bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural observations of lung neoplasms induced in the strain A/J mouse by benzo(a)pyrene and ethylnitrosourea
Authors: Gunning W.T. , Stoner G.D. , Goldblatt P.J.
Published: June 2020

The current literature regarding the histogenesis of mouse lung adenomas suggests two alternative cells of origin for these tumors. The Type II pneumocyte was accepted by most investigators as the cell which proliferated either spontaneously or by chemical induction, until Kauffman and co-workers reported histologic and ultrastructural features of a Clara cell adenoma, and indicated that in Swiss mice, 63% of all chemically induced tumors appeared to be Clara cell derived. Ward et al. using immunocytochemical techniques have demonstrated that all lung adenomas they tested in B6C3F1, BALB, and A strain mice appear to be of alveolar cell origin. It has also been reported that up to 70% of ethylnitrosourea induced adenomas can be characterized as Clara cell based on histochemical staining for nitroblue tetrazolium reductase.

Histological investigation of lung tumors arising in Strain A/J mice from bioassays of thirteen chemicals demonstrates a variable growth pattern.
A light and electron microscopic examination of novel features of fish granulomas
Authors: Dykstra M.J. , Noga E.J.
Published: June 2020

A typical mammalian granuloma resulting from chronic inflammation is primarily composed of plasma cells, lymphocytes, macrophages, monocytes and giant cells. So-called epithelioid cells are usually found in granulomas of immunological origin and are derived from the mononuclear phagocyte series. Epithelioid cell granulomas are associated with a number of infectious diseases of man such as tuberculosis, schistosomiasis and fungal infections such as coccidioidomycosis.

Tissues from Atlantic menhaden and Tilapia fish were fixed in 10% formalin and stained with hematoxylin and eosin (H&E) for light microscopy. Replicate samples were fixed with McDowell's and Trump's fixative, embedded in Spurr's resin, sectioned, stained with uranyl acetate and lead citrate and examined with a transmission electron microscope.

Three fish granulomas were examined: 1) A granuloma of unknown origin in a menhaden spleen (Figs. 1,2); 2) A granuloma induced by fungal hyphae in a menhaden with ulcerative mycosis (Figs. 3,4); and 3) A granuloma due to mycobacteriosis in Tilapia (Figs. 5,6).
Toxic effects of inhaled DMMP on the kidneys of Fischer-344 rats
Authors: Mattie D.R. , Hixson C.J.
Published: June 2020

Dimethylmethylphosphonate (DMMP) is a simple organophosphate used industrially as a flame retardant and to lower viscosity in polyester and epoxy resins. The military considered the use of DMMP as a nerve gas simulant. Since military use of DMMP involved exposure by inhalation, there was a need for a subchronic inhalation exposure to DMMP to fully investigate its toxic potential.

Male Fischer-344 rats were exposed to 25 ppm or 250 ppm DMMP vapor on a continuous basis for 90 days. An equal number of control rats were sham-exposed. Following the 90-day continuous exposure period, 15 male rats were sacrificed from each group. Two rats from each group had the left kidney perfused for electron microscopic examination. The kidneys were perfused from a height of 150 cm water with 1% glutaraldehyde in Sorensen's 0.1M phosphate buffer pH 7.2. An additional kidney was taken from a rat in each group and fixed by immersion in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer pH 7.4. A portion of the 9 kidneys collected for electron microscopy were processed into Epon 812. Thin sections, stained with uranyl acetate and lead citrate, were examined with a JEOL 100B Transmission Electron Microscope. Microvilli height was measured on photographs of the cells of proximal tubules. This data, along with morphologic features of the cells, allows the proximal convoluted tubules (PCT) to be identified as being S1, S2, or S3 segment PCT.
Absorption edge imaging of bacterial endospores
Authors: Panessa-Warren B. J. , Tortora G. T. , Warren J. B.
Published: June 2020

Due to the structure and physiology of the bacterial endospore, the resist ratio for most chemical sterilants of spores to vegetative cells is 10,000:1 thereby making them uniquely resistant to chemical sterilization. Although some chemical sterilants do exist that are quite effective against most species of spores, little is known about the effect these chemicals have on spore morphology. This investigation involves the application of a relatively new vanadium-containing sporocide to viable Bacillus subtilis and B. Thuringiensis spores and subsequent microscopy and viability studies to analyze the changes produced after 30 sec, 5 min, 10 min 50 min and 80 min exposure. To try and identify the role, and site of action, of vanadium during spore destruction we attempted a new type of x-ray microscopy utilizing monochromatic x-rays above and below the absorption edge of vanadium (V LII edge). Control x-ray replicas were made at the nitrogen absorption edge (3.09nm) for orientation purposes due to the optimal imaging of protein within the spore. Scanning electron microscopy of sporocide-treated and untreated endospores were used for comparison.
A scanning electron microscopic study of the eggs of Culicoides variipennis (Diptera: Ceratopogonidae)
Authors: Nunamaker R. A. , Nunamaker C. E. , Wick B. C.
Published: June 2020

Culicoides variipennis (Coquillett) is probably the most economically important species of biting midge in the U.S. due to its involvement in the transmission of bluetongue (BT) disease of sheep, cattle and ruminant wildlife, and epizootic hemorrhagic disease (EHD) of deer. Proposals have been made to recognize the eastern and western populations of this insect vector as distinct species. Others recommend use of the term “variipennis complex” until such time that the necessary biosystematic studies have been made to determine the genetic nature and/or minute morphological differences within the population structure over the entire geographic range of the species. Increasingly, students of ootaxonomy are relying on scanning electron microscopy (SEM) to assess chorionic features. This study was undertaken to provide comparative chorionic data for the C. variipennis complex.

