bluuebunny/crossref_metadata_2025 huggingface dataset:
An atom probe field ion microscope analysis of grain boundary chemistry in boron and carbon doped NiAl
Authors: Jayaram Raman , Miller M.K
Published: June 2020

The low temperature brittleness of nickel aluminides has been a serious impediment to their technological applications. A commonly employed technique to ductilize these materials involves the addition of suitable microalloying elements and correlating grain boundary chemistry with fracture mode. In the well documented case of Ni3Al, boron segregation to grain boundaries is accompanied by suppression of intergranular fracture and a significant increase in ductility. The high resolution microanalytical technique of atom probe field ion microscopy (APFIM) has been used in this study to analyze grain boundaries in order to characterize similar attempts to ductilize NiAl. APFIM specimens were prepared from tensile specimens of stoichiometric NiAl doped with either 0.04 or 0.12 at. % boron or 0.1 at % carbon, respectively. A field ion image of a grain boundary in a B-doped NiAl specimen is shown in Fig. 1. The brightly-imaging spots decorating the boundary were determined by atom probe analysis to be boron atoms. The boron enrichment factor at the boundary depends on the assumed thickness of the segregation as shown in Fig. 2 with an enrichment factor of ∼850 times for a monolayer coverage (i.e. 0.2 nm).
Atomic AEM - poissonian problems from gaussian probes!
Authors: Cliff Graham , Kenway Peter B.
Published: June 2020

In a previous paper, the authors have described the engineering requirements needed to detect one atom in the analytical electron microscope (AEM) by using x-ray microanalyis. Whilst the requirements to achieve this goal cannot be specified at present for a particular instrument, the specification for machines being developed by Vacuum Generators have a calculated minimum detection limit (MDL) of fewer than 4 atoms. At these detection limits the usual Gaussian statistics which have applied in AEM give way to Poissonian statistics. This paper will look at some of the interesting consequences of AEM at the atomic level.

The energy dispersive x-ray spectrometers (EDS) used in AEM have percentage detection limits usually quoted as about 0.1 wt. %. For this to equal 1 atom as the MDL, the analysed volume, defined by the probe diameter and the specimen thickness, must contain about 1000 atoms. For a field emission gun (FEG) on an AEM, sufficient current (1nA) can be obtained in a small enough probe (1nm FWHM) to allow analysis from a volume containing 1000 atoms (assuming adequate x-ray detection sensitivity) if the sample is about 20 atoms thick.
Core-Shell Excitation EELS of High-Angle Phonon-Scattered Electrons
Authors: Wang Z. L. , Fisher A. T.
Published: June 2020

A new technique, thermal-diffuse-scattered electron energy-loss spectroscopy (TDS-EELS), has been demonstrated to be useful for measurement of atomic mean vibration amplitude aA. This technique is performed in the dark-field image mode with a large-angle, annular objective aperture in a conventional transmission electron microscope (TEM) (Figs. 1 and 2). TDS-EELS is based on high-angle phonon - atomic inner-shell double inelastic (rather than high-angle atomic inner-shell single inelastic) scattering processes, and has shown significant temperature dependence (Fig. 3), which may arise from the variation of aA with temperature.

Signals in TDS-EELS could be generated by the following scattering mechanisms. One is the “coherent” double-inelastic scattering process, in which TDS and core-shell excitations occur “simultaneously” during scattering by the same atom. The other is “incoherent” double-inelastic scattering, in which TDS and core-shell excitations occur separately during scattering by different atoms. If the incoherent double scattering is the dominant process in TDS-EELS and if the collection angular range of the annular objective aperture is large (>30 mrad), the ratio of the integrated ionization edge intensities would be expected to be independent of temperature and similar to the intensity ratio of the corresponding ionization edges acquired in bright-field (BF-EELS) mode, where I(A)/I(B) ≈ nA/nB·σ(A)/σ(B), σ is the integrated ionization cross-section and n is the atomic concentration.
Predicting resolution in backscattered electron SEM images from monte carlo calculations of the interaction volume
Authors: Newbury Dale E.
Published: June 2020

Calculations of spatial resolution in scanning electron microscopy are typically based on estimates of the beam size from considerations of the electron optics. The gaussian beam diameter, dg, which is determined from the brightness equation, the contributions of the aberrations (spherical, dS and chromatic, dC), and aperture diffraction (dD) are added in quadrature to give the diameter of the focused probe, dp:

(1)

This formula can predict the size of the unscattered probe outside of the specimen but to predict image resolution, it is necessary to include a description of the beam interaction with the target. Monte Carlo electron trajectory simulation provides a good description of the complex, multiple scattering situation that exists and the distribution of signals emitted, but the simulation is too slow to be used for on-line calculations, except for a few laboratories with direct access to a parallel-processing computer environment. Monte Carlo studies show that the distribution of emitted signals is dominated by the scattering processes and not by the beam size, at least for high resolution conditions.
Gas-flow field in the environmental SEM
Authors: Danilatos G. D.
Published: June 2020

The study of the gas flow in the environmental SEM (ESEM) is important both for the instrument design and for determining the environmental conditions around the specimen. Some results from such a study were published previously and the present report is a continuation from the same work. The Monte Carlo simulation method for the gas flow was used. Of particular importance is the question on the flow field contours as the specimen approaches the pressure limiting aperture (PLA) and the question on the mass density of the supersonic jet formed above the plane of the PLA and on the mass density immediately below the aperture.

