bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing the Chemistry and Spectroscopy of Radiation-Sensitive Polymers by Parallel-Detection EELS
Authors: Rightor E. G. , Young G. P.
Published: June 2020

Investigation of neat polymers by TEM is often thwarted by their sensitivity to the incident electron beam, which also limits the usefulness of chemical and spectroscopic information available by electron energy loss spectroscopy (EELS) for these materials. However, parallel-detection EELS systems allow reduced radiation damage, due to their far greater efficiency, thereby promoting their use to obtain this information for polymers. This is evident in qualitative identification of beam sensitive components in polymer blends and detailed investigations of near-edge features of homopolymers.

Spectra were obtained for a poly(bisphenol-A carbonate) (BPAC) blend containing poly(tetrafluoroethylene) (PTFE) using a parallel-EELS and a serial-EELS (Gatan 666, 607) for comparison. A series of homopolymers was also examined using parallel-EELS on a JEOL 2000FX TEM employing a LaB6 filament at 100 kV. Pure homopolymers were obtained from Scientific Polymer Products. The PTFE sample was commercial grade. Polymers were microtomed on a Reichert-Jung Ultracut E and placed on holey carbon grids.
The Use of Correlation Techniques in EELS
Authors: Ouyang F. , Isaacson M. , Kirkland E.J.
Published: June 2020

The signal rate which is attainable in analyzing small volumes of material in the electron microscope is essentially proportional to the cross-section of the process and the number of atoms probed. When analyzing nanometer scale volumes, small concentrations of material or processes of low probability, the experimenter is always faced with spectra of low signal-to-noise (i.e., poor statistics). Provided that the signal rate is larger than the background counting rate due to the detection system, the main approach to increasing statistics (if the probe current density has been maximized) is just to effectively count for a longer period of time.

There are, however, several problems with implementing long counting times on nanovolumes. One is the stability of the incident beam position which effectively limits the analyzed volume. The other is the energy stability of the incident electron beam. For systems with cold field emission sources which are capable of <0.3eV natural energy spreads, the energy stability of the beam is as stringent for EELS as for imaging if one wishes to take full advantage of the narrow energy distribution of the source.
Investigations of Energy Spectroscopic Intensity Distributions in Large-Angle Convergent-Beam Patterns of MoSe2
Authors: Quandt Eckhard , Weickenmeier Andreas , Kohl Helmut , Niedrig Heinz
Published: June 2020

1.

Introduction

With special experimental arrangements - e.g. the rocking crystal technique (fig. 1) - energy-filtered electron diffraction methods can be used for element specific determination of the crystalline structure. Because of the missing phase information of the recorded large angle convergent beam-like patterns (LACBPs) the structure determination can only be achieved by comparing calculated with measured intensity distributions. Therefor a suitable theoretical model should consider the experimentally selected energy loss, scattering vector and detector aperture to calculate the rocking curve intensities. LACBPs of MoSe2 show significant anomalous absorption for major bands (fig. 2,3a), so that absorption has to be considered in an appropriate theoretical model. To verify the reliability of this method experiments and calculations have been carried out with known structures, e.g. the hexagonal lattice of MoSe2.

2.

Experimental realization

The rocking crystal method combined with energy loss spectroscopy of the transmitted electrons allows the recording of energy filtered LACBPs in serial detection mode and energy spectroscopic LACBPs in parallel detection mode as well.
Background Fitting in the Low-Loss Region of Electron Energy Loss Spectra
Authors: Scott C P , Craven A J , Gilmore C J , Bowen A W
Published: June 2020

The normal method of background subtraction in quantitative EELS analysis involves fitting an expression of the form I=AE-r to an energy window preceding the edge of interest; E is energy loss, A and r are fitting parameters. The calculated fit is then extrapolated under the edge, allowing the required signal to be extracted. In the case where the characteristic energy loss is small (E < 100eV), the background does not approximate to this simple form. One cause of this is multiple scattering. Even if the effects of multiple scattering are removed by deconvolution, it is not clear that the background from the recovered single scattering distribution follows this simple form, and, in any case, deconvolution can introduce artefacts.

The above difficulties are particularly severe in the case of Al-Li alloys, where the Li K edge at ~52eV overlaps the Al L2,3 edge at ~72eV, and sharp plasmon peaks occur at intervals of ~15eV in the low loss region. An alternative background fitting technique, based on the work of Zanchi et al, has been tested on spectra taken from pure Al films, with a view to extending the analysis to Al-Li alloys.
Comparison of Images of Crystalline Specimens by Energy-Filtering TEM at 80 keV and CTEM at 200 keV
Authors: Bakenfelder A. , Reimer L. , Rennekamp R.
Published: June 2020

One advantage of energy-filtering electron microscopy (EFEM) is to avoid the chromatic aberration of conventional transmission electron microscopy (CTEM) by the mode of electron spectroscopic imaging (ESI) using either zero-loss filtering of unscattered and elastically scattered electrons or a narrow selected energy window at the most probable loss of the electron-energy-loss spectrum (EELS). Chromatic aberration can also be reduced by high-voltage electron microscopy (HVEM). Comparisons of ESI at 80 keV and CTEM at 200 keV have already been reported for biological tissues. In this contribution we compare the imaging of evaporated crystalline films with ESI at 80 keV in a ZEISS EM902 and with CTEM at 200 keV in a Hitachi H800/NA.

