bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron diffraction studies of long-range order in AlxGa1-xAs
Authors: Kuan T. S.
Published: June 2020

We have recently found by electron diffraction that Ga and Al atoms can form an ordered sublattice during a continuous and uniform growth of AlxGa1-xAs thin crystals. Such long-range order has never before been observed in any III-V semiconductor alloys. Important questions are thus raised concerning the equilibrium phase of that system and the stability of certain types of artificially grown superlattice structures. The long-range order was found in thin layers of AlxGa1-xAs (with 0.15 ≤ x ≤ 0.80) grown epitaxially on GaAs substrates using metal-organic vapor-phase epitaxy (MOVPE) or molecular beam epitaxy (MBE) techniques under a range of growth temperatures and employing certain substrate orientations. The ordered state is reached during a continuous co-deposition of Al, Ga, and As at high temperatures without any artificial imposition of special growth sequences. It is thus likely that the ordered structure may represent an equilibrium and thermodynamically stable state.
Hrem of metal/metal multilayer materials
Authors: Petford-Long A.K. , Chang C.-H , Stearns M.B. , Kadin M.A.
Published: June 2020

Multilayered structures (MLS) containing thin (<10nm) metallic layers of W or Mo with C or Si are undergoing development for use as x-ray reflectors and other x-ray optical elements. The two metals used are sputtered or evaporated in alternate layers onto a crystalline Si substrate (eg. [2]). The x-ray reflectance properties of these materials have been extensively studied, but until recently only indirect structural evidence has been available to allow a correlation between reflectance and structure to be made. A JEM 4000EX ultra-high resolution electron microscope has been used in this study to image the MLS and provide direct structural information.
Characterization of Si(Li) x-ray detector efficiencies in the low energy range
Authors: Wirmark G. , Wahlberg G. , Nordén H.
Published: June 2020

X-ray microanalysis with windowless or ultra-thin window Si(Li)-detectors is becoming increasingly important in analytical electron microscopy. The most common approach in the quantification of this method is the thin film ratio method.

where CA and CB denote the concentrations of elements A and B respectively and IA and IB are the corresponding x-ray intensities. The KAB-factor should ideally be determined from analyses of standard specimens of known compositions.
Measurement of the absolute thickness of metallic specimens
Authors: Cheng S. C. , Egerton R. F.
Published: June 2020

Several procedures are available for determining the local thickness of a TEM specimen. However, these existing methods tend to be either imprecise or time-consuming, while some of them require knowlege of the chemical composition of the specimen. We discuss here a technique involving electron energyloss spectroscopy (EELS) which appears to be capable of better than 10% accuracy (see Fig. 1 and Table 1) and which, for a metallic specimen, requires no knowledge of the physical or chemical properties.
Dislocation and solid-phase epitaxial growth microstructure control by Ar+ implantation for gettering in semiconductors
Authors: Smith P. , Narayan J.
Published: June 2020

Gettering of undesirable impurities from the junctions or the electrically active regions improves electrical characteristics of semiconductor devices. This removal of impurities can be accomplished either by point defects or more efficiently by line defects such as dislocations and small-angle grain boundaries. The small-angle grain boundaries containing arrays of dislocations constitute two-dimensional defects which are more effective in removing the impurities. This removal of undesirable impurities involves dislocation - impurity interaction and subsequent segregation of impurities at the dislocations. The gettering efficiency of dislocations is determined by the nature of dislocations and also by the stability of dislocation network against annealing. In previous studies, it has been shown Ar+ implantation damage is very effective in gettering undesireable impurities. However, the mechanisms of enhanced gettering by Ar+ ion damage were not clear. The purpose of this investigation was to explore the mechanism of enhanced gettering by Ar+ damage and charaterize the Ar+ damage as a function of annealing treatments.
Aspects of high-resolution imaging with a scanning ion microprobe
Authors: Levi-Setti R. , Chabala J. M. , Wang Y. L.
Published: June 2020

We have shown the feasibility of 20 nm lateral resolution in both topographic and elemental imaging using probes of this size from a liquid metal ion source (LMIS) scanning ion microprobe (SIM). This performance, which approaches the intrinsic resolution limits of secondary ion mass spectrometry (SIMS), was attained by limiting the size of the beam defining aperture (5μm) to subtend a semiangle at the source of 0.16 mr. The ensuing probe current, in our chromatic-aberration limited optical system, was 1.6 pA with Ga+ or In+ sources. Although unique applications of such low current probes have been demonstrated,) the stringent alignment requirements which they imposed made their routine use impractical. For instance, the occasional tendency of the LMIS to shift its emission pattern caused severe misalignment problems.
Fractionation of polymethylene chains: An electron crystallographic investigation
Authors: Dorset Douglas L.
Published: June 2020

A variety of linear chain materials exist as polydisperse systems which are difficultly purified. The stability of continuous binary solid solutions assume that the Gibbs free energy of the solution is lower than that of either crystal component, a condition which includes such factors as relative molecular sizes and shapes and perhaps the symmetry of the pure component crystal structures.