A conically shaped PLA is preferred for several reasons; one such reason is that it allows the preservation of a stagnation pressure environment over the specimen surface for a short distance down to one PLA diameter (D): In Fig. 1 the specimen is placed 1.2 mm (i.e. 3 PLA diameters) below the aperture, and from the number density contours no effect is observed over the specimen surface.
Environmental Scanning Electron Microscope Applications in Agricultural Chemistry Research
Authors: Campbell S. M. , Kohls C. L.
Published: June 2020

The environmental scanning electron microscope (ESEM) can be used to examine hydrated biological samples and observe dynamic processes in the SEM chamber. We have used the ESEM to explore solvent/sample interactions in a number of agricultural products. Two examples are given below.

Unidentified crystals were observed by SEM on the surface of a pelletized pesticide. The identity of these crystals was sought. EDS revealed the presence of copper, sulfur and phosphorus, but did not allow positive identification. The ESEM was used to identify a solvent that could extract the crystals for identification by other analytical techniques. Figure 1 shows the uncoated pellet surface at low magnification. Figure 2 shows the surface of a pellet after a drop of methylene chloride was applied to the sample and pumped away with the ESEM vacuum. Figures 3 and 4 are the same surface of a single pellet before and after chloroform was used to briefly extract the surface. Of several solvents investigated in this way, chloroform appeared to extract the crystals with the least disruption of the pellet's surface.
Principles of Low-Vacuum SEM
Authors: Peters Klaus-Ruediger
Published: June 2020

Only recently it became possible to expand scanning electron microscopy to low vacuum and atmospheric pressure through the introduction of several new technologies. In principle, only the specimen is provided with a controlled gaseous environment while the optical microscope column is kept at high vacuum. In the specimen chamber, the gas can generate new interactions with i) the probe electrons, ii) the specimen surface, and iii) the specimen-specific signal electrons. The results of these interactions yield new information about specimen surfaces not accessible to conventional high vacuum SEM. Several microscope types are available differing from each other by the maximum available gas pressure and the types of signals which can be used for investigation of specimen properties.

Electrical non-conductors can be easily imaged despite charge accumulations at and beneath their surface. At high gas pressures between 10-2 and 2 torr, gas molecules are ionized in the electrical field between the specimen surface and the surrounding microscope parts through signal electrons and, to a certain extent, probe electrons. The gas provides a stable ion flux for a surface charge equalization if sufficient gas ions are provided.
Slow-Scan CCD Observation of Backscattering Patterns in SEM
Authors: Ouyang F. , Ray D. A. , Krivanek O. L.
Published: June 2020

Electron backscattering Kikuchi diffraction patterns (BKDP) reveal useful information about the structure and orientation of crystals under study. With the well focused electron beam in a scanning electron microscope (SEM), one can use BKDP as a microanalysis tool. BKDPs have been recorded in SEMs using a phosphor screen coupled to an intensified TV camera through a lens system, and by photographic negatives. With the development of fiber-optically coupled slow scan CCD (SSC) cameras for electron beam imaging, one can take advantage of their high sensitivity and wide dynamic range for observing BKDP in SEM.

We have used the Gatan 690 SSC camera to observe backscattering patterns in a JEOL JSM-840A SEM. The CCD sensor has an active area of 13.25 mm × 8.83 mm and 576 × 384 pixels. The camera head, which consists of a single crystal YAG scintillator fiber optically coupled to the CCD chip, is located inside the SEM specimen chamber. The whole camera head is cooled to about -30°C by a Peltier cooler, which permits long integration times (up to 100 seconds).
Analysis of SEM Electron Backscattered Kikuchi Patterns Using a CCD Detector and a Macintosh Computer
Authors: Goehner Raymond P. , Michael Joseph R. , Hills Charles R. , Carr Martin J.
Published: June 2020

The existence of electron backscattered (Kikuchi) patterns (EBSP) in the scanning electron microscope (SEM) is well known. The principal application of EBSP has been to determine the crystallographic orientation of bulk samples from materials with cubic symmetry. More recently the technique has being used to study crystallographic distortions and make space group determinations. An unexploited application of EBSP is that of phase identification, for example in metallographically prepared cross sections of solders and brazes.

We have adapted EBSP to the general problem of crystallographic analysis of materials in an SEM though the development of high quality imaging hardware and interactive analysis software. Though visually complex, EBSP patterns exhibit interplanar spacing data comparable to Selected Area Diffraction (SAD) in TEM. After correcting for projection distortion, the angular information in a typical EBSP pattern is also comparable in precision to SAD (∼±1°), but, significantly, includes a much larger solid angle (∼60°) of reciprocal space which typically includes several crystallographic zones simultaneously.
The calculation of backscattered images for cross-section samples in the scanning electron microscope (SEM)
Authors: Ly T.D. , Howitt D.G
Published: June 2020

The calculation of image contrast in heterogeneous samples can be done using Monte Carlo techniques if the electron trajectories can be calculated through the composition profiles in the specimen. Most of the programs that are available are designed to calculate signal intensities from samples of uniform atomic number and density (e.g Joy 1988, Reimer and Steltzer 1987) but some success has been achieved in the description of samples with distinct composition profiles by extrapolating these results.

