bluuebunny/crossref_metadata_2025_split huggingface dataset:
Architecture/environments for image processing: Hardware and software for the microscopist
Authors: Bright David S. 
Published: June 2020

Digital images are large arrays of data with array elements all treated in a similar way. “Architecures for image processing” immediately suggests parallel processors because of the enormous increase in speed. These processors enhance images in real time - TV rates - but this is less of a consideration where image collection takes more than a few seconds. Further, these machines are expensive and programming is difficult. For example, when the image is divided among processors as in Fig. 1 and 2, problems arise at the edges of the pieces. Issues such as cost, flexibility, ease of use and data integrity are often of more interest to the microscopist.Desktop computers present an ideal environment for off line processing of images with a few thousand pixels on an edge. These computers are adequately fast, they have sufficient storage and communication capability, and the software is less expensive than equivalent software for workstations or larger computers.
Three dimensional deblurring of transmitted-light brightfield micrographs
Authors: Bhattacharyya Santosh 
Published: June 2020

Three dimensional microscopic structures play an important role in the understanding of various biological and physiological phenomena. Structural details of neurons, such as the density, caliber and volumes of dendrites, are important in understanding physiological and pathological functioning of nervous systems. Even so, many of the widely used stains in biology and neurophysiology are absorbing stains, such as horseradish peroxidase (HRP), and yet most of the iterative, constrained 3D optical image reconstruction research has concentrated on fluorescence microscopy. It is clear that iterative, constrained 3D image reconstruction methodologies are needed for transmitted light brightfield (TLB) imaging as well. One of the difficulties in doing so, in the past, has been in determining the point spread function of the system.We have been developing several variations of iterative, constrained image reconstruction algorithms for TLB imaging. Some of our early testing with one of them was reported previously. These algorithms are based on a linearized model of TLB imaging.
Some problems and solutions in electron energy loss spectroscopy of cryosections
Authors: Shao Zhifeng , Ho Ruoya , Somlyo Andrew P. 
Published: June 2020

Electron energy loss spectroscopy (EELS) has been a powerful tool for high resolution studies of elemental distribution, as well as electronic structure, in thin samples. Its foundation for biological research has been laid out nearly two decades ago, and in the subsequent years it has been subjected to rigorous, but by no means extensive research. In particular, some problems unique to EELS of biological samples, have not been fully resolved. In this article we present a brief summary of recent methodological developments, related to biological applications of EELS, in our laboratory. The main purpose of this work was to maximize the signal to noise ratio (S/N) for trace elemental analysis at a minimum dose, in order to reduce the electron dose and/or time required for the acquisition of high resolution elemental maps of radiation sensitive biological materials.Based on the simple assumption of Poisson distribution of independently scattered electrons, it had been generally assumed that the optimum specimen thickness, at which the S/N is a maximum, must be the total inelastic mean free path of the beam electron in the sample.
Determination of nucleic acid content of viruses by electron spectroscopic imaging and correlation averaging
Authors: Misra M. , Conway J. F. , Trus B. L. , Steven A. C. 
Published: June 2020

Energy filtering offers the potential to form element-specific images, and thus to quantitate and map various elements in biological specimens. To assess the sensitivity and reproducibility with which we can detect phosphorus using current technology, we have performed ESI experiments in a model system comprising three well-characterized viruses - tobacco mosaic virus (TMV), LA virus of yeast, and bacteriophage T4 - that differ widely in their contents and spatial distributions of nucleic acid. Here we make a preliminary report of experiments in which the data were recorded in a Zeiss EM902 electron microscope equipped with a Henry-Castaing energy filter.An aliquot of the viral mixture was adsorbed to a thin, grid-mounted, carbon film, blotted to a thin film, rapidly frozen in liquid ethane, and transferred into the microscope in the frozen-hydrated state, where it was freeze-dried at 100°K. A SIT camera was used to record images at energy losses of 105, 120 and 150 eV respectively, with an energy window of 10eV.
Quantitative magnetic imaging in STEM using DPC
Authors: McFadyen Ian R. 
Published: June 2020

