bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution x-ray analysis of dislocation networks nn tilt boundaries
Authors: Michael J. R. , Lin C. H. , Sass S. L.
Published: June 2020

The segregation of solute atoms to grain boundaries in polycrystalline solids can be responsible for embrittlement of the grain boundaries. Although Auger electron spectroscopy (AES) and analytical electron microscopy (AEM) have verified the occurrence of solute segregation to grain boundaries, there has been little experimental evidence concerning the distribution of the solute within the plane of the interface. Sickafus and Sass showed that Au segregation causes a change in the primary dislocation structure of small angle [001] twist boundaries in Fe. The bicrystal specimens used in their work, which contain periodic arrays of dislocations to which Au is segregated, provide an excellent opportunity to study the distribution of Au within the boundary by AEM.

The thin film Fe-0.8 at% Au bicrystals (composition determined by Rutherford backscattering spectroscopy), ∼60 nm thick, containing [001] twist boundaries were prepared as described previously. The bicrystals were analyzed in a Vacuum Generators HB-501 AEM with a field emission electron source and a Link Analytical windowless x-ray detector.
Irradiation-induced mass loss effects at low temperature are dependent on specimen material
Authors: Lamvik M.K. , Davilla S.D.
Published: June 2020

Low temperatures reduce the rate at which total mass or specific elements are lost from specimens during irradiation in electron microscopes. Many studies have shown such reductions when liquid nitrogen temperature was compared with room temperature. Some studies suggested an even greater benefit at liquid helium temperature. We recently found that there was a substantial reduction in the rate of mass loss from collodion when specimens were held at liquid helium temperature. The need for additional studies is illustrated by a comparison of collodion with albumin, which shows qualitative and quantitative differences in the response of these two materials to electron irradiation at liquid helium temperature.

Collodion had distinct advantages as an initial specimen: There have been previous measurements, thus allowing comparison. Collodion is sensitive to radiation, so experiments could be completed efficiently. Most important was that collodion films could be made of uniform thickness, thus allowing the inital thickness to be used to monitor for accidental pre-exposure or unwanted material (like adsorbed water).
High-resolution electron spectrometers for molecular microanalysis
Authors: Ottensmeyer F. P. , Jiang X. G.
Published: June 2020

The last decade has brought major advances in electron beam induced microanalytical capabilities, particularly with the utilization of energy loss electrons. These developments have been predicated primarily by the design and by the more ready commercial availabilty of better magnetic spectrometers, both for scanning transmission and fixed-beam transmission electron microscopy.

Theoretical and experimental investigation of spatial resolution or localization possible for microanalysis and elemental mapping has indicated a potential of about 0.5 nm at an energy loss close to 100 eV, improving slowly with increasing energy loss. At lower energy loss the spatial resolution worsens due to an expected increase in impact parameter, but is still anticipated to be of the order of 1 nm at a 10 eV loss.

Coupled with high spatial resolution is an experimentally observed very high sensitivity of detection and identification of a very small number of atoms at high concentration.
Analytical electron microscopy of fresh and vehicle-aged catalysts
Authors: Kim Sooho
Published: June 2020

Automotive catalysts have a general loss of activity during aging, basically due to two principal deactivation mechanisms. One of them is thermally induced “sintering,” which results in catalytic surface area reduction. The other is chemically induced “poisoning,” which in part causes blockage of active metal sites. The conventional bulk techniques have indicated that various catalyst functions were affected differently by poisons and thermal damage; however, they generally did not provide detailed descriptions of the mechanisms of deactivation. Only analytical electron microscopy (AEM) can provide microchemical and microstructural information to gain a more thorough and fundamental understanding of catalytic deactivation.

Fresh and vehicle-aged commercial automotive catalysts containing Pt, Pd, and Rh on alumina supports were prepared for AEM by a microtomy technique, which retains the spatial integrity of the catalyst pellet with uniform thickness. Then these AEM specimens were characterized in a transmission electron microscope (TEM) and in a dedicated scanning transmission electron microscope (STEM).
High-resolution TEM of precipitate plate growth by diffusional and displacive transformation mechanisms
Authors: Howe J. M. , Mahon G. J.
Published: June 2020

Precipitate plates can grow by diffusional, displacive or coupled diffusional/displacive (for interstitial alloys) mechanisms of interfacial motion. In each case, it is necessary to characterize the atomic details of the structural and/or compositional changes which occur at the matrix/precipitate interface in order to fully understand the transformation mechanisms. High-resolution transmission electron microscopy (HRTEM) provides unique capabilities for obtaining such information. This is illustrated below by HRTEM studies of interfacial structure performed on precipitate plates which grow by diffusional and diffusionless mechanisms in Al-Li-Cu and Fe-Cr-C alloys, respectively.