The image simulations we have done here are based upon Monte Carlo calculations of the electron backscattered signal from samples where the composition variations can be taken into account in determining both the elastic and inelastic scattering cross sections. This work involved extending the program developed by Joy (1988) and comparing the calculated signal intensities to the values derived experimentally from a specimen of well defined geometry. In the program the elastic scattering cross-sections, which describe the collisions of the electrons with the atomic nucleus are described by a Rutherford model given by

(1)
A miniature MCP detector for low voltage SEM imaging
Authors: Hooper John , Ellis Glenn , Easterbrook David
Published: June 2020

MicroChannel plate (MCP) based detectors are becoming widely accepted in SEM imaging applications requiring low beam energies and currents. Images have been obtained of uncoated samples without the usual charging effects and of semiconductor materials with little or no damage to sensitive surfaces. Useful images have been obtained with beam energies as low as 200 v and currents as low as 2 pa.

The major limitations of the current generation of MCP detectors for SEM are their size (diameter) and thickness. The diameter of the typical MCP detector exceeds that of the polepiece tip of most SEM instruments, lowering the maximum angle at which samples may be tilted. Many semiconductor inspection procedures require high tilt angles. The thickness of the detector module limits the sample working distance and, therefore, the resolution of the SEM instrument. The major contributor to detector module thickness is the space required by the metal casing which houses the MCP itself.
High-resolution scanning electron microscopy of thin-film magnetic media of magnetic recording disk
Authors: Ogura K. , Nishioka H. , Ikeo N. , Kanazawa T. , Teshima J.
Published: June 2020

Structural appraisal of thin film magnetic media is very important because their magnetic characters such as magnetic hysteresis and recording behaviors are drastically altered by the grain structure of the film. However, in general, the surface of thin film magnetic media of magnetic recording disk which is process completed is protected by several-nm thick sputtered carbon. Therefore, high-resolution observation of a cross-sectional plane of a disk is strongly required to see the fine structure of the thin film magnetic media. Additionally, observation of the top protection film is also very important in this field.

Recently, several different process-completed magnetic disks were examined with a UHR-SEM, the JEOL JSM 890, which consisted of a field emission gun and a high-performance immerse lens. The disks were cut into approximately 10-mm squares, the bottom of these pieces were carved into more than half of the total thickness of the disks, and they were bent. There were many cracks on the bent disks. When these disks were observed with the UHR-SEM, it was very difficult to observe the fine structure of thin film magnetic media which appeared on the cracks, because of a very heavy contamination on the observing area.
The microscopy of electromigration failures
Authors: Lloyd J. R. , Rose J. H.
Published: June 2020

Electromigration is the major wearout failure mechanism in the metal conductors of integrated circuits. As such, the study of electromigration is very important in the microelectronics industry, and has been the subject of intense study for over 25 years. The basic physics is fairly well understood, although the precise reasons and mechanisms responsible for the failure process are still the subject of some controversy. Several models have been constructed, all of which adequately predict the major experimental observations, but the underlying mechanisms are very different. The curious thing is that microscopy has not yet been able to provide the evidence necessary to differentiate between the major failure mechanisms.

Electromigration is the diffusion of metal atoms in a metal conductor under the influence of a high current density where the mass transport is biased in the direction of electron flow, for n type conductors, by the momentum exchange between conducting electrons and the diffusing metal atoms.
Effect of Thermal ramping rate on defect formation in oxygen-implanted silicon-on-insulator material
Authors: Park Ju-Chul , Krause Stephen , El-Ghor Mohammed
Published: June 2020

Integrated circuits on SIMOX (Separation by IMplantation of OXygen) have higher speed, radiation hardness, and higher temperature capability. Defects in the top Si layer inhibit bipolar applications and may affect CMOS(Complementary Metal-On-Semiconductor) device yield, operation and reliability. As-implanted SIMOX has many types of defects, including short stacking faults(SFs), multiply faulted defects(MFDs), and {113} defects. In annealed SIMOX, new defects form during the ramping cycle. The effect of thermal ramping rate on the development of new defects has received only limited study. In this work, the effects of rapid thermal annealing(RTA) and thermal ramp rate on defect density and structural change were studied.

Two set of samples were prepared with different oxygen doses. First, one set of (100) Si wafers was implanted with a high dose of 1.8×l018cm−2 at 200 KeV at 620°C. A rapid thermal anneal(RTA) wafer was obtained from a lamp anneal for 1 minute at 1320°C using a ramp rate of 50°C/sec. A portion of this sample was then conventionally annealed in a tube furnace for 5 hours at 1320°C. Another set of (100) Si wafers was implanted with a low dose of 3×l015cm−2 at 25°C. Different samples were then annealed at 1250°C for 30 sec using three ramp rates of 50°C/sec, l°C/sec and 0.1°C/sec. Cross-sections of the samples were studied with conventional transmission electron microscopy (CTEM) at 200 KeV.
A correlative study of microstructure and surface topography in Al-1.5%Cu films
Authors: Theodore N. David , Cao Bea , Carrejo Juan , Crozier Peter A.
Published: June 2020

Al(Cu) is currently being used for interconnects in semiconductor integrated-circuits. Problems that arise with use of the material are electromigration, stress-migration, and corrosion. Electromigration and stress-migration behaviors of the films are known to depend on grain-sizes and distributions in the material. Surface topography of the films could possibly affect stress-migration as well as use of the material in multi-level metallization schemes. The present study investigates the extent of correlation between microstructure and surface topography in Al-1.5%Cu films.

