bluuebunny/crossref_metadata_2025_split huggingface dataset:
Si(111)-(5x2) Au structure from off-axis high-resolution Transmission
Electron Microscopy
Authors: Plass R. , Marks L. D. 
Published: June 2020

Although metal semiconductor interfaces play a major role in semiconductor device performance the basic understanding of the atomic structure of many of these interfaces has been elusive. The submonolayer of gold on silicon (111) system is of special interest as it displays several different surface structures depending on gold coverage and temperature. Substantial light has been shed on one of these structures, the 5×2 present between .1 and .5 gold monolayers, in recent x-ray diffraction and high resolution STM studies, yet the placement of the gold atoms remains unclear. We present here a solution for this structure found using off-axis plan view HREM and digital image restoration in combination with more conventional bright-field, dark-field imaging and diffraction techniques.Instrumental details related to this experiment have been reviewed by Bonevich and Marks. Si 111 oriented TEM samples with clean, fairly flat surfaces were prepared using Ar+ ion sputter/electron beam annealing cycles.
Analytical Electron Microscopy of Monolayer Surface Segregation in Alloy Nanoparticles
Authors: Lakis R. E. , Lyman C. E. , Stenger H. G. 
Published: June 2020

Alumina-supported Pt-Rh alloy catalysts are widely utilized for air pollution control and are particularly effective for the reduction of nitric oxide (NO) at temperatures below 300°C. The alloy particles of interest are present in the size range of l-15nm in diameter. A catalyst that was observed to contain only Pt-rich alloy particles, performed better than catalysts which contained Rh-rich alloy particles or a mixture of Pt-rich and Rh-rich particles. The reaction data suggested that Rh may have segregated to the surface of the individual Pt-rich alloy particles. This observation is consistent with the literature on the Pt-Rh system. However, there are no traditional surface sensitive techniques (e.g. XPS, AES) which possess both the spatial resolution and the depth resolution required to observe surface segregation in 1-15nm particles. The goal of this study is to determine if this segregation could be observed by analytical electron microscopy in a dedicated STEM.The composition-size distributions of several catalysts were measured using a VG-HB501 scanning transmission electron microscope (STEM).
Structure and chemical composition of Pt-Ru nanoparticle supported on carbon black
Authors: Radmilovic V. , Gasteiger H. , Ross P. 
Published: June 2020

The presence of nanoparticles in catalyst systems is essential because their large surface area increases the reaction rate of the catalyst. However, such a small size of the particles causes serious limitations in microstructural characterization, that could be overcome by high resolution electron microscopy (HREM), especially for particle morphology studies, presence of faults, etc. The present study uses HREM, microdiffraction and EDS techniques to characterize the Pt-Ru catalyst supported on amorphous carbon black. In order to get structural information from local region of single particle optical diffraction has been also performed. HREM imaging allows the particle morphology and the presence of various structural defects to be revealed. To avoid contamination, microchemical analysis has been performed at -160°C, using cold stage beryllium holder. The fluorescence effect can be neglected.Fig. 1 shows that some of Pt-Ru particle in a catalyst containing 20 % of metal mass and having ratio Pt:Ru=3:l, exhibits pronounced microfaceting on 111 and 100 type planes (see Fig. la), forming equilibrium cubo-octahedron shape.
Flux-pinning related defects in YBa2Cu3O7-x thin films grown on miscut LaA1O3 substrates
Authors: Wang Z. L. , Christen D. K. , Klabunde C. E. , Kroeger D. M. , Lowndes D. H. , Norton D. P. 
Published: June 2020

