bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Throughput, Large Area Silicon X-Ray Detectors for High-Resolution Spectroscopy Applications
Authors: Iwanczyk Jan S , Part Bradley E , Tull Carolyn R , Barkan Shaul
Published: July 2020

The concept utilized in charge coupled devices (CCD’s) for detection and imaging of light signals involving lateral movement of charges and extremely low capacitance of the detector and readout electronics has spawned a variety of new ideas in the design of nuclear detectors. Initially, silicon drift detectors (SDD’s) were developed for high energy physics applications. More recently, a vigorous effort to develop new structures for x-ray spectroscopy and light detection has started. Drift structures have been designed in a variety of topologies and materials (such as Si, CdZnTe, and HgI2) to satisfy the requirements of many different applications. The most interesting features that can be achieved with drift structures include: a) Large active area devices with low capacitance and low electronic noise, b) Very high signal throughput, c) Operation at or near room temperature, d) High sensitivity over the large entrance electrode to low energy xrays and short wavelength light, f) Single carrier charge collection allowing for elimination of hole contribution to the spectral broadening in compound semiconductor detectors such as HgI2, CdTe, and CdZnTe, f) 2D resolution of few tens of micrometer in both directions over few cm2 active areas, and g) Possibility of using more sophisticated schemes of charge collection by switching between integration and drift mode.
In Situ Nanoscale Studies of Liquid Polymerization Reactions in the Manufacture of Polyamides and.Combinatorial Catalysis
Authors: Gai Pratibha L , Kourtakis K , Ziemecki S
Published: July 2020

Low temperature heterogeneous catalytic routes for polymers are of considerable interest in the chemical sciences and technology because they are economical and environmentally beneficial. However such routes have been difficult because of an incomplete understanding of process control and low yields. Currently, hydrogenation of aliphatic dintriles in solvents is used in the chemical industry to manufacture the corresponding diamenes which are subsequently reacted with adipic acid solutions and polymerized to produce the polyamide, nylon (6,6).

Here we report an alternative, low temperature heterogeneous catalytic process for the polymerization reactions using novel environmental-HRTEM (EHREM) in liquid environments. EHREM under simulated reaction conditions provides direct, in situ real-time information on the dynamic structural and chemical changes and reaction modes of operation. We prepared high surface area heterogeneous catalysts including cobalt-ruthenium nanoclusters supported on rutile titania using a single step sol-gel technique, (shown in Fig. 1).
High-Resolution Backscattered Electron Microscopy: Determining the 3-D Distribution of Metallic Nanoparticles in Supported Catalysts
Authors: Liu Jingyue
Published: July 2020

Metallic nanoparticles play an important role in heterogeneous catalysis; these nanoparticles are usually finely dispersed onto high-surface-area supports and act as active centers during a catalytic reaction. The performance of a supported metal catalyst is often directly related to the size and spatial distribution of the nanoparticles. Traditionally, TEM/STEM techniques have to be used to visualize highly dispersed nanoparticles. A major limitation of TEM/STEM techniques is, however, the stringent requirements of samples that can be examined: Useful information can be extracted from only very thin areas of a sample. The preparation of samples suitable for TEM/STEM observation can also pose a challenging problem for examining certain types of catalyst samples such as catalyst beads, pellets, powders, cylinders, or other forms that are often used in industrial applications. These and other limitations preclude the application of TEM/STEM techniques to extracting useful information about the surface or subsurface properties of thick or bulk catalyst samples.
UHV ENFINA - A New High-Performance EELS Spectrometer for the VG STEM
Authors: Hunt John A , Dickerson Frank E , Abbott A , Szantai Gabriel , Mooney Paul E
Published: July 2020

The Gatan Enfina EELS spectrometer, featuring a new generation of detection system, was recently developed to upgrade or replace Gatan PEELS / DigiPEELS systems. Major advantages of the system include significant improvements to the detector point spread function, readout speed, sensitivity, readout noise, and increased number of detection channels. This design was until now not available for VG STEM systems because compatible detectors must not significantly degrade the UHV column vacuum and must survive column baking. in this abstract we report on a new detector system with comparable specifications to the standard Enfina system but designed for new or for upgrading existing Gatan UHV PEELS / DigiPEELS systems on the VG STEM.

The standard Enfina design has the scintillator, fibers, CCD, CCD socket board, flex-cables, thermo electric cooler and coupling grease in the shared vacuum of the EELS spectrometer and the electron microscope.
Charge - Ordered Manganeese Oxide Studied By Ω - Filter - Angular Resolved EELS
Authors: Murooka Y , Tanaka N , Hibino M , Tsuda K , Tanaka M
Published: July 2020

Despite of the intensive studies, Colossal Magnetoresistance (CMR) phenomena occurring in manganese oxides is still not fully understood. Theoretical studies based on an ordered crystal phase such as the charge-ordering (CO) phase have shown some successes in reproducing experimental evidences. Recently it was, however, shown that such a CO phase included giant clusters which were as large as 100 nm. This indicates the importance of the nanometer-scale information about the electronic structure to understand the CO. La0.5Sr1.5MnO4 is one of the oxides under intense investigations. in the CO phase, the eg valence electrons were found to be ordered at Mn sites. The optical responses of the CO clusters, however, has not been studied. in this study we have attempted to obtain such information from CO clusters in La0.5Sr1.5MnO4 by angular-resolved electron-energy-loss-spectroscopy (EELS) using an in-column type Ω-spectrometer.
Difference Spectrum Images: Numerical Filters Applied to EELS 3D Data Sets
Authors: Kothleitner G , Hofer F , Trevor C
Published: July 2020

