bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of X-Ray Microanalysis to Characterize Liver Necrosis of Mice, Rats, And Guinea-Pig
Authors: Augsten Kurt , Güttner Jürgen
Published: June 2020

On the basis of ultrastructural findings several types of cell death have been distinguished, which characterize different pathological mechanisms of death. Necrosis refers to the progressive degradation of cell structure after death caused by different toxins. Apoptosis is characterized morphologically by shrinking and budding of a cell and by the appearance of discrete apoptic bodies which varied considerably in size. The aim of this work was by means of x-ray microanalysis to characterize different liver necrosis of well-known and unknown aetiology.

Liver necrosis of mice that had been suffered from Tyzzer’s disease, mouse hepatitis virus infection and infectious ectromelia as well as necrosis of unknown origin of guinea-pigs were investigated. Rats receiving CCl4 (p. o.) were used as reference. The liver was processed for routine histology by fixation in 4 % neutralized formalin for two days and embedded in paraffin; subsequently following serial sections, 4-5 um thick, were mounted on glass slides and Al-foil or C-discs.
Low-Energy Electron Induced X-Ray Spectroscopy (LEEIXS), An Emerging Technique in Surface and Thin-Film Analysis. New Developments and Applications
Authors: Charbonnier M. , Romand M. , Gaillard F.
Published: June 2020

Within the last two decades analysis and characterization of surfaces, interfaces and very thin films have become of considerable importance in many fields of modern technology. This increasing demand has lead to a rapid development of various surface and near-surface analytical techniques. Some of these methods such as XPS, AES, SIMS and ISS have matured both with respect to instrumentation and methodology and therefore are now sufficiently well-established. Others are yet in their infancy but possess a large potential and this is the case of low-energy electron induced x-ray spectrometry (LEEIXS) discussed hereafter.

The instrument is a wavelength-dispersive x-ray spectrometer in which the conventional x-ray tube has been replaced by an electronically stabilized gas-discharge source. Such a system operates as an electron source under the primary vacuum of the spectrometer (≃ 10−1 torr). Typical operating conditions are in the range 0.5-5 kV with a current of 0.1-0.5 mA and the diameter of the electron beam at the sample surface is less than 1 cm2.
A Study on the Occurrence of Gold in Unoxidized Carlin-Type Ores in China Using AEM, SEM-EDX and SXRF
Authors: Yongkang Liu , Shirong Liu , Guangquan Wan , Lindi Zhou , Jilian Li , Fangqiong Lu
Published: June 2020

The knowledge about the occurrence of gold is essential both to the explanation for the genesis of gold mineralization in its deposits and to the evaluation and exploration or even smelt process of its ores. It has been well known that the gold occurrence in the Carlin-type ores still remains a difficult question to be answered because of the tiny scale of its locality and its very low content.

This paper reports the results of our analysis on some gold bearing minerals in the Carlin-type ores discovered during recent years in China with combined use of analytical electron microscopy (AEM), scanning electron microscopy-energy dispersive X ray spectrometry (SEM-EDX) and synchrotron X ray flourescence analysis (SXRF) techniques as following:

(1) Some gold occurred as submicron size grains in the ores (see Photo 1-4 and Figure 1-3) with grain size generally less than 0.2 micron.

(2) It has been found by AEM and SEM-EDX observation and SXRF analysis that gold occurred as micrograins embedded in the boundaries of clay or quartz minerals rather than, as said, entered the lattice or adhered as a covering film to the surface of clay minerals (see Figure 4).
Quantitative Microanalysis of ZrO2/Non-Oxide Ceramic Composites
Authors: Miller P.R. , Hannink R.H.J. , Muddle B.C.
Published: June 2020

Addition of zirconia (ZrO2) to oxide and non-ox1de ceramics improves consolidation behaviour, strength and toughness of fabricated bodies. Such materials are generally referred to as zirconia-toughened ceramics, ZTC. Typical examples of such systems include oxide matrices such as α- and β"-Al2O3, MgO.Al2O3 (spinel), ZrSiO4 (zircon) and ZnO; non-oxide systems include Sic, Si3N4, TiN, TiCN and TiB2. In these materials an Improved toughness is anticipated as a result of the stress-activated tetragonal to monoclinic transformation in the dispersed ZrO2. In an effort to understand the consolidation mechanisms and microstructural features leading to the improved strength and toughness of ZrO2-TiX (X=C,N,B2) based composites, a systematic study has been made of the composition of the component phases using energy dispersive x-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS).