The growth of hexagonal T2 (Al2CuLi) precipitate plates on the {111{α f.c.c. matrix planes in an Al-2wt.%Li-1wt.%Cu alloy is an example of a diffusional transformation which requires substantial changes in both crystal structure and composition at the transformation interface. The growth of b.c.t. α martensite plates on the {252{γ f.c.c. austenite planes in a Fe-8wt.%Cr-1wt.%C alloy is more complicated than the T1 transformation crystallographically, but it is a good example of a diffusionless transformation which requires only a change in structure at the transformation interface.
SHaRE: Collaborative materials science research
Authors: Kenik Edward A. , More Karren L.
Published: June 2020

The Shared Research Equipment (SHaRE) Program provides access to the wide range of advanced equipment and techniques available in the Metals and Ceramics Division of ORNL to researchers from universities, industry, and other national laboratories. All SHaRE projects are collaborative in nature and address materials science problems in areas of mutual interest to the internal and external collaborators. While all facilities in the Metals and Ceramics Division are available under SHaRE, there is a strong emphasis on analytical electron microscopy (AEM), based on state-of-the-art facilities, techniques, and recognized expertise in the Division. The microscopy facilities include four analytical electron microscopes (one 300 kV, one 200 kV, and two 120 kV instruments), a conventional transmission electron microscope with a low field polepiece for examination of ferromagnetic materials, a high voltage (1 MV) electron microscope with a number of in situ capabilities, and a variety of EM support facilities. An atom probe field-ion microscope provides microstructural and elemental characterization at atomic resolution.
Theory of plasmon diffuse scattering in dynamical calculations for RHEED: A method of introducing inelastic scattering in multislice theory
Authors: Wang Z. L.
Published: June 2020

Multislice theory has been applied for investigating electron elastic scattering at crystal surfaces in reflection high-energy electron diffraction (RHEED). Quantitative analysis of RHEED intensity requires full dynamical calculation including multiple elastic and inelastic scattering. The purpose of this paper is to present a method for introducing plasmon diffuse scattering (PDS) in the multislice theory.

Considering an electron travelling in medium b parallel to an interface with distance x from medium a, the kinetic energy of this electron after travelling distance z is given as:

(1)

Where eV0 is the incident energy of the electron; (-eU0) is the potential energy of the electron in the atomic potential of the solid; and (-Ui is the total energy-loss of the electron due to plasmon excitation, which can be calculated from the relativistic dielectric excitation theory as [2]:
Modified multislice theory for calculating the energy-filtered inelastic images in REM and HREM
Authors: Wang Z. L.
Published: June 2020

Using a method introduced by Wang, the multiple plasmon diffuse scattering (PDS) can be included in dynamical calculation for reflection electron microscopy (REM) and high resolution electron microscopy (HREM). The calculated electron intensity distribution would be the combination of elastic and inelastic scattered electrons. In some experimental cases, it is desirable that the energy filtered inelastic image (EFIM) could be simulated. The purpose of this paper is to suggest a modified multislice theory for calculating the EFIM in REM and HREM.

Considering an electron travelling in medium b with distance x parallel to an interface from medium a, due to the plasmon excitation, the wavelength of the electron is perturbed by its energy-loss during the propagation. The modified phase grating function (PGF) of a thin potential slice ▵z might be written as [1]:

(1a)

with

(1b)
Analytic integration of contrast transfer functions
Authors: Rez Peter
Published: June 2020

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is

1

where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by

2

where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.

We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.
Identification of periodic structure characterized from amorphous support by simulation and processing techniques
Authors: O'Keefe Michael A. , Sattler Margaret L.
Published: June 2020

High resolution electron images that suggest crystalline lattice fringes in a background of amorphous material are difficult to interpret. A new technique of image processing, referred to here as “background subtraction”, was recently developed to enhance images of such crystalline particles supported on amorphous substrates. However, the interpretation of exact crystalline surfaces on the particle was not straightforward. We have now applied this enhancement technique, previously used exclusively on experimental images, to simulated images of small crystals on amorphous substrates. Additionally, other commonly-used processing techniques are introduced as comparisons for the “background subtraction” method to point out its advantage in defining particle shape and internal structure.

