bluuebunny/crossref_metadata_2025 huggingface dataset:
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).
Fast calibration of CBED patterns for quantitative analysis
Authors: Gribelyuk M.A. , Rühle M.
Published: June 2020

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.
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.
Growth of Si on Ge(001)2×l by gas-source molecular beam epitaxy
Authors: Xiao H.Z. , Tsu R. , Robertson I.M. , Birnbaum H.K. , Greene J.E.
Published: June 2020

The growth of SiGe strained-layer superlattices (SLS) has been received considerable attention due to the electronic and optoelectronic properties of these layers. In addition, these structures offer tantalizing possibilities for "band gap engineering" through the use of strain and chemically ordered alloys. The remaining barriers to grow the SiGe SLS structures with high quality result from the generation of large densities of defects, such as dislocations, twins, stacking faults, etc., at the heterointerfaces arising from the misfit strain relaxation. Other problems associated with the growth of the SiGe SLS structures are segregation and low incorporation of the dopants and inter-diffusion of Si and Ge. In the present study, the inter-mixing of Si and Ge and the generation of the defects in Si epilayers grown on Ge(001)2×1 at 550 °C by gas-source molecular beam epitaxy (MBE) from Si2H6 were studied using transmission electron microscopy (TEM), in-situ reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM) and electron energy-loss spectroscopy (EELS).
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.
X-ray microscopy in polymer science: Prospects of a new imaging technique
Authors: Ade H. , Hsiao B. , Mitchell G. , Cameron S. , Costello S.
Published: June 2020

The ultimate bulk and surface properties of heterophase polymers are strongly tied to their morphology. Light and electron microscopies are often successfully used to characterize such morphologies, but these techniques are inherently limited in their applicability and versatility. We present a new, relatively non-invasive imaging technique which employs highly focused, tunable x-rays that can be used to investigate the surface and bulk characteristics of heterophase polymeric materials with chemical and orientational sensitivity. In X-ray Absorption Near Edge Structure (XANES) imaging, a highly monochromatic soft x-ray beam is focused onto the sample, and the transmitted flux through a thin specimen is collected to produce images with presently 55 nm Rayleigh resolution on the X1A beamline at the National Synchrotron Light Source. With judicious choice of photon energy, the technique is sensitive to the chemical (valence) state and local orientation of each component present and is, for instance, capable of distinguishing among chemical functionalities such as C-C, C≡C, C=O, COOH, and C≡N.
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.
Electron spectroscopy of ceramics
Authors: Dravid Vinayak P. , Wang Yun-Yu , Zhang Hong
Published: June 2020

High resolution, analytical and conventional TEM techniques/analyses have had considerable impact on ceramic science and engineering. Recently, the focus is shifted to the use of less traditional such as transmission EELS and novel techniques such as electron holography, STM, AFM etc.. In this contribution we illustrate the power and potential for transmission EELS in high spatial/energy resolution analysis of charge carriers in ceramic superconductors. Traditionally, optical and x-ray spectroscopies have been successfully utilized to probe the electronic structure of solids. The oxide superconductors, however, are marred by inhomogeneity of structure, chemistry and consequently the electronic structure. Thus, though very powerful, dedicated EELS has its limitations. Furthermore, these compounds possess highly anisotropic crystal and electronic structure. As an alternative, we have demonstrated that our 200 keV Hitachi HF-2000 cFEG TEM offers adequate energy, momentum transfer (q) and spatial resolution (< 0.5 eV at zero loss, ∼ 0.10Å-1 and < 1-2 nm, respectively) to realistically address these issues.
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).
Three-fold astigmatism: An important TEM aberration
Authors: Krivanek O.L. , Leber M.L.
Published: June 2020

Three-fold astigmatism resembles regular astigmatism, but it has 3-fold rather than 2-fold symmetry. Its contribution to the aberration function χ(q) can be written as:

where A3 is the coefficient of 3-fold astigmatism, λ is the electron wavelength, q is the spatial frequency, ϕ the azimuthal angle (ϕ = tan-1 (qy/qx)), and ϕ3 the direction of the astigmatism.