Measurements of critical current density in YBa2Cu3O7-x (Y123) thin film grown on slightly (1.6 deg) miscut LaA1O3 {001} substrates have shown an anomalous angular dependence of Jc. A strong, magnetic field-dependent peak in Jc is observed when the magnetic field is oriented between the c-axis (the film normal direction) and the a-b plane, an orientation where flux pinning normally is not strong. Scanning tunneling microscope images of the films showed tilted-platelet microstructures, suggesting that the films might contain highly oriented internal growth defects, induced by the miscutaligned growth. This array of defects may be responsible for the strong flux pinning and high Jc. In this paper, high-resolution transmission electron microscopy (HRTEM) is applied to study the defect structure formed in the films.HRTEM studies were performed at 300 kV in a Philips CM30 TEM/STEM with image resolution 2.3 Å. The {001} Y123 films of thickness - 0.5 μm were grown on miscut LaA1O3 {001} substrates. Cross-sectional TEM specimens were prepared in order to examine the relationship between the substrate steps with the observed defects.
SEM and SAM observation of S-adsorbed Cu3Au (110) surface
Authors: Huang Y. , Cowley J. M. 
Published: June 2020

The behavior of impurities on the surfaces is an important topic in surface science. Cu3Au is a typical ordering bimetalic alloy whose bulk and clean surface have been extensively studied.This make it a good material for studying the effect of impurities such as sulfur on the properties of the alloy surfaces. Some work has been done by the present authors on the structure and compositionchange of the Cu3Au (110) surface with the sulfur adsorption . It was found that when S isadsorbed on the surface the ratio of the surface Au concentration over Cu concentration decreases drastically. The reason of this change was explained as movement of Au atoms into the bulk and Cu atoms from the bulk to the surface due to the difference in the affinity of Au and Cu for S.The previous observations were based on macroscopic RHEED and AES techniques, the information was averaged over a large area. In order to obtain more localized information such as surface morphology andthe element distribution, secondary electron microscopy (SEM) and scanning Auger microscopy (SAM) were used to study the clean and S-adsorbed Cu3Au (110) surfaces. The experiment was carried out in a modified UHV VG HB501.
The long-period structure on ordering alloy surfaces
Authors: Huang Y. , Cowley J. M. 
Published: June 2020

The long-period structure (LPS) has long been known to exist in bulk ordering alloys such as CuAu and Cu3Au. in the structure the ordered lattice shifts back and forth by a vector every M unit cells and forms a super cell 2M unit cells long. The planes where the lattice shifts are usually called antiphase boundaries (APBs) and the LPS can be regarded as periodically arranged antiphase domains. This superstructure can be detected by the splitting (∝1/M) of some superlattice spots in the diffraction panern. One may ask whether the LPS also occurs on the surface; if so, what is its effect onthe diffraction pattern. The answer to them is important to explain some unknown features observed in the RHEED experiment. They also have significance for the surface transition theories.Ideal termination of a LPS Cu3Au crystal gives a surface first-layer atomic arrangement shown in fig.1a. In this arrangement the basic vectors a and b of the surface hexagonal ordered structure are two bulk {110} vectors. Every M unit cells in a direction the lattice shifts by(1/2)b. This forms the 2-D super unit cell with a size of 2Ma×b. The relatively shifted areas are actually 2-D antiphase domains. The boundaries between them are the periodically arranged linear APBs. All these features indicate that the ideal Cu3Au(111) surface is indeed a 2-D LPS. Fig.1b and 1c show the 2-D reciprocal lattice calculated from the above surface arrangement.
Identifying groups of airborne particles by ordination
Authors: Shlepr M. , Vicroy C. M. 
Published: June 2020

The microelectronics industry is heavily tasked with minimizing contaminates at all steps of the manufacturing process. Particles are generated by physical and/or chemical fragmentation from a mothersource. The tools and macrovolumes of chemicals used for processing, the environment surrounding the process, and the circuits themselves are all potential particle sources. A first step in eliminating these contaminants is to identify their source. Elemental analysis of the particles often proves useful toward this goal, and energy dispersive spectroscopy (EDS) is a commonly used technique. However, the large variety of source materials and process induced changes in the particles often make it difficult to discern if the particles are from a common source.Ordination is commonly used in ecology to understand community relationships. This technique usespair-wise measures of similarity. Separation of the data set is based on discrimination functions. Theend product is a spatial representation of the data with the distance between points equaling the degree of dissimilarity.
Quantification of micromagnetic structure from Lorentz micrographs
Authors: Zweck J. , Herrmann M. , Hoffmann H. 
Published: June 2020