The model used for simulation consists of eight by eight units of anatase in [111] orientation (Fig. 1), enclosed in a “unit cell” of 56.8Å by 56.8Å (corresponding in size to 16 by 16 units of anatase). In addition we added various thicknesses of a structure of random SiO2units to this model to simulate the effects of an amorphous support.
An approach to damage-free analysis in Auger scanning microprobe
Authors: Mogami A. , Sekine T.
Published: June 2020

Sample damage induced by electron bombardment is one of the biggest problems to be noticed in an Auger scanning microprobe with high spatial resolution.

1) WHAT IS sample damage and 2) HOW TO MINIMIZE it are reported here.

Fig. 1 shows the beam-induced damage on a silicon plate specimen. The silicon LVV peaks and secondary electron emission abruptly change within 1 sec. just after the ion sputtering is stopped, while such a rapid change may have been easily overlooked. Fig. 2 shows that the silicon oxide (coated to a thickness of 1,000 Å on a silicon plate) is gradually deoxidized under the beam. A peak characteristic of metallic state clearly appears 10 min. after electron bombardment. The maximum allowable dosage of electrons is roughly calculated to be approx. 10-6 coulomb/μm2 for this specimen.

As an approach to damage-free analysis, beam brightness modulation (BBM) and the computer control system (CCS) with a light pen have been developed for the AUGER MICROPROBE, JAMP-10.
A new STEM capable of observing single heavy atoms in frozen specimens
Authors: Wall J. , Hainfeld J.
Published: June 2020

A new Scanning Transmission Electron Microscope (STEM) has been constructed in the Biology Department of Brookhaven National Laboratory. This instrument is designed specifically for imaging single heavy atoms in frozen-hydrated biological specimens. Observation of frozen-hydrated specimens has been shown to provide excellent structural preservation and reduced damage on biological specimens. The required components for this work are: a high resolution instrument with a suitable cold stage, a specimen changer capable of introducing frozen specimens into the microscope, and a suitable preparation chamber for fast freezing and transfer to the microscope.

A STEM instrument was chosen for this work because of its superiority for low dose dark field operation and single heavy atom detection. The Brookhaven STEM is similar to instruments built at the University of Chicago and at Johns Hopkins University, except for the added capability for woking with frozen specimens. A field emission gun operates at a vacuum of < 10-10 Torr to produce a beam of 10-11 Amp at 50 kV.
A tilting high temperature gas reaction chamber for the JEM 7A T.E.M.
Authors: Rhoades Brian L.
Published: June 2020

A gas reaction chamber has been designed and constructed for the JEM 7A transmission electron microscope which is based on a notably successful design by Hashimoto et. al. but which provides specimen tilting facilities of ± 15° aboutany axis in the plane of the specimen.

It has been difficult to provide tilting facilities on environmental chambers for 100 kV microscopes owing to the fundamental lack of available space within the objective lens and the scope of structural investigations possible during dynamic experiments has been limited with previous specimen chambers not possessing this facility.

A cross sectional diagram of the specimen chamber is shown in figure 1. The specimen is placed on a platinum ribbon which is mounted on a mica ring of the type shown in figure 2. The ribbon is heated by direct current, and a thermocouple junction spot welded to the section of the ribbon of reduced cross section enables temperature measurement at the point where localised heating occurs.
Preparation and properties of alumina supermicrogrid
Authors: Fujiyoshi Y. , Uyeda N.
Published: June 2020

It is often required in high resolution electron microscopy to use very thin supporting films for the reduction of random noise. When the specimen is crystalline film, it is also desirable that the thickness is controlled to be less than a hundred angstroms so that the specimen can be dealt with as a thin phase object. In both cases, a suitable supporting technique is necessary to secure the stability and mechanical strength of these very thin films and perhaps very small fragments of a few hundred angstroms in size. The present work was undertaken to prepare rigid supporting films by means of chemical thinning of alumina films produced by the anodic oxidation of aluminium plate. The overall procedure is outlined in Fig. 1.

The aluminium to be oxidized is cut in a form of a 1cm × 2cm plate from extra pure foil whose thickness ranges between 15 to 30μm.
The interpretation of the zone axis critical voltage effect
Authors: Buxton B. F.
Published: June 2020

In cross-grating high energy electron diffraction, the scattering of the incident beam by the atomic string potentials is often so strong that there are many zone axis critical voltages below 1 MV. Steeds et al. (1976, 1977) have therefore explored the possibility of obtaining structural information from these critical voltages. In particular, for simple zone axes of high symmetry with only one string of atoms in each unit cell of the projected potential, they were able to characterize zone axis patterns by the critical voltage Ec and a thickness parameter ξ24 defined as the (2)-(4) extinction length at an orientation approximately midway between the zone axis and the first Brillouin zone boundary. Here a simple model atomic string potential will be used to investigate the information which can be gleaned from these parameters.