Three-fold astigmatism is responsible for the “star of Mercedes” aberration figure that one obtains from intermediate lenses once their two-fold astigmatism has been corrected. Its effects have been observed when the beam is tilted in a hollow cone over a wide range of angles, and there is evidence for it in high resolution images of a small probe obtained in a field emission gun TEM/STEM instrument. It was also expected to be a major aberration in sextupole-based Cs correctors, and ways were being developed for dealing with it on Cs-corrected STEMs.
Applications of TEM to microstructure, epitaxy, and preferred orientation in magnetic thin films
Authors: Parker Michael Andrew
Published: June 2020

J. Kent Howard, some years ago, published an extensive review of the phenomenon of what he referred to as “grain-to-grain” or “polycrystalline” epitaxy in thin films. Of the six or so different applications of this phenomenon, from superconductors to magnetics, none has greater technological significance than applications to magnetic thin films. This derives from the magnetic anisotropy of these thin films which has such a profound influence on their magnetic properties. In particular, magnetocrystalline anisotropy is often used to engineer thin films with the desired orientation of the easy axis of magnetization for magnetic record ing media applications. Magnetocrystalline anisotropy is intimately connected to the the crystallographic preferred orientation of the grains composing the magnetic layer which can be controlled through the skillful use of epitaxy with a suitable sublayer. The techniques of AEM, especially elongated probe microdiffraction (EPMD), have proven themselves invaluable for characterizing the micro-structure of such thin films.
Flux-line observation by electron Holography
Authors: Tonomura Akira
Published: June 2020

In electron microscopy, the intensity of an electron beam transmitted through an object can be observed. While in electron holography, the phase of the electron beam can also be observed and displayed as an interference micrograph. Using a technique unique to holography, the precision of phase measurements can be increased to 1/100 of the electron wavelength. An interference micrograph of a magnetic object can be interpreted in a straightforward way: Contour fringes directly indicate projected magnetic flux lines and a constant magnetic flux of h/e (= 4 × 10-15 Wb) flows between two adjacent fringes (See Fig. 1).

Examples of magnetic recordings are shown in Fig. 2. Flux lines inside and outside of the magnetic tapes, recorded in different ways, can directly and quantitatively be observed as interference micrographs. Figure 2 (a) shows an example of in-plane magnetic recording. Two magnetization streams, pointed in opposite directions, merge and produce vortices in the transition region similar to those produced by streams of water.
Microscopy of magnetic materials using an optimised FEG CTEM/STEM instrument
Authors: Chapman J N , Ferrier R P , Bormans B
Published: June 2020

Modern magnetic materials, as well as being of major scientific interest, are being developed intensively for a wide range of technological applications To achieve superior properties great attention is devoted to the ways in which materials are produced in that many of the desirable attributes are induced by a particular growth process rather than being intrinsic to the material itself. Thus development of enhanced macroscopic properties requires that the magnetic microstructure be determined and its dependence on the physical microstructure understood. Furthermore, the information needed is not restricted to the materials in their as-grown state but on how they are affected by application of magnetic fields and changes in temperature.

To satisfy all these requirements a highly modified electron microscope has been developed. The main criteria it had to fulfill were: (i) sufficient room around the specimen to house a small “micromagnetic laboratory” to allow a range of in-situ experiments to be undertaken
TEM examination of the magnetic domain boundaries in a duplex austenitic- ferritic stainless steel
Authors: Fourlaris G. , Gladman T.
Published: June 2020

Duplex austenitic- ferritic stainless steels (DSS) offer significant advantages when compared to standard austenitic stainless steels, in several areas of industrial applications, due to their higher mechanical strength, superior resistance to corrosion and a lower price because of their lower nickel content. Despite the extensive research carried out so far in the area of DSS the characterisation of their magnetic properties, under stress or under a static field, has attracted significantly less attention. This is contrary to the fact that in certain naval constructions the suitability of a given type of steel is judged not only by its tensile, impact, and corrosion properties but also by its magnetic behaviour.

A 2205 type austenitic- ferritic DSS has been cold rolled to different cold rolling reductions, with an aim of achieving a 0.2 % proof strength of at least 700 MPa with an elongation value of greater than 20%.
Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM
Authors: Liu J. , Pan M. , Spinnler G. E.
Published: June 2020

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.
Focus-variation image reconstruction in field-emission TEM
Authors: Coened W.M.J. , Janssend A.J.E.M. , Op de Beeck M. , Van Dyck D. , Van Zwet E.J. , Zandbergen H.W.
Published: June 2020

