bluuebunny/crossref_metadata_2025 huggingface dataset:
A microscopic marker experiment study on high temperature oxidation of Ni-Al alloy
Authors: Fan Shou-kong
Published: June 2020

Transmission and analytical electron microscopic studies of scale microstructures and microscopic marker experiments have been carried out in order to determine the transport mechanism in the oxidation of Ni-Al alloy. According to the classical theory, the oxidation of nickel takes place by transport of Ni cations across the scale forming new oxide at the scale/gas interface. Any markers deposited on the Ni surface are expected to remain at the scale/metal interface after oxidation. This investigation using TEM transverse section techniques and deposited microscopic markers shows a different result,which indicates that a considerable amount of oxygen was transported inward. This is the first time that such fine-scale markers have been coupled with high resolution characterization instruments such as TEM/STEM to provide detailed information about evolution of oxide scale microstructure.
SIMS/TEM characterization of titanium thin films
Authors: Prestipino R. M. , Furman B. K.
Published: June 2020

Thin metal films are important constituents of semiconductor devices and packages. One metal of primary interest is titanium. It is known that titanium is susceptible to absorption of hydrogen at elevated temperatures and forms hydrides that can cause embrittlement and cracking. In this study secondary ion mass spectroscopy (SIMS) was used to study the absorption of hydrogen into titanium thin films as a function of processing conditions. SIMS/ion imaging provided information on hydrogen segregation and hydride formation. Transmission electron microscopy (TEM) was used to study the microstructure of the fi1ms.
TEM observations of the structure of metal multilayers
Authors: Baxter C.S. , Stobbs W.M.
Published: June 2020

Potential explanations for the anomalous properties, such as the “supermodulus effect”, of metal multilayers include arguments based on the consequences of high coherency strains and/or the relief of these strains by interfacial dislocation arrays as well as others based on Fermi surface interactions. We have been investigating the Cu/NiPd system with the aim of distinguishing between such explanations since both the misfit and e/a ratio can be changed by altering the Ni:Pd ratio in the alloy layers. Our work has required the development of a range of TEM methods for the structural analysis of metal multilayers, and we are in general concerned that the x-ray methods normally used provide data averaged over too large a region to be unambiguous given the inhomogeneities that necessarily occur in multilayer systems.
Element analysis with the imaging electron energy loss spectrometer of the zeiss EM 902
Authors: Bihr J. , Rilk A. , Miller W.I.
Published: June 2020

An imaging electron energy loss spectrometer can be used to produce elemental maps with highest spatial resolution by Electron Spectroscopic Imaging (ESI). Simultaneously, electron energy loss spectra (EELS) can also be recorded. It is therefore simple to combine morphological examinations with the analytical method of electron energy loss spetroscopy (Figs. 2, 3)

The electron energy loss spectrometer of the EM 902, used in combination with a suitable electron detector (Fig. 1), provides the possibility of recording electron energy loss spectra over an energy loss range from 0 to 2000 eV. In this way, all elements of the periodic system can be detected via their K, L, M, N or O absorption edges (Fig. 5). Unlike X-ray microanalysis, this technique is especially suitable for detecting light and medium-heavy elements which are of special significance in biological and medical research.
Sputtering, radiation damage, and microanalysis
Authors: Zaluzec Nestor J. , Mansfield John F.
Published: June 2020

The advent of medium and high voltage electron microscopes having high brightness electron sources and ultra-high vacuum environments has been awaited with great anticipation for the last few years. There has been a particuliarly keen interest with respect to their potentials for enhanced performance in analytical and high resolution modes. Along with these positive aspects there are also the inevitable detrimental effects, the foremost of these relative to microcharacterization are electron sputtering, displacement damage and concomittent radiation induced segregation (RIS) of the various atomic species within the specimen. Previous work on this problem has concentrated upon the RIS aspects, in this study we have expanded calculations to include a comparision of electron induced sputtering.
An atomic-resolution microscope study of Al contracts on GaAs
Authors: Liliental-Weber Z. , Nelson C. , Ludeke R. , Gronsky R. , Washburn J.
Published: June 2020

The properties of metal/semiconductor interfaces have received considerable attention over the past few years, and the Al/GaAs system is of special interest because of its potential use in high-speed logic integrated optics, and microwave applications. For such materials a detailed knowledge of the geometric and electronic structure of the interface is fundamental to an understanding of the electrical properties of the contact. It is well known that the properties of Schottky contacts are established within a few atomic layers of the deposited metal. Therefore surface contamination can play a significant role. A method for fabricating contamination-free interfaces is absolutely necessary for reproducible properties, and molecularbeam epitaxy (MBE) offers such advantages for in-situ metal deposition under UHV conditions
Mark II Test Vehicle Holder for in Situ Viewing of Integrated Circuit Electr0Migrati0N
Authors: Maskowitz J. V. , Rhoden W. E. , Kitchen D. R. , Omlor R. E. , Lloyd P. F.
Published: June 2020

A patent pending test holder was designed to support research in electromigration using a JEOL 100 CX STEM. The holder provides electrical connections for an aluminum stripe test vehicle which allows the electromigration process to be conducted within the microscope.