Spectroscopy and imaging techniques based on electron energy-losses (EELS) in a TEM have proven to be important tools to characterize materials and life science samples. There are two techniques available to explore the energy-loss dimension. in the fixed-beam approach spectroscopic data are recorded via energy-filtered images taken by an energy-filtering transmission electron microscope (EFTEM). in the STEM approach a parallel-detection EELS spectrometer (PEELS) coupled with a small focused probe acquires large energy ranges of the energy-loss spectrum point-wise for a small area. Both techniques produce complete 3 dimensional data sets containing energy-loss information for all image pixels. This technique is called EFTEM or STEM spectrum imaging.

In the recorded SI data cube the x and y-axes correspond to spatial positions in the specimen as for any image. The third axis contains the energy-loss spectrum. in the scanning mode one records a complete spectrum for each pixel.
Electron Energy Loss Spectroscopy (EELS) At the Magic Angle
Authors: Brydson R , Daniels H , Brown A , Scott A , Nichells A , Rand B
Published: July 2020

Electron loss near edge structure (ELNES) reflects transitions of inner shell electrons to site- and symmetry-projected unoccupied electronic states, which in a solid lie above the Fermi level and may be calculated using advanced electronic structure calculations. The direction of momentum transfer, q, imparted during the inelastic scattering process is dependent on the angle over which the scattered electrons are collected. It is usual to resolve the momentum transfer, into components parallel and perpendicular to the incident beam direction (q∥and q⊥). in a specimen region which is crystallographically anisotropic, the exact direction of the momentum transfer and hence energy states available to the excited electron will depend on the specimen orientation with respect to the incident electron beam. Practically, this can present problems where quantitative comparisons and/or modelling of electronic structure between different specimen regions at different orientations, or within a polycrystalline material, or even between different samples are required.
Interpretation of Atomic Resolution Eels Signals at Interfaces
Authors: Möbus G , Nufer S
Published: July 2020

Introduction: Atomically resolved chemical analysis by means of electron energy (core-) loss spectroscopy has been postulated since the technical availability of highly focused sub-nm STEM beams. We study the feasibility of this approach, as compared to the alternative of spatial difference spectra, where interfacial resolution is achieved by subtracting boxes at and apart from the interface. A nanobeam EELS signal is generated by the dynamical propagation of a conical wave through the specimen. This wave acts as 3D-excitation envelope for inelastic scattering and is needed to link the ab-initio calculated atom- and angular-momentum-projected density-of-state (DOS) functions to measurable EELS signals.

Projected DOS: For the rhombohedral twin grain boundary in sapphire (FIG 1) as model system, DOS for p states in oxygen have been calculated 4 as described in, for the most stable twin structure obtained by ab-initio calculations.
Electronic structure analysis of LiCoO2 using Electron Energy Loss Spectroscopy (EELS)
Authors: Graetz J , Hightower A , Ahn CC , Rez P , Fultz B
Published: July 2020

LiCoO2 is currently the preferred cathode material in secondary Li-ion batteries. Stoichiometric LiCoO2 has rhombohedral symmetry and belongs to the R3m space group. This layered structure has Li and Co ions ordered along (111) planes to form alternating cation layers. The Co3+ ion, located in octahedral sites, forms a strong bond with neighboring oxygen atoms to produce O-Co-O sheets. Li layers are sandwiched between these sheets of CoO2.

It has traditionally been accepted that in lithium metal oxides (LiMO2) the valence of the transition metal compensates for the charge on the intercalated Li. The theoretical boundaries for Li concentration in an electrode of LixCoO2 are 0≤x≤l. Using a simple ionic charge transfer model, the fully-lithiated material has ions with charges of Li+, Co3+, and O2-. in the CoO2 end member the ions have charges of Co4+ and O2- This simple model incorrectly leads to the conclusion that the oxygen valence is virtually unaffected by Li intercation.
Advances in Microwave-Assisted Processing For Electron Microscopy
Authors: Giberson R T
Published: July 2020

The history of microwave-assisted processing has been dominated by the idea that microwave heating was an integral part of the equation. The separation of a microwave component from the heating effects of the radiation during sample processing has been experimentally difficult. Combined with this difficulty has been the closed cavity design of microwave ovens. This design is typical of laboratory and household ovens and results in the formation of “hot” and “cold” spots within the chamber. These spots produce regions in close proximity to each other which have widely varying heating effects on samples.

A second factor to consider with microwave heating is the effect wattage output has on rate and extent of microwave induced heating. Peak wattage outputs of all laboratory and most household microwave ovens are in excess of 650W. As a result the vast majority of all microwave-assisted protocols are based on heating parameters associated with high wattage processing.
Low Temperature Scanning Electron Microscopy of Soft Bodied Organisms
Authors: Erbe Eric F , Wergin William P , Ochoa Ronald , Dickens Joseph C , Moser William
Published: July 2020

Resolving the true fine structure and behavior of soft bodied organisms such as arthropod larvae, acari, nematodes, annelids and pupae by conventional scanning electron microscopy has been difficult. Classical preparation techniques, involving immersion fixation, dehydration and critical point drying, cause significant deleterious changes in specimen structure due to effects of surface tension, osmotic stress and mechanical damage. The intact exoskeleton, cuticle or other limiting membranes of these organisms, creates a formidable obstacle to the penetration of fixatives and solvents, which are only effective after a long period of time (hours). During this time, behavioral postures and much of the structural integrity are lost and most organisms detach from their hosts.