Culicoides variipennis eggs were collected from a laboratory colony maintained in Laramie, Wyoming.
The Ultrastructure of Galago senegalensis cerebellar cortex
Authors: Milliken G. , Lavallee K. , Lamoreaux W. , Rosell-Davis R. , Ward J.
Published: June 2020

The insectivorous, nocturnal prosimian, Galago senegalensis (bushbaby), relies on its arboreal running and leaping ability for survival, and extreme hand-eye coordination for prey capture. In mammals, these functions require a well developed motor system mediated by a highly evolved cerebellum. The mammalian cerebellar cortex is characterized by a three layer configuration comprised of the molecular, Purkinge, and granular layers. In this study, we examined the ultrastructure of the cerebellar cortex of the bushbaby.

A six year old male bushbaby was anesthetized with 2 cc sodium pentobarbitol injected intraperitoneally. The animal was perfused through the superior vena cava by flushing the system with saline and 2% heparin, followed by fixation with 2% glutaraldehyde for 30 min. After primary fixation, the animal was decapitated and the head placed in 2% glutaraldehyde overnight. The brain was removed and desired areas were excised from the brain, post-fixed with osmium tetroxide, dehydrated in acetone, and embedded in Epon Araldite.
Discovery of intracellular 2,8 dihydroxyadenine crystals in bovine lymphatic and hepatic cells
Authors: Rigsby W. E. , Hinton D. M. , Hurst V. J. , McCaskey P. C.
Published: June 2020

Crystalline intracellular inclusions are rarely seen in mammalian tissues and are often difficult to positively identify. Lymph node and liver tissue samples were obtained from two cows which had been rejected at the slaughter house due to the abnormal appearance of these organs in the animals. The samples were fixed in formaldehyde and some of the fixed material was embedded in paraffin. Examination of the paraffin sections with polarized light microscopy revealed the presence of numerous crystals in both hepatic and lymph tissue sections. Tissue sections were then deparaffinized in xylene, mounted, carbon coated, and examined in a Phillips 505T SEM equipped with a Tracor Northern X-ray Energy Dispersive Spectroscopy (EDS) system. Crystals were obscured by cellular components and membranes so that EDS spectra were only obtainable from whole cells. Tissue samples which had been fixed but not paraffin-embedded were dehydrated, embedded in Spurrs plastic, and sectioned.
Expression of bovine coronavirus antigens at the plasma membrane in infected cell cultures
Authors: Payne H. R.
Published: June 2020

Infection by bovine coronavirus (BCV) may cause severe diarrhea in neonatal calves. The virus can multiply in the human adenocarcinoma cell line HRT-18 and in bovine fetal spleen cells (BFS). Fusion of BFS cells occurs after BCV infection if trypsin is added to the culture medium. This type of fusion may be induced by other enveloped viruses following the expression of virally encoded macromolecules in the plasma membrane. The presence of viral proteins in the host plasma membrane is not, however, necessary for BCV maturation since coronaviral particles are enveloped by budding into intracellular compartments. Immunogold techniques were used to determine if BCV proteins are present in the plasma membrane of the host cell and whether their absence might explain the lack of fusion in BFS cells not treated with trypsin.

Monolayers of HRT-18 cells, grown in DMEM medium with 5% fetal calf serum, were infected with BCV.
Acetaminophen: Macula densa hypersecretory activity by induced hepatotoxicity
Authors: Poolsawat S.S. , Huerta C.A. , Lae S.TY. , Miranda G.A.
Published: June 2020

Introduction. Experimental induction of altered histology by chemical toxins is of particular importance if its outcome resembles histopathological phenomena. Hepatotoxic drugs and chemicals are agents that can be converted by the liver into various metabolites which consequently evoke toxic responses. Very often, these drugs are intentionally administered to resolve an illness unrelated to liver function. Because of hepatic detoxification, the resulting metabolites are suggested to be integrated into the macromolecular processes of liver function and cause an array of cellular and tissue alterations, such as increased cytoplasmic lysis, centrilobular and localized necroses, chronic inflammation and “foam cell” proliferation of the hepatic sinusoids (1-4).

Most experimentally drug-induced toxicity studies have concentrated primarily on the hepatic response, frequently overlooking other physiological phenomena which are directly related to liver function. Categorically, many studies have been short-term effect investigations which seldom have followed up the complications to other tissues and organs when the liver has failed to function normally.
Ultrastructure of yeast plasma membrane revealed by a new high-resolution freeze-replica method
Authors: Hirano Tadashi , Tanaka Akira
Published: June 2020

The Freeze-fracture morphology of the plasma membrane and surface of yeast protoplasts has been investigated by a new high resolution freeze-replica method (Tanaka et al.1978). According to freeze-fracture theory, it is generally argued that the plane of cleavage breaks down into the bilayer and then follows the plane of the membrane between the two halves of the lipid. However, when we observed thin sections of replica film of the surface of the freeze-fractured face of intact yeast cells, the single unit membrane was clearly visible between the replica film and the cytoplasm (Fig. 1). Accordingly, in the case of yeast cells, we assume that the plane of cleavage breaks down between the plasma membrane and cell wall.

