bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Light Microscopy: Examples of Practical Problemsolving and Efficiency in Pharmaceutical Quality Control and Formulation
Authors: Stoney D A , McCrone W C
Published: July 2020

Five applications of analytical light microscopy to problem-solving in the pharmaceutical industry are described and illustrated by case examples. Problems included are (1) the caking of pharmaceutical products, (2) chemical incompatibility, (3) nucleation and precipitation, (4) recognition of hydrates and polymorphs, and (5) identification and sourcing of contaminant particles.

Considerable effort goes into the sizing of solid pharmaceutical raw materials and products. In many instances, particle size is used to help control the rate and uniformity of dissolution, which in turn affects the kinetics of drug delivery. Caking is a macroscopic description of the change in a sample from a finely-divided powder to a single solid molded aggregate. Caking obviously has a severe impact on handling and dissolution characteristics.

Caking of a powder is almost always caused by moisture through the cyclical dissolution and precipitation on the surfaces of the particles. When exposed to sufficient vapor pressure, often through changes in humidity or temperature,
Analysis of IN-SITU Converted Chrysotile Asbestos Fibers in Sprayed on Fireproofing
Authors: Sabatini R L , Sugama Toshi , Petrakis Leonidas
Published: July 2020

A BNL-Grace process has been developed to chemically convert in-situ, the chrysotile fibers of sprayed-on fireproofing products to an unregulated glassy material. The effectiveness of this process has been convincingly demonstrated using Analytical Electron Microscopy and X-Ray Diffraction techniques.

Asbestos minerals were used in fireproofing materials because of their excellent physical properties including fire resistance, high tensile strength, heat and electrical insulation, and resistance to acids and alkali. But in 1975 the Environmental Protection Agency began regulating materials containing > 1% asbestos.

The new in-situ BNL-Grace process, which uses a foamy solution sprayed directly onto asbestos-containing fireproofing chemically digests essentially all the asbestos fibers, transforming them into harmless materials. After treatment, the fireproofing is no longer a regulated material. The process produces essentially no waste.

Our problem was to demonstrate that all of the asbestos was converted and that the remaining materials were no longer regulated. Typical analysis methods use conventional optical and Polarized Light Microscopy (PLM) to measure and observe fibers.
Applying Microscopy in Forensic Science
Authors: Lee Henry C
Published: July 2020

Microscopy is of vital importance in the real world of the forensic scientist. In today's society, physical evidence is critical to the criminal justice system for the detection, investigation and prosecution of criminal acts. A trail of microscopic fibers led investigators in Atlanta to the conviction of the serial killer, Wayne Williams. Flecks of paint on a hit-run victim, analyzed microscopically, can be compared with the paint on a suspect vehicle to exclude or match it to the crime. The forensic firearms examiner compares the microscopic striations on a bullet to match it to the gun it was fired from. Microscopes are used throughout the modern forensic laboratory. They are essential in searching for evidence. They aid the examiner in identifying and comparing trace evidence. As the scales of justice symbolize forensic science, microscopes symbolize the trace evidence examiner.

Because of the variety of physical evidence, forensic scientists use several types of microscopes in their investigations.
Measurements of Fine Volcanic ASH Via Stereoscopy in the Scanning Electron Microscope
Authors: Mills OP , Rose WI , Riley CM
Published: July 2020

Volcanic eruptions inject tons of silicic material into the atmosphere. Large, dense material falls out within a few hours whereas fine size fractions, < 10 μm radius ash, may remain airborne for weeks to months. Protection of human population centers and aircraft requires predictive atmospheric transport models. Many of these models assume the ash particles are spherical but abundant qualitative studies of ash particles demonstrate irregular shapes ranging from parachute-like bubble-wall shards to polygonal shaped mineral grains. These non-spherical shapes increase atmospheric drag. The accuracy of transport models may be improved with a better understanding of the actual shapes found in fine ash particles. Therefore, the objective of this study is to accurately determine three-dimensional shape measurements via stereoscopic methods using the scanning electron microscope.

The scanning electron microscope is an ideal imaging platform for collection of stereo pairs because of its utility in stereoscopic height measurement.
Characterization of Age Hardening in a 319 AL Alloy
Authors: Jahn R , Donlon W T , Allison J E
Published: July 2020

319 Al (7.2-7.7wt% Si, 3.3-3.7%Cu, 0.25-0.35%Mg, 0.4%max.Fe, 0.2-0.3%Mn, 0.25%max Zn, 0.25%max Ti) is utilized by the automotive industry for engine blocks and cylinder heads. Detailed understanding of the age hardening behavior of these types of alloys is important to optimize the processing of these components to yield the desired physical properties. Age hardening curves for temperatures between 100 and 305°C have been determined for a commercial grade 319 Al alloy having a dendrite arm spacing of 30(im. Samples for TEM were prepared by conventional grinding and dimpling followed by ion milling at 4keV at liquid nitrogen temperatures. The phases formed within the primary aluminum dendrites during age hardening were characterized by JEOL 2000FX and an OXFORD ISIS microanalysis system.

