bluuebunny/crossref_metadata_2025 huggingface dataset:
“dual phase” thin films prepared by deposition of aluminum on liquid nucleant gallium layers
Authors: Moberly Warren J. , Schwarcz Daniel , Ohring Milton
Published: June 2020

Aluminum thin films have been universally employed as interconnections in integrated circuits for the last quarter of a century. However, during this time Al metallization has never been totally immune from assorted reliability problems. This present research involves preparation and characterization of “dual phase” thin films, comprised of Al (or a transition metal) vacuum evaporated onto a liquid Ga (or other low melting temperature metal) nucleant layer. Ga is well known for causing grain boundary embrittlement in structural Al alloys. However, the Ga may well enhance the mechanical properties in Al thin films used as interconnect metallization, where this “dual phase” microstructure will prevent the buildup of stress that has historically resulted in electromigration failures in semiconductor devices. In addition, the presence of a liquid nucleant layer results in thin films (up to 2 μm thick) having surface roughness of the order of the film thickness, which in turn would enhance the bondability of such films.
Growth of au on a ge (111) surface
Authors: Dunn D.N. , Xu P. , Marks L.D.
Published: June 2020

The growth of noble metals such as Au and Ag on Si and Ge is of considerable interest for modern semi-conductor device applications. Several groups have investigated the room temperature growth of Au films on Ge (111) substrates using RHEED, LEED, UPS, as well as other techniques. It is clear from these investigations that the growth of Au on Ge (111) proceeds by a mechanism contrary to what might be expected by comparison to the growth of Au on Si (111). In general most of these studies have looked in two regimes, the first being simple room temperature growth over a wide range of Au coverages from a few tenths of a monolayer up to 100 Å in thickness. The second regime is the behavior of these Au films as a function of annealing temperature. Using RHEED and LEED to study a wide range of Au coverages, Le Lay and coworkers have found that the growth mechanism of Au films proceeds by the appearance of two dimensional close packed domains which do not completely cover the surface.
Direct phase determination in electron crystallography: layer silicates
Authors: Dorset Douglas L.
Published: June 2020

Recently the direct 3D determination of an aluminosilicate structure was reported based on high-voltage, high resolution electron microscopy of thin slices representing several projections of the crystal. It was particularly interesting that the relatively light oxygen atom positions could be visualized along with those of heavier components (Al, Si, Fe) in the staurolite structure.

Although this direct visualization of a crystal structure in the electron microscope certainly is a tour de force, representing a significant advance in microscopic instrumentation and technique, the electron crystallography of silicate structures at atomic resolution is, in itself, not particularly a new field of investigation. For example, in his book, B. B. Zvyagin outlines how he was able to use texture electron diffraction intensity data from several layer silicates in order to determine their crystal structures via interpretation of the Patterson function or construction of reasonable layer models suggested by the atomic stoichiometry.

It is unfortunate that many of the early Russian electron diffraction structure analyses have been overlooked or even ignored by the crystallographic community.
Inclusion of the weak beam effects in the bloch-wave simulation of dynamical diffraction by using the bethe potential
Authors: Zuo J. M.
Published: June 2020

The Bloch wave method of high energy transmission electron diffraction involves diagonalization of an nxn matrix, where n is the number of beams included in the simulation. This method is used widely in quantitative electron diffraction as the simulation method because of its flexibility in treating electron diffraction of arbitrary incident beam directions, while the multislice method of simulation is mostly used for low index zone axes of large unit cell crystals. The number of beams included in the simulation is limited by the computing time and the memory size of the computer. The computing time of the Bloch wave method is proportional to the n2. Thus only a limited number of beams can be included in the simulation. The truncation of beams may introduce a systematic error, if the number of beams included fails to converge. This is illustrated by fig. 1, in which the thickness pendelösung for MgO crystal along [001] zone axis is calculated with different number of beams in ZOLZ only, with no absorption, no Debye-Waller factor, atomic scattering factors for neutral spherical Mg and O atoms, and a = 4.2112 Å.
Least-square refinement of structure parameters from CBED integrated intensities: application to determination of temperature factors in Y BA2CU3O7
Authors: Gjønnes Kjersti , Gjønnes Jon
Published: June 2020

Electron diffraction intensities can be obtained at large scattering angles (sinθ/λ ≥ 2.0), and thus structure information can be collected in regions of reciprocal space that are not accessable with other diffraction methods. LACBED intensities in this range can be utilized for determination of accurate temperature factors or for refinement of coordinates. Such high index reflections can usually be treated kinematically or as a pertubed two-beam case. Application to Y Ba2Cu3O7 shows that a least square refinememt based on integrated intensities can determine temperature factors or coordinates.