The experiments were conducted on two types of samples. Firstly, to establish the kTizr factors for EDXS analysis and to assess the detectability limits of the EELS technique, a series of TiO2-ZrO2 solid-solution standards containing 2.5-13 mole% TiO2 were prepared.
Leached Nuclear Waste Glasses: Ultramicrotomy and AEM Characterization
Authors: Bradley J.P. , Bates J.K.
Published: June 2020

The long term performance of a nuclear waste repository depends ultimately on the stability of the waste form. Borosilicate glasses have been proposed as a waste form because they can incorporate radionuclides into their structures and they are relatively resistant to corrosion in an aqueous environment. Experimental and computer modeling programs are in progress to evaluate their long term stability in a geological repository. In the experimental program, glasses have been reacted in sealed vessels (for between 7 and 280 days) to simulate the effects of terrestrial aqueous alteration (leaching). During leaching, a layer of secondary phases (predominantly layer silicates) builds up on the glass surfaces (Pigs. 1-3). Determination of the mineralogy of the leached layer is critical for evaluation of glass performance, but the layers are typically ultra-thin (1-50 μm), poorly crystallized, friable coatings that have eluded detailed characterization. Using ultramicrotomy, we have successfully prepared electron transparent thin-sections of the glasses plus leached layers with minimal disturbance of their indigenous microstructures (Figs. 2-4).
Phase Identification in Graphite Fibre-Aluminum Composites Using AEM
Authors: Carpenter G.J.C. , Lo S.H.
Published: June 2020

The unique properties of graphite fibre - aluminum (Gr/Al) composites (high specific strength, high modulus and low coefficient of thermal expansion) have resulted in their use for components in space structures. However, the exposure to high temperatures required for the production of bulk material can result in interfacial reactions that cause a degradation in mechanical properties. Analytical electron microscopy (AEM) has been used to examine the phases formed during the heat treatment of such materials. The Gr/Al composite was examined in two forms: (a) as wire tows made up of AA6061 Al alloy, reinforced with Arco pitch-based P100 graphite fibres, coated with a thin layer of TiBx, and (b) as bulk composites produced by hot pressing a bundle of tows within a cladding of AA6061. Specimens for TEM were produced in longitudinal and cross-sectional orientations by preparing discs in a dimple-grinder, followed by ion-beam thinning. The specimens were examined in a Philips EM400T microscope, fitted with an Edax 9100 EDX system and a Gatan EELS.
Chemical Analysis of Layered Structures by Digital X-ray and EELS Mapping on an HB501 STEM
Authors: Long N.J. , Petford-Long A.K.
Published: June 2020

The development of materials formed from multilayer structures (MLS), with compositional modulation on the nanometre scale, such as semiconductor multiple quantum-well structures (MQW), used as lasers in fibre-optic communications, and metallic MLS such as Co/Cr and Co/W, for use as perpendicular magnetic recording media has led to a need for high spatial resolution chemical analysis techniques. The properties of such materials depends critically on the composition profile across the layers and interfaces. Techniques which can be applied to analysis of MLF in cross-section are energy dispersive X-ray (EDS) or electron energy loss (EELS) analysis using a small probe scanning transmission electron microscope (STEM).

A VG HB501 STEM at Oxford, fitted with a windowless EDS detector and an EELS detector has been modified to enable pulse counted digital X-ray and EELS maps (plus bright-field (BF) or annular dark-field (ADF) images) to be collected and stored for post-processing in the Semper image-processing package.
Application of ALCHEMI to the study of non-Stoichiometric Compounds
Authors: Munroe P.R. , Baker I.
Published: June 2020

ALCHEMI, or atom location by channeling enhanced microanalysis, has been used to study the sublattice occupancy of trace elements in minerals and ternary additions to intermetallic compounds. ALCHEMI studies of intermetallic compounds have previously been performed on compounds which are at, or near to, stoichiometry, or where the ternary element has been added at the expense of one species. In these cases it is assumed that the sublattices are perfect. That is, in the compound AB + X, there are no A atoms on the B sublattice or vice versa.

In compounds which are far from stoichiometry, which may include ternary additions, there may be A atoms on the B sublattice. For example in Ni-45Al (compositions given in atomic %) , 10% of the aluminum sublattice sites are occupied by nickel atoms; iron-rich FeAl alloys behave similarly. Thus if a nickel-rich NiAl thin foil is tilted to an orientation where the x-ray intensity of the aluminum sublattice is enhanced, there will be a concomitant enhancement of the nickel x-ray intensity due to the nickel atoms located on the aluminum sublattice.
A CBED Study of CuAgSS
Authors: Baker C.L. , Lincoln F.J. , Johnson A.W.S.
Published: June 2020

The room temperature phase of the compound CuAgS occurs in nature as the mineral stromeyerite. Its structure is stable up to approximately 90°C, above this temperature it transforms to a cation disordered structure with copper and silver ions mobile through a hexagonal close packed sulphur lattice. The structure of stromeyerite has been investigated by single crystal X-ray diffraction and was found to have an orthorhombic unit cell with possible space groups Cmcm (63) or Cmc21 (36). The structure was refined in Cmcm but only to an R factor of 0.30. Refinement in Cmc21 was not attempted. The structure is important as a starting model for those of other phases in the system Cu-Ag-S and consequently more precise information was required.

