bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Resolution SEM of Colloidal Gold Labels
Authors: Albrecht Ralph M. , Simmons Scott R. , Prudent James R. , Erickson Chris M.
Published: June 2020

Colloidal gold, conjugated to a number of biologically active molecules, including ligand and antibody, provides a useful label for light microscopy and electron microscopy. This stems, in part, from its color, density, and regular spherical shape although the ability to make the particles in a number of defined sizes, the ease of conjugation to biological material, and the retention of activity of bound molecules are also important factors.

Although nearly all sizes of colloidal gold particles, from 2.0 nm on up, can be identified in transmission or high voltage transmission electron microscopy, it has generally been the larger sized particles, 15 nm and up, that have proved useful for scanning electron microscopic studies. This is due principally to the resolution limits of conventional SEMs and the need to employ backscattered electron imaging, BEI, to unambiguously define the gold labels.
Contrast and Resolution in the ESEM
Authors: Danilatos G. D.
Published: June 2020

The basic theory of contrast arid resolution for the SEM is applicable to the environmental scanning electron microscope (ESEM) except that it must be extended to include the effects of the gaseous environment on the beam-specimen—signals system. The resolution depends on the detection mode and the associated beam specimen interaction volume, provided there is enough contrast for a particular feature to become visible. The ultimate resolution (resolving power) is limited by the precise electron beam profile as it propagates through the gas. This has been examined in a previous presentation here and the overall topic has been surveyed in detail elsewhere.

There are two different situations under which the resolving power is considered: (i) When the electron skirt (scattered electrons) is comparable with the original spot size (unscattered electrons). This can happen in the case of a very broad beam, where the scattered electrons fall in the neighborhood of the original spot and cannot be easily distinguished from the unscattered ones.
Ultrastructure of Ligament Extracellular Matrix After Chondroitinase ABC Digestion
Authors: Bray D. F. , Frank C.
Published: June 2020

The cationic stain ruthenium hexammine trichloride (RHT) has been utilized as a connective tissue stain primarily due to its ability to stabilize and stain anionically-charged glycosaminoglycans (GAGs). A major drawback of this procedure however is that the increased preservation and visibility of the GAGs obscures other RHT-stained constituents of the “ground substance”. In order to more readily visualize these non-GAG ground substance components ligament tissue was pre-treated with chondroitinase ABC, an enzyme that removes most, if not all of the GAGs present.

Segments of the midsubstance of medial collateral ligaments (MCL) of mature New Zealand white rabbits were excised and incubated 1 hat 37°C in chondroitinase ABC (1 U/ml in 0.25M Tris, 0.18M NaCl, 5mM benzamidine HC1, 0. 1. 6-amino-n-caproic acid, pH 8.0) followed by fixation in Na-cacodylate (0.1M, pH 7.4) buffered glutaraldehyde (2.5%) containing RHT (lmg/ml) for 2.5 h. Post-fixation for 1 h in cacodylate-buffered osmium tetroxide (1%) plus RHT (lmg/ml) preceded ethanol dehydration and embedding in Spurr's resin.
Deformation of Yeast Plasma Membrane by Ethidium Bromide
Authors: Keyhani E.
Published: June 2020

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.

Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.

Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.
Occurrence of abundant autophagosomes in bird hepatocytes
Authors: Keyhani E.
Published: June 2020

Autophagy is a process by which the cytoplasm of the cell segregates and degrades endogenous macromolecules and organelles. Autophagy plays an important role in the degradation of intracellular components during physiological cell functioning. This paper describes the morphology of bird hepatocytes with reference to abundant formation of autophagosomes.

Six house sparrows were purchased from a local dealer, and, on examination, all were apparently healthy, did not show any sign of starvation or disease. Their liver was removed after cervical dislocation and was doubly fixed with glutaraldehyde-osmium, and processed with conventional methods.

The hepatocytes were generally polyhedral, sometimes slightly oval. The nuclei were round, slightly eccentric and contained one or two prominent nucleoli. Nuclear chromatin exhibited the normal structure and organization of hetero- and euchromatin. The cytoplasm showed abundant mitochondria round and elliptic. No intramitochondrial vacuolization and swelling were seen and cristae exhibited the normal structure described for liver cells. The Golgi apparatus was poorly developed.
Trophoblast ultrastructure in murine interspecies pregnancy
Authors: Crepeau M. , Yamashiro S. , Bast T. , Croy B.A.
Published: June 2020

Mus caroli blastocysts transferred to the uterus of pseudopregnant Mus musculus implant but do not survive past midgestation. Blastocyst microsurgery has been used to show that trophoblast is the tissue responsible for pregnancy failure but the nature of the failure remains undefined. Therefore a histological study, was undertaken to compare development of M. caroli embryos in M. musculus and M. caroli uteri at a time point just prior to development of grossly observable lesions.

