bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryo-Electron Tomography of Isolated Triad Junctions from Skeletal Muscle
Authors: Hsieh C-E , Marko M , Rath BK , Fleischer S , Wagenknecht T
Published: July 2020

In skeletal muscle, depolarization of the plasma membrane, which is initiated at the neuromuscular junction, is transduced to a rise in cytoplasmic calcium at specialized structures known as triad junctions (TJs). TJs occur in the myofiber’s interior at regions near the z-lines, where transversely oriented tubular invaginations of the plasma membrane (T-tubules) form junctions with two elements of the sarcoplasmic reticulum (SR). Isolation of membrane fractions that are enriched in junctional complexes and which retain function has been reported.

Figure 1 shows a region of an electron micrograph containing an isolated TJ in the frozen-hydrated state. in the orientation shown, two SR-derived vesicles sandwich a flattened vesicle derived from the T-tubule. The junctional regions contain a complex distribution of density, presumably due to proteins that are known to be present in TJs. Electron tomography offers the means to determine the three-dimensional mass density from such micrographs, which would greatly aid in their interpretation. Only recently has the automated data collection technology for determining tomograms of non-stained, frozen-hydrated specimens become available. Here we describe the first tomographic reconstruction of a frozen-hydrated triad junction by automated electron tomography.
Detection and Identification of Macromolecular Complexes in Electron Tomograms of ‘Phantom Cells’
Authors: Böhm Jochen , Frangakis Achilleas S , Nicastro Daniela , Nickell Stephan , Hegerl Reiner , Baumeister Wolfgang
Published: July 2020

One of the most promising and exciting developments in electron tomography is its application to ice-embedded cells and cellular organelles. The primary goal of cellular electron tomography is not to obtain a high-resolution structure of a particular protein complex, but to identify a macromolecule by virtue of its structural signature and to locate it in the context of the native cellular environment. We present a computationally feasible approach, which demonstrates that an objective identification of large macromolecular complexes in cells is possible, given that a highresolution reconstruction and the structure of the molecular assembly under scrutiny are available. Our aim is to quantify the identification results using a realistic test specimen, open for the modification of experimental parameters like thickness, protein density or protein composition. in this study, the reliability of the algorithm applied to electron tomograms of ‘phantom cells’ - mimicking a real cell - is shown.

We prepared phospholipid vesicles that were filled with different macromolecular complexes. First, a phospholipid solution (SOPC) was sonicated and mixed with His-tagged macromolecular complexes, such as thermosomes, 20S proteasomes or a mixture of both. The lipid-protein mixture was subjected to several freeze-thaw cycles and extruded to produce uni-laminar ‘phantom cells’ of various sizes.
Environmental SEM (ESEM) in the Study of Biomedical Materials, Cells & Interfaces
Authors: Stokes DJ , Rea SM , Porter AE , Best SM , Bonfield W
Published: July 2020

The ability of ESEM to image insulating and/or moist specimens without the need for the removal of volatile components or the application of a conductive coating has significantly increased the potential range of experiments and observations that can be performed at the high resolution of electron microscopy. Such a technological advance has particularly important implications for the study of soft matter, complex fluids and biological specimens.

An important area of study to which ESEM can be readily applied is that of materials for biomedical applications. Hydroxyapatite (HA) ceramics and HA/polymer composites (e.g. HAPEX™) are being developed for use as synthetic scaffolds in bone tissue engineering. The bioactivity of these materials is dependent upon such factors as phase composition, chemical composition, surface activity, crystallinity and microstructure. Using ESEM it is possible to obtain surface-sensitive, specimen-dependent secondary electron images (in the absence of specimen coating), yielding potentially new perspectives on microstructure to complement information derived from other techniques.
Advanced Raman Spectroscopy for Pharmaceutical and Biological Applications
Authors: Whitley Andrew , Adar Fran , Geiger Ruth
Published: July 2020

With the advent of easy to use analytical and research instrumentation the Raman technique has finally become accepted and is now widely used by pharmaceutical and biomedical companies. Applications range from simple polymorphic crystal form and protein studies to Raman mapping studies of active/excipient distribution and association that give a better understanding of drug dissolution and effectiveness. Examples of such work will be discussed.

More recently with the growing confidence in the power of Raman spectroscopy pharmaceutical and biomedical companies have teamed with instrument companies to develop specific Raman tools. One example of this is the development of a Raman mutiwell/microarray analyzer. High Throughput screening (HTS) is the latest approach in analytical technology. Used particularly in the pharmaceutical industry and in the life science laboratories, this method enables systematic screening of drug design and high throughput analysis of batch production. Combinatorial chemistry is a statistical approach in synthetic chemistry.
Chromium-Doped Luminescent Glasses for Raman Intensity Calibration with 785 nm Laser Excitation
Authors: Etz Edgar S , Hurst Wilbur S , Choquette Steven J , Blackburn Douglas H
Published: July 2020