Age hardening curves for Al-Cu alloys are characterized by multiple hardening stages as shown by Silcock, et al. Figure 1 shows an example of a 150°C age hardening curve for 319 Al.
Fractographic Evaluation of Thermally Stressed Single Crystal Sapphire
Authors: Wajer SD , Cohen PH
Published: July 2020

Optical, video and scanning electron microscopic observations show fractographic features that are used to determine the crack propagation direction and crack origin in thermally stressed single crystal sapphire hemispherical shells. These features have been typically identified in materials with symmetrically applied stresses and simple geometries. This fractographic evaluation of sapphire is unusual because of the hemispherical geometry and complex mechanical and thermal stress conditions. Computer models predict the thermal stress response of the sapphire from fast acting asymmetrical heating patterns generated during controlled laboratory testing. These experimental tests are conducted to validate the computer model predictions. When an experimental structure fails to meet the survival limits predicted by the computer model, a fractographic evaluation is conducted to determine fracture mode and to locate the crack initiation site.

Fractured pieces are examined and photographed using a low magnification, binocular optical microscope and a high resolution video camera with digitizing capabilities.
Application of SEM, TEM and CBED Techniques for Compound Identification in Stress Corrosion Cracking Failure.
Authors: R. Caballero  , A. Quintero
Published: July 2020

Stress corrosion cracking has been a problem in aluminum alloys exposed to an aggressive environment under high static residual tensile stress. This work is concerned with the application of electron microscopy to investigate possible causes that led to failure through stress corrosion cracking in the aluminum alloy 5182. This alloy is commonly used for making carbonated beverage containers. The containers in this study did not experience any problem at the time of the filling. However, after humid storage periods going from a few days to a few weeks, leakage at the can ends was reported in many of them. These leaks developed from a failure referred to as aluminum can end blow out.

Figure la shows an SEM micrograph of a cross section of the score imposed on the top of the can during manufacturing. The unscored metal below the score is broken when the ring or tab is pulled out during opening.
“Real-World” Microscopy: Understanding Environment-Sensitive Behavior of Ni-Base Welds
Authors: Burke M G , Wehrer R J , Brown CM
Published: July 2020

Ni-base alloy welds such as EN82H weld metal are frequently employed in nuclear power applications where resistance to corrosion is required. Results of a recently reported study of the mechanical properties of EN82H welds show that this alloy is susceptible to low-temperature (∼100°C) environmental embrittlement (LTEE) in hydrogenated water. LTEE is a manifestation of hydrogen embrittlement in these alloys.1 Recent LTEE tests have demonstrated a beneficial effect of a high-temperature (∼1100°C) anneal and furnace-cool in alleviating the material's susceptibility to LTEE. Understanding the reason for the reduction in LTEE susceptibility requires detailed characterization of the microstructure so that the specific structural and compositional changes that have been induced by the solution-anneal can be identified. This study reports the results of light optical and analytical electron microscopy (AEM) characterization of the microstructures of as-fabricated and as-solution-annealed EN82H welds with the objective of providing insight into the observed LTEE behavior.
Terra Incognita: Spectra from Edges and Elements not in the EELS Atlas
Authors: Former J A , Buck E C
Published: July 2020

The EELS Core-Loss Atlas, like a road map, serves as an essential guide for practitioners of electron energy loss spectroscopy (EELS). Even the best maps will be incomplete, however, and one may need to plot a course by other means. Our work with materials from the nuclear fuel cycle has required new spectral lines, and even new elements, to be charted. The actinides and technetium, for instance, have important spectral features above 2 keV. The EELS technique has not often been used for detecting lines above about 2 keV because of the rapidly diminishing differential cross sections for these higher energy transitions. However, as instrumentation has progressed from scanning to parallel to CCD-array detection, statistical limitations on the high energy data have been improved by orders of magnitude. Also, in some cases, the notion of higher energy lines as “weak” is excessively pessimistic.
Incommensurate Structures in Rhenium Disilicide
Authors: Misra A , Chu F , Mitchell TE
Published: July 2020

The binary ReSi2 and ternary (Mo,Re)Si2 alloys are of interest due to potential applications as infrared detectors [1]. Also, Re may be a beneficial alloying element to MoSi2 which is a potential high temperature structural material [2]. A recent study of the structure of ReSi2 by X-ray diffraction (XRD) revealed an orthorhombic distortion (a= 0.3121 nm, b= 0.3139 nm and c= 0.7670 nm) from the tetragonal CI lb MoSi2 structure and a Si-deficient composition of Re4Si7 [3]. Further, a weak monoclinic distortion (β=89.87°) was also inferred from high-resolution XRD [3]. In the present investigation, the orthorhombic distortion and the Si-deficient stoichiometry were confirmed by XRD and the structure of arc-melted Re4Si7 studied by transmission electron microscopy (TEM).

A bright field (BF) TEM image and the corresponding [010] zone axis selected area diffraction pattern (SADP) are shown in Fig. 1. In addition to the fundamental reflections for tetragonal Cllb MoSi2 structure,
Defects in Nb-Cr-Ti C15 Laves Phase Alloys
Authors: Kotula P G , Carter CB , Chen K C , Thoma D J , Chu F , Mitchell T E
Published: July 2020

Laves-phase intermetallics are of potential use as high-temperature structural materials. NbCr2-based C15-structured alloys are of particular interest for such applications. The effect of Ti alloying on the microstucture and mechanical properties of such alloys has been investigated and it has been shown that Ti can improve the fracture toughness of the monolithic CI 5 Laves phase8 and dual-phase (bcc and CI 5) alloys. In the Nb-Cr-Ti system, there is a complete solid solution between NbCr2 and TiCr2, with a significant range of solubility of the C15 phase and a large two phase, bcc and C15, region. The initial characterization of the defect structure of an alloy of overall composition Nb10Cr75Ti15 is discussed here.