Although extensive studies of n-alkane miscibility have been carried out via powder X-ray diffraction of bulk samples we have begun to examine binary systems as single crystals, taking advantage of the well-known enhanced scattering cross section of matter for electrons and also the favorable projection of a paraffin crystal structure posited by epitaxial crystallization of such samples on organic substrates such as benzoic acid.
Structure and function of the neuronal endomembrane system
Authors: Martone Maryann E. , Simpliciano Victoria M. , Zhang Ying , Deerinck Thomas J. , Ellisman Mark H.
Published: June 2020

Components of the endomembrane system in a variety of cell types appear to function in the storage and release of calcium similar to the muscle sarcoplasmic reticulum. Many proteins involved in intracellular calcium regulation in skeletal or smooth muscle, e.g. Ca++ ATPase, calsequestrin, the inositol l,4,5,trisphosphate (TP3) receptor and the ryanodine binding protein, are found in the nervous system where they are particularly abundant within the smooth endoplasmic reticulum (SER) of cerebellar Purkinje neurons. Immunolocalization studies suggest, however, that calcium regulatory proteins are not uniformly distributed within the SER but are concentrated in or excluded from certain domains. For example, the IP3 and ryanodine receptors, two distinct calcium channels which mediate calcium release by different ligands, are found associated with the SER in cell bodies and dendrites of chick cerebellum but only the IP3 receptor is found within dendritic spines. These results are consistent with evidence that cells may possess multiple intracellular calcium stores that are pharmacologically, spatially and perhaps physically distinct.
Dual stain kit for the microscopic gram classification of ocular infection bacteria
Authors: Hanker Jacob S. , Holdren Dale N. , Cohen Kenneth L. , Giammara Beverly L.
Published: June 2020

Keratitis and conjunctivitis (infections of the cornea or conjunctiva) are ocular infections caused by various bacteria, fungi, viruses or parasites; bacteria, however, are usually prominent. Systemic conditions such as alcoholism, diabetes, debilitating disease, AIDS and immunosuppressive therapy can lead to increased susceptibility but trauma and contact lens use are very important factors. Gram-negative bacteria are most frequently cultured in these situations andPseudomonas aeruginosais most usually isolated from culture-positive ulcers of patients using contact lenses. Smears for staining can be obtained with a special swab or spatula and Gram staining frequently guides choice of a therapeutic rinse prior to the report of the culture results upon which specific antibiotic therapy is based. In some cases staining of the direct smear may be diagnostic in situations where the culture will not grow. In these cases different types of stains occasionally assist in guiding therapy.
MTF restoration with slow-scan CCD cameras
Authors: Mooney P.E. , de Ruijter W.J. , Krivanek O.L.
Published: June 2020

Slow-scan CCD cameras (SSCs) attached to transmission electron microscopes (TEMs) are proving invaluable in the acquisition of TEM images and in providing high quality data for on-line analysis and autotuning procedures. When equipped with a sensitive phosphor and an efficient fiber-optical coupling, they are able to record the arrival of single fast electrons. At more typical exposure levels of 10 -1000 fast electrons per pixel, they are able to capture images while adding less noise than the Poisson noise inherent in any electron image.

The raw images captured by the SSC suffer from various defects, but these can be corrected on-line in the computer used to record the images. The most familiar defect is the pixel-to-pixel gain variation, which is readily corrected by capturing a gain-reference image and then performing on-line gain-normalization. Another significant defect in raw images is that the signal due to each arriving electron is spread overseveral pixels.
Effect of matrigel on development of A549 lung epithelial cells
Authors: Kress Yvonne , Bloom Barry R. , McDonough Kathleen A.
Published: June 2020

Extracellular matrix components are known to influence the growth and differentiation of cultured cells, often causing them to behave more like their in vivo counterparts than cells grown on plastic. To develop an in vitro model in which to study the interaction of pathogenic microorganisms with the lung epithelium, we have undertaken a morphological study of the effects of extracellular matrix components on the human lung alveolar epithelial cell line A549. A549 cells were grown for varying amounts of time on plastic; Costar polycarbonate membrane filter inserts; or on Matrigel coated polycarbonate filter inserts. Cells were fixed for 1 h in 2% glutaraldehyde in 0.1 M cacodylate buffer, post-fixed in 1 % OsO4 for 45 min, dehydrated in ascending ethanol, and embedded in Spurr’s resin.

