bluuebunny/crossref_metadata_2025 huggingface dataset:
Microscopic techniques leading to the discovery of endolithic plant communities in a stream ecosystem
Authors: Nunley J. , Donahoe R. , Stock M. , Ward A.
Published: June 2020

The chemical weathering of rock is generally assumed to occur primarily at the water/rock interface and to be dominated by inorganic mechanisms. A previous study aimed at using microscopic techniques to study the weathering of sandstone bedrock in a stream ecosystem suggested the operation of biotic processes inside these rocks. Examination of rock samples by a variety of microscopic techniques led to the discovery of endolithic plant communities. Endolithic microbial communities are known to exist in hot and cold desert, freshwater, and marine environments, occurring in a variety of bedrock types. However, endolithic organisms have not been previously documented in stream ecosystems.
Artifacts caused by dehydration and epoxy embedding in TEM
Authors: Mollenhauer Hilton H.
Published: June 2020

Various means have been devised to preserve biological specimens for electron microscopy, the most common being chemical fixation followed by dehydration and resin impregnation. It is intuitive, and has been amply demonstrated, that these manipulations lead to aberrations of many tissue elements. This report deals with three parts of this problem: specimen dehydration, epoxy embedding resins, and electron beam-specimen interactions. However, because of limited space, only a few points can be summarized.

Dehydration: Tissue damage, or at least some molecular transitions within the tissue, must occur during passage of a cell or tissue to a nonaqueous state. Most obvious, perhaps, is a loss of lipid, both that which is in the form of storage vesicles and that associated with tissue elements, particularly membranes. Loss of water during dehydration may also lead to tissue shrinkage of 5-70% (volume change) depending on the tissue and dehydrating agent.
Imaging intracellular membrane traffic and organelle dynamics using confocal microscopy
Authors: Cooper M. S.
Published: June 2020

Movements of exocytic and endocytic vesicles within cells are controlled in part by active transport along microtubules. The forces generated by microtubule-based transport are also known to strongly influence the distribution and shapes of membranous organelles, such as mitochondria and the endoplasmic reticulum. The ability to observe such dynamic interactions between cytoskeletal elements and fluorescently-labelled intracellular membranes in living cells has been improved recently by the advent of scanning laser confocal microscopy. Here we describe the use of this technique to study activities of the Golgi apparatus in living cells.

Vesicular traffic, diffusive transport and morphological dynamics within the Golgi apparatus of cultured rat hippocampal astrocytes were imaged with a Bio-Rad MRC-500 scanning laser confocal microscope. Golgi elements were labelled with NBD-ceramide, a molecule which serves as a vital stain for the trans-most cisternae of Golgi stacks. Single scans of the specimen, obtained with the laser microscope's slow scan rate (4 sec/image), were stored sequentially on an optical memory disk recorder.
Sideband imaging for sub-Å image resolution with an intermediate voltage conventional TEM
Authors: Krakow William
Published: June 2020

The impetus for achieving sub-angstrom resolution in a CTEM was put in place several years ago at Cornell University in the laboratory of Professor Benjamin Siegel. Amongst the many activities in his laboratory was the mission to retrieve and restore the information contained in HREM images by correcting the deleterious effects of the objective lens contrast transfer function. At this time, micrographs of amorphous materials such as Ge were being studied elsewhere with the premise that tilting the illumination would lead to improved resolution. This in fact led to the observation of fringe-like image features which could not be explained in terms of an amorphous material's microstructure. At this time we were able to demonstrate in Professor Siegel's laboratory that the appearance of pseudo fringe structures was an image artifact produced by spatial filtering in the electron microscope of elastically and inelastically scattered electrons.
Surface studies in UHV: Applications of High-resolution electron microscopy
Authors: McCartney M. R. , Smith David J.
Published: June 2020

The examination of surfaces requires not only that they be free of adsorbed layers but the environment of the sample must also be maintained at high vacuum so that the surfaces remain clean. The possibility of resolving surface structures with atomic resolution has provided the motivation for optimizing intermediate and high voltage electron microscopes for this particular application. Electron microscopy offers a variety of techniques which have the capability of achieving atomic level detail of surfaces including plan-view imaging, REM and profile imaging. Operation at higher voltages permits reasonable pole piece dimensions thereby providing space for in situ studies yet still compatible with high resolution. Moreover, video systems can be attached which permit observation and recording of dynamic phenomena without compromising microscope performance.
Prospects for convergent beam electron diffraction with a 200kV cold field-emission transmission electron microscope
Authors: Steeds J W , Vincent R
Published: June 2020

We review the analytical powers which will become more widely available as medium voltage (200-300kV) TEMs with facilities for CBED on a nanometre scale come onto the market. Of course, high performance cold field emission STEMs have now been in operation for about twenty years, but it is only in relatively few laboratories that special modification has permitted the performance of CBED experiments. Most notable amongst these pioneering projects is the work in Arizona by Cowley and Spence and, more recently, that in Cambridge by Rodenburg and McMullan.