The use of a field emission gun (FEG) in high resolution TEM (HRTEM) improves the information limit much below the point resolution. This is due to the FEG’s high brightness and low energy spread which yield a very good coherence. In the area between point and information resolution of the FEG-TEM, image interpretation is complicated by the lens aberrations and focus effects, which cause scrambling of the information from the specimen. This problem is solved by ‘holographic’ techniques, which retrieve aberration-corrected amplitude and phase information of the electron wave ϕ at the exit plane of the specimen. We follow the route of ‘in-column’ or ‘nonlinear’ holography by digital processing of a focal series of HRTEM images. Different reconstruction algorithms can be used for that purpose depending on the assumptions that are made in the HRTEM imaging model. We have devised two workable algorithms. A first method, called the “paraboloid method” (PAM), aims at filtering out recursively the nonlinear contributions in the images, so that high-speed linear reconstruction can be applied.
Optical characteristics of the hitachi HF-2000 cold field-emission TEM
Authors: Allard L. F. , Völkl E. , Nolan T. A.
Published: June 2020

The illumination system of the cold field emission (CFE) Hitachi HF-2000 TEM operates with a single condenser lens in normal imaging mode, and with a second condenser lens excited to give the ultra-fine 1 nm probe for microanalysis. The electron gun provides a guaranteed high brightness of better than 7×l08 A/cm2/sr, more than twice the guaranteed brightness of Schottky emission guns. There have been several articles in the recent literature (e.g. refs.) which claim that the geometry of this illumination system yields a total current which is so low that when the beam is spread at low magnifications (say 10 kX), the operator must “keep his eyes glued to the binoculars” in order to see the image. It is also claimed that this illuminating system produces an isoplanatic patch (the area over which image character does not vary significantly) at high magnification which is so small that the instrument is ineffective for recording high resolution images.
Study of cobalt oxide films deposited on single-crystal yttria-stabilized zirconia by pulsed-laser ablation
Authors: Ramamurthy Sundar , McKernan Stuart , Barry Carter C.
Published: June 2020

One of the most common applications of pulsed-laser ablation (PLA) is the production of oxide films of almost any stoichiometry. In this work, thin films of cobalt oxide were grown onto single-crystal yttria-stabilized zirconia (YSZ) substrates of (100) orientation. Film morphology during the early stages of growth has been studied.

Cobalt oxide films grown on suitable substrates have potential applications in electronic and magnetic devices. Like most transition metal oxides, cobalt oxide exists in more than one form, depending on the valence of the cations and their distribution . The transition from CoO to Co3O4 occurs at about 900°C in air, CoO being the high-temperature phase. However, by lowering the partial pressure of oxygen, the CoO stability region shifts down to much lower temperatures.

The laser system used for the depositions was a Lambda Physik model 210i with KrF excimer laser (λ=248 nm) operating at an energy of 200 mJ per pulse. A Co3O4 pellet (96% dense) was fabricated as the target material.
A pseudo threefold helical structure found in silk Langmuir-Blodgett films by electron diffraction
Authors: Zhang Weiping , Gido Samual P. , Muller Wayne S. , Fossey Stephen A. , Kaplan David L.
Published: June 2020

The high performance tensile properties of silkworm (Bombyx mori) silk fiber has resulted in a long standing interest in the semicrystalline morphology of this material. The properties of silk fiber depend not only on the chemical composition (primary protein structure) but also on the fiber spinning conditions present in the silk gland which induce the formation of a (β-sheet based crystalline morphology (secondary protein structure). Knowledge of the silk structure is essential for understanding how the natural spinning processes results in such excellent material properties, but surprisingly few experimental results are available concerning the detailed structures of silk proteins. Two β-sheet based silk fibroin crystalline structures (e.g. silk I and silk II) have been studied by many authors, but the silk I structure remains largely uncharacterized. Here we report results from thin silk films prepared by the Langmuir-Blodgett (LB) technique which display a new silk fibroin structure with a threefold helical chain conformation.
Three hundred years after Hooke and Van Leeuwenhoek: The revolution in optical microscopy
Authors: Isaacson M.
Published: June 2020

Man is always trying to extend his vision through the four senses of sight, sound, touch and smell. The microscopy of Hooke and van Leeuwenhoek are examples of methods devised centuries ago to extend our visible vision. In fact, instrument designers have constructed microscopes using each one of the four senses to bring us peeks into the microworld. When Robert Hooke took some scrapings from his teeth and viewed the bacteria in these scrapings under his primitive microscope, a whole new view of the world ensued. But it should be noted that optical microscopes used two centuries after Hooke were not much different than the primitive 17th century versions. It was the illucidation of modern optics principles by Abbe and then Zernicke that allowed for the design of most present-day conventional optical microscopes and revolutionized the microscopy of their day. Even after that revolution, the laws of physics seemed to prevent imaging structures significantly smaller than the wavelength, λ, and this led to the search for other methods to increase resolution.
Scanning tunneling microscopy of the topology of vapour-deposited and electro-deposited metal films
Authors: Liu J.B. , Clark Boyd , Duan J.Z. , Fisher R.M.
Published: June 2020