Seven transferred M. caroli embryos and six transferred M. musculus embryos were recovered from three M. musculus recipients on day 8.5 of gestation. Four M. caroli embryos recovered from a M. caroli uterus on day 7.5 of gestation were used as stage-matched controls. For light microscopy, 2 μm thick, glycol methacrylate embedded (3), sections of implantation sites were stained with H & E or periodic acid-Schiff (PAS). For electron microscopy, small pieces of the tissues were fixed and processed routinely.
Electron microscopic study of respiratory syncitial (RS) virus: A new approach
Authors: Alain R. , Bélanger F. , Berthiaume L. , Trudel M.
Published: June 2020

The respiratory syncytial (RS) virus is included in the Paramyxoviridae family, genus Pneumovirus. In the present study, three strains were compared: human (HRS), bovine (BRS) and caprine (CRS). The ultrastructure of HRS virus has been previously described according to conventional methods of negative staining and ultrathin sectioning (Berthiaume et al., 1974). Recently, bridges between BRS particles in ultrathin sections were noted (Bélanger et al., 1988). Bridges were also observed with CRS (unpublished results). We were interested in studying, by negative staining, what produced these bridges and why they were present on BRS and CRS particles and not on HRS.

Human, bovine and caprine RS virus were propagated in ovine kidney (OK) cells. After 5 to 7 days post-infection, when viral titers were at a maximum, supernatants were collected. They were separated in two parts: the first aliquot was used without treatment immediately after collection; the second aliquot was immediately fixed with glutaraldehyde (final concentration of 0,5% (v/v)) and after ten minutes fixation, samples were prepared for electron microscopy.
Quantitative changes of organelles in early cirrhosis of rat
Authors: Ryoo J. W. , Buschmann R. J.
Published: June 2020

Cirrhosis involves major architectural changes in the liver. The changes are appreciated histologically as regenerative nodules and septa, but they do not reflect directly the structural/functional changes which must occur at the subcellular level. In order to test for these subcellular changes, we chose to carry out a morphometric analysis of two organelle systems that are most likely to be affected in liver cirrhosis.

Early cirrhosis was produced by CC14 inhalation along with phenobarbital continuously in the drinking water (CCl4+PB). Two groups of control rats were used. One group was given neither the CCI4 nor the phenobarbital (CONT); the other group was given just the phenobarbital (PB). After 8 wk the rat livers were fixed by perfusion, The left lobe was isolated, weighed, and its volume determined. Tissue was prepared for electron microscopy. Micrographs of random areas of hepatocyte cytoplasm (36000x), hepatocyte mitochondria (90000x), and Ito cell cytoplasm (54000x).
Ultrastructural observations in two cases of acute pyelonephritis
Authors: Caughey R.C. , Kelly C.E.
Published: June 2020

In two histologically diagnosed cases of acute pyelonephritis, several ultrastructural features were observed. The transmission electron microscope (TEM) highlights the bacterial adhesion, inflammatory process, phagocytosis and lysosomal release characteristic of pyelonephritis.

The renal biopsies from both patients were fixed in 2.5% glutaraldehyde, rinsed with Millonig's buffer, and post fixed with 1% osmium tetroxide. They were then en bloc stained with 0.5% uranyl acetate, rinsed with Walpole's buffer, dehydrated with a graded series of ethanols and embedded with Epon 812 epoxy resin. Ultramicrotomy thin sections were stained with uranyl acetate and lead citrate and scanned using a JEOL - JEM100C.

Using the TEM, bacteria are seen in tubular epithelial cells, phagocytized to the basement membrane, within cells of the tubular lumen, and within the polymorphonuclear leukocytes (polys). Bacteria may also be seen phagocytizing within cells in the tubular lumen. The inflammatory response of polys is seen in the tubular lumen and interstitium, and attached and within the tubular basement membrane.
A web-like network of type vi collagen in human skin is revealed by immuno-electron microscopy
Authors: Keene Douglas R. , Glanville Robert W. , Engvall Eva
Published: June 2020

A mouse monoclonal antibody (5C6) prepared against human type VI collagen (1) has been used in this study to immunolocalize type VI collagen in human skin. The enbloc method used involves exposing whole tissue pieces to primary antibody and 5 nm gold conjugated secondary antibody before fixation, and has been described in detail elsewhere (2).

Biopsies were taken from individuals ranging in age from neonate to 65 years old. By immuno-electron microscopy, type VI collagen is found to be distributed as a fine branching network closely associated with (but not attached to) banded collagen fibrils containing types I and III collagen (Fig. 1). It appears to enwrap fibers, to weave between individual fibrils within a fiber, and to span the distance separating fibers, creating a “web-like network” which entraps fibers within deep papillary and reticular dermal layers (Fig. 2). Relative to that in the dermal matrix, the concentration of type VI collagen is higher around endothelial basement membranes limiting the outer boundaries of nerves, capillaries, and fat cells (Fig. 3).
Demonstration of somatomedin c/insulin-like growth factor I (SM-C/IFG-I) and growth hormone (GH) bindings on chick embryo tissues
Authors: Wang J. J. , Teng C. S.
Published: June 2020

The presence of SM-C/IGF-I has been described on chick embryo tissues. The binding of endogenous GH on Mullerian ducts (Mds) has been detected previously. Recently, the presence of SM/IGF and SM/IGF receptors were identified in 9-12 day-old mouse embryos. These evidences indicate that SM-C/IGF-I and GH are involved in embryonic development.