There are a large number of potential advantages of a high intensity, small diameter, focussed probe. We discuss first the advantages for probes larger than the projected unit cell of the crystal under investigation. In this situation we are able to perform CBED on local regions of good crystallinity. Zone axis patterns often contain information which is very sensitive to thickness changes as small as 5nm. In conventional CBED, with a lOnm source, it is very likely that the information will be degraded by thickness averaging within the illuminated area.
Combining slow-scan CCD images to extend image size and dynamic range
Authors: Fan G.Y. , Gubbens A.J. , Krivanek O.L. , Leber M.L. , Mooney P.E.
Published: June 2020

A slow-scan CCD (SSC) camera attached to an electron microscope can record images with 4096 gray levels, nonlinearity less than ±1 %, and a detective quantum efficiency (DQE) greater than 0.5 even with just one primary electron per pixel. Moreover, the images are read out by a computer and are therefore available for further processing as soon as they are acquired. SSC cameras therefore seem destined to replace photographic film as the primary recording medium used in electron microscopy as completely as they have in top-level optical astronomy, where film is now mostly of historical interest.

However, the SSCs have two disadvantages compared to photographic film: 1) Fewer number of pixels and 2) the “spill” problem. Currently, SSCs are available for electron microscopists with a sensor array of up to 1024x1024 pixels. (2048x2048 CCD sensors have been developed but their price is high and performance, in terms of pixel defects, is low.) By comparison, a micrograph can record about 10,000x10,000 pixels. And, in order to maximize sensitivity, SSCs do not incorporate anti-blooming wells. As a result, a saturated pixel caused by, for example, a Bragg spot, will “spill” into neighboring pixels.
Defect modeling in HRTEM image simulation
Authors: Kilaas Roar
Published: June 2020

One practical problem in High Resolution Transmission Electron Microscopy (HRTEM) image simulation is the creation of atomistic models of defect structures. The ideal crystal structures are readily represented by a relatively small number of “basis” atoms and the crystallographic space group. On the other hand, the specification of a grain boundary between two crystals requires the atomic location of possibly thousands of atoms, and a HRTEM simulation program will need all this information before a calculation can be carried out. Users comfortable with writing computer code will write a computer program to generate the hundreds or thousands of atomistic locations, while others may be forced to enter the data by hand or search around for a ready made program that can generate the required data To the authors knowledge, no such suitable program is readily available. There are existing programs that will generate geometric interface models, but these programs were designed to create input to atomistic relaxation calculations, not as generalized tools for creating defect structures.
Radiation-induced segregation in austenitic stainless steels
Authors: Kenik E. A. , Hojou K.
Published: June 2020

Radiation-induced segregation (RIS) is driven by fluxes of point defects to sinks. RIS can induce composition fluctuations in irradiated stainless steels, which can result in microstructural and property changes, including precipitation, austenite instability, strengthening, embrittlement, and irradiation-assisted sensitization and stress corrosion cracking. Analytical electron microscopy (AEM) provides a powerful technique to study such segregation. RIS in several irradiated stainless steels has been investigated. AEM was performed in a Philips EM400T/FEG equipped with an EDAX 9100/70 analysis system. The specimens were neutron irradiated to 15 displacements per atom (dpa) at 520 ° C in the Fast Flux Test Facility (FFTF) and were only mildly radioactive (<50/μCi = 1.85 MBq), thus permitting high spatial resolution X-ray microanalysis to be employed. Typical acquisitions were performed for 100 s in the STEM mode with <2-nm-diam probes containing >0.5 nA current. Subtraction of “in-hole” spectra from the measured spectra corrected for both the normal “in-hole” counts and those associated with the radioactivity of the specimen.
Growth and transformation structures in tantalum films
Authors: Liu J.B. , Fisher Robert M.
Published: June 2020

Tantalum oxide, nitride and metal films are of considerable interest to the semiconductor industry because of the attractive dielectric properties of the compounds and the unusual electrical conductivity of the metallic forms. For example, β-tantalum has a relatively high resistivity of 180 u ohm/cm and a temperature coefficient of essentially zero whereas α-tantalum is superconducting below 7°K and has a room temperature resistivity of 15-40 u ohm/cm depending on method of preparation. The transformation sequence in tantalum films is unusual as the film first grows in the low density bet form. At a critical thickness, about 200 nm for glass substrates at room temperature, transformation to the higher density α-form occurs with a net volume shrinkage of about 1.5%. Substrate temperature and composition markedly affect the critical thickness for transformation to bec Ta growth. At 300 C for example, the critical thickness for glass substrates is about 30 nm. For Cu substrates it is 50 nm at room temperature and on Nb it is 0 nm(2).
Observation of a high-temperature incommensurate phase transition and discommensurations in TaTe4
Authors: Bennett J.C. , Boswell F.W. , Ritchie S. , Corbett J.M. , Prodan A.
Published: June 2020