In work reported previously we, and the McCreery Group at Ohio State University, have proposed the use of glass luminescence standards for the calibration of the Raman spectral intensity. We now have a program underway that is directed at the development of such secondary standards for the calibration of the Raman instrument response function. The first Raman intensity standard to be certified and issued by NIST this year will be for the relative intensity calibration of Raman spectra excited at 785 nm. in general, for any laser excitation wavelength, the calibration procedure is based on the use of luminescent glasses, doped with either transition metal or rare earth ions, that will furnish structureless, broad-band emission spectra upon laser excitation, over any chosen Raman range. For any selected glass standard, the intensity of the luminescence spectrum is calibrated versus the radiant output of a NIST-calibrated white light source, thereby transferring the white light calibration onto the output emission of the luminescent glass.
Emerging Pathogens: Something Old, Something New
Authors: E. Miller Sara , N. Howell David
Published: July 2020

Infectious diseases are the leading cause of death worldwide and the third leading cause in the US. Among these maladies are many that can be classified as emerging diseases. Some of these disorders may be caused by truly novel pathogens. in others, the causative organisms have been present for many years (for some, probably millennia), but have escaped detection until recently. Still others represent the re-emergence of known pathogenic organisms after a long period of quiescence. The mention of emerging pathogens brings to mind sensational exotic and feared microorganisms such as Ebola virus, human immunodeficiency virus (HIV), hantavirus, West Nile virus, Yersinia pestis (plague), and prion diseases such as bovine spongiform encephalitis (BSE, “mad cow” disease) which have been associated with variant Creutzfeldt- Jakob disease (CJD) in humans. However, other organisms that have been known for some time can be classified as emerging pathogens as they continually mutate, recombine, and adapt, causing misery and death.
Past, Present and Future of Analytical Stems
Authors: Colliex C
Published: July 2020

Twenty five years ago, in august 1976, a specialist workshop gathered in Cornell University, at John Silcox's invitation, scientists covering a broad spectrum of interests to assess the potential of analytical electron microscopy, as to instrumentation, fundamental limits, general level of data processing and current theoretical understanding. If the STEM instrument had already been existing for a few years in Crewe's laboratory, its major emphasis, in spite of the existence of an EELS spectrometer, had focused on new modes of high resolution imaging. At the first Cornell workshop, the STEM instrument was for the first time recognized as a potentially formidable analytical instrument because of the possibility of extracting all available signals simultaneously. Furthermore it was directly suitable for digital computer processing and therefore for providing quantitative information. It was also pointed out that a major advantage of the STEM would be its potential to record EELS spectra from every point in the field of view as one scans an area to form an image, thus offering the capability of "chemical" mapping beyond "elemental" mapping.
Contrast Effect of Strain Fields in ADF-STEM Imaging
Authors: Yu Z , Muller DA , Baumann F , Silcox J
Published: July 2020

STEM is an important tool for the study of material by forming Z-contrast ADF images. Studies of strain fields suggest that strain can cause extra contrast in ADF images. Since strain fields exist in many TEM samples, especially interfaces of two different materials, it is necessary to study the contrast effect of strain fields in more detail. in this paper, we study the contrast effect of strain fields by STEM experiments and multislice simulations.

Sample thickness and the dimensions of ADF detector can both affect strain contrast. We first study the influence of sample thickness. A cross-section TEM sample of an interface of crystal silicon and amorphous silicon was prepared by typical tripod polishing and was studied with the 100 kV Cornell VG 5.0 UHV STEM. The sample was tilted so that the crystal was on the (110) zone axis and ADF images of the interface were recorded.
Quantitative Low Loss and Ultra Low Loss Spectroscopy in the STEM
Authors: Howie A , Garcia de Abajo FJ , Yamamoto N
Published: July 2020

Many of the topics in valence spectroscopy originally pioneered with TEM equipment have now been taken over by STEM. Notable exceptions are the studies by J. Silcox and his colleagues of plasmon dispersion and of the guided modes in thin slabs where retardation and other relativistic effects arise. The growing use of STEM valence EELS on increasingly complex nanostructures and the development of dielectric excitation theory for quantitative interpretation of the results were recently reviewed. The spatial resolution approaches the atomic scale, exceeding by orders of magnitude the capability of near field spectroscopy. By using the cathodoluminescence (CDL) signal, optical precision in STEM energy loss measurement can also be achieved, particularly in the difficult region below 5 eV or even 1 eV. High spatial resolution can be preserved provided that an intermediate stage of carrier diffusion is not involved in the radiative decay of excitations.

Figure 1 shows STEM CDL images of an Ag particle obtained from the dipole l=1 and quadrupole l=2 surface plasmon excitations
EELS as a Probe of Local Electronic Structure and Cohesion
Authors: Muller David A
Published: July 2020

There is an intimate connection between the electronic structure of a material and its physical properties. to change one, is to change the other. Some of the most striking illustrations of this relationship can be found at grain boundaries in metals and their alloys. Here, the most important changes in cohesion can be described by changes in the local density of states (LDOS), which in turn can be measured using EELS [1]. The first demonstration that EELS could be used to connect the electronic and mechanical properties of a material was in revealing the role that boron has in restoring a bulk-like bonding to grain boundaries in Ni3Al [2,3]. Boron was known to change the fracture mode in Ni3Al from intergranular to transgranular, possibly by enhancing grain boundary cohesion.