LACBED patterns taken in the (00l) systematic row show an easily recognisable pattern of narrow bands from reflections in the range 15 < l < 40 (figure 1). Integrated intensities obtained from measured intensity profiles after subtraction of inelastic background (figure 2) were used in the least square fit for determination of temperature factors and refinement of z-coordinates for the Ba- and Cu-atoms.
Cluster analysis for large data sets: applications to individual aerosol particles from the mid-pacific
Authors: Shattuck Thomas W. , Anderson James R. , Tindale Neil W. , Buseck Peter R.
Published: June 2020

Individual particle analysis involves the study of tens of thousands of particles using automated scanning electron microscopy and elemental analysis by energy-dispersive, x-ray emission spectroscopy (EDS). EDS produces large data sets that must be analyzed using multi-variate statistical techniques. A complete study uses cluster analysis, discriminant analysis, and factor or principal components analysis (PCA). The three techniques are used in the study of particles sampled during the FeLine cruise to the mid-Pacific ocean in the summer of 1990. The mid-Pacific aerosol provides information on long range particle transport, iron deposition, sea salt ageing, and halogen chemistry.

Aerosol particle data sets suffer from a number of difficulties for pattern recognition using cluster analysis. There is a great disparity in the number of observations per cluster and the range of the variables in each cluster. The variables are not normally distributed, they are subject to considerable experimental error, and many values are zero, because of finite detection limits. Many of the clusters show considerable overlap, because of natural variability, agglomeration, and chemical reactivity.
Accuracies associated with the automated electron probe analysis of particulate populations
Authors: Small John A. , Calderone Matthew A.
Published: June 2020

The analysis of large numbers of particles by automated scanning electron microscopy/ electron probe (ASEM) has been used in conjunction with multivariate analysis algorithms to classify atmospheric particles into different groups based on size, shape, and elemental composition. These groups or clusters and the number of particles belonging to each are often used to develop source apportionment for the sampled aerosol.

There are several limitations particularly with the compositional analysis aspects of the automated routines that may limit the information that can be obtained from the sample. One of the major limitations of ASEM analyses is associated with the relatively short counting times, typically between 10-30 s, used for the accumulation of x-ray spectra from the individual particles. In contrast, the counting times used for conventional electron probe analyses are on the order of 5 minutes.

We are conducting a series of experiments to study the effects of accelerating voltage, and electron dose (beam current, and counting time) on the accuracy, precision, and detection limits of ASEM analyses. The degradation of accuracy, precision and detection will have a pronounced effect on the separation of particles with similar but different elemental compositions into groups.
Near IR multichannel Raman spectroscopy with μm spatial resolution
Authors: Barbillat J. , Roussel B.
Published: June 2020

The techniques and capabilities of near infrared (NIR) multichannel microprobing are described in detail in this paper.

The advantages and drawbacks of various kinds of instruments used to measure Raman spectra excited in the NIR spectral range have been extensively studied and compared. We demonstrate that a dispersive spectrometer specially designed to match the recently improved NIR multichannel detectors (silicon-based CCD,Germanium and InGaAs photodiode arrays) may provide better results than a Fourier Transform Interferometer in two fields:

- spatial resolution close to the diffraction limit in a micro-Raman confocal configuration (1.5 to 2 μm) and

- extension of the Raman spectrum to the low-frequency region (Stokes and Anti-Stokes).

Moreover, to observe the excitation profiles of both resonance and fluorescence, a combined multichannel instrument covering the entire range from 0.4 to 1.5 μm enables the user to select the best conditions of measurement.

For the study of very small samples (close to the diffraction limit),it is optically impossible to fill in the wide entrance aperture of the interferometer with the image of the sample while covering correctly the optical elements inside the interferometer.
A high-throughput confocal Raman microprobe based on a single grating spectrograph and CCD detector
Authors: Adar Fran
Published: June 2020

The availability of sharp cut-on holographic notch filters has enabled the design of simplified, compact Raman instruments for many applications where the size, complexity, and/or cost of instrumentation has been a significant limiting factor. With such a filter, a confocal Raman microprobe has been constructed around a 0.5 m focal length monochromator and 1” CCD detector. This system provides all the microprobe capabilities of the larger systems, including full confocal aperturing with spatial resolution determined by diffraction limitations. Since the gratings are kinematically mounted and easily interchangeable, the choice of grating will determine the trade-off on the array between spectral coverage and spectral resolution for any excitation wavelength between 400 and 830 nm.