In many ways, TaTe4 and NbTe4 are nearly prototypical compounds for the study of charge-density waves (CDW). The compounds have a quasi-one-dimensional crystal structure in which chains of metal atoms are centered within extended cages of Te atoms in square antiprismatic coordination. The observed lattice distortions, involving mainly longitudinal motions of the metal atoms along the chains, correspond to that of the classic CDW model. In addition, the compounds exhibit the full spectrum of possible CDW-driven phase transitions: commensurate-to-incommensurate (C to IC), C to C and IC to IC. The subcell of TaTe4 is tetragonal with axes (a x a x c). At room temperature, the crystal is commensurately modulated giving rise to a supercell with axes (2a x 2a x 3c) and, upon heating, has been observed to undergo a C to C transition at about 450 K. In this paper, we report an additional C to IC transition occurring above 550 K. The evolution of the microstructure upon heating, including the formation of discommensuration arrays in the IC state, has been revealed by satellite dark-field (SDF) imaging.
Decomposition of Ni-23 at.% Si and formation of Ni3Si
Authors: Baker I. , Schulson E.M.
Published: June 2020

The purpose of the paper is to outline the formation of Ni3Si from Ni-23 (at. %) Si. The Ni-23Si was annealed at 1130°C for 24 h and quenched, after which it consisted of ∼10μm particles in an otherwise single phase matrix. To produce the peritectoid transformation to Ni3Si, samples were annealed at 725°C.

Thin foils of Ni-23Si were prepared by electropolishing 250μm thick discs with 13% hydrochloric acid in methanol in a Struers Tenupol at -40°C, 40V (200 mA) and a medium flow rate. After perforation, the thin foils were rinsed in ethanol before washing in hydrofluoric acid for 30-40s. The foils were examined in a JEOL 2000FX TEM, furnished with a Tracer Northern TN5500 EDS system.
Reconstruction of the Au (001) surface
Authors: Dunn D.N. , Zhang J.P. , Marks L.D.
Published: June 2020

The Au (100) surface has been a widely studied surface producing a variety of reconstructions using several different techniques. LEED has determined the clean surface reconstruction to consist of (5x20)1 and (26x68)2 surface domains. More recently an ultra high vacuum transmission electron microscope study of small Au(001) crystallites has found a reconstructed surface with (28x5)3 slightly rotated surface unit cells. The common elements in all these studies seem to be that the ‘5’ dimension is a hard dimension and does not seem to vary from study to study save one. It is also generally accepted that this surface can be thought of as the an hexagonal layer superimposed on a bulk terminated surface. Generally the long dimension is representative of an average number taken from the analysis of many domains. We have found the Au (001) surface to reconstruct into (5xn) domains where the ‘5’ dimension is a hard dimension while the ‘n’ is a soft dimension ranging between 15 and 21.
Applications of electron holography to interference microscopy
Authors: Tonomura Akira
Published: June 2020

Electron-holographic interference microscopy, which provides an image of the phase distribution of an electron wave transmitted through a specimen, has become practical with the development of a field-emission electron microscope. This instrument, increasing the brightness of the electron beam by more than two orders of magnitude, allows biprism interference fringes to be directly observed on a fluorescent screen. The coherence of this microscope's electron beam has enabled phase measurement to a precision of 1/100 of the wavelength, and it even makes dynamical observation possible.
Efforts to improve the quantification of EDX analyses, particularly for the light elements
Authors: L'Espérance G.
Published: June 2020

The attachment of a Si(Li) energy dispersive X-ray (EDX) detector to a (scanning) transmission electron microscope ((S)TEM) is widely used to carry out quantitative determinations of elemental composition of a localized region of a thin specimen. Although the principles of the technique first proposed by Cliff and Lorimer have been established for some time, there are still a large number of sources of errors. In addition, EDX analyses have been generally restricted until recently to elements with an atomic number (Z) larger than that of sodium (Z > 10) so that electron energy loss spectroscopy (EELS) was the preferred technique for the detection of light elements in an AEM. The relatively recent advent of ultra-thin window (UTW) detectors has offered an alternative (and often complementary) technique to EELS for the analysis of light elements with additional difficulties in the detection and quantification. This paper presents some results of investigations made to improve the quantification of EDX data. Particular attention is given to the detection and quantification of data from light elements on a routine and reproducible basis.
Quantitative mineral compositional analysis using digital x-ray images
Authors: Liang Long C.
Published: June 2020

Digital x-ray imaging (DXI) has been utilized to display spatial elemental distribution and to conduct quantitative elemental compositional mapping on various samples. The quantitative elemental compositional mapping technique, however, requires the use of an advanced image analysis and computer system to display elemental concentration maps. In this study, a simplified DXI technique is used to achieve two goals: (1) display elemental distribution, and (2) conduct quantitative mineral compositional analysis using stored digital x-ray maps. The analytical procedure of this technique can be easily implemented to similar instruments in any laboratory.

