The NEA diamond surface exhibits an unusually large secondary electron (SE) yield which is desirable for applications in cold cathode electron emitters of flat panel displays. Examination of NEA diamond surfaces by scanning electron microscopy (SEM) has indicated that a unique mechanism appears to be responsible for the SE contrast in which sub-surface microstructural information is contained. This paper provides a brief interpretation of the origin of SE contrast from the NEA diamond surface.The electron affinity of a semiconductor surface, χ, is defined by the position of the vacuum energy level, E0, relative to the conduction band minimum, Ec (Fig. la). If χ>0, excited conduction band electrons must migrate to the surface and arrive with sufficient kinetic energy to overcome the surface energy barrier in order to escape into vacuum.
Microstructure and microtexture of a Nb-16%Si (DS) Alloy
Authors: Sutliff J. A. , Bewlay B. P. 
Published: June 2020

In-situ composite Nb-Si alloys have been studied by several investigators as potential high temperature structural materials. The two major processing routes used to fabricate these composites are directional solidification and extrusion of arc-cast solidified ingots. In both cases a stable microstructure of primary Nb dendrites in a eutectoid of Nb and Nb5Si3 phases is developed after heat treatment. The Nb5Si3 phase is stable at room temperature and forms as a decomposition product of the high temperature Nb3Si phase. The anisotropic microstructures developed by both directional solidification and extrusion require evaluation of the texture to fully interpret the fracture and other orientation dependent mechanical behavior of these composites.In this paper we report on the microstructural characterization of a directionally solidified (DS) and heat treated Nb-16 at.%Si alloy. The microtexture of each of the phases (Nb, Nb5Si3) was determined using the Electron BackScattering Pattern (EBSP) technique for electron diffraction in the scanning electron microscope. A system employing automatic diffraction pattern recognition, crystallographic analysis, and sample or beam scanning was used to acquire the microtexture data.
Structure determination of a new metastable Au-Sn phase using convergent beam electron diffraction
Authors: Sleight M.E. , Midgley P.A. , Vincent R. 
Published: June 2020

Reports of a new metastable Au-Sn phase led to the investigation of this system by Convergent Beam Electron Diffraction (CBED). A novel growth route was used, in which a single metallic layer of Sn was evaporated onto rock salt and allowed to form a thin oxide layer, before a film of gold was evaporated directly on top. Subsequent in-situ heating in a TEM supplied enough energy to allow solid state diffusion of Sn through the oxide to react with the Au, forming a number of intermetallic phases.A new tetragonal AuSru phase was found, space group P4/nbm and lattice parameters a=6.63Å, c=5.92Å, and it was proposed that this new phase was isostructural with PtPb4 . Further work described here confinns this structure type and shows how the atomic positions were refined using First Order Laue Zone (FOLZ) reflections within a quasi-kinematic approximation.Fig. 1 shows a section of the FOLZ at the [001] zone axis of this new Au-Sn phase.
Electron diffraction analysis of a metastable state in ion-irradiated MgAl2O4 spinel
Authors: Devanathan Ram , Yu Ning , Sickafus Kurt E. , Nastasi Michael 
Published: June 2020

Magnesium aluminate spinel is considered to be a remarkably radiation resistant material. Single crystal spinel exhibits very little damage when irradiated with fast neutrons or energetic ions. Recently, amorphization of single-crystal MgAl204 was observed, for the first time, following irradiation with 400 keV Xe2+ at about 100 K to a peak dose of 25 dpa. Electron diffraction patterns from spinel subjected to different doses show the extinction of first-order fundamental reflections prior to the occurence of amorphization. This suggests that, enroute to becoming amorphous, ion-irradiated spinel transforms to a metastable crystalline state with a lattice constant that is half that of spinel. In an effort to understand this phase transformation, we have analyzed the structure of the metastable state using electron diffraction.Spinel belongs to the spacegroup Fd3m (fee Bravais lattice). The unit cell has a lattice constant of about 0.8 nm and is made of two sets of four octants.
Morphological transformations in solution-cast Styrene-Butadiene-Styrene (SBS) triblock copolymer thin films
Authors: Kim Ginam , Marsillo W. , Libera M. 
Published: June 2020