A549 cells grown on a plastic slide formed an even monolayer with cells connected by wellformed junctional complexes or separated by interdigitating microvilli. The cytoplasm showed many polyribosomes, rough endoplasmic reticulum, small golgi complexes, mitochondria, occasional lysosomes and bundles of microfilaments.
Chemically induced accumulation of phospholipids in canine organ systems
Authors: Maleeff Beverly E. , Kircher Charles H. , Badger Alison M. , Hart Timothy K. , Bugelski Peter J.
Published: June 2020

Cationic amphiphilic drugs (CAD) are structurally characterized by their hydrophobic ring structure and hydrophilic side chain. Studies have shown that over 30 CADs with various pharmacological activities have the ability to induce phospholipid-like inclusions in peripheral blood cells and in organs such as lung, liver and spleen. SK&F 105685 is a novel cationic amphiphilic compound with immunomodulatory activity. It induces immune suppressor cell activity in many species. The purpose of this study was to determine if this compound induces cytoplasmic phospholipid inclusions in dogs.

Heparinized blood samples were collected from male and female dogs after 14 and 85 days of treatment. Buffy coats were prepared and fixed with 2.5% glutaraldehyde - 2.0% paraformaldehyde with 50 μM CaCl2 in 0.1 M cacodylate buffer, pH 7.2. The pellets were processed to epoxy resin. Tissues from all organs were collected at necropsy in buffered formalin following 30 or 90 days of treatment, and processed for histopathologic evaluation.
Effects of low-temperature heating on the morphology of birch wood
Authors: Fisher Robert M. , Reine Barbara A.
Published: June 2020

The effects of heating wood have been studied for many years with much of the work focused on the curing, ignition, extraction of gaseous and liquid by-products, production of charcoal and, of course, high temperature oxidation, i.e. combustion. Research techniques include bulk weight-loss studies or differential gravimetric analysis (DTA), analyses of the evolution of a wide variety of C-O-H organic compounds by gas chromatography and mass spectroscopy, observing critical times and temperatures for piloted and smoldering ignition, analyses of heat energy absorption and release using Differential Thermal Analysis (DTA) and measurement of the caloric value of firewood and charcoal. Optical microscopy has been used in support of these studies but surprisingly little electron microscopy has been carried out.

The stimulus for this research was curiosity about structural changes during long term heating of wood that increase its' susceptibility to spontaneous, i.e., smoldering combustion. The literature on fire origin investigations contains numerous references to cases where fires were believed to have resulted from spontaneous ignition of structural wood members after years of exposure to steam heating pipes.
Strained-layer Van Der Waals epitaxy in a Langmuir-Blodgett film
Authors: Viswanathan Ravi
Published: June 2020

Langmuir-Blodgett (LB) films are layered structures of amphiphilic molecules which are assembled by successive deposition on a solid substrate from a monolayer at the air water interface. Most of the potential applications of LB films (molecular electronics, cell membrane models, biosensors) are based on the premise of perfect molecular layering and orientation. The technique of atomic force microscopy (AFM), which probes only the outermost layer of the film, has opened up the study of the surfaces of these films which occupy a unique position at the intersection of surface science and complex fluids. We show here that the growth of lead stearate (PbSt) LB films on mica substrates proceeds by a new type of epitaxy which we call “strained layer van der Waals epitaxy” because it represents a compromise between the mechanisms of strained-layer epitaxy and van der Waals epitaxy.

The PbSt films were prepared with the standard Langmuir-Blodgett vertical dipping method and imaged with the AFM in air at ambient temperature.
Image analysis: From pixels to data
Authors: Russ John C.
Published: June 2020

This meeting is about microscopy, which deals with images, and this special session is specifically concerned with the methods for interpretation of those images. It should not be necessary to preach to such an audience about the need for appropriate tools for performing quantitative measurements to extract numeric information from images. Most of these tools are based on the ready availability of computers and peripherals which allow the acquisition, storage, processing, measurement and interpretation of the data. Provided we can also teach the scientist to ask the right questions and correctly use the results, image analysis can offer a powerful tool for the understanding of structure. Since most of this structure is threedimensional, whereas images are essentially two-dimensional, there is need for stereological interpretation, and for the construction of 3D visualization from multiple images. These are dealt with in subsequent papers in this session. This talk is primarily an introduction to the basics of computer-based image analysis - the tools for obtaining information from images, or “data from pixels.”
High-spatial-resolution x-ray microanalysis: Comparison of experiment and incoherent scattering calculations
Authors: Michael J. R. , Romig A. D.
Published: June 2020