What interested me in this project, when John Silcox first suggested it as a thesis topic, was the potential of using the EELS fine structure to measure materials properties directly.
Automated Analysis of X-Ray Spectrum Images from the STEM
Authors: Kotula PG , Michael JR , Keenan MR
Published: July 2020

For failure analysis and process control it is critical to perform comprehensive microanalysis. The desire to perform this analysis thoroughly but quickly is the ultimate goal. Typical analyses of this sort have been performed by collecting x-ray spectra at points, along lines, by mapping, and more recently by spectrum imaging where a complete x-ray spectrum is collected over a 2D array of points. Spectrum imaging is perhaps of greatest interest for its potential to thoroughly and comprehensively sample a given area of a microstructure. The problem is that the techniques available for analyzing large (> 1000 spectra) spectrum image (SI) data sets have been limited to mapping after the fact and perhaps thresholding the maps and summing the resultant spectra from those pixels. As a result, there is a need for more sophisticated SI analysis tools, capable of reducing the SI to its essence-the chemical components. Software is currently commercially available for the automated analysis of x-ray spectrum images (SIs) from the SEM
Energy Dispersive Spectrometry Calibration of Fe and Co
Authors: Vartuli CB , Stevie FA , Purcell BM , Scwhitter A , Rossie B , Brown S , Shofner TL , Anderson SD , McKinley JM , Irwin RB
Published: July 2020

Energy Dispersive Spectrometry (EDS) is an ubiquitous method of elemental analysis for SEM, TEM, and STEM applications. The elements of interest are generally quantified without standards using theoretical calculations or by using standards that are high purity specimens of the elements measured. However, EDS is often used to determine a small percentage of an element in a matrix. The accuracy and limit of detection of these low concentration measurements has not been established. An earlier report proved the concept that a cross section high dose BF2 implanted specimen could provide a standard for EDS measurement of F. This study extends this quantification approach to transition elements of importance to the semiconductor industry.

The Fe and Co standards were created by high dose ion implantation. For ions implanted into silicon, a dose of lxl016 atoms/cm2 results in a peak concentration of approximately lxl021 atoms/cm3 or 2% atomic. The exact concentration can be determined using methods such as Rutherford Backscattering Spectrometry (RBS) and Secondary Ion Mass Spectrometry (SIMS).
Quantification of Compositional Modulations in Self-Assembled Multisheet (Cd, Zn, Mn)Se Quantum Dot Structures
Authors: Topuria T , Möck P , Browning ND , Titova LV , Dobrowolska M , Lee S , Furdyna JK
Published: July 2020

CdSe/ZnSe based semiconductor quantum dot (Q D) structures are a promising candidate for optoelectronic device applications. However, key to the luminescence properties is the cation distribution and ordering on the atomic level within the CdSe QDs/agglomerates. Here the Z contrast imaging technique in the scanning transmission electron microscope (STEM) is employed to study multisheet (Cd,Zn,Mn)Se QD structures. Since Z-contrast is an incoherent imaging technique, problems associated with strain contrast in conventional TEM are avoided an accurate size and composition determinations can be made.

For this work we used a JEOL JEM 201 OF field emission STEM/TEM. The sample was grown by molecular beam epitaxy in order to achieve vertical self-ordering of Cd rich quasi-2D platelet This sample comprises 8 sequences of 10 ML (2.83 nm)Zn0.9Mn0.1Se cladding layer and 0.3 ML (0.09 nm) CdSe sheet, a further 10 ML of Zn0.9Mn0.1Se, and a 50 nm ZnSe capping layer.
Extension of HRTEM Resolution: Solving Structures of Grain Boundary and Interface Using Gerchberg-Saxton Algorithm and Blind Deconvolution
Authors: Chen F-R , Ichinose H , Kai J J , Chang L
Published: July 2020

Oxides, nitrides, carbides and silicides contain more than one type of atoms that gives one extra degree of freedom in the grain boundary and interfacial structure. This degree of freedom is the choice of the boundary plane containing different type of atoms which results of several structural multiplicities in the boundary. Coexistence of the structural multiplicities (or boundary domains) in the interface and grain boundary were reported [1, 2]. The structural information in high frequency domain is usually blurred and lost in the lens system of a high resolution transmission electron microscopes (HRTEM) such that the HRTEM image may not truly represent the real structure. Conventionally, the structures of grain boundary and interface were solved using forward method. The forward method involves matching the simulated images from guessed possible models with the through focal series experimental images. Recently, rereconstruction methods such as focal variation holography [3, 4], tiltbeam holography [5] and Gerchberg-Saxton algorithm [6] provide a backward (direct) way to recover the structural information lost in a modern microscope.
Quantitative High Resolution Electron Microscopy of Grain Boundaries and Comparison with Atomistic Simulations
Authors: Campbell GH , King WE , Plitzko JM , Belak J , Foiles SM
Published: July 2020

The technique of high-resolution transmission electron microscopy (HREM) produces images that contain information about the atomic structure of the specimen. Within additional, very stringent, constraints, the HREM image can contain information about atomic structure of crystal defects, including grain boundaries and interfaces. to extract this information from the image it is necessary to compare the experimental image with a simulated image calculated based upon an atomic model of the specimen.2 in this comparison, investigators have been aided by the use of quantitative techniques.