Quantitative analysis with the simplified DXI technique is performed using background-corrected elemental pixel intensities instead of using net x-ray counts as in a conventional electron microprobe analysis. In this study, digital x-ray mapping has been conducted using a JEOL 733 electron microprobe automated with a Tracor Northern (TN) 5500/5600 system. A TN image analysis program, IPP, was used to acquire all digital x-ray maps at an accelerating voltage of 15 kV and a beam current of 15 nA.
TEM study of thin iron oxide films deposited by pulsed-laser ablation
Authors: Anderson Ian M. , Grant Norton M. , Barry Carter C.
Published: June 2020

Iron-oxide-based compounds are of technological interest because of their unique magnetic properties. Thin films of these compounds are especially suited to applications such as magnetic recording devices. The binary Fe-O system provides a model for the study of iron-oxide-based compounds, since the multiple valence of the Fe cations permits the formation of phases having a variety of crystal structures. These structures include rock salt (wüstite, Fe1-δO), two spinels (magnetite, Fe3O4 and maghemite, γ-Fe2O3), and corundum (hematite, α-Fe2O3). The former three phases have cubic-close-packed oxygen sublattices, while the latter has a hexagonal-close-packed oxygen sublattice. The γ-Fe2O3 phase is a metastable, cation-deficient spinel, generally formed by careful low-temperature oxidation of the magnetite phase.

Thin iron oxide films have been deposited by pulsed-laser ablation onto (001)-oriented MgO single-crystal substrates. The microstructure and epitaxy of these films have been studied using transmission electron microscopy (TEM) and selected-area diffraction (SAD).
Crystallization of amorphous Si in Si/Al multilayers
Authors: Konno Toyohiko J. , Sinclair Robert
Published: June 2020

Stability of the amorphous Si (a-Si)/Al interface is an important issue from both practical and scientific points of view. Practically, this system can be found in many applications, such as solar cells, thin film transistors, and electrophotography. The normal crystallization temperature of a-Si is close to 700°C. However when in contact with a metallic element with which it forms a binary eutectic phase system, it can crystallize well below the eutectic temperature. The reason for the ease of such a reaction has still not been clarified. High-resolution transmission electron microscopy (HRTEM) is a powerful technique to study the mechanism of this behavior because of its ability to identify phases on an atomic scale. This article reports on the crystallization of a-Si observed in a Si/Al multilayer structure.
Luminescence from individual dislocations in II-VI and III-V semiconductors
Authors: Steeds J W
Published: June 2020

There is a wide range of experimental results related to dislocations in diamond, group IV, II-VI, III-V semiconducting compounds, but few of these come from isolated, well-characterized individual dislocations. We are here concerned with only those results obtained in a transmission electron microscope so that the dislocations responsible were individually imaged. The luminescence properties of the dislocations were studied by cathodoluminescence performed at low temperatures (~30K) achieved by liquid helium cooling. Both spectra and monochromatic cathodoluminescence images have been obtained, in some cases as a function of temperature.

There are two aspects of this work. One is mainly of technological significance. By understanding the luminescence properties of dislocations in epitaxial structures, future non-destructive evaluation will be enhanced. The second aim is to arrive at a good detailed understanding of the basic physics associated with carrier recombination near dislocations as revealed by local luminescence properties.
Amorphous-phase formation and initial reactions at Pt/GaAs interfaces
Authors: Ko Dae-Hong , Sinclair Robert
Published: June 2020

It is now well known that many metals form a l-2nm amorphous interdiffused layer when deposited onto clean Si surface, which grows upon annealing in some systems but crystallizes into stable, or metastable, phases in others. Such behavior can be interpreted in terms of a solid-state amorphization, driven by a negative heat of mixing of the elements with the amorphous phase produced for kinetic reasons. Some metal/compound semiconductor systems also show the same reaction behavior. Though there have been some reports, using electron diffraction, on the amorphous phase formation at metal-compound semiconductor interface upon low temperature annealing, because the expected thickness might only be several atomic layers, it is clear that high resolution transmission electron microscopy (HRTEM) is the most powerful technique to study such a phase. This article reports on the amorphous phase formation and the initial stages of reaction occuring at Pt/GaAs interfaces upon annealing with HRTEM, and this is the most direct demonstration of solid state amorphization of a metal with a compound semiconductor.
TEM investigation of hydrogen-implanted polycrystalline Si
Authors: Jones K.M. , Al-Jassim M.M. , Soport B.L.
Published: June 2020

Hydrogen implantation for passivating grain boundaries and dislocations in polycrystalline silicon solar cells was studied by TEM and HREM. Back-surface passivation is being investigated because studies have shown that front-side passivation causes serious surface damage with resultant surface recombination velocities as high as 7 x 107 cm/sec. Front-side hydrogenation also restricts solar cell fabrication processes. Since the passivation of defects must occur within the entire volume of the cell, particular emphasis was placed on the depth distribution of hydrogen. The hydrogen implantation was carried out In a Kaufman ion beam system using a beam energy of 0.5-1.5 keV and a beam current of 55 mA for 15 minutes.
A study of robust critical dimension measurement algorithm for use in differing scanning electron microscope configurations in the measurement of submicron semiconductor geometries
Authors: Reilly Terrence W. , Dawang Louis G.
Published: June 2020