In previous studies, our laboratory utilized methods in low temperature freeze stabilization, to preserve and observe the undisturbed fine structure of biological samples. Plunge freezing, although more rapid, resulted in many parasitic organisms dislodging from hosts and being lost.
TEM Imaging of Amorphous Silicon Oxide - Silicon Nitride - Silicon Oxide Dielectric Films
Authors: Rabenberg Lew , Zhou J P , Ko Kil-Soo , Johnson Rita
Published: July 2020

Thin films of amorphous silicon oxide and silicon nitride are routinely used as gate dielectrics in silicon-based microelectronic devices. It is valuable to be able to image them and measure their thicknesses quickly and accurately. This brief note describes conditions that can be used to obtain accurate and reproducible TEM images of oxide-nitride-oxide (ONO) thin films.

Obtaining adequate contrast differences between oxide and nitride is not trivial because they have the same average atomic number, and both phases are amorphous. As stoichiometric compounds, both SiO2 and Si3N4 would have average atomic numbers equal to 10. For SiO2, (14+2(8))/3=10, and for Si3N4, (3(14)+4(7))/7=10. Thus, the atomic number contrast between these two is weak or nonexistent. Similarly, the amorphous character prevents the use of conventional diffraction contrast techniques.

However, the density of Si3N4 (3.2 g/cm3) is considerably greater than the density of SiO2 (2.6 g/cm3), reflecting the higher average coordination of N compared with O.
Microstructure of Pulsed-Laser Deposited Titanium Carbide Thin Films Grown for Tribological Applications
Authors: Adams P M , Radhakrishnan G
Published: July 2020

The carbides and nitrides of transition metals, are excellent candidates for hard coatings for tribological applications. Recently a novel pulsed laser deposition (PLD) technique has been developed for the room temperature growth of particulate free titanium carbide (TiC) coatings on bearing steels. On a completely different scale from ball bearing applications, moving microelectricalmechanical systems (MEMS) face issues of limited lifetime as a result of rapid wear of the silicon components. The integration of hard tribological coatings into moving MEMS structures should greatly increase the functional lifetime of these devices. The same PLD technique has been used to deposit TiC thin film onto MEMS test structures consisting of multilayer coatings on Si substrates, and patterned 3-D Si substrates. This procedure for growing TiC appears to be compatible with conventional MEMS fabrication procedures.
γ Phase Precipitation Processes in Quenched β Phase Cu-Zn-Al Alloys at an Electron Concentration of 1.53
Authors: Condó Adriana M , Arneodo Larochette Pierre , Tolley Alfredo
Published: July 2020

In the ternary Cu-Zn-Al alloys the bcc β phase is stable at high temperatures at electron concentrations (e/a) in the range from about 1.4 to 1.6 electrons per atom. Cu, Zn and Al atoms contribute with 1, 2 and 3 electrons, respectively. This region of stability is bounded by a β + γ twophase region at the high electron concentration border. If the P phase is retained at room temperature (RT) it transforms martensitically to a close packed structure. This transformation occurs without diffusion and provides information on the relative phase stability of the bcc and close packed structures. A detailed characterization of the microstructure of the parent bcc β phase and the martensite is thus essential for an adequate study of the transformation.

To retain the β phase at RT Cu-Zn-Al alloys must usually be quenched.
A Study on Precipitation in Clean Micro Alloyed Steels
Authors: Wang Yuanli , Liu Delu , Fu Jie , Zhu Jian
Published: July 2020

Much attention has been devoted to develop the new generation of microalloyed steels in recent years to meet the needs of high performance and low cost for the 21st century. The new type of steels is characterized by reduced carbon content, improved cleanness and refined grain size through the phase transformations.11'21 Precipitation of the carbonitrides in the steels is also one of the keypoints for controlling mechanical properties of the steels.

In the present work ultra-low carbon clean microalloyed steels, which contain 0.029∽0.047(wt)%C, 1.48∽1.54(wt)% Mn, 0.044∽0.052(wt)%Nb, 0.025∽0.044Ti(wt)%, 0.0015∽0.0020(wt)%B and 0.0045∽0.0070(wt)%N, were prepared in a vacuum induction furnace in laboratory. The contents of S and P of the steels are 0.0005(wt)% and 0.0010∽0.0024(wt)% respectively. Total amount of the impurity elements O, S, P and H in the steels is 0.0061∽0.0077%. Dominant component of the structure in both casting and as-forged samples is acicular ferrite or bainite.
Solid State Chemistry and the Electron Microscope: an Individual's Journey
Authors: Thomas John Meurig
Published: July 2020