Substrates used for this study consisted of (100) silicon wafers with a 200 nm silicon-dioxide layer on top. Al(1.5%Cu) was sputtered onto the substrates; substrates were held at a temperature of 450°C during sputtering. Layer thicknesses were ∼740 nm. Scanning electron-microscopy was performed using a Cambridge 250-MK III SEM equipped with a heating stage. Plan-view TEM specimens were prepared in the 100 substrate-geometry. These were then analyzed using bright-field and dark-field TEM imaging techniques. A JEOL JEM 200CX transmission electron microscope was used for the investigation, operating at 200 kV.
The morphologies and electrical properties of indium contacts on (100) cadmium telluride surfaces
Authors: Letsoalo A.M. , Lee M.E. , de Neijs E.O.
Published: June 2020

Semiconductor devices require metal contacts for efficient collection of electrical charge. The physics of these metal/semiconductor contacts assumes perfect, abrupt and continuous interfaces between the layers. However, in practice these layers are neither continuous nor abrupt due to poor nucleation conditions and the formation of interfacial layers. The effects of layer thickness, deposition rate and substrate stoichiometry have been previously reported. In this work we will compare the effects of a single deposition technique and multiple depositions on the morphology of indium layers grown on (100) CdTe substrates. The electrical characteristics and specific resistivities of the indium contacts were measured, and their relationships with indium layer morphologies were established.

Semi-insulating (100) CdTe samples were cut from Bridgman grown single crystal ingots. The surface of the as-cut slices were mechanically polished using 5μm, 3μm, 1μm and 0,25μm diamond abrasive respectively. This was followed by two minutes immersion in a 5% bromine-methanol solution.
EELS detection limits
Authors: Hunt J. A. , Williams D. B.
Published: June 2020

Why determine detection limits?A natural question to ask about any quantitative technique, including EELS in the STEM, is “How little of  can be observed?” Detection limits serve as a guide to what problems are solvable and what are the best techniques to analyze specific systems, e.g., EELS vs. EDXS vs. SIMS, etc. The exercise of determining EELS detection limits provides a sobering reminder of sizable uncertainties of numerous EELS variables, e.g., cross-sections, analyzed volumes, interaction delocalization, etc. Minimizing detection limits require optimization of many issues of the field, such as beam size and energy spread, the spectrometer and detector, quantitation techniques and specimen preparation. Additionally, comparing obtainable detection limits with theoretical values allows assessment of the rate at which a major portion of the field of EELS is maturing. Such assessments provide useful clues to if and where further development work is justified.

Traditional detection limit calculations. Typically there have been two types of detection limits discussed in EELS, the minimum detectable mass (MDM) and the minimum mass fraction (MMF).
Analysis of microsamples with an FT-Raman microscope
Authors: Kawai N.T. , Sawatski J. , Lehner C.
Published: June 2020

Rapid developments in near-IR filter and detector technology have resulted in FT-Raman spectroscopy emerging as a powerful technique in both research and analytical laboratories. The more recent advances in FT-Raman instrumentation now emphasize the optimization of different sampling accessories, including microsampling techniques. Microscopes attached to conventional Raman spectrometers operating at visible wavelengths have already proven to be applicable to many problems of chemical analysis. However, the optimized combination of an optical microscope and a near-IR FT-Raman spectrometer currently enables the analysis of very small samples which would normally fluoresce with visible excitation. Such samples include polymer fibers and thin films, dyes on fabrics, and small biological samples.

In FT-Raman microscopy, the microscope is coupled to the near-IR FT-Raman spectrometer via fiber optic cables. These cables transfer the Nd:YAG laser beam from the spectrometer to the microscope, and channel the scattered light back again to be modulated by the interferometer and measured by the high sensitivity near-IR detector.
Quantitative mass analysis of cryosections in the field-emission STEM
Authors: Andrews S.B. , Buchanan R.A. , O'Connell M.F. , Leapman R.D.
Published: June 2020

Low-dose, dark-field imaging in the field-emission STEM is a well documented method for mass mapping isolated protein molecules and macromolecular assemblies. Now, technical advances can provide truly thin, minimally compressed cryosections of unfixed, direcdy frozen tissues. These sections are thin enough-and have enough ultrastructural detail-to make mass mapping useful for directly and quantitatively measuring the in situ mass of cell constituents without beam-induced mass loss or other damage. In this report, we illustrate how dark-field STEM of cryosections can be used to measure the mass of single organelles in Purkinje cell dendrites, which is of interest because certain of these organelles participate in ion and water flow following synaptic activity-induced calcium mobilization.