Within semiconductor companies, there can be many different critical dimension (CD) measurement instruments. They could be optical, electrical, confocal laser, or scanning electron microscopes (SEM). Often times, they are not only different configurations, but different brands as well. There is a great need for a measurement algorithm that has the ability to deliver the same measurement between two machines. It is possible the development group within a semiconductor company would use an SEM with expanded capabilities when compared to the production group's SEM. If this is the case, the ability to use a measurement algorithm that is impervious to the influence different microscope designs have on the signal output used for measurement would enhance system matching. One would believe that two identical CD systems should produce nearly the same measurement. However, when two totally different systems are compared, only a robust algorithm would give good machine to machine matching of measurements.
Particle characterization of CVD tungsten metallization for 64 MBIT DRAM
Authors: Bennett-Lilley Marylyn , Fu Thomas T.H. , Yin David D. , Allen Bowling R.
Published: June 2020

Chemical Vapor Deposition (CVD) tungsten metallization is used to increase VLSI device performance due to its low resistivity, and improved reliability over other metallization schemes. Because of its conformal nature as a blanket film, CVD-W has been adapted to multiple levels of metal which increases circuit density. It has been used to fabricate 16 MBIT DRAM technology in a manufacturing environment, and is the metallization for 64 MBIT DRAM technology currently under development. In this work, we investigate some sources of contamination. One possible source of contamination is impurities in the feed tungsten hexafluoride (WF6) gas. Another is particle generation from the various reactor components. Another generation source is homogeneous particle generation of particles from the WF6 gas itself. The purpose of this work is to investigate and analyze CVD-W process-generated particles, and establish a particle characterization methodology.
Island Growth during the Crystallization of Amorphous Ge48Te52 Films
Authors: Libera M. , Chen M.
Published: June 2020

Microstructural TEM studies have been combined with temperature-dependent measurements of laser reflection and transmission to study crystallization in amorphous films of near-stoichiometric germanium telluride. The transformation proceeds by rapid growth of crystalline islands through the film thickness followed by two-dimensional growth in the film plane. Isothermal studies find an Avrami exponent of 4.5 suggesting a non-linear crystal growth rate.

75nm of Ge48Te52 was deposited by co-evaporation from separate Knudsen cells onto Si, carbon-coated mica, and glass substrates. Compositions were determined by x-ray fluorescence from films deposited on silicon.
Microstructural Evaluation of Silicon Carbide Whisker Reinforced Alumina Fabricated with Carbon-Coated Whiskers
Authors: Alexander K. B. , Becher P. F.
Published: June 2020

The presence of interfacial films at the whisker-matrix interface can significantly influence the fracture toughness of ceramic composites. The film may alter the interface debonding process though changes in either the interfacial fracture energy or the residual stress at the interface. In addition, the films may affect the whisker pullout process through the frictional sliding coefficients or the extent of mechanical interlocking of the interface due to the whisker surface topography.

Composites containing ACMC silicon carbide whiskers (SiCw) which had been coated with 5-10 nm of carbon and Tokai whiskers coated with 2 nm of carbon have been examined. High resolution electron microscopy (HREM) images of the interface were obtained with a JEOL 4000EX electron microscope. The whisker geometry used for HREM imaging is described in Reference 2. High spatial resolution (< 2-nm-diameter probe) parallel-collection electron energy loss spectroscopy (PEELS) measurements were obtained with a Philips EM400T/FEG microscope equipped with a Gatan Model 666 spectrometer.
Electron Microscopy of Silicon Nitride-Based Ceramics
Authors: Thomas Gareth
Published: June 2020

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.
The Schottky Source
Authors: Swanson L.W.
Published: June 2020

The ZrO/W(100) Schottky source is a unique field-assisted, thermionic point cathode which operates at 1800K. It rivals the W(310) cold field emission point cathode in brightness and exceeds it in terms of noise characteristics. It is ideally suited for use in low-voltage microscopy applications where high beam currents and high resolution are needed.
Application of conical-scan dark-field for imaging nanoscale filaments in Cu-Nb in situ composites
Authors: Chumbley L.S. , Laabs F.C.
Published: June 2020

In-situ composites composites are two-phase structures produced by heavy deformation of a coarse initial structure, such as a cast ingot, blended powders, or stacked sheets. After deformation the structure consists of a matrix phase and a strengthening phase, which is present in the form of extremely fine filaments or sheets depending upon the type of deformation processing method used. Several studies have been conducted using transmission electron microscopy (TEM) to measure the size and spacing of these filaments as a function of deformation and relate the results to the observed strengths. It is in these studies that conical-scan dark-field (CS-DF) has proven to be an extremely useful tool and has enabled accurate information to be obtained from thicker regions of the foils examined.
Koehler illumination advantages for imaging in TEM
Authors: Probst W. , Bauer R. , Benner G. , Lehman J. L.
Published: June 2020

The Koehler principle of correct illumination in the light microscope was described about 100 years ago by A. Koehler. It is used in most of todays upper class light microscopes in order to achieve optimal imaging conditiones. Basically, in light microscopy (LM) and electron microscopy (EM) the same optical principles are used in order to describe or design beam paths in the different types of instruments. Mainly due to technical reasons up to now it was, however, not possible to transfer all the advantageous optical experience from LM to EM. The EM 910 from Carl Zeiss is now the first TEM providing the benefits of Koehler illumination.