Atomistic simulations are often used to predict the atomic structure of crystal defects or to simulate the evolution of dynamic processes in crystals, e.g. radiation effects or dislocation motion and interaction. During the development of new models of interatomic interactions, the predictions of simulations are tested against experimental observations to validate new potentials. Grain boundary structure is a good test because atoms residing in the boundary experience environments (interatomic distances and angles) that are significantly different from those experienced by atoms residing in a perfect crystal lattice site.
AEM and HRTEM Analysis of the Metal-Oxide Interface of Zircaloy-4, Prepared by FIB
Authors: Abolhassani S , Schäublin R , Groeschel F , Bart G
Published: July 2020

The understanding of the mechanism of oxidation of Zircaloy materials provides an important support for the corrosion control of the fuel claddings in the light water nuclear reactors. Many investigations are devoted to the study of the oxidation of these materials. One of the important aspects of these studies, is the analysis of the metal-oxide interface, which produces information about the nature of the oxide formed at the interface, at different stages of oxidation and the influence of the oxide structure and morphology on the formation and growth of the oxide.

In the present study, analytical electron microscopy (AEM) and high resolution transmission electron microscopy (HRTEM) are used to examine the metal-oxide interface of an un-irradiated Zircaloy-4 material, oxidized in autoclave, under pressurized water reactor conditions.

The TEM specimen preparation for the interface analysis is an important step of the investigation, since the transverse section required for such observation should be sufficiently thin exactly at the position of the interface.
Experimental Evidence of Ca Segregation to Antiphase Boundaries in Pigeonite
Authors: Moore KT , Veblen DR , Howe JM
Published: July 2020

For over 30 years geologists have been trying to better understand antiphase domains (APD) and boundaries (APB) in pigeonite in hopes of using them as markers for the thermal history of the rocks in which they are found. The ability to know the cooling history of igneous rocks is of great interest to geologists and pigeonite has received special attention on this matter because it has exsolution (precipitation) and antiphase domains (APD), both of which can be used as possible thermal markers. APDs in pigeonite arise because of the C2/c → P21/c transformation that occurs upon cooling. When multiple APDs nucleate, grow, and impinge upon one another, they are either in registry or have a translational discrepancy of ½(a+b). The size of the APDs can be used as a qualitative marker of cooling rates, since slowly cooled pigeonites favor large APDs and rapidly cooled pigeonites favor small APDs.
Energy-Filtering TEM Imaging of Zrb2/Sic Composite — An Ultrahigh Temperature Ceramic for Thermal Protection
Authors: Xu Huifang , Zhai Jiangping
Published: July 2020

Ceramic of ZrB2 and its composite of the ceramics with SiC are used for ultrahigh temperature protection coatings in re-entry space vehicles because of high melting temperature of ZrB2 (3245°C). Chemical composition and microstructure of the ceramics are critical to thennal shock properties of the ceramics. Especially oxidation of boron and formation of boron oxide will degrade property of thermal resistance. Conventional TEM with Energy dispersive X-ray spectroscopy (EDS) is unable to study light elements like boron. However, parallel-recorded electron energy-loss spectroscopy (EELS) and energy-filtering GIF system associated with field-emission gun (FEG) TEM are able to carry out chemical imaging and chemical information of light elements. Bonding structure and oxidation states of an element (such as B) can be obtained by using EELS.

Figure A is a zero-loss bright-field TEM image showing an interface between ZrB2 and SiC. Figure B is a Plasmon-loss filtered TEM image of the same area. A plasmon peak at about 20 eV was used for this image.
Anisotropic Grain Boundary Segregation in Y-Doped TiO2
Authors: Lian G D , Susalla A , Dickey E C
Published: July 2020

A variety of properties of polycrystalline TiO2, such as conductivity, creep and grain boundary diffusion, are strongly dependent on the atomic-level structure and chemistry of grain boundaries. TiO2 has been studied as a model dielectric system because of its relatively simple structure and well-understood point defect chemistry. Defect segregation in grain boundaries of polycrystalline and bi-crystal TiO2 have been studied by several groups and significant variations in solute segregation levels from boundary to boundary were observed. in this paper, we address this issue of anisotropic grain boundary segregation. We have measured solute segregation as a function of grain boundary misorientation to determine any correlation between segregation and misorientation.