Zero-loss filtering at 80 keV can be applied for maximum mass-thicknesses of x=ρt≃150 μg/cm2 where the zero-loss transmission falls below 0.001 and an energy window at the most-probable energy loss can be used below ≃300 μg/cm2. Inelastic scattering preserves the Bragg contrast.
Advances in Parallel-Detection EELS
Authors: Krivanek O.L. , Dellby N. , Gubbens A.J. , Kundmann M.K. , Leber M.L. , Ray D.A. , Truong K.V.
Published: June 2020

Parallel-detection electron energy-loss spectrometers (PEELS) now routinely provide spectra in which the main source of noise is the statistical fluctuation in the number of arriving electrons (i.e., they have DQE > 0.5), achieve an energy resolution which is more than 90% limited by the electron microscope gun, and are fairly easy to operate. They have pushed the minimum detectable mass (MDM) obtainable by PEELS close to the single atom level, and have improved the minimum detectable mass fraction (MDF) so that it is now comparable or better than MDF detectable by EDXS even for elements as heavy as Fe. The attainable energy resolution is now 0.3-0.5 eV on a routine basis when the spectrometer is mounted on a cold field-emission gun (S)TEM operating at 100 kV (Fig. 1). This impressive progress has opened up an important question: where next?

Our answer is three-fold: towards greater integration of EELS with other techniques of electron microscopy, towards new applications of the technique, and towards more quantitative and yet more user-friendly analysis of the results.
Interfacing a Personal Computer to an Analog Scanning Electron Microscope for Storing Images on Optical Disks
Authors: Ransick Mark H. , Barklay Chadwick D.
Published: June 2020

Most manufacturers of scanning electron microscopes (SEM) now offer models that display an image digitally. This holds many advantages, including the ability to store the image on a disk and perform image analysis on the sample. Most SEMs in service, however, produce only an analog video output; they do not have the ability to digitize the image. Film is the only method of storing images.

Consequentially, film is a significant portion of every microscopy laboratory’s budget. Completely eliminating the use of film from use is not practical. There will always be the need to examine a hard copy of the image; many programs require duplicate copies of each image generated; and it is sound practice to keep a copy of each image on file. By archiving digital images to an inexpensive media, the amount of film used or the time devoted to processing negatives can be greatly reduced.

By using personal computers (PCs)s, with a digitizing board and analog to digital (A/D) board, it is possible to construct a relatively low cost digitizing system for any SEM.
Performance of a Wien-Filter Energy Analyzer Installed in a TEM for EELS
Authors: Terauchi Masami , Kuzuo Ryuichi , Satou Futami , Tanaka Michiyoshi , Tsuno Katsushige , Ohyama Junichi
Published: June 2020

We have been developing a new instrument for high resolution EELS with a spacial resolution of 100nm, a momentum resolution of 0.02A-1 and an energy resolution of 10meV. It is composed of a JEM-1200EX electron microscope - the basic component - , a field emission gun and two Wien filters ( an energy- monochrometer and analyzer) with a retardation lens and an acceleration lens.

The shape of the Wien filter was designed to produce the Wien condition E=v × B (E:electric field, B:magnetic field, v:velocity of electrons ) not only in the filter but also in the fringing field regions and to form a stigmatic focus. We reported a preliminary result on energy-loss spectra of Aluminum obtained by using only the analyzer at two different retarding potentials of Uo=2000V and 600V. We believed that the result was taken at the stigmatic focus condition, though we could not understand the reason why such spectra were not obtained at Uo < 600V.
Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions
Authors: Hasselbach F. , Schäfer A.
Published: June 2020

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.
Particulate Magnetic Media Contamination: Large Defects
Authors: Ackerman Evelyn R. , Kimmel Gerald
Published: June 2020

Participate magnetic media is widely used throughout the computer industry for data storage. Particle contamination is a major source for head crashes in magnetic disk drives. Bit size, track width and flying heights are decreasing because of the demands for greater storage density. As a result, the interfacial phenomena between the head and the disk are becoming critical. Particles generated during the operation of a magnetic disk drive or introduced through the defects in the filtering system, can cause a Head/Disk Interference (HDI) and/or result in a total system failure due to a head crash.