From the late 1960s onwards the author embarked on a series of electron microscopic adventures using progressively more sophisticated techniques which yielded structural information and uncovered physics-chemical phenomena that would have been irretrievable by other methods. Illustrative examples include; (i) proof that photoreactivity and unexpected photoproducts of organic molecular crystals are governed by stacking faults, and that applied stress converts some photostable organic solid to photactive ones; (ii) elucidation of interdependence of photoluminesence and polymorphism in organic crystals; (iii) determination of surface pointdefect-concentration at, and discovery of catalytic channeling by metals in the oxidation of, graphite and molybdenite; (iv) establishing the mechanism of interconversion of “stages” in graphite intercalates, and the discovery of incommensurate guest-hosts-structures (with graphiteiron chloride); (v) rationalization of the structures of the many seemingly unrelated phases of bismuth molybdate catalysts (for oxidation) in terms of a common, defect-fluorite (Bi2O3) archetype;
Fine Structures of Zeolites and Mesoporous Materials
Authors: Terasaki Osamu , Ohsuna Tetsu , Kaneda Mizue , Sakamoto Yasuhiro , Hiraga Kenji , Carlsson Anna , Ryoo Ryong , Alfredsson Viveka , Anderson Michael W
Published: July 2020

Zeolites are crystalline aluminosilicates with frameworks built from corner-sharing TO4- tetrahedra(where T is Si or Al but can also be substituted with P, Ga, Ge, etc.) to produce channels or cavities of molecular dimensions. Owing to these characteristic features, zeolites have attracted much attention not only for catalytic applications but also as containers of confined materials. In most circumstances zeolites can only be synthesized as fine powders, ca. 1 μm, and the additional presence of defects or intergrowths makes structure solution difficult. HREM is therefore one of the most important tools for the investigation of such structures and the early work of Thomas and his group in Cambridge were dedicated to developing such techniques. The advantage of HREM has been subsequently demonstrated especially for characterizing and determining fine structures, e.g. (i) zeolite intergrowths structures such as ERI/OFF and FAU/EMT, (ii) enantiomeric intergrowths of structural units in ETS-10 and structural solution, (iii) surface structures and growth units and (iv) size of clusters and their registry with the framework structures.
Shyntesis and Characterization of Quantum Dot Superlattices
Authors: José-Yacamán M , Gutiérrez-Wing C , Santiago P , Ascencio J , Camacho A
Published: July 2020

The engineering of a new generation of advanced materials based on nanoparticles demands the fabrication of self-assembled arrays of passivated metal, oxide and semiconductor clusters (1 -). In particular the case of self-assembled gold clusters passivated with an organic molecule has attracted the attention of several researchers (2-3). Because its unique properties gold metal is a leading candidate for the fabrication of single electron tunneling devices.

Passivated gold nanoclusters were produced using the method developed by Brust et.al. (4) with the modifications of Whetten et.al (5) n-alkylthiol molecules were used as passivating agent. Carbon chains from C=4 to C=18 were used. It was found that C=12 dodecanethiol was optimum for forming ordered arrays of the clusters. To produce the superlattice crystallization a toluene vapor atmosphere was used. The passivated clusters were deposited on a copper electron microscope grid covered with carbon.
The Nanostructures Of Amorphous Silicas
Authors: Hobbs Linn W , Yuan Xianglong , Qin L C , Pulim Vinay , Coventry Alexander
Published: July 2020

Silicon dioxide is an important catalyst material, a mainstay insulator in microelectronics, and a widely distributed terrestrial and marine skeletal mineral. Geologically, it is found in one of a large number of polymorphic crystalline states, but can also be rendered “amorphous” by rapid cooling from the melt through a glass transition, depositing from a vapor or from solution (in radiolaria skeletons), oxidizing silicon, or irradiating with electrons, ions or neutrons. While the structures of the crystalline polymorphs are well documented, the structure of even the exhaustively studied vitreous silica remains largely enigmatic. Diffraction provides average information about short-range order—which appears to comprise [SiO4] tetrahedral units in all but a high-pressure crystalline polymorph—but is relatively insensitive to alternative medium-range arrangements of these structural units. One sensitive, but little understood, indicator is the position and shape of the first sharp diffraction peak (FSDP).
Aberration Corrected Lattice Imaging With Sub Ångstrom Resolution
Authors: Kisielowski C , Nelson EC , Song C , Kilaas R , Schwartzman A , Thust A
Published: July 2020

In 1999 NCEM's One Ångstrom Microscope (OAM) became fully operational. The OAM is a Philips CM300 FEG/UT field emission microscope with holographic capabilities that is equipped with a Gatan Image Filter (GIF) and operates at 300 kV. It was designed to reach a resolution close to the “magic barrier” around one Ångstrom (100 pm) by combining mid voltage technology with advanced computer processing [1,2]. Ahardware correction of the three-fold astigmatism allows for aberration free imaging down to sub Ångstrom values [3]. In this contribution it will be shown that the instrument's performance exceeded expectations because sub Ångstrom resolution can be achieved by reconstructing electron exit waves from focal series [4].

Figure la depicts a simulated [110] lattice image of a 90° partial dislocation in silicon. Tersoff potentials were used to calculate the exact atomic positions around dislocations with different core structures [5].
Asphaltene Aggregation Studies of Crude Oil Using 3-D Confocal Microscopy
Authors: Johnston Robert J , Mason Thomas G
Published: July 2020

Confocal laser scanning microscopy (CLSM) has been used to generate three dimensional projection maps of less fluorescent domains caused by asphaltene aggregates in the autofluorescent matrix of crude oil. Heavy crude oils contain asphaltene particles resulting in the production of optically observable micron sized asphaltene aggregates. This technique has been employed to determine the volume fraction of aggregated asphaltenes, øagg, and the time evolution of this phenomenon. The measurements cover a range of various concentrations of asphaltene volume fractions of the heavy asphaltenic oil, øm, from øm = 0 to øm = 0.6.