The holder is specifically designed for use in conjunction with a JEOL-type electron microscope side entry goniometer. Four leads provide the ability to power three different test stripes on one test vehicle. This allows three separate electromigration runs/observations in-situ without removing the test vehicle from the STEM, thus minimizing test vehicle time outside the vacuum environment.
Fixation artifacts in percutaneous needle biopsies of liver
Authors: Januszewski T.C. , Harb J.M. , Komorowski R.A.
Published: June 2020

Percutaneous needle biopsy is a standard procedure for obtaining liver tissues for pathologic studies by light and electron microscopy. Tissues obtained by this procedure usually measure 1mm to 1.5 mm in diameter, and can be placed immediately at the bedside into a standard glutaraldehyde fixative for processing by the electron microscopy laboratory. Although the biopsy thickness is within the penetration range of glutaraldehyde, we have noted a significant loss of preservation in the center of most liver biopsies. The loss is apparent at light and electron microscopic levels. The purpose of this paper is to illustrate the artifact and to discuss the importance of avoiding the artifact when selecting areas of the specimen for electron microscopic studies.

Secimens studied were routine liver biopsies submitted to the electron microscopy laboratory after an initial fixation of one hour in 2.5% glutaraldehyde in 0.1M cacodylate buffer. To illustrate the artifact, one-micron thick sections of the entire block face were stained with toluidine blue for light microscopic study (Figure 1).
Platinum shadowing, complementary imaging and stereo analysis: Techniques developed for TEM can now be used to increase the resolution of frozen hydrated specimens in a SEM
Authors: Wergin William P. , Erbe Eric F.
Published: June 2020

In 1957, Steere froze virus crystals, fractured and transferred them to a vacuum evaporator where they were etched, shadowed and coated. The coating, which was then removed from the tissue and mounted on a grid, represented a replica that could be observed in the transmission electron microscope (TEM). This accomplishment is regarded as the first successful biological application of the freeze-etching technique in electron microscopy. This technique was further advanced by describing procedures whereby the replicas from both surfaces of a frozen, fractured sample could be recovered. This pair of replicas provided additional surface information by allowing one to view and compare the two opposing surfaces, or the complementary images, of a freeze-fractured biological specimen. Using a goniometer stage the replicas were also photographed, tilted and rephotographed to produce stereo pairs that could be used to analyze three-dimensionally the surface characteristics of the replica. Until recently these TEM techniques have been the principle procedures utilized by biologists to gain high resolution structural details about virus crystals, biological membranes and a wide range of other material.
A newly developed cryofixation appartus for physiological experiments and its application to squid photoreceptor cells
Authors: Ichikawa Michinori , Hanyu Yoshiro , Matsumoto Gen
Published: June 2020

By cryofixation method for electron microscopy, structural change in squid photoreceptor microvilli accompanied by long period of light illumination has been studied by Tsukita et al., resulting that there are two states of the microvillar cytoskeletal structure under dark- and light-adapted conditions. In this paper we report the structural changes as a function of time after the light pulse application and their physiological significance.

For this experiment, we have developed a new cryofixation device which can combine rapid freezing with physiological experiment2 (Fig. 1). The device cryofixes biological specimen at precisely specified time after the light illumination by driving a small silver block cooled down to 10°K with a computer-controlled actuator; that is, for cryofixation, the cooled silver block is pushed onto the specimen put on an experimental bench. Structural change in the microvilli is observed to take place for the specimens cryofixed at the time period over 50 msec after the light pulse is irradiated, but is not observed for the 20-30 msec light-illuminated photoreceptors (Fig. 2).
Improved structural preservation of high-pressure frozen cartilage
Authors: Studer Daniel , Wagner Jeannine , Hunziker Ernst B.
Published: June 2020

Adult cartilage is a unique tissue in that it is avascular and lacks innervation. The chondrocytes are embedded in an extracellular matrix which in most cases occupies 60 to 90% of the tissue volume. The ultrastructure and composition of rat growth plate cartilage has been investigated (1). It was found that during conventional chemical fixation of me tissue (2), about 60% of the extracellular matrix proteoglycans were lost (3). This artefact can be prevented if proteoglycans are precipitated by cationic dyes (eg. ruthenium hexaamine trichloride) during fixation (4) which forms relatively large precipitates by rendering high resolution imaging impossible. High pressure frozen extracellular matrix revealed a fine meshwork which was attributed to proteoglycan distribution (5). A meshwork due to segregation during freezing was not seen in recent experiments where adaequately frozen cartilage was investigated.

200μm thick sections of rat growth plate cartilage were excised in a bath of hexadecene (6). The sections were again processed under hexadecene, firstly punched (diameter 1.7mm) and then transferred to an aluminum sandwhich (corresponding in size to the sample).
Three-dimensional imaging and physiology of live neurons and glia: Confocal light and correlative high-voltage Electron Microscopy
Authors: Turner J.N. , Szarowski D.H. , Shain W. , Davis-Cox M. , Carpenter D.O. , Fejtl M.
Published: June 2020

Correlating physiologic measures with three-dimensional (3D) imaging at the light and electron microscopic levels is a powerful combination of methods for studying the structure and function of biological systems. Neurobiology is an ideal field for the application of these methods because neurons and glia have complex and extensive 3D structure, and their physiology is under intense study. Neurons, such as those studied here from Aplysia, can be more than 100 μm in diameter, and glia undergo large scale 3D shape change as a function of a number of physiologic parameters. The ability to accurately quantitate the 3D structure, volume and surface area of live neurons and glia is important to our understanding of the complex function of these cells.

