bluuebunny/crossref_metadata_2025_split huggingface dataset:
The determination of the thickness and composition of multilayered thin films in the SEM by x-ray microanalysis with Monte Carlo simulations
Authors: Gauvin Raynald , Caron Mario , Hovington Pierre , Drouin Dominique , Gagnon Gilles , Currie John F. 
Published: June 2020

X-Ray microanalysis is now a well established technique to determine the composition and the thickness of multilayer structures of different materials. The most popular software used to quantify such system are based on analytical φ(ρz) curves which are approximation of the x-Ray generation process. The computed φ(ρz) curves of multilayered samples are based on mixtures rules and weight functions which are not always accurate. In this paper, Monte Carlo simulations of electron trajectories in solids are used to compute φ(ρz) curves in multilayered specimens directly and then used to computed the K ratios.To validate this procedure, a TiN(100 nm)/Ti(10 nm) multilayer metallization structure deposited on SiO2(100 nm)/Si substrate was used in conjonction with a TiN(400 nm)/Si standard sample. This system is a very active field of research and development in the microelectronics industry. The thicknesses, composition and microstructure of both systems were fully characterized by Elastic Recoil Detection (ERD), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM).
Density of states calculations for Ni-Al Alloys
Authors: Alvarez Jose R. , Rez Peter 
Published: June 2020

Impurities at grain boundaries can have dramatic effects on the ductility or embrittlement of metals and metallic alloys. The mechanism for these effects is controversial, but it is believed that charge redistribution induced by the impurity atoms is responsible. Electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) can be used to measure changes in unoccupied densities of states (DOS) when a small nanometer sized probe is moved across a grain boundary. To interpret the energy loss fine structure band theory is needed to relate the observations, which represent an angular momentum resolved density of states at a particular atomic site, to the local electronic structure in the material.We compare the Linearized Augmented Plane Wave (LAPW) and layered Korringa-Kohn-Rostoker (LKKR) methods for calculating densities of states relevant for energy loss in Ni-Al alloys. Both methods can give the angular momentum resolved densities of states at a particular site and both use the Local Density Approximation (LDA). The LAPW method allows ab initio electronic structure calculations of materials by introducing atomic spheres where the basis wave functions are approximated by solutions of a radial potential; for the interstitial region between the atoms the basis wave functions are approximated by plane waves.
Quantitative high-spatial-resolution microchemical analysis of Fe-Co-Ni transformation-toughened steels
Authors: Lippard H. E. , Dravid V.P. , Olson G.B. 
Published: June 2020

Superior strength-toughness combinations can be obtained in AerMet100 by an austenite→martensite phase transformation of small intralath austenite precipitates. The enhanced toughness in these alloys has been attributed to the presence of “metastable” austenite precipitates, the stability of which is intimately related to the size and composition. The austenite precipitates require high stability to resist transformation under all stress conditions except when in the triaxial stress field of a crack tip. The two primary factors determining austenite stability are size and composition. Thus the microstructure-property correlations and further alloy development require quantitative microchemical analysis of austenite precipitates in the 4-10nm size range.Of the possible analytical techniques, only analytical electron microscopy (AEM) and atom probe-field ion microscopy (AP-FIM) merit consideration by achieving quantitative composition analysis with very high spatial resolution. After exploring both avenues, AEM was chosen as the analytical technique based on its superior speed, counting statistics, and versatility.
Widefield digital images in biological transmission electron microscopy (TEM) obtained by automatic image montage
Authors: Haug F.M.S. , Desai V. , Laake J. , Nergaard P.O. , Ottersen O. P. 
Published: June 2020

A transition to digital recording is taking place in microscopy, including TEM. Biological TEM often requires nanometer resolution within micrometer fields of view, i.e., image widths between 1 and 5 (10) Kpixels in digital terms. Electron dense particles between 1 and 15 nm are used in immunolabelling and in neurohistology, micrometer-sized objects such as synaptic boutons or glial processes are often studied with a need to clearly resolve membranes and filaments.We needed larger fields of view in an image processing system (IPS) to quantify neuroactive amino acids in immunogold labelled ultrathin sections. At startup of our project (1991) megapixel cameras for TEM were few and expensive and we designed a system for on-line image montage.A Gatan 673 Mk3 Wide angle TV camera is adapted to the lateral port of a Philips CM10 TEM. Pixel noise is reduced by frame averaging in a fully equipped Matrox Image 1280 board (EISA version) that also supports variable offset and gain of the analogue signal, real time mapping of gray values 0 and 255 to specific colours, and full handling of 1280 × 1024 pixel images.
The Critical Role of Microscopy and Spectroscopy in the Development of New Materials for Microelectronics Packaging
Authors: Youngman R.A. 
Published: June 2020