There have been many experimental efforts to measure the spatial resolution for x-ray microanalysis in the analytical electron microscope (AEM). There have been three commonly utilized specimen geometries in these experiments: 1) segregant at a grain boundary, 2) interphase boundaries oriented parallel to the electron beam, and most recently 3) spherical particles embedded at various depths in thin foils. The results of many of these experiments have been analyzed with a number of models for the broadening of the electron beam as it traverses the thin foil. These models are typically based on incoherent electron scattering, typical of Monte Carlo simulations. A vast majority of the published spatial resolution data support the incoherent scattering models as the best simulation of spatial resolution for x-ray microanalysis in the AEM. Recent experimental work using embedded particles to measure beam broadening has been used to support the coherent scattering model of beam broadening.
Tacky dot arrays for ordered particle mounting
Authors: Cairncross Allan , Flaherty David M. , Klabunde Ulrich
Published: June 2020

We describe for the first time a rapid way to mount particles on regularly spaced centers for microscopic examination. This innovative method mounts particles in ordered arrays rather than the random chaos of usual methods and therefore simplifies particle examination, identification and analysis. Advantages include the ability to easily mount single particles in controlled patterns and known locations, to mount tight clusters of 2 or more particles per center (Fig. 3); to repeatedly mount the same pattern/number of particles; to mount particles in unusual orientations (Fig. 5, 6) and to easily get the average weight of single particles. Examples of applications include mounting and examination of ores (Fig. 1), pollens (Fig. 2, 3), milled products, seeds (Fig. 4) and crystalline products(Fig. 5, 6).

The mounting medium consists of a pattern of fine adhesive centers typically on 1 by 3 inch glass slides or on clear plastic film that is easily cut to any size or shape.
Nanometer-resolution Auger electron spectroscopy and microscopy of small particles
Authors: LIU JINGYUE
Published: June 2020

Small metal particles have peculiar physical and chemical properties and they are especially important in catalysis. A detailed understanding of catalytic processes requires knowledge of both the microstructure and the microchemistry of the catalyst system. Although nanometer scale surface topography of supported catalysts can be studied with secondary electron (SE) signals, a chemically specific and surface sensitive signal such as Auger electrons must be used to extract compositional information about the surface species. Auger electron (AE) spectroscopy (AES) and scanning Auger microscopy (SAM) have been widely used for surface and catalyst characterization. In order to observe the active phases (small particles) of supported catalysts, it is necessary, however, to have nanometer scale resolution in SAM images.

With significant improvement in detection efficiency of low energy secondary electrons by employing magnetic parallelizers in our UHV scanning transmission electron microscope (STEM), known as MIDAS (a Microscope for Imaging, Diffraction and Analysis of Surfaces), a spatial resolution of approximately 3 nm in SAM images has been achieved on bulk samples.
Impurity gettering in rapidly solidified advanced steels
Authors: Ghosh G. , Olson G. B.
Published: June 2020

It is well known that gettering of the elements responsible for intergranular stress-corrosion cracking (SCC), such as P and S, leads to significant improvement in resistance to SCC in ultrahigh-strength (UHS) steels. Using rapid solidification processing (RSP) and with the addition various impurity getteres, such La, Ti and Zr, it is possible to obtain very fine dispersion of various phases. Formation of very stable P- and S-bearing compounds not only improves SCC but also provide grain coarsening resistance during high temperature consolidation/austenization treatments. In a recent study of La gettered Ni-Mo steels, highly stable fine dispersions of LaPO4 and La2O2S were claimed to have been observed. But, the major drawback was that the structure of these phases and quantitative estimate of any stoichiometry were not carried out. Furthermore, above experiment was done using thin foils which are certainly not suitable for making any kind of quantitative estimate involving light elements.
Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs
Authors: Anderson David M. , Landh Tomas
Published: June 2020

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.

The study of these structures has become of increasing importance in the past five years for two reasons:

1)

Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and

2)

Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.
Light microscopy of ceramics
Authors: McCrone Walter C.
Published: June 2020

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).
Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC
Authors: Bow J.S. , Carpenter R.W. , Kim M.J.
Published: June 2020

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.
Morphology of Acid-Cleaned Heat-Treated MgO (100) Surfaces
Authors: King Simon , Barry Carter C.
Published: June 2020

The widespread use of the (100) MgO surface as a substrate for the deposition particularly of high-Tc super-conductors, and a wide variety of other materials such as titania, has provoked considerable interest in the morphology of the surfaces employed. In the above studies, (100) oriented MgO specimens have generally been prepared according to the method of Norton et al, in which foils are cleaned in acid, with the active ingredient being aqua-regia, after perforation by ion-milling and before a heat treatment in air, typically for 10-15 mins at 1350 °C. The surface morphology of specimens prepared in this manner is explored in this paper.