Defocused imaging of magnetic domain structures is a well-known technique to observe the micromagnetic structures in ferromagnetic thin films. Nevertheless, Lorentz microscopy images are rarely subject to a quantitative evaluation of micromagnetic parameters. In this paper, we offer a new method for quantitative evaluation of ripple wavelengths and ripple angle from Lorentz microscopy images carried out on soft magnetic Ni81Fe19 films. The work was carried out using a Philips CM30 electron microscope with a combined Twin/Lorentz lens.The experiments were performed on thin ferromagnetic films of a Ni81Fe19 alloy. Due to the internal magnetic induction within the specimens, the partial electron waves experience a phase shift proportional to the local in-plane magnetic induction , the specimen's thickness t and the lateral distance x from an arbitrarily chosen point of zero phase shift on the specimen. This phase shift can then be imaged using phase contrast methods similar to HREM. Since the phase shifts and the corresponding deflection angles can be very small, a large defocus is necessary to obtain contrast. This large defocus gives rise to an oscillating phase contrast transfer function for the spatial frequencies under observation as well as to a damping envelope for higher spatial frequencies.
Automatic analysis of Kikuchi diffraction patterns
Authors: Weiland H. , Field D. P. 
Published: June 2020

Recent advances in the automatic indexing of backscatter Kikuchi diffraction patterns on the scanning electron microscope (SEM) has resulted in the development of a new type of microscopy. The ability to obtain statistically relevant information on the spatial distribution of crystallite orientations is giving rise to new insight into polycrystalline microstructures and their relation to materials properties. A limitation of the technique in the SEM is that the spatial resolution of the measurement is restricted by the relatively large size of the electron beam in relation to various microstructural features. Typically the spatial resolution in the SEM is limited to about half a micron or greater. Heavily worked structures exhibit microstructural features much finer than this and require resolution on the order of nanometers for accurate characterization. Transmission electron microscope (TEM) techniques offer sufficient resolution to investigate heavily worked crystalline materials.Crystal lattice orientation determination from Kikuchi diffraction patterns in the TEM (Figure 1) requires knowledge of the relative positions of at least three non-parallel Kikuchi line pairs in relation to the crystallite and the electron beam.
Toward a neuroscope: An application of high-performance computing for real-time evaluation of brain function using MRI
Authors: Potter C. S. , Gregory C. D. , Morris H. D. , Liang Z.-P. , Lauterbur P. C. 
Published: June 2020

Over the past few years, several laboratories have demonstrated that changes in local neuronal activity associated with human brain function can be detected by magnetic resonance imaging and spectroscopy. Using these methods, the effects of sensory and motor stimulation have been observed and cognitive studies have begun. These new methods promise to make possible even more rapid and extensive studies of brain organization and responses than those now in use, such as positron emission tomography.Human brain studies are enormously complex. Signal changes on the order of a few percent must be detected against the background of the complex 3D anatomy of the human brain. Today, most functional MR experiments are performed using several 2D slice images acquired at each time step or stimulation condition of the experimental protocol. It is generally believed that true 3D experiments must be performed for many cognitive experiments. To provide adequate resolution, this requires that data must be acquired faster and/or more efficiently to support 3D functional analysis.
Pattern recognition in HREM analysis of grain-boundary structures
Authors: Paciornik S. , Kilaas R. , Turner J. , Dahmen U. 
Published: June 2020

The present study focuses on an application of pattern recognition techniques to the detection of structural units in grain boundaries and in heterophase interfaces. It describes a simple means of extracting the essential characteristics of an interface from a high resolution image, to find the location, repeat distance and degree of similarity between such units and to sum them into an average unit with increased signal to noise ratio. A measurement of the discrimination between different crystallographic structures can also be obtained from a histogram of the processed image.Usually the procedure is composed of three steps. In the first the user selects a structural unit of interest and the program scans it over the original image to obtain a real-space cross-correlation (CC) coefficient map. This map will consist of bright spots where the template matches the underlying image and dark spots otherwise. In the second step an automatic peak-finding procedure is used to locate the positions of best match.
A review of Schottky and cold field-emission cathode characteristics
Authors: Swanson L. W. 
Published: June 2020