Interaction between the head and the particle becomes responsible for HDI or head crashes. The HDI occur either from the head impacting and shattering the particle as shown in Figure 1 or the particle is dragged across the disk surface by the head as shown in Figure 2. The particle, marked by the arrow, in Figure 2 has been pushed into the substrate.
Measurement of subscellular calcium distribution in cardiac muscle in the presence of caffeine and elevated extracellular calcium
Authors: Hurley B. J. , Cantino M. E.
Published: June 2020

Calcium is thought to play a major role in the activation of mammalian cardiac muscle. Several investigators have utilized Electron Probe X-ray Microanalysis (EPMA) to study the role of calcium in myocardial contraction. The purpose of this study is to measure subcellular elemental concentrations in rat papillary muscle under the influence of caffeine or elevated extracellular calcium. Of particular interest is the concentration of calcium in the junctional sarcoplasmic reticulum (jSR) under these conditions.

Male Sprague-Dawley rats weighing approximately 300 g were anesthetized using I.P. Na-pentabarbitol injection. The hearts were carefully removed and back-perfused with a modified Tyrodes solution via cannulation of the aorta. The wall of the right ventricle was cut away revealing the papillary muscles. The tendon and wall ends of the papillary muscle were then sutured and the muscle was carefully cut out of the heart. The papillary muscle was then placed on the freezing device holder and the suture tied to a fixed post and tension transducer post, as shown in Figure 1.
Concentration determination of chromatin in unstained resin-embedded sections by means of Z-contrast in STEM
Authors: Haider M. , Bohrmann B.
Published: June 2020

The technique of Z-contrast in STEM offers the possibility to determine the local concentration of macromolecules like lipids, proteins or DNA. Contrast formation depends on the atomic composition of the particular structure. In the case of DNA, its phosphorous content discriminates it from other biological macromolecules. In our studies, sections of E. coli, the dinoflagellate Amphidinium carterae and Euglena spec. cells were used which were obtained by cryofixation followed by freeze-substitution into acetone with 3% glutaraldehyde. The samples were then embedded either in Lowicryl HM20 at low temperature or in Epon at high temperature. Sections were coated on both sides with 30Å carbon.

The DF- and the inelastic image have been recorded simultaneously with a Cryo-STEM. This Cryo-STEM is equipped with a highly dispersive Electron Energy Loss Spectrometer. With this instrument pure Z-contrast can be achieved either with a Filtered DF-image divided by the inelastic image or, as is used in this paper, by dividing the conventional DF-image by an inelastic image which has been recorded with an inelastic detector whose response is dependent on the total energy loss of the inelastically scattered electrons.
Monte Carlo electron trajectory simulation of x-ray emission from films supported on substrates
Authors: Newbury Dale E. , Myklebust Robert L.
Published: June 2020

Monte Carlo electron trajectory simulation provides a powerful tool for theoretical studies of electron/x-ray interactions in solid targets. The great power of a Monte Carlo technique arises from the stepwise treatment of the electron trajectory in the target, which provides the capability of dealing with unusual geometric boundary conditions which differ from the ideal of a flat, polished, semiinfinite slab. Special targets, such as randomly tilted surfaces, particles, thin foils, and films supported on substrates, can be simulated by a Monte Carlo procedure.

It is proper to speak of “a” rather than “the” Monte Carlo procedure because there is no single formulation of the simulation in universal use. A variety of choices exists for the treatment of the scattering and energy loss processes. In particular, the approach to simulating inelastic scattering varies widely. While most calculations consider inelastic scattering by means of a continuous energy loss approximation rather than by modeling the discrete inelastic processes, there are now several different choices proposed for the treatment of energy loss in the low energy range (<3 keV) where the Bethe model proves inadequate.
Experimental determination of the total enhancement factor in x-ray microanalysis of thin overlayers
Authors: Nassiopoulos A. G. , Valamontes E. , Travlos T. , Tsamis C.
Published: June 2020

The total enhancement factor in X-ray Microanalysis of thin overlayers has been measured at different primary beam energies by comparing the signal from a thin film deposited on a bulk material to that from a thin unsupported film of the same composition. This enhancement factor contains the contribution of both backscattered electrons and characteristic and bremsstrahlung X-rays created in the bulk by the primary beam , which ionize the film in their way out of the sample.

The experimental results from a Cu film on different substrates ( Si, Ni and Au ) are compared to Monte-Carlo calculations, performed by the authors. In these calculations [1,2] all three correction factors cited above (backscattering, characteristic and continuous X-rays from the bulk) are taken into account. It is thus demonstated that the contribution of continuous X-rays from the bulk take important values (as high as 12-14%) in cases where the substrate is of a high Z material at high primary beam energies (40 keV).
Quantitative electron probe microanalysis of Be in Nb-Be alloys using an a-factor correction technique
Authors: Burilla Chuck T.
Published: June 2020

With the advent of Multilayered Dispersion Elements (MLDE) it is now possible to routinely analyze beryllium in the electron microprobe. In NbBe binary alloys the Be x-ray yield is high enough to allow accurate quantitative analysis of this ultralight element. An empirical correction technique, in conjunction with NbBe standards, enables Be intensities to be converted into concentrations. The minimum detection level of Be in Nb is estimated to be less than 0.05 weight percent.