Many of the features common to the aqua-regia cleaned and heat-treated thin-films are shown in the (100) zone-axis bright-field (BF) image of fig 1(a). The general morphology of these foils includes a high density of holes within the thinnest regions, whilst pores are in evidence in thicker areas.
The effects of small crystal tilts on dynamical scattering: why simulated images are thinner than experimental ones
Authors: O’Keefe Michael A. , Radmilovic Velimir
Published: June 2020

It is now well-established that high-resolution transmission electron microscope image simulation can accurately reproduce experimental HRTEM images when imaging parameters are accurately known. These parameters include specimen properties such as unit cell structure, crystal orientation, and specimen thickness, as well as microscope parameters such as beam energy and coherence (both spatial and temporal), objective aperture size, and objective lens defocus and spherical aberration. Of these parameters, the most difficult to measure, and thus to include accurately, is the specimen thickness (and also the temporal coherence; on the other hand, although spatial coherence is easily measured, its effects are not always accurately included in all simulations). In many investigations that utilize matches between experimental and simulated HRTEM images, specimen thickness is treated as a disposable parameter; i.e. the experimental specimen thickness is not measured, but assigned to be the thickness that was used in the simulation program to produce the simulated image that best matched the experimental one.
Electron holography with a CM30-FEG-special-Tübingen Microscope
Authors: Lichte Hannes
Published: June 2020

Electron holography offers the advantage over conventional microscopy that full use of the object information can be made especially if numerical reconstruction is applied: By coherent optical coupling of a computer to the electron microscope, the electron object wave is completely available for a very flexible wave optical analysis. For example, besides the correction of the coherent aberrations (e.g. spherical aberration, defocus and astigmatism) and the unique accessability of both amplitude and phase of the object wave in real space and in Fourier space, techniques like nanodiffraction or Selective Imaging can be used to improve our knowledge about the object structure at atomic dimensions.

However, there are limits imposed on this scheme by the restrictions given by todays technology for the two steps of data acqusition and processing, i.e taking the hologram and reconstructing the wave.

First, the information collected in a hologram is limited by incoherent effects.
HRTEM Image of Twin Structure in Nanocrystalline Platinum
Authors: Lin Hong-Ming , Hsu Chi-Ming , Huang Ching-Shung , Lay Ming-Shyong , Lee Pee-Yew
Published: June 2020

This paper presents recent result on the observation of microstructure of nanocrystalline platinum. Nanocrystalline powders of Pt are made by gas condensation method, and examined by using TEM and HRTEM. Twin structure is found first within the individual particle of as evaporated nanophase Pt particles which form twin during the nucleation and growth of particle. Twin also appears while neck growth take place during the sintering of as evaporated pt with Al2O3. The formation of these twins during sintering was due to the fact that the neck growth will induce a tensile stress which is high enough to pull the nanocrystalline powders to form twin structure. Twin plane of nanophase sintering Pt powder was identified by using the Fourier transformation as {111} plane. It is the same as usually found in fcc bulk materials.

The pure nanocrystalline Pt particles with a diameter less than 100 nm had been produced by the gas evaporation in helium atmosphere.
Growth kinetics of Al2Cu in an Al-1.5Cu thin film by in Situ TEM
Authors: Park M. , Krause S.J. , Wilson S.R.
Published: June 2020

Cu alloying in Al interconnection lines on semiconductor chips improves their resistance to electromigration and hillock growth. Excess Cu in Al can result in the formation of Cu-rich Al2Cu (θ) precipitates. These precipitates can significantly increase corrosion susceptibility due to the galvanic action between the θ-phase and the adjacent Cu-depleted matrix. The size and distribution of the θ-phase are also closely related to the film susceptibility to electromigration voiding. Thus, an important issue is the precipitation phenomena which occur during thermal device processing steps. In bulk alloys, it was found that the θ precipitates can grow via the grain boundary “collector plate mechanism” at rates far greater than allowed by volume diffusion. In a thin film, however, one might expect that the growth rate of a θ precipitate might be altered by interfacial diffusion. In this work, we report on the growth (lengthening) kinetics of the θ-phase in Al-Cu thin films as examined by in-situ isothermal aging in transmission electron microscopy (TEM).
User-friendly field emission
Authors: Crewe Albert V. , Clayton Deborah L. , Crewe David A. , Moscicka Katarzyna
Published: June 2020

We introduced the field emission source into electron microscopy twenty five years ago but in spite of the obvious advantages of such a source it was not an instant success. In fact it is only in recent years that the use of field emission has become significant, and even now it is only for high performance, high cost instruments.

The reasons for customer resistance are not hard to find. Firs t there is the need for a UHV system, a necessity which brings with it a significant increase in cost and also the need for new expertise and training since UHV systems use different hardware and different maintenance procedures.

Next there is the need for knowledge and experience with field emission and its peculiar characteristics. Tips need to be “flashed” and the operator needs to be able to recognize the symptoms which signal that need.
Image processing to delineate defect structures in HREM images of vapor-deposited thin films
Authors: Fisher R.M. , Duan J.Z. , Hetherington Crispin J. , Fowler Norman
Published: June 2020

The resistance of deposited thin films to cracking or delamination from substrates during production or service, crucial to the long term reliability of IC devices, is under study as part of a broad program on interfacial bonding and adhesion. Chromium films, of particular interest because of their widespread use in microelectronics, are especially prone to mechanical failure due to the high residual stresses that are generally present and their low fracture toughness. Transmission and scanning electron microscopy are being used to define the columnar grain structure and failure modes and x-ray diffraction is being employed to determine the nature of through-thickness stress gradients that occur in such films.