The practical usefulness of the system as a confocal Raman microprobe will be determined by the low frequency cut-off and the acquisition times. The low frequency cut-off will depend on the notch filter; at laser wavelengths shorter than 550nm the cut-off today is about 100-200 cm-1.
Raman mapping and imaging using microline focus spectromety (MiFS)
Authors: Gardiner Derek J. , Bowden Michael
Published: June 2020

Early attempts to obtain Raman images relied upon illuminating the whole field of view with laser light, wavelength selecting the scattered light and imaging it onto a vidicon type TV detector. This method had several limitations, principally with sensitivity and inability to deal with fluorescence interference. Improvements have been made to this general approach, by the use of interference filters to select the required portion of the Raman spectrum for specific images and the possibilities of using Hadamard transform spectroscopy to produce micro-Raman images have been explored. Alternatively, the advantages of the single point micro Raman instrument can be retained and the sample moved under the focussed beam, either manually or by computer control, and the resulting spectroscopic data processed to generate the required map, image or profile.

The development of cooled, slow scan, charge coupled device (ccd) detectors offers the possibility of using a line focus arrangement to reduce greatly the data collection times. Raman Microline Focus Spectroscopy (MiFS) utilises a line focussed Raman microscope coupled to a non-astigmatic spectrograph operating with a slow scanned ccd detector.
Spatially resolved Raman and photolumtnescence spectroscopy of advanced materials
Authors: Ager Joel W. , Rosenblatt Gerd M.
Published: June 2020

We have developed and previously described a technique to profile important physical and chemical properties of materials based upon simultaneous acquisition of optical spectra excited along a laser-illuminated line, coupled with extensive and rapid spectral analysis to extract the desired informatioa Changes in materials properties that change the position, width, or relative intensities of spectral features can be mapped rapidly with a spatial resolution approaching 5 μm. Recently, we have used a combination of profiling photoluminescence (PL) spectroscopy and Raman scattering (RS) to measure bandgap and compositional variations in GaxIn1-xP epilayers grown on GaAs by organometallic vapor phase epitaxy (OMVPE). The spectral resolution in these experiments was 1 meV for PL and 0.4 cm-1 for RS; the spatial resolution was 85 μm.

GaxIn1-xP has potential as a component of high-efficiency visible LED's and lasers (300 K bandgap of 2.26 eV at x = 0.74). It can be grown lattice matched to GaAs at x=0.51 (bandgap = 1.91 eV) by a variety of techniques. However, small variations in x cause misfit strain at the interface, making high-quality, low-defect material difficult to grow.
Forensic applications of IR infrared microscopic internal reflection spectroscopy
Authors: Bartick Edward G. , Reffner John A.
Published: June 2020

Since the introduction of commercial Fourier transform infrared (FTIR) microscopic systems in 1983, IR microscopy has developed as an important analytical tool in research, industry and forensic analysis. Because of the frequent encounter of small quantities of physical evidence found at crime scenes, spectroscopic IR microscopes have proven particularly valuable for forensic applications. Transmittance and reflectance measurements have proven very useful. Reflection-absorption, specular reflection, and diffuse reflection have all been applied. However, it has been only very recently that an internal reflection (IRS) objective has been commercially introduced.

The IRS method, also known as attenuated total reflection (ATR), has proven very useful for IR analysis of standard size samples. The method has been applied to adhesive tapes, plastic explosives, and general applications in the analysis of opaque materials found as evidence. The small quantities or uncontaminated areas of specimens frequently found requiring forensic analysis will often be directly applicable to microscopic IRS analysis.
Cristal-growth dynamics of n-doped gaAs
Authors: Huong Pham V. , Bouchet Stéphanie , Launay Jean-Claude
Published: June 2020

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.

The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).

The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.

With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.
Transmission optimization of a microprobe instrument using a magnetic mass spectrometer
Authors: Slodzian Georges , Daigne Bernard , Girard Francois
Published: June 2020

Secondary ion emission from a solid target bombarded with primary ions in the range of several keV energy is a well known phenomenon which has been extensively used for determining elemental and isotopic compositions of solid samples and characterizing surface layers. Taking advantage of the fact that secondary ion emission is a rather localized process and has relatively high ionization yields, it is possible to build analytical ion microscopes with resolutions better than l00nm and fairly good sensitivity. The ionization useful yield (inverse of the average number of target atoms which must be sputtered to produce a well identified ion) depends upon the ionization probability and the overall transmission of the instrument (ratio of the number of ions forming a line in the mass spectrometer to the number of ions produced when a given number of atoms have been sputtered). It should be emphasized that the useful yield controls the ultimate performances of the instrument and that transmission considerations are essential when the spectrometer must work at high mass resolutions to separate different ionic species having the same number of mass units.
Transition metal ion implants in IngaAs measured by secondary-ion mass spectrometry
Authors: Simons David S.
Published: June 2020