On the other hand, Walzthöng et al. (1982) have shown that surface granules are an artifact or form of contamination produced under the conditions used for the ordinary freeze-replica method employing metal shadowing film.
Warm and freeze-fracture of cotton seed radicles
Authors: Vigil E. L. , Erbe E. F.
Published: June 2020

In cotton seeds the radicle has 12% moisture content which makes it possible to prepare freeze-fracture replicas without fixation or cryoprotection. For this study we have examined replicas of unfixed radicle tissue fractured at room temperature to obtain data on organelle and membrane structure.

Excised radicles from seeds of cotton (Gossyplum hirsutum L. M-8) were fractured at room temperature along the longitudinal axis. The fracture was initiated by spliting the basal end of the excised radicle with a razor. This procedure produced a fracture through the tissue along an unknown fracture plane. The warm fractured radicle halves were placed on a thin film of 100% glycerol on a flat brass cap with fracture surface up. The cap was rapidly plunged into liquid nitrogen and transferred to a freeze- etch unit. The sample was etched for 3 min at -95°C to remove any condensed water vapor and then cooled to -150°C for platinum/carbon evaporation.
Crystallization intermediates of sickle hemoglobin
Authors: Gabriel Barbra L. , Josephs Robert
Published: June 2020

Sickle hemoglobin (HbS) polymers can crystallize through different pathways determined by the solution conditions. Fibers are the first polymers to form Above pH 6.5 in 50 mM phosphate buffer (the high pH pathway), fibers form fas cicles, which consist of large arrays of fibers. The fibers in fascicles become progressively more ordered and ultimately crystallize. Below pH 6.5 (the low pH pathway), fibers form macrofibers which align and crystallize. The different intermediates are similar in being composed of double strands of HbS and in forming structurally identical crystals.

In this work, HbS polymerization near the boundary of the high and low pH pathways was investigated. The experiments were conducted over a pH range of 6.1 to 7.2 in 20 to 100 mM phosphate buffer. The solutions were periodically assayed at frequent intervals (3 to 15 min), and the structures present at each time point characterized in the electron microscope. The experiments were concluded when the HbS crystallized.
Interpretation of low-voltage field-emission projection interferograms
Authors: Spence J.C.H. , Qian W.
Published: June 2020

Remarkable transmission electron interference patterns have been reported from very thin crystals at energies Eo< 400 volts using a field emission tip, distance z1 ≈ 200 nm from a semi-transparent crystal sample, which acts as the grounded anode. As predicted, “atomic resolution” Fourier images ar observed on a screen distance z2 from the sample, with magnification z2/z1 ≈ 106at interior sample regions, confused by Fresnel fringes at edges. The same geometry is used to observe lattice images without scanning in coherent CBED patterns with overlapping orders. The interpretation of these patterns must be based on the theory of transmission LEED (TLEED), including multiple scattering. Figure 1 shows the Ewald sphere construction for 250 volt electrons along [110] gold. Image resolutio is limited to the inner reflections by the small sphere (large wavelength). TLEED computations using the Bloch-wave method of Collela are compared with the single scattering approximation in figure 2 Convergence tests show that 58 forward and backscattered beams are sufficient (Backscattered beams hop along the surface under the repulsive influence of the tip field).
Magnetic microlens focusing of electron beams
Authors: Terris B. D. , Rugar D.
Published: June 2020

Recently, field emission sources in combination with either magnetic or electrostatic microlenses have been predicted to produce electron beams with high brightness and low aberrations. The key advantage to such systems is the short focal length and thus small coefficients of spherical and chromatic aberration. In addition, by using either small apertures or extremely sharp emission sources, the emission angle can be made small and thus the effect of the aberrations reduced further. We present here our initial results on building a magnetic microlens system. The unique feature of this work is the use of permanent magnets as the sole focusing elements in the lens, resulting in an extremely simple and inexpensive system.

It has been shown that the aberrations in a focused electron beam can be reduced by selectively scaling the column dimensions. The focused spot sized is limited by the spherical aberrations,

and the chromatic aberrations
Holographic contrast transfer theory
Authors: Plass R. , Marks L. D.
Published: June 2020

With the advent of reliable cold field emission transmission electron microscopes there is substantial interest in using the amplitude and phase information recorded in electron holograms to optically or numerically correct for the coherent aberrations of transmission electron microscopes. However electron holography cannot compensate for incoherent aberrations. The derivation of the contrast transfer function for off axis electron holography in this paper shows there is no fundamental improvement in resolution for electron holography over conventional transmission electron microscopy.