The intrinsic stress, as distinguished from the extrinsic stress caused by differential contraction between film and substrate during cooling from the deposition temperature, results from the presence of vacancies and diffuse “voids” trapped between the columns during deposition. Transmission electron microscopy of plan-view and cross-sections is being used in efforts to observe and define the structure of the inter-columnar regions.
Superconductivities and structure modulations in Tl-Ba-Ca-Cu-O oxides
Authors: Iijima Sumio
Published: June 2020

Charge carrier sources for the superconductivities of high Tc oxides have been sought by various techniques. The role of lattice defects in the superconductivity, and structural defects which are common in these oxides, were investigated by electron microscopists. In this paper, microstructures on TBCCO oxide crystals, in particular, superlattice modulations in the 2201 phase, and Y-doped 2212 phases which are prepared under various growth conditions, are presented. All specimens were prepared in the standard sintering method.

In contrast with the 2212 and 2223 compounds, the 2201 compounds showed a wide range of Tc values. Their variations were found to be strongly affected by oxygen content.This was concluded from the fact that the nonsuperconductive specimen became conductive by quenching after heating in O2 atmosphere at 400°C. This was further confirmed when the superconductivity vanished by annealing. It was also demonstrated that crystal symmetries of the compounds, orthorhombic and tetragona1 are not directly related to the superconductivity as was proposed by Hewat et al. The orthorhombic structures are obtained at preparation temperatures above 840°C. It was also found that the Tc value increases linearly with an increase in the c-axis length which is independent of crystal structures.
Microstructural characterization of YBaCuO Films on LaAlO3 substrates
Authors: Hall E. L. , Mogro-Campero A. , Lewis N. , Turner L. G.
Published: June 2020

There have been a large number of recent studies of the growth of Y-Ba-Cu-O thin films, and these studies have employed a variety of substrates and growth techniques. To date, the highest values of Tc and Jc have been found for films grown by sputtering or coevaporation on single-crystal SrTiO3 substrates, which produces a uniaxially-aligned film with the YBa2Cu3Ox c-axis normal to the film plane. Multilayer growth of films on the same substrate produces a triaxially-aligned film (regions of the film have their c-axis parallel to each of the three substrate <100> directions) with lower values of Jc. Growth of films on a variety of other polycrystalline or amorphous substrates produces randomly-oriented polycrystalline films with low Jc. Although single-crystal SrTiO3 thus produces the best results, this substrate material has a number of undesireable characteristics relative to electronic applications, including very high dielectric constant and a high loss tangent at microwave frequencies. Recently, Simon et al. have shown that LaAlO3 could be used as a substrate for YBaCuO film growth. This substrate is essentially a cubic perovskite with a lattice parameter of 0.3792nm (it has a slight rhombohedral distortion at room temperature) and this material exhibits much lower dielectric constant and microwave loss tangents than SrTiO3. It is also interesting from a film growth standpoint since it has a slightly smaller lattice parameter than YBa2Cu3Ox (a=0.382nm, b=c/3=0.389nm), while SrTiO3 is slightly larger (a=0.3905nm).
Epitaxial growth of yBa2Cu3O7-x films on Si substrates with buffer layers
Authors: Hwang D. M. , Ramesh R. , Wu X. D. , Inam A. , Hegde M. S. , Wilkens B. , Chang C. C. , Nazar L. , Venkatesan T. , Miura S. , Matsubara S. , Miyasaka Y. , Shohata N.
Published: June 2020

Several groups have prepared nearly-single-crystalline YBa2Cu3O7-X thin films on SrTiO3 substrates with critical temperatures of zero resistivity (Tα) exceeding 90 K and critical current densities at 77 K (Jc,77k) exceeding 106 A/cm2. However, films prepared on Si substrates, either directly or with buffer layers, are usually polycrystalline and with much lower Tα and Jc. Recently, much-improved YBa2Cu3O7-X thin films have been prepared on Si substrates with double buffer layers, BaTiO3 and MgAl2O4. Miura et al. prepared the films by rf magnetron sputtering at 640°C substrate holder temperature and their best as-deposited film exhibits Tα = 70 K and Jc,40k = 4 × 104 A/cm2. Wu et al. prepared the films by pulsed laser deposition at 650°C substrate holder temperature and their best film exhibits Tα = 87 K and Jc,77K = 6 × 104 A/cm2. X-ray diffraction studies indicated that the films are orientationally locked with the Si substrates. Here we present the transmission electron microscopy (TEM) analysis of the laser deposited films and show the epitaxial relations between the buffer layers and the Si substrates, as well as between the YBa2Cu3O7-X flims and the buffer layers. Defect generating mechanisms and possibilities for improving the crystalline properties of the YBa2Cu3O7-X films, and consequently the superconducting properties, will be discussed.
The analysis of “Gels” in polymer films
Authors: Brown G. M. , Brown D. F. , Butler J. H.
Published: June 2020