series of NbBe binary alloys and Be metal were examined with an electron microprobe. Very favorable Be Ka peak intensities and P/B ratios were obtained with a Boron Carbide/Molybdenum MLDE (2d= 203.6 A ). These values are reported in Table 1. Because of many factors, including the probable high absorption of the ultra-soft Be x rays in the matrix and the huge overvoltages affronted, traditional correction procedures such as ZAF can be expected to fail.
An Empirical Test Of A Thin-Film Analysis Routine On Bisrcacu Oxide Superconductor Precursors
Authors: Ross D.K. , Heyman R.V. , Elthon D.
Published: June 2020

Until quite recently, electron microprobe analysis techniques were limited to samples of “infinite” thickness, that is, to samples thick enough such that the entire excitation volume was contained within the material of interest. Thin film analysis was not possible with available matrix correction programs, which were based on the assumption of samples of “infinite” thickness. Now however, algorithms are available that permit analysis of thin samples.

We have obtained one of the more versatile and sophisticated of these programs. In order to investigate the accuracy of this routine we have analyzed several BiSrCaCuO thin films at 15 kV and repeated the analysis at 30 kV. These films were thick enough such that at 15 kV conventional ZAF data reduction yielded acceptable totals (98-101 %) with minimal substrate x rays observed. At 30 kV, however abundant substrate x rays were observed and ZAF yielded very low totals. X-ray intensity ratios from 30 kV runs were used to estimate film thickness and matrix corrections were applied using the Waldo algorithm.
Quantitative Analysis Of X-Ray Images From Geological Materials
Authors: Paque J. M. , Browning R. , King P. L. , Pianetta P.
Published: June 2020

Geological samples typically contain many minerals (phases) with multiple element compositions. A complete analytical description should give the number of phases present, the volume occupied by each phase in the bulk sample, the average and range of composition of each phase, and the bulk composition of the sample. A practical approach to providing such a complete description is from quantitative analysis of multi-elemental x-ray images.

With the advances in recent years in the speed and storage capabilities of laboratory computers, large quantities of data can be efficiently manipulated. Commercial software and hardware presently available allow simultaneous collection of multiple x-ray images from a sample (up to 16 for the Kevex Delta system). Thus, high resolution x-ray images of the majority of the detectable elements in a sample can be collected. The use of statistical techniques, including principal component analysis (PCA), can provide insight into mineral phase composition and the distribution of minerals within a sample.
Composition Particle-Size Relationship In Atmospheric Aerosol Samples
Authors: Tura J.M. , Xaus C. , Traveria A. , Casassas E. , Garcia F.
Published: June 2020

The aim of this work is the scanning electron microscopy with x-ray analysis (SEM-EDX) morphological and microanalytical characterization of atmospheric aerosols in a heavy-traffic suburban area. Aerosols are sampled in a cascade impactor, during a full week. For each size-fraction a semiquantitative analysis of the more characteristic elements is perfomed. A synthetic atmospheric aerosol is used as reference material.

The collection point was placed in the Montcada relay area by the Barcelona-France motorway. Sampling was perfomed during a week, with daily periodicity. A Sierra-Misco high-volume sampler with a five-stage cascade impactor was used. The aerosol samples were collected in fractions according the particle size on the different stages of the impactor and on a backup cellulose-ester absolute filter. At the flow rate used the cut-off values for the particle size collected in each stage was: 6.4, 3.1, 1.7, 0.8 and 0.39 μm. Sampling time was 24 h and the daily air volume aspired was 2.000 m3 aproximately.
Application Of Electron Microscopy To Automotive Finish Defect Analysis
Authors: Mahon Martin J. , Keating Patrick W. , McLaughlin John T.
Published: June 2020

Coatings are applied to appliances, instruments and automobiles for a variety of reasons including corrosion protection and enhancement of market value. Automobile finishes are a highly complex blend of polymeric materials which have a definite impact on the eventual ability of a car to sell. Consumers report that the gloss of the finish is one of the major items they look for in an automobile.

With the finish being such an important part of the automobile, there is a zero tolerance for paint defects by auto assembly plant management. Owing to the increased complexity of the paint matrix and its inability to be “forgiving” when foreign materials are introduced into a newly applied finish, the analysis of paint defects has taken on unparalleled importance. Scanning electron microscopy with its attendant x-ray analysis capability is the premier method of examining defects and attempting to identify their root cause.

Defects are normally examined by cutting out a coupon sized portion of the autobody and viewing in an SEM at various angles.
Raman And Fluorescence Spectra Observed in Laser Microprobe Measurements of Several Compositions in the Ln-Ba-Cu-O System
Authors: Etz Edgar S. , Schroeder Thomas D. , Wong-Ng Winnie
Published: June 2020

We are investigating by Raman microprobe measurements the superconducting and related phases in the LnBa2Cu3O7-x (for x=0 to 1) system where yttrium has been replaced by several of the lanthanide (Ln = Nd,Sm,Eu,Ho,Er) elements. The aim is to relate the observed optical spectra (Raman and fluorescence) to the compositional and structural properties of these solids as part of comprehensive materials characterization. The results are correlated with the methods of synthesis, the processing techniques of these materials, and their superconducting properties. Of relevance is the substitutional chemistry of these isostructural systems, the differences in the spectra, and their microanalytical usefulness for the detection of impurity phases, and the assessment of compositional homogeneity. The Raman spectra of most of these compounds are well understood from accounts in the literature.