Evaluating the contrast transfer function involves mathematically following an electron beam through a field emission electron microscope set up for off axis electron holography. Due to the high coherence of the field emission electron beam coherent aberrations caused by the pre-specimen beam focusing system must be accounted for. Starting with a spacial frequency distribution, C(v), for the electron beam leaving the gun, the electron beam is limited by the condenser aperture and coherently aberrated by the condenser lens and objective pre-field as it passes to the specimen region:
Architecture of butterfly scales: Pattern formation by single cells
Authors: Ghiradella Helen
Published: June 2020

Scales, the fine “dust” that covers the wings and bodies of butterflies and moths, are extremely complex in form. Like the wings and the rest of the exoskeleton they are made of non-living cuticle. Each is the product of a single cell and as such represents pattern formation on a microscopic level, all the more remarkable in view of the great variety in forms that scales may take.

On the wing, the scales are usually arranged in rows of alternating long cover scales and shorter ground scales (Figure 1). The ground scales are usually unspecialized and show typical scale architecture: each is essentially a flattened sac whose lower lamina (the surface hidden from view) is smooth and featureless, while the visible upper lamina is elaborated into a gridwork of parallel longitudinal ridges joined at intervals by transverse crossribs (Figure 2). Ridges and ribs together frame rows of windows that open into the interior of the scale. The interior is usually empty except for pillar-like trabeculae which join the upper and lower laminae.
Biomineralization:New directions in crystal science
Authors: Heywood Brigid R
Published: June 2020

The development of effective protocols for the reproducible control of crystal structure, size and morphology is attracting considerable interest given the requirement for particles of modal size and shape in many areas of materials fabrication and the importance of crystallochemical selectivity in determining the exploitable properties (eg. optical, magnetic, electrokinetic) of inorganic solids. In biological systems their are many examples of advanced “crystal engineering” in which inorganic solids are deposited in a highly controlled manner to produce mineral phases that are unique with respect to their structure, habit, and uniformity of size (Figures 1 & 2). The crystallochemical specificity of such biogenic solids (eg. calcium phosphates, calcium carbonates, iron oxides, barium and strontium sulphates) is tailored to a wide variety of both structural (eg. bones and teeth) and non-structural roles. Examples of the latter include pH homeostasis, the transduction of magnetic signals and inertial detection.

A review of biomineralization will show that while a complex array of strategies have evolved for regulating the formation of crystalline phases, one feature is common to the continuum of mechanisms; interactions between organized biopolymeric assemblies and the nascent inorganic solids play a fundamental role in controlling the deposition of the biomineral.
Application of the Omega spectrometer TEM
Authors: Lehman J. L. , Mayer J. , Probst W.
Published: June 2020

The recent development of an analytical TEM with an integrated imaging Omega spectrometer has opened the door to a new world of specimen information. The Omega Spectrometer eliminates some of the information limits which have been imposed by the chromatic aberration effects in thick 3-D specimen imaging, as well as thermal diffuse and inelastic scattering in electron diffraction studies. This benefits both the TEM 3-D imaging and electron diffraction fields.

Inelastically scattered electrons are electrons which have lost some of their energy while passing through the specimen. In all conventional TEMs, these inelastically scattered electrons inherently cause the final image to be blurry as the objective lens focuses the different energies into different image planes. The chromatic aberration of the objective lens can be calculated by the simple equation, Δc = Cc.α.ΔE/E, where ΔE is the energy spread of the electrons leaving the specimen, and E is the energy of the electrons entering the specimen. The chromatic aberration of the objective lens can be reduced by increasing the value of E or limiting ΔE.
The ultrastructure of fibrin prepared from fibrinogen ASAHI (γ 310 met→thr) and fibrinogen morioka (γ 275 arg→cys)
Authors: DiOrio J.P. , Siebenlist K.R. , Terukina S. , Yamazumi K. , Matsuda M. , Mosesson M.W.
Published: June 2020

Fibrinogen is composed of three pairs of polypeptide chains, termed Aα, Bβ and γ, respectively, covalently linked at their amino termini by disulfide bonds. Fibrinogen is proteolytically activated to fibrin monomer by thrombin which cleaves two A (FPA) and two B (FPB) fibrinopeptides from the respective N-termini of Aα, Bβ chains, each exposing a different type of polymerization site [“A” or “B”]. Exposure of either site leads to fibrin monomer assembly to form two-stranded fibrils with subsequent lateral fibril association to a branched three-dimensional fiber network. Fibrinogen Asahi is a congenital fibrinogen variant [γ310 Met → Thr] characterized by posttraumatic bleeding, a prolonged thrombin time, and abnormal fibrin polymerization. Asn at γ308 on the variant γ chain is glycosylated due to formation of a consensus sequence for glycosylation [Asn-Gly-Thr] that is created by the γ 310 Thr substitution. Fibrinogen Morioka is another congenital fibrinogen variant [γ 275 Arg→Cys] also characterized by defective fibrin polymerization.
Evaluation of the biocompatibility of polymer surface modifications with the corneal endothelium
Authors: Citron R. , Tunberg B. , Yamada A.
Published: June 2020

Early studies of the interactions of intraocular lens (IOL) implant materials with corneal endothelial cells showed that momentary contact during surgery could result in permanent damage to these cells. It was also demonstrated that this damage could be prevented by providing a protective barrier between the intraocular lens substrate and the endothelium. This barrier might be in the form of a permanent or dissolvable coating, or introduction of a hydrophilic viscoelastic to the anterior chamber of the eye prior to implantation. It is desirable to examine this effect in vitro when developing new IOL materials or surface modifications. The technique developed for this purpose provides an improvement over previous methods, in that momentary contact and the forces involved are computer controlled for consistency, and image analysis may be used in quantifying the amount of damage.