Nb10Cr75Ti15 was prepared by arc-melting the high-purity elemental metals followed by annealing at 1400°C for 120 h and then cooling at l°C/min. Specimens were prepared for observation in the TEM by cutting 3 mm discs with a coring saw, followed by dimpling and ion milling.
Microstructure of the Die-Upset Nd (Pr)-Fe-B Hard Magnets Studied by Magnetic and High Resolution Transmission Microscopy
Authors: Volkov VV , Zhu Y , Lewis LH , Welch DO
Published: July 2020

Magnetic properties of permanent magnets are sensitive to their microstructure. In particular, for a class of Nd(Pr)-Fe-B magnets very different coercivity and energy products may be obtained by different processing techniques. In this work we report on the preliminary results of magnetic domains (MD) structure and grain boundaries (GB) analysis of such hot-deformed Nd(Pr)-Fe-B magnets. To reveal the fine details of MD and GB interaction the experiments were carried out by the combined use of Magnetic Foucault-Fresnel Imaging and High Resolution Microscopy.

The magnets used in this study had a nominal composition Nd13.75Fe80.25B6 (I) and Pr13.75Fe80.25B6 (II) and were produced at the General Motors Research and Development Center. Buttons of the die-upset samples were prepared from overquenched ribbons using the melt-spun technique. Thin sections were cut from the buttons obtained by die-upset of the ribbons of I and II. These sections were mechanically polished and then ion milled until perforation. Electron microscopy was done using a JEM 2000FX microscope operating at 200 kV.
Stress-Induced Phase Transformations in SiC
Authors: Pirouz Pirouz
Published: July 2020

Tetrahedrally co-ordinated materials can undergo stress-induced structural transformations often under invariant plane strain conditions; examples of such transformations are twinning and polytypism. The structure of a tetrahedrally co-ordinated material, XY, may be considered in terms of an assembly of “normal”, Ti’and “twinned” tetrahedra, T'I’all connected to each other at their corners. In some of these materials, e.g. SiC, GaN or CdS, these corner-sharing tetrahedra may be connected to each other in different ways, giving rise to different polytypes. In this paper, a dislocation model for polytypic transformations is discussed and a few examples of stress-induced transformations are illustrated.

In general, dislocations in XY polytypes he on basal (0001) planes and are generally dissociated into “leading’ and “trailing” partial dislocations with Burgers vectors b1 and bt’ respectively. There is also good evidence that dissociated dislocations in tetrahedrally-coordinated materials belong to the glide set and move on the slip plane in a dissociated manner.
Dislocations in Ceramics
Authors: Carter C Barry
Published: July 2020

Of the four groups of crystal lattice defects, i.e., point defects, dislocations, interfaces and particles, dislocations are often thought to be the least important for ceramic materials. However, they not only give considerable insight into interfaces (they can be thought of as the link between point defects and interfaces), but they are becoming more important as interest grows in epitactic oxide heterostructures.

The present paper provides a review of our current understanding of dislocations in ceramics. To simplify the discussion, we can separate the task into the following sections, namely Simple oxides (MgO, ZnO etc.)Simple non-oxides (A1N, GaN, SiC, TiC, etc.)More complex binary oxides (AI2O3, Fe203, etc.)Multicomponent oxides and complex non-oxides (spinels, garnets, S13N4)Interfacial dislocations (misfit, grain boundary, etc.)

The features which are most often associated with ceramic materials are their complex structures and large unit cells. For example in bcc garnets, the smallest Burgers vector for a perfect lattice dislocation is ∼0.8nm long.
Z-Contrast Imaging of Ordered Structures in Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3
Authors: Yan Y , Xu Z , Viehland D , Pennycook S J
Published: July 2020

Lead-based cubic perovskites such as Pb(B2+  1/3B5+  2/3)O3 (B2+ = Mg, Co, Ni, Zn; B5+ = Nb, Ta) are relaxor ferroelectrics. Localized order and disorder often occur in materials of this type. In the Pb(Mg1/3Nb2/3)O3 (PMN) family, previous studies have proposed two models, space-charge and charge-balance models. In the first model, the ordered regions carry a net negative charge [Pb(Mg1/2Nb,/2)03], while in the second model it does not carry a net charge [Pb((Mg2/3Nb1/3)1/2Nb1/2)03]. However, no direct evidence for these two models has appeared in the literature yet. In this paper we report the first direct observations of local ordering in undoped and La-doped Pb(Mg1/3Nb2/3)03, using high-resolution Z-contrast imaging.

