bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Thermal Vibration Phase Correlation in Electron Diffraction and Imaging
Authors: Wang Z. L. , Bentley J.
Published: June 2020

Consideration of phase correlation between localized inelastic events occurring at different atomic sites remains one of the major obstacles in the dynamic calculations of either the Bloch wave theory or the generalized multislice theory. The former is restricted by the 3-D periodic assumption of the transition matrix and the latter is limited by the coherent treatment of the inelastic excitation within the same slice. To approach this problem properly, one starts from the coupled Schrodinger equations,

Ψ0 is the elastically scattered wave of energy E0, Ψn describes the inelastically scattered wave of the nth excited state of energy En = E0 - εn, and H'nm are the transition matrix elements. Taking Ψn = ϕn(z)Ψn0(r), where Ψn0(r) satisfies the elastic scattering Schrodinger equation of different wave vectors,

and under the small angle approximation, Eq. (1) becomes

Equation (2) can be solved with established elastic scattering theory, such as the multislice method.
Development of the 25 micron pixel imaging plate system for TEM
Authors: Ogura N. , Yamada T.
Published: June 2020

In 1986, we reported that the Imaging Plate (IP) could be applied to the recording material for TEM. In 1990, we reported the first commercial IP system for TEM, which was co-developed with JEOL Ltd. This time, we developed a new IP system that has the following remarkable concepts.

1. Enormous amount of information and high image quality The IP is read by the IP Reader at a pixel size of 25 microns and at a gray level of 16384 (14 bit). One image consists of 3760 × 3000 pixels. This means the image satisfies two essential requirements, i.e., high resolution and large area, at the same time. As the new sophisticated scanning system and the 400 dpi high-quality color printer (Fujix Pictrography 3000) have been combined, the final hard copies are almost identical to photographic films.

2. Applicable to most TEMs The size of the IP is 99.6 × 80.9 mm, which is the same as that of photographic films mainly used in the USA, so the IP can be applied to most TEMs of any manufacturer in the world.
Advanced computing for ultra-high-resolution in TEM
Authors: Thust A. , Coene W. M. J.
Published: June 2020

1. Introduction
Attempts to push the resolution of electron microscopes towards 1 Å follow presently two different strategies. One approach takes advantage of the short electron wavelength provided by high-voltage instruments (E > 1 MeV) resulting in an "interpretable" point resolution close to the information limit. An alternative strategy is based on the idea to extend the information limit of conventional medium-voltage instruments (E ≈ 200 - 300 keV) by taking advantage of the excellent coherence properties of field-emission guns (FEG). In the latter approach, however, the gain of extra information beyond the "interpretable" point resolution is of no direct use for structure interpretation. Generally, the interpretability of single highresolution images suffers from a loss of phase information and from contrast-delocalization effects, the latter being caused by the spherical aberration and the defocussing of the objective lens. These derealization effects become drastically apparent when aiming at the ultra-high resolution regime (d < 1.5 Å) which is routinely accessible with medium-voltage FEG-TEMs.
Simulation of high-resolution annular dark field STEM images
Authors: Kirkland E. J.
Published: June 2020

In a STEM an electron beam is focused into a small probe on the specimen. This probe is raster scanned across the specimen to form an image from the electrons transmitted through the specimen. The objective lens is positioned before the specimen instead of after the specimen as in a CTEM. Because the probe is focused and scanned before the specimen, accurate annular dark field (ADF) STEM image simulation is more difficult than CTEM simulation. Instead of an incident uniform plane wave, ADF-STEM simulation starts with a probe wavefunction focused at a specified position on the specimen. The wavefunction is then propagated through the specimen one atomic layer (or slice) at a time with Fresnel diffraction between slices using the multislice method. After passing through the specimen the wavefunction is diffracted onto the detector. The ADF signal for one position of the probe is formed by integrating all electrons scattered outside of an inner angle large compared with the objective aperture.
Near-field plasmon-resonance scanning microscopy
Authors: Schultz Sheldon
Published: June 2020

In the past few years the field of near-field scanning optical microscopy (NSOM) has developed rapidly with applications spanning all the physical sciences. A key goal of this form of microscopy is to obtain resolution at levels well beyond those possible with the usual far-field optics. In contrast to far-field optics, which is bounded by the well known limits imposed by diffraction, near-field optics has no "in principle" fundamental lower limit in lateral size, at least down to atomic dimensions, although in practice, signal-to-noise considerations may restrict the application of NSOM to a few nanometers.