Two high brightness, point cathodes currently being used in TEM's and nanometer electron focusing systems are the cold field emission (CFE) and Schottky emission (SE) cathodes. In terms of emission mechanisms, CFE and SE represent two extremes of a continuous change in surface electric field strength F and temperature T of a pointed cathode of work function ϕ. The conditions for CFE and SE emission modes can be stated as follows:CFE: 4π(2mϕ(1/2 kT/heF < 0.5SE: he1/4F3/42<2m1/2 < 0.5When the above conditions are met most electrons are tunnelling from at or near the Fermi level inthe case of CFE and thermally excited over the vacuum barrier in the case of SE. The expressions for the current density J are:CFE: JCFE = a(F2/ϕ)exp(10.4/ϕ1/2)exp(-bϕ3/2/F)(A/cm2SE: JSE = 1202exp(-(ϕ - 3.8F1/2)/)kT)(A/cm2)where a = 1.54×10-6, b = 0.644 and F and ϕ are in units of V/Å and eV respectively.One important aspect for source optics applications is the energy spread of the emitted electrons for the two emission regimes. Fig. 1 gives the theoretical values of the full width at half maximum (FWHM) of the energy distribution for the case of CFE with ϕ = 4.0 eV, T = 300 K, J = 1×105 A/cm2 and SE with ϕ = 3.0 eV, T = 1800, J = 1×103 A/cm2.
Extending the limits of molecular microanalysis
Authors: Blackson J. H. , Susnitzky D. W. , Beaman D. R. 
Published: June 2020

Modern polymer blends are frequently composed of domains and interfacial phases having submicron dimensions. Previously, die characterization of specific unknown submicron polymer phases has been limited to selective staining methods that help to classify the phase but rarely lead to chemical identification. The present procedure uses parallel detection electron energy loss spectroscopy (PEELS) to perform submicron molecular microanalysis on beam sensitive materials. Polymer domains are first differentiated by their elemental composition and then by their characteristic carbon core loss edge structure. These spectra are compared to spectra recorded from polymers of known composition.A polymer film composed of alternating 0.5 μm layers of polycarbonate (PC) and polymethylmethacrylate (PMMA) was used as a test specimen (Fig. 1). Ultra-thin sections (<50 nm) were prepared by microtomy, collected on unsupported 600 mesh copper grids and examined at −160°C usinga VG HB601UX dedicated STEM fitted with a Gatan 666 UHV PEELS. The combination of beam blanking, simplecontrol of electron dose, UHV, low energy spread FEG, stage stability and the ability to produce a high contrast image at a very low electron dose makes this instrument ideally suited for this experiment.
A new method for quantitative analysis of EELS
Authors: Luo Suichu , Joy David C. 
Published: June 2020

Techniques to remove plural scattering from electron energy loss spectra (EELS) are important in bot hmicroanalysis and other quantitative applications of electron spectroscopy. The techniques used are either based on convolution, or Fourier transform deconvolution, methods, in which either the elastic scattering angular correction or both elastic and inelastic angular corrections are not included. In this work we propose a new method based on both angular and energy loss three-dimension Poisson statistics which includes elastic and inelastic mixed angular scattering correction in order to obtain more accurate quantitative analysis for EELS.The electron scattering distribution determined by angular and energy loss three-dimension Poissonstatistics is given by:where ITis the total incident electron intensity; t is the sample thickness; λi, λeand λTare inelastic , elastic and total scattering mean free paths; Si(θ) and Se(θ) are normalized single inelastic and elastic angular scattering distributions respectively, F(E) is the single scattering normalized energy loss distribution.
Energy-filtered chemical mapping: Current applications to materials science
Authors: Crozier P. A. 
Published: June 2020