The fact that block copolymers can assume a range of morphologies depending upon such variables as relative block length and molecular weight is now well known. In the case of poly(styrene)[PS]-poly(butadiene)[PB]-poly(styrene) (SBS) triblock copolymer, the morphologies range from spheres (roughly ~20% minor component), to cylinders (roughly 20%~35% minor component), to lamellae (roughly equal component fractions) Most recently, there has been increasing interest in transformations between morphologies by thermal annealing. This paper describes initial results studying the effect of solvent evaporation rate and post-casting annealing treatment on the morphology of SBS thin films.TEM specimens were prepared by solution casting electron transparent films. 50 μl of 0.1 wt% SBS (30% styrene, Mw=14,000, Scientific Polymer Products, Inc.) dissolved in toluene was deposited on a polished NaCl single crystal substrate placed in a small dish. After solvent evaporation the film was cut into small squares, floated from the salt in water, and each square was collected on a Cu grid.
The influence of nitrogen on the stability of nanophase molybdenum disilicide
Authors: Kung H. , Jervis T. R. , Hirvonen J-P , Mitchell T. E. , Nastasi M. 
Published: June 2020

The intermetallic compound, MoSi2, has a combination of interesting properties, ranging from a high melting point to superior high temperature oxidation and corrosion resistance, which makes it a potential candidate for high temperature structural applications. It was shown previously that the addition of nitrogen into MoSi2 forms MoSi2Nx (x:3-4). The new phase has a very high crystallization temperature (> 1000°C) and is thermally compatible with both Mo and MoSi2. As suggested by these results, the introduction of nitrogen into MoSi2 may cause significant changes in its properties, yet the role of nitrogen in influencing the structure and phase stability of MoSi2 is still not known. In this study, we have systematically investigated the evolution of structure in MoSi2 in the presence of different nitrogen contents and annealing conditions.The system investigated is single phase MoSi2Nx. Films were prepared by sputter deposition using a planar magnetron MoSi2 target at a DC power of 100-200 W.
Investigation of irradiation-induced nucleation processes in silicon and germanium
Authors: Atwater Harry A. , Yang C.M. , Shcheglov K.V. 
Published: June 2020

Studies of the initial stages of nucleation of silicon and germanium have yielded insights that point the way to achievement of engineering control over crystal size evolution at the nanometer scale. In addition to their importance in understanding fundamental issues in nucleation, these studies are relevant to efforts to (i) control the size distributions of silicon and germanium “quantum dots𠇍, which will in turn enable control of the optical properties of these materials, (ii) and control the kinetics of crystallization of amorphous silicon and germanium films on amorphous insulating substrates so as to, e.g., produce crystalline grains of essentially arbitrary size.Ge quantum dot nanocrystals with average sizes between 2 nm and 9 nm were formed by room temperature ion implantation into SiO2, followed by precipitation during thermal anneals at temperatures between 30°C and 1200°C[1]. Surprisingly, it was found that Ge nanocrystal nucleation occurs at room temperature as shown in Fig. 1, and that subsequent microstructural evolution occurred via coarsening of the initial distribution.
Energy-filtered imaging of interfacial composition in complex Ni-base superalloys
Authors: Hall E. L. , Bentley J. 
Published: June 2020

In a wide variety of important engineering materials, including structural Ni, Fe, and Al-base alloys, the study of compositional gradients that occur at grain boundaries and other interfaces due to the precipitation of solute-rich second phases is of critical importance. X-ray spectrometry in the analytical electron microscope (AEM) has been used for many years to study solute depletion at interfaces in these alloys. It has been particularly effective at providing accurate, quantitative measurements in cases where the interface precipitates are spaced far apart and where relatively wide compositional gradients result from diffusion-controlled “collector-plate” mechanisms. However, in complex alloys, with heavy grain boundary coverage, multiple precipitate types, and/or multiphase matrices, x-ray microanalysis is more limited due to beam spreading and die associated 5-20nm spatial resolution achieved in these alloys with AEMs equipped with thermionic sources.Elemental mapping in an AEM equipped with an imaging energy-filter is an alternative method for the study of interface compositional gradients. It has been shown to be effective for this purpose in relatively simple situations in steels.
Delocalization effect in energy-filtered electron images of surfaces and interfaces
Authors: Wang Z. L. , Shapiro A.J. 
Published: June 2020