Because the ordered structure in Ba(Mg1/3Nb2/3)03 is well known, the Z-contrast image from an ordered domain is used as a reference for this study. Fig. 1(a) shows the projection of the supercell of fully ordered Ba(Mg1/3Nb2/3)03 along the [110] direction.
Atomic Scale Structure-Property Relationships of Defects and Interfaces in Ceramics
Authors: Stemmer S , Duscher G , James E M , Ceh M , Browning ND
Published: July 2020

The evaluation of the two dimensional projected atom column positions around a defect or an interface in an electronic ceramic, as it has been performed in numerous examples by (quantitative) conventional high-resolution electron microscopy (HRTEM), is often not sufficient to relate the electronic properties of the material to the structure of the defect. Information about point defects (vacancies, impurity atoms), and chemistry or bonding changes associated with the defect or interface is also required. Such complete characterization is a necessity for atomic scale interfacial or defect engineering to be attained.

One instructive example where more than an image is required to understand the structure property relationships, is that of grain boundaries in Fe-doped SrTi03. Here, the different formation energies of point defects cause a charged barrier at the boundary, and a compensating space charge region around it. The sign and magnitude of the barrier depend very sensitively on the atomic scale composition and chemistry of the boundary plane.
White Lines in the Iron L2,3 Electron-Energy-Loss Spectra of Pyrite and Greigite
Authors: Cheng S C , Wilkin R T
Published: July 2020

The white lines on the L2,3 absorption edges of the transition metals and on the M4,5 absorption edges of the rare earth elements are the most prominent feature in electron-energy-loss spectra (EELS). The white lines of these elements have been studied and used to determine valance and coordination of atoms in various systems. Fe-O compounds with valence 2, 3 and mixed valence states, for example, have been carefully examined and characterized. However, in spite of the importance of iron sulfides in geochemistry and environmental science, the EELS data of these compounds are not available. Pyrite (FeS2) is widespread in hydrothermal ores, modern sediments, and sedimentary rocks deposited throughout the geologic record. The ferromagnetic iron sulfide greigite (Fe3S4) is another important compound. It has been recognized as a carrier of magnetic remanence in young sediments. Sedimentary greigite may be precipitated inorganically or biogenically by magnetotactic bacteria.
Improved Adhesion of the c-BN Film by the Post ION Implantation: TEM and FTIR
Authors: Sung C , Gunasekara S , Byon ES , Lee SW , Lee SR
Published: July 2020

Boron nitride thin films have been deposited on (100) oriented Si substrate by magnetically enhanced activated reactive evaporation technique. The build up of c-BN is normally accompanied by strong compressive stresses. When these stresses exceeds the strength of the adhesion forces at the interface, adhesion fails causing the destruction of the c-BN film. This has been one of the major limiting factors of using the c-BN films for many important industrial applications such as cutting tools and semiconductor devices.

In this experiment, the plasma immersion ion implantation has been applied to improve the adhesion of the film. The post ion implantation was conducted at several implantation energies and constant dose. The effect of ion implantation on the microstructures was investigated by Fourier Transform Infrared spectroscopy and Transmission Electron Microscopy.

Infrared characterization of c-BN film by FTIR (Fig.l) shows that the IR spectra of the specimens prepared at all energies but 72 kV have strong absorption band at 1080 cm-1 corresponding to cubic boron nitride.
Carbon-Induced UV Sensitivity in Aluminum Nitride
Authors: Berta Y , Gerhardt R A
Published: July 2020

Aluminum nitride, translucent, calcia-sintered and hot pressed, with its superior thermal properties has applications in high performance electronic devices such as multichip modules. In these applications, A1N is exposed to high energy electromagnetic sources which could alter its properties; for example, upon UV irradiation, thermal conductivity drops and dielectric loss increases. These observations indicate that the UV altered properties are due to the presence of impurities. The early studies concentrated primarily on oxygen doped samples, which photodarken upon UV exposure; the role of other impurities was not considered.

In the current work, we consider the role of carbon in the microstructure of two very low oxygen content (< 0.3 wt %), carbon-containing samples, labeled B and E, for the ultimate purpose of 3 determining the mechanism by which carbon impurities affect the properties of A1N. Previous work on these samples correlated higher carbon content with a lower increase in the dielectric loss factor, after UV irradiation,
Microstructure and Strain Relaxation of Epitaxial SrRuO3 Films
Authors: Jiang J C , Pan X Q , Gan Q , Eom C B
Published: July 2020

It is widely believed that the stress in the epitaxial thin films, caused by the lattice mismatch between the thin film and substrate, has a strong influence on the properties. For example, lattice strained epitaxial thin films of SrRu03 grown on (001) SrTiO3 demonstrated magnetic and electrical properties different from those in bulk materials.1 In this paper, we report the effect of strain relaxation of the thin film on microstructure by means of transmission electron microscopy (TEM).

SrRuO3 thin film on a vicinal (001) SrTiO3, with a miscut angle 0.9° and miscut direction 5.7° away from the in-plane [100] axis, was grown by 90° off-axis sputtering. Cross-section and plan-view TEM specimens were prepared following the procedure described in Ref. 2. TEM investigations were conducted in a Philips CM 12 microscope in the EMAL at the University of Michigan.