The fracture and subsequent spontaneous delamination of thin metal films under the influence of excessive internal stresses, resulting from low temperature deposition and processing, can be extremely deleterious to the long term serviceability of IC devices. The conditions for fracture are determined by the magnitude of the residual stress, which can be measured by x-ray diffraction techniques, the fracture toughness of the thin film material and the size of any internal or sinface flaws that may be present.

In order to establish the size and depth of microcracks at the surface, high resolution scanning (SEM) and transmission electron microscopy (TEM) and scanning tunneling microscopy (STM) are being used to define the topology of the surfaces of vapour-deposited films for comparison with electroplated films of the same metal. Direct knowledge of the surface relief is required to predict the onset of through-thickness cracking or to derive the fracture energy of the film material by detecting the critical conditions for cracking. Detailed knowledge of surface structures also is useful for understanding the mechanisms of film growth, including information on the crystallography of surface facets and growth steps.
Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors
Authors: Peters Klaus-Ruediger
Published: June 2020

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.
Small, cool lenses
Authors: Crewe Albert V.
Published: June 2020

The potential advantages of small magnetic lenses are well-known and obvious and many attempts have been made to make such lenses. Previous work has been adequately summarized in an excellent article by Mulvey who covered most of the ground. This paper can be considered to be just a small addendum to that publication. As often happens surprises occur when we combine two different concepts.

If we consider an annular shaped coil (Fig. 1a) we can easily relate the power consumption to the ampere turns by a simple integration. Inserting some practical values, we obtain

and we see that the power consumption does not depend upon the radius directly, only by virtue of the ratio r2/r1.

We can make the coil into a lens very simply by wrapping it in iron (Fig. 1b). In the case of a thin lens (e.g. for an SEM) the focal length depends upon the value of s and the magnetic field and it is possible to combine these expressions to obtain
Development of a 200kV field emission TEM
Authors: Isakozawa S. , Kashikura Y. , Sato Y. , Takahashi T. , Ichihashi M. , Murakoshi H.
Published: June 2020

We have completed development of a 200kV field emission TEM. Fig. 1 is a general view of the instrument showing the electron gun and illumination lens system. The electron gun is reported in a separate paper in details. The high voltage accelerator is of 6-stage with aluminum oxide insulators. It allows stable 200kV operation achieving a voltage stability of 1.5 х 10−6/min. The field emitter is a polished tungsten tip having a crystal orientation of (310). It is operated at an ambient temperature without heating. The illumination lens system has been designed and built with permalloy to suite the small virtual source and to minimize external magnetic field disturbances. The objective lens has been designed to allow a point resolution of 0.23 nm and a small probe of 1 nm diameter. The probe has an intensity of 1 х 109A/cm2 sr. or higher as measured on the specimen.
3-D reconstruction of biological material from serial section and stereo modeling
Authors: Mastronarde David , McDonald Kent , McIntosh J. Richard
Published: June 2020

Stereo visualization of biological fine structure has long been useful for the appreciation of three-dimensional structure in high voltage electron micrographs of thick specimens. Quantification of specimen geometry by this method is difficult, however, since reproducible placement of a 3-D cursor in a gray-scale object with a single pair of stereo views is difficult. Serial thin sectioning and electron microscopy has been used to obtain quantitative three-dimensional information about biological structures, but when high resolution is required, serial section tracking can be problematic because distortions of as much as 5% between successive sections are common, impeding section alignment and reliable 3-D reconstruction.

We are experimenting with computer image processing methods to overcome the above mentioned difficulties. A MicroVax III hosting a Parallax board set is being used to process images obtained from electron micrographs with a DAGE -81 video camera and displayed on a Mitsubishi high resolution color monitor.
High-resolution z-contrast imaging of YBa2Cu3O7-δ grain boundaries
Authors: Chisholm M. F. , Pennycook S. J.
Published: June 2020