Examining crude oils for asphaltenes aggregates using CLSM presents a challenge due to the strong absorption of the oils. This is because some molecules of the crude oil fluoresce when excited by optical laser light used as a source in the CLSM. Other molecules of the crude oils absorb light at similar wavelengths.
Chemical Compostion Analysis on Sintered Gold and Platinum Nanoparticles
Authors: Lu S , Yao N , Aksay I A
Published: July 2020

Nanoparticles continue to attract interests because they fall into intermediate stage between molecular and macroscopic materials. Due to their large surface-to-volume ratio, nanoparticles exhibit physical and chemical properties that differ markedly from those characterizing the bulk solid state. One example is the phase diagram of a nanomaterial. Because nanocrystals display clear changes in both the thermodynamics and the kinetics of phase transitions, we expect different solubility limits in the nanometer regime. This means that phases unstable or unobserved in extended solids may be prepared as nanocrystals. We synthesized Au and Pt nanoparticles and performed chemical analysis on the sintered agglomerates.

The colloidal Au and Pt particles were synthesized according to Turkevich's method. An aqueous AuCl3 solution (50mg Au/L) was heated to 70°C. A determined amount of lwt% aqueous sodium citrate dihydrate (Na3C6H5O7.2H2O) solution was added such that the citrate-to-Au mass ratio was 10.
In Situ and Ex Situ Microscopic Study of Propylene Polymerization With Heterogeneous Mgcl2-Supported Ziegler-Natta Catalysts
Authors: Oleshko V , Crozier P , Cantrell R , Westwood A
Published: July 2020

The large-scale commercial production of polyolefins by catalytic Ziegler-Natta polymerization have stimulated the development of the third, fourth and fifth generation heterogeneous catalysts comprising high surface area defective MgCl2 with TiCl4, electron donors, and AlR3-co-catalysts. In spite of intensive research over the years, the present level of understanding of the catalysts is still incomplete because of their complex composition leading to a multitude of local active site environments. The aim of this work is to provide a new insight into the process via in situ video microscopy of gas phase propylene polymerization over MgCl2-supported Ziegler-Natta catalysts combined with ex situ characterization by light and electron microscopy techniques (SEM, TEM, HRTEM, STEM, PEELS and windowless EDX). Procedures for catalyst synthesis are described elsewhere. The catalysts were stored in a dry box under a He atmosphere (<lppm H2O/O2). Samples were transferred to specimen holders in the dry box and then transferred into the microscopes under high purge N2 conditions to prevent poisoning of the catalysts by air and moisture.
Image Reconstruction From TEM Diffraction Patterns Using Feinup Algorithm
Authors: Chen Q , Weierstall U , Spence J C H
Published: July 2020

Iterative algorithms, which use diffracted intensities and some a-priori knowledge of an image to solve the phase problem, have been under development for many years. The promised super-resolution images, reconstructed from diffraction information alone, would be of the greatest value for molecular imaging and for the image of nonperiodic structures in materials. Using simulated data it is possible, for example, to reconstruct a complex object from a knowledge of its diffracted intensities with certain known support functions. Some success has recently been achieved reconstructing micrometer-sized non-periodic objects using coherent X-rays by the Feinup method. One favorable support function consists of two holes spanned by the coherence width of the beam, with one or both holes containing an unknown object. Our simulations, which iterate between diffracted intensities and the image, applying the known support (either completely opaque or completely transparent) and intensities in each domain, confirm that image reconstruction is possible for loose supports and noiseless data.
In-Situ Characterization of Carbon Nanotube-Polystyrene Composite Deformation
Authors: Qian D , Dickey E C , Andrews R , Rantell T , Safadi B
Published: July 2020

Carbon nanotubes (NTs) have novel electronic properties and exceptionally high Young's moduli on the order of TPa. so NTs have potential applications in advanced composite materials such as conductive polymers, electromagnetic-radio frequency interference (EMI/RFI) shielding material and opto-electronic materials. The utility of the nanotubes in composite applications depends strongly on the ability to disperse the NTs homogeneously throughout the matrix without destroying the integrity of the NTs. Furthermore, interfacial bonding between the NT and matrix is necessary to achieve load transfer across the interface, which is desirable for improving the mechanical properties of polymer composites.

In this work, aligned multiwalled carbon nanotubes (MWNTs) produced by continuous chemical vapor deposition (CVD) (see Fig.l), were homogeneously dispersed in polystyrene (PS) matrices by a simple solution-evaporation method. Using this procedure, we made uniform MWNT-PS composite films ∼0.4mm thick for ex-situ mechanical tensile test and very thin films, ∼100nm, for in-situ TEM tests, as shown in Fig.2.
CBED Study of Mn3+ Orbital Ordering in LaMnO3
Authors: Jiang B , Zuo JM , Chen Q , Cheong S-W , Spence JCH
Published: July 2020