In0.53Ga0.47As (hereafter InGaAs), lattice-matched to an InP substrate, is a potentially important material for optoelectronics and microwave devices. It is important for some of these applications to create semi-insulating (SI) layers in the material. Some possible uses would be in photodetectors, heterojunction lasers, and device isolation regions in monolithic integrated circuits. InGaAs is usually n-type as grown due to residual impurities such as Si and S. One way to achieve SI layers is to dope InGaAs with transition metal ions that are known to introduce deep acceptor levels in GaAs and InP. Fe has been added to InGaAs during growth for this purpose, but the Fe concentration and the resistivity of the material are difficult to control. An attractive alternative method for introduction of transition metals is ion implantation. This process offers good control over the dopant concentration and depth distribution. However, it does require a subsequent annealing step to heal the implantation-induced lattice damage.
Non-resonant multi- and single-photon ionization for the chemical characterization of surfaces
Authors: Welkie David G.
Published: June 2020

The chemical analysis of surfaces, where the ‘surface’ of a sample refers to the top few monolayers, is most commonly performed using the techniques of Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), and/or electron spectroscopy for chemical analysis (ESCA). For inorganic materials, AES is especially advantageous for quantitative elemental surface analysis at high spatial resolution. At lower spatial resolutions, SIMS generally provides the highest sensitivity, although quantitative interpretation of the results is often difficult or impossible. The primary reason for such difficulties is that the SIMS signal often depends more strongly on the nature of the local chemical environment at the analysis site than on the concentration of the species that is generating the signal. This is commonly referred to as the SIMS ‘matrix effect’.

For organic materials, both ESCA and SIMS are used to obtain information on the chemical structure at surfaces. While ESCA can provide unique information on the nature of the chemical bonds between species at a surface, SIMS can provide complementary information on the molecular structures that are present.
Laser microprobe mass spectrometry: A trend analysis
Authors: Kaufmann Raimund , Spengler Bernhard
Published: June 2020

Within the search for ultimate frontieres in microprobe analysis, sensitivity, selectivity and spatial resolution are amongst the primary criteria to be assessed. During recent years laser microprobe and ion microprobe analysis have been the most promising and competing approaches which not only share a lot of features in common but, by their physical principles are both rather open to further general improvements and dedicated instrumentations.

The term desorption for either laser- or particle-induced ion formation has become common use. Both principles are actually intensively explored especially with respect to produce organic ions by “soft” ionization. Some of the key aspects of such ion formation will be addressed with special emphasis on laser desorption.

Both principles are equally well suited for spot probing and/or analytical imaging with spatial resolution in the sub 1 μm range. However, while SIMS ion probe techniques have meanwhile achieved some impressive improvements with respect to practical capabilities by introducing e.g. pulsed high brightness ion sources in combination with TOF-MS the state of the art in the available laser microprobe instruments has virtually remained the same since the first introduction of the LAMMA and LIMA instruments more than a decade ago.
Applications and techniques of thickness measurement for sections and thin films
Authors: Heng Yew M. , Simon Gerard T. , Ottensmeyer F. Peter
Published: June 2020

The thickness of a specimen to be examined in the electron microscope is a significant parameter for many applications. However, due to the lack of ideal methodology for absolute thickness measurement, most quantitative analyses are performed using approaches which are more convenient. For example, theoretical factors, indirect relative thickness or ratio methods are used to eliminate the necessity to obtain the absolute thickness. These alternatives are theoretically valid. However, experimental verification using standards with known thicknesses are still imperative. Since absolute thickness remains indispensable, continuous development and improvement of techniques for thickness measurement are still much needed. The purpose of this study is to critically survey the importance of absolute thickness measurement and assess the available methods for thickness determination.

Knowledge of specimen thickness can be applied for both qualitative and quantitative purposes. Specimen thickness can be used to study imaging properties in different electron microscopy modes. Monitoring of film thickness is, for example, essential when coating specimens for high resolution secondary electron imaging, preparing multilayer specimens in material sciences or preparing ultrathin support films.
Microprobe analysis of technetium-mibi accumulation in cultured heart cell mitochondria: Correlation of structure and membrane potential
Authors: Backus Mark , Hockett Daniel , Piwnica-Worms David , Lieberman Melvyn , Ingram Peter , LeFurgey Ann
Published: June 2020

Hexakis (methoxyisobutylisonitrile)99mTechnetium (Tc-MTBI) is a gamma emitting radiopharmaceutical currently in clinical use for evaluating myocardial perfusion. Because Tc-MIBI exists as a lipophilic cation with a single positive charge, it has been shown to concentrate in mitochondria in response to membrane potential in a Nernstian fashion similar to rhodamine 123. Use of electron probe x-ray microanalysis (EPXMA) for localization and quantitation of the element technetium in mitochondria and calculation of membrane potential allows correlation for the first time between mitochondrial structure and membrane potential in intact cells.