The simplest form of NSOM to visualize is based on the principle of a sub-wavelength aperture (with D/λ < < 1) in an opaque plane. Light impinging on this aperture may only be transmitted through the diameter D, and, indeed, were it observed in the far-field, would be spread out over the entire half space due to diffraction. However, if the sample to be studied is placed in the near-field of the aperture, say within a distance D away, the region illuminated will also be restricted to a lateral dimension very close to D.
Resolution beyond the diffraction limit: 4PI-confocal-, STED-, and GSD- fluorescence microscopy
Authors: Hell Stefan W. , Hanninen Pekka E. , Schrader Martin , Wilson Tony , Soini Erkki
Published: June 2020

In far-field light microscopy resolution is determined by diffraction. In a far-field light microscope such as the confocal scanning light microscope, the resolution is governed by the extent of the squared intensity distribution in the focal region. Precise measurements of the confocal PSF have shown that the axial and lateral resolution of a confocal microscope (NA=1.4 oil, 1= 633 nm) is 520nm and 200nm (FWHM), respectively. At a wavelength of 375nm, this amounts to a resolution of 300 nm (axial) and 120 nm (lateral), obtainable with a standard confocal microscope of high aperture.

A 3-7 fold increase in axial resolution is achieved with a 4Pi-confocal microscope. The 4Piconfocal microscope uses two high numerical aperture objective lenses that are used coherently for illuminating or detecting the same point in the object space. The present paper deals with the latest developments in the field of 4Pi-confocal microscopy. The Optical Transfer Functions (OTF) of 4Piconfocal microscopies with 4Pi-illumination (type A), 4Pi-detection (type B), and 4Pi illumination and detection (type C) are measured and compared with their standard confocal counterpart.
Design of an intermediate high voltage EM for 3-D studies of biological material and its integration with a system for remote access
Authors: Ellisman Mark H.
Published: June 2020

The increased availability of High Performance Computing and Communications (HPCC) offers scientists and students the potential for effective remote interactive use of centralized, specialized, and expensive instrumentation and computers. Examples of instruments capable of remote operation that may be usefully controlled from a distance are increasing. Some in current use include telescopes, networks of remote geophysical sensing devices and more recently, the intermediate high voltage electron microscope developed at the San Diego Microscopy and Imaging Resource (SDMIR) in La Jolla. In this presentation the imaging capabilities of a specially designed JEOL 4000EX IVEM will be described. This instrument was developed mainly to facilitate the extraction of 3-dimensional information from thick sections. In addition, progress will be described on a project now underway to develop a more advanced version of the Telemicroscopy software we previously demonstrated as a tool to for providing remote access to this IVEM (Mercurio et al., 1992; Fan et al., 1992).
A microscopic system for high-resolution electron crystallography
Authors: Fujiyoshi Y. , Murata K. , Mitsuoka K. , Hirai T. , Miyazawa A. , Kimura Y.
Published: June 2020

High-resolution electron cryo-microscopy is one of good candidate for structure analysis of membrane-protein, and also actually analyzed the structure of membrane-proteins such as bacteriorhodopsin (bR) and plant light-harvesting complex (LHC). By developing an expeditious method for structure analysis up to atomic or near atomic resolution, we would like to interpret a function of protein from the structural point of view. However, there are some difficulties in electron microscopy for structure analysis of protein. Especially, the most serious problems are the specimen damage caused by electron irradiation, the denaturation of biomolecules caused by dehydration and missing high-resolution data on electron micrographs at high-tilted angle.

The irradiation damage at 8K has been found to be reduced to 1/20 compared with that at room temperature. We have, therefore, developed a high-resolution electron cryo-microscope and improved it by which images can be recorded with higher resolution than 3 Å at a specimen-stage temperature of 4.2 K, even when the specimen is highly tilted. The highly tilted data are essential for reduction of the missing corn effect.
X-ray standing wave measurements of adsorbates on metal surfaces
Authors: Heskett D. , Shi X. , Su C. , Xu P. , Corridon D. , Berman L E. , Kao C.-C. , Bedzyk M.J.
Published: June 2020

One of the main goals in surface science is the determination of the geometric structure of the surface, including the local registry of adsorbed atoms and molecules on surfaces. The X-ray Standing Wave (XSW) technique offers a powerful method of locating the positions of atoms and molecules in and on single crystals1. This technique is now being employed with increasing frequency with the availability of x-ray radiation synchrotron sources, but is still underutilized with regards to structural determinations of adsorbates on metal surfaces.

When x rays are Bragg-reflected from a crystal, the incident and diffracted waves interfere to set up a standing wave field parallel to and having the same spatial periodicity as the reflecting planes. The exact location of the peaks of this standing wave field shift relative to the atomic scattering planes as one scans through the region of total reflectivity associated with the Bragg condition. By measuring a yield characteristic of a bulk atom or an adsorbate excited by the standing wave field, such as Auger electron emission, core level photoemission, or x-ray fluorescence, the atom's position relative to the diffraction planes can be determined.
Dynamical Lorentz TEM observation of exchange coupling in MR Ni0.80Fe0.20/NiO films
Authors: Cao Wei
Published: June 2020

In our research program involved with materials showing magnetoresistive (MR) phenomena, attention has been given to detailed microstructural analyses in order to understand physical properties and other characteristics. One of the biggest problems in the MR sensor application is the noise associated with Barkhausen jumps due to magnetic domain wall motion in the MR sensor, usually permalloy films (Ni0.80.Fe0.20) It has neen found that when a permalloy film was deposited together with an antiferromagnetic film such as FeMn, the noise could be suppressed. It is known that there is an exchange coupling field ( He) in the Ni0.80.Fe0.20/FeMn bilayers through the interface, and it is this exchange coupling field that makes the MR sensor a single domain which suppresses the noise. However, FeMn antiferromagnetic films have poor corrosion resistance, and this provides a motivation to find a substitute material for FeMn.