The term “gel”, in the jargon of the plastics film industry, may refer to any inclusion that produces a visible artifact in a polymeric film. Although they can occur in any plastic product, gels are a principle concern in films where they detract from the cosmetic appearance of the product and may compromise its mechanical strength by acting as local stress concentrators. Many film gels are small spheres or ellipsoids less than one millimeter in diameter whereas other gels are fusiform-shaped and may reach several centimeters in length. The actual composition of gel inclusions may vary from miscellaneous inorganics (i.e. glass and mineral particles) and processing additives to heavily oxidized, charred or crosslinked polymer. The most commonly observed gels contain polymer differing from the bulk of the sample in its melt viscosity, density or molecular weight.

Polymeric gels are a special concern in polyethylene films. Over the years and with the examination of a variety of these samples three predominant polymeric species have been observed: density gels which have different crystallinity than the film; melt-index gels in which the molecular weight is different than the film and crosslinked gels which are comprised of crosslinked polyethylene.
Surface oxygen artifacts on aluminum nitride
Authors: Callahan Daniel L.
Published: June 2020

Aluminum nitride (AlN)is an increasingly important electronic ceramic with oxygen as an important bulk impurity. Quantitative microanalysis of oxygen to determine its precise distribution is a necessary step in characterization of the ceramic that may be complicated due to surface oxidation. AlN is thermodynamically unstable compared to the oxide (Al2O3) at room temperature in the presence of environmental oxygen or water and may thus be expected to form a thin, possibly passive oxide film similar to the oxide layer of pure aluminum metal. Such an oxide layer has been used to explain anomalies in oxygen quantification in AlN by neutron activation methods [1] but reflecteion high energy electron diffraction studies [2] failed to reveal either crystalline or amorphous oxide phases forming at room temperature.

Electron diffraction techniques in the transmission electron microscope were used to examine thin AlN sections for possiblecrystalline surface layers. A ceramic AlN sample was prepared using conventional techniques for the preparation of thin foils with final thinning accomplished by ion milling.
Microscopy of porous ceramics
Authors: Kerch H. M. , Gerhardt R. A.
Published: June 2020

Highly porous ceramics are employed in a variety of engineering applications due to their unique mechanical, optical, and electrical characteristics. In order to achieve proper design and function, information about the pore structure must be obtained. Parameters of importance include pore size, pore volume, and size distribution, as well as pore texture and geometry. A quantitative determination of these features for high porosity materials by a microscopic technique is usually not done because artifacts introduced by either the sample preparation method or the image forming process of the microscope make interpretation difficult.

Scanning electron microscopy for both fractured and polished surfaces has been utilized extensively for examining pore structures. However, there is uncertainty in distinguishing between topography and pores for the fractured specimen and sample pullout obscures the true morphology for samples that are polished. In addition, very small pores (nm range) cannot be resolved in the S.E.M. On the other hand, T.E.M. has better resolution but the specimen preparation methods involved such as powder dispersion, ion milling, and chemical etching may incur problems ranging from preferential widening of pores to partial or complete destruction of the pore network.
Microdiffraction and convergent-beam diffraction from surfaces
Authors: Eades J. A.
Published: June 2020

Microdiffraction from surfaces at near grazing incidence is an important method of surface characterization. It is very much akin to RHEED (reflection high-energy electron diffraction) except that in RHEED a large area of sample (∼ 1 mm2) contributes to the diffraction. In this respect the relationship between RHEED and surface microdiffraction is analogous to that between selected-area diffraction and microdiffraction in transmission. In addition RHEED systems usually have no post-specimen lenses and therefore operate at a fixed camera length.

Surface microdiffraction can contribute important information for the characterization of surfaces but there are some important factors that make it more complex than in the case of convergent-beam diffraction in transmission.

At grazing incidence, even with high-energy electrons, refraction at the surface is important -whereas in transmission (at near-normal incidence) it may be neglected.
HREM observation of NiO growth on submicron spheres of pure nickel
Authors: Teng C.M. , Kelly T.F. , Zhang J.P. , Lin H.M. , Kim Y.W.
Published: June 2020

Spherical submicron particles of materials produced by electrohydrodynamic (EHD) atomization have been used to study a variety of materials processes including nucleation of alternative crystallization phases in iron-nickel and nickel-chromium alloys, amorphous solidification in submicron droplets of pure metals, and quasi-crystal formation in nickel-chromium alloys. Some experiments on pure nickel, nickel oxide single crystals, the nickel/nickel(II) oxide interface, and grain boundaries in nickel monoxide have been performed by STEM. For these latter studies, HREM is the most direct approach to obtain particle crystal structures at the atomic level. Grain boundaries in nickel oxide have also been investigated by HREM. In this paper, we present preliminary results of HREM observations of NiO growth on submicron spheres of pure nickel.