Neurons were isolated from the major ganglia of juvenile Aplysia Californica and glia were obtained from long term cultures of LRM 55 cells or as primary isolates from rats. Cultures were exposed to Dil dissolved in DMSO with or without 20% Pluronic F-127 and added to the culture media. The imaging instrument was an Olympus IMT-2 and a Bio-Rad MRC-600.
Deferoxamine-induced ultrastructural lesions of nucleoli in MCF-7 carcinoma cell line
Authors: Wang Fen , Head Jonathan F. , Elliott Robert L.
Published: June 2020

Deferoxamine(DFO), an iron chelator, has been demonstrated to inhibit the growth of a variety of human malignant cell lines. Evidence suggests that DFO exerts its primary effect by chelating ferric iron and inhibiting DNA and RNA synthesis.

The effects of DFO on MCF-7 cells have been investigated. The IC50 and IC90 inhibitory concentrations of DFO on MCF-7 cells were 4.8 uM and 9.5 uM, respectively. This inhibition can be reversed by equimolar concentrations of iron and iron-loaded transferrin. Alterations in the ultrastructure of nucleoli of MCF-7 cells exposed to the DFO in the concentrations of 4.8uM and 9.5uM for 24 hours, 48 hours and 72 hours were studied by transmission electron microscopy. The cells were grown in 24 well plates in alpha-MEM supplemented with 10% FCS and incubated at 37°C. They were harvested with trypsin-EDTA, pelleted into Beem capsules and centrifuged. A standard specimen preparation procedure was employed for transmission electron microscopy.
Characterization of HF-treated Si(111) surfaces using REM, SEM, and XPS
Authors: Ma Y. , Lordi S. , Eades J. A.
Published: June 2020

The imperfections on silicon wafers have become more and more crucial as the dimensions of integrated circuits are progressively reduced in the submicron range. The problems relating to the HF acid etching of Si surfaces have recently been studied using different techniques. It has been found that Si-H bonding is responsible for the passivation of HF-treated surfaces, and the roughness of the surfaces is related to the pH value of HF acid used for etching. The roughness of those surfaces was in most cases characterized indirectly by the width of the Si-H absorption peaks in IR spectra. Only in limited cases, were they studied by STM, a direct imaging technique.

Here, we try to characterize the HF-treated Si(111) surfaces using direct imaging techniques, REM and SEM and a spectroscopy technique, XPS. The morphology of Si(111) surfaces HF-treated under different conditions was directly imaged in TEM, and SEM for comparison.
A cryo-SEM technique developed and applied to surfactant liposomes
Authors: Bhadriraju Kiran , Bellare Jayesh
Published: June 2020

Freeze-fracture replication TEM and Cryo-TEM are developed techniques for studying surfactant dispersions. Application of freeze-fracture cryo-SEM with direct imaging to such systems has the advantages of observing a greater range of particle sizes, large depth of field implying larger tilts together with rotation, and freeze-etching/freeze drying the sample while imaging it. A procedure for cryo-SEM of liquid colloids, which uses a simple sample preparation setup, and its results for liposomal dispersions, are described here.

Samples are plunge-frozen by a freezing device (Fig.l) made from a standard desoldering tool (Fig.2) used as a plunging unit. Fracture plates (Fig.3) are made from 0.1 mm thin copper sheet made adhesive to the liquid by 400 mesh TEM grids that are bent over the two edges of the plates and stuck on the non-sample side with a rubber adhesive. The sample is sandwiched between a pair of fracture plates (Fig.3) and plunged into liquid Freon-22 kept at its freezing point (-160°C) in an electrically heated cup (Fig.l) cooled by a liquid liquid nitrogen bath.
High-resolution gold labeling
Authors: Hainfeld James F. , Furuya Frederic R. , Carbone Kyra , Simon Martha , Lin Beth , Braig Kerstin , Horwich Arthur L. , Safer Daniel , Blechschmidt Bernd , Sprinzl Mathias , Ofengand James , Boublik Milas
Published: June 2020

A recently developed 1.4 nm gold cluster has been found to be useful in labeling macromolecular sites to 1-3 nm resolution. The gold compound is organically derivatized to contain a monofunctional arm for covalent linking to biomolecules. This may be used to mark a specific site on a structure, or to first label a component and then reassemble a multicomponent macromolecular complex. Two examples are given here: the chaperonin groEL and ribosomes.