Antiferromagnetic NiO and CoO have received some attention as alternative materials because of their corrosion resistance.
Image processing of conventional TEM images: a catalyst case study
Authors: Briceño-Valero J. M. , Martinez L. , Moore K. , Grassian V.
Published: June 2020

Particle characterization with the Transmission Electron Microscope (TEM) has the inherent problem of interpreting three dimensional objects from two-dimensional projections. Relevant questions when measuring small particles include how projection of the image will distort measurement of crystallite size, and how will the image distort the morphology of the particle Another difficulty is the effect of overlapping images from two or more particles. In the case of supported catalysts, an additional problem may be termed "differential contrast" which interferes with distinguishing between the supported metal crystallites and the support itself. While these situations may appear to be quite different, the is a shared concern of how the general appearance of the particle image related to its real shape. Image processing technology can be used to extract and display hidden information from conventional TEM micrographs. In this study, platinum particles supported on silica were examines.

TEM images were taken at 80,000X magnification with a Hitachi H-600 at 100 kV, digitally acquired using an Imapro QCS 3200 flatbed scanner at 3200 dots per inch.
Electron diffraction of copper perfluorophthalocyanine on the HVEM
Authors: Tivol W. F. , Fryer J. R.
Published: June 2020

The use of high-energy (1200 kV) electrons has been shown to be advantageous in the ab initio structure analysis from electron diffraction of organic compounds. Previous studies showed that ab initio analysis of copper perchlorophthalocyanine could be accomplished at accelerating voltages at or above 1000 kV, but not at 400 kV for crystals which are about 10 nm thick. Copper perbromophthalocyanine could also be analyzed ab initio at 1200 kV, but the presence of severe dynamical scattering precluded such analysis at lower voltages.

Copper perfluorophthalocyanine (Cu FPC) was grown epitaxially from the vapor phase onto a clean KC1 crystal face. Electron diffraction patterns were obtained from crystals tilted at 20° and oriented so that the electron beam was parallel to the c-axis.

Electron doses were kept to a minimum by the use of a 100 μm condenser aperture and a highly excited first condenser lens. A video system allows scanning the specimen to find a crystal suitable for the correct orientation of the grid by rotating it within its own plane and focusing the objective lens, all at an illumination level below that necessary to distinguish anything by eye on the HVEM's phosphor screen.
AEM characterization of magnetic nanoparticles encased in graphite shells
Authors: Host J. J. , Teng M. H. , Hwang J. H. , Elliott B. R. , Weertman J. R. , Mason T. O. , Johnson D. L. , Dravid V. P.
Published: June 2020

Since it was discovered that crystalline materials could be encased in graphite shells, protection in this manner has been the focus of significant research. Previously, production of graphite encapsulated crystalline nanoparticles has been reported using an arc discharge between an anode stuffed with a metal oxide and a graphite cathode, resulting in a mixture of carbides, encapsulated carbides and carbonaceous debris. More recently, an arc discharge between metal electrodes has been used to produce large quantities of pure metal nanoparticles, with the addition of graphite to the anode resulting in the large scale production of graphite encapsulated metal nanoparticles (GEMN). In earlier studies, these materials were separated from the other products of the arc discharge only by a magnetic gradient, which does not remove the non-encapsulated crystalline particles. Therefore, the immersion of the product mixture in an acid bath was added as a subsequent processing step. The combined arc discharge/acid bath technique reduces both production and separation problems, producing a large quantity of Fe, Co, and Ni GEMN free from any non-encapsulated metal particles. Subsequent characterization of the resulting material has led to a better understanding of the GEMN produced.
In situ REM study of indium particle evolution on InP(110) surfaces
Authors: Gajdardziska-Josifovska M. , Malay M. H. , Smith David J.
Published: June 2020

Reflection electron microscopy (REM) has been used by several groups for in situ studies of terrace and step dynamics induced by phase transformations, film growth, and surface electromigration. Real-time viewing and video-recording of these phenomena has become possible with the use of intensified TV cameras under surface resonance diffracting conditions. Recently we captured the dynamics of nucleation and growth of In particles on InP(l10) surfaces induced by thermal annealing in an ultrahigh-vacuum transmission electron microscope. In addition to the projection problem, also encountered in TEM, the REM image interpretation is further complicated by foreshortening effects. At present, there are no developed methods for measurement of particle sizes from REM images. This work quantifies the In particle shape and size evolution from in-situ REM experiments.