Accurate structure determination is feasible using zero energy-loss images, since image simulations can be done accurately based on elastic scattering theory [1]. Two factors can be assessed from the energy-filtered images: one is the contribution of inelastically scattered electrons to HREM images; and two is the effect of absorption by inelastic scattering on images obtained using 0-loss electrons. In this paper, MgO(l00) surface and Al/Ti interface are used to demonstrate the delocalization effect of valence-excitation in energy-filtered surface and interface images, respectively.Figure 1 shows a pair of MgO lattice images recorded using all the transmitted (Figure la) and just the elastically transmitted (Figure lb) electrons, respectively. The MgO cube is oriented along [110], so that the contrast variation as a continuous function of the specimen thickness is revealed by a single image. When the specimen is thinner than about 20 nm, no significant differences are seen between the filtered and unfiltered images.
Quantitative high spatial resolution microchemical analysis of Fe-Co-Ni transformational-toughened steels
Authors: Lippard H.E. , Dravid V.P. , Olson G.B. 
Published: June 2020

Superior strength-toughness combinations can be obtained in Aermet 100 by an austenite→martensite phase transformation of small intralath austenite precipitates. The enhanced toughness in these alloys has been attributed to the presence of “metastable” austenite precipitates, the stability of which is intimately related to the size and composition. The austenite precipitates require high stability to resist transformation under all stress conditions except when in the triaxial stress field of a crack tip. The two primary factors determining austenite stability are size and composition. Thus the microstructureproperty correlations and further alloy development require quantitative microchemical analysis of the 50-150Å austenite precipitates.Of the two obvious analytical electron microscopy techniques, energy dispersive spectrometry (EDS) is superior for quantitative results. Several artifacts must be considered when performing quantitative EDS, for example; the continuum background, absorption/fluorescence effects, k-factor measurement and peak overlap. The continuum background fitting is elementary due to the high peak/background ratio and extensive research in this area.
Electron optical design of an EFTEM concerning optimum selection of imaging parameters for different sizes of detection systems
Authors: Benner G. , Probst W. , Rilk R. 
Published: June 2020

The amount of information which can be gained about an object is considerably improved by the incorporation of an imaging energy filter in a TEM. Besides the conventional modes of operation elastic brightfield (EBF) and darkfield (EDF) imaging or diffraction are provided by an Energy Filtering Transmission Electron Microscope (EFTEM) as well as Electron Spectroscopic Imaging (ESI) or Electron Energy Loss Spectroscopy (EELS). Thus, the demands for carefully designed highly flexible electron optics are much more sophisticated as compared to a CTEM.One of the most important parameters for elastic imaging and ESI is the width of the energy window, which can be selected by a slit aperture of adjustable width according to the particular needs. This energy window defines the size of the transferable specimen area or diffraction pattern, respectively, as well as the acceptance angle of the spectrometer. In order to meet the optimum parameters concerning the energy window and the size of the detection system (e.g. photographic plate, image plate, Slow Scan CCD camera (SSCCD), TV camera, electron detector, etc.) the magnifications of the pre- and of the post-spectrometer projector lens systems has to be independently adjustable.
Point-defect distributions in ceramics by spectrum-line profiling
Authors: Bruley John , Williams David B. , Tseng Ming-Wei 
Published: June 2020

Electron energy-loss spectroscopy is well suited to the study of interfaces because the ionization edges can be used to identify the atomic species present and the near edge fine structures on the edges reveal information on the electronic structure surrounding these atoms. This information can be extracted from regions of sample approaching atomic dimensions. A challenge is to be able to map and interpret spectral features with a level of confidence that will allow explanations of physical properties of interest.The term Spectrum-Line is used here to refer to a linear array of spectra, recorded sequentially along a line traced out by the electron probe and is the 1 dimensional analog of the Spectrum-Image. Processing Spectrum-Lines to generate quantitative profiles can provide a vivid picture of changes in composition, a valence state, or site occupancy across an interface. To aid interpretation and guide further spectrum analysis the near-edge fine structures can be compared to spectra from compounds whose atomic coordinations are well known or modeled using the results of band-structure or molecular orbital calculations of electronic structures.
Quantitative analysis of hole density and lattice parameter at grain boundaries in YBa2Cu3O7-δ
Authors: Zhu Yimei , Zuo J.M. 
Published: June 2020