Chaperonins are essential oligomeric complexes that mediate nascent polypeptide chain folding to produce active proteins. The E. coli chaperonin, groEL, has two stacked rings with a central hole ∽6 nm in diameter. The protein dihydrofolate reductase (DHFR) is a small protein that has been used in chain folding experiments, and serves as a model substrate for groEL. By labeling the DHFR with gold, its position with respect to the groEL complex can be followed. In particular, it was sought to determine if DHFR refolds on the external surface of the groEL complex, or whether it interacts in the central cavity.
Microscopic study of male Morpho rhetenor wing scales
Authors: Bingham L. , Bingham I. , Tanner J. , Driscoll C. , Geary S. , Hollingshead J. , Hansen B. , Gardner J. S.
Published: June 2020

The morphology of pigmented ventral scales and non-pigmented iridescent dorsal scales of Morpho rhetenor wings were compared using scanning electron microscopy and light microscopy. Sections of wing and individual scales were mounted at various angles on stubs for SEM evaluation. Some scales were embedded in Spurr’s resin and sectioned for LM and SEM.

Pigmented scales are ornamented by ridges parallel to the axis of the scale (Fig. 1). They are approximately 1.5 μm apart with holes through the membrane between ridges. The non-pigmented iridescent scales similarly contain a series of parallel ridges, but with several layers of lamellae (Fig. 2). The distance between these ridges is only approximately 0.7 μm (Fig. 3). Much smaller and more frequent holes can be observed between these ridges (compare Figs. 1 and 3). The overlapping layers of lamellae form stacks of thin films, which resemble a “Christmas tree” structure. The space between the overlapping lamellae is 0.05 μm and there appear to be holes through the midrib between lamellar stacks (Fig. 4).
The effect of torbafylline on capillary morphology in primate skeletal muscle after ischemic reperfusion injury
Authors: Gregory Michael A , Mars Maurice
Published: June 2020

Morphometric studies have shown that experimental drug Torbafylline (T) alters the response of skeletal myofibres to ischemic reperfusion injury (IRI). An ultrastructural study has been instituted to determine if and/or how T may “protect” the muscle from IRI. This report outlines the effect that 3 hours of tourniquet mediated ischemia and up to 24 hours of reperfusion has on the capillaries of primate skeletal muscle, with and without prior administration of T.

Sixteen adult vervet monkeys (8 control - 8 experimental) were studied under general anesthesia. In each case, a hindlimb was exsanguinated using an Esmarch bandage. To induce lower limb ischemia, a pneumatic tourniquet was applied to the thigh at 100mm Hg above systolic pressure for 3 hours. In 4 control animals, open muscle biopsies were taken from the tibilais anterior before tourniquet application (BTA), just prior to tourniquet deflation, and after 3 and 6 hours of reperfusion. In the remaining 4 animals, biopsies were taken BTA and after 12, 18 and 24 hours of reperfusion.
Scanning electron microscopy evaluation of heat cured composite resin after surface preparation to enhance bond strength
Authors: Imamura Glen M. , Reinhardt John W. , Perdigao Jorge
Published: June 2020

Tooth shaded composite resin is frequently used as a direct restorative material in the oral cavity. However, during setting it undergoes a volumetric shrinkage which can result in leakage around margins of the restoration. Indirect techniques avoid intraoral shrinkage by fabricating and curing the composite at elevated temperatures outside of the mouth. Higher curing temperatures also improve physical properties in vitro. The completed restoration is then cemented into the prepared cavity with a low viscosity composite resin cement. This study evaluated the effect of varied surface preparation and chemical conditioning on the bond strength of two different indirect heat cured composite resins to a composite resin luting cement.

Well and disk specimens of a microfilled resin (Concept, Williams), groups 1-7, and a minifilled hybrid resin (Herculite-XRV-Lab, Kerr), groups 8-14, were fabricated and cured at 250° C and 85 psi pressure. Each resin set was randomly divided into 7 groups of 10 specimens.
Secondary ion mass spectroscopy in the biological and materials sciences
Authors: Linton Richard W.
Published: June 2020

Secondary ion mass spectrometry (SIMS) is based upon energetic ion bombardment of surfaces resulting in in the emission of sputtered particles, including both atomic and molecular ions. The use of mass spectrometric detection provides a highly versatile and sensitive tool for surface and thin film chemical analysis. In recent years, the scope of the technique has broadened to include a variety of analysis modes including:

1.

Elemental Depth Profiling (dynamic SIMS),

2.

Laterally Resolved Imaging (ion microprobe or ion microscope analysis),

3.

Image Depth Profiling (combination of modes 1 and 2 providing 3-D images),

4.

Molecular Monolayer Analysis (static SIMS),

5.

Sputtered Neutral Mass Spectrometry (post-ionization).

Much of the early work in dynamic SIMS centered on the development of depth profiling and imaging techniques, with an emphasis on applications to electronic materials. SIMS has made extensive contributions to semiconductor materials science since the 1960's, including the development of new devices and processes, and in failure analysis.
Contact and non-contact atomic-force microscopy of type I collagen
Authors: Chernoff Ellen A.G. , Chernoff Donald A. , Kjoller Kevin
Published: June 2020

Introduction. Type I collagen was examined using two types of atomic force microscopes (AFM) in a continuing effort to refine the process of obtaining molecular information from biological materials using scanning probe microscopy. Operating in air, a contact mode (Nanoscope II) and a non-contact mode AFM (Nanoscope III) were used to image collagen fibrils polymerized from pepsin-extracted type I bovine skin collagen adsorbed onto mica substrates. AFM is a practical method for high resolution examination of extracellular matrix material without the time consuming preparative techniques required for electron microscopy.