Antiserum against porcine GH and anti-SM-C/IGF-I antibody were used as primary antibodies for immunocytochemical labelling probes by the avidin-biotin complex (ABC)-gold technique. There is no or very weak cross reactions between these two antibodies by ELISA. Chick embryos and Mds were fixed in 2.5% glutaraldehyde for 30 minutes. Washes with phosphate buffer were administered between each of the following incubations: 1. 2% bovine serum albumin, 2. Primary antibody (1/200 dilution), 3. Biotinated secondary antibody (1/100), 4. Avidin conjugated with gold particles (1/50). The 10-day Mds were double labelled with SM-C/IGF-I-gold and then with MIS-peroxidase (MIS-PO) as described before.
Thick-sectioning characteristics of vitreous carbon microtome knives
Authors: Disharoon D. R. , Wickham M. G. , Myrick J. J.
Published: June 2020

Since the introduction of vitreous carbon microtome knives progress has been made on improving the quality of the cutting edge. It has been found that long uniform edges produced by mechanical lapping are superior to cleaved edges. Knife edges of 12.5mm to 25mm with 45° cutting angles have been produced, mounted for ultramicrotomes in aluminum boats (Fig. 1) and alpha tested under routine microtomy conditions. In tests at independent laboratories, the 25mm, 45° knives were found to produce routine l-2μm thick sections of a variety of materials embedded in a range of media.

Vitreous carbon was commercially obtained in square sheets, 76mm X 76mm X 3mm, cut and processed for polishing by standard machine grinding. Uniform edges with 45° cutting angels were produced by lapidary procedures incorporating the sequential use of fine polishing grits.
Preparation and staining of hard seed tissue for backscatter imaging
Authors: Paul R. N. , Egley G. H.
Published: June 2020

Hard seed coat material is extremely difficult to prepare for observation at the EM level. Seed coat segments are usually removed for embedding and sectioning, which results in loss of tissue juxtaposition. Observation and monitoring reactions of the intact seed coat under experimental procedures such as tracking dye penetration into seeds make seed coat dissection unfeasible. Efforts to apply analytical EM methods such as STEM/EDS analysis, are restricted by the limiting effect of section thickness on X-ray signal. We investigated the ultrastructure of dry seeds by treating them with various metallic staining solutions and observing the trimmed block faces with the SEM in backscatter mode. Good structural information was obtained as well as visualization of a specific tissue layer that accumulates lead.

Intact seeds were incubated in several aqueous solutions including: 2% w/v uranyl acetate; 1% w/v OsO4; 2% ferrous chloride (Followed by 5% potassium ferricyanide to form an insoluble precipitate) ; and various lead solutions including Reynolds lead citrate.
New replica method with plasma polymerized film by glow discharge
Authors: Tanaka A. , Yamaguchi M. , Hirano T.
Published: June 2020

The plasma polymerization replica method and its apparatus have been devised by Tanaka (1-3). We have published several reports on its application: surface replicas of biological and inorganic specimens, replicas of freeze-fractured tissues and metal-extraction replicas with immunocytochemical markers.

The apparatus for plasma polymerization consists of a high voltage power supply, a vacuum chamber containing a hydrocarbon gas (naphthalene, methane, ethylene), and electrodes of an anode disk and a cathode of the specimen base. The surface replication by plasma polymerization in negative glow phase on the cathode was carried out by gassing at 0.05-0.1 Torr and glow discharging at 1.5-3 kV D.C. Ionized hydrocarbon molecules diffused into complex surface configurations and deposited as a three-dimensionally polymerized film of 1050 nm in thickness.

The resulting film on the complex surface had uniform thickness and showed no granular texture. Since the film was chemically inert, resistant to heat and mecanically strong, it could be treated with almost any organic or inorganic solvents.
Progress in near-field scanning optical microscopy (NSOM)
Authors: Betzig E. , Isaacson M. , Barshatzky H. , Lin K. , Lewis A.
Published: June 2020