Yttria-doped TiO2 polycrystalline samples were prepared by mixing 99.999% pure TiO2 powder with 0.1% mole percent 99.99% purity Y(NO3)3 (both powders are commercially available from Aldrich Co. or Alfa Co.), followed by uni-axial pressed to 200-400Pa and sintering at 1300 °C for about 5-7 hours.
Atomic Structure Determination Using the Focal-Series Reconstruction Technique
Authors: Thust A , Jia CL
Published: July 2020

During the last five years the technique focal-series reconstruction has evolved to a powerful tool for investigating materials science problems in high-resolution transmission electron microscopy. Compared to the conventional interpretation of one single high-resolution image, the quantum mechanical electron wave function at the exit plane of the object (exit-plane wave function, EPW) is in many cases a better starting point for the materials analysis. The retrieval of the EPW is achieved on a routine basis by applying automated numerical procedures to a series of images taken from the same specimen area at different objective lens defocus values. The application of the reconstruction procedure allows one to remove numerically all the well known instrumental artifacts, such as nonlinear contrast formation or delocalisation effects due to spherical aberration and other parasitic aberrations. The reconstructed EPW gives thus direct insight into the atomic structure in the case of sufficiently thin objects and renders tedious image simulations of complicated defects unnecessary in many cases.
Monodisperse Pbse Nanoparticle Self-Assembling Nanoarrays Before and After Annealing
Authors: Zhou WL , Wiemann J , Stokes KL , O’Connor CJ
Published: July 2020

A variety of semiconductor and metal nanoparticles can be synthesized and tunable in size from about 10 to 200 Å using size-selective separation technique. Preparation of monodisperse samples enables systematic characterization of the structural, electron, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy and ordered nanocrystal. At inter-particle separations 5-100 Å, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. The fabrication of monodisperse ordered nanoarrays with the inter-particle separations less than 5Å will be very important to study its physical properties since interaction between neighboring nanocrystals cause otherwise insulating assemblies to become semiconducting, metallic, or superconducting depending on nanocrystals composition. Here we present the fabrication of monodisperse PbSe nanoarrays with inter-particle distance less than 5 Å and its nanostructure study.
Transmission Electron Microscopy Study of Y2O3 Nanotips Grown on LaAlO3
Authors: Sun HP , Jan DB , Jia QX , Pan XQ
Published: July 2020

Y2O3 is a super refractory oxide with high thermal stability and finds various applications in optics and microelectronic devices. Recently, Eu-activated Y2O3 films attracted much research interest due to its promising applications in flat panel field emission displays. Epitaxial Y2O3:Eu thin films have been grown on LaA1O3(LAO). in this paper we report a transmission electron microscopy (TEM) study of Y2O3 nano tip-structure grown on LAO by pulsed laser deposition using stoichiometric YBa2Cu3O7-σ.a target under a low oxygen pressure. The experimental work was conducted within a JEOL2010F TEM equipped with an ED AX system.

Fig.l is a low magnification cross-section TEM image of the nano-tip structure grown on (001) LAO. The lattice parameters of the tips were calculated to be that of Y2O3 by using LAO as a standard for indexing the diffraction patterns. Nano electron beam diffraction patterns from the tips along [100] and [110] axis are shown in Fig.2a and Fig.2b, respectively, in agreement with the simulated ones using bulk Y2O3 structure.
Grain Boundary Segregation in Zr-, B- and C-Doped Mo
Authors: Miller M K , Kenik E A , Russell K F , Bryhan A J
Published: July 2020

Molybdenum-based alloys possess a unique combination of physical properties including high strength at elevated temperatures, high thermal conductivity, low coefficient of thermal expansion, and excellent performance in neutron flux environments. However, welds in commercial grade molybdenum alloys typically exhibit low (∼3%) ductility which limits their application. Bryhan has shown that controlled additions of substitutional and interstitial alloying elements can provide almost 20% elongation from gas-tungsten arc welds in 6.35-mm-thick material. Therefore, molybdenum alloys may be considered for use in fusion reactors and other high temperature applications.

The molybdenum alloy was vacuum arc-cast with 0.16 at % Zr intended to getter the O (250 appm) and N (178 appm) impurities together with 53 appm B and 96 appm C intended to strengthen the grain boundaries. The 4-pass welding process was performed on a 6.35-mm plate in a controlled atmosphere chamber where the O, N and water vapor impurity levels were < 10 wppm each.
In Situ TEM Analysis of Facet Motion in Gold Σ=3 {112} Boundaries
Authors: Medlin DL
Published: July 2020

Interfacial anisotropy complicates the prediction of microstructural evolution, particularly ir extreme cases for which the presence of facets and corners prevents the application of classical notions of grain-boundary curvature. Although there has been much effort at incorporating anisotropic grain-boundary properties, including faceted geometries, into computational approaches for microstructural evolution, at present our mechanistic understanding of the behavior of facets anc their junctions remains limited. In this presentation, we investigate the development of faceted boundaries between Σ=3 <111> oriented grains in epitaxially deposited gold thin films. This system is well suited tc experimental studies of facet evolution since the crystallography and structure of the boundaries is already well understood. It is well known that “double-positioning” of epitaxially aligned <111> grains on a surface of three-fold or six-fold symmetry results in a microstructure composed of grains in two twin-related (Σ=3) variants that are separated by facets running vertically through the film and forming 120 degree corners [1,2].
How accurate is ALCHEMI for ordering measurements?
Authors: Jiang Nan
Published: July 2020

Atom location by channeling-enhanced microanalysis (ALCHEMI) promises a straightforward measurement of ordering in materials. On tilting the electron beam in a transmission electron microscope (TEM) about a superlattice Bragg position the electron channeling changes, weighting X-ray production from each of the sublattices differently. The overall X-ray signal, converted to an apparent composition via a kinematical non-channeling standardization, moves between the composition of the constitute sublattices. However, the accuracy of measurement always bothers many researchers. Results may vary from time to time, and in the worse cases, the composition outputs are nonsense. Table 1 gives an example of a series of ALCHEMIC measurements in a B2 Ti50Al42Mo8 intermetallic alloy.