The atomic string approximation (ASA) developed by Buxton and Tremewan (1977) will be used in order to avoid the large matrices encountered in the conventional many-beam theory.
Changes in electron image contrast associated with the melting of particles of lead
Authors: Curzon A.E. , Yang Y.H.
Published: June 2020

A Faraday cage based on a design by Drummond (1971) has been used in a Philips EM300 electron microscope operating at 100 kV to measure the image current for specimens consisting of lead particles condensed on thin carbon substrates.

Figure 1 shows how the current in the image of a given specimen changes when the temperature of the specimen is altered. At A' the specimen consists of polycrystalline lead. As the temperature is increased, some of the smaller particles begin to melt (Blackman and Curzon, 1959). Eventually, in the temperature range A to B, the remainder of the particles melt. Tm is called the melting temperature. When the temperature is reduced from above Tmthe particles supercool but they eventually solidify over the range B' to A' in the vicinity of Ts. Electron diffraction experiments were conducted to verify that the changes shown in Figure 1 were in fact correlated with the melting and solidification of the lead particles as stated above.
Transmission electron microscope studies in special ceramics
Authors: Zangvil A. , Gauckler L.J. , Schneider G. , Rühle M.
Published: June 2020

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.
Effect of radiation damage on the molecular image of Th-Phthalocyanine
Authors: Kobayashi Takashi , Uyeda Natsu
Published: June 2020

Because of a high sensitivity of organic molecules to the electron irradiation, it is difficult to analyse the structure of organic materials with a high resolution electron microscopy in atomic resolution.It is expected to be possible as the second best to detect a position of a heavy atom in a molecule even when the molecule became a skeleton as a result of intense electron bombardment. This paper is to report on the effect of damage on molecular image and a role of a heavy atom in the damage process.

The specimen is a thin crystalline film of tholium-phthalocyanine (Th-Pc) prepared by epitaxial growth. The film deposited on a single crystal (001)face of KCl by high vacuum evaporation and the thickness was monitored by the use of quartz crystal microbalance to be about 100 A and 50A. The film was supported on gold coated microgrid with small holes of 1-2μm in diameter.
New possibilities of electron microscopy for misfit dislocation studies!
Authors: Palatnik L.S. , Fedorenko A.I. , Chpakovckaja L.P.
Published: June 2020

Thin film growth in Frank-van der Merwe mode is accompanied by formation of misfit dislocation (MD) grid onto the interface of the film and a substrate.MD'e are playing important role in definition of such characteristics of epitaxial bycrastals,as the elastic strain values of the film and the substrate,the densitu of surface states for charge carriers,stability of manylayer systems,ets.

It was shown on the examples of β-Co/Cu,Cu/β-Co,Pt/Au and Al/Ag epitaxial bycrystals that at small misfits ( f<∼2%) MD's are introduced unhomogeneously onto interface (Fig.1,a) and features of MD's (distribution, density, Burgers vector) can be studied only by analysis of electron microscopy images.The periodicity of MD's is improving with increasing of f ⋝ 3% (Fig.1,b) due to introduction of them from the surface of film by climb and features of MD's can be studied by electron diffraction due to periodic array of MD's [3] .It was shown on the examples of PbS/PbTe,PbTe/PbSe,PbS/PbSe,Bi/Sb and Sb/Bi epitaxial bycrystals [4],that from diffractin pattern (Fig.1,c) one can easily deduce such features of MD's,as symmetry of their grid,mean interdislocation distance,their orientation relatively lattices of film and substrate and projection of edge component of their Burger's vector onto interface.
Superstructures and defects in alloys with the γ-brass structure
Authors: Morton A.J.
Published: June 2020

In a very wide range of alloy systems, but particularly those of the noble and transition metals with zinc and cadmium, alloys are formed with the so-called 'γ-brass crystal structure' or structures closely related to it. The prototype structure has a body-centred cubic unit cell containing 52 atoms and is non-centrosymmetric. Recognised variants of the structure include both a primitive cubic cell of 52 atoms and a face-centred cell of 416 atoms and there is also a rhombohedral cell which is only very slightly distorted from cubic. However in some systems such as the Cu-Zn, Ni-Zn and Pd-Zn systems unidentified “non-cubic” superstructures have been proposed from x-ray diffraction studies. In this study TEM and electron diffraction have been used to determine the nature of these superstructures and to identify defects in crystals with the γ-brass structure.