Synthetic CuAgS was prepared from the binary sulphides by solid state reaction in vacuo at 300°C for one week. It was then ground to a powder and annealed at 70°C in N2 for a month.
Characterization of Crystalline Defects Using CBED Techniques
Authors: Pérez R.
Published: June 2020

Convergent beam electron diffraction (CBED) is a technique widely used for obtaining crystallographic information from a small region in a specimen. In recent years CBED technique have been mainly used for the symmetry characterization of perfect crystals. However, the study of crystals containing defects by CBED have received little attention in the literature1-4. The results presented in this communication explore some of the image contrast characteristics obtained in theoretical simulations of zero-order laue zone (ZOLZ) reflections. These calculations have been carried out for crystalline specimens wich contain dislocations or stacking faults. The theoretical simulations are based on the multibeam form of the dynamical theory using ato mic scattering factors reported by Doyle and Turner5. The Fourier coefficients of the lattice pottential were Debye-Waller corrected in all cases. Some of the most important parameters which have strong influence on image contrast have been explored. These include, the thickness of the specimen, the depth of defect in the specimen, the multibeam effects, the nature of the defects etc.
Critical Voltage for Non-Centro. Crystals and its Application to the Accurate Measurement of Structure Factor Phases by CBED
Authors: Spence J.C.H. , Zuo J.M.
Published: June 2020

The application of the three-beam dynamical theory of transmission electron diffraction to centrosymmetric and non-centrosymmetric crystals shows that certain regions of three-beam CBED patterns are highly sensitive to the three-phase structure invariant By applying this method to the systematics geometry, a method has been described which allows structure factor phases to be measured with an accuracy of 0.07°. Using the Bethe potentials, we find a degeneracy in eigenvalues at the critical voltage VA for acentric crystals in the systematics orientation where

Here VA is now seen to depend both on the structure factors Vg (in volts) and on the systematics “two=phase” invariant In this paper we consider the application of this method to BeO (wurtzite structure), with g = (004) and h = (002). Then the CBED intensity is most sensitive to Y near the (004) Bragg condition at 46 kV. But since the theory contains only the product KSg, other voltages and orientations are also sensitive.
Characterization of Occurrence and Distribution of Invisible Gold in Ore by EPMA
Authors: Mao Shuihe
Published: June 2020

Owing to the invisibility of ultramicron gold (invisible gold) in “Carl in type” gold ore, it is extremely difficult to investigate its occurrence and distribution by conventional determinative means.EPMA has been proved to be very powerful instrument for doing research on this subject because it has advantages of high space resolution, nondestructive,getting quantitative analysis results and observing various kinds of images continuously with same equipment etc.

The unoxidized ore sample is selected from drill cuttings at a “Carlin type” gold mine in Southwest China with gold tenor of 31.02 g/t and weighs 2438g. The operating conditions of EPMA are: accelerating voltage 25kV, beam current 1×l0-8 A, beam diameter about 1 μm. AuLα but not AuMα is preferably chosen as analysed x-ray line, because AuMα 1 (5.840Å) is overlapping with the 3rd order line of FeKα (5.812Å) to some extent and iron is the main component of pyrite matrix. According to the expression of detection limit(CDL ), the calculated value of CDL under the circumstances is 0.038%.
CCD Quantum Efficiency at the Theoretical Limit with Molecular Beam Epitaxy
Authors: Nikzad Shouleh , Hoenk M.E. , Grunthaner P.J. , Grunthaner F.J.
Published: June 2020

A variety of biological, medical, astronomical and materials science measurements require real-time imaging of phenomena which produce low light levels. Charge-coupled devices (CCDs), which have high resolution and linear response over a large dynamic range, are often used as imaging sensors in conjunction with image intensifiers or phosphors to improve the signal-to-noise at low light levels, particularly in the blue and UV regions of the spectrum. Conventional CCDs typically have quantum efficiency (QE) as low as ~10% in the range of 300-500 nm. This region of the spectrum is very important in biological experiments which require detecting the fluorescence of dyes, in astronomical observations of spectral lines in the blue and near UV, and in a variety of applications which use image intensifiers to amplify the signal. Improvement of CCD quantum efficiency with respect to the conventional technology is critical for most of these experiments. The detection of blue and UV photons in a silicon CCD is challenging due to the short absorption length of these photons in silicon (e.g., 4 nm absorption length at 270 nm) and the existence of a backside potential well (caused by positive charge at the interface of Si and SiO2).
Real-time observation of single molecules by confocal fluorescence microscopy
Authors: Nie Shuming , Chiu Daniel T. , Zare Richard N.
Published: June 2020

The ability to detect, identify, and manipulate individual molecules offer exciting possibilities in many fields, including chemical analysis, materials research, and the biological sciences. A particularly powerful approach is to combine the exquisite sensitivity of laser-induced fluorescence and the spatial localization and imaging capabilities of diffraction-limited or near-field optical microscopes. Unlike scanning tunneling microscopy (STM) and atomic force microscopy (AFM), which lack molecular specificity, optical spectroscopy and microscopy techniques can be used for real-time monitoring and molecular identification at nanometer dimensions or in ultrasmall volumes.