Samples were prepared by cleavage of an undoped (001) InP wafer along the (110) crystallographic plane. The cleavage was performed in air, immediately before loading into a Philips 430ST HREM, modified for UHV operation and equipped with a single-tilt specimen heating holder.
In situ study of tetragonal-orthorhombic structural transformation in La2-xBaxCuO4
Authors: Zhu Yimei , Tafto J.
Published: June 2020

In the concentration range of the local Tc minimum in La2-xBaxCuO4 (0.10≤×≤0.15), below 60K, there is a low temperature tetragonal (LTT) structure (space group P42/ncm). With an increase in temperature, the structure becomes orthorhombic (LTO, space group Bmab), then above 140K becomes tetragonal (HTT) with the space group I4/mmm.

The transition from HTT to LTO during cooling generates twins, and the twin morphology persists even below 60K. This is inconsistent with a pure LTT phase, since twinning is associated with an orthorhombic symmetry. To address the issue of the LTO/LTT phase transition, we performed in-situ experiments with a 200 keV TEM equipped with a liquid H2 specimen holder.

Fig.1(a) and (b) show selected area diffraction patterns taken at 15K in the (001)* and (101)* zone, respectively. During in- situ cooling and the LTO/LTT transition, the (101)* diffraction pattern remains the same because h+l=2n reflections are allowed in both LTO and LTT.
Techniques for in situ HVEM mechanical deformation of nanostructured materials
Authors: Wall M.A. , Barbee T.W. , Dahmen U.
Published: June 2020

We have developed two in situ HVEM experimental techniques which allow us to begin fundamental investigations into the mechanisms of deformation and fracture in nanostructured materials. First, a procedure for the observation of tensile deformation and failure of multilayer (ML) materials in cross-section is detailed. Second, the development of an in situ HVEM nanoindentor of surfaces and films on surfaces in cross-section is presented.

Nanostructred ML materials often exhibit enhanced physical properties such as increased hardness and strength. There have been few (if any) direct observations of the mechanisms by which nano-scale structures affect deformation thereby enhancing mechanical performance. Nanoindenting has become a primary technique for measuring the mechanical properties of small volume materials. The mechanical properties of small volumes can vary greatly from bulk values. The elastic and plastic response and microstructure evolution in these small volumes under the indentor tip has never been dynamically observed before. Observation of the behavior of material under these conditions would no doubt further our understanding of the mechanical behavior of nanostructured materials.
In situ observations of electromigration induced void behavior
Authors: Marieb T. , Bravman J. C. , Flinn P. , Gardner D. , Madden M.
Published: June 2020

Electromigration and stress voiding have been active areas of research in the microelectronics industry for many years. While accelerated testing of these phenomena has been performed for the last 25 years[1-2], only recently has the introduction of high voltage scanning electron microscopy (HVSEM) made possible in situ testing of realistic, passivated, full thickness samples at high resolution.

With a combination of in situ HVSEM and post-testing transmission electron microscopy (TEM) , electromigration void nucleation sites in both normal polycrystalline and near-bamboo pure Al were investigated. The effect of the microstructure of the lines on the void motion was also studied.

The HVSEM used was a slightly modified JEOL 1200 EX II scanning TEM with a backscatter electron detector placed above the sample[3]. To observe electromigration in situ the sample was heated and the line had current supplied to it to accelerate the voiding process. After testing lines were prepared for TEM by employing the plan-view wedge technique [6].
High-resolution TEM and energy filtering TEM study of interfacial structure and reaction of diamond/Si in chemical vapor deposition
Authors: Chen Fu-Rong , Chang L. , Chen C. J. , Lin T. S.
Published: June 2020

Diamond film was grown using microwave plasma CVD technique which consists of three steps: carburization, bias and growth . The high resolution TEM (HRTEM) in cross-sectional view has been used to observe the evolution of interfacial structure in each processing step [1]. The chemistry near the interface was characterized with elemental mapping using energy-filtered imaging technique with Gatan imaging Filter (GIF) [2]. At the carburization stage, β-SiC, diamond particles and graphite plates have been observed in an amorphous layer. This amorphous layer was analysized to be carbon by energy filtering technique.

As shown in the Fig. 1, β-SiC can form in epitaxial orientation with Si in the following stage of biasing. Graphite was not observed after the bias was applied. At the bias stage there is an interlayer of 6 nm thick between diamond and silicon substrate . From the high resoultion image in Fig. 2 (a), most of the regions of the interlayer are of amorphous characteristics which presents a barrier to identify the elemental compositions.
Interface analysis in the VG microscopes’ HB603 300 keV STEM
Authors: Bruley John , Ackland David W. , Fang Jianxin , Williams David B.
Published: June 2020

The optimum operating conditions for microanalysis (either EDX or EELS) would be those which maximize the signal-to-noise ratio, SNR, and signal-to-background ratio, SBR, and at the same time minimize the probe size so as to locate the signal to as small a volume as possible. In practice however these three quantities can not be optimized simultaneously. For many materials problems, the analyst seeks first to determine if a solute has segregated to an interface. We therefore consider the conditions required to operate the analytical microscope to maximize the detection sensitivity of interfacial segregants.