Heart cells from 11-day-old chick embryos were cultured into spherical aggregates 50 -100 μm in diameter after Ebihara et al. Aggregates were then incubated for 60 minutes in HEPES balanced buffer salt solution containing either 0, 36,72, or 144 μMTc99-MIBI as well as 20 mCi metastable Tc99m-MIBI. Some aggregates were prepared for conventional fixation and subsequent electron microscopic evaluation, while other aggregates were plunge frozen in liquid propane and cryosectioned for quantitative EPXMA.
Imaging transported and endogenous calcium independently at a subcellular resolution: ion microscopy imaging of calcium stable isotopes
Authors: Chandra Subhash
Published: June 2020

Ion microscopy, based on secondary ion mass spectrometry (SIMS), is a unique isotopic imaging technique. The use of stable isotopes as tracers and their SIMS localization at a subcellular resolution has introduced a significant new approach for molecular localization and ion transport studies. A molecule of interest may be tagged with stable2H,13C,15N, etc. and imaged with SIMS for its intracellular location. Stable isotopes of physiologically important elements such as calcium and magnesium provide excellent tracers for ion transport imaging studies with SIMS. in a recent study with44Ca, the brush border region in the small intestine was observed to be the main barrier for calcium transport from the intestinal lumen to the lamina propria region in chickens suffering from Rickets, a vitamin D-deficiency condition.

An example of the use of44Ca stable isotope for imaging calcium-calcium exchange between the intracellular and extracellular calcium with SIMS is shown in figure 1. 3T3 cells were grown on high purity germanium chips to about 80% confluency.
Quantitative compositional mapping of biological tissues using a microcomputer
Authors: Heyman Robert V. , Saubermann Albert J.
Published: June 2020

Biological samples pose problems for analysis with electron probe microanalysis (EPMA), since they have considerable differences in element composition depending on compartment and physiological state. Further problems exist because the compartment may be difficult to identify with certainty when cryo-preparation methods are used. It is therefore often necessary to collect many analysis points to provide a suitable sampling of a particular compartment from many specimens. Rejection of spectra because the values appear to be outliers may possibly introduce bias or risk rejection of significant data. Application of quantitative digital x-ray mapping overcomes many of these problems. Digital computers can be used to divide a sample region into many small units, collect x-ray counts at each "point," store these results, and reassemble this data into a compositional map at a later time. When enough analysis time is allowed for each point, and appropriate standards are used, the resulting data becomes quantitative.
Visualization and measurement of concentration and surface range images
Authors: Russ John C.
Published: June 2020

Images representing the variation in elemental concentration or some intensity signal proportional to it, are produced by instruments such as the electron and ion microscope. They are customarily presented as “dot” maps in which the density of dots represents the concentration, or if the counting statistics of the signal are adequate, as a continuous tone grey scale image. Range images in which the elevation of a surface is recorded as an array of values which can be displayed as a grey-scale image, are produced by several instruments, including the scanning tunneling microscope, atomic force microscope, interferometric light microscope, and the confocal scanning light microscope. Display of the resulting concentration or elevation data with false color to enhance the visibility of small differences, or with expansion or compression of the vertical scale, or subtraction of a reference surface such as a best-fit plane, are often included. Some instruments offer additional display modes such as line profiles, along with some numerical data, such as the mean, standard deviation and limits of the values.
Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe
Authors: Fialin Michel , Rémond Guy
Published: June 2020

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).

Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.
Calculation and measurement of electron ionization cross sections for L and M shells
Authors: Luo Suichu , Joy David C. , Dunlap John R. , Wang Xinlei
Published: June 2020

The ionization of atoms by electrons is a process of great importance in physics, because it is the primary mechanism for energy loss of electron in matter and for X-ray microanalysis. Powell has critically compared various theoretical, semi- or empirical formulations with experiments and it is clear that although calculations and measurements have been carried out previously for K and to a lesser extent for L shells, very little data, both experimental and theoretical, exist for M shells.