In general, two major sources cause errors in ALCHEMI: weak channeling and delocalization effects. The later only results in “systematic errors”, which can always be corrected or reduced by theoretical calculations. However, it is difficult to improve the error due to weak channeling.
3d Reconstruction of Sub-Nm Beam Profiles in STEM
Authors: Möbus G , Dunin-Borkowski RE , Hethėrington CJD , Hutchison JL
Published: July 2020

Introduction:Atomically resolved chemical analysis using techniques such as electron energy loss spectroscopy and annular dark field imaging relies on the ability to form a well-characterised sub-nm electron beam in a FEGTEM/STEM [1-2]. to understand EELS+EDX-signal formation upon propagation of a sub-nm beam through materials we first have to assess precisely the beam intensity distribution in vacuum and find conditions for the best obtainable resolution.

Experimental Details:Modern TEM/STEM instruments combine features of both imaging and scanning technology. The beam forming capability approaches closely that for dedicated STEMs, while CCD recording devices allow us to measure the beam profile by direct imaging at magnifications up to 1.5 M. The recording of a “z-section” series through the 3D intensity distribution of the cross-over can therefore be realised by recording of a “condenser focal series”.
The Study of Structural Disorder in Spinel by ALCHEMI
Authors: Anderson IM
Published: July 2020

The mineral spinel (MgAl2O4) is a candidate material for proposed fusion reactors because of its resistance to structural damage during irradiation. When irradiated to high damage levels, spinel is eventually driven amorphous. However, at lower fluences the nearly cubic close packed arrangement of the oxygen anions remains intact, as indicated by electron diffraction patterns consistent with a face centered cubic Bravais lattice. in this regime, the damage to the material is manifested primarily in the redistribution of the magnesium and aluminum cations among the interstices of the anion sublattice. For ion irradiation, the study of these early stages of damage is well suited to electron beam characterization methods, because the damage is spatially localized at the nearsurface region. Electron diffraction methods have been used for the characterization of cation disorder, but are notoriously unreliable because the similarity in the elastic scattering cross sections offers little discrimination between the magnesium and aluminum cations.
Anomalies in the Hough Transform of Kikuchi Bands in EBSD
Authors: Tao Xiaodong , Eades Alwyn
Published: July 2020

The Hough Transform is widely used to detect linear features in image processing techniques. However, the features sought in the EBSD patterns are typically Kikuchi bands from low-index crystal planes, which are not lines but are bands of above average intensity bordered by dark bands. This gives rise to a characteristic shaped peak in the Hough transform that has been called the “butterfly” shape. in most cases, to reduce noise, the Hough Transform is convoluted with a mask having a matching “butterfly” shape. Unfortunately, this method sacrifices resolution through averaging the intensity of neighboring pixels. We have been concerned to use the Hough transform to locate the position of the Kikuchi bands with the highest possible precision. in order to achieve this goal we have looked into the way the Hough transform works on Kikuchi bands in detail, and found some anomalies that must be considered if accuracy is to be achieved.
Electron Backscatter Diffraction (EBSD) of Sub 500 Nm Particles
Authors: Small J , Michael J
Published: July 2020

In our initial studies of the phase identification analysis of individual particles by EBSD, we observed that the quality of the EBSD patterns obtained from particles less than 1 micrometer in size decreased with decreasing particle size, density, and atomic number. This effect is shown in FIG. 1 by comparison of an EBSD pattern from a 12 um Al2O3 particle (FIG. la) and a 200 nm Al2O3 particle FIG. lb. Both particles were mounted on 2 mm thick carbon substrates. The Kikuchi bands from the larger particle are clearly visible while the bands from the smaller particle are not. This decrease in image quality is believed to be the result of a combination of 2 factors related to the electron scattering associated with these very small particles. First, as particle size decreases below about 1 micrometer, an increasing number of electrons are transmitted through the bottom of the particles.
TEM Characterization of Pseudotetragonal Mullite
Authors: Johnson Bradley R , Kriven Waltraud M
Published: July 2020

Mullite (3Al2O3•2SiO2) exists in a solid solution field (∼57-63 mol% Al2O3) as the only stable compound in the Al2O3•SiO2 phase diagram at ambient pressures. Equilibrium 3:2 mullite has an orthorhombic structure with b>a (o-mullite). However, when initially crystallized from molecularly mixed, 3:2 precursors at temperatures < 1200°C, the first phase that forms has lattice parameters with a ≈b. This structure is often termed pseudotetragonal mullite (pt-mullite), since even when the ‘a’ and ‘b’ lattice parameters are identical, they are symmetrically independent. Pseudotetragonal mullite has been shown to contain approx. 70 mol% Al2O3. with increasing time and temperature, the structure gradually assimilates the residual SiO2, and the lattice parameters change, such that by 1400°C, the material has attained its equilibrium structure and composition.