It has been over thirty years since sintered aluminum nitride (AIN) has been the focus of many research and development activities in Japan, the U.S., and Europe. Only in the past 5 years has there been significant use of this material in microelectronics. There are many reasons for this considerable time for application including, technology needs and acceptance of a new material. Also important has been the role of materials understanding of AIN through the use of microscopy and spectroscopy. We illustrate the use of both standard and unique characterization techniques to elucidate the nature of the crystalline defects which control the important property of thermal conductivity.The thermal conductivity of pure AIN is 320 W/mK. This value has never been achieved in a sintered ceramic. In order to develop a sintered AIN with a high thermal conductivity it is necessary to understand the factors which control the thermal conductivity.
Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride
Authors: Callahan D. L. 
Published: June 2020

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.
Characterization of boron nitride thin films synthesized by plasma-assisted chemical vapor deposition technique
Authors: Liu J. , Lin S. H. , Feldman B. J. 
Published: June 2020

Boron nitride (BN) is a well-known non-oxide ceramic that has interesting and useful properties for potential industrial applications. The attractive properties of BN include its high-temperature shock stability, high electrical resistivity, anisotropic thermal conductivity and desirable mechanical properties. The potential uses of BN films include oxidation-resistant and anti-corrosive coatings, sensors, optical devices, and high temperature electronics. Thin films of BN have been obtained by a variety of growth techniques including sputtering, ion plating, evaporation, and chemical vapor deposition and associated techniques. To optimize the growth parameters and the performance of BN films, advanced electron microscopy techniques have been employed to study the structural evolution of BN films synthesized by plasma assisted chemical vapor deposition technique (PACVD).The BN films were grown in a capacitively coupled rf plasma reactor with a feedstock of diborane (B2H6), ammonia (NH3), and hydrogen (H2). The growth parameters were the same as previously reported. Chemical analyses of the grown BN films showed that they had significantly more boron (44 at.%) than nitrogen (33 at.%) and contained a large amount of hydrogen (23 at.%).
Silicate-Glass/Sapphire Interfaces Probed with Micromechanical Testing Instruments: Sem and Tem Combined Characterization
Authors: Zagrebelny A. V. , Nelson J. C. , Ramamurthy S. , Carter C. B. 
Published: June 2020

The presence of intergranular phases is a common feature in today's polycrystalline ceramics prepared through traditional sintering routes. Although it has been shown that the chemistry and the microstructure of these phases may be altered, for example, by manipulating the heat treatments to tailor the final material's properties, very little is known about the mechanical properties of the interfaces on the microscopic scale.The mechanical behavior of the interfaces between calcium-alumino-silicate (CAS) glasses and single-crystal α-AI2O3 substrates has been studied with two different types of micromechanical testers. The emphasis of this work is to correlate irregularities observed in the load-displacement curves produced using these testing instruments with the morphology of the deformation regions observed for the microindentations and microscratches. The effect of the substrate orientation on the interfacial properties has also been studied. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the deformation structures associated with the microscratches and microindentations.
Observation of a network structure in asphalt cements
Authors: Rozeveld S. J. , Shin E. E. , Bhurke A. , Drzal L.T. 
Published: June 2020

Paving asphalts are often judged and selected based on their rheological behavior at prescribed temperatures or aging response. Asphalts are considered as a colloidal mixture, where clusters of polar, aromatic molecules are dispersed in a less polar solvent. Thus, the extent to which the solvent phase disperses the associating molecules will determine many of the fundamental asphalt properties. Asphalts are typically divided into four major groups, namely: asphaltenes, resins, aromatics, and saturates. Asphaltenes are the highest molecular weight group and constitute ∼25% of the total asphalt. Resins are very polar in nature and act as a dispersing agent or peptisers for the asphaltenes. The solvent or oily phase (aromatics and saturates) are the lightest molecular weight group and are the bulk of the total asphalt (40-50%).The dispersion of the asphaltenes within the oily solvent is an important property and has been studied by separation and titration methods. In this study, asphalt cements were examined using an Environmental Scanning Electron Microscopy (ESEM) (ElectroScan 2020), and confocal Laser Scanning Microscope (LSM) (Zeiss 10).
Direct imaging of charge transfer
Authors: Zhu Yimei , Tafto J. 
Published: June 2020