X-ray diffraction studies of the as-grown SrRu03 thin film using a four-circle diffractometer showed that the film consists of a single [ 110]-type domain structure.
Determination of the Site Occupancy of Holmium in SrTiO3 by Alchemi
Authors: Cheng S C , Hitomi A , Randall C A
Published: July 2020

The perovskite structure is based upon the mineral CaTiO3, which is a pseadocubic at room temperature. The ideal structure has a twelve fold coordinate A-site, and an octahedral coordinated B-site, and the face-centered position being oxygen. The perovskites have been of commercial interest for capacitors owing to their high dielectric constants. The crystal chemistry related to the perovskite based dielectrics multilayer capacitors (MLCs) is of interest in this paper. The MLCs with base metal internal electrodes such as copper and nickel have been studied for many years. To avoid oxidation of the nickel or copper electrodes during sintering, a reducing atmosphere is necessary. However, reduced firing causes two basic problems: an increasing of conductivity of the BaTiO3, dielectrics and limitation on reliability by the migration of oxygen vacancies. The solution for the first problem is to use acceptor dopants, such as MnO and more stable oxide additives, such as CaZrO3 to increase the resistivity of the dielectrics.
On Devitrification of Monticellite (CaMgSiO4) Films Grown on (001)-Oriented Single-Crystal MgO.
Authors: Yanina Svetlana V , Johnson Matthew T , Mao Zhigang , Carter C Barry
Published: July 2020

Silicate glasses are the most common constituents of intergranular phases which can be found in liquid-phase sintered ceramics [1]. Silicates are known to influence the structure of ceramic interfaces which, in turn, frequently affect mechanical properties of ceramic materials [2]. In earlier studies of silicate glasses on single-crystal alumina Ramamurthy et al [3] and Mallamaci [4] showed that the morphology of dewetted glass films and the mechanism of devitrification depend on the crystallographic orientation of the substrate surface. In continuation of these studies, results are presented on the dewetting behavior of monticellite (CaMgSi04) in contact with the (OOl)-oriented surface of single-crystal MgO. Due to the simplicity of sample preparation and availability of 3- dimensional topographic information, Atomic Force Microscopy (AFM) was used for surface characterization. These AFM results are complemented by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) data on the chemical composition and the structure of the glass-substrate interface.
Defects in Pseudo-Orthorhombic Anorthite on Basal Sapphire
Authors: Mao Zhigang , Johnson Matthew T , Carter C Barry
Published: July 2020

Crystallization of intergranular glass films can influence the performance of ceramic materials [1]. The crystallization of anorthite glass films has been studied in situ in the transmission electron microscope (TEM) [2]. The films are grown by pulsed-laser deposition (PLD) on sapphire (α-AI2O3) substrates. These substrates can be pre-thinned to electron transparency, so that contamination or microstructural damage of the TEM specimen due to the thinning process can be eliminated. This process also allows the microstructure of the glass films to be characterized before crystallization; the evolution of specific features of the film can then be tracked through repeated heat treatments. Prior to the crystallization of the anorthite glass films, observations confirmed that all the glass films deposited by PLD are indeed amorphous. Crystallization experiments were performed in a Philips CM30 TEM equipped with a Gatan single-tilt heating holder. Each specimen was heated in the microscope to a temperature of about 1200 °C at a heating rate of about 30 °C/min. and held at this temperature for 20 minutes.
The Effect of an Electric Field on the Reaction Between Oxides
Authors: Johnson Matthew T , Carter C Barry
Published: July 2020

It is well known that diffusion in ionic materials occurs primarily by the movement of charged species. Therefore, an applied electric field can provide a very large driving force for mass transport. In the present study, thin films of In2O3 and Fe2O3 have been deposited on (001) and (111) MgO using pulsed-laser deposition (PLD). These thin-film diffusion couples have then been reacted in an applied electric field at elevated temperatures. The electric field directly influences the diffusion of the cations in the constitutive layers. Through the use of both transmission (TEM) and scanning (SEM) electron microscopy, diffusion couples reacted either with and without an electric field have been analyzed to examine the effect that an induced ionic current can have on solid-state reaction processes.

The apparatus for reacting the diffusion couples in a field has been described elsewhere. The diffusion couples were characterized in cross-section by SEM and TEM techniques.
Image Periodicities Introduced by Three-Fold Astigmatism in HRTEM Images of α-Al2O3 and Related Materials
Authors: Medlin DL , Smugeresky JE , Cohen D
Published: July 2020

HRTEM images of α-Al2O3 oriented along [1100] often exhibit a modulation of the basal fringe intensity with a period that corresponds to twice the basal plane spacing. In the example shown in figure 1, note the strong basal fringe contrast in the A12O3 with a period of 4.33 Å. HRTEM image simulations for ideal imaging conditions fail to reproduce this doubling of the lattice fringe period. Instead, simulated images predict that the (0006) fringes (d0006=2.17 Å) should be of equal intensity (e.g., see Figure 3a). Incorrect beam and/or crystal tilt can strongly affect HRTEM image contrast. In particular, anomalous periodicities can arise under beam and crystal tilt conditions for which normally kinematically and dynamically forbidden diffracted beams contribute to the image. More recently, the importance of 3-fold astigmatism on HRTEM imaging has been recognized. As with beam tilt, this lens aberration produces asymmetrical phase shifts in the diffracted beams.
Heterogeneous Oxidation and Precipitation of Aqueous Mn(II) at the Goethite Surface: A SPM Study
Authors: Rakovan John , Hochella Michael F
Published: July 2020

Since its invention inl982 scanning probe microscopy (SPM) has become an important analytical tool in every branch of physical science. The two most widely used types of SPM are atomic force Microscopy (AFM) and scanning tunneling microscopy (STM). Both AFM and STM allow measurement of the microtopography of a surface down to the atomic scale. Many spin-off applications such as lateral force and magnetic force allow measurement of a variety of the physical properties of a surface while imaging its microtopography. SPM can be done in both air and liquid and hence can be used to observe the interactions that take place at a solid-solution interface.