The choice of lens operating conditions for carrying out interface analysis on a STEM is not necessarily intuitive. Apart from the geometrical optics, instrumental artifacts may adversely influence the observed SNR and SBR. We have carried out a series of EDX experiments to compare the working performance of interface analysis with that expected using a simple planar interface segregation model and geometrical optics.
Direct imaging of spatially varying potential and charge across internal interfaces in solids
Authors: Ravikumar V. , Rodrigues R. P. , Dravid V. P.
Published: June 2020

The importance of spatially varying potential (and thus charge) across lattice discontinuities in solids has been recognized in many technologically important systems, especially those containing electrically active interfaces, e.g. electroceramics. The presence of spatially varying potential across electroceramic interfaces has been indirectly deduced and analyzed using predominantly bulk measurement techniques like I-V, C-V curves and impedance spectroscopy. Direct imaging of spatially varying electrostatic potential profile and determination of the sign, magnitude and spatial distribution of the associated interface- and space- charge (and therefore defect density) in electroceramics have remained elusive.

We have utilized the technique of transmission high energy electron holography to directly image and quantify the electrostatic potential across grain boundaries (GBs) in SrTiO3, a functional electroceramic. The phase of the exit wave function at the GB region can be altered by : (i) variation in local mean inner potential (related to the change in density of atoms at the GB), (ii) differential diffraction conditions across the interface, (iii) change in the local specimen thickness and, (iv) presence of local electrostatic (electrical charge) and magnetic potential.
AFM studies of annealed single-crystal α-alumina surfaces
Authors: Heffelfinger Jason R. , Bench Michael W. , Barry Carter C.
Published: June 2020

Since the invention of atomic-force microscopy (AFM) in 1986, the technique has found an invaluable niche in the imaging of insulating surfaces. AFM allows for analysis of topographical details at the atomic level with minimum sample preparation, but the technique is subject to artifacts such as broadening of surface structures and ghost images of the tip due to the finite size and shape of the contacting probe. In the present investigation, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used as supporting techniques to AFM in the study of annealed single-crystal α-alumina surfaces. Although discrepancies were found between the EM data and the AFM images which point to artifacts inherent to the AFM, useful information on surface step heights and roughness of terraces was gained using AFM.

AFM studies were performed on a Nanoscope III (Digital Instruments, Santa Barbara, CA) using microfabricated Si3N4 cantilevers (Ultralevers, Park Inst., Sunnyvale, CA).
Structural analysis of Tl/Hg-based superconductor with nominal composition Tl2Hg1 Ba4Ca4Cu6Ox having Tc=120K
Authors: Feng Y. , Larbalestier D.C. , Lechter W.L. , Osofsky M.S. , Skelton E.F. , Qadri S.B. , Toth L.E.
Published: June 2020

Recently, Hg-based superconductors HgBa2Can−1CunO2n+2+x (n=l,2,3) were demonstrated to have remarkably high transition temperatures (Tc). The Hg-compounds are structurally analogous to the previously discovered Tlbased compounds TlBa2Can−1CunO2n+2+x. Oxygen site occupation in the rock-salt Hg-O layers and Tl-O layers differ, due to the difference in the valence states of Tl (III) and Hg (II). In the Hg-compounds the Hg-O layer is always single while in the Tl-compounds both single or double Tl-O layers are possible. Up to 4 Cu-O2 layers may be found in both families. Martin et al. investigated the mixed Hg-Tl system and reported a new structure akin to a single cell Hg-1201/Tl-2201 intergrowth, having a Tc about half that of either individual compound. We synthesized mixed Hg-Tl compounds corresponding to the higher order intergrowth formula Tl2Hg1 Ba4Ca4Cu6Ox (Hg-1223/Tl-2223) with the hope of producing new intergrowth structures with higher Tc. In this report, we only describe our structural characterization on one of the Tl-Hg compounds with nominal composition Tl2Hg1 Ba4Ca4Cu6Ox. A complete report on the synthesis and properties of these compounds will be published elsewhere.
A correlation of CL emissions from Penrith sandstone with elemental distributions obtained by simultaneous SEM-CL and EDS analysis
Authors: Wright Paul J.
Published: June 2020

Most industrial and academic geologists are familiar with the beautiful red and orange cathodoluminescence colours produced by carbonate minerals in an optical microscope with a cold cathode electron gun attached. The cement stratigraphies interpreted from colour photographs have been widely used to determine the post depositional processes which have modified sedimentary rock textures.

However to study quartzose materials high electron densities and kV's are necessary to stimulate sufficient emission. A scanning electron microscope with an optical collection system and monochromator provides an adequate tool and gives the advantage of providing secondary and backscattered electron imaging as well as elemental analysis and distribution mapping via standard EDS/WDS facilities.

It has been known that the incorporation of many elements modify the characteristics of the CL emissions from geological materials. They do this by taking up positions between the valence and conduction band thus providing sites to assist in the recombination of electron hole pairs.
Quantitative nano-characterization of heterogeneous catalysts
Authors: Crozier P.A. , Pan M.
Published: June 2020

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.

HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.
EM of diamond-coated molybdenum field emission cathodes
Authors: Myers A. F. , Choi W. B. , McClure M. T. , Hren J. J. , Voelkl E. , Frost B. , Allard L. F.
Published: June 2020

Molybdenum is a common metal used to fabricate field emission devices.1-2 However, during extended operation, Mo cathodes exhibit current instabilities, which are thought to arise from adsorption of contaminants on the emitter surface. Coating Mo field emitters with diamond may enhance the current stability, as well as the total emission current. An understanding of the diamond nucleation mechanism is crucial for depositing consistent, uniform coatings on the emitters, and therefore producing reliable devices. To the author's knowledge, little information exists about the mechanism of diamond nucleation on these highly curved Mo surfaces.

In order to study the diamond nucleation mechanism, the morphology of the diamond coating and the structure of the diamond/Mo interface were analyzed by high resolution TEM. Emitters make excellent TEM specimens, since no further sample preparation is required after the diamond deposition; artifacts thus do not become an issue in interpreting the TEM results. Figure 1 shows that the films have a general morphology of clustered nanocrystalline particles.
Correlation of defect densities in semiconductors measured by TEM and optical profiling instruments
Authors: Mulestagno L. , Holzer J.C. , Hill D.E. , Fraundorf P.
Published: June 2020

The measurement of oxygen precipitate defect densities in Czochralski (CZ) Silicon wafers after standard heat cycles, or at strategic points in the device manufacturing process is often used as a tool to understand the oxygen precipitation behavior of the wafers on which electronic devices will be manufactured and to measure variability in the precipitation . The relevance of these measurements arises from the fact that controlled oxygen precipitation in the bulk of the wafer is used as a means to ‘getter’ unwanted impurities from the device layer of the wafer, and control of oxygen precipitation can be an important factor in device yields.

Typically the density of oxygen precipitate in a given wafer and the depth profile is determined by physically counting defects on cleaved slices after preferential etch to reveal the defects . This is a fairly time-consuming and a destructive test. However in the last few years a number of companies have developed computerized, non-destructive IR laser scattering instruments which rely on the fact that silicon is transparent to IR., and a precipitate (having a different refractive index from silicon ), will scatter some of the laser beam which can be detected.
Microstructural investigation of surface roughness in MBE-grown AlAs
Authors: Rajesh R. , Droopad R. , Kuo C. H. , Carpenter R. W. , Maracas G. N.
Published: June 2020

Knowledge of material pseudodielectric functions at MBE growth temperatures is essential for achieving in-situ, real time growth control. This allows us to accurately monitor and control thicknesses of the layers during growth. Undesired effusion cell temperature fluctuations during growth can thus be compensated for in real-time by spectroscopic ellipsometry. The accuracy in determining pseudodielectric functions is increased if one does not require applying a structure model to correct for the presence of an unknown surface layer such as a native oxide. Performing these measurements in an MBE reactor on as-grown material gives us this advantage. Thus, a simple three phase model (vacuum/thin film/substrate) can be used to obtain thin film data without uncertainties arising from a surface oxide layer of unknown composition and temperature dependence.

In this study, we obtain the pseudodielectric functions of MBE-grown AlAs from growth temperature (650°C) to room temperature (30°C). The profile of the wavelength-dependent function from the ellipsometry data indicated a rough surface after growth of 0.5 μm of AlAs at a substrate temperature of 600°C, which is typical for MBE-growth of GaAs.
Microstructures of ultra high molecular weight polyethylene by SEM
Authors: Wang H. C. , Sung C. , Hamilton J.
Published: June 2020

Ultra high molecular weight polyethylene (UHMWPE) is widely used in many orthopedic applications because of its good mechanical properties and excellent biocompatability. Mechanical properties are related to its ultra-high molecular weight, but the presence of defects in morphology will cause a decrease in these properties. The aim of this study was to characterize the microstructure and microchemistry of so-called “fusion defects”, observed by optical transmission microscopy, using SEM along with EDXS analysis. The fractured surface of UHMWPE was also studied.

Defects similar to those found in commercially prepared UHMWPE were detected in the hot-pressed and extruded samples prepared at U-Mass Lowell using GUR 412. They consist of holes or cavities and sometimes appear to be circular in shape and are composed of variously sized small holes. The size of the defects is around 100 μm in diameter which is similar to the particle size of the raw powders.
Characterization of corrosion scales in water distribution pipes using SEM and energy dispersive X-ray spectroscopy (EDS)
Authors: Shull J. L. , Kriven W. M. , McAnally A. S.
Published: June 2020

A series of water treatment programs involving different combinations of chemical additives was evaluated with the aim of reducing the levels of lead and copper in the drinking water of several communities in South Carolina. Test coupons from 7 pilot systems and 3 municipal distribution systems involved in the study were analyzed using SEM and EDS in order to determine the structure and composition of the corrosion scales and other deposits which formed on the interior pipe surfaces.