One challenge for high Tc superconductor research is to overcome the low intergranular transport currents which hinder practical applications. Evidence shows that lattice mismatch at the boundaries contributes to the depletion in charge carriers (holes), while the strain fields surrounding the cores of boundary dislocations suppress the superconducting order parameter. Using high-spatial resolution EDX, EELS and CBED techniques with a 20 Å field emission probe, we studied cation segregation, variations in oxygen/hole content, and lattice parameters at and across grain boundaries for various Σ and near-Σ boundaries in bulk YBa2Cu3O7-δ. The geometry of those arbitrary grain boundaries was modeled using the constrained Coincidence Site Lattice (cCSL) theory, which requires c2/a2 being rational for coincidence boundaries in non-cubic crystals.In this presentation, we report our quantitative and simultaneous measurements of oxygen/hole content (Fig.l) and of lattice parameters (Fig.3) at the boundary regions. The oxygen/hole density was quantified by guassian fitting to the observed oxygen K-edge spectra (Fig.2) and comparing them with those from the same batch which had undergone oxygen reduction process (oxygen content was determined by thermal gravimetric analysis and mass-measurement techniques).
A CVI-processing marker study
Authors: Freeman G. B. , Lackey W. J. , Vaidyaraman S. 
Published: June 2020

Fiber reinforced ceramic composites greatly extend the region of application for ceramic materials because the inclusion of a second phase such as fibers helps to prevent catastrophic failure via the mechanisms of crack branching, deflection, bridging and fiber pull-out. While ceramic composites are excellent candidate materials for high temperature structural applications, many conventional manufacturing processes damage the fibers during fabrication and thereby reduce the strength and toughness from what is theoretically possible. Chemical vapor infiltration (CVI) is an effective and versatile technique for fabrication of ceramic matrix composites which promises to reduce fiber degradation.While CVI is no longer a truly novel processing technique, it is still difficult to predict the best set of operating conditions for what can be a tedious process. Conventional CVI methods may take up to a week to fully infiltrate a small part and even state-of-theart forced flow-thermal gradient CVI (FCVI) processing takes the better part of a day. It is, more over, difficult to monitor the evolution of deposition within a, for example, woven preform.
Identification of the intermediate phase Bi4Sr4Ca3Cu5O18+δ during Bi/2212 and Bi/2223 conversion
Authors: Bian Weimin , Zhu Yimei , Wang Y.L. , Gillette D. , Suenaga M. 
Published: June 2020

Among all the high-temperature superconductors, Bi/2223 is the most promising material as tapes and wires for large-scale and high-current applications. However, synthesizing Bi/2223 as a single phase is extremely difficult because of its relatively poor thermal stability and the narrow ranges of stoichiometry and temperature for its formation. Recently, to understand the formation mechanism and establish the optimum heat treatment conditions for the growth of Bi/2223, we have systematically studied phase transformation of the Bi-based superconductors. In this article, we report our finding of the intermediate phase of Bi4Sr4Ca3Cu5O18+δ (Bi/4435).Bi/2212 tapes with a Bi/2223 composition, produced by the standard “oxide powder in tube” process, were used in the study. TEM cross-section specimens were prepared from the bulk samples that were quenched or furnace-cooled from different stages during the Bi/2212 and Bi/2223 conversion.Figure 1 shows a lattice image of the Bi/4435 phase with an alternating narrowly and widely spaced lattice (each black line corresponds to the position of the BiO layer).
Composition-size distribution diagrams for alloy catalysts
Authors: Lyman C. E. , Lakis R. E. , Stenger H. G. 
Published: June 2020

Catalyst microstructure and catalytic properties can be directly correlated using a composition-size distribution diagram that maps the phases of small alloy particles by composition and size. The application of this diagram given here concerns Pt-Rh/alumina catalysts for reduction of NO in hydrogen at low temperatures. The composition-size diagram provides an understanding of why some alloy catalysts perform worse than pure Pt in the NO reduction reaction, while other preparations exhibit the several times the activity of pure Pt. The composition-size diagram can be used to "fingerprint" active and less active alloy catalysts. Analytical electron microscopy (AEM) has been used to determine the Pt-Rh particle composition-size distribution.Catalysts were prepared by aqueous impregnation of platinum chloride into gamma-alumina particles with a 4 nm average pore size. After impregnation and air drying, the catalyst was calcined in air at 500°C for 3 hr. Subsequently, rhodium was impregnated from its chloride into the same support material, and the preparation was air-dried.