We report the use of confocal fluorescence microscopy coupled with a diffraction-limit laser beam and a high-efficiency photodiode for real-time detection of single fluorescent molecules in solution at room temperature. Rigler and Eigen have also demonstrated single-molecule detection with a confocal microscope and fluorescence correlation spectroscopy. The probe (or sampling) volume is effectively an elongated cylinder, with its radius being determined by optical diffraction and length by spherical aberration.
SNR gains with superconducting coils and hyperpolarized inert gas
Authors: Black R. D.
Published: June 2020

Magnetic resonance microscopy (MRM) has advanced from a technical challenge to a practical tool in a wide range of basic sciences (1). The nondestructive nature of the technique allows for repeated studies of the same sample, retrospective studies through any arbitrary plane, registered studies using different contrast mechanisms, and examination of valuable specimens. "Proton contrast" is provided by making use of T1, T2, T1ρ , diffusion, and magnetization contrast weightings, thus permitting direct examination of the state of water in tissues; something not possible with other microscopic techniques. The technical hurdles imposed by a limited signal-to-noise ratio (SNR) have been partially overcome by improved RF coil design and by three dimensional Fourier transform encoding for large arrays. We have introduced two additional technologies that help to further redress this SNR deficit: superconducting RF coils and inert gas hyperpolarization.

It has been argued elsewhere (2,3) that the dominant source of noise in the receiving chain for small objects in high fields is the pickup coil and the preamplifier.
NMR microscopy studies of tumor microenvironments
Authors: Neeman Michal , Schiffenbauer Yael S. , Abramovitch Rinat , Meir Gila
Published: June 2020

The microenvironmental heterogeneity, characteristic of solid tumors 500 üm in diameter or larger, arises from insufficient nutrient supply due to tumor growth exceeding the rate of vascularization. Multicellular spheroids were proposed as an in vitro experimental model system for simulating these stress environments. As in hypoxic regions of tumors, inner cell layers in spheroids show resistance to radiation and conventional chemotherapy, as well as enhanced expression of the angiogenic vascular endothelial growth factor (VEGF). We have applied NMR microscopy for the study of the effects of these microenvironments on tumor physiology.

NMR microscopy experiments were developed for mapping gradients in water diffusion and metabolite content across intact, perfused spheroids (1 mm in diameter). These methods were tested in a study of the cytotoxic effects of cyclocreatine, a synthetic analogue of creatine. In contrast with most of the common anti cancer drugs, accumulation of cyclocreatine was observed across the entire viable rim of C6 glioma spheroids.
Study of crystalline interfaces using Δ-G approach
Authors: Zhang W.-Z.
Published: June 2020

The study of interfacial structure is a fundamental step to achieve the beneficial structure/property relationship in materials. A knowledge of phase boundaries may provide useful insights for a better understanding of the phase transformation. The O-lattice theory, containing the coincidence site lattice (CSL) model as a subset, has been widely applied and shown to account for boundaries of preferred orientation. Examples include low-Σ CSL grain boundaries with high-Γ (Σ=the ratio between the volumes of unit cells of CSL and the crystal lattice; Γ=the planar density of CSL points), and facets or habit plane of interfaces of precipitates.36 The indices of the crystals adjoining the boundary are commonly used to define the boundary plane. These indices do not reveal a direct connection between the O-lattice planes and the boundaries.

This paper emphasizes the application of a simple parameter, Δg, for the study of interfaces and its relationship with the O-lattice planes.
Preparation and characterization of thin films of carbon nitride
Authors: Wan L. , Egerton R. F.
Published: June 2020

INTRODUCTIONRecently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNXfilms deposited by two different methods.

SPECIMEN PREPARATIONSpecimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.
What is the ultimate precision of CBED structure factor measurement? Application to Group IV and III-V semiconductors
Authors: Saunders M. , Midgley P.A. , Vincent R.
Published: June 2020

We have previously demonstrated the feasibility of fitting calculated zone-axis Convergent Beam Electron Diffraction (CBED) patterns to zero-loss energy-filtered experimental data. The aim of this pattern matching procedure is to refine accurate low-order structure factors that can be used to reconstruct the bonding charge density. Initial tests on silicon [110] zone-axis patterns have shown that this new electron diffraction technique is capable of accuracies comparable with existing X-ray methods and that the results are in good agreement with solid state theory calculations. The general applicability of the CBED pattern matching technique is now investigated by studying the bond charge of two other Group IV materials, i.e. germanium and diamond, and the HI-V semiconductor GaAs.

The (110) plane of the reconstructed bond charge density for each of the Group IV materials is shown in Figure 1. The agreement between these results and those predicted by solid state theory is excellent despite the use of only five independent Fourier components in the reconstruction.
Plate and needle-like crystal structure determination by combining electron and synchrotron diffraction
Authors: Li Z. G. , Harlow R. L. , Gardner K. H. , Liang L. , Dorset D. L. , Zou J. M.
Published: June 2020