Magnetic domains can be imaged by a number of techniques in the transmission electron microscope. These techniques rely on the Lorentz force and are thus known collectively as Lorentz microscopy. More accurately the interaction of a fast electron with the magnetic induction of a sample can be described as a change in the phase of the electron wave where the phase gradient is given by:

where e is the electron charge, h is Plank’s constant, is the magnetic induction and is the unit vector along the electron trajectory. The integration from - ∞ to ∞ takes into account the magnetic stray fields in addition to the magnetic induction within the sample itself.Magnetic samples can therefore be regarded as phase objects and the magnetic structure can be revealed by phase contrast techniques and at best one could hope to get a map of the phase gradient which is linearly related to the integrated induction.
Modifications of a JEOL 2000EX TEM for insSitu surface studies
Authors: Marshall Michael T. , Tong Xianghong , Murray Gibson J. 
Published: June 2020

We have modified a JEOL 2000EX Transmission Electron Microscope (TEM) to allow in-situ ultra-high vacuum (UHV) surface science experiments as well as transmission electron diffraction and imaging. Our goal is to support research in the areas of in-situ film growth, oxidation, and etching on semiconducter surfaces and, hence, gain fundamental insight of the structural components involved with these processes. The large volume chamber needed for such experiments limits the resolution to about 30 Å, primarily due to electron optics. Figure 1 shows the standard JEOL 2000EX TEM. The UHV chamber in figure 2 replaces the specimen area of the TEM, as shown in figure 3. The chamber is outfitted with Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Residual Gas Analyzer (RGA), gas dosing, and evaporation sources. Reflection Electron Microscopy (REM) is also possible. This instrument is referred to as SHEBA (Surface High-energy Electron Beam Apparatus).The UHV chamber measures 800 mm in diameter and 400 mm in height. JEOL provided adapter flanges for the column.
Quantitative analysis of low-dose high-resolution images and diffraction patterns from zeolites using a slow-scan CCD camera
Authors: Pan M. , Crozier P.A. 
Published: June 2020

Zeolites are an important class of low-density aluminosilicates framework structures with applications to the field of catalysis and molecular sieves. In order to understand die origin of die unique properties of these materials and hence optimize their performance, it is essential to have a detailed description of their structures. Zeolite structure is often described in terms of the secondary building unit (SBU) which is a specific configuration of the SiO4 tetrahedrons. Structure determination of zeolites is then reduced to determine the types of SB Us and their connectivities when forming the 3-D framework structure.It has been recognized that zeolites undergo rapid structural damage under electron beam irradiation. The use of a slow-scan CCD camera to record low-dose high resolution electron microscope (HREM) images from zeolites with the combination with real-space averaging techniques has been shown to be successful in obtaining the averaged unit cell with high signal-to-noise ratio (SNR).
Measurements of Debye-Waller factors in TiAl from energy-filtered HOLZ line intensities
Authors: Holmestad R. , Weickenmeier A. L. , Zuo J. M. , Spence J.C.H. , Horita Z. 
Published: June 2020

This paper reports a new method to measure Debye Waller factors. The measurements are required for subsequent structure factor refinement in TiAl. The procedure is to obtain a large angle CBED pattern near a sparse zone axis, extract line scans along HOLZ lines from this pattern and use two beam intensity calculations to fit experiment and simulation by varying the Debye Waller factors. Unlike earlier work, we have used non-systematic reflections. The material studied is γ−TiAl (50-50), made from 25g ingots produced by arc-melting in an argon atmosphere, and homogenized for 1 day at 1473 K. Specimens were thinned by twin-jet electropolishing.Elastic energy filtered patterns are required for accurate quantitative comparisons between experiment and theory. A Zeiss 912 Omega TEM/STEM electron microscope was used to obtain energy filtered CBED patterns, fitted with an Omega imaging energy filter, which forms images or diffraction patterns within any desired energy loss range.
Rapid preparation of semiconductor cross sections for TEM analysis
Authors: Benedict John , Anderson Ron , Klepeis Stanley J. 
Published: June 2020