We have calculated K ,L (L1 and L23 ) and M( M1 ,M23 M45 )shell ionization cross section covering the entire periodic table and spanning the energy range from the critical ionization energy for a particular element up to 100 keV using Hartree-Slater central self- consistent field model. The calculation algorithm is essentially that described in Ref.3 but both exchange and correlation energy effects have been included in the computations to ensure that the computed cross-sections are valid at low overvoltage ratios, and relativistic corrections have also been included for accuracy at high incident energies.
A simple formula for total elastic Mott cross sections
Authors: Gauvin Raynald , Drouin Dominique
Published: June 2020

The Monte Carlo method is a very powerful method to describe the scattering of electrons in solids. In this computations, the scattering of electrons is often described by the total elastic Rutherford Cross-Sections, given by [1]:

where E is the energy of the electron (KeV),Z is the atomic number of the atom responsible for scattering and α is the screening parameter and it is usually given by [2]:

Since equation (1) has been obtained using the Born approximation, it is well known that this formula gives innacurate values when the atomic number of the solid is high and/or the energy of the electron is low [3]. In such cases, total elastic cross-sections computed using the Mott's theory are more accurate. Recently, these total elastic cross-sections have been computed [4] using a complex numerical procedure and values for 96 elements for 26 energies ranging from 20 eV to 30 KeV are available.
Applications of a direct simulation of electron scattering to quantitative electron-probe microanalysis
Authors: Kotera Masatoshi , Yamamoto Keiji , Suga Hiroshi
Published: June 2020

A direct simulation of electron scatterings in solids is developed. The simulation takes into account elastic processes, and inelastic processes including inner-shell electron ionization, conduction electron ionization, bulk plasmon excitation, and bulk plasmon decay. After the ionization and the plasmon decay processes, the trajectories of hot electrons which are liberated from atomic electrons are calculated, and cascade multiplication of hot electrons is simulated in the solid. The theoretical equations used in the present simulation are in the following. For the elastic scattering of electrons by an atomic potential, we use the Mott cross section, which is obtained by the partial wave expansion method of the solution of the Dirac wave equation. For the inner-shell electron ionization, we use the cross section obtained from the generalized oscillator strength for each sub-shell in an atom. Under a condition of the Born approximation, cross section of an inner-shell electron excitation to the various continuum angular momentum channels for ionization is calculated using the generalized oscillator strength.
A simple Monte Carlo model for electron-probe quantitation
Authors: Duncumb Peter
Published: June 2020

Since the early work of Bishop in the 1960's, many have used Monte Carlo techniques for studying the role of electron scattering in the X-ray production process, but the simulation of individual trajectories has always proved too slow to be of use for online analysis. The paper describes a simple model for calculating the distribution curves of ionisation with depth ϕ(ρz) for a variety of target conditions, which are then characterised by a type of exponential expression capable of much faster computation. This expression is built into a practical correction procedure which can be applied to the analysis of all elements from boron upwards.

The Monte Carlo model uses a simple multiple scattering cross-section with 50-step trajectories. This cross-section is adjusted to give the correct variation of backscatter coefficient with target atomic number, as shown in Figure 1, and this is the only physical parameter which it is necessary to fit empirically.
Analysis of size-segregated samples from vehicular exhaust using laser microprobe mass spectrometry
Authors: Hoeft Stephen , Fletcher Robert
Published: June 2020

Because of their potential adverse health effects, polycyclic aromatic hydrocarbons (PAHs) are significant environmental pollutants. Many studies have demonstrated the presence of PAHs in vehicular exhaust by using chromatographic analysis techniques on filter samples. Most of these studies do not correlate the aerosol size distribution with that of the composition and occurrence of the PAHs, other than collecting the aerosol into a 'coarse' and a 'fine' (< 2.5 μm diameter) fraction and then determining the PAH content for each fraction. The goal of this study is to characterize the 'fine' fraction aerosol by further segregating it into six size fractions and then using laser microprobe mass spectrometry (LMMS) to analyze each fraction.

Samples were collected from the exhaust rooms of traffic tunnels at the Fort McHenry Tunnel in Baltimore, Maryland. This highway tunnel complex separates heavy diesels (trucks) from automobiles. Since each traffic tunnel is independently ventilated, it is possible to collect samples of emissions from either type of vehicular traffic.
Use of a thermal gradient and eds mapping to follow the fine details of formation in Tl-"1223" superconductors.
Authors: Morgan Peter E. D. , Doi Toshiya , Yuasa Toyotaka , Housley Robert M. , Porter John R.
Published: June 2020

The microstructural requirements of a superconducting wire, with a core of high temperature superconductor ceramic (HTSC), are long and platy grains, with good percolation from grain to grain to allow a high critical current. This microstructure is encouraged by growth from a liquid phase.