In recent years, significant progress in determining light-element crystal structures using electron diffraction has been made to meet the increasing needs from the material science community. The set of techniques for carrying out electron crystallography, including sample preparation, data collection and recording, diffraction micrograph digitization, and confirmation by direct phasing methods and structure refinements, have being developed. However, only a very limited number of structures have been determinated by electron crystallography because of a number of severe problems and difficulties. Meanwhile, the progress in determining crystal structures using x-ray diffraction has been rapidly increasing, particularly because of the more extensive use of powerful synchrotron diffraction techniques. In this case, the minimum crystal size required for a single-crystal study has decreased from 100 microns to about 10 microns. Even so, many new materials can only be obtained in microcrystalline form with crystallite sizes well below one micron. In this submicron regime, ab initio structure solutions from synchrotron powder-diffraction patterns have proven to be quite powerful.
Energy filtered diffraction contrast defect imaging using a field emission TEM
Authors: Wiezorek J.M.K. , Swaminathan S. , Fraser H.L.
Published: June 2020

The dynamical theory of electron diffraction describes most of the effects observed in diffraction contrast defect images very well. However, quantitative discrepancies between appropriately simulated and experimental defect image contrast have been reported and have generally been attributed to the inadequate theoretical treatment of absorption. Thus, it is expected that the comparison of energy filtered defect images with many-beam dynamical simulations will facilitate a quantitative study of the contributions from inelastically scattered electrons to the image. Presently, two commercially available instruments allow the acquisition of energy-filtered imaging data in TEM: (1) the Zeiss EM912 Omega equipped with an in-column filter and (2) a post-column system, the Gatan Imaging PEELS (GIF) which, in principle, can be added to any TEM. At the Ohio State University (OSU) the GIF has been attached to a Philips CM200 FEG TEM and this paper will report on some preliminary experimental results of diffraction contrast imaging of stacking fault (SF) pyramids in <001>-Si, which have been chosen because they have been well characterized in the past.
Automation in electron diffraction analysis
Authors: Zuo J. M.
Published: June 2020

Automated lattice parameter measurement and orientation analysis are often needed in the characterization of microstructures using electron diffraction, and is made possible with increasingly popular use of slow scan CCD camera and imaging plates. Both of these two detectors are largely linear and digital. Typical electron diffraction analysis has three steps: 1) diffraction pattern measurement, 2) diffraction pattern indexing and 3) solution. Full automation in all these three steps is desired, however, may be hard to achieve especially for complex crystal structures. The importance of automation in each of these steps depends on the type of analysis and the number of analysis needed. Full automation is necessary in the type of applications where the same analysis is repeated many times, such as in texture analysis. In table 1, various applications of electron diffraction and automation needed are listed.

There are two types of approach to the automatic indexing. The commonly used method is to matching a calculated list of g's with the measured ones.
Energy-filtered high-resolution Electron Microscopy of nanostructured materials
Authors: Wang Z. L.
Published: June 2020

The interaction between an incident electron and the atoms in condensed matter results in various inelastic scattering processes. Thermal diffuse scattering or phonon scattering is the result of atomic vibrations in crystals. This process does not introduce any significant energy-loss (< 0.1 eV) but produces large momentum transfer. Valence-loss (or plasmon for metals and semiconductors) excitation, which characterizes the transitions of electrons from the valence band to the conduction band, involves an energyloss in the range of 1 -50 e V. Atomic inner-shell ionization is excited by the energy transfer of the incident electron, resulting in an ejected electron from the deep-core states. Continuous energy-loss spectra can also be generated by an electron which penetrates into the specimen and undergoes collisions with the atoms in it, resulting in Bremsstrahlung and leading to emission of x-rays with continuous energy. The electron Compton scattering refers to the collision of the incident electron with an electron belonging to the specimen. In an electron energy-loss spectrum (EELS), the zero-loss peak is composed of elastically and thermal diffusely scattered electrons. The low-loss region is dominated by valence-excitations.
Recent developments in scanning ion conductance microscopy
Authors: Proksch Roger , Lai Ratnesh , Hansma Paul K.
Published: June 2020

Scanning probe microscopes sensitive to two or more localized physical or chemical interactions are finding increased application in science and technology. These microscopes usually measure surface topography and another property such as electric field, magnetic field or optical propeties such as fluorescence. These simultaneously imaged properties can be correlated to provide a multimodal perspective of the sample. In order to measure ion transport through membranes and surface topography, we have developed a combination Scanning Ion Conductance Microscope (SICM) and Atomic Force Microscope (ARM). A schematic diagram of this microscope is shown in Figure 1. The SICM/AFM uses a flexible micropipette which has been pulled to a very small diameter (c.a. 50-100 nm). The end of the pipette is bent at 90° and a small gold covered piece of mica is glued to the top of the bend allowing it to function as a cantilever for AFM. The pipette is filled with an electrolyte and an Ag/AgCl electrode is inserted, allowing it to serve as a conductance probe.
Analysis of Nanometer Sized Pyrogenic Particles by Scanning Transmission Electron Microscopy
Authors: Wallis DJ , Browning ND , Megaridis CM
Published: June 2020

Iron is a ubiquitous element on the earth's surface, and is thus involved in most naturally occurring fires. Iron organometalic compounds have also been known to suppress carbonaceous soot emissions under certain operating conditions of practical combustors. In order to unravel the physical and chemical mechanisms of influence, of iron on the emission of carbonaceous pyrogenic particles, finescale characterization techniques need to be implemented.