The materials examined here are mostly ceramic powders prepared by conventional solid state reaction techniques. The bulk samples are of nominally single-phase composition as determined by x-ray diffraction.
Secondary Ion Mass Spectrometry Studies of Polycrystalline Thin-Film Cdte/Cds Solar Cells
Authors: Asher S.E.
Published: June 2020

Polycrystalline thin films of CdTe deposited on CdS are one of the most promising materials systems currently being investigated for the fabrication of low cost, large area, high efficiency photovoltaic devices. However, many of the deposition processes being used to fabricate these thin film materials have not yet been well characterized. It has been found that a post-fabrication heat-treatment is necessary to improve the quantum efficiency of these devices. Secondary ion mass spectrometry (SIMS) was used to study the interdiffusion of S and Te in CdTe/CdS structures grown by two different methods. The depth profiles revealed significant differences in the sputtering behavior depending on the film morphology.

Two sets of CdTe/CdS samples were studied. The first set of films was deposited at high temperature using a spray pyrolysis technique with no post deposition anneal. The second set of films was electroplated, followed by treatment with CdCl2 and a high temperature anneal.
Cryofixation of Biological Objects
Authors: Müller Martin
Published: June 2020

The immobilisation of biological material kept under optimally controlled physiological conditions is the first and most critical step when attempting to preserve the complex interactions of organelles, macromolecules, ions and water in close relationship to the living state. Immobilization must be sufficiently rapid, trapping dynamic events at membranes, (e.g. membrane fusion and exocytosis which occur on a milisecond time scale) and preventing the lateral displacement of lipids and proteins within the membranes. Techniques based on chemical immobilisation (aldehyde fixation) seem to approach their limits in this respect, although their use will remain indispensible in solving many relevant biological problems. Chemical fixatives react relatively slowly and cannot preserve all cellular components.

Cryoimmobilization represents a farther reaching alternative. Very high cooling rates (10−4 Ksec−1 to 10−6 Ksec−1) are required to prevent the formation and growth of ice crystals by which the structural integrity would be affected. The high cooling rates at the same time bring along a rapid arrest of the physiological events, i.e. a very high time resolution for dynamic processes in the cell and consequently structural immobilisation closely related to the living state.
Specimen Preparation for Clinical Applications of X-Ray Microanalysis
Authors: Shelburne J.D. , Roomans G.M.
Published: June 2020

Proper preparative procedures are a prerequisite for the validity of the results of x-ray microanalysis of biological tissue. Clinical applications of x-ray microanalysis are often concerned with diagnostic problems and the results may have profound practical significance for the patient. From this point of view it is especially important that specimen preparation for clinical applications is carried out correctly.

Some clinical problems require very little tissue preparation. Hair, nails, and kidney and gallbladder stones may be examined and analyzed after carbon coating. High levels of zinc or copper in hair may be indicative of dermatological or systemic diseases. Nail clippings may be analyzed (as an alternative to the more conventional sweat test) to confirm a diagnosis of cystic fibrosis. X-ray microanalysis in combination with scanning electron microscopy has been shown to be the most reliable method for the identification of the components of kidney or gallbladder stones.

A quantitatively very important clinical application of x-ray microanalysis is the identification and quantification of asbestos and other exogenous particles in lung.
The Diamond Knife: A Necessary Tool in Light and Electron Microscopy
Authors: Gnaegi Helmut
Published: June 2020

Since the introduction by H. Fernández-Morán in 1953 [1], the diamond knife has found wide acceptance by the majority of electron microscopists for the preparation of ultrathin sections of biological samples.

Through the years the basic architecture of the knife itself remained unchanged: The cutting edge was formed by the intersection of two planes making an angle of approximately 45°. It is assumed that this angle was taken from the nominal 45° angle of the glass knives.

Reasons for keeping such values were: By in large, 45° angle diamond knives gave satisfactory results for morphological studies. Factors, other than the sectioning artifacts, seemed to be more important for limiting image quality. In recent years electron microscopes have been developed to an extremely high performance, the resolution reaching atomic level. Due to all of these developments, ultramicrotomy became a needed tool not only for plastic embedded and frozen biological samples, but also in materials research for virtually all types of materials.
Cross-Sectional Imaging of Coated Drug Granules
Authors: Mawn M.P. , Linton R.W.
Published: June 2020

Coatings on pharmaceutical products serve many purposes such as hiding an unpalatable drug taste, giving increased stability, and providing controlled-release dosage. The analysis of coatings on drug granules has been performed through “bulk” studies, such as dissolution tests, stability tests, and sieve analysis, which provide little direct structural information about the coating. Microstructural information such as coating thickness, uniformity, and porosity is necessary to help optimize processing conditions as well as to predict dissolution behavior and resultant biological activity. A sample preparation method is described which permits successful imaging of granule drug coatings without sampling bias. Information about the coating structure is obtained through morphometric analysis of cross sectioned embedded granules.