Sample coupons consisted of short segments of copper pipe, each of which was coated on one end with 50-50 wt.% lead-tin solder. Small (3 mm × 6 mm) pieces cut from both the soldered and unsoldered ends of the coupons were used as specimens for SEM surface analysis. Cross-sectional specimens were prepared by embedding small pieces in an acrylic resin and using an ultramicrotome to obtain high quality surfaces.

Analysis of the coupon surfaces produced results that were consistent with the corresponding water quality analyses.
HREM structure analysis of Σ13 symmetrical boundaries in strontium titanate bicrystals
Authors: Bonevich J.E. , Xiao S.Q. , Dahmen U.
Published: June 2020

Strontium titanate (STO) has found a myriad of technological applications, most notably as a substrate material for superconductors such as YBa2Cu3O7-δ (YBCO). One example is the growth of thin film YBCO devices whereby grain boundaries introduced in the films are used to create SQUID devices. The nature of the interfacial structure plays an important role in determining the behavior of these materials, e.g., their electrical properties. We have thus endeavored to investigate the atomic structure of grain boundaries in STO and to explore the structure implications on the properties of YBCO films.

The Σ13 STO bicrystals with two symmetrically inclined boundary planes of (510) and (320) were produced by Shinkosha Ltd.(Japan); the bicrystals were rotated by 22.6°±0.5° about the common [001] zone axis. Cross-sectional TEM specimens were prepared in the usual manner and examined in the NCEM's Atomic Resolution Microscope operating at 800 kV. The HREM images were subsequently digitized for template matching (cross-correlation) analysis.
Trial production of γ-type energy filtering TEM
Authors: Taniguchi Y. , Nakazawa E. , Taya S.
Published: June 2020

Imaging energy filters can add new information to electron microscopic images with respect to energy-axis, so-called electron spectroscopic imaging (ESI). Recently, many good results have been reported using this imaging technique. ESI also allows high-contrast observation of unstained biological samples, becoming a trend of the field of morphology. We manufactured a new type of energy filter as a trial production. This energy filter consists of two magnets, and we call γ-filter since the trajectory of electrons shows ‘γ’-shape inside the filter. We evaluated the new energyγ-filter TEM with the γ-filter.

Figure 1 shows schematic view of the electron optics of the γ-type energy filter. For the determination of the electron-optics of the γ-type energy filter, we used the TRIO (Third Order Ion Optics) program which has been developed for the design of high resolution mass spectrometers. The TRIO takes the extended fringing fields (EFF) into consideration. EFF makes it difficult to design magnetic energy filters with magnetic sector fields.
X-ray Gabor holography
Authors: Lindaas Steve , Jacobsen Chris , Kalinovsky Alex , Howells Malcolm
Published: June 2020

Soft x-ray microscopy offers an approach to transmission imaging of wet, micron-thick biological objects at a resolution superior to that of optical microscopes and with less specimen preparation/manipulation than electron microscopes. Gabor holography has unique characteristics which make it particularly well suited for certain investigations: it requires no prefocussing, it is compatible with flash x-ray sources, and it is able to use the whole footprint of multimode sources. Our method serves to refine this technique in anticipation of the development of suitable flash sources (such as x-ray lasers) and to develop cryo capabilities with which to reduce specimen damage. Our primary emphasis has been on biological imaging so we use x-rays in the water window (between the Oxygen-K and Carbon-K absorption edges) with which we record holograms in vacuum or in air.

The hologram is recorded on a high resolution recording medium; our work employs the photoresist poly(methylmethacrylate) (PMMA). Following resist “development” (solvent etching), a surface relief pattern is produced which an atomic force microscope is aptly suited to image.
The influence of the objective lens current in low magnification electron holography
Authors: Frost B.G. , Joy D.C. , Völkl E. , Allard L.F.
Published: June 2020

In order to align an electron microscope for low magnification holography we usually completely switch off the objective lens and image the sample by the first intermediate lens. In addition, to achieve a highly coherent electron beam we highly excite the condensor lens resulting in a divergent illumination of the sample and the intermediate lens. Now negatively biasing the fiber of a Möllenstedt type biprism placed between the first an second intermediate lenses of our Hitachi HF-2000 field emission electron microscope creates two virtual sources below the back focal plane of the first intermediate lens. These two sources are necessary to form off-axis holograms. Slightly exciting the objective lens and still imaging the sample by the first intermediate lens results in two major changes in our holograms.

First: Due to an electron beam less divergent or even convergent illuminating the first intermediate lens when exciting the objective lens (compare Fig. 1 to Fig.2) the angle β at which object wave and reference wave are superimposed decreases.
Quanitative aspects of electron diffraction using electron holography
Authors: Völkl E. , Allard L.F. , Frost B. , Nolan T.A.
Published: June 2020

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:

(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))

where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.
Studies of dental samples by the low-loss electron method in the field emission SEM
Authors: Wells Oliver C. , Rishton Stephen A. , Bromage Tim
Published: June 2020

A low-loss electron (LLE) detector has been installed with a redesigned specimen stage in a Hitachi S800 field-emission SEM (Fig. 1). This has been evaluated by comparing secondary electron (SE) and LLE images of abrasive striations known as “microwear” on an uncoated human incisor mounted at 45° to the beam (Fig. 2).