The combined techniques of Z-contrast imaging and electron energy loss spectroscopy (EELS) in a VG HB-501 dedicated STEM are ideally suited to study such a system. The sensitivity of the Z-contrast imaging technique to high-Z materials makes it ideal for location of the iron particles within the much lower atomic number matrix. As only the high-angle scattering is used in the image formation, EELS can be performed simultaneously from a position defined in the image. This accurate positioning of the probe by the Z-contrast image permits both compositional and bonding information to be obtained with a spatial resolution approaching the atomic scale.
TEM investigation of the low temperature phase of HfV2
Authors: Chu F. , Mitchell T. E.
Published: June 2020

C15 Laves phase intermetallic compounds are potential high temperature structural materials, of which C15 HfV2 is particularly attractive. At room temperatures (RT), the C15 Laves phase has a fcc-based structure with a lattice parameter a=7.4 Å, as shown in Fig. 1. Sensitive specific heat measurements indicate that HfV2 undergoes a structural transformation at 115 K, as shown in Fig. 2. The crystal structure of the low temperature (LT) phase of HfV2 is not unambiguously known, although some studies have been done. A HfV2 alloy was made by arc-melting. The alloy was homogenized at 1200°C for 120h. In a preliminary study we have concentrated on selected area diffraction patterns (SADs) along different zone axes of C15 structure at 83 K, using a Philips CM 30 microscope with a liquid nitrogen cold stage.

A <100>C15 SAD at RT is shown in Fig. 3 (a). At 83 K, SADs along some <100>C15 show (100), (200), and (300) superlattice spots, as shown in Fig 3 (b), while SADs along other <100>C15 indicate (110) and (200) superlattice spots, as shown in Fig. 3 (c).
Energy-filtered plasmon images of MgAl2O4 implanted with Al+ and Mg+ ions
Authors: Evans N. D. , Bentley J. , Zinkle S. J.
Published: June 2020

Magnesium aluminate spinel (MgAl2O4) is a candidate material for specialized applications in proposed fusion reactors, and previously, has been irradiated with Al+ or Mg+ ions to assess the effects of high-dose irradiation. Electron energy-loss spectrometry (EELS) has been used to confirm the identity of metallic aluminum colloids located in the ion-implanted region of the spinel because electron diffraction experiments were inconclusive for phase identification. In the present study, energy-filtered plasmon images of the ionimplanted region have been obtained to reveal this colloid distribution.

Following implantation with 2 MeV Al+ ions to a fluence of 3.8 × 1021 ions/m2 at 923 K, or with 2.4 MeV Mg+ to a fluence of 2.8 × 1021 ions/m2 at room temperature, spinel specimens were prepared in cross-section for analytical electron microscopy. Energy-filtered images were obtained using a Philips CM30 microscope with an attached Gatan Imaging Filter. Acquired images were 512 × 512 pixels in size and gain normalized.
Atom probes as analytical microscopes
Authors: Kelly T. F. , Camus P. P. , Larson D. J. , Bajikar S. S. , Holzman L. M.
Published: June 2020

Analytical microscopes are used to provide compositional and image information at spatial scales from the atomic (nm) to the macroscopic (mm). There are limitations in these techniques, however, and three in particular are noteworthy. 1) Compositional information at the atomic scale is not readily available. 2) The precision of the data is not high (limited to about a few part per thousand). 3) It is difficult or impossible to determine information about the composition in three dimensions.

Atom probe field ion microscopy (APFIM) has historically been able to complement analytical electron microscopes (AEM) at the atomic scale but has not competed with them otherwise. For example, atomic-scale compositional information is inherent to APFIM but it has been difficult to extend this to large dimensions. Furthermore, APFIMs achieve single atom sensitivity which is difficult for AEMs in all but limited situations. In this paper, we consider how atom probes are evolving with capabilities which allow them to not only overcome some of the shortcomings of AEM, but also to compete directly with AEM against its strengths.
Combining atomic imaging, growth, and surface spectroscopy
Authors: Marks L. D. , Collazo C. , Doraiswamy N , Grozea D. , Jayaram G. , Landree E. , Plass R. , Stair P. C.
Published: June 2020

UHV transmission electron microscopy brings several advantages to the study of surfaces including direct imaging of surface structures and surface defects with contrast based on atomic scattering and the ability to obtain information from subsurface layers. Over the last several months our research group has implemented several image and diffraction analysis techniques to enhance these advantages and help determine four noble metal induced silicon surface structures. Perhaps the most significant of these techniques are Wiener and Parametric Wiener image filtering to improve signal to noise levels in off axis HREM images of surface structures, two examples of which are shown in Figs. 1 and 2. Figure 1 is a Parametric Wiener filtered, near Schertzer, off-zone HREM image of Si(lll)-(5×2) Au which clearly shows the rows of gold and also contains some information on the silicon structure between the gold rows. With data from images and χ2 diffraction analysis we have found this structure is basically a Si surface dislocation decorated by two rows of gold atoms.
Removing edge overlapping for maximum usage of EXELFS signal
Authors: Qian Maoxu , Sarikaya Mehmet , Stern Edward A.
Published: June 2020