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.
Progress in Electron-Probe Microanalysis of Boron in Geologic Samples
Authors: McGee James J. 
Published: June 2020

Despite the availability of modern instrumentation with improved detection and correction systems, the analysis of boron in geologic samples by electron probe microanalysis (EPMA) is often avoided. Many studies resort to using calculated or assumed concentrations of B based upon mineral stoichiometry rather than attempt to quantify the B contents by measurement. Assuming stoichiometric behavior for B is not always valid and disregards the possibility of variations in B content of minerals. Such assumptions can contribute to misleading crystal chemical substitution models for the other mineral constituents.With modem EPMA instrumentation, analysis of B in minerals where B is present in major concentration levels (such as in tourmaline) is possible and should be incorporated into routine analytical procedures by the mineralogical community. The effort to make B measurement routine will reinforce itself, as techniques, standards, and problems are addressed by the geologic community interested in refining the measurement application. Progress in this effort, and some of the factors in need of further consideration are discussed here.
Charge-density wave modulations in the transition metal chalcogenides
Authors: Bennett J.C. , Boswell F.W. 
Published: June 2020

The transition metal chalcogenides, due to the typically large covalency of the metal-chalcogenide bonds, often adopt low-dimensional structures and exhibit charge-density wave (CDW) modulations. Incommensurate (IC) or commensurate (C) modulations structures are observed as well as a rich variety of phase transitions driven by the temperature dependence of the CDW amplitude and phase. Defects of the CDW modulation, including antiphase boundaries (APB) and discommensurations (DC), are of determinate importance for the mediation of these phase transitions. The microstructural phenomena occurring in the quasi-one-dimensional chalcogenides will be surveyed with emphasis on two representative systems: the Nb1-xTaxTe4 solid solution and the MxNb3Te4 (M = In or TI) intercalation compound.The NbxTa1-xTe4 compounds are based on a tetragonal subcell with axes (a x a x c) and consist of an extended chain of metal atoms centered within an antiprismatic cage of Te atoms.
HREM study of phase transformation induced by ion irradiation in Al-Cu-Co-Ge single decagonal quasicrystal
Authors: Chen L.F. , Wang L.M. , Ewing R.C. 
Published: June 2020

Irradiation-induced phase transformation in crystals has been an interesting research field for the past twenty years. Since the discovery of quasicrystals in Al-based alloys, there have been some reports on irradiation-induced phase transformation in quasicrystals by in situ TEM observations. However, detailed study on phase transformation in quasicrystals under ion irradiation at atomic level using HREM is necessary for the fundamental understanding of the process. In this paper, we report the results from a systematic HREM study on phase transformation induced by ion irradiation in Al-Cu-Co-Ge single decagonal quasicrystal (31.4 wt.% Cu, 21.8 wt.% Co and 5.4 wt.% Ge).The TEM specimens of single decagonal quasicrystal were prepared perpendicular to the tenfold axis. The transformation in single quasicrystal was studied by in situ TEM during 1.5 MeV Xe+ ion irradiation at room temperature using the HVEM-Tandem Facility at Argon National Laboratory and examined in detail by HREM using a JEM2010 microscope at the University of New Mexico after the irradiation.
Ultrastructural changes in endothelial cells cultured in heparin-enriched media
Authors: Taylor C. A. , Lemley-Gillespie S. , Xu S.M. , George J. , Mandal A.K. 
Published: June 2020

The widespread use of heparin is due to its ability to reduce clotting and prevent thrombosis. An additional biological property of heparin is the reduction of blood pressure in rat models. This lowering of blood pressure is endothelin-l dependent and results in cell cytoskeleton reorganization, which suggests a mechanism for vascular relaxation.Endothelial cells (CRL 1998 ATTC) reach confluency within 3 days when fed media 199/10% FCS (Sigma) and incubated at 37°C with 5% CO2 at 80% humidity. This growth medium is replaced with fresh medium containing 0-100 U/ml heparin, and the incubation continued for 24 hours. The cells are removed with 0.25% trypsin and pelleted for 2 minutes in a microfuge. Routine procedures for TEM include fixation in 2% buffered glutaraldehyde followed by 1% aqueous OsO4, dehydration in a graded series of acetones, and embedding in Medcast (Pella).
Monte Carlo simulations of the ion-cascade process in the ESEM
Authors: Thiel B.L. , Bache I.C. , Fletcher A.L. , Meredith P. , Donald A.M. 
Published: June 2020