The computer controlled test instrument designed and built at IOLAB brings the test material and a rabbit eye corneal endothelial surface into contact with a specified load, time, and stage speed.
Dental porcelain repair: a scanning electron microscopy study
Authors: Perdigao Jorge , Suliman Abdul-Haq , Swift Edward
Published: June 2020

Due to its lasting esthetic results, the use of percelain has been increasing in Dentistry. Porcelain has two main disadvantages: it is vulnerable to shear stresses and is difficult to repair. When fractures occur, they must be repaired intraorally. Since it is not feasible to repair porcelain with the same material, a bonding system is needed for effective repair, using resin composites. Several techniques have been advocated to create microporosities on the porcelain surface, allowing the formation of a mechanical interlocking with a resin material: roughening with a diamond bur, intraoral sandblasting, and acid-etching with hydrofluoric acid (HF). A silane has been used as a coupling agent between polymers and inorganic substances for the last 40 years. It was introduced as a dental material in the early 60's.

The purpose of this project was to evaluate the effect of four different porcelain surface topographies treated with four different bonding systems, on the morphology and bond strengths of porcelain bonded to a hybrid resin composite (AP H).
Atomic force microscopy (AFM) of the topography of silicon surfaces exposed to ion beams
Authors: Denker Mark , Wall Jennifer , Ray Mark , Linton Richard
Published: June 2020

Reactive ion beams such as O2+and Cs+are used in Secondary Ion Mass Spectrometry (SIMS) to analyze solids for trace impurities. Primary beam properties such as energy, dose, and incidence angle can be systematically varied to optimize depth resolution versus sensitivity tradeoffs for a given SIMS depth profiling application. However, it is generally observed that the sputtering process causes surface roughening, typically represented by nanometer-sized features such as cones, pits, pyramids, and ripples. A roughened surface will degrade the depth resolution of the SIMS data. The purpose of this study is to examine the relationship of the roughness of the surface to the primary ion beam energy, dose, and incidence angle. AFM offers the ability to quantitatively probe this surface roughness. For the initial investigations, the sample chosen was <100> silicon, and the ion beam was O2+.

Work to date by other researchers typically employed Scanning Tunneling Microscopy (STM) to probe the surface topography.
Biological applications of atomic-force microscopy
Authors: Yang Jie , Somlyo Avril V. , Reedy Michael K. , Takeyasu Kunio , Tamm Lukas K. , Allietta Margaretta , Tillack Thomas W. , Shao Zhifeng
Published: June 2020

Atomic force microscopy (AFM) has been successfully applied to image many biological specimens such as proteins, DNA molecules, membrane fragments, synthetic lipid bilayers and monolayers and even whole cells, with a resolution ranging from hundreds of nm to sub-nm. In particular, AFM has a unique capability of operating in solutions; thus, proteins in situ can be directly imaged to study their functional relationships to the structure. Because in AFM, the contrast reflects direct force interactions between the probe and the specimen surface, the resolution of AFM images is highly dependent on the specimen being studied. We, and others, found that atomic resolution images on hard crystal surfaces are among the easiest to be obtained in AFM. For example, periodic surface atomic structures with hexagonal, rhombohedral, and cubic lattices were clearly resolved by AFM [9-12]. Using the NanoScope II AFM with various home-made accessories, such as motion stages and fluid cells, we have studied several different biological materials with a resolution from tens of nm to subnm.
Convergent-beam electron diffraction at high spatial resolution
Authors: Steeds J W
Published: June 2020

That the techniques of convergent beam electron diffraction (CBED) are now widely practised is evident, both from the way in which they feature in the sale of new transmission electron microscopes (TEMs) and from the frequency with which the results appear in the literature: new phases of high temperature superconductors is a case in point. The arrival of a new generation of TEMs operating with coherent sources at 200-300kV opens up a number of new possibilities.

First, there is the possibility of quantitative work of very high accuracy. The small probe will essentially eliminate thickness or orientation averaging and this, together with efficient energy filtering by a doubly-dispersive electron energy loss spectrometer, will yield results of unsurpassed quality. The Bloch wave formulation of electron diffraction has proved itself an effective and efficient method of interpreting the data. The treatment of absorption in these calculations has recently been improved with the result that <100> HOLZ polarity determinations can now be performed on III-V and II-VI semiconductors.
Lattice defect identification using convergent-beam electron diffraction
Authors: Tanaka Michiyoshi , Terauchi Masami , Kaneyama Tohsikatsu
Published: June 2020

Electron microscopy has made a great success in the identification of lattice defects. Convergent-beam electron diffraction (CBED) also allows us to identify them and CBED gives more information about lattice defects than the electron- microscope-image method. Lattice defects are divided into two basic types. One causes a phase shift at the defect and the other an angular change. The stacking fault is a typical example of the former type and the coherent twin boundary, of the latter type. The dislocation can be treated as an extension of the former type. CBED can determine the displacement vector of a stacking fault, the Burgers vector of a dislocation and the orientation difference at a coherent twin boundary reliably and easily. We will explain the methods to determine them using examples. STACKING FAULTS : Rocking curves obtained from a stacking fault are different from those of a perfect region in a manner characteristic of the displacement between two crystals at the fault.
Grain boundary segregation in metals
Authors: Briant C.L.
Published: June 2020

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.