Mn oxides of pervoskite-related structure containing Mn ions have attracted considerable interest due to the colossal magnetoresistence (CMR) effect. Doping the family of compounds La1-x Cax MnO3 with divalent Ca ion oxidizes Mn+3 to Mn4+, introducing holes in the 3d bond orbital that give rise to a series of interesting physical properties. The parent compound LaMnO3 (Pbnm) with unit cell of a=5.5367Å b=5.7473Å and c=7.6929Å, is an antiferromagnetic insulator in which orbital ordering is established due to the cooperative Jahn-Teller (JT) effect breaking the degeneracy of the electronic configuration of Mn3+ (t2g3eg1). This particular C-type orbital ordering is responsible for the A-type magnetic structure observed by Wollen and Kohler. Theoretical Monte-Carlo simulation has shown that the A-type antiferromagnetic state is stable in a model based on JT phonons, using coupling values physically reasonable for LaMnO3 and considering the small but important effect of octahedral tilting.
As-Quenched ARC Products By bulse - Discharge
Authors: Murooka Y , Maede Y , Ozaki M , Hibino M
Published: July 2020

Since their discovery, steady state arc discharge has been used for fullerenes and nanotubes production. Unfortunately this method intrinsically made it difficult to understand their growth mechanisms since the discharge included many complicated physical processes and the growth happened in the non-equilibrium arc plasma. Processes such as heating of the cathode by cation bombardment, emission of thermal electrons, and heating of the anode by electron bombardment are important in order to follow the mechanism, but it is difficult to study them separately. In the present work, however, it was shown that a pulse-arc discharge with a small current for a short time could simplify the discharge process and provide as-quenched arc products, which should be useful to understand the mechanisms.

Short discharges with a small current were performed on the pulse-arc system, which was developed by the authors.
One, Two, and Three Demisional Gold Nanoparticle Arrays from Reverse Micelles
Authors: Zhou WL , Lin J , O'Connor CJ
Published: July 2020

Nanoparticles (1-100 nm) of semiconductors and metals have shown some unique optical, electric and magnetic and catalytic properties which are greatly different from their bulk materials. Recently the use of these nanoparticles as quantum dots in nanoelectronics requires their arrangement in one, two, and three dimensions (1D, 2D and 3D). Therefore more attention has been paid to the organization of these nanoparticles into ordered arrays in order to achieve novel collective properties. Gold colloids have been well studied for its self-organization in several systems. Here we present 1D, 2D and 3D gold self-organization nanostructure generated from reverse micelles (microemulsion system).

Gold nanoparticles were prepared by the reduction of HAuCU in CTAB (cetyltrimethylammonium bromide)/Octane+l-Butanol/H2O microemusion system using NaBH4 as the reducing agent. Typically, 0.3g of CTAB, 0.148ml of 0.056M HAuCl4 aqueous solution, l.Og octane (surfactant) and 0.25g 1-butanol (cosurfactant) were mixed together and stirred vigorously for 10 min until a homogenous phase was obtained.
SEM and TEM of Metallic Inverse Opals
Authors: Blanford CF , Yan HW , Stein A , Carter CB
Published: July 2020

Drawing on nature, synthetic opals (e.g., gilsonite) consist of uniformly sized ceramic spheres ordered into large close-packed domains. In order to improve the toughness or appearance of these chemically bonded ceramics, a polymer is often infiltrated into the interconnected space between the packed spheres. In a similar fashion, colloidal crystal arrays of submicrometer silica or polymer spheres have been employed as templates for periodic porous solids. All the methods for preparing periodic macroporous materials share a common synthetic thread: first, the colloidal crystals are formed from monodisperse spheres; next, the void spaces are filled and solidified; finally, the template is removed by heat, by refluxing in a solvent such as THF (in the case of polymer spheres), or by soaking in hydrofluoric acid (in the case of silica spheres). The product, which can be thought of as an “inverse opal,” often exhibits the same iridescence as a natural opal due to the similarity between the periodicity of the wall structure and the wavelength of light.
Calcium Release and Spread Within the Sarcomere of Vertebrate Skeletal Muscle Fibers.
Authors: Baylor Stephen M , Hollingworth Stephen
Published: July 2020

Experiments were carried out to investigate excitation-contraction coupling in vertebrate skeletal muscle fibers. Single-dissected twitch fibers of frog muscle were injected with flourescent calcium (Ca) indicators, and fluorescence intensity (F) and changes in intensity (ΔF) were recorded during various stimulation protocols (16-22 °C). In fibers activated by an action potential, the low-affinity indicator furaptra was used to estimate the spatially-averaged change in myoplasmic free calcium concentration (ΔC[a]; peak value, 15-20 μM; time to peak, 4-5 ms). Δ[Ca], in combination with a kinetic model, was used to calculate the change in concentration of calcium bound to the principal myoplasmic Ca buffers (ATP, troponin, parvalbumin). The rate of Ca release from the sarcoplasmic reticulum (SR) was obtained from the time derivative of the estimated change in total myoplasmic calcium concentration, Δ[CaT] (= Δ[Ca] + Δ[CaATP] + Δ[CaTroponin] + Δ[CaParvalbumin]).
New Projects for Superstem
Authors: Brown L M , Bleloch A L
Published: July 2020

It is proposed to build two high-performance general-user instruments at Daresbury, Cheshire, where the present U.K. synchrotron facility is located. The instruments can be used on-site, where accommodation for visitors is already available. They can also be used remotely, via the internet. The features of the instruments are: aberration-corrected optics, voltage-stabilised electron spectrometer, and multi-specimen stages to facilitate rapid throughput of routine work. We anticipate that a sub-Angstrom probe size will be available for incoherent HAADF imaging, and PEELS with an energy resolution better than 0.3V for losses up to 2kV. The operating voltage will be l00kV.