The granules studied were prepared through a wet granulation process and contain approximately 13% (by weight) drug, 4% corn starch, and 83% sucrose. This inner granule (200-250 μm) was coated (10 μm) with an hydrogenated cotton seed oil in a spray congealing microencapsulating process.
X-Ray Microanalysis of Respiratory Epithelial Cells in the Study of Cystic Fibrosis
Authors: Roomans Godfried M. , Sagström Samuel , Ceulemans Joke L.M. , Bijman Jan
Published: June 2020

One of the most important clinical symptoms associated with cystic fibrosis (CF) is obstructive airway disease and recurrent airway infections. The smaller airways in CF patients are blocked by viscous mucus, and infections are common and difficult to manage. Generally, lung disease is directly or indirectly the cause of death in CF. The viscous mucus in CF is likely to be a result of defective water transport in the respiratory epithelium. Water transport is coupled to chloride secretion, and it is strongly suspected that a defective chloride channel in the apical membrane of the respiratory epithelial cells is the basic error in CF. We therefore studied changes in the intracellular concentration of chloride (and other ions) by x-ray microanalysis of cultured respiratory epithelial cells under a variety of conditions.

Tissues were obtained from material excised during polypectomy. The tracheal mucosa was digested with collagenase and the dispersed cells were plated onto Milliporefilters coated with human placental collagen.
Microprobe AES Combined With Scanning RHEED Microscope
Authors: Sakai Y. , Kitamura S. , Buonaquisti A. D.
Published: June 2020

Surface micro-structure analysis is very important for surface study in material science. Observations of surface atomic steps and reconstructed structures have been made using several techniques: reflection high energy electron microscopy (RHEEM), low energy electron reflection microscopy (LEERM) and low energy electron diffraction microscopy (LEEDM).

In the present experiment, observations of surface micro-structures have been made using a scanning type reflection high energy electron diffraction (RHEED) microscopy. This technique has certain advantages of easy combinations with multiple surface analyzing techniques such as scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS).

A schematic diagram of the scanning RHEED microscope combined with the microprobe AES is shown in Fig. 1. RHEED patterns are observed on the fluorescent screen through a viewing port. To observe the micro-structure (scanning RHEED image or dark field image), a particular diffraction spot is selected by means of the other small fluorescent screen with an aperture.
Angular Resolved Electron Spectroscopy with Parallel Recording
Authors: Min Huang , Flora P.S. , Harland C.J. , Venables J.A.
Published: June 2020

A cylindrical mirror analyser (CMA) has been built with a parallel recording detection system. It is being used for angular resolved electron spectroscopy (ARES) within a SEM. The CMA has been optimised for imaging applications; the inner cylinder contains a magnetically focused and scanned, 30kV, SEM electron-optical column. The CMA has a large inner radius (50.8mm) and a large collection solid angle (Ω > 1sterad). An energy resolution (ΔE/E) of 1-2% has been achieved. The design and performance of the combination SEM/CMA instrument has been described previously and the CMA and detector system has been used for low voltage electron spectroscopy. Here we discuss the use of the CMA for ARES and present some preliminary results.

The CMA has been designed for an axis-to-ring focus and uses an annular type detector. This detector consists of a channel-plate/YAG/mirror assembly which is optically coupled to either a photomultiplier for spectroscopy or a TV camera for parallel detection.
Parabolas from Reconstructed Surfaces Observed in Convergent-Beam RHEED Patterns
Authors: Gajdardziska-Josifovska M.
Published: June 2020

Parabolas have been observed in the reflection high-energy electron diffraction (RHEED) patterns from surfaces of single crystals since the early thirties. In the last decade there has been a revival of attempts to elucidate the origin of these surface parabolas. The renewed interest stems from the need to understand the connection between the parabolas and the surface resonance (channeling) condition, the latter being routinely used to obtain higher intensity in reflection electron microscopy (REM) images of surfaces. Several rather diverging descriptions have been proposed to explain the parabolas in the reflection and transmission Kikuchi patterns. Recently we have developed an unifying general treatment in which the parabolas are shown to be K-lines of two-dimensional lattices. Here we want to review the main features of this description and present an experimental diffraction pattern from a 30° MgO (111) surface which displays parabolas that can be attributed to the surface reconstruction.
Experimental Control of Electron-Irradiation Damage
Authors: Egerton R.F.
Published: June 2020

The electrons which convey information about a specimen can also cause permanent changes in its structure and/or chemical composition. The extent of such ‘radiation damage’ depends on several experimental parameters over which the microscopist has control:

Incident energy. Displacement damage and sputtering (which arise from high-angle elastic scattering) occur only above certain threshold energies. On the other hand, radiolysis (due to inelastic scattering) varies inversely with incident energy, except below lkeV where an observed threshold effect for aromatic compounds has been interpreted in terms of the need for inner-shell ionization.