The concept of near field scanning optical microscopy was first described more than thirty years ago1 almost two decades before the validity of the technique was verified experimentally for electromagnetic radiation of 3cm wavelength.2 The extension of the method to the visible region of the spectrum took another decade since it required the development of micropositioning and aperture fabrication on a scale five orders of magnitude smaller than that used for the microwave experiments. Since initial reports on near field optical imaging8-6, there has been a growing effort by ourselves6 and other groups7 to extend the technology and develop the near field scanning optical microscope (NSOM) into a useful tool to complement conventional (i.e., far field) scanning optical microscopy (SOM), scanning electron microscopy (SEM) and scanning tunneling microscopy. In the context of this symposium on “Microscopy Without Lenses”, NSOM can be thought of as an addition to the exploding field of scanned tip microscopy although we did not originally conceive it as such.
Scanning tunneling microscopy of biomacromolecules
Authors: Stemmer A. , Engel A. , Häring R. , Reichelt R. , Aebi U.
Published: June 2020

Since its invention in the early 1980s the scanning tunneling microscope (STM) has rapidly evolved into a well established tool in solid state physics for surface structure analysis at atomic resolution. Recently a growing interest in the STM for investigating biological matter has been expressed, since surface ‘topographs’ of biomacromolecules can be recorded at ambient pressure or possibly in buffer solutions, thereby eliminating structural alterations induced by specimen dehydration such as required for electron microscopy (EM).

As simple as a STM may look, it provides a wealth of information ranging from mere surface topography and local variations in the tunnel-barrier height to local spectroscopy of electronic states and elasticity. On the other hand the physics involved in imaging biological specimens such as protein or DNA, membranes, or fatty acid monolayers, which are generally known to be poor conductors, is not quite understood yet. To cope with insulators the atomic force microscope (AFM), a relative of the STM, provides a means to obtain topographs and elasticity data.
Amorphization of Zr3Al by 1-MeV electron radiation
Authors: Koike J. , Okamoto P.R. , Rehn L.E. , Meshii M.
Published: June 2020

A crystalline to amorphous transition during high energy particle radiation has been reported in various intermetallic compounds. Chemical disordering is known to precede amorphization, which takes place only below a certain temperature. In Zr3A1, chemical disordering has been observed during 1-MeV electron radiation at temperatures between 130 and 375K but no amorphization has been reported. A large decrease in shear modulus was also observed during chemical disordering of Zr3Al by 1-MeV Kr ion irradiation at room temperature, followed by amorphization. In the present work, the possibility of amorphization of Zr3Al by electron radiation was examined, and the lattice softening due to chemical disordering was studied with electron diffraction.

An alloy with a nominal composition of Zr-25at%Al was furnished by Chalk River National Laboratory. It was annealed at 925°C for 2 weeks and subsequently sliced and jet-polished. Specimen was irradiated and examined at 52K with 1-MeV electrons in the Argonne-HVEM.
Precipitation in silicon: Microanalysis
Authors: Carpenter R.W.
Published: June 2020

Interest in precipitation processes in silicon appears to be centered on transition metals (for intrinsic and extrinsic gettering), and oxygen and carbon in thermally aged materials, and on oxygen, carbon, and nitrogen in ion implanted materials to form buried dielectric layers. A steadily increasing number of applications of microanalysis to these problems are appearing. but still far less than the number of imaging/diffraction investigations. Microanalysis applications appear to be paced by instrumentation development. The precipitation reaction products are small and the presence of carbon is often an important consideration. Small high current probes are important and cryogenic specimen holders are required for consistent suppression of contamination buildup on specimen areas of interest. Focussed probes useful for microanalysis should be in the range of 0.1 to 1nA, and estimates of spatial resolution to be expected for thin foil specimens can be made from the curves shown in Fig. 1.
Precipitation of hydrogen in crystalline silicon
Authors: Ponce F. A. , Johnson N. M.
Published: June 2020

The behavior of hydrogen in semiconductors has been a topic of increasing interest in recent years. The interest is in part stimulated by the ability of hydrogen to remove the electrical activity (passivate) of both dopant impurities and deep-level defects at moderate temperatures (<300C). Hydrogen is known to readily diffuse in silicon resulting in the neutralization of shallow-acceptor and shallow-donor dopants, Controlled studies of the role of hydrogen in silicon has been recently reported. This was achieved by exposing silicon single crystals to monoatomic hydrogen or deuterium from a microwave gas discharge. To prevent the radiation damage that results from direct exposure to the plasma, the specimens were mounted on a hot stage that was located down stream from the plasma. Optical isolation was achieved with the use of baffles. The specimen temperature was held constant in the range of 100-400°C for time intervals between 10-120 minutes.
Semi-coherent precipitation of silicon nitride in silicon
Authors: Kaushik V. S.
Published: June 2020

Implantation of nitrogen into silicon, followed by high-temperature annealing causes formation of silicon nitride. At high doses, continuous polycrystalline layers are formed, while at lower doses, discrete precipitates are formed. These precipitates show preferred orientation with the silicon matrix. This paper presents the results of characterization of these semi - coherent precipitates using electron diffraction and cross-section TEM.