One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.
Measurement of segregation at interfaces by AEM
Authors: Garratt-Reed Anthony J.
Published: June 2020

Many material properties are determined by the segregation (or lack of it!) of atoms of trace elements to boundaries, including, for example, the strength, electrical conductivity, dielectric constant, and diffusion properties. Many scientists are therefore interested in measurements of the segregation, and have found the field-emission scanning transmission electron microscope to be an invaluable tool.

There are two cases to be differentiated. In the first, typified by sensitization in stainless steels, the width of the segregation or depletion zone is large compared with the diameter of the electron probe and the beam broadening. In the second, the reverse is true, the beam diameter and/or the beam broadening is large compared with the extent of the segregation. While the first case is certainly of interest, this paper will be concerned solely with the second.

The earliest attempts at detecting grain boundary segregation by AEM were made by Doig et. al., studying tin segregation in iron alloys in a 100kV microscope with a tungsten-hairpin electron gun.
Annular dark-held images of crystals
Authors: Silcox John , Hillyard Sean , Loane Russell F.
Published: June 2020

The demonstration of Z-contrast atom structure images and high spatial resolution using annular dark field STEM has drawn considerable interest. This approach is well suited for quantitative image and diffraction pattern acquisition. It has thus proven possible to use experimental data to validate calculations of convergent beam electron diffraction (CBED) patterns in silicon and ADF STEM images of (100) InP. Such simulations can then be extended, as reported here, to explore the dependence of images on factors such as thickness.

Energy filtered CBED patterns over an angular range of over 150 mrads and covering a range of over four orders of magnitude in intensity from silicon were recorded with a VG HB501A STEM for thicknesses of 217Å, 326Å and 543Å. Simulation using a “frozen phonon” approximation successfully modeled this data provided an accurate phonon amplitude was used. A similar quantitative study for images has been carried out for (100) oriented InP.
Experiences with HPGe EDS detectors on a philips EM430 and a JEOL 6300F FESEM
Authors: Griffin Brendon J. , Johnson Andrew W.S.
Published: June 2020

A turreted 10mm2 HPGe Link EDS detector has been mounted on a JEOL 6300F field emission SEM and the performance compared to that of a Si(Li) Link detector on a JEOL 6400 conventional SEM with identical geometry and construction.

A second HPGe Link EDS detector has been mounted on a Philips EM430.The detector is 30 mms. sq.in area,with a type LZ5 ultra thin window and is mechanically configured to retract behind a gate valve and in addition, has a pneumatically operated shutter to provide a rapid protection from excessive electron and x-ray doses.

Both detectors were shipped 'wet' from the factory and appeared to be contaminated by ice when initially tested on the columns. The FESEM detector was de-iced after two conditioning events and achieved an on-column resolution at Mn Kα of 115ev which matched the factory performance. Principal changes to spectra through the de-icing were improvement of resolution, decrease of dead time, reduction of oxygen Kα peak and improvement in copper Lα : Kα peak ratio. The EM430 detector has been more problematical.
Peak-to-background measurements on a 300-kV TEM/STEM
Authors: Zemyan S. M. , Williams D. B.
Published: June 2020

As has been reported elsewhere, a thin evaporated Cr film can be used to monitor the x-ray peak to background ratio (P/B) in an analytical electron microscope. Presented here are the results of P/B measurements for the Cr Ka line on a Philips EM430 TEM/STEM, with Link Si(Li) and intrinsic Ge (IG) x-ray detectors. The goal of the study was to determine the best conditions for x-ray microanalysis.

We used the Fiori P/B definition, in which P/B is the ratio of the total peak integral to the average background in a 10 eV channel beneath the peak. Peak and background integrals were determined by the window method, using a peak window from 5.0 to 5.7 keV about Cr Kα, and background windows from 4.1 to 4.8 keV and 6.3 to 7.0 keV.
Elemental analysis of telatively thick specimens by EELS
Authors: Egerton R.F. , Cheng S.C.
Published: June 2020

Core-loss spectra of thicker specimens are strongly influenced by plural scattering. Plural inelastic events increase the background Ibunderneath an ionization edge by an amount dependent on t/λ, t being the specimen thickness and λ the total-inelastic mean free path. However, plural scattering also contributes to the integral core-loss signal Ic. In fact, if the latter were integrated over a sufficiently large energy window Δ, the signal/background ratio (SBR=IC/Ib) might be expected to be independent of t.