TEM was used to determine the spatial relationship between the crystalline phase and the residual, amorphous, SiO2-rich phase in pt-mullite. The starting materials were quenched, 3:2 mullite beads and fibers (made by containerless processing).
A Seasonal Record of Total Particulate Matter Embedded in Greenland Surface Snow
Authors: Kessler JD , Currie LA , Windsor ES , Newbury DE
Published: July 2020

Atmospheric aerosols are often investigated in order to gain insight into their effects on the global radiative heat budget, optical properties of the atmosphere, and their effects on human health. Characterizing the seasonal behavior of these aerosols is fundamental in understanding their climatological and air quality impacts. As part of a larger program to study the present and recent history of chemical species transported to Greenland, we analyzed a seasonal cycle of total aerosol matter scavenged from the air by surface snow.

During a “winter-over” experiment in Summit, Greenland, extending from June 1997 through March 1998, kilogram quantities of surface snow were collected, melted, and filtered onto high-purity quartz fiber filters in the field. Upon the receipt of these filters at NIST, the total particulate matter was removed from the filters and transferred to boron substrates with protocols involving resuspension, centrifugation, and filtration.’ Previous techniques that quantified multi-element particles used several different substrates.
Effect of Precipitates on the Recrystallization Behavior of Ti-Added If Steels
Authors: Choi Jae-young , Lee Hu-Chul
Published: July 2020

Because of its superior cold formability, a great amount of IF steels is being produced by many steel manufacturers. Accordingly, numerous efforts have been made to understand the mechanism of improved plastic strain ratio in Ti-added IF steels1“3. Several mechanisms have been proposed to explain the effect of Ti on the deep drawability of these steels: l)the scavenging effect that is removing carbon and nitrogen from the solution by fixing them as stable precipitates, 2)promotion of (111) texture by fine dispersion of TiC precipitates, and 3)effects of substitutional elements in solid solution4. in spite of these advantages, Ti-added ultra low carbon steels have a disadvantage of high recrystallization temperature. Hayakawa et al.5have reported that recrystallization temperature is sharply rises with the increase in titanium content and reaches a peak when solute titanium is nil, and the acute recrystallization temperature is lowered with the decrease in amount of fine TiC precipitates.
The Effect of Moore&s Law on the Growing Role of Transmission Electron Microscopy in the Semiconductor Industry
Authors: Mardinly John
Published: July 2020

TEM has been used for semiconductor device characterization since the 1980's, when Marcus and Cheng first demonstrated the feasibility and utility of applying TEM to semiconductors. The frequency of use of TEM has accelerated briskly due to the continual shrinkage of devices as predicted by Gordon Moore and now documented in the SIA roadmap (http://public.itrs.net/Home.htm). TEM use has also grown due to application of FIB techniques which make possible high precision cross-sections of specific structures. This relentless shrinking has resulted in difficulties in preparing suitable specimens. Many of the features and interfaces in a device may be curved rather than planar, and as the radius of curvature begins to approach the thickness of a TEM specimen, it can result in “geometrical blurring” of features, both for imaging and microanalysis. The origin of this blurring is illustrated in Figure 1, where it can be seen that a single electron may pass through two different features, and as a result, they are not resolved.
Microscopy in the Real World: A Manufacturer’s Perspective
Authors: Kersker Michael M
Published: July 2020

What in the “real” world does this title mean? I would argue that every paper given at this meeting in some way reflects an application in the real world, thus rendering this paper and this symposium redundant. But then again, here we are. of course, every one using an instrument will insist that his application is in some way unique and therefore not a common, mundane, “real-world” one. The “real-world” for an academically motivated scientist may be quite different from the “real-world” of the commercially motivated scientist. What happens in an asbestos testing lab is quite different from the activities of a consulting group using the microscope to solve industrial problems. Every application is “real world”...but they most certainly may be different.

And so, where to begin? For a start, consider the following “real world” situations: 1. a University using a microscope to support the research activities of that University,
Soil Colloids and Soil Organic Matter Associativity - the Basis of Soil Structure
Authors: Vrdoljak G , Sposito G
Published: July 2020

In the hierarchical model of soil structure, the lowest scale of structure is the combination of clays < 0.2 um diameter to form 2 um domains. to investigate the basis for soil structure, two highly weathered soils from Brazil (Oxisols) were selected and the < 2 um size fraction extracted by sedimentation for analysis. The first soil used in this study, classified as Xanthic Hapludox, was collected in 1991 at an EMBRAPA research station outside of Manaus, Brazil from a tropical forest site collected from the 0-8 cm depth. The second soil (0-20 cm depth) was sampled from a topographically flat area inside the Brasilia National Park, Brasilia D.F. Brazil by Dr. Flavio Vasconcelos.