Cryosections, prepared in a Reichert FC-4E cryoultramicrotome at ca. -160 C, were cut to a nominal thickness of 100 nm on a 35° Diatome diamond knife with the aid of an antistatic device. Sections mounted on carbon/Formvar-coated grids were transferred (frozen-hydrated) into a modified VG HB501 field-emission STEM prior to freeze-drying at ca. -110 C.
Ionic changes in cultured heart cells following calcium depletion and repletion
Authors: Hockett Daniel , Freudenrich Craig C. , Mohr Jennifer R. , Lieberman Melvyn , Ingram Peter , LeFurgey Ann
Published: June 2020

Intact perfused hearts subjected to calcium depletion and subsequent repletion undergo irreversible structural damage characterized by sarcolemmal disruption, hypercontracture, and the appearance of large electron dense deposits (thought to be calcium phosphate) within mitochondria. This structural damage is accompanied by increased intracellular Na+ and Ca++. Cultured embryonic chick heart cells subjected to the same conditions do not exhibit ultrastructural damage but do undergo similar ionic changes. This study characterizes the intracellular ionic changes associated with calcium repletion and assesses the role of mitochondria in the buffering of calcium.

METHODS: Heart cells were obtained from 11-day-old chicken embryos and cultured as spherical aggregates for 3-4 days. The aggregates were then incubated at 37°C in HEPES buffered solution containing 1.3 mM Ca for 10 minutes (control period). Following this control period, the aggregates were incubated for 10 minutes in Ca-free HEPES buffer containing 1mM EGTA (depletion period). Finally, the aggregates were returned to normal, Ca-containing, HEPES buffer (repletion period).
Platinum as a tracer for intracellular distribution of a drug (CIS-PLATIN) : x-ray microanalysis
Authors: Gary Kirk R. , Lee Ping
Published: June 2020

Cisplatin, cis-diamminedichloroplatinum (II) , contains a platinum atom in each of its molecule. It is an effective chemotherapeutic agent, used to treat ovarian, testicular and bladder tumors. The antitumor activity and cytoxity of this drug is generally attributed to its ability to cross-link DNA in the chromosome. Recent investigators show that there are also membrane and cytosolic components in the biological activity of cisplatin. Although the mechanism for the membrane transport of cisplatin is not known, it is thought that decrease in uptake of the drug is contributory to the cellular resistance to cisplatin. In addition cytosolic concentrations of glutathione, metallothionein or protein kinase C have been shown to affect the cytotoxicity of cisplatin. A frequent toxicity seen in patients that have received cisplatin treatment is the depression of the bone marrow cells. In order to gain some insight into this toxicity event, we have studied the uptake and intracellular distribution of cisplatin using the technique of cryomicrotomy and x-ray microanalysis.
Magnesium and sulfur in mast cell and basophil granules of lower vertebrates in relation with histamine
Authors: Takaya Kenichi
Published: June 2020

Mast cell and basophil granules of the vertebrate contain heparin or related sulfated proteoglycans. Histamine is also present in mammalian mast cells and basophils. However, no histamine is detected in mast cell granules of the amphibian or fish, while it is shown in those of reptiles and birds A quantitative x-ray microanalysis of mast cell granules of fresh frozen dried ultrathin sections of the tongue of Wistar rats and tree frogs disclosed high concentrations of sulfur in rat mast cell granules and those of sulfur and magnesium in the tree frog granules. Their concentrations in tree frog mast cell granules were closely correlated (r=0.94).

Fresh frozen dried ultrathin sections and fresh air-dried prints of the tree frog tongue and spleen and young red-eared turtle (ca. 6 g) spleen and heart blood were examined by a quantitative energy-dispersive x-ray microanalysis (X-650, Kevex-7000) for the element constituents of the granules of mast cells and basophils. The specimens were observed by transmission electron microscopy (TEM) (80-200 kV) and followed by scanning transmission electron microscopy (STEM) under an analytical electron microscope (X-650) at an acceleration voltage of 40 kV and a specimen current of 0.2 nA. A spot analysis was performed in a STEM mode for 100 s at a specimen current of 2 nA on the mast cell and basophil granules and other areas of the cells. Histamine was examined by the o-phthalaldehyde method.
Visibility of two intermixed phases as a function of grain size and signal-to-noise: a computer simulation
Authors: Bright David S.
Published: June 2020

In electron microscope or microprobe images, noise obscures the visibility of objects. The noise level can be reduced at the cost of increasing the image collection time, beam current, detector efficiency, etc. How good does the signal to noise have to be in order for the operator to be able to visually detect two intermixed phases of material?

In our previous papers we related visibility of single, well separated objects to object size and shape and to the Rose parameter, k, which is related to object contrast. In this paper we determine the imaging conditions for being able to detect the presence of two phases versus a uniform phase.