Small particles of pure nickel were prepared by EHD atomization. For the study of pure nickel, 0.5 mm diameter pure nickel wire (99.9975%) is sprayed directly in the EHD process. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-7 torr.
The effect of an aluminum heat-sink layer on the laser-induced amorphization of SiOx/TeGeSn/SiOx phase-change recording films
Authors: Libera Matthew R. , Chen Martin
Published: June 2020

Phase-change erasable optical storage is based on the ability to switch a micron-sized region of a thin film between the crystalline and amorphous states using a diffraction-limited laser as a heat source. A bit of information can be represented as an amorphous spot on a crystalline background, and the two states can be optically identified by their different reflectivities. In a typical multilayer thin-film structure the active (storage) layer is sandwiched between one or more dielectric layers. The dielectric layers provide physical containment and act as a heat sink. A viable phase-change medium must be able to quench to the glassy phase after melting, and this requires proper tailoring of the thermal properties of the multilayer film. The present research studies one particular multilayer structure and shows the effect of an additional aluminum layer on the glass-forming ability.
Formation and stability of {113} defects in oxygen implanted silicon-on-insulator material
Authors: Ravi T.S. , Jung C.O. , Burke D.E. , Krause S.J.
Published: June 2020

High dose oxygen implantation into Si (SIMOX – Separation by Implantation of Oxygen) is a viable technique for producing silicon-on-insulator structures. The {113} defect was first observed in SIMOX by van Ommen. It has received considerable study in bulk Si. Bergholz et al. proposed that {113} defects are coesite, a high pressure monoclinic phase of silica, and are a possible precursor to amorphous silicon oxide. Recently Bourrel proposed a self-interstitial model for the formation of hexagonal silicon in the {113} planes in the diamond cubic lattice which was an extension of Tan's model and suggested that oxygen is generally not required for the creation of {113} defects. In this paper we have examined the formation and stability of {113} defects in as-implanted and annealed SIMOX.

The first set of samples studied was implanted to 2.4×1018 cm-2 at 200 keV from 400°C to 600°C. The second set was implanted at 150 keV to 2.0×1018 cm-2 at 500°C. Five equivalent parts of the wafer were annealed from 650°C to 1050°C in steps of l00°C for two hours in Ar. Cross-section samples were made by gluing, grinding, dimpling and ion milling of the wafer chips.
In situ studies of deformation at interfaces
Authors: Clark William A. T.
Published: June 2020

During the last twenty-five years there have been a number of studies of dislocation motion and interactions performed in the electron microscope. In general these observations have been limited by a number of technical shortcomings which have compromised their usefulness. In recent years, however, significant developments in the design and construction of specimen stages and in systems for recording in situ experiments in real time in the electron microscope have led to a renewed interest in dynamic experiments. One such application is the study of the interaction of dislocations with interfaces in polycrystalline solids, a topic which is of fundamental interest in understanding the laws which govern macroscopic deformation. It has been clearly demonstrated that in situ experiments are essential to this investigation, as they have provided direct observation of deformation mechanisms which conventional TEM analyses, in which the samples are deformed before they are put in the microscope, cannot. The two types of TEM observations provide complementary information, each greatly enhancing the value of the other.
Electron-beam-induced reactions at surfaces
Authors: Smith David J. , McCartney M. R.
Published: June 2020

It is well-known that the intense electron irradiation needed to record HREM images or micro-analytical spectra is liable to cause permanent microstructural changes in the specimen region undergoing observation or analysis. Beam-induced modifications at surfaces are even more likely because of the increased probability of permanent loss of material and the likelihood of reaction with constituents of the residual microscope vacuum. In this short review, we first survey the mechanisms available for beam-induced surface reactions, then briefly summarize recent observations of surface modifications and finally discuss their validity for surfaces relative to other reaction mechanisms described elsewhere. Since our primary interest here is in the possibilities for eliciting atomic-scale local information using HREM or microanalytical techniques, consideration is restricted to inorganic solids which are far less susceptible to damage by the electron beam than organic materials.

Mechanisms. There are two basic mechanisms covered by the generic term “radiation damage” which could lead to electron-beam-induced surface reactions: ballistic or knock-on displacement whereby there is momentum exchange with an incident electron which may be sufficient to cause atomic displacement; and radiolytic processes which involve electron-electron interactions.