Our Monte Carlo simulations and experimental measurements show the Townsend Gas Capacitor (TGC) model to be highly inappropriate for describing the electron cascade process in the Environmental SEM (ESEM). Previous workers have described the signal collected by the Gaseous Secondary Electron Detector (GSED) as having contributions from secondary as well as backscattered and primary electrons, all being amplified by gas cascade. Although these models are qualitatively correct, they require a more sophisticated description of Townsend’s First Ionisation Coefficient, α. Figure 1 illustrates the short-comings of the TGC models when compared to experimentally obtained amplification curves. (Details of the amplification measurements made with various imaging gases will be given elsewhere, along with specifics of the Monte Carlo Calculations.)The major flaw in applying the TGC model to the ESEM stems from the assumption that the secondary electrons and their environmental daughters reach a steady-state kinetic energy distribution en-route to the detector.
Modeling the electron-gas interaction in low-vacuum SEMS
Authors: Joy David C 
Published: June 2020

The passage of a beam of electrons through the low pressure gas atmosphere in an environmental SEM results in a scattering - and hence a broadening - of the probe, a reduction in the current available for imaging and analysis, and in the production of secondary ions which can also impact the specimen and modify the production of secondary and backscattered electrons. In order to optimize and fully exploit the capabilities of low vacuum SEMs it is desirable to be able to accurately predict these effects. The first step in achieving this aim is to be able to quantitatively predict the behavior of the incident beam.At a gas pressure of 100Pa. the mean free path for 20keV electrons is of the order of 1cm. For a typical working distance of 1cm., therefore, the average electron is only scattered once.
Quantitative EDS analysis in the environmental ESEM using a bremstrahlung intensity-based correction for primary electron beam variation and scatter
Authors: Griffin B.J. , Nockolds C.E. 
Published: June 2020

Quantitative EDS analysis of bulk samples in the scanning electron microscope (SEM) or electron microprobe requires, as a fundamental parameter, a stable and reproducible primary electron beam current Beam current is usually measured with a Faraday cage positioned in the electron column below the objective aperture or in the specimen holder. Reproducibility and stability within 1%/hour is a minimum condition.Primary beam current measurement in the ESEM or any high pressure SEM is difficult to measure. Electron-gas interaction in the biased chamber generates a positive ion flow highly amplified relative to the primary beam (Danilatos, 1990) and generates an x-ray signal from the gas. The latter signal amplitude is dependent on primary beam current, chamber pressure and backscatter electron signal from the specimen (Griffin et al. 1993). These interactions prevent quantification of EDS data standardised to Faraday cage primary beam current measurements or x-ray counts from a reference standard.
Advanced applications and instrumentation for scanning probe microscopy (SPM)
Authors: Grigg D.A. 
Published: June 2020

Scanning probe microscopy (SPM) has continued to advance into new applications and disciplines every year. The development of new techniques and instrumentation for SPM's have enabled researchers to study sample surfaces in a variety of ambient conditions and using a number of contrast mechanisms. A review of new SPM techniques and instrumentation will be presented.Phase imaging is a new technique that provides nanometer-scale information about variations in surface properties, such as adhesion, friction, viscoelasticity, composition and perhaps others, not revealed by any other single SPM technique. An example using phase imaging to differentiate component phases of composite materials is shown in Fig. 1 of wood pulp fiber. The left image is a normal topographic image acquired using the TappingMode™ technique. The right image is the simultaneous phase image. The phase image highlights cellulose microfibrils and a lignin component atop the cellulose component not seen in the topographic image. The details of phase imaging will be discussed.
Round robin AFM study of dealkahzed float glass
Authors: Gesner K.A. , Votava W. E. , Varner J. F. 
Published: June 2020

An extensive study of the surfaces of glass treated in a variety of ways was undertaken at the New York State College Of Ceramics At Alfred University over the past 1.5 years. As the project progressed it became evident that glass surfaces can be very difficult to image because of a variety of factors including, static charge buildup, humidity, and tip reflections, to mention a few. Also, because many of the calibrations and scan parameters are specified by the operator, there is great potential for variability to occur between two or more AFM systems. To study the impact of the variations between operators and instruments, a round robin experiment was initiated, and five identical samples were distributed among five different facilities for AFM analysis; two microscopes were manufactured by Topometrix® and three by Digital Instruments®.A dealkahzed float glass sample was used for this experiment.