The new instruments will allow better analysis of continuing problems. Anticipated developments are as follows:

1. Study of helium bubbles in reactor materials: Recently, accurate quantification of helium has been achieved and a quantitative explanation has been given for the ‘blue shift’, that is, the increasing threshold energy for the Is to 2p transition due to quantum confinement of the excited state with increasing gas pressure.
Electron Scattering with an Atomic Sized Probe
Authors: Silcox J
Published: July 2020

It is the presence of local variations in atomic and electronic structure that often gives rise to intriguing properties of materials. Control of material properties then rests on detection of the local variations in the materials, determination of the origin of those variations and then understanding how such variations can be controlled to achieve a desired functionality. Recent examples using STEM with an atomic sized probe (∼2.2 Å) include studies of the bonding at grain boundaries in nickel rich Ni3Al doped with boron. EELS measurements revealed changes in the d-hole density-of-states that were used to estimate changes in the electronic contribution to the grain boundary energy. These changes in grain boundary strength correlated with a change in fracture from an intra- to an inter-granular mode. In another example, the observation of metal induced gap states at Cu/MgO interfaces provided evidence that the dipole moment across that interface was relatively low.
Non-Stoichiometry at Tilt Grain Boundaries in SrTiO3
Authors: Duscher G , Kim M , Browning N D , Pantelides S T , Pennycook S J
Published: July 2020

The origin of electrically active grain boundaries in perovskite oxides and related materials remains controversial. The stoichiometry of the grain boundary core structure and the role of oxygen vacancies are the key issues involved. Previous results have given no indications of any non-stoichiometry at SrTiO3 grain boundaries, despite the fact that SrTiO3 is the system where atomic column EELS resolution has been demonstrated [1], and where atomic resolution images of the core structures have been obtained by Z-contrast imaging [2,3]. Here we show EELS spectra from individual dislocation cores in an 8° [100] tilt grain boundary in SrTiO3 that show significant oxygen depletion.

The low angle grain boundary with well-separated dislocation cores makes it possible to study individual cores with high energy resolution in EELS. Previous work either averaged over all structural units in the grain boundary, sacrificing spatial resolution [2,3], or, used a very low probe current to obtain the highest spatial resolution [1].
The Hitachi HD-2000 in Semicondutor Manufacturing Support and Research.
Authors: Vanfleet RR , Vartuli CB
Published: July 2020

A Hitachi HD-2000 dedicated STEM with a cold field emission source was installed last fall at the Lucent Technologies Semiconductor Fab site in Orlando. The close relationship between the Orlando arm of Lucent Technologies and the University of Central Florida has and will allow this instrument to be evaluated for its usefulness in two roles: Support of the development and fabrication needs of a semiconductor fabrication facility and the research needs of University based Materials research.

This Hitachi instrument was specifically designed to meet the needs of the semiconductor industry. Sample holder compatibility with the Hitachi Focused Ion Beam (FIB) allows rapid swapping between the two tools. A large solid angle Energy Disperse X-ray Spectrometer (EDS) supports increased resolution and sensitivity of X-ray analysis. Direct digital acquisition speeds image and data transfer to the end user. All these and other features speed the turn around time and usefulness for manufacturing line feedback.
Atomic Scale Grain Boundary Analysis by Incoherent Imaging With TEM/STEM
Authors: Kawasaki M , Yamazaki T , Watanabe K , Shiojiri M
Published: July 2020

Quantitative compositional characterization was carried out on a ceramic boundary using atomic resolution high-angle annular dark field scanning transmission electron microscopy (HAADFSTEM), with the aid of HAADF image simulation. HAADF-STEM observation was performed with a JEM-2010F TEM/STEM equipped with a field emission gun and an HAADF detector. And also the image simulation for HAADF was made on a computer by the program that was developed by the authors using Bethe's method.

The material used in this experiment that was provided by TDK Co., is a semiconducting SrTiO3 (STO) ceramic condenser. The bulk substance was formed by the process of sintering in a reduced ambience followed by the reoxidization in the air after surface coating with Bi2O3, PbO and CuO compounds resulting in having a unique structure with Bi diffusion layers at the grain boundary region.
Nanometer-Scale Cathodoluminescent Properties Through Z-Contrast Scanning Transmission Electron Microscopy
Authors: Gao H-J , Duscher G , Kim M , Kumar D , Singh RK , Pennycook SJ
Published: July 2020

Interest in rare earth-activated oxide-based phosphor thin films for high-resolution display devices has been growing in the last few decades. However, thin-film phosphors typically have a significantly reduced brightness compared to equivalent powder phosphor materials. Several possible explanations have been suggested for the lower brightness including internal reflection and the small interaction volume between the incident beam and the solid. In this report, we show another factor to be crucial to external radiative efficiency, the porosity of the films. Porosity creates internal surfaces that act as a "dead layer" which decreases the emission efficiency. Using Z-contrast imaging in the scanning transmission electron microscope (STEM) with simultaneous cathodoluminescence (CL) imaging, the dead layer is directly observed, and quantitative accounts for the reduction of luminescent efficiency.