Methods. For fibrillar collagen samples, Vitrogen 100 (Collagen Corporation, Palo Alto, CA) was prepared according to a modification of the procedure provided by Collagen Corp. for neutralized isotonic collagen gels. Monomeric collagen samples were prepared by diluting the vitrogen in 0.012M HCl.

Images captured with the Nanoscope II AFM (Digital Instruments, Santa Barbara, CA) used a “J” scanner (horizontal range of 120 um).
Finding noise-related artifacts in scanned-probe microscope images
Authors: Siriwardane H. , Fraundorf P. , Fei L , James W.J. , Newkirk J. , Pringle O.A.
Published: June 2020

Scanned probe microscope images often contain structure which does not belong to the actual specimen. Some of this structure arises in time-domain instabilities of the microscope and its environment, some of it arises with imperfect attempts of the feedback loop to hold force or current constant, and some of it reflects tip (as opposed to specimen) structure. We illustrate here: (i) artifacts of the first kind, i.e. those which are independent of tip shape and which exist in the slow-scan limit, (ii) the way in which low-pass filtering can give such artifacts three-dimensional character, and (iii) tests involving Fourier phases and amplitudes in scanned probe images which can signal the presence of such artifacts.

The first and best test for artifacts related to time-domain instability is simply to locate precisely the same feature in two micrographs, if possible taken with different scan speeds (e.g. at different magnfications). If the feature remains unchanged in structure and size, then it is unlikely to be a purely time domain artifact.
Hard-copy imaging options
Authors: Polizzotto Leonard
Published: June 2020

Photographic film has played a central role in the recording of microscope images since the invention of photography in the 1830s. Photography rapidly creates an accurate record of the microscopic specimen and avoids the subjectivity that was inherent in written and artistic descriptions of visual observations. Both instant and conventional films offer high resolution, the ability to record a large tonal gradation, and a stable media for long-term data storage.
Newer techniques, such as thermal, ink jet, and laser prints, have grown in popularity because they offer ease-of-use or lower per-image cost. Despite recent improvements, none of these techniques offer the resolution or stability of a photograph. In general, people have been forced to sacrifice quality and permanence in order to achieve the lower per-image cost and ease-of-use promised by alternative recording systems.

Photographic hard copy has traditionally served as both the communication and storage medium. The introduction of digital storage methods has made these functions more distinct.
EXELFS revisited: An improved data analysis technique
Authors: Qian Maoxu , Sarikaya Mehmet , Stern Edward A.
Published: June 2020

EXELFS (extended energy loss fine structure) spectroscopy contains unique information of local atomic structure, same as XAFS (X-ray fine structure), but has several advantages overXAFS, such as having high spatial resolution (nanoscale versus bulk), better low Z element sensitivity, parallel detectability, and no dependability on synchrotron-radiation-sources. Due to poor statistical total counts, however, EELS data quality is inferior and, therefore, EXELFS technique has not been well developed to its full advantages. The main limitations in EELS acquisition are channel-to-channel gain variations (CCGV) in the parallel detection system and low S/N ratio due to the instability of instrument that prevents long acquisition times. Techniques that circumvent CCGV, such as first or second difference, do not allow the retrieval of EXELFS signal from the spectra. Recently we have improved the EELS data acquisition technique so that CCGV could effectively be corrected and statistical fluctuations could reach a level much lower man that in the fine structure.
Optimization and testing of an imaging energy spectrometer for high-resolution electron-energy-loss microanalysis
Authors: Jiang X.G.
Published: June 2020

Electron energy loss (EEL) microanalysis is a powerful technique for studying the chemical composition of a specimen and the distribution of each constituent. The energy loss spectrum of the post-specimen electron beam, on which the technique is based, is obtained by the use of an energy spectrometer. In transmission electron microscopy, the most prevalent type of imaging energy spectrometer is the Prism-Mirror-Prism (PMP) design (Fig. 1). It is compact in size and easy to align. For an acceptance half angle (β in Fig. 1) of 10 mradian, which corresponds to the full field of view of a modified Siemens 102 microscope of our laboratory, an experimental PMP spectrometer with a straight-faced magnetic prism has an energy resolution of 25 eV at the microscope operating voltage of 80 kV. This resolution has permitted ionization energies of different elements to be resolved, thus making the elemental microanalysis possible. However, a resolution of 25 eV is inadequate for resolving and possibly imaging with characteristic molecular energy losses, that are located in the 1.5-10 eV region of the electron energy loss spectrum.
Determination of structure factors of copper by convergent beam electron diffraction
Authors: Mansfield John , Saunders Martin , Burgess George , Bird David , Zaluzec Nestor
Published: June 2020

There has been considerable recent interest in the determination of structure factors from convergent-beam electron diffraction (CBED) patterns and the ultimate goal is the ability to retrieve the crystal structure of an unknown crystal by inversion of a CBED pattern. There are a number of different methods that have been used to extract structure factor information. The zone-axis pattern fitting technique of Bird and Saunders has recently been used to obtain structure factors for silicon that compare well with those obtained by X-ray methods. This work extends the techniques to f.c.c. metals, specifically copper.