Microwear features typically appear as long linear scratches or discrete pits in the range 0.2 μm to 2.0 μm in width. These reflect both the specific contacts that one tooth makes against another when chewing (jaw movements and tooth wearing patterns) and the food eaten (seed, plant fiber, fruit, etc.). The density of scratches per unit area has been widely used as a measure of the dietary proclivities of an organism. Thus grazers have been distinguished from browsers on the basis of the greater density of scratches caused by opaline phytoliths in grasses that are harder than tooth enamel.
Improved 3-D reconstruction using stereo computer graphics and multiple tilt EM images
Authors: Peachey Lee D. , Fodor Lou , Haselgrove John C. , Dunn Stanley M. , Huang Junqing
Published: June 2020

Stereo pairs of electron microscope images provide valuable visual impressions of the three-dimensional nature of specimens, including biological objects. Beyond this one seeks quantitatively accurate models and measurements of the three dimensional positions and sizes of structures in the specimen. In our laboratory, we have sought to combine high resolution video cameras with high performance computer graphics systems to improve both the ease of building 3D reconstructions and the accuracy of 3D measurements, by using multiple tilt images of the same specimen tilted over a wider range of angles than can be viewed stereoscopically. Ultimately we also wish to automate the reconstruction and measurement process, and have initiated work in that direction.

Figure 1 is a stereo pair of 400 kV images from a 1 micrometer thick transverse section of frog skeletal muscle stained with the Golgi stain. This stain selectively increases the density of the transverse tubular network in these muscle cells, and it is this network that we reconstruct in this example.
The effect of temperature on high-resolution TEM image contrast
Authors: Geipel T. , Mader W. , Pirouz P.
Published: June 2020

Temperature affects both elastic and inelastic scattering of electrons in a crystal. The Debye-Waller factor, B, describes the influence of temperature on the elastic scattering of electrons, whereas the imaginary part of the (complex) atomic form factor, fc = fr + ifi, describes the influence of temperature on the inelastic scattering of electrons (i.e. absorption). In HRTEM simulations, two possible ways to include absorption are: (i) an approximate method in which absorption is described by a phenomenological constant, μ, i.e. fi; - μfr, with the real part of the atomic form factor, fr, obtained from Hartree-Fock calculations, (ii) a more accurate method in which the absorptive components, fi of the atomic form factor are explicitly calculated. In this contribution, the inclusion of both the Debye-Waller factor and absorption on HRTEM images of a (Oll)-oriented GaAs crystal are presented (using the EMS software.

Fig. 1 shows the the amplitudes and phases of the dominant 111 beams as a function of the specimen thickness, t, for the cases when μ = 0 (i.e. no absorption, solid line) and μ = 0.1 (with absorption, dashed line).
Histochemical methods for localizing and characterizing cell and tissue glycoconjugates
Authors: Schulte B.A.
Published: June 2020

Glycoproteins, glycolipids and proteoglycans, collectively termed glycoconjugates, account for a large percentage of all tissue constituents. The carbohydrate moieties associated with these macromolecules have long been known or suspected to play specific biologic roles such as protection of the peptide backbone from recognition by antibodies and proteases, regulation of proper folding, assembly and exocytosis of secretory glycoproteins and lubrication of mucosal surfaces. Structural studies of complex carbohydrates have gained momentum over the past two decades with the realization that they participate in a much wider range of dynamic biological processes than was previously envisioned. Expressed predominantly at the external surface of plasma membranes and in the extracellular matrix glycoconjugates possessing unique saccharide sequences serve as recognition sites (ligands) for endogeneous or exogeneous carbohydrate binding proteins (lectins). Lectin-ligand interactions are involved in cell-cell and cell-substrate recognition events which occur for instance, during development and morphogenesis, wound healing and activation of immune responses.
Observations of unusual stacking fault configurations using complimentary strong and weak beam images
Authors: Kim H. S. , Sheinin S. S.
Published: June 2020

In this paper, the authors present both strong and weak beam images of stacking faults in FCC cobalt which indicate the presence of an unusual stacking fault configuration. Experimental images have been obtained at 100 kV from a specimen in a orientation with (1-1-1) stacking fault planes. Fig. 1 shows the (-1-11) strong beam dark field image. It can be seen that the contrast in faults A, B and D are very similar, while the fault at C is different. Using conventional techniques for identifying the nature of stacking faults in FCC materials A, B and D have been identified as single or intrinsic faults with a displacement vector R=l/3[-111]. On the other hand, the fault at C can be identified as a double or extrinsic fault. At this point, the interpretation of the faults in the image in Fig. 1 appears to be completely straightforward and in keeping with results obtained from a conventional analysis. The next image of interest is shown in Fig. 2 which shows the same four faults as in Fig. 1 obtained under weak beam diffraction conditions.