Elemental mapping is a powerful technique for elucidating the distribution of elements on the nanometer scale in materials with complex morphologies. In electron microscopy, mapping is usually performed on a scanning transmission electron microscope (STEM) fitted with a field emission gun (FEG) using the techniques of energy-dispersive x-ray spectroscopy (EDX) or electron energy-loss spectroscopy (EELS). However, recent advances in spectrometer design and digital image recording have stimulated renewed interest in energy-filtered imaging and elemental mapping with a conventional transmission electron microscope. Here, some applications of energy-filtered chemical mapping in materials science are described.Experiments were conducted on a Zeiss 912 operating at 120 kV with a thermal source and equipped with an omega filter spectrometer. A variable width slit in the spectrometer image plane allows energy-filtered images to be formed on the microscope viewing screen. These images are digitally recorded using a Gatan 679 slow-scan CCD camera with 1024 pixels.
Quantiative analysis of grain boundaries in YBa2Cu3O7-δ using a 20Å high-resolution probe
Authors: Zhu Yimei , Moodenbaugh A. R. , Zuo J. M. , Suenaga M. 
Published: June 2020

One challenge for high Tc superconductor research is to overcome the low intergranular transport currents which hinder practical applications. Evidence shows that lattice mismatch at the boundaries contributes to the depletion in charge carriers (holes), while the strain fields surrounding the cores of boundary dislocations suppress the superconducting order parameter. Using high-spatialresolution EDX, EELS and CBED techniques with a 20 Å field emission probe, we studied cation segregation, variations in oxygen/hole content, and lattice parameters at and across grain boundaries for various Σ and near-Σ boundaries in bulk YBa2Cu3O7-δ. The geometry of those arbitrary grain boundaries was modeled using the constrained Coincidence Site Lattice (cCSL) theory, which requires c2/a2 being rational for coincidence boundaries in non-cubic crystals.In this presentation, we report our quantitative and simultaneous measurements of lattice parameters, and of oxygen/hole content at the boundary regions. The oxygen/hole density was quantified by guassian fitting to the observed oxygen K-edge spectra and comparing them with those from the same batch which had undergone oxygen reduction process (Fig.1).
Coupled thermal diffuse-atomic inner shell scattering in electron diffraction
Authors: Wang Z. L. 
Published: June 2020

In electron diffraction patterns, diffuse scattering at high angles is primarily generated by phonon, or thermal diffuse, scattering (TDS). Techniques were introduced to acquire the electron energy-loss spectra (EELS) of high-angle thermal-diffuse-scattered electrons (TDS-EELS) in a transmission electron microscope (TEM). With regards to the scattering mechanism, the TDS-EELS core ionization edge intensity was believed to be generated primarily by TDS - single electron, double-inelastic electron scattering processes. It was concluded from experimental data that the signal from coupled phonon - atomic inner shell excitations is stronger than that from atomic inner shell excitation alone. A formal dynamical theory is presented in this paper to illustrate the theoretical basis of the experimental observations. The theory can be applied to calculate the diffraction patterns of inelastically double-scattered electrons and the signal intensity observed in TDS-EELS.TDS is actually a statistically averaged, quasi-elastic scattering of the electrons by the crystal lattice of different thermal vibration configurations.
Alchemi of Fe-doped B2-ordered NiAl alloys with different doping levels
Authors: Anderson I. M. , Duncan A. J. , Bentley J. 
Published: June 2020

Recently, a formulation of the ALCHEMI technique has been presented that yields exact expressions for bestfit parameters in terms of the ionization localization constants and site distributions of three elements distributed over two sublattices. The application of this formulation to a NiAl-based B2-ordered alloy doped with 10% Fe used a graphical plotting technique to show that the size of the standard error of the best-fit parameters (and therefore of the site distributions) correlates with the extent to which the plotted data define a unique plane. The definition of the plane depends both upon the scatter of the data (Poisson statistics) and the spread of data over the best-fit plane (the variety of channeling conditions sampled). In this paper, the graphical plotting technique is applied to Fe-doped NiAl B2-ordered alloys of composition Ni0.5-xFexAl0.5 with x ∊ {0.02, 0.10}.Thin foil specimens of each composition were examined in a Philips CM 12 operated at 120 kV and equipped with an EDAX 9900 ultra-thin window energy-dispersive X-ray spectrometer.