In earlier work in both Tl- and Bi-HTSC, we found that a liquid phase was also necessary to crystallize the three-Cu-layer 2223-types by solution-reprecipitation; without liquid none formed. It was of interest to see if the same type of situation applies to the Tl- 1223 case, which is attracting increasing attention due to its superior flux-pinning properties. The immediately available sample was a gold encapsulated wire with a core of (Pb0.5Tl0.5)(Sr1.6Ba0.4)Ca2Cu3Ox, made by a published technique, and which had been prefired to 800°C. The sample was subsequently fired in a constant temperature gradient furnace (2°C/cm) for 100h. Samples were mounted, sectioned, polished and gold coated for characterization by BSE imaging and EDS elemental mapping.
SAM/EDX analysis of Cu(Nb) alloys
Authors: Bevolo Albert J.
Published: June 2020

For several years our laboratory has investigated the properties of copper based alloys with transition metals such as Cu80Nb20. When heavily drawn these alloys retain the thermal conductivity of pure copper but acquire strengths usually associated with steels. Niobium dendrites, that are immiscible in the copper matrix in the as-cast form, become very fine, thermally stable filaments when heavily drawn. When heat treated in a diffusion pumped static vacuum chamber the surface unexpectedly acquires a silvery coloration rather than the reddish color expected from the dominant copper constituent. If a flow of inert gas is maintained then the surface becomes reddish. Experiments involving SAM and EDX analyses of cast alloys ex situ and in situ treated in ultra high vacuum (UHV) were performed to investigate this behavior.

Auger depth profiles of the ex situ silver colored alloys showed from the Nb (167) Auger transition lineshape that the dominant phase was metallic NbO.
Particle preparation for materials analysis (tutorial)
Authors: Zeissler Cynthia J.
Published: June 2020

Often, good results in materials analysis depend on good sample preparation. Although sample preparation can often be simple and straightforward, particles sometimes present special challenges. Sometimes just a few tricks make the only difference between the success and failure of sample preparation and analysis. Without adequate insight and care in specimen preparation, there may be loss of sample, over-expended effort and loss of time, contamination (sample or instrument), adverse morphological changes, misrepresentation of elemental composition or phase distribution, and other artifacts. This tutorial will cover a variety of topics dealing with sample preparation methods, the tools, equipment and supplies used, and artifacts primarily of concern to analytical electron beam techniques.

The many combinations of numerous parameters that can affect sample treatment and analysis make it difficult to produce a simple flow-chart for sample preparation. Various factors that determine optimal preparation methods include the physical state of the received sample (e.g., bulk, powder or single particle, wet or dry, homogeneous or heterogeneous), and the known chemical properties of the received sample.
Role of Non-Radiative Transitions in X-RAY Analysis
Authors: Lábár János L.
Published: June 2020

Radiative and non-radiative transitions present alternative ways for the excited atom to reduce its energy when the initial state is an atom singly ionised in one of its inner electron shells. Since the fluorescence yield gives the probability that the empty state in the inner (sub)shell is filled in by a radiative process, it seems that the generated x-ray intensities are independent of the non-radiative rearrangements from the point on where the value of fluorescence yield is given for the (sub)shell in question. In that way the intensity of an x-ray line would solely be dependent on the ionisation probability of the given (sub)shell and on the rates of the radiative transitions (determining the relative intensities of the lines originating from the same subshell). That image involves that the non-radiative processes only influence the value of the fluorescence yield. For the simplest case i.e. for the K shell it is true.
Removal of Bragg-Compton Channel Coupling in Electron Compton Scattering
Authors: Jonas P. , Schattschneider P. , Pongratz P.
Published: June 2020

Electron Compton scattering is inelastic scattering of fast electrons at large angles off core or valence electrons. The energy of the scattered electron is increasingly lowered with scattering angle; the energy distribution can be shown to be an image of the electron momentum density distribution in the ground state.

The most dominant problem in ECOSS (Electron Compton Scattering from Solids), is the Bragg-Compton channel coupling. Bragg scattered electrons in the specimen act as new sources for Compton scattering. Since these Compton events correspond to various scattering angles a number of Compton profiles with different maximum and width are superimposed in a measurement.

The Method

We may write the total measured intensity M at a particular energy loss E as a linear combination of coupled Bragg-Compton events. In the case of a systematic row reflection with i excited beams it is always possible to choose n = 2 * (i - 1) angles such that the system of linear equations can be solved with respect to I.
Deconvolution of EELS Spectra Revisited
Authors: Su D.S. , Schattschneider P.
Published: June 2020

The exact analysis of EELS-data needs a removal of multiple scattering from the measured low energy spectrum. Several methods have been reported. However, only the Fourierlog deconvolution seems to be widely used, inspite of difficuties with correct phase retrieval. Alternatively, a matrix-deconvolution proposed by one of the authors can be applied. The following comparison of the distinct approaches shows for the first time the limitation of the methods. Surprisingly, we find that the Fourier-log method is restricted to D ≤ π/2 (D is given in units of the mean free path) even if the proposed phase correction is applied. But also the method given by Spence, theoretically applicable for any D, fails for D ≥ 3 in our simulation. These failures may have been overlooked because EELS experimenters avoid specimens with D ≥ π/2, in general.