CBED patterns were recorded from [110] zone axes of electropolished foils of pure copper (99.999% purity) in the Philips EM420T at Argonne National Laboratory. The patterns were energy-filtered by scanning the whole pattern across the entrance aperture of a Gatan #607 serial energy loss spectrometer and collecting the zero loss intensity only (energy window ∼5eV).
Observation of a supported metal catalyst in an ultra-high-resolution field-emission SEM
Authors: Liu J. , Spinnler G. E.
Published: June 2020

Zeolites loaded with noble-metal particles are interesting catalytic systems. The relative positions of small metal particles on and within the support structure may have significant consequences for catalytic activity. Small metal particles dispersed on model and commercial catalyst supports have been observed by using secondary and Auger electrons in a UHV STEM. In this paper we further report preliminary results of observing a metal/zeolite catalyst in a commercial high-resolution field-emission SEM and investigate the contrast variations of SEM images with the change of incident beam energies.

Metal-loaded zeolite samples were ground to fine powders and were dispersed onto a thin holey carbon film coated on a copper grid. The samples were directly observed without being coated with conducting materials. Such coating would obscure fine-scale surface details and make imaging of small metal particles impossible. The experiments were performed in a field-emission Hitachi S-5000 SEM, operating from 0.5 to 30 kV.
Characterization of Al/GaAs Schottky barriers with thin Si interfacial layers
Authors: Bench M.W. , Miller T.J. , Nathan M.I. , Carter C.B.
Published: June 2020

It has been shown in previous reports that barrier height variations can be achieved in GaAs Schottky diodes grown using molecular beam epitaxy by utilizing a thin epitaxial Si layer (a few monolayers) between the GaAs and the Al contact. The effective barrier height was found to be dependent on the thickness and growth conditions of the Si layer. However, there has remained a question as to the exact nature of the interfacial Si layer. In the present investigation, samples with different Si layer thicknesses (no Si, 6 Å Si, and 20 Å Si, as determined in situ during growth using reflection high energy electron diffraction (RHEED)) were characterized using transmission electron microscopy (TEM) to determine the nature of the Si layers. In the present study, it was also found that the presence of the interfacial Si layers affected the growth orientation and morphology of the Al layers.

The layer structures investigated were grown using molecular beam epitaxy in a system described elsewhere.
Zero-Loss Energy Filtered REM and RHEED Observations on Rutile (110) Surface
Authors: Wang L. , Liu J. , Cowley J. M.
Published: June 2020

In reflection electron microscopy (REM), the surface reflection electrons undergo both elastic and inelastic scattering within a crystal. The dominant inelastic processes are phonon scattering, valence electron excitation, bulk and surface plasmon excitation and combinations of these processes. Multiple inelastic scattering processes are also probable as the mean traveling distance of surface reflection electrons is about 10 to 100 nm. In reflection high energy electron diffraction pattern (RHEED), 50% to 90% of the electrons contributing to surface reflection spots used for imaging have suffered energy loss of more than 10 eV, thus the main limitation on REM image resolution is due to the chromatic aberration effects given by the energy spread from inelastic scattering. An energy filter fitted inside a TEM microscope can remove most of the inelastic scattering contribution and so improve the contrast and resolution. Oxygen-annealed rutile (001), (100) and (110) surfaces were previously studied by REM and RHEED techniques without energy filtering.
Lorentz Electron Microscopy of cobalt borides in a platinum cobalt matrix
Authors: Qiu N. , Wittig J.E.
Published: June 2020

The presence of cobalt borides significantly increases the intrinsic coercivity (Hic) of a Pt-Co alloy. Whereas the maximum Hic for a binary Pt-Co alloy is less than 5 kOe, a ternary Pt42Co45B13 (at%) alloy exhibits intrinsic coercivity as large as 15.2 kOe. The optimum microstructure for the maximum Hic consists of a dispersion of cobalt boride precipitates having the orthorhombic Co3B structure in an Ll0 Pt-Co matrix. Lorentz electron microscopy of the magnetic structure of these cobalt borides has been used to elucidate their strong influence on the magnetic properties of this alloy. Magnetic domain wall thickness measurements assist with modeling of the magnetic hardening mechanism.

Processing the Pt42Co45B13 (at%) material utilized an initial rapid solidification step followed by annealing at 800°C. Samples for Lorentz electron microscopy were prepared by dimple grinding and ion milling to electron transparency. The Lorentz imaging employed the standard Fresnel contrast method by operating a Philips CM20T at 200 kV in the low magnification (LM) mode.
TEM of electron-beam induced crystallization of an amorphous AuFe.03/Si Spin-Glass Multilayer
Authors: Howell D.A. , Hoines L. , Crimp M.A. , Bass J. , Heckman J.W.
Published: June 2020

The use of thin film multilayers for the study of physical phenomena (e.g. spin-glass dc magnetic susceptibility, giant magnetoresistance, and x-ray reflectivity) has grown recently as the technology for their preparation has improved. The multilayers in this study were produced for an investigation of finite-size effects in a AuFe.03 spin-glass.