Semiconductor manufacturers examine cross sections of their semiconductor devices to check the quality and integrity of their product. The growing complexity and diminishing size of these devices has caused manufacturers to increasingly rely on the resolving and analytical capabilities of TEM. The manufacturers' requirements for TEM analysis are: high specimen preparation spatial resolution (preparation of a specific area, usually less than 0.5 microns in size), a large sample area (at least 0.5 mm) available for examination, and a short sample preparation time (e.g. several hours). To meet these needs we have developed a technique for rapid preparation of cross sections for TEM analysis.The specific area to be cross sectioned on the sample is identified by marking it with a laser or Focused Ion Beam (FIB) tool. The sample is then cut down to a 3 x 6 mm rectangle with the area of interest in the center. This rectangle is mounted using wax onto a Tripod polisher with the area of interest protruding over the edge of the polisher.
CBED study of low-temperature InP grown by gas source MBE
Authors: Rajesh R. , Kim M.J. , Bow J.S. , Carpenter R.W. , Maracas G.N. 
Published: June 2020

In our previous work on MBE grown low temperature (LT) InP, attempts had been made to understand the relationships between the structural and electrical properties of this material system. Electrical measurements had established an enhancement of the resistivity of the phosphorus-rich LT InP layers with annealing under a P2 flux, which was directly correlated with the presence of second-phase particles. Further investigations, however, have revealed the presence of two fundamentally different types of precipitates. The first type are the surface particles, essentially an artefact of argon ion milling and containing mostly pure indium. The second type and the one more important to the study are the dense precipitates in the bulk of the annealed layers. These are phosphorus-rich and are believed to contribute to the improvement in the resistivity of the material.The observation of metallic indium islands solely in the annealed LT layers warranted further study in order to better understand the exact reasons for their formation.
Lateral dopant profiling of submicron VLSI device structures using scanned-probe microscopy
Authors: Slinkman J. A. 
Published: June 2020

Present day very large scale integrated circuit (VLSI) technology requires accurate knowledge of the spatial extent in three dimensions (3D) of active impurity dopants which have been purposely incorporated into the device structures. The active region of a typical device, where most electrical conduction is confined, is engineered to contain dopants such as As, B, or P in a concentration range of 1015 to 1020 cm−3. It is necessary to control the variation of the dopant "profiles" to a resolution of 100 nm for device reliability. The devices themselves occupy a footprint of, typically, 10 um2.Except in 1D, it has been impossible to achieve a high degree of precision in the metrology of dopant profiles in actual device structures. Existing methods which have been developed for 2D dopant profiling, such as junction-staining or TEM, generally yield only qualitative information and are destructive measurements. Secondary ion mass spectrometry (SIMS) yields quantitative data but the technique is time and labor intensive, but it, too, is destructive.
Reflection electron microscopy of triangular quantum wells
Authors: Gajdardziska-Josifovska M. 
Published: June 2020

Asymmetric triangular quantum wells (ATQW) have recently been developed to improve the absorption and emission characteristics of opto-electronic devices. A triangular compositional gradient is produced during epitaxial growth of AlxGa1-xAs on GaAs by either continuous variation of x or by alternate deposition of thin layers of the two compounds where the ratio of the layer thickness produces an average alloy composition. The knowledge of the compositional profile of the actual ATQW, as derived from HREM, has proven essential for the description of the photo-emission properties of the device. Recently, the technique of reflection electron microscopy has also been applied to multiple rectangular quantum wells of GaAs/AlxGa1-xAs with the encouraging result that layers with 1% Al can be distinguished from the GaAs layers. In this work we investigate the applicability of REM to characterization of ATQW.Triangular quantum wells were grown by MBE, employing the digital alloy method. Fig. 1 shows a schematic representation of the nominal thickness and composition of the studied ATQW.
The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film
Authors: Barmak K. 
Published: June 2020