Silicon (110) was implanted with 150 KeV N+ ions at a dose of 1 x 1018 /cm2 at 500° C at near-normal incidence. Annealing was carried out at 1200° C for thirty minutes in a nitrogen atmosphere. The samples were then analyzed by XTEM using a JEOL 2000 FX STEM operated at 200 kV with the electron beam parallel to [112] Si. A continuous polycrystalline layer of silicon nitride was observed at the mean ion range. In addition, a band of precipitates of α-Si3N4 was observed at about 1 μm below the wafer surface, presumably corresponding to the fraction of ions channeled along [110] Si.
Heterogeneous precipitation on misfit dislocations in Si/Si-2%Ge epitaxy
Authors: Posthill J.B. , Lee D.M. , Shimura F. , Rozgonyi G.A.
Published: June 2020

Metallic impurities such as Au, Ni, Cu, Fe, etc. are known to degrade the performance of electronic devices. Therefore, necessary precautions must be taken to ensure that impurity contamination is minimized. Nevertheless, some degree of inherent and process-induced impurity introduction into silicon crystals is unavoidable. An intrinsic gettering annealing cycle can be utilized to nucleate metallic precipitates on dislocations produced upon SiO2precipitation.eg.1 Another impurity gettering approach is the intentional introduction of a controlled, stable array of dislocations to act as heterogeneous nucleation sites. This is one type of extrinsic gettering scheme. This contribution addresses our ongoing studies pertaining to extrinsic gettering by an orthogonal grid of b=1/2<011> 60° misfit dislocations generated in Si/Si-2%Ge epitaxy. Additionally, the prospect of uniformly decorating dislocations with a conducting metal presents the technological opportunity for forming buried micro-wires as proposed previously.

A buried Si-2%Ge epitaxial layer of ˜ 2 μm thickness was grown on (001) silicon substrates at 1080°C by chemical vapor deposition. The Ge concentration is defined as the ratio of GeH4to SiH2Cl2. On top of the Si-2%Ge layer, a 4-13 μm pure silicon capping epilayer was grown. Misfit dislocations were generated at both of the Si/Si-2%Ge interfaces.
Energy loss extreme — near-edge and pre-edge structure
Authors: Batson P.E.
Published: June 2020

During the past several years we have begun to understand many features of the core loss excitations including absolute crosssections, extended fine structure, (EXELFS) and near edge fine structure. (ELNES) In electronic materials near interfaces or defects, we expect the valence and conduction bands to be modified by the existence of isolated resonances, broadening of the band edges, or a completely filled gap region. These electronic changes have been observed with high resolution EELS in the low energy loss region (0-3eV) where direct inter-band transitions are likely. The present work is aimed at determining if pre-edge structure near the core loss scattering may reflect local changes in the electronic structure as well. There are two major experimental difficulties: 1) the necessary energy resolution is of order 0.1-0.3eV in order to define the shape of the core edge; and 2) the energy differential scattering cross section is small (of order 10-23cm2eV-1). At IBM I have addressed these problems by constructing a high resolution energy loss spectrometer system with parallel recording to allow signal collection in reasonable times.
Oxygen K near edge structures studied with multiple scattering calculations
Authors: Weng Xudong , Rez Peter
Published: June 2020

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.
Ab initio band theory approach to electron energy loss near edge structures
Authors: Weng Xudong , Sankey O.F. , Rez Peter
Published: June 2020

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.

In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.
Improving the accuracy of convergent-beam thickness measurements
Authors: Christenson K. K.
Published: June 2020

Convergent-beam diffraction patterns taken at appropriate “two-beam” conditions allow simple, rapid determinations of a specimen's thickness, extinction length and even its anomalous absorption coefficient (1,2). We here note three points to consider when obtaining the pattern.

First, in thickness measurements the ratio of the fringe spacing to the spacing between the disks is utilized; there is an underlying assumption that the two distances are on the same angular scale. This assumption is incorrect if the illumination crossover is not in the plane of the specimen and simultaneously, the diffraction lens is focused incorrectly. If the crossover is at the specimen (Fig. 1a), varying the focus of the diffraction lens (changing w) varies the distance between the disks and the sizes of features within the disks in the same way, only the magnification of the pattern is changed. Likewise, if the diffraction lens is focused correctly, on the back focal plane of the objective lens, the angular scale within the disks matches that between the disks and neither scale is affected by variations in the illumination.
Spatial resolution limits in EELS spectroscopy and imaging
Authors: Colliex C. , Mory C.
Published: June 2020