The Koehler principle is the most favourable design of the illumination beam path of a microscope as an imaging beam path for the source. In the first step the light source (LM) or the electron beam crossover (TEM) is imaged into the front focal plane of the condenser lens (LM) or the objective-prefield lens (TEM), respectively.
Effects of surface treatments on changes in low-voltage SEM of polymers
Authors: Chang J. , Krause S. , Adams W.
Published: June 2020

The effects of surface treatment of polymers is important in many areas of technology. Polymer surfaces may be treated for a variety of reasons including: increased wettability for printing; improved fiber bonding in composites; and improved bonding in powder sintering. A variety of techniques are used to study surface changes after treatments including hydrophobicity, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Another technique which has good potential for surface characterization is the effect of surface treatment on the crossover voltage, “E2,” in low voltage SEM. E2 is the accelerating voltage at which there is 0 potential on surface of an insulator because the electron emission current is equal to the primary beam current. We have previously demonstrated that changes in E2 are correlated to changes in hydrophobicity. These results also correlated well with XPS and weight loss measurements. In this research we are reporting on the effects of surface roughness, chemical treatment and electrical discharges on changes in E2 for teflon (polytetrafluoroethylene).
Application of high-resolution low-voltage SEM to the study of high-performance polymers
Authors: Adams W.W. , Vezie D.L.
Published: June 2020

Low-voltage, high-resolution (LVHR) scanning electron microscopy (SEM) of polymers is becoming more widespread as the new LVHRSEMs become more available to the general microscopy public. Although low-voltage SEM has been known for many years, the availability of new high-resolution microscopes with high-brightness field emission electron guns (FEG) and lens systems optimized for lower operating voltages (especially the immersion lens designs) has revolutionized the field of polymer surface morphology. The adequate beam current and excellent resolution at low voltages (4.0 nm at 1.0 keV) results in a dramatic improvement in image contrast at low voltages due to reduced beam spread and smaller interaction volume. In addition, imaging can be performed near the E2 crossover voltage, which means there is little or no sample charging, necessitating little or no sample coating with conducting metals or carbon, thus simplifying sample preparation.
EDS analysis of bromine in polymers
Authors: Price C. W. , Lindsey E. F. , Letts S. A.
Published: June 2020

Design requirements for the Inertial Confinement Fusion program at LLNL frequently require polymers to be modified with known amounts of dopants without seriously degrading the surface finish. Techniques such as x-ray fluorescence permit reliable quantitative analyses of the dopants. However, our strong emphasis on surface finish requires frequent SEM examinations, and the need for rapid analyses instigated an evaluation of EDS to analyze bromine in the SEM. Brominated polymers based on polystyrene and a plasma-deposited hydrocarbon with a composition of approximately CH were analyzed. Since standard ZAF programs are not effective for hydrocarbon-based materials, calibration curves were generated by correlating Br Lα/C Kα peak ratios with known compositions. The ratio technique was selected because it was highly sensitive to bromine and provided an effective internal standard based on carbon. The analyses were performed using a thin window in a NORAN Micro-Z II Si(Li) EDS on a Hitachi S-800 FESEM. The specimens were coated with palladium.
Secondary-electron yield measurements of conducting polymers in the Scanning electron microscope
Authors: Susczynsky D. M. , Klavetter F. I.
Published: June 2020

In recent years, research on conducting polymers has been motivated to a large extent by the prospect of developing low-cost, light-weight conducting polymeric materials for commercial use. Conducting polymers have potential uses as electrodes and/or electrolytes for rechargeable batteries, as power conductors andpowercable sheathing and as material for space photovoltaics and spacecraft-charging applications.

The utilization of conducting polymers for spacecraft construction and instrumentation requires an understanding of how such materials respond to the spacecraft environment. Of particular importance is how and to what degree such a material will charge when exposed to the wide range of energetic fluxes of electrons and protons that characterize a typical satellite environment. For typical space plasma environments, the total charging current to a satellite is given by the net sum of the electron and proton particle currents from the ambient plasma to the satellite, the secondary-electron and backscatter-electron emission currents arising from ambient-particle impact, and the photoelectron emission current resulting from solar UV.
Dark-field imaging of ultrathin films of YBa2Cu3O7-δ grown on MgO
Authors: Streiffer S.K.
Published: June 2020

The study of very thin (<15 nm) YBa2Cu3O7-δ (YBCO) films is necessary both for investigating the nucleation and growth of this material and for achieving a better understanding of multilayer structures incorporating such thin YBCO regions. We have used dark-field transmission electron microscopy to examine the structure of ultrathin films grown on MgO substrates by single-target, off-axis magnetron sputtering; details of the deposition process have been reported elsewhere, Briefly, polished, [001]-oriented, single crystal MgO substrates were attached to a block placed at 90° to the sputtering target and heated to 670 °C. The sputtering was performed in 40 mtorr oxygen and 170 mtorr argon with an rf power of 125 watts. Films were grown to a nominal thickness of one unit cell, or 1.2 nm. After deposition, the chamber was vented to 500 torr oxygen and allowed to cool to room temperature.
Segregation in Fe substituted YBa2Cu3O7 films
Authors: Ponce F. A. , Boyce J. C. , Bridges F. , Tramontana J. C.
Published: June 2020