We prepared the samples by dc sputtering of a AuFe.03, alloy and a Si target in an UHV system. The specimen in this investigation had 67 bilayers of 3 nm spin-glass layers alternating with 7 nm amorphous silicon (a-Si) layers on a (001) single-crystal silicon substrate for a total film thickness of 670 nm. Ultrathin cross-sections were prepared by cleaning the thin-film surface in Freon TF and gluing this surface to a clean ground-glass slide with epoxy. We removed the thin-film from its silicon substrate by peeling the substrate from the film which remained on the glass slide.
A cross-sectional TEM study of ion-sputtered hydroxyapatite on silicon
Authors: Raghunathan K.V. , Griffin R.D. , Rigney E.D. , Janowski G.M. , Petrik G.
Published: June 2020

Recent improvements in biomaterials have led to the development of coatings such as hydroxyapatite (HA), a calcium phosphate phase. One of the main reasons for the interest in HA as a coating material for titanium bone implants is that it is component of bone and teeth and would be expected to be biocompatible.

HA can be deposited by ion beam sputtering, which produces a thin, adherent coating which is initially amorphous. Studies of HA sputter deposited onto titanium have shown that the bond strength increases if the samples are heated-treated under vacuum and decreases if heat-treated in air (Figure 1). The present study will characterize the microstructural evolution of HA which was deposited on a model substrate, Si, after heat treatment.

Coatings of HA were ion beam sputter deposited onto single crystal [001] silicon wafers. The HA-coated silicon wafers were heat treated in air or vacuum at either 500 or 600°C for one hour.
Mechanisms of transgranular carbide precipitation in deformed 304 stainless steels
Authors: Advani A. H. , Murr L.E. , Fisher W.W.
Published: June 2020

Transgranular (TG) carbides form in thermomechanically processed austenitic stainless steels (SS) when the material is plastically deformed to high strain levels, typically above 20%, and for heat treatments that lie within the 500-850°C sensitization range of the SS. In recent work, we have shown that the TG carbide precipitation is site-specific, and favors deformation-induced sites created during the straining process. Specifically, twin-faults and their intersections, and dislocation intersections have been indicated to be preferred sites forTG carbide formation in 304 and316 SS, while clustered regions containing a mix of fine-austenite and lath martensite were also observed to be critical sites for the TG precipitation in 304 SS. In this paper, we present lattice image observations of carbide precipitates in the TG fme-austenite/lath martensite regions of 40% deformed, 670°C/0.1-10h heat treated, 0.051%C 304 SS, as a means to understand the mechanisms of TG carbide precipitation in the SS.
A comparison of Schottky emission and cold field-emission cathodes
Authors: Swanson L.W. , Rathkey D.S.
Published: June 2020

We compare Schottky Emission (SE) and Cold Field Emission (CFE) cathodes with respect to emission characteristics and environmental factors. The CFE cathodes most commonly used are W<310> and a slightly oxidized W<100> used at room temperature. The SE cathode most commonly used is a ZrO coated W<100> emitter which has a localized work function of 2.8 ±0.2 eV on the <100> plane.

In terms of emission mechanism, SE and CFE represent two extremes of a continuous change in surface electric field strength F and temperature T of a pointed cathode. The primary difference between a SE and CFE cathode is F, T, and energy distribution as shown in Fig. 1. TheSE cathode emission distribution contains mostly non-tunneling electrons terminated on the low energy side by the work function barrier. In contrast, the CFE emission distribution is defined by tunneling electrons terminated on the high energy side near the Fermi level of the metal.
Dual Stage SEM with thermal field-emission gun
Authors: Yamazaki S. , Sato T. , Aota S. , Buchanan R.
Published: June 2020

Resolution improvement is an on-going goal in scanning electron microscope development. High resolution is required at both high and low accelerating voltages in a wide field of applications, including, but not exclusive to, semiconductors and new materials development. Two approaches which result in improved resolution through-out the operating voltage range of the SEM are 1) the adoption of low aberration objective lenses, and 2) the use of high brightness electron sources.

The DS-130F SEM which is described here uses a high brightness thermal field emission gun (TFEG) in conjunction with a modified DS-130 column. The electron optical configuration is quite unique, as it includes two independent stages. The top stage places the sample within a high field strength low aberration objective lens, resulting in ultra high resolution on samples up to 18 x 8 mm. The bottom stage accommodates 6” samples and uses a second dedicated conical objective lens allowing a short working distance to be maintained on tilted samples.
Absorption corrections for AEM Analysis of thin-film and sphere samples with large-solid-angle x-ray detectors
Authors: Zreiba Nuri A. , Kelly Thomas F.
Published: June 2020

Recent advances in x-ray detectors for TEM and STEM instruments have resulted in large increases in the solid angle that these detectors subtend with respect to the sample. These solid angles of order 0.2 steradian mean that x rays emitted into a cone of semi-angle equal to 15° will be intercepted by the detector. Since the conventional absorption correction for x-ray analysis assumes that all detected rays are parallel, we chose to examine whether divergent x rays could change the absorption and fluorescence corrections significantly and should therefore be taken into account.