Figures 1 and 2 show that two distinct superstructures form in Cu-rich γ-brass.
Damage structure in zirconium alloys neutron irradiated at 573 to 923 K
Authors: Gllbert R.W. , Farrell K.
Published: June 2020

Introduction. Zirconiun alloys are resistant to void formation and associated Swelling, but are subject to radiation-enhanced creep, radiation growth and radiation hardening, all of which are dependent on the damage microstructures. Information on the microstructures will aid in understanding these phenomena. We have examined specimens of zirconium, ZLrcaloy-2, and Zr-2.5 wt% Nb irradiated at each of 573,673,773, and 923 K to fluences of 1.3, 1.2, 1.0, and 0.7 x 1025 n.m-2, respectively, in the Oak Ridge Reactor. Foils were electropolished using a 4:1 ethyl alcohol:perchloric acid solution at 240 K and examined at 100 kV in a Phillips EM300G electron microscope using a double axis tilt stage.

Observations. Annealed Crystal Bar Zirconium. Dislocation loops were present after irradiation at 573 and 673 K (Fig.1,2). The median diameter increased with irradiation temperature from 18.6 to 50 nm and corresponding loop concentrations decreased from 5 x 1021 to 5 x 1020m-3 respectively.
Applications of high spatial resolution hicroanalysis to materials problems using dedicated STEM
Authors: Hall Ernest L. , Vander Sande John B.
Published: June 2020

The scanning transmission electron microscope has afforded a dramatic improvement in the spatial resolution of X-ray microanalysis of thin specimens, allowing the investigation of extremely localized compositional variations in materials systems. In this paper, the results of high resolution composition profile analysis in several materials are presented. The materials were analyzed in a 100 kV field emission STEM manufactured by VG Microscopes, Ltd., and fitted with an energy dispersive X-ray spectrometer. The specimens were held in a double-tilt graphite cartridge which allowed X-ray detection in the tilt range 0°-20° about each axis. The vacuum in the specimen chamber was ∿ 2 x 10-9 torr during analysis. Electron probe spot sizes of 5-10 Å were used, corresponding to probe currents in the range of 10-10-10-9 amps.

For a given specimen composition, the spatial resolution of X-ray microanalysis in thin specimens is a function of probe size, accelerating voltage, specimen atomic number, and thickness.
Electron microscopy of the magnetic material SmCo5
Authors: Fidler J. , Skalicky P.
Published: June 2020

The magnetic material SmCo5 has attracted considerable interest for the use in permanent magnets. Microscopic investigations should provide information on the interaction of crystal defects and precipitates with the magnetic domain structure and thus about the special magnetic properties of this material. Single crystals of SmCo5 which has a CaCu5-structure were grown from 99,9 purity Sm and Co by the Bridgman technique in pyrolytic BN crucibles. Thin foils for TEM-investigations were prepared by ion-milling perpendicular to the growth-direction which always was <1216> or <0113>.

Electron microscopy revealed growth-dislocations, stacking-faults and Sm2Co17 precipitates, the density of defects beeing very low. The material has a very high magnetic anisotropy but a relative low elastic anisotropy characterized by Acomp= = 0,67 and Ashear = 1,03. The low anisotropy makes it possible to determine Burgers vectors of dislocations with the help of the invisibility criterion under two-beam conditions.
Exsolution and inversion in pigeonite from the Whin Sill, Northern England
Authors: Smith P.P.K.
Published: June 2020

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.

In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.
STEM versus CTEM beam damage: paraffin single crystals
Authors: Krause S. J. , Allard L. F. , Bigelow W. C.
Published: June 2020

IntroductionCurrently, the resolution of structural detail in conventional transmission electron microscopy (CTEM) of organic materials is limited by the electron beam damage suffered by the sample. It has recently been shown that the imaging modes now available in scanning transmission electron microscopy (STEM) provide the potential for improvements in resolution over CTEM methods. However, the effect of the sensitivity of an organic sample itself to beam damage has not been compared in STEM versus CTEM. In STEM each element of the sample area is briefly illuminated with a small diameter, high flux, scanning electron beam, whereas in CTEM the entire sample area is continuously illuminated with a large diameter, lower flux, static electron beam. Although it has been shown that the amount of sample damage in CTEM is independent of dose rate(2), the electron flux in STEM may range from 3 to 4 orders of magnitude greater than that in CTEM, with a possible influence on damage rate. Generally, the effects of beam size, high flux, and short dwell time of the scanning electron beam on sensitivity of the sample to damage in STEM are not known.
EDS spectral contamination in the EM-301
Authors: Johnson P.F. , Bates S.R. , Hren J.J.
Published: June 2020