A rapid reduction of the critical current density across grain boundaries with increasing tilt angle up to ∽10° has been observed in YBa2Cu3O7−δ superconductors. These results fit nicely with an investigation of the structure of low-angle tilt boundaries in these materials. The boundaries are observed to be composed of an asymmetric array of dislocations with a Burgers vector of 1.17 nm for [100] tilt boundaries (Fig. 1) and 0.389 nm for [001] tilt boundaries. It is observed that at 7.5° tilts, the dislocation cores begin to overlap (Fig. 2). Increasing the tilt angle beyond this value is not expected to significantly change the boundary structure which corresponds closely to the point where tilt angle had little further effect on critical current. A complication which was not completely addressed in the study of the structure of these low-angle boundaries is that ceramic materials have a strong tendency to form thin intergranular glass phases and to exhibit enhanced segregation of impurities to the grain boundaries. Conventional transmission electron microscopy and x-ray microanalysis with emitted photons using an energy dispersive spectrometer is of questionable use for this application. A new method for forming high resolution images with strong chemical sensitivity using large-angle elastically scattered electrons in a scanning transmission electron microscope has been used in this study to directly address the grain boundary segregation question.
Observation of the quantum size effect in the STEM
Authors: Ouyang F. , Isaacson M.
Published: June 2020

The study of small particles or microclusters has been very active in recent years. When the particle size becomes smaller, its electronic properties deviate from those of bulk material and become size dependent. This phenomenon is refered to as the quantum size effect.

One of the frequently used probes for studying the electronic states of small particles is the surface plasmon (SP) excitation. Genzel et al. studied the optical absorption peaks from silver particles in glass. They found a blue shift of the SP peak when the particle size becomes smaller (see Fig 2). Electron energy loss spectroscopy (EELS) studies have also been performed. Recently vom Felde et al. reported broad beam EELS with large momentum transfer from potassium particles embedded in a MgO matrix. They observed that the surface plasmon energy increases when particle size becomes smaller, and there is a positive dispersion for particles of size 40 Å.
High spatial resolution microanalysis on the (200) nanodiffraction intensity to determine the Al concentration of AlGaAs-GaAs MQWS
Authors: Ou H.-J. , Higgs A. A. , Perkes P. R. , Cowley J. M.
Published: June 2020

When a nano probe electron beam of 4Å in diameter is scanned from a GaAs layer to a AlGaAs layer on a cleaved AlGaAs-GaAs MQWS sample (with X = 0.75 of Al concentration for AlGaAs, as grown by MBE), a significant increase of the (200) nanodiffraction intensity can be observed in the [001] nanodiffraction patterns of AlGaAs, which indicates that the (200) intensity is sensitive to the Al content of AlGaAs. The appearance of the {200} nanodiffraction disc patterns of AlGaAs is best recognized with the four-way split (000) disc, as shown in Fig. 1(e), because the (000) disc overlaps with the four nearest {200} discs. This is expected in the simulated AlGaAs (X = 0.75) nanodiffraction pattern of Fig. 1(g). While both the experimental and simulated patterns of GaAs, as illustrated in Fig. 1(d) and (f), show almost no intensity of the {200} nanodiffraction patterns. From the previous studies, two conclusions are: (1) measurement of the (200) thickness contour position in AlGaAs layer can reflect the content of the absolute Al concentration for each AlGaAs layer and (2) for a uniform region of thickness less than 200Å, the local Al concentration. Al%j. of a small region within a AlGaAs layer can be determined by the formula Al%j = [l - ΔI200/I200)]· Al%, if the absolute Al concentration. Al%. and the ratio of the change of the (200) intensity, (ΔI200/I200), are known.
Quantitative elemental x-ray imaging of timed calcium displacement from stores (JSR) in isolated single frog skeletal muscle fibers: Its efficacy in quantitation
Authors: Nassar R. , Ingram P. , High T. , Sommer J.R.
Published: June 2020

We are performing a continuing series of experiments to describe the time course of fast physiological events in terms of morphology and microtopochemistry, using electron probe x-ray microanalysis in both the static probe (STP) and quantitative digital imaging (QDI) modes. As a model, we are using timed spatial displacements of elements (e.g. the release of calcium from JSR) during the process of excitation-contraction coupling in single, intact skeletal muscle fibers quick-frozen at known time intervals following electrical stimulation. There is considerable variance in the total calcium concentration ([Ca]t) among JSRs, which increases the requirement for widespread sampling to increase statistical confidence. Even at a low number of pixels/raster chosen for time economy, QDI seems well suited to deal with this variance because it covers a large number of JSRs in a reasonably short scanning time (64x64 pixels: ∽3 h; 128×128 pixels: ∽9 h). Here, we report on the efficacy of QDI in our experiments and compare the results with those obtained from STP.