In analytical problems, EELS is a powerful technique to locate, identify and measure the atoms contained within volumes of very small size. The present study is an experimental investigation of its resolution limits on a test specimen made of small metallic Tb and U clusters down to the atomic size and lying on a thin amorphous carbon layer. Several parameters have to be determined : the spatial resolution power (d), the minimum detectable concentration (Co) and the ultimate number of detectable atoms N = Co d2 tn within a specimen of local thickness t. The used instrument is a dedicated FEG-STEM VG HB 501 equipped with a Gatan spectrometer and governed by a home made digital acquisition system. This equipment offers unique capabilities for complete data quantification : the simultaneous acquisition for each pixel of two information channels (the annular dark field (adf) and the bright field one after the spectrometer) allows to discriminate the primary probe contribution from the inelastic effect. Sequences of up to 10 energy filtered images are acquired for different loss values covering the EELS range of interest from below the U-O45 edge (at 105 eV) to above the Tb-N4B edge (at 155 eV).
A simple parameterization scheme for inner-shell cross sections
Authors: Egerton R.F.
Published: June 2020

Quantitative elemental analysis by electron energy-loss spectroscopy requires values of core-loss cross section σ(β,Δ) integrated up to a scattering angle β and over an energy range Δ above the ionization threshold. Such cross sections can be calculated using atomic models [1-3], neglecting solid-state effects. They can also be determined experimentally [4,5], but only for particular values of β,Δ and incident energy E0. By representing σ(β,Δ) in terms of an integrated dipole oscillator strength f(Δ) which is independent of β and E0, we realize two advantages: (1) measurements on solids can be directly compared with one another and with theory, and (2) values of σ(β,Δ) for K, L and M edges can be derived from tabulated values of f(Δ) by use of a hand calculator or a very short computer program.
The effects of chromate deoxidizer treatment parameter variation on surface morphology and adhesive bonding of 2219-T87 aluminum
Authors: Rowland L. J. , Allgeyer D. F. , Brown R. J.
Published: June 2020

The shell of the Space Shuttle's External Tank is 2219-T87 aluminum to which an epoxy primer is applied to allow bonding of the Thermal Protection System (TPS). A chromate deoxidizer is used to prepare the aluminum surface for primer bonding. In this study, scanning electron microscopy (SEM) was used to characterize the surface morphology of 2219-T87 aluminum associated with different bond strengths produced by varying the deoxidizer treatment parameters.

Eight sets of two 2219-T87 aluminum panels were treated with chromate deoxidizer. One set was used as a control. The second set was subjected to an additional deoxidizer treatment, while the third set received two additional deoxidizer treatments. The fourth, fifth, and sixth sets were held for 5, 10, and 15 minute post deoxidiation and prior to final rinse with demineralized water. The two remaining sets were deliberately contaminated with 25:1 and 100:1 water:deoxidizer solutions, which were allowed to dry on their surfaces.
HRTEM of antigorite: The structure as a polysomatic series
Authors: Spinnler Gerard E. , Otten Max T.
Published: June 2020

Antigorite is one of the serpentine minerals, a group of 1:1 layer silicates with the approximate composition of Mg3Si2O5(OH)4. These minerals display an unusual variety of crystal structures even though they are almost identical in composition; chrysotile has an elongated-tube structure, lizardite occurs as flat plates, and antigorite has corrugates layers.

The details of the crystal structures of the serpentine minerals are not completely known. Threedimensional structure refinements only exist for one- and two- layer lizardite. For antigorite, the only direct structural information consists of a two-dimensional Fourier synthesis of hOI diffractions. The lack of detailed structural data on these minerals arises from the complexity of the structures as well as the paucity of sufficiently large, well-formed single crystals. In addition, structural disorder is common in these minerals, making structure refinement difficult.

High resolution transmission electron microscopy (HRTEM) has been used to study antigorite in order to discriminate among various structural models of antigorite and to characterize its microstructures
TEM Studies of modulated structures in the monoclinic (B) phase Of CaO-stabilized Dy2O3
Authors: Kim Y. J. , Kriven W. M.
Published: June 2020

Dysprosia (Dy2O3) undergoes a monoclinic (B) to cubic (C) transformation on cooling through 1950°C, which is accompanied by an 8% volume increase and shattering. Minor additions of CaO combined with rapid quenching, however, are able to stabilize the high temperature phase down to room temperature. The similarities with the tetragonal to monoclinic transformation of ZrO2 suggest that it may be a possible high temperature transformation toughener. A sample of 8 mol% CaO was sintered at 1900°C and cooled at an intermediate rate. About 90% of B phase, which invariably had a modulated structure, was retained.

From TEM studies of this B phase, it was shown that most of the selected area diffraction (SAD) patterns in different orientations consisted mainly of three types of reflections: (i) major reflections from the monoclinic lattice; (ii) satellites associated with each major reflection; and (iii) split reflections at the middle of the framework of major reflections. Depending on the orientation, (ii) and (iii) were accompanied by twinned reflections. Fig. 1 displays (i) and (iii) type reflections.
Microstructural analysis of sputtered titanium nitride ceramics
Authors: Dabrowski B. W.
Published: June 2020

Titanium Nitride, TiN, is an attractive ceramic material in the tool and electronic industries because of its high hardness, corrosion resistance and high electrical conductivity. TiN was investigated for use as a high reliability electrical contact material to replace gold in certain microelectronics applications. However, the optimal contact resistance values were not always reproducible despite processing with stable and repeatable sputtering parameters, use of ultra-pure gases, and a high-base vacuum. It was suspected that these inconsistentcies could be due to subtle changes in the microstructure. Therefore, the purpose of this paper is to present the initial results from a TEM study of TiN thin films.