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.
Microstructural characterization of a corrosion-resistant hydrotalcite coating on aluminum
Authors: Drewien C. A. , Hills C. R. , Buchheit R. G. 
Published: June 2020

Aluminum-lithium-hydroxycarbonate hydrate (Li2Al4CO3(OH)12*3H2O) or hydrotalcite coatings are novel corrosion resistant coatings being considered for replacement of environmentally sensitive chromate conversion coatings. Hydrotalcite coatings provide corrosion protection to aluminum alloys used in atmospheric environments. In order to model the electrochemical corrosion behavior and to assess the impact of changing processing variables on the overall corrosion performance, a detailed baseline characterization of the microstructure was required.Hydrotalcite coatings were formed by immersion of an 1100 aluminum alloy into a room temperature, alkaline bath of lithium carbonate and lithium hydroxide for 15 minutes. Microstructural characterization of the coating was performed using both scanning (SEM) and transmission (TEM) electron microscopy. In Figure 1a, the secondary electron image of the surface, obtained on a JEOL 6400 SEM operated at 15 kV, reveals a porous network of hydrotalcite crystals oriented perpendicular to the plane of viewing. In order to determine whether the pores were continuous to the substrate and to provide further characterization, crosssectional TEM was performed.
Copper enrichment on Al 2024 surface after de-oxidizing treatment
Authors: Drewien C. A. , Buchheit R. G. , Zavadil K. R. , Neil T. E. 
Published: June 2020

Coatings of lithium-aluminum-carbonate-hydroxide are being developed for corrosion protection of aluminum alloys against atmospheric and saline environments. Coating is performed by immersion of the aluminum part into a lithium carbonate-lithium hydroxide solution of pH=11.5. Before coating, the aluminum alloy is degreased in trichloroethylene, cleaned in a sodium carbonate-sodium silicate bath, and de-oxidized in nitric acid containing ammonium biflouride. Coating of most aluminum alloys is easily accomplished, and the coatings pass the ASTM B117 salt spray test. However, aluminum alloys that contain copper, specifically 2024-T3 and 7075-T6, yield coatings that fail the salt spray test, i.e. pitting and general corrosion is observed. Photographs of coatings after 168 hr salt spray exposure are shown in Figure 1 for Al 1100 and 2024-T3 alloys. A study has been undertaken to determine the influence of copper upon the corrosion properties of the coating.The surface of 2024-T3 was analyzed after each processing step in order to determine if copper enrichment at the specimen surface was occurring.
Imaging nanostructures on ablated kapton polymide
Authors: Callahan Daniel L. , Phillips H. M. , Sauerbrey R. 
Published: June 2020

Excimer laser irradiation has been used to interferometrically ablate submicron line patterns on to Kapton polyimide. Such patterned material may exhibit highly anisotropic conduction as was predicted from previous studies showing enhanced conductivity from uniformly ablated material. We are currently exploiting this phenomenon to create integrated devices using conventional polymers as both dielectrics and conductors. Extensive scanning electron microscopy (SEM) and limited transmission electron microscopy (TEM) have been conducted in order to characterize the morphology of such patterned nanostructures as a function of processing conditions.The ablation technique employed produces an interference pattern on the polymer surface of period equal to half that of a diffraction grating period, independent of the laser wavelength. In these experiments, a 328 nm grating has been used to produce line patterns of 164 nm line-spacings as shown in Figures 1 and 2. A 200 Å Au coating has been used to both prevent charging and, perhaps more importantly, enhance contrast.
The morphology and structure of a rod-coil polymer and its molecular object derivatives
Authors: Li L. S. , Stupp S. I. 
Published: June 2020