Understanding of the role played by the Cu(2)-O and the Cu(1)-O chains is crucial in the high Tc material YBa2Cu3O7 (YBCO). One approach has been to substitute other atoms such as Co, Fe, Ni and Zn for some of the Cu. A linear decrease in the Tc has been observed for several dopants, in particular for Fe substituted bulk samples, Tc⟶0 at 14-15%. Bulk sample studies show some variation in the amount of Tc suppression with concentration, possibly related to the method of materials preparation. The materials discussed here were prepared using the laser ablation technique. Successive ablations from a series of targets was used in order to achieve in principle a mixing on an atomic scale as the components are deposited about an atomic layer at a time. An XeCl laser deposition system was used, equiped with a computer controlled rotating target holder enclosed in a water-cooled shroud.
Structure of high-angle-tilt boundaries in YBa2Cu3-O7-x thin films
Authors: Shin D. H. , Silcox J. , Russek S. E. , Lathrop D. K. , Moeckly B. H. , Buhrman R. A.
Published: June 2020

It has been known that high angle tilt grain boundaries in c-axis oriented YBa2Cu3O7-x thin films cause weak link behavior in the transport properties reducing Jc's by several orders of magnitude. These grain boundaries have been shown to be clean both structurally and chemically by high resolution imaging and microanalysis studies. Therefore the mechanism of weak link behavior in thin film YBa2Cu3O7-x is not yet understood.

Recently it has been deduced from the behavior of weak link Jc under small magnetic fields that the high angle tilt boundaries are nonuniform, consisting of several regions of good contact, each about 5-10 % of the boundary length, with the rest of the boundary region being poor. This seems to suggest that the superconducting properties at the boundary may be sensitive to changes in structures of atomic scale, since typical grain boundaries are free of macroscopic (≥ 10 Å) defects all along the boundaries.
Electron diffraction contrast of fluxons
Authors: Qin L.C. , Marks L.D.
Published: June 2020

Partial penetration of an applied external magnetic field occurs in type-II superconductors. The properties of magnetic fluxons are important in determining the critical current density of type-II superconductors as it is the mobility of the fluxon lattice that limits the high value of critical current density of superconductors. There have been various experimental techniques in use to study the fluxons, e.g. the decoration technique, neutron diffraction, electron holography and scanning tunneling microscopy.

Noting that in the thin crystal case the magnetic fluxes have a tangential component which deflects incident electrons, we explore the possibility of using conventional electron diffraction contrast technique to observe the fluxons. This is accomplished by using the London model for the vortex in thin crystals and the classical electromagnetic theory based on Maxwell equations to construct the magnetic field of a fluxon.
On the recrystallization of electrodeposited zinc during mechanical polishing to electron transparency
Authors: Giannuzzi L. A. , Howell P. R. , Pickering H. W. , Bitler W. R.
Published: June 2020

A primary concern involving transmission electron microscopy (TEM) analysis is whether the electron transparent region under investigation is representative of the bulk material. TEM is frequently employed to examine the microstructure of electrodeposited materials due to their small grain size and high dislocation density. Previous work in this laboratory on palladium electrodeposits has shown that deformation twins and diffusion induced recrystallization may be induced during preparation of thin foils using both twin jet electropolishing and ion beam thinning. Recent developments in TEM sample preparation in the physical sciences include a procedure for the cross-section of heterogeneous layered materials which reduces or eliminates the need for ion milling. In this sample preparation technique, a tripod polisher device is used to mechanically polish the specimen to electron transparency. The purpose of this paper is to report on the influence of the tripod polisher sample preparation technique, on the microstructure of zinc electrodeposits.
TEM sample preparation with focused ion beams
Authors: Kirch S. J. , Anderson Ron , Klepeis Stanley J.
Published: June 2020

The continuing reduction in the sizes of features of interest for integrated circuit failure analysis requires greater precision in transmission electron microscopy (TEM) sample preparation. With minimum feature sizes approaching 0.5 μm, the mere finding of such a feature at a polished edge, let alone preparing a TEM sample containing it becomes a formidable task. The required substantial thinning also increases the risk of loss of what may be a unique sample.

We present in this paper a technique that allows localized thinning of cross-sectional TEM samples using a focused ion beam (FIB) machine. Standard preparation techniques are used to make a cross-sectional TEM sample that would otherwise be too thick to be very useful for TEM analysis. This sample is then placed in the FIB machine, which is used as a micromachining tool. No special surface preparation is necessary and the secondary electron signal generated by the ion beam provides an image that can be used to locate the feature of interest.
Precautions toward XTEM of Si3N4/SiO2
Authors: Ogbuji Linus U.J.T.
Published: June 2020

Because of extreme differences between the mechanical properties of Si3N4, and SiO2 usual means of specimen preparation pose severe difficulties every step of the way in the XTEM of oxidized silicon nitride. Perhaps that explains the lack of TEM investigation of the report that the Si3N4/SiO2 interface is duplex. This paper highlights some of the problems encountered in that system, and the remedies employed.