Approximately 5μm thick TiN films were deposited onto a variety of substrates by the CTS Corporation in a UHV reactive sputtering system [1], Through-foil orientations of the films were obtained by grinding the substrate side to a total thickness of ∼15 μm.
The role of boundary plane: HREM investigation of the atomic structure of grain boundaries in gold
Authors: Merkle K. L.
Published: June 2020

Computer simulations of large-angle grain boundaries (GBs) have indicated the importance of local atomic relaxation, rigid body translations, and of the boundary plane in determining GB energy. Experimental observations of GB structure often find GB faceting, which is an indication that some GB planes are preferred over others. Investigations of the atomic structure of large-angle >001> tilt GBs in NiO have shown, along with symmetrical GB con-figuations, the presence of asymmetric GBs of the type which has at least one of the crystals terminated at the boundary by a low index plane. Such boundaries are thought to be of low energy. For studying the role of the GB plane in a metallic GB we chose in the present work two <011> tilt boundaries in Au. The misorientation angles (θ) were selected such that one bicrystal orientation (θ=39°) was close to the Σ=9 reciprocal coincident site density, while the other (θ=55°) was near the misorientation for which (111) and (100) planes are parallel to each other (θ=54.74°). The latter misorientation is also close to Σ=41 (θ=55.88°).
Structure of an asymmetrical tilt boundary in gold
Authors: Norden Hans , Smith David A.
Published: June 2020

Balluffi and coworkers developed a technique for making grain boundaries, with chosen misorientations, by welding together appropriately oriented single crystal films. This technique has been used to make gold bicrystals with a misorientation which does not correspond to any short period structure of the kind which is usually thought to have low energy. The procedure followed was to join {100} and {111} single films with <110> directions in each film approximately parallel. With [110](001) and [110](111) exactly parallel an asymmetrical tilt boundary with misorientation 54.73°/[110] is produced. For Σ, the reciprocal fraction of coincidence sites <50, the periodic boundary structures nearest in misorientation are 50.48°/[l10], Σ=11; 55.88°/[110], Σ = 33. Analysis of the present boundaries can therefore give direct evidence relating to the controversial question of the extent of the physical significance of the dislocation model for grain boundaries.

Fig. 1 shows a typical region of the interface. Patches of grain boundary are surrounded by regions where the two films are not in contact.
Contrast effects at grooved interfaces
Authors: Rasmussen D.René , Simpson Yonn Kouh , Kilaas Roar , Carter C. Barry
Published: June 2020

Recent studies have shown that the characterization of the microstructure of ceramics such as polycrystalline alumina is complicated by the surface grooving of the grain boundary (thermal grooving and preferential mechanical damage produced by specimen preparation processes). Many of the TEM techniques, such as the Fresnel-fringe technique and the dark-field diffuse scattering technique, that are used to test for the presence of a glassy phase at grain boundaries do not give unambiguous results due to this grooving effect. Fig. 1 shows an example of such a grain boundary in alumina: the grain boundary has been inclined to show grooving at both surfaces, see fig. 2a. It is the aim of this investigation to study the effect of grooving on the Fresnel-fringe contrast and on high resolution images of grain boundaries by computer simulations.

The simulations were performed using the multislice program TEMPAS installed on a CONVEX computer.
Quantitative measurements of stresses at grain boundaries in polycrystalline metals
Authors: Clark W. A. T.
Published: June 2020

It has long been recognized that the deformation of polycrystalline metals proceeds by the movement of individual dislocations both within the grains and across the grain boundaries which separate them. It is known, for example, that the yield stress is directly affected by the density of grain boundaries in a metal; in the familiar Hall-Petch relationship it is inversely proportional to the grain diameter. Various models have been proposed to account for this behaviour, all of which involve the interaction between dislocations and grain boundaries (for a review see e.g. ref. 1). Microscopically, these interactions can be accomplished by several different mechanisms, which include the nucleation of new dislocations, direct transmission of dislocations across the interface, the absorption and desorption of dislocations into and out of the interface.

The TEM can be used for both static and in-situ dynamic studies of these interactions. In the static mode, a TEM is used to analyze fully the crystallography of dislocation pile-up/grain boundary interactions; one such pile-up is shown in Fig. 1.
Dissociated Σ=27 boundaries in silicon
Authors: Garg A. , Clark W.A.T. , Hirth J.P.
Published: June 2020

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.