Several non-crystalline ordered structures are known in polymer science; these include liquid crystalline structures and long range ordered microdomain structures of amorphous block copolymers with well defined block lengths. It would be very interesting to combine these two types of structures together to form a block copolymer in which a rigid board-like or rod-like mesogen block is connected to a coil-like chain. These copolymers, containing a mesogenic block and a short block of polyisoprene (PI), polystyrene (PS) or a diblock sequence have been synthesized in our laboratory. The chemical structure of one of the copolymers is shown below:If a molecular object, such as molecular sheet or rod could be formed through microphase separation and cross-linking among the PI blocks, a nanocomposite with liquid crystalline, rubbery and glassy regions could be formed. In order to reveal the morphology and structure of the rod -coil copolymer and its molecular object we studied the copolymer using electron microscopy and electron diffraction techniques.
Grain boundaries in silicon nitride
Authors: Chowdhury K Das , Carpenter R. W. , Braue W. 
Published: June 2020

Research on whisker/matrix interfaces and matrix grain boundaries in Si3N4 and Al2O3 composites reinforced with SiC whiskers by HREM imaging have shown that disordered layers exists in these regions. The disordered interfacial regions are often considered amorphous layers, particularly when they are thicker than ∼1nm. They appear to be discontinuous in the whisker/matrix interfaces and continuous in matrix grain boundaries. Thin amorphous layers in composites and conventionally synthesized ceramics, particularly those based on Si3N4, are expected to contain oxygen from sintering aids and powder particle surface impurities. In this paper we report the results of an investigation of silicon nitride matrix grain boundaries in Si3N4/SiC(w) composites (CMC) and polycrystalline CVD silicon nitride, using very high spatial resolution position resolved EELS and HREM imaging. Interfaces between SiC and silicon nitride in CMC materials have been discussed elsewhere.The CMC's were prepared by pressing and presintering Toyo-Soda α-silicon nitride (TS10) powder with 5.5 wt% Yttria and 1.1 wt% Alumina as sintering aids and 20 vol% β-SiC Huber whiskers at 1500°C in 0.1MPa Argon.
Structures of chemically stabilized ceramics
Authors: Gai Pratibha L. , Saltzberg M. A. , Hanna L.G. , Winchester S.C. 
Published: June 2020

Silica based ceramics are some of the most fundamental in crystal chemistry. The cristobalite form of silica has two modifications, α (low temperature, tetragonal form) and β (high temperature, cubic form). This paper describes our structural studies of unusual chemically stabilized cristobalite (CSC) material, a room temperature silica-based ceramic containing small amounts of dopants, prepared by a wet chemical route. It displays many of the structural charatcteristics of the high temperature β-cristobalite (∼270°C), but does not undergo phase inversion to α-cristobalite upon cooling. The Structure of α-cristobalite is well established, but that of β is not yet fully understood.Compositions with varying Ca/Al ratio and substitutions in cristobalite were prepared in the series, CaO:Al2O3:SiO2 : 3-x: x : 40, with x= 0-3. For CSC, a clear sol was prepared from Du Pont colloidal silica, Ludox AS-40®, aluminium nitrate nonahydrate, and calcium nitrate hexahydrate in proportions to form a final composition 1:2:40 composition.
Ion mixing of thin ZrO2 films on α-Al2O3 by Cr+ or Kr+ ions
Authors: Evans N. D. , Joslin D. L. , McHargue C. J. 
Published: June 2020

Analytical electron microscopy (AEM) has been used to study ion beam mixing in an oxide-oxide system: ZrO2 thin films on α-Al2O3. This mixing process is useful in applications such as adhesion enhancement.Films of ZrO2 (∼80 nm thick) were deposited on α-Al2O3 by radio frequency (rf) sputter deposition and annealed for 2 h at 500°C in 96%Ar+4%H2 to remove excess oxygen. Samples were bombarded at room temperature with either 340 keV Cr+ or 475 keV Kr+ ions to a fluence of 4×1012 ions/m2. An area of each specimen was masked during implantation to permit analysis of unimplanted interfaces. Specimens for AEM were mounted in cross-section, ground and dimpled to a thickness of ∼20 μm, and Ar+ ion milled to electron transparency. Specimens were sputter-coated with ∼5 nm of carbon to reduce charging effects. The AEM was performed in a Philips EM400T/FEG operated in the scanning transmission mode with a probe diameter of <2 nm (FWTM prior to beam spreading).