Elimination of the sources of EDS spectral contamination in the Philips EM-301 ASTEM is particularly difficult due to the limited space available between the objective lense pole pieces. Into this space must go a sample holder, a cold finger decontamination device, an objective aperture, a backscattered electron detector (if used) and, of course, the sample, often supported by a grid. The EDS detector should be placed as close to the sample as possible, further reducing the space available.All of these, including the pole pieces, can result in unwanted systematic peaks in EDS spectra.

An earlier paper described the design and use of an A1 sample holder and cold finger. The use of A1 was satisfactory, except that the resulting aluminum peak precluded the analysis of A1 samples and interferred with the Si peak if present. A Be holder, similar in design to the A1 holder (1), was built.
Identification of oxide precipitates in annealed silicon crystals
Authors: Anderson Ron , Yang K. H. , Kappert H. F.
Published: June 2020

Prolonged heat treatment of Czochralski-grown silicon crystals containing oxygen concentrations on the order of 1018 atoms/cm3 usually causes formation of precipitates (1-3). These precipitates are assumed to be a form of silicon oxide. This assumption is based on the fact that the oxygen concentration, as measured by IR spectroscopy, is reduced after annealing. The precipitates growth kinetics are diffusion-controlled and their size can be calculated with reasonable accuracy from the supersaturation and diffusion coefficient of oxygen in silicon at the annealing temperature (3). However, no direct evidence of the precipitates as a form of silicon oxide has been reported. The main difficulty arises from the fact that microanalysis of the precipitates requires an instrument with both a capability of detecting oxygen plus high spatial resolution and detection sensitivity. Techniques such as electron diffraction fail to reveal extra dots or rings from the precipitates (1-3).

The Czochralski crystals used contained 1018 atoms/cm3 oxygen, were <100> oriented and doped with boron to 2 Ω-cm, annealed at 1100°C for 40 hours and then prepared for TEM analysis by chemical etching.
A combined TEM and SEM study of erosive wear
Authors: Kosel T.H. , Scattergood R.O. , Turner A.P.L.
Published: June 2020

Mechanisms of erosive wear are being studied using transmission electron microscopy (TEM) to examine the subsurface dislocation structures developed and scanning electron microscopy (SEM) to observe the surface topography. Specimens of recrystallized Ni 200 and copper single crystals have been eroded with 5 to 25μm glass microbeads and with 40 and 150 μm A12O3 particles at 53 m/sec using a slinger type erosion apparatus. Thin foils parallel to the original rough eroded surface and one μm or more below it have been prepared by first electroplating a few microns of nickel on the specimen and then electropolishing it away. Thin foil sections at 45̊ to the original surface have been prepared by sectioning specimens with thick electroplated layers; these allow observations to be made at different depths in the same foil.

Material removal during particle impingement erosion at low angles of incidence probably occurs by a cutting or micromachining mechanism similar to that suggested by Finnie (1).
Application of analytical electron microscopy to the study of partitioning of silicon in a 2 wt% Si eutectoid steel
Authors: Ridley N. , Al-Salman S.A. , Lorimer G.W.
Published: June 2020

The application of the technique of analytical electron microscopy to the study of partitioning of Mn (1) and Cr (2) during the austenite-pearlite transformation in eutectoid steels has been described in previous papers. In both of these investigations, ‘in-situ’ analyses of individual cementite and ferrite plates in thin foils showed that the alloying elements partitioned preferentially to cementite at the transformation front at higher reaction temperatures. At lower temperatures partitioning did not occur and it was possible to identify a ‘no-partition’ temperature for each of the steels examined.