SPM has been used in mineralogy and geochemistry since 1989. Here as in other applications the great strength of SPM is in the characterization of the heterogeneous nature of mineral surfaces and the ability to observe many geochemical processes in real time.
Microstructures and Microanalysis in ALH84001: Minerals or Martians?
Authors: Harvey Ralph P , Bradley John , McSween Harry Y
Published: July 2020

The martian meteorite ALH84001 leapt into the spotlight in late 1996 when a NASA-led research team suggested that it contained evidence of biotic activity on ancient Mars. ALH84001 is unique among the martian meteorites- a cumulate rock made up predominantly of orthopyroxene, with interstitial maskelynite (feldspar turned into a diaplectic glass by shock), apatite, chromite and sulfides. Highly brecciated fracture zones cut through the rock, presumably a result of impacts, and within these zones is a variable amount of secondary carbonate. This carbonate, the most extensive secondary mineral found in any martian meteorite, formed during significant interaction between martian crust and volatiles, and represents a unique access point toward understanding the environment of ancient Mars. However, the conditions under which this carbonate formed are less clear. While claims for evidence of biotic activity are predicated on carbonate formation at low (<100°C) temperatures under water-rich conditions, other research suggests much less hospitable conditions, with little water present and formation temperatures approaching 700°C.
Local Strain Measurements in Hexagonal Systems
Authors: Kisielowski Christian , Schmidt Olaf
Published: July 2020

It is challenging to access the microscopic distribution of strain in subsurface systems with a lateral resolution better than 1 nm and an accuracy of about 10-3 because such measurements require the detection of displacements by 1 pm at near atomic resolution. Nevertheless, such measurements are commonly desirable, in particular, for the investigations of thin heteroepitaxial films. A particular method developed in the past extracted geometrical information from unit cells in lattice images to perform this task in thin layers of cubic quantum well structures. Strain relaxation in thin TEM samples may falsify such measurements and needs to be controlled. It is the purpose of this paper to describe a quantitative method to measure strain with the required accuracy and resolution in the more complex hexagonal systems. A AxGa1-xN/GaN heterostructure grown on a sapphire substrate was investigated. Local strain comes from compositional variations which alter the size of the unit cells that are shown in Figure 1.
The Determination of Copper Composition Profiles in Semiconductor Device Aluminum Interconnect Electromigration Test Lines using Electron Probe Microanalysis (EPMA)
Authors: Oparowski JM , Sriram TS , Ambrose V
Published: July 2020

Extensive long range transport of copper has been observed in polycrystalline aluminum-copper (Al-Cu) interconnects subjected to accelerated electromigration testing. Cu depletion is believed to be the rate limiting factor for electromigration damage accumulation. It is not clear if this is also the case for Al-Cu interconnects with bamboo/near-bamboo microstructures. In order to understand this phenomenon, Cu transport under electromigration conditions in bamboo microstructures has to be characterized quantitatively. This paper describes the procedure used to determine Cu distributions on a series of bamboo test structures subjected to accelerated electromigration (EM) testing. Copper composition profiles were determined for these structures through the use of electron probe microanalysis (EPMA) techniques and customized corrections for non-standard interaction volumes.

Aluminum (0.5 wt.% Cu) interconnect test line structures were fabricated with four metal layers and surrounding silicon dioxide dielectric. Following EM testing, the samples were deprocessed to expose the test lines at metal layer three, as shown in Figure 1.
Hrtem Study of Interface Structure Of Heteroepitaxially Grown GaAs Thin Films on GaAs(l00)
Authors: Dai ZR , Chegwidden SR , Ohuchi FS
Published: July 2020

GaSe, a member of the III-VI compound semiconductors, and its related compounds have recently gained an considerable attention because of their high non-linear optical coefficients in the infrared ranges, making them candidates for second harmonic generation (SHG) materials[l,2]. While the optical properties of those materials in bulk form are quite promising, poor thermal and mechanical properties preclude their easy applications. In thin film devices, the thermal and mechanical properties are dominated by those of the substrate, therefore, heteroepitaxially grown thin films of GaSe and related materials on substrates such as GaAs, Si and A12O3 should enable their application in device structures. Development of such new generation of materials, however, require fundamental knowledge about the surface and interface structure that play decisive roles in the thin film crystallinity and materials properties.
Microstructure of Porous Silicon Thin Films
Authors: Berta Y , A. Gerhardt R
Published: July 2020