The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.
A series of JEOL 2000 FX vacuum system upgrades to provide substantial performance improvements at modest cost
Authors: Mardinly A. J.
Published: June 2020

Since its introduction three years ago, the JEOL 2000 EX/FX series of transmission electron microscopes has been extremely popular. However, there is one aspect of the instrument that could be improved; that is the vacuum system. The factory supplied 150 l/s ion pump provides satisfactory, but not outstanding performance. Ultimate vacuum of 3x10-7 Torr could be achieved, but was difficult to maintain during operation. In addition, the conductance of the manifold limited pumping speeds at the accelerator. Evacuation times after column or gun maintenance and recovery time after specimen exchange required improvement. Finally, some specimen contamination occurred during focussed probe operation, and ice formation made cold stage work difficult.

It was decided to improve the vacuum system in a mannner which would be as non-invasive as possible to the microscope. The pumping system could be augmented, but there should be no dismantling of the microscope and any changes should be compatible with the microprocessor controlled valve system.
Calculation of knock-on sputtering cross sections
Authors: Bradley Charles R.
Published: June 2020

Electrons in a TEM can be energetic enough to remove atoms from the exit surface of a sample. The probability of a collision imparting enough energy to dislodge an atom from the surface is expressed in terms of a cross-section which depends on the nuclear charge, the atomic mass, surface binding energy, and incident electron kinetic energy. McKinley and Feshbach have given an asymptotic relation for the Mott cross-section which has been widely used in studies of this process. However the expression is accurate only for low Z, and low incident electron energies (see Figure 1). Since modem TEMs often have accelerating voltages up to 300 or 400kV and occasionally over 1MV the assumption of low incident electron energies is not valid and the restriction to low Z is prohibitive.

We have developed a program to evaluate numerically the total Mott cross-section. This program uses an algorithm like that described by Doggett and Spencer to evaluate two conditionally convergent Legendre series.
Electron microscopy in surface science
Authors: Venables J. A.
Published: June 2020

Surface science and electron microscopy are two fields of comparable size. The overlap between the two, the examination of surfaces on a microscopic scale, constitutes a small but important area of both fields. Historically, the area has grown slowly, with relatively few electron microscopy groups worldwide involved in studies of surface structure and reconstructions, small particles and surface reactions, and crystal growth. More recently, activity has intensified with substantial developments based on TEM, STEM, REM and SEM. At the same time surface science instrumentation has been developed in a micro-analytical direction; advances have been made in scanning electron and Auger microscopy, and low energy and photoemission microscopy, as described below. Such techniques, as is standard in surface science, are used in conjunction with ultrahigh vacuum (UHV) chambers, typically involving in-situ specimen preparation facilities and other diagnostic tools.
Electron-beam induced nucleation and redispersion of ruthenium on MgO supports
Authors: Datye Abhaya K. , David Logan A.
Published: June 2020

Catalysts prepared aqueously from RUCl3.3H2O on MgO supports generally have poor dispersions. This occurs because the precursor reacts with surface hydroxyl groups and tends to precipitate on the surface. The chloride precursor is not stable in basic solutions such as those encountered in dispersions of MgO powder. Tauster et al. pointed out that the use of non-aqueous preparation minimizes this problem and yields catalysts having higher dispersions. However, MgO powder that is exposed to the atmosphere can readily pick up moisture and hence the surface hydroxyl concentration is not well controlled. In order to develop a better understanding of the nucleation and growth of Ru, we have prepared catalysts supported on MgO that was dehydroxylated by calcining in air at 1200°C overnight and used immediately. All catalysts were prepared by non-aqueous impregnation using low surface area MgO cubes.
Nanometer-area diffraction of small iron crystallites in single crystalline Fe-MgO composite films
Authors: Tanaka N. , Mihama K. , Ou H. , Cowley J.M.
Published: June 2020

Nanometer-sized iron(Fe) crystallites can be prepared in a single crystalline magnesium oxide(MgO) film by a simultaneous vacuum deposition of Fe and MgO. The crystallites are grown epitaxially and almost coherently in the film, the orientation being (001) [110]Fe//(001)[100]MgOand (011) [100]Fe//(001) [100]MgO. A heat treatment of the as-grown composite films at 500-1000°C brings about a phase-transformation from α -iron(b.c.c.) to γ -iron(f.c.c.). In the present study, the phase-transformation and the structure of the γ-iron crystallites are studied by nanometer-area electron diffraction(nanodiffraction) in TEM and STEM as well as high-resolution electron microscopy.

The specimens were single crystalline Fe-MgO composite films prepared on a NaCl (001 ) surface by co-evaporation of Fe and MgO. The films were separated from the substrate in water and mounted on a perforated carbon film. Nanodiffraction in TEM was performed in a 200 kV transmission electron microscope(JEM- 2000FX)2 and that in STEM3was carried out in a 100 kV scanning transmission electron microscope (VG-HB5) equipped with a specimen-preparation chamber.