In his paper in 1948 on the quality of television transmission of images, Rose defined a parameter, k, which we generalize and relate to the signal quality for objects in digital images. As illustrated in Fig. 1, k = "signal"/"noise", where "signal" indicates the excursion in pixel counts due to the object against the background and "noise" indicates the scatter in pixel counts for either the object or the background.
Improved sensitivity, accuracy and spatial resolution of light-element analysis in the SEM at low beam voltages
Authors: Boyes E D , Hartmann I R , Smith D L , Gooding F W , Hanna L , Sokola D
Published: June 2020

We have found that at low beam voltages, and especially at or below 5kV, the sensitivity, accuracy and spatial resolution for light element EDX analysis of bulk specimens in the SEM are all improved, compared to the conventional 30kV, by more than a factor of 10x. The reduced range (R) of the electron beam into a bulk sample is a strong function of beam voltage (R ∝ E05/3). This translates directly into much better spatial resolution of analysis which can be well into the sub-micron range and often <0. 1μm, compared with the 1-10<m typical of conventional EPMA analysis at 30kV. The greatly reduced electron penetration, and therefore much shorter x-ray escape range, substantially reduces, and in many cases entirely eliminates absorption (A) and fluorescence (F) effects on the (ZAF) x-ray signal. The situation is similar to that with a detached thin foil specimen prepared for STEM/AEM by physical separation, where the A and F effects are also generally very small and quantitation is also simplified.
Standardless quantitative x-ray analysis
Authors: pouchou Jean-Louis , Pichoir Françoise
Published: June 2020

The ϕ(ρz) models developed during the recent years (Gaussian, PAP, XPP) have been shown by several authors to improve significantly the capability of quantitative x-ray microanalysis, mainly in the field of light elements, tilted specimens, and layered specimens. An increasing number of users is now able to take advantage of these models, since some of them have been implemented in EPMA or EDS commercial softwares.

However, most of the reported successful applications are the result of analyses with standards, where the basic data are the relative x-ray intensities (also called k-ratios). Indeed, analyses with standards are well adapted to the electron microprobes, and permit to obtain very accurate results. But in the scanning electron microscopes (SEM), the operations of acquiring, processing and handling the EDS spectra of all the required standards are really time consuming. It is why an EDS standardless mode giving satisfactory quantitative results would be so useful, even for those laboratories which can also operate an electron microprobe for the applications requiring the highest degree of accuracy.
A new and versatile computer program for correcting EPMA data
Authors: Farthing I , Love G , Scott VD , Walker CT
Published: June 2020

A new computer program has been developed to convert electron probe microanalysis data into accurate measurements of chemical composition. It is menu-based and designed to operate off-line using any IBM PC compatible computer. As shown in the flowchart, fig. 1, the architecture is modular and the programming language adopted is a compilable version of BASIC which possesses much of the processing speed associated with FORTRAN or C. Specimens containing up to fifteen elements, with 4 ≤ Z ≤ 96, can be handled and all the major x-ray lines (Kα, Kβ, Lα, L(β, Mα and Mβ) are available for analysis purposes.

The procedure itself is based upon the classical ZAF approach in which corrections for atomic number (Z), x-ray absorption (A), characteristic fluorescence (Fl) and continuum fluorescence (F2) are treated independently. The factors dealing with fluorescence are essentially those of Reed (characteristic) and Springer (continuum) although both contain minor updates. However, the atomic number and absorption factors are the authors' own and the latter, developed from a quadrilateral representation of the x-ray distribution with depth in a solid, distinguishes this program from others.
The Use of Monte Carlo Simulations in Quantitative Electron-Probe Microanalysis
Authors: Karduck Peter , Ammann Norbert
Published: June 2020

The interaction of a focused beam of monochromatic electrons with a solid sample is a complex many-particle problem, which cannot be fully described by analytical methods. But already in the early sixties trajectories of single electrons were simulated numerically on computers (1,2,3). This method was called Monte Carlo simulation (MC). Sequential simulation of some thousand trajectories accumulates a set of data, sufficient to provide information about

-fraction of backscattered electrons,

-fraction of transmitted electrons in case of thin film samples,

-ionization probability for certain electron shells as a function of sample depth,

-calculation of x-ray intensities generated in or emitted from the sample,

-energy distribution of backscattered electrons or of electrons in certain depth,

-calculation of signal generation in samples with complex geometries.

For all these applications the physical processes of electron - solid interaction needed to be described as realistic and accurate as possible, which was always - and is still - in contradiction to the limitations of existing theories, their applicability in such a complex problem, and of course to the limitations of computer capacities.
Analytical electron microscopy of grain boundaries in Al-Cu metallizations
Authors: Michael J. R. , Romig A. D. , Frear D. R.
Published: June 2020

Al with additions of Cu is commonly used as the conductor metallizations for integrated circuits, the Cu being added since it improves resistance to electromigration failure. As linewidths decrease to submicrometer dimensions, the current density carried by the interconnect increases dramatically and the probability of electromigration failure increases. To increase the robustness of the interconnect lines to this failure mode, an understanding of the mechanism by which Cu improves resistance to electromigration is needed. A number of theories have been proposed to account for role of Cu on electromigration behavior and many of the theories are dependent of the elemental Cu distribution in the interconnect line. However, there is an incomplete understanding of the distribution of Cu within the Al interconnect as a function of thermal history. In order to understand the role of Cu in reducing electromigration failures better, it is important to characterize the Cu distribution within the microstructure of the Al-Cu metallization.
A quantitative analysis of inert gases in thin metal films with the use of simulated pure standards
Authors: Park J. S. , Liu D. R. , Hoffman D. W.
Published: June 2020