We obtained the single loss distribution S from a measured Al plasmon spectrum of a thin film (d = 50nm) using the Fourier-log algorithm.
Some Quantification Problems in Parallel EELS Images
Authors: Botton G. , L’Espérance G. , Ball M.D. , Gallerneault C.E.
Published: June 2020

The recently developed parallel electron energy loss spectrometers (PEELS) have led to a significant reduction in spectrum acquisition time making EELS more useful in many applications in material science. Dwell times as short as 50 msec per spectrum with a PEELS coupled to a scanning transmission electron microscope (STEM), can make quantitative EEL images accessible. These images would present distribution of elements with the high spatial resolution inherent to EELS. The aim of this paper is to briefly investigate the effect of acquisition time per pixel on the signal to noise ratio (SNR), the effect of thickness variation and crystallography and finally the energy stability of spectra when acquired in the scanning mode during long periods of time.

The configuration of the imaging system is the following: a Gatan PEELS is coupled to a CM30 (TEM/STEM) electron microscope, the control of the spectrometer and microscope is performed through a LINK AN10-85S MCA which is interfaced to a IBM RT 125 (running under AIX) via a DR11W line.
STEM Study of Surface Plasmon Excitation in Small Spherical Particles
Authors: UGARTE Daniel
Published: June 2020

Small particles exhibit chemical and physical behaviors substantially different from bulk materials. This is due to the fact that boundary conditions can induce specific constraints on the observed properties. As an example, energy loss experiments carried out in an analytical electron microscope, constitute a powerful technique to investigate the excitation of collective surface modes (plasmons), which are modified in a limited size medium. In this work a STEM VG HB501 has been used to study the low energy loss spectrum (1-40 eV) of silicon spherical particles [1], and the spatial localization of the different modes has been analyzed through digitally acquired energy filtered images. This material and its oxides have been extensively studied and are very well characterized, because of their applications in microelectronics. These particles are thus ideal objects to test the validity of theories developed up to now.

Typical EELS spectra in the low loss region are shown in fig. 2 and energy filtered images for the main spectral features in fig. 3.
EXELFS Studies of Carbon Fibers
Authors: Serin V. , Hssein K. , Zanchi G. , Sévely J.
Published: June 2020

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.
High Purity Germanium Detectors for EDS
Authors: McCarthy J. J. , Ales M. W. , McMillan D. J.
Published: June 2020

High purity germanium (HPGe) detectors offer multiple advantages for x-ray microanalysis in electron microscopes. These advantages include improved detection efficiency at energies above 20 keV, lower noise and higher energy resolution than can be obtained with a lithium drifted silicon detector. In the past, the use of HPGe detectors for EDS at energies below about 2 keV was impossible due to severe distortions of peak shapes and shifts in peak positions. These effects are the result of incomplete charge collection and are most pronounced at energies just above the energy of the germanium L absorption edges (1.2 to 1.4 keV). Using new processing techniques, we have manufactured 30 mm2 HPGe detectors that do not exhibit significant spectral distortion due to incomplete charge collection. Figure 1 presents a comparison of the peak shapes obtained from an HPGe detector produced by a previous method and a new detector produced with our current process. These detectors have been used for EDS applications in (S)TEM and SEM.
Design of a Field-Emission Gun for the Phillips CM20/STEM microscope
Authors: Mul P.M. , Bormans B.J.M. , Schaap L.
Published: June 2020

The first Field Emission Guns (FEG) on TEM/STEM instruments were introduced by Philips in 1977. In the past decade these EM400-series microscopes have been very successful, especially in analytical electron microscopy, where the high currents in small probes are particularly suitable. In High Resolution Electron Holography, the high coherence of the FEG has made it possible to approach atomic resolution.

Most of these TEM/STEM systems are based on a cold field emitter (CFE). There are, however, a number of disadvantages to CFE’s, because of their very small emission region: the maximum current is limited (a strong disadvantage for high-resolution TEM imaging) and the emission is unstable, requiring special measures to reduce the strong FEG-induced noise. Thermal field emitters (TFE), i.e. a zirconiated field emitter source operating in the thermal or Schottky mode, have been shown to be a viable and attractive alternative to CFE’s. TFE’s have larger emission regions, providing much higher maximum currents, better stability, and reduced sensitivity to vacuum conditions as well as mechanical and electrical interferences.