In the present work partitioning during the pearlite transformation has been studied in a eutectoid steel containing 1.95 wt% Si. Measurements of pearlite interlamellar spacings showed, however, that except at the highest reaction temperatures the spacing would be too small to make the in-situ analysis of individual cementite plates possible, without interference from adjacent ferrite lamellae. The minimum diameter of the analysis probe on the instrument used, an EMMA-4 analytical electron microscope, was approximately 100 nm.
Microdiffraction studies of Al-Mg2Si
Authors: Lynch J. P. , Jacobs M. H. , Brown L. M.
Published: June 2020

The microdiffraction mode of Scanning Transmission Electron Microscopy (S.T.E.M.) has found several applications in metallurgical problems requiring diffraction information of high spatial resolution (1,2). The purpose of the work described here was to apply the microdiffraction facility on a S.T.E.M. equipped with a field emission gun (3) to the investigation of precipitate structure.

To obtain a microdiffraction pattern, the electron beam is stopped on the specimen. This results in the formation of a diffraction pattern from an area of the specimen defined by the probe cross-sectional area. To record the pattern a set of scan coils deflect the pattern past a collector aperture.

The effective probe diameter was determined at the edge of a precipitate to be less than 2 nm. The spread of the diffraction spots, due to the angular spread of the beam, is defined by the angle 2αo subtended by the objective aperture, while the angular resolution is determined by the angular size of the collector aperture, 2αc.
Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium
Authors: Carpenter G.J.C.
Published: June 2020

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.

The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.
The syneretic lens junction
Authors: David Robertson J. , Costello M.J. , McIntosh T.J.
Published: June 2020

The lens of the eye consists of closely adherent greatly elongated flattened narrow fiber cells that are electrically coupled by gap junctions. In thin sections the 100-150 Å intermembrane space usually seen in tissues between adjacent cells is greatly reduced between adjacent fiber cells. Freeze-fracture-etch (FFE) studies have demonstrated gap junctions between fiber cells. Several workers have observed expanses of square crystallinity in fiber cell membranes with a lattice constant of 6-7 nm. This has usually been attributed variously to artifact induced by calcium, pH or proteolytic enzymatic digestion. Square arrays have been seen in isolated fractions of fiber cell membranes prepared with detergents as minor components and dismissed as relatively insignificant and either related or unrelated to gap junctions. Some have regarded them as a form of gap junction.
Liposome fixation by UV polymerization
Authors: Zasadzinski Joseph A.
Published: June 2020

In standard dehydration and epoxy embedding of biological material, substantial portions of lipid are extracted. In addition, the mechanisms of lipid fixation by osmium tetroxide are either unknown or poorly understood. Liposomes, particles of lamellar liquid crystalline lipid in water, react immediately with osmium, but are not preserved and the bulk of the lipid is removed in subsequent processing. Several authors heve attempted to improve lipid retention by using water-soluble embedding media, various dehydration techniques, etc., with varying degrees of success. The structure and morphology of the lipid bilayers in tissue or in liposomes remains open to question. To deal with these problems, a new type of lipid which can be polymerized was developed. The synthetic lipid, N,N dimethyl, di(ethoxycarbonyl-2,4-hexadecadienyl)ammonium iodide, DDEAI, incorporates a polymerizable conjugated diene moeity in each tail of the molecule. The counterion in the head group is iodide, which provides a strong, yet localized electron scattering site which precludes the need for other stains (Fig. 1.).
Structural studies of DNA gyrase
Authors: Kirchhausen T. , Wang J. , Harrison S. C.
Published: June 2020

DNA gyrase, a prokaryotic type II topoisomerase, can introduce negative supercoils into DNA in an ATP-dependent manner and relax negative supercoils in the absence of ATP. Gyrase is a tetramer of two A subunits (MW 105,000) and two B subunits (MW 95,000), and it interacts with about 140 base pairs of DNA (based on staphylococcal nuclease and DNase I protection experiments). We have undertaken an electron microscopic study of gyrase and its binding to DNA, in order to determine how DNA wraps in its complex with the protein.
Cell surface topography and ultrastructural characteristics of human prostatic cancer cell line DU 145
Authors: Chakraborty J. , Von Stein A. , Saha S. K.
Published: June 2020

In spite of continuous efforts by numerous investigators, no ideal animal or in vitro cell model has so far been established for the human prostatic cancer cells. A human prostatic cancer cell line, DU 145, established by Stone et al. (1), provides a useful model for the basic understanding of malignant growth of this cell type. DU 145 has been characterized as an epithelial cell line, which retains most of its original growth characteristics (1,2). We are using this cell line as in vitro model system for biochemical, immunological and morphometric analyses, to understand the subcellular and molecular changes in these cells leading to their malignant transformation. The present paper is our first report describing a detailed characterization of DU 145 cell line.
Distribution of newly formed hepatic glycogen in adrenalectomized rats as observed by radioautography after injection of 3H-galactose
Authors: Michaels J. E. , Hung J. T. , Cardell E. L. , Cardell R. R.
Published: June 2020

In order to study early events of glycogen synthesis, we have used adrenalectomized (ADX) rats fasted overnight and injected with the synthetic glucocorticoid dexamethasone (DEX) to stimulate glycogen synthesis. Rats were given DEX 0-5 hr prior to sacrifice and injected with 2 mCi 3H-galactose 1 hr prior to sacrifice. Liver was prepared for light (LM) and electron microscopic (EM) radioautography by routine procedures.