The quantitative analysis of inert gases in solid media presents a great challenge because no suitable calibration standards are available. Early analyses on inert gases in thin films were conducted qualitatively with an electron microprobe. A quantitative analysis with the use of surrogate standard was reported based on an assumption that the intensities of neighboring elements do not vary much or vary linearly. Another quantitative analysis of Ar was conducted with pure Ar intensities being obtained from linear extrapolation from the normalized net peak counting rate values of Si to Cl. Since various inert gases are commonly used in thin film sputtering processes, it is important to obtain accurate analyses on inert gases that are entrapped in films during the process. The present study is another attempt to employ simulated pure standards for the inert gases Ne, Ar, Kr and Xe by interpolation and extrapolation with a least square fit.
Quantitative digital x-ray imaging of the outer shell layer of mytilus edulis (Bivalvia)
Authors: Parker Donald L. , Rosenberg Gary D.
Published: June 2020

Compositional mapping using digital x-ray imaging has been applied to a variety of applications. The extension of these procedures permitting complete quantitation allows EPM application where detailed structures exist requiring higher resolution. We apply these techniques here for the first time to the study of the molluscan shell. The outer shell layer of the mussel, Mytilus edulis, consists of fibrous calcific prisms (1-3μm diameter) which are organized structurally as layers corresponding to growth increments (up to ca.100μm thick, deposited daily, normal to the direction of growth). Digital imaging is used here to precisely determine the composition of these layers with high spatial resolution.

Digital images were obtained with a Cameca® three spectrometer EPM system interfaced to a Kevex 8000® analyzer/imaging system. Images are stored as WDS intensity pixels, with final extraction of image data for complete quantitation being performed offline. The extracted intensities were corrected for dead time, background and transformed into K-ratios for full matrix correction using the CITZAF routines.

Shells were sectioned along selected growth axes and polished using alumina followed by ultrasonic cleaning. All specimens were coated with ∼50nm of aluminum (as opposed to carbon) to retard degradation of the carbonate during analysis.
Electron-Microbeam investigation of late quaternary sand sediments from the lagoon of venice (Italy)
Authors: Bonardi Maurizio
Published: June 2020

Electron probe microanalysis (EPMA) has been used to investigate the mineral assemblage of sand samples from the Venice Lagoon Quaternary sediments. These sediments consist mainly of sand, silt and clay layers with some peat lenses. The boundary between the Holocene and Late-Pleistocene is marked by an overconsolidated layer of clay, related to the origin of the Venetian Lagoon. Because in some area of the basin this clay layer has been eroded away it is not always possible to accurately define the limit between the Holocene and Pleistocene sedimentations.

Seventeen continuous cores collected for geotechnical purposes along the offshore sandy bar that separates the Lagoon of Venice from the open Adriatic Sea, were available for this investigation. The cores 25 to 30 m long included the Holocene and Late-Pleistocene sediments. For this preliminary study about 130 sand samples were selected at different depth in order to characterize the various levels of the sediments, recognize and define possible correlations between the layers in the 17 cores and, most important, define the boundary between the Holocene and Pleistocene sediments.
Scanning x-ray fluorescence microscopy and principal component analysis
Authors: Cross Brian
Published: June 2020

A relatively new entry, in the field of microscopy, is the Scanning X-Ray Fluorescence Microscope (SXRFM). Using this type of instrument (e.g. Kevex Omicron X-ray Microprobe), one can obtain multiple elemental x-ray images, from the analysis of materials which show heterogeneity. The SXRFM obtains images by collimating an x-ray beam (e.g. 100 μm diameter), and then scanning the sample with a high-speed x-y stage. To speed up the image acquisition, data is acquired "on-the-fly" by slew-scanning the stage along the x-axis, like a TV or SEM scan. To reduce the overhead from "fly-back," the images can be acquired by bi-directional scanning of the x-axis. This results in very little overhead with the re-positioning of the sample stage. The image acquisition rate is dominated by the x-ray acquisition rate. Therefore, the total x-ray image acquisition rate, using the SXRFM, is very comparable to an SEM. Although the x-ray spatial resolution of the SXRFM is worse than an SEM (say 100 vs. 2 μm), there are several other advantages.
Is spectrometer resolution or system count rate performance more important in quantitative energy-dispersive x-ray microanalysis?
Authors: Fiori C.E. , Swyt C.R.
Published: June 2020

Recently, important improvements have been achieved in both the resolution of energy dispersive spectrometers (EDS) and their count rate performance. Figure 1 is a plot of the count rate performance versus resolution for one EDS system. This particular system was chosen for our study because data were available for 6 pulse processing times. It can be seen that there is a direct trade off between count rate performance and energy resolution. The purpose of this study is to examine the consequences of the various pulse processor conditions for quantitative analysis. A number of analytical problems were simulated including various combinations of acquisition times, degree of spectral overlap, and relative peak heights.