Electron dose. The loss of structure or elemental concentration is usually exponential (Fig.1) and described by a characteristic dose De, although a second process of much larger De is often present.

>Dose rate. For organic compounds, the characteristic dose is normally independent of dose rate, although beneficial effects of high rates and short irradiation times have been reported. For alkali halides, an analogous increase in De with dose rate is observed (Fig.2); the rate of decomposition is presumably limited by diffusion of a species whose concentration gradient is independent of the irradiation flux.
Analytical and High-Resolution EM Study of Crystalline Phases formed at Metal-Ceramic Interface
Authors: Merk N. , Tomsia A. P. , Thomas G.
Published: June 2020

A recent development of new ceramic materials for structural applications involves the joining of ceramic compounds to metals. Due to the wetting problem, an interlayer material (brazing alloy) is generally used to achieve the bonding. The nature of the interfaces between such dissimilar materials is the subject of intensive studies and is of utmost importance to obtain a controlled microstructure at the discontinuities to satisfy the demanding properties for engineering applications . The brazing alloy is generally ductile and hence, does not readily fracture. It must also wett the ceramic with similar thermal expansion coefficient to avoid large stresses at joints. In the present work we study mullite-molybdenum composites using a brazing alloy for the weldment.

A scanning electron micrograph from the cross section of the joining sequence studied here is presented in Fig. 1.
Influence of Tilt Angle on Hole Count and Secondary Fluorescence in x-ray Microanalysis
Authors: Kenik E. A. , Bentley J.
Published: June 2020

The spatial resolution and accuracy of X-ray microanalysis in an analytical electron microscope (AEM) are limited by a variety of factors, two of which are the hole count and secondary fluorescence. The hole count arises from uncollimated radiation, either electrons or X rays, which excites areas of the specimen other than that excited by the primary electron beam. This can result in X-ray generation even when the probe does not hit the specimen; hence the name hole count. Secondary fluorescence deals with X-ray generation resulting from radiation produced by the interaction of the incident probe with the specimen. This radiation may be either backscattered electrons spiraling in the magnetic field of the objective lens or high energy X rays, particularly forward-peaked bremsstrahlung radiation. As the interaction of both the uncollimated radiation and the secondary radiation with the specimen can be influenced by the tilt angle of the specimen, the variation of the hole count and secondary fluorescence with specimen tilt was investigated.
Simultaneous Identification of the Bravais Lattice and Glide Planes From Microdiffraction Patterns: Deduction of the Possible Space Groups
Authors: Paul Morniroli Jean , Gantois Michel
Published: June 2020

Microdiffraction experiments obtained with a small spot size and a nearly parallel electron beam are well-adapted to most specimens and especially to small particles. They are particularly useful when Convergent Beam Electron Diffraction (CBED) patterns do not give the 2D and 3D information required to identify the point and the space groups. They can also be used to start the identification or the determination of a crystal structure. Specific and simplest CBED experiments are later realized to remove left ambiguities.

The microdiffraction Zone Axis Patterns (ZAP) are composed of sharp reflections whose high angular resolution helps to appreciate the shifts and the periodicity differences between the Zero (ZOLZ) and First (FOLZ) Order Laue Zones reflection nets. Observations of thin areas at low temperature are recommended in order to produce many well visible FOLZ reflections.

It was already indicated that the crystal system and the Laue class are deduced from observation of the whole pattern symmetry of the reflections.
Dynamical Diffraction Effect on HOLZ-Pattern Geometry for Semiconductor Alloys of Sil-xGex and Gal-xInxAs
Authors: Okuyama Tetsuya , Matsumura Syo , Yasunaga Tatsuya , Tomokiyo Yoshitsugu , Kuwano Noriyuki , Oki Kensuke
Published: June 2020

A network of dark lines for higher order Laue zone (HOLZ) reflections often appears in the bright-field disc of convergent beam electron diffraction under zone axis incidence. As geometry of the network (HOLZ pattern) depends sensitively on the crystal lattice parameters, the observation of HOLZ pattern has been applied to measure local change in the lattice parameters in various materials. The kinematical diffraction approximation has been usually employed in the analysis of observed HOLZ patterns, where the lattice parameters and the accelerating voltage exist as independent variables. However the positions of HOLZ lines depend also on the crystal potential for electrons, because the lines arise from intersections of dispersion spheres for the HOLZ reflections with the zeroth-order dispersion surface. In the kinematical analysis, an effective accelerating voltage Ee should be used in place of the actual one Ea, in order to compensate for line shift due to the dispersion effect.
Convergent Beam Electron Diffraction Zone Axis Pattern Map of Zirconium
Authors: Silva E. , Scozia R.
Published: June 2020

The purpose in obtaining zone axis pattern map (zap map) from a given material is to provide a quick and reliable tool to identify cristaline phases, and crystallographic directions, even in small particles. Bend contours patterns and Kossel lines patterns maps from Zr single crystal in the [0001] direction have been presented previously. In the present communication convergent beam electron diffraction (CBED) zap map of Zr will be shown. CBED patterns were obtained using a Philips microscope model EM300, which was set up to carry out this technique. Convergent objective upper pole piece for STEM and some electronic modifications in the lens circuits were required, furthermore the microscope was carefully cleaned and it was operated at a vacuum eminently good.