The problems begin with abrasive preparation. While lapping on wheelbonded diamond removes material uniformly, diamond paste polishing does not: the fine particles lodge in the boundary of interest and destroy the oxide. Next comes dimpling. Its load focuses at a point over/near the boundary and crushes the fragile oxide. Fig. 1 shows a dimple that was aborted at 10μm depth on a foil 90μm thick. Load was 10 gm. Though offset from the boundary, the dimpling still crushed adjoining oxide.
The orientation effect on amorphization in CoTi under 1 MeV electron irradiation
Authors: Xu Genbao , Meshii M. , Okamoto P. R.
Published: June 2020

Since the first report of electron irradiation induced amorphization in 1982, this phenomenon has been characterized in many aspects. The effects of the dose and temperature, the mass of the incident beam, the deviation from stoichiometry and the electron flux, have been studied. There is, however, no systematic study has been reported on the crystallographic orientation effects. This paper will report the orientation effect on amorphization of intermetallic compound CoTi irradiated by 1 MeV electrons.

An alloy button of Co-45 at.% Ti was prepared by arc-melting and subsequently annealed at 1100°C for ten days. The HVEM samples were spark-cut from the button and then thinned by double jetpolishing in the solution of 15%HCLO4and methanol. The irradiation was carried out with fully focused 1 MeV electron beam in a high voltage electron microscope. The critical electron dose for complete amorphization and its temperature dependence have been determined for <111>, <110> and <001> orientations.
Electron-beam radiation damage to cellulose fibers in ESEM
Authors: Sheehan John G.
Published: June 2020

Of interest to the paper industry is how cellulose fibers shrink, swell, and break during wetting and drying of paper. The Environmental Scanning Electron Microscope (ESEM) is a new tool for examining wetting and drying. However, surfaces of cellulose fibers appeared smoothed in an unexpected way while examined in the ESEM (made by Electroscan, Wilmington, MA, USA) during wetting and drying. Closer examination revealed that the smoothed appearance was due to electron beam radiation damage that occurs while the fibers are wet. Shown below is evidence that damage to wet cellulose fibers is due to attack from free radicals that are products of radiolysis of ice.
Golgi Apparatus Secretion of Vacuolar Substances in Maize Root Cells
Authors: Mollenhauer H. H. , Hanson J. E.
Published: June 2020

It has long been known that secretory vesicles from the Golgi apparatus discharge their contents through the plasmalemma by a process of membrane fusion called exocytosis (2,3). Ultrastructural studies have shown that the membrane of the secretory vesicle fuses with the plasmalemma, opens up at the site of fusion, and then discharges the vesicle product to the extracellular medium (i.e., to the lumen or cell wall) (2,3). Exocytosis is recognized as a widely occurring, and possibly general, mechanism for the discharge of macromolecular secretory products (2,3). A similar mechanism is also operable for the transfer of Golgi apparatus product into the acrosome (a lysosome) of mammalian cells (4).
The Demonstration of Human Prostatic Acid Phosphatase (Pap) With Phosphorylcholine
Authors: Serrano José A. , Wasserkrug Hannah L. , Serrano Anna A. , Seligman Arnold M.
Published: June 2020

As previously reported (1, 2) phosphorylcholine (PC) is a specific substrate for prostatatic acid phosphatase (PAP) as opposed to other acid phosphatases, e.g., lysosomal acid phosphatase. The specificity of PC for PAP is due to the pentavalent nitrogen in PC, a feature that renders PC resistant to hydrolysis by all other acid phosphatases. Detailed comparative cytochemical results in rat tissues are in press. This report deals with ultracytochemical results applying the method to normal and pathological human prostate gland.

Fresh human prostate was obtained from 7 patients having transurethral resections or radical prostatectomies. The tissue was fixed in 3% glutaraldehyde- 0.1 M cacodylate buffer (pH 7.4) for 15 min, sectioned at 50 μm on a Sorvall TC-2 tissue sectioner, refixed for a total of 2 hr, and rinsed overnight in 0.1 M cacodylate buffer (pH 7.4)-7.5% sucrose.
N,N’ -Bis (4-Aminophenyl) -N,N'-Dimethylethylenediamine (BED) Oxidation In Rat Thyroid Gland
Authors: Allen Shannon W.
Published: June 2020

Ultracytochemical oxidation studies with N,N'-bis(4-aminophenyl)-N,N'-dimethylethylenediamine (BED) have been previously reported. Reaction variations related to fixation have been studied in rat liver and parotid gland. It is thought that in vitro oxidation of the compound demonstrates two different oxidative systems. They are represented by 1) mitochondrial outer compartment activity and 2) cytoplasmic membrane activity, i.e. Golgi, ER and nuclear envelope. Unlike the latter activity, the former one exhibits considerable sensitivity toward formaldehyde fixation. Further investigation with this compound in rat thyroid gland has revealed oxidative activity in mitochondrial cristae in addition to that present in the outer compartment and membranes of other organelles.