Eu activated Y2O3 thin films with thickness of about 200 nm were deposited on (001) LaAlO3 substrates by laser ablation. TEM analysis of the samples was conducted in a Philips EM-400 electron microscope operated at l00kV.
Why Diffraction-Contrast of Defects is a Sad Song and How to Make it Better
Authors: Eades J A
Published: July 2020

Modern TEM's are not suited for the taking of diffraction-contrast images of defects. Figures in books and papers taken more than a quarter century ago show defects (dislocations, small precipitates and so on) against a uniform background, reflecting constant diffraction conditions across the field of view. Such pictures can not be taken today. Even if the sample is quite flat, TEM images are crossed by “bend contours” which arise, not from the bending of the sample, but from the changing orientation of the beam. In modern TEM's, the objective lens is an immersion lens. The sample sits deep within the magnetic field of the lens and, thus, the electrons are travelling in a helical pattern as they strike the sample. Even with a so-called parallel beam, at different places across the image, the electrons strike the sample at different angles (see figure 1).
Recent Developments in Failure Analysis in an Ultra thin Film Evaluation System
Authors: Kamino T , Konno M , Yaguchi T , Hashimoto T , Tanaka H , Nakamura K
Published: July 2020

The increased demand in the microelectronics industry for higher spatial resolution in the analysis of device defects has focused attention on the use of transmission electron microscopy(TEM). However, in contrast to scanning electron microscopes(SEM), the number of TEM units in the microelectronics industry is still limited. This is because TEM operation and TEM specimen preparation are rather complicated and the results dependent upon operator experience.

A innovative solution using a dedicated ultra thin film evaluation system(HD-2000) based upon a 200kV cold field emission scanning transmission electron microscopy(STEM) technique has been developed[1]. The system has STEM image resolution of 0.24nm and 0.3nm spatial resolution for elemental analysis using energy dispersive X-ray(EDX) spectroscopy with 0.3sr collection solid angle. The system therefore allows materials characterization to be performed at atomic resolution. Another advantage of the system is the ease of use due to newly developed PC-SEM operation software.
Electron Beam-Induced Chemical Reactions Of Single Crystal Calcium Floride By Time - Resolved EELS
Authors: Murooka Y , Tanaka N , Hibino M
Published: July 2020

Using parallel beam illumination, electron beam-induced structural transformation has been studied as radiation damages for decades. Recently, however, more attention may need to be paid to beam-induced chemical transformation which happens under illumination by a finely focused beam. Such a small probe is often used in analytical electron microscopy, particularly the core-electron energy loss spectroscopy (EELS). Since the signal for the spectroscopy is very weak long radiation is required and makes the induced chemical reactions happen. Therefore, without attentions to the reactions, the acquired data could lead to misinterpretation of specimen properties. In the present study, using a single crystal calcium fluoride (CaF2), we demonstrated by time-resolved EELS that radiation with a nanometer electron probe could induce chemical reactions between the specimen and the typical residual gases in a microscope column.

The thin films of CaF2 were fabricated by vaporizing flakes of single crystal CaF2 with an electron beam and by dissolving the vapors onto a (001) surface of sodium chloride (NaCl) heated at 300°C.
Image-Spectroscopy: Applying EELS Analysis Techniques to EFTEM Series
Authors: Thomas PJ
Published: July 2020

The energy-loss spectrum of transmitted electrons contains a wealth of information regarding the physical, chemical and electronic properties of the medium under analysis. It provides a powerful means for materials characterisation in the TEM by use of electron energy-loss spectroscopy (EELS) or its spatially parallel counterpart, energy-selective imaging (ESI). Essentially, both analyses probe the same core-loss information, recording transmitted intensity / as a function of energy-loss E and spatial position x, y, to yield a three-dimensional data set I(E, x, y). Acquisition of an extended series of energy-selected images across the energy-loss range of interest has been shown to provide useful spectral as well as spatial information, with the resolution of extracted ‘image-spectra’ being determined by the energy interval between acquisitions and the width of the energy-selecting slit, as illustrated in Figure la. This mode of analysis, termed ‘image-spectroscopy’ is directly analogous to spectrum-imaging in the STEM, and offers many advantages over conventional two- or three-window elemental mapping techniques.
Nanometer Crystal Structure Analysis by EF-CBED and EF-Microscopy
Authors: Tsuda K , Tanaka M
Published: July 2020

Crystal structure refinement by the convergent-beam electron diffraction (CBED) method has the following advantages: (i) Nanometer-size crystal structure refinement: CBED patterns can be obtained from specimen areas of a few nanometer in diameter, (ii) Dynamical diffraction effect: the CBED intensities contain phase information of crystal structure factors through the strong dynamical effect. (iii) Site-selective analysis: the use of Bloch states formed by incident electrons allows structure determination weighted for specific atom sites. Energy-filtering (EF) to revome inelastically scattered background is now getting necessary for such quantitative analysis of CBED patterns. Especially for the determination of atom positions and Debye-Waller factors, the use of energy-filtered higher-order Laue zone (HOLZ) CBED patterns is essential because small displacements of atoms can be sensitively detected using HOLZ reflections with large reciprocal vectors. For this purpose, we developed a new fl-filter transmission electron microscope (JEM-2010FEF) with a high acceptance angle [2] and a new analysis program “mbfit” to refine structural parameters using many-beam Bloch-wave calculations and least-square fitting [1].