We provide here one example from the study, the analysis of PbS, which offers a difficult spectral overlap of the Pb M lines and the S K lines. We used the recently available computer program DTSA (Desk Top Spectrum Analyzer), to simulate 1000 spectra for each of the pulse processor resolution conditions shown in Figure 1. A linear least squares procedure was used to determine the peak areas.
SIMS studies of Ca and Mg distributions in sintered Al2O3
Authors: Soni K. K. , Thompson A. M. , Harmer M. P. , Williams D. B. , Chabala J. M. , Levi-Setti R.
Published: June 2020

The addition of MgO to α-Al2O3 has been practiced for over 30 years in order to improve greatly the properties of the sintered material. However, a complete understanding of the role of MgO has not been achieved despite significant research efforts by various groups. The most difficult obstacle is microchemical characterization of MgO doped Al2O3. Surface analytical techniques, primarily AES and XPS, have been employed by past researchers in order to analyze the grain boundaries on fractured surfaces of sintered Al2O3. This prior work has met with limited success due to poor sensitivity and spatial resolution. MgO is believed to segregate to the grain boundaries and to retard the grain boundary mobility via a solute drag mechanism; this hypothesis has not been verified experimentally.

In this study, the distribution of Ca and Mg was characterized by a high lateral resolution scanning ion microprobe (SIM) developed at The University of Chicago (UC).
Characterisation of nicalon fibres using EPMA
Authors: Love G , Bleay SM , Chapman AR , Scott VD
Published: June 2020

Nicalon is a fibre produced commercially by melt spinning a mixture of silanes and pyrolising the product. This gives a ceramic fibre, based upon silicon carbide, used for reinforcing metallic and composite materials. The composition of Nicalon is not fully understood but in addition to silicon carbide the presence of free carbon, and silica have been reported together with a non-stoichiometric oxycarbide.

EPMA was carried out on transverse fibre sections prepared from a plate of metal matrix composite using a JEOL 8600M fitted with wavelength dispersive spectrometers. Quantitative data were obtained at a voltage of 15kV using reference standards of silicon carbide (for silicon and carbon analysis) and silica (for oxygen). The analyzing crystals employed for recording CK, OK and SiKα radiation were lead stearate, a W-Si multlilayer (2d = 7nm) and PET respectively. Peak intensity measurements were used except in the case of CK radiation where area measurements were necessary because of obvious differences in peak shape from Nicalon and SiC.
On the Simulation of EEL Spectra Corresponding to Solid and Gaseous Samples
Authors: Zanchi G. , Kihn Y. , Sévely J.
Published: June 2020

The electron energy loss spectra can be considered as the result of the convolution of elementary inelastic scattering processes (1, 2). We have developed a procedure which allows to write the intensity of the spectrum as a function of the energy loss.These calculations take the electron angular scattering into account.

The probability for an electron to suffer an energy loss E and to be deviated through an angle after a single electron-electron interaction of any kind is given by a normalized function D(E, ), which can be written with a good approximation as a product of two functions g(E) and f(), separately normalized. Assuming that the excitation probabilities of any interaction follows a Poisson distribution, for a collection angle θd the intensity of the spectrum can be written in the Fourier space :

Gs(ω) is the Fourier transform of GS(E) which characterizes the transfer function of the experimental device.
Angle-Resolved Energy-Loss Spectra of Gd2O3
Authors: Schattschneider P. , Hofer F.
Published: June 2020

Energy loss spectra of heavy rare earths oxides show two well defined plasmon-like peaks below 40 eV and some intensity variation beyond. Since the high-energy maximum is at about twice the energy as the low-energy maximum, double scattering contributions may mask the former. This effect induces artifacts when one attempts to determine the dielectric function ε(ω) from Kramers-Kronig-analysis (KKA) of the loss spectrum. Knowledge of ε(ω) allows to heuristically assign interband transitions or plasma excitations to particular maxima. Measurements in diffraction mode allow detection of dispersive features in ε(ω,q).

Polycrystalline Gd2O3-films of of 40 nm thickness were investigated at 120 kV in a Philips EM420, attached to which is a Gatan 607 Spectrometer. Spectra were taken in diffraction mode (image coupling) at 8 scattering angles with a q-resolution of ≈ 0.03 Å-1. Energy resolution was ≈ 2 eV. The spectra were combined to a q-dependent loss function, using aperture correction.
On Mode Selection for Quantitative Electron-Energy-Loss-Spectroscopy
Authors: Yang Ying-Ying , Egerton Ray F.
Published: June 2020

The present work shows that, without great care, quantitative EELS measurement using the diffraction mode of TEM operation could be quite inaccurate. In the diffraction mode, a zero-loss diffraction pattern is focused on the TEM viewing screen while the focal plane of the lossy pattern is somewhere above the screen, due to lens chromatic aberration effects. For small to medium camera length, the distance between the focal plane of the lossy pattern and the focal plane of the zero-loss pattern is much smaller than the distance between the zero-loss and lossy images in image mode, for normally used magnification (10,000 or more). However, this smaller distance is not sufficient to ensure that spectrometer-collection efficiencies are more equal for different energy electrons in the diffraction mode compared to those in the image mode.

As shown in Figure 1, lossy diffraction spots expand to discs on the viewing screen because their focal plane lies above the viewing screen.