The samples were analyzed by NMR spectroscopy, transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. NMR spectroscopy revealed the organic materials within this size fraction consisted predominantly of polysaccharides.
SEM Petrography of Hydrothermally Altered, Metamorphic Monazite in the Quetico Sub-Province of Northeastern Minnesota
Authors: Payne L , Ross L , Bauer R
Published: July 2020

Metasedimentary rocks of the Archean Quetico subprovince of the Superior province in northeastern Minnesota contain monazite that has undergone low-grade hydrothermal alteration and disseminated sulfide mineralization. The area contains multiply deformed, metasedimentary rocks with abundant granitic veins that were subjected to deep burial, deformation, and syntectonic Barrovian metamorphism ranging from kyanite-staurolite grade to sillimanite-muscovite grade. Continued deformation and concomitant granitic intrusion produced rapid decompression and a well-developed high-temperature, low-pressure thermal aureole adjacent to the granitic intrusive bodies. This second metamorphic event is characterized by mineral assemblages containing cordierite or andalusite after staurolite. Subsequent reburial of the area produced prennite/pumpellyite facies regional metamorphism that is widespread but only locally recognized.

The initial aim of this study was to determine the petrographic relationships between monazite, a light rare-earth phosphate, and the surrounding minerals as a basis for absolute age dating, by electron probe microanalyzer (EPMA), of deformation and related metamorphic events.
Electron Microscopic Investigation of FE-Rich Phyllosilicates
Authors: Ma Chi , Eggleton Richard A , Rossman George R
Published: July 2020

Green glauconite-like minerals from Weipa, Australia, which were previously known as glauconite, were determined to be unusual Fe-rich vermicuhte and Fe-rich smectite. This study revealed the structural and chemical nature of these unique phyllosilicates with HRTEM, AEM, SEM and XRD analysis.

The Fe-rich phyllosilicates comprising up to about 15 wt% of the rock occur with various amounts of quartz, mica, feldspar, low-Fe smectite, kaolinite, pyrite and siderite at about 30 meters depth in unweathered marine sediments of the Rolling Downs Formation at Weipa. The proportions of Fe-rich vermiculite and smectite decrease upward and become undetectable in the upper saprolite zone at about 23 m depth.

Two major morphologies of the Fe-rich phyllosilicates were observed. One is of tabular or granular detrital-shaped form (Fig.la); the other is platy or film-like, coating grains and occurring in matrix and fissures (Fig.lb).
Phase Transformations in an Austenitic Stainless Steel Weld During Postweld Heat Treatment
Authors: Burke M G , Nuhfer N T
Published: July 2020

The microstructural development in a Type 309 stainless steel weldment associated with a post-weld heat treatment of 30 h at 580°C has been studied using analytical electron microscopy (AEM). The purpose of post-weld thermal treatments is generally to relieve stresses within the weld, thereby improving performance. Microstructural stability during these thermal treatments is important for the weld; i.e., no deleterious phases should form. in this example, detailed microstructural analyses of a weldment in the as-welded and postweld heat-treated condition have been performed. Microstructural analyses were performed using Philips CM 12 and CM300-FEG analytical electron microscopes equipped with Oxford Instruments ISIS analyzers and LZ5 energy dispersive x-ray spectrometers, and a CM200-FEG analytical electron microscope equipped with a Gatan Image Filter (GIF).

As-Welded Condition:The microstructure of the weld was characterized by the presence of dislocated austenite (γ) and a network of delta (δ) ferrite.
Quantitative Thickness Measurements of Thin Oxides Using Low Energy Loss Filtered TEM Imaging
Authors: Pantel R , Sondergard E , Delille D , Kwakman LFTz
Published: July 2020

A technique for very thin silicon oxide measurements using energy filtered TEM (EFTEM) is presented and applied for BiCMOS technology optimization.

In advanced VLSI circuits, thin silicon oxide layers are used as critical part of active devices such as MOS or bipolar transistors (BiCMOS). Today the 2 nm thick gate oxides of the 0.12 urn generation MOS transistors can be controlled using high resolution TEM (HRTEM). However, for the next generations these measurements will become difficult or will necessitate Cs corrected microscopes'. For the NPN bipolar transistor very thin oxides (less than 0.5 nm) are used at the base-emitter interface to control the forward base (hole) current and improve the transistor current gain. This interface presents generally some roughness and the oxide control is impossible using HRTEM. in this communication we demonstrate a new technique for very thin oxide measurement using low loss energy filtered TEM (EFTEM).
Characterization of Semiconductors Grown in a Rotating Magnetic Field
Authors: Cochrane J , Carpenter P
Published: July 2020

Many different techniques have been used in attempts to minimize defects in single crystal semiconductors. This study examines semiconductors grown in the presence of a rotating magnetic field (RMF). The RMF method is commonly used in metallurgy to stir an electrically conducting liquid during the casting process which can reduce the effects of buoyancy driven convection and enhance the mass transfer process. The variation of heat and mass transfer processes by RMF can be controlled by selecting a specific frequency and strength of the magnetic field. Both numerical modeling and space-based crystal growth experiments using RMF indicate that the application of RMF to solidification of semiconductors will dramatically minimize defects and inclusions.

A ground based program in the Microgravity Research Division at NASA's Marshall Space Flight Center has been studying the effects of RMF on various semiconductor compounds grown by the traveling heater method (THM).