Figure 1 shows K-edge signal/background ratios for elemental carbon and silicon, presented as measured data points (for a collection semi-angle of l0mrad, 120keV incident energy and Δ=100eV) and as solid curves calculated by convolving a power-law edge profile with a delta-function approximation of the low-loss region. For silicon, SBR falls off more slowly with increasing t/λ, as expected from its higher edge energy. This trend is confirmed by measurements on amorphous silicon dioxide depicted in Fig.2, which shows the signal/background ratios of the oxygen and silicon K-edges as a function of thickness.
High-resolution topographic SEM and radiation damage: The rationale for using low beam voltage
Authors: Pawley James , Joy David
Published: June 2020

The scanning electron microscope (SEM) builds up an image by sampling contiguous sub-volumes near the surface of the specimen. A fine electron beam selectively excites each sub-volume and then the intensity of some resulting signal is measured and then plotted as a corresponding intensity in an image. The spatial resolution of such an image is limited by at least three factors. Two of these determine the size of the interaction volume: the size of the electron probe and the extent to which detectable signal is excited from locations remote from the beam impact area. A third limitation emerges from the fact that the probing beam is composed of a number of discrete particles and therefore that the accuracy with which any detectable signal can be measured is limited by Poisson statistics applied to this number (or to the number of events actually detected if this is smaller). As in all imaging techniques, the limiting signal contrast required to recognize a morphological structure is constrained by this statistical consideration. The only way to overcome this limit is to increase either the contrast of the measured signal or the number of beam/specimen interactions detected. Unfortunately, these interactions deposit ionizing radiation that may damage the very structure under investigation. As a result, any practical consideration of the high resolution performance of the SEM must consider not only the size of the interaction volume but also the contrast available from the signal producing the image and the radiation sensitivity of the specimen.
Effects of chamber pressure and accelerating voltage on X-RAY resolution in the ESEM
Authors: Griffin Brendon J.
Published: June 2020

Chamber pressure, accelerating voltage and working distance have been shown to control the relative diameter of the scattered skirt of the primary electron beam at the specimen surface in the ESEM. Inital x-ray studies indicate that at 3 torr, 30 kV and a WD=15mm, 45% of the beam comes from beyond 25 μm of the incidence point and 4% from beyond 1.5mm. At 5 torr 66% of the beam is scattered beyond 25 μm2. No specific data was available on the spatial resolution of x rays and this study aimed to improve that situation. The results also form the basis for establishing a mechanism for and defining the potential limits of quantitative EDS microanalysis in the ESEM.

The negative viewing angle of the EDS x-ray detector in the current ESEM (model E-3) requires at least a 15 degree tilt on a flat sample for microanalysis. This geometry places a narrow limit on the working distance range that can be used, due to the collimation of the detector, thereby effectively eliminating working distance as a variable in x-ray microanalysis.
SEM evaluation of pharmaceutical inhalation aerosols deposited in an andersen cascade impactor
Authors: Angel A. , Robson J. , Muchnick T.L. , Moretz R.C. , Patel R.B.
Published: June 2020

Particle size characterization is a critical parameter used for inhalation aerosol formulation development, batch control and product performance evaluation. Both the United States Pharmacopeia optical microscopy method and multistage cascade impaction methods are used for particle size evaluation and control of inhalation aerosols. Particle size determination based on aerodynamic properties is considered more relevant than other techniques for assessing product performance during patient-use. The cascade impaction technique for evaluation of inhalation aerosols is typically used with a suitable inlet to facilitate introduction of the aerosol spray into the impactor. The drug particles deposited on the impaction stages are extracted and analyzed by an appropriate method to relate drug mass to the aerodynamic cut-off size and thereby determine respirable fractions (particles of < 5.8 μm aerodynamic size). This approach does not provide information relating to the physical character of the formulation (aggregates, agglomerates, particle shapes and morphology) or its deposition characteristics both within and between stages.
In situ TEM studies of the effect of misfit strain on the kinetics of sil-xgex solid phase epitaxy: temperature calibration & surface effects
Authors: Paine David C. , Howard David J. , Evans N.D.
Published: June 2020

While in situ TEM studies have proven useful for the direct observation of solid-state reaction mechanisms, such studies rarely provide quantitative kinetic data. This limitation is due to problems associated with the accurate measurement of local sample temperature, assessment of beam heating and damage, and minimization of thin-film effects. Sinclair et al. have proposed a technique for establishing the temperature of a sample during in situ TEM annealing experiments in which the wellcharacterized Si <001> solid phase epitaxy amorphous-crystalline (a/c) transformation rate is used to estimate the temperature in an adjacent (but not contiguous) region of the specimen. We have used this in situ technique to determine the activation energy for strained solid phase epitaxy of Sil-xGex (x=5.4, 11.6, and 17 at.%). The alloys were grown by CVD on <001> Si substrates to a thickness of approximately 200 nm. The entire alloy layer, and 180 nm of the underlying substrate, were amorphized with 100, followed by 200 keV 29Si implantation.
Analytical characterization of dilute cxsi1-x alloys grown by molecular beam epitaxy on si(100)
Authors: Posthill J.B. , Malta D.P. , Humphreys T.P. , Hattangady S.V. , Fountain G.G. , Rudder R.A. , Markunas R.J.
Published: June 2020

As discussed elsewhere recently, metastable CxSi1-x epitaxial alloys on Si(100) have been fabricated which may eventually find utility in Si bipolar or FET device technology where a heterobarrier or specific strain control would be desirable. Research on the metastable binary CxSi1-x system is also the logical first step toward development of the metastable ternary CxSiyGez system where the possibility of independently altering lattice parameter, strain, and band gap exists. Since the initial report of the epitaxial growth of dilute CxSi1-x alloys on Si(l00) by remote plasma-enhanced chemical vapor deposition (RPECVD), there has also been progress in this field using solid source molecular beam epitaxy (MBE); particularly in the growth of strained layer Si/CxSi1-x/Si superlattices. We report on MBE growth and characterization of CxSi1-x epitaxial alloys grown to a substantial thickness.