Porous silicon has potential applications in the microelectronics industry. It has been investigated as an electroluminescent source1, as a sensing device in chemical sensors and as an antireflective coating for solar cells. The low efficiency of the solar cells is enhanced by the antireflective coating that porous silicon provides, while the cost of fabrication of the cells is decreased. Porous silicon is normally processed by electrochemical anodization of silicon wafers. Since parameters such as current density, anodization time, and surface conditions can affect the microstructure of the films obtained, we varied the current density to study the effect of the microstructure on the resultant reflectance for the purpose of improving it. It has been found that higher current densities result in higher reflectance films than the lower current densities.
Solid-Phase Epitaxial Regrowth of GaAs by in-situ Controlled Intermediate Phase Decomposition
Authors: Farrer JK , Caldwell DA , Palmstrom CJ , Carter CB
Published: July 2020

A transmission electron microscopy (TEM) analysis on the regrowth of GaAs by a two-stage reaction between a metal layer (M) and a GaAs substrate is presented. The first stage of the regrowth process is the consumption of GaAs in a low temperature reaction with the metal layer, producing an intermediate phase of (MxGaAs). A second solid-phase reaction, induced by the deposition of Ga or As, results in the decomposition of the intermediate phase and the epitaxial regrowth of a layer of GaAs. The sample growth and reactions were performed in-situ in a molecular beam epitaxy system, using Ni for the metal and As deposition for the second reaction. TEM data confirm the formation of the ternary phase, NixGaAs, and its subsequent decomposition into NiAs and GaAs by reacting with the deposited As. A layer of AlGaAs, 100 nm thick, was grown in all samples as a marker.
Scanning Capacitance Microscopy of Dopants in III-V Semiconductors
Authors: Lang David V
Published: July 2020

Scanning Capacitance Microscopy (SCM) was first developed in 1985 as a method for sensing tip-to-sample spacing for surface topography profiling in connection with the RCA VideoDisc. Williams and coworkers were the first to use an SCM for obtaining dC/dV doping profiles in semiconductors, albeit with a rather modest resolution of 200 nm. More recently, it has been developed as a 50-nmresolution tool for microscopic doping analysis of semiconductors by measuring the tip-to-sample rf capacitance in an AFM controlled by other means, e.g. by laser beam deflection of a cantilever tip. In this paper we report on the application of SCM to study the 2D doping profiles of InP-based devices, such as multi-quantum well lasers.

It is particularly convenient to prepare cross sections of III-V devices, since the material readily cleaves on [110] planes, as compared to silicon where cross sections must be obtained by painstaking polishing.
Electron Holography of Semiconductor Junctions
Authors: McCartney M R , Li Jing
Published: July 2020

TEM has not traditionally contributed to characterization of semiconductor junctions, except for some intriguing results by Perovic, Hull and Alvis where highly doped layers gave contrast under very specific sample preparation and imaging conditions. Since electron holography is sensitive to the phase of the electron wavefront that has passed through the sample, it has the potential to provide voltage contrast. In principle, given its inherent two-dimensional and quantitative character, electron holography is a strong candidate for analysis of semiconductor device junctions.

The sample for the work reported here was one of a group of test specimens fabricated at IBM for a dopant metrology round-robin comparison to evaluate various profiling methods. The substrate was <100> p-type silicon, boron-doped at 11-25 Ω-cm-1. The test structure was fabricated using low- temperature epitaxial growth and consisted of an abrupt p-n junction, formed by abutting 1020cm-3 doped regions of boron and phosphorus
Scanning Electron Microscopy of Dopants in Semiconductors
Authors: Venables D
Published: July 2020

It has been demonstrated that doped regions in semiconductors yield contrast in secondary electron images taken under appropriate imaging conditions. Perovic et al. attributed this "electronic" contrast to surface potentials arising from the bending of the energy bands at the surface of the semiconductor. This band-bending results from the presence of surface states which pin the Fermi level. These effects have found application to an important problem in the electronics industry -- the profiling of dopant distributions in two-dimensions. However, such dopant distributions are rarely uniform, i.e., the dopant concentration may change over many orders of magnitude within distances of only a few tens to hundreds of nanometers. Therefore, it is necessary to understand how the observed contrast from the doped regions varies for non-uniform dopant distributions to apply the technique to real electronic devices.
Microscale Elemental Imaging of Semiconductor Materials Using Focused Ion Beam Sims
Authors: Stevie F A , Downey S W , Brown S , Shofner T , Decker M , Dingle T , Christman L
Published: July 2020

The semiconductor industry demands elemental information from ever smaller regions. Two types of information in demand are two dimensional dopant profiles for the MOS transisitor and identification of particles as small as 30 nm diameter. The work of Levi-Setti and others resulted in liquid metal ion source (LMIS) instruments that provided secondary ion mass spectrometry (SIMS) images using Ga+ beams with 20 nm lateral resolution. It is now possible to purchase focused ion beam (FIB) systems with 5 nm beam capability and SIMS detection.