Extended energy loss fine structure (EXELFS) is an unique tool to determine the local atomic structure of various materials. Compared to X-ray absorption fine structure (XAFS), EXELFS has several advantages, such as having much greater spatial resolution that can be used to investigate phenomena that are spatially inhomogeneous samples, e.g., nanograined materials. In addition, the region being investigated can be characterized by the full capabilities of the TEM such as by imaging and diffraction. Recently, the development of high quality data acquisition and sophisticated data analysis techniques has removed the obstacles for routine use of the EXELFS technique. The applicability of EXELFS is often limited by the edge-overlapping problem due to the close proximity of the edges and the overlap of their fine structures. When this happens, either the desired edge is completely unanalyzable or the usable fine structure range is very narrow and, hence, the uncertainty in the deduced information is too large for reasonable conclusion.
Electron spectroscopic imaging: detection and resolution limits, quantitative evaluation
Authors: Mayer J. , Plitzko J.
Published: June 2020

One of the main applications of the new imaging energy filters is to obtain elemental distribution images by electron spectroscopic imaging (ESI). Before the technique can successfully be applied to new materials problems it is important to evaluate the detection and resolution limits which have to be expected. Since the intensities in ESI images recorded with inner shell loss electrons are very small, the detection limit is governed by the signal to noise ratio (S/N). In a systematic study we have evaluated the performance of three different electron microscopes, a Zeiss EM 912 Omega, a Philips CM 20, and a Jeol ARM 1250, the latter two being equipped with a Gatan imaging filter (GIF). As experimental systems we chose amorphous oxide grain boundary films in Si3N4 ceramics and thin diamond films on silicon substrates. Furthermore, new routines were developed to extract EELS spectra from a whole series of ESI images. These EELS spectra can be used to study the local variation of the near edge fine structure (ELNES) or, after quantitative evaluation, of the chemical concentration of certain elements.
Quantitative analysis of spatially resolved valence electron energy-loss spectra for electronic structure studies of grain boundaries and thin intergranular films
Authors: French Roger H.
Published: June 2020

The spatial variation of the electronic structure at interfaces is critical to both interatomic bonding at atomically abrupt interfaces such as grain boundaries and also to the development of van der Waals (vdW) attraction forces at partially wetted interfaces. This interfacial electronic structure, as represented by the interband transition strength , can be determined by Kramers Kronig (KK) analysis of either vacuum ultraviolet (VUV) optical reflectance spectra or spatially resolved valence electron energy loss (SR-VEEL) spectra. Quantitative analysis of SR-VEELS requires accurate spectral line shapes coupled with single scattering deconvolution, convergence correction, and KK analysis. Both the energy loss functions (Fig. 1) and the interband transitions (Fig. 2) determined for α-Al2O3 using SR-VEELS compare well with the VUV results. In addition the use of the spectral line scan method, whereby typically 200 SR-VEEL spectra are acquired along a scan line of 20 nm, helps overcome many uncertainties in the data acquisition and analysis.
Olivine-MgO interfaces produced by crystallization of glass fulms on single-crystal MgO substrates
Authors: Ramamurthy Sundar , Hebert Brian C. , Barry Carter C.
Published: June 2020

Glassy silicates are present at grain boundaries in almost all liquid-phase sintered ceramic oxides. In many cases, the amorphous-crystalline interfaces in the sintered microstructure can be modified by inducing crystallization of the glassy phase. The intergranular phases in polycrystalline MgO are typically silicates with cations of calcium, magnesium and iron in the silicate network. A systematic approach to study the crystallization behavior of glass-MgO interfaces has been attempted in the present study. Following the work by Mallamaci in which crystallization of a silicate glass in contact with A12O3 was studied, devitrification of glass in contact with single-crystal MgO has been investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the resulting microstructures.

A pellet of Mg2SiO4 (forsterite) prepared by hot-pressing MgO and SiO2 powders was used as the target for depositing glass films onto single-crystal MgO substrates by pulsed-laser deposition (PLD). Glass films with the composition of olivine.
Surface morphology of xenon implanted single crystal magnesium oxide observed by Atomic Force Microscopy
Authors: Jiang Wenbiao , Grant Norton M. , Poker David B.
Published: June 2020

The implantation of materials with noble gas ions is of particular interest in studying some of the fundamental aspects of the ion implantation process and resultant phenomena because the noble gas ions are immiscible with the matrix and therefore chemical effects are unlikely. Electron diffraction studies have clearly demonstrated that noble gas ions implantated into either metals or ceramics may coalesce to form inclusions. These inclusions may be either solid or fluid and their formation often results in swelling of the matrix. This swelling can be readily apparent on the surface of metallic materials. However, in ceramic materials the extent of this swelling, particular at low ion fluences, can be very small and hence only detectable with surface sensitive topographic probes such as atomic force microscopy (AFM).