An MBE chamber equipped with independent e-beam evaporation of Si and graphite and a base pressure of 5×10−10 Torr was used for growth.
TEM studies of (ZnSe/FeSe) superlattices
Authors: Park K. , Salamanca-Riba L. , Jonker B. T.
Published: June 2020

Diluted magnetic semiconductors (DMS) are of considerable interest in the area of heterostructures and superlattices because the lattice parameter, energy gap, and effective mass can be “tuned” in a controlled fashion by varying the composition. This tunability has been exploited in the fabrication of DMS superlattices. Since the superlattices can be grown with a wide range of choices of materials, there is a great variety of possible applications requiring magneto-optical properties. However, the lattice mismatch between the constituent layers in the superlattice and between the superlattice and the substrate makes it difficult to grow high quality superlattices.

Superlattices of (11.4 Å FeSe/34.0 Å ZnSe)12 (sample A) and (20.0 Å FeSe/45.3 Å ZnSe)6 (sample B) were grown on (001) GaAs substrates using MBE. Sample A was grown on a ZnSe buffer layer with a thickness of 500 Å on a (001) GaAs substrate, while sample B was grown directly on a GaAs substrate. TEM samples were prepared by mechanical grinding, dimple grinding, and ion-milling (3.0 keV Ar+ ions and 1 mA current) at liquid nitrogen temperature.
Microstructures of Al(Pd, Nb) and Al(Ti) lines for VLSI
Authors: Stanis C. , Smith D. , Blauner P. , Small M.
Published: June 2020

Very Large Scale Integration necessitated an ongoing and rapid decrease in the minimum feature size which must be made on silicon devices with the aims of improving productivity and performance. Conductor lines are commonly made from Al(Cu). Widths of 1.5 μm for conductor lines are common today, submicron lines are in late stages of development and 0.25 μm lines will be needed. These dimensions present new issues since the feature size is of the same order as the grain size of the Al and other metal alloys presently used for chip wiring. In order to make on-chip wiring reliable at these dimensions it is necessary to optimise the resistance to the stresses placed on them: electromigration due to increasing current densities; thermal stresses due to differences in thermal expansivities. The kinetics of both processes are dominated by interface transport. The resistance of the metal to both stresses can be modified by alloying.
Formation of defects in implanted hipox-structures
Authors: Pegler Peter , David Theodore N. , Pan Ming
Published: June 2020

High-pressure oxidation of silicon (HIPOX) is one of various techniques used for electrical-isolation of semiconductor-devices on silicon substrates. Other techniques have included local-oxidation of silicon (LOCOS), poly-buffered LOCOS, deep-trench isolation and separation of silicon by implanted oxygen (SIMOX). Reliable use of HIPOX for device-isolation requires an understanding of the behavior of the materials and structures being used and their interactions under different processing conditions. The effect of HIPOX-related stresses in the structures is of interest because structuraldefects, if formed, could electrically degrade devices.

This investigation was performed to study the origin and behavior of defects in recessed HIPOX (RHIPOX) structures. The structures were exposed to a boron implant. Samples consisted of (i) RHlPOX'ed strip exposed to a boron implant, (ii) recessed strip prior to HIPOX, but exposed to a boron implant, (iii) test-pad prior to HIPOX, (iv) HIPOX'ed region away from R-HIPOX edge. Cross-section TEM specimens were prepared in the <110> substrate-geometry.
Microstructure of capacitor-structures exhibiting varying charge-to-breakdown
Authors: Pan Ming , Gong Sheng , David Theodore N.
Published: June 2020

The quality of oxide/silicon structures is of interest because of extensive application in capacitors and MOSFETs. Various factors can influence electrical breakdown of such structures. Breakdown can occur by enhancement of electric fields at the injecting interface due to the presence of trapped positive charges (holes), due to mobile ions, or due to interface roughness and oxide nonuniformities. In the present study, transmission electron microscopy (TEM) was used to characterize oxide/ substrate and oxide/ poly-Si interfaces in poly-Si/ oxide/ substrate-silicon structures. Electrical measurements had shown varying values of charge-to-breakdown (Qbd) for different but equivalent structures on a wafer. The purpose of this study was to investigate differences in microstructure and interfaces among the different structures.

Capacitors were fabricated on (100) p-type silicon with a 1.6μm p-type epitactic layer. A 4E12 cm−2 phosphorus implant was used for Nwell capacitors and a 3.5E12 cm− boron implant was used for Psub capacitors. Silicon-dioxide (∼175 Å) was grown on top of implanted substrates. Phosphorus-doped polysilicon (5E12 cm−2 phosphorus) was then deposited on top the oxide layers to form field plates.