The application of LMIS SIMS to meet semiconductor demands has been pursued in our laboratory with a FEI-800 FIB. SIMS imaging of semiconductor patterns after etch has shown the ability to identify boron and carbon contamination. Figure 1 shows boron in a comb structure after a BC13 etch. The boron can be shown to be removed by a cleaning step.
Direct Imaging of Device Characteristics In a Focused ion Beam System
Authors: Campbell A N , Soden J M
Published: July 2020

A great deal can be learned about integrated circuits (ICs) and microelectronic structures simply by imaging them in a focused ion beam (FIB) system. FIB systems have evolved during the past decade from something of a curiosity to absolutely essential tools for microelectronics design verification and failure analysis. FIB system capabilities include localized material removal, localized deposition of conductors and insulators, and imaging. A major commercial driver for FIB systems is their usefulness in the design debugging cycle by (1) rewiring ICs quickly to test design changes and (2) making connection to deep conductors to facilitate electrical probing of complex ICs. FIB milling is also used for making precision cross sections and for TEM sample preparation of microelectronic structures for failure analysis and yield enhancement applications.
Templating Effects On C54-Tisi2 Formation In Ternary Reactions.
Authors: Quintero A , Libera M , Cabral C , Lavoie C , M. Harper J
Published: July 2020

Titanium disilicide (C54-TiSi2) is a low resistivity silicide (15 - 20 μΩ-cm) and is widely used in the device industry. It is formed at about 750-850 °C when thin layers (∽30- lOOnm) of Ti on poly- or single-crystal Si substrates are subjected to rapid thermal annealing (3 °C/sec) in a controlled atmosphere (N2). During the anneal, other Ti silicides such as Ti5Si3, Ti5Si4,TiSi and C49-TiSi2 may form prior to the desirable C54-TiSi2.

Some attempts have been made to promote low-temperature C54-TiSi2 formation. Depositing a Mo (l-2nm) interlayer between Ti and Si has been reported to decrease the C54 formation temperature by 100 °C.2 Codepositing Ti with Ta, Nb or Mo has successfully decreased the formation temperature by about 150 °C.3 These findings have been interpreted in terms of a template mechanism which facilitates formation of C54 by advantageous lattice matching between similar planes in C54 and a hexagonal ternary (Ti- X-Si, X=Ta, Nb, Mo) C40 precursor phase.
Crystallographical Analysis of Intermediate Phases in BI(2223)/AG Tape
Authors: Wu Lijun , Zhu Yimei , Suenaga M
Published: July 2020

(Bi,Pb)2Sr2Ca2Cu3Ox/Ag composite tapes are currently the most promising high-temperature superconductors for large-scale applications. A major issue in further improving the supercurrent-carrying-capability and optimizing fabrication procedures of these tapes is to understand the formation kinetics of the Bi(2223) from precursor powders of Bi(2212), CaO, and CuO. Since the microstructural transformation during the complicated phase evolution is not well known yet, identification of minor phases at different transformation stage is desirable. Here, we report our crystallographic analysis of several frequently observed intermediate phases during the phase evolution.

The heat treatment of the tapes consisted of ramping the temperature to 840°C in air and of holding it for a prescribed period and then oil-quenching from various temperatures.
Oxide Structures: By Hook Or by Crook
Authors: Marks L D , Sinkler W , Zhang H
Published: July 2020

Sometimes oxides are friendly; x-ray or neutron diffraction solves the structure and (at most) simple HREM does a double check. Sometimes they are not. Problems can range from phase purity (identifiable using EDX) to more subtle issues about the true unit cell and/or atom locations. The latter are often particularaly hard for x-ray or neutron to handle when single crystal data is not available and, for instance, the samples are polyphase or textured.

One common problem is that the unit cell is rather larger than originally thought due to a superstructure. While superstructure reflections may be obvious in the microscope due to the very large dynamic range of TED patterns, they may not show in powder patterns. The issue then is to determine the true structure using (often) a combination of HREM and TED plus multislice simulations to confirm the structure.
Study of the Hole Distribution in Oxide Superconductors Using a Sensitive Electron Diffraction Technique
Authors: Tafto J , Wu Lijun , Zhu Yimei
Published: July 2020

A key towards understanding the properties of high-temperature superconductors is knowledge about the distribution of the valence electrons and holes. Despite their complicated crystal structure, electronic structure of many cuprates has been calculated. The most successful calculation method is based on the theorem that the ground state energy is a unique functional of the electron density. Thus, experimental techniques that give information about the valence electron density are essential to test the calculations and to gain further insight into these important materials.

To move beyond locating the atoms in the crystal unit cell towards addressing the details of the electron distribution requires in general extremely accurate diffraction experiments. Highly perfect crystals with small unit cells have been approached. It has been known for several decades that in electron diffraction the amplitudes of those reflections at small scattering angles that are present in crystals with large unit cells, are strongly influenced by the valence electron distribution.
The Electronic Structure and Bonding of Copper Oxides by CBED and EELS
Authors: Kim M Y , Alvarez J , Zuo J M , Spence J C H
Published: July 2020

Cu2O and CuO are of great interest after the discovery of the high Tc superconductors. The superconductivity is believed to be dependent on charge states in CuO2 layers whose structure is similar to that of CuO. These transition-metal compounds are also important because of the different copper coordination numbers and different copper-oxygen distances, therefore these reflect different electron density distributions and bonding mechanisms. The electronic structure of cuprite has been studied extensively both theoretically and experimentally because of its symmetrical crystallographic structure (space group ) while that of CuO (space group C2/c) which has a monoclinic structure has been studied only recently. Previous experimental and theoretical results show that the valence electrons of copper in cuprite form hybrid states which is proposed by Orgel instead of spherical d10 state as in ionic copper.