This paper will focus on the effects of such changes on the absorption correction of thin specimens. Two specimen geometries will be considered, namely the usual plane parallel slab and the sphere geometry. Sphere geometries are of interest because they are currently used in the evaluation of the efficiency of x-ray detectors, the results of which are to be presented in the X-ray Optics and Microanalysis Conference in Poland this summer.
X-Ray absorption edge elemental imaging of B. thuringienis
Authors: Stears R. L.
Published: June 2020

Because of the nature of the bacterial endospore, little work has been done on analyzing their elemental distribution and composition in the intact, living, hydrated state. The majority of the qualitative analysis entailed intensive disruption and processing of the endospores, which effects their cellular integrity and composition.

Absorption edge imaging permits elemental analysis of hydrated, unstained specimens at high resolution. By taking advantage of differential absorption of x-ray photons in regions of varying elemental composition, and using a high brightness, tuneable synchrotron source to obtain monochromatic x-rays, contact x-ray micrographs can be made of unfixed, intact endospores that reveal sites of elemental localization. This study presents new data demonstrating the application of x-ray absorption edge imaging to produce elemental information about nitrogen (N) and calcium (Ca) localization using Bacillus thuringiensis as the test specimen.
Imaging of ribosomal RNA-protein interactions by dark-field STEM
Authors: Boublik M. , Mandiyan V. , Tumminia S. , Hainfeld J.F. , Wall J.S.
Published: June 2020

Success in protein-free deposition of native nucleic acid molecules from solutions of selected ionic conditions prompted attempts for high resolution imaging of nucleic acid interactions with proteins, not attainable by conventional EM. Since the nucleic acid molecules can be visualized in the dark-field STEM mode without contrasting by heavy atoms, the established linearity between scattering cross-section and molecular weight can be applied to the determination of their molecular mass (M) linear density (M/L), mass distribution and radius of gyration (RG). Determination of these parameters promotes electron microscopic imaging of biological macromolecules by STEM to a quantitative analytical level. This technique is applied to study the mechanism of 16S rRNA folding during the assembly process of the 30S ribosomal subunit of E. coli. The sequential addition of protein S4 which binds to the 5'end of the 16S rRNA and S8 and S15 which bind to the central domain of the molecule leads to a corresponding increase of mass and increased coiling of the 16S rRNA in the core particles. This increased compactness is evident from the decrease in RG values from 114Å to 91Å (in “ribosomal” buffer consisting of 10 mM Hepes pH 7.6, 60 mM KCl, 2 m Mg(OAc)2, 1 mM DTT). The binding of S20, S17 and S7 which interact with the 5'domain, the central domain and the 3'domain, respectively, continues the trend of mass increase. However, the RG values of the core particles exhibit a reverse trend, an increase to 108Å. In addition, the binding of S7 leads to the formation of a globular mass cluster with a diameter of about 115Å and a mass of ∽300 kDa. The rest of the mass, about 330 kDa, remains loosely coiled giving the particle a “medusa-like” appearance. These results provide direct evidence that 16S RNA undergoes significant structural reorganization during the 30S subunit assembly and show that its interactions with the six primary binding proteins are not sufficient for 16S rRNA coiling into particles resembling the native 30S subunit, contrary to what has been reported in the literature.
Effect of alkali cations on the microstructure and composition of iron silicate catalysts
Authors: Ulan J. , Gronsky R.
Published: June 2020

Zeolites are shape selective catalysts widely used in industry. Selectivity arises from the fact that zeolites possess channels several angstroms in diameter which limits the size of species that can easily diffuse through. Promoted iron oxide is a highly active catalyst for the synthesis of hydrocarbons from CO and H2 (Fischer-Tropsch reaction) but researchers would like to narrow product selectivity to the C7-C10 gasoline range. Selectivity is improved by dispersing iron on zeolites and efforts are now directed at maximizing the iron distribution in the zeolite channels. One approach is to first incorporate iron directly into the zeolite framework during synthesis and then remove the iron from the zeolite framework and ideally form catalytically active iron oxide particles within the channels while still maintaining the pore structure of the zeolite. Iron silicate analogs of the zeolite ZSM-5 (FeZSM-5) have been synthesized and thermal treatments have been employed to produce a catalytic active material. The complete characterization by SEM and TEM of a series of FeZSM-5 catalysts with various Si/Fe ratios and preparation conditions has been achieved. This presentation is a continuation of that work. Three series of FeZSM-5 catalysts were synthesized, two had Si/Fe ratios of 45 with different Si/Al ratios and one had a Si/Fe ratio of 25. In each series, the synthetic conditions were modified by adding alkali metal cations (Li+, Na+ and K+) to the reaction mixture. It has been shown with ZSM-5 that the addition of alkali cations during synthesis produces large single crystals. The effect of alkali cations on the growth of zeolite analogs is interesting for several independent reasons ranging from basic studies of the mechanism of zeolite growth to practical experimental considerations. Single crystals are very desirable for electron microscopy studies: results are unambiguous for a single crystallite in one orientation compared to a region with many overlapping small particles.