Polished (00l)-oriented MgO single crystals were implanted with xenon ions using an accelerating voltage of 200 keV at a range of fluences. The specimens were then examined with AFM. The AFM results showed that, even at the lowest fluence, there was measurable roughening of the surface. At a fluence of 1 × 1017/cm2 small blisters were observed. These blisters have diameters of 0.5 - 0.8 μm and extend to heights of up to 80 nm.
The determination of the Pr valence state in (Pr1.5Ce0.5)Sr2Cu2NbO10 compound by Electron Energy Loss Spectroscopy
Authors: Cheng S. C. , Dravid V. P.
Published: June 2020

The debate on the Pr valence state in PrBCO compounds is well documented. Recently (Pr1.5Ce0.5)Sr2Cu2NbO10(RCeSCNO) system has been synthesized and studied. In this paper, the results of our study to determine the valence of Pr in PrCeSCNO, which has similar property of PrBCO are presented. Typical EELS spectrum of Pr M45 edges with Ce M45 edges from (Pr1.5Ce0.5)Sr2Cu2NbO10 is shown in Fig. 1. In Fig. 1 the energy position of Ce M45 edges were taken at 883.0 eV and 901.0 eV. The Ce M45 edges were used to calibrate the energy axis, so that the position of Pr M45 edges could be accurately measured. The measured energy positions of Pr M45 edges in PrCeSCNO and in Pr2Ce2O7 and Pr2Ce2O8, which were used to obtain the spectra of trivalent and tetravalent Pr compounds, are also listed in table 1. The spectra taken from these compounds are shown in Fig. 1 (a) and (b).
Surface spectroscopic studies of model supported-metal catalysts
Authors: Wayne Goodman D.
Published: June 2020

A new surface science approach to the study of supported-metal catalysts will be described. Thin oxide films (~100 Å) of SiO2, Al2O3, or MgO supported on a refractory metal substrate (e.g., Mo or W) have been prepared by depositing the oxide metal precursor in a background of oxygen (ca. l×l0-5 Torr) [1]. The thin-film catalysts facilitate investigation by an array of surface techniques, many of which are precluded when applied to the corresponding bulk oxide [1,2]. In particular, the oxide films have been characterized by AES, ELS, HREELS, XPS, UPS, ISS, IRAS, and TD spectroscopies and shown to have essentially identical electronic and vibrational properties of the corresponding bulk oxides. These studies indicate then that these films can serve as convenient models for oxide catalysts or metal supports. Metal thin films (e.g., Cu, Pd, Ni) have subsequently been deposited onto the oxide films and the properties of the metal/oxide system then studied with the above array of surface techniques [3]. By properly defining the metal thin film thickness, metal particles of varying sizes can be synthesized with dispersions from a few nanometers to tens of nanometers.
Detection of a point defect in a silicon single crystal by high-resolution TEM
Authors: Awaji M.
Published: June 2020

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.

The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.
TEM investigation of the YSZ-on-insulator structure
Authors: Zhou D.S. , Jia Q.X. , Wu X.D. , Mitchell T.E.
Published: June 2020

Silicon-on-insulator (SOI) structures have been widely used in the semiconductor industry as substrates to grow various devices. They are usually prepared by a process called separation by implantation of oxygen (SIMOX). As an alternative, single crystal yttria-stabilized-zirconia (YSZ) can be grown on single crystal silicon substrates, followed by heat treatment in oxygen to form an intermediate SiO2 layer. This YSZ-on-silicon structure has the potential to be used as a new SOI material in semiconductor device fabrication.

YSZ has a cubic (fluorite type) structure with a lattice parameter of 0.514 ~ 0.523 nm (as compared to 0.543 nm for silicon) depending on its Y2O3 content. The good lattice match between YSZ and silicon makes epitaxial growth possible. In this experiment, the pulsed laser deposition technique has been employed to grow YSZ thin films on single crystal p-Si (100) wafers. Post-deposition heat treatment was carried out at 850°C for 1.5 h in dry oxygen at 1 atmosphere. The structure was first examined by Rutherford backscattering spectrometry and x-ray diffraction, and then by cross-sectional transmission electron microscopy (XTEM) techniques.
Lorentz observation of magnetic domains in terfenol-d
Authors: Dooley J. , Nuhfer N.T. , De Graef M.
Published: June 2020

Terfenol (Tb.27Dy.73Fe1.95) has the largest known room-temperature magnetostriction coefficient, making it well suited for low frequency, high power sonar applications. Terfenol takes the MgCu2 cubic Laves phase structure, with lattice parameter a = 0.732 nm and space group Fd3m. Magnetic domain configurations in this material are generally interpreted as 71° and 109° walls, along with 180° walls, with the magnetization along the 〈111〉 directions. At room temperature the cubic unit cell experiences an extremely small rhombohedral distortion along the magnetically soft 〈111〉 directions (e.g., the cubic [100] tilts by 1.13 mrad toward a new orientation). The growth direction, designated [11], is taken as a reference throughout this discussion.

The material, prepared by a free-standing float-zone (FSZ) technique, was provided by Etrema Products Inc. in the form of [11] oriented rods with a diameter of 3 mm. Since the growth direction is perpendicular to [111] and the growth front is dendritic, growth twins are easily formed by a 180° rotation on the (111) plane.