CBED patterns in the Zr zap map consist of zero layer disks, showing fine details within them which correspond to intersecting set of higher order Laue zone (HOLZ) deficiency lines.
Application of a slow-scan CCD camera in protein electron crystallography at 400 KV
Authors: Brink Jaap , Sherman Michael B. , Chiu Wah
Published: June 2020

In protein electron crystallography, high resolution amplitudes and phases are required for a 3D reconstruction of a protein in which one can trace the Cα-backbone. Recording of these amplitudes and phases has so far been done on photographic film. In principle they can be obtained with higher fidelity using an electronic device, such as a slow-scan charge-coupled device (CCD) camera. We use a 1024 × 1024 Gatan CCD camera (model 679) attached to a JEOL 4000EX intermediate voltage electron cryo-microscope. The camera has a 20-30 μm thin P43 phosphor scintillator and an extra set of fiber optics, that reduces the number of x-ray pixels in acquired frames. In this abstract, we will focus on several issues related to the CCD camera in obtaining high resolution diffraction patterns and images from thin protein crystals.

To obtain electron diffraction patterns with sufficient statistical definition, one needs to use an adequate electron dose. However, at exposures well above 0.25 e/Å2, the pattern will suffer from blooming due to the central beam.
P20 phosphor on polyimide as a large area high-resolution transmission screen for slow scan CCD systems
Authors: Ahn C. C. , Karnes S. , Lvovsky M. , Garland C. M. , Atwater H. A. , Fultz B.
Published: June 2020

The bane of CCD imaging systems for transmission electron microscopy at intermediate and high voltages has been their relatively poor modulation transfer function (MTF), or line pair resolution. The problem originates primarily with the phosphor screen. On the one hand, screens should be thick so that as many incident electrons as possible are converted to photons, yielding a high detective quantum efficiency(DQE). The MTF diminishes as a function of scintillator thickness however, and to some extent as a function of fluorescence within the scintillator substrates. Fan has noted that the use of a thin layer of phosphor beneath a self supporting 2μ, thick Al substrate might provide the most appropriate compromise for high DQE and MTF in transmission electron microcscopes which operate at higher voltages. Monte Carlo simulations of high energy electron trajectories reveal that only little beam broadening occurs within this thickness of Al film. Consequently, the MTF is limited predominantly by broadening within the thin phosphor underlayer. There are difficulties however, in the practical implementation of this design, associated mostly with the mechanical stability of the Al support film.
HREM autotuning on crystalline materials
Authors: Pan M. , Krivanek O.L.
Published: June 2020

Complete autotuning of a high resolution electron microscope has been well established. It performs the following tasks: align the electron beam along the true electron-optical axis of objective lens (autoalignment), correct the astigmatism (autostigmation), and set the defocus to a user defined value (autofocus). It can also characterize the coefficient of 3-fold astigmatism while performing the autoalignment. Based on diffractogram analysis current HREM autotuning algorithm only works on amorphous materials. In reality, however, most of the HREM practice is performed on crystalline materials. Therefore it is highly desirable to extend the current HREM autotuning algorithm to crystalline specimens. In this abstract we report preliminary studies on attempting to analyze diffractograms from a mix of crystalline and amorphous materials.

For crystalline specimens observed in most high resolution electron microscopes, except under UHV conditions, there is typically a thin layer of amorphous contamination due to either sample preparation or poor vacuum conditions. This amorphous layer can be easily seen at the edge of a crystalline sample in the microscope.
Building data storage systems and data networks to support digital microscopy
Authors: Dodson T. A. , Nolan T. A. , Allard L. F. , Völkl E.
Published: June 2020

As laboratories like the Materials Analysis User Center (MAUC) in the HTML at ORNL move from analog to digital imaging systems, the process for acquiring, processing, analyzing, and publishing research results is changing. In this case since original scientific data exist only in digital form, analog systems for gathering, storing, and transmitting data are being set aside in favor of digital systems. In order to adequately protect original scientific data and to ensure that digital laboratories have the same (or greater) functionality as analog laboratories, scientists must focus on building information systems that make data highly available, highly reliable, and quickly accessible. Meeting these three objectives imposes special requirements for both data storage systems and data networks.
A data storage system for a digital microscopy laboratory must have a very large capacity (at MAUC, 30 GB). In addition, the data stored within the system must be highly available and highly reliable.