The concentration of silver grains over hepatic cytoplasm was measured in LM radioautographs using a Zeiss Videoplan. The hepatocytes were categorized as unlabeled if no silver grains (gr) were present, lightly labeled (<10gr/100 μm2 cytoplasm) or intensely labeled (>10 gr/1002 μm cytoplasm). Although very few hepatocytes showed heavy labeling after 1 hr treatment with DEX, by 2 hr after DEX treatment 8% of the cells distributed throughout the lobule were intensely labeled.
Structural and functional analysis of pancreatic autografts
Authors: Fraser R.B. , Morais J.A. , MacAulay M.A. , MacDonald A.S.
Published: June 2020

Despite the successful management of diabetes by means of insulin therapy, interest is still high in the possibilities of pancreatic transplants. A more sophisticated insulin therapy is under investigation in order to prevent the sequelae that incapacitates and kills, for insulin in the management of diabetes only converts an acute fatal illness (diabetic coma induced by Ketosis) into a chronic degenerative one (microvascular complications,neuropathy or atherosclerosis of the heart and limbs). The advantages of organ transplantation include a physiological glucoregulatory control as opposed to the fluctuations inherent with insulin injections through the standard therapeutic routes. Major problems.however, are graft rejection, exocrine drainage and vascular thrombosis. The route of the drainage channel of the inplanted pancreas has been extensively examined and a useful model involving bladder anastomosis has been described.
Some recent developments in low-voltage e-beam testing of IC's
Authors: Buchanan R. , Menzel E.
Published: June 2020

With the increasing complexity and decreasing dimensions of IC structures, traditional mechanical probing techniques to determine voltage waveforms at specific locations within a device can no longer be applied. This is due to the difficulties of positioning a mechanical probe on features approaching one micron width, and the capacitive loading of the device under test which distorts the measured waveforms and in some instances causes the device to malfunction. These problems are all avoided, if the mechanical probe is replaced with an electron probe. An additional advantage is that the danger of device damage is avoided if a non-loading beam energy, typically in the range from 500-3,000eV, is selected.

While the electron probe diameters used for device testing are large by normal SEM imaging standards (typically 0.1-0.5 microns), current levels require to be as large as possible (typically 10-7 - 10-8A). This is especially necessary in some of the more important operating modes where the incident electron beam is pulsed, resulting in a substantial reduction in average current levels compared to continuous beam operation.
Holz pattern by hollow-cone illumination
Authors: Kondo Y. , Harada Y. , Kersker M.
Published: June 2020

The pattern of the higher order Laue-zone (HOLZ) lines is one of the useful information which is usually appeared in convergent beam electron diffraction (CBED) pattern. However, it is difficult to see details of HOLZ pattern in CBED, because the diffraction disk is of high intensity and complex patterns caused by the interaction of the zeroth order Laue-zene reflection. Recently, to avoid this disadvantage, we report a technique to observed HOLZ pattern selectively using a hollow-cone illumination. In this report, the incident convergent angle dependency of the pattern by hollow-cone illumination will be described.

Hollow-cone illumination was achieved by the electronic hollow-cone illumination (EHCI) device (the ray path of EHCI is shown in Fig. 1). A JEM-1200EX With EHCI device was used in this experiment.
Hot Stage HVEM Dynamic Studies of Order-Disorder Transitions in Lithium Ferrite
Authors: Van der Biest O. , Butler E. P. , Thomas G.
Published: June 2020

Lithium ferrite (LiFe5O8) is a ferrimagnetic compound with some interesting technological properties. In the disordered state the compound has the spinel structure with a random mixture of lLi+and 3Fe3+on the octahedral sites (spacegroup Fd3m). Below 750°C the lithium ions and iron ions on the octahedral sites order and the spacegroup symmetry is lowered to P4332 (P4132). The resulting domain structure has been described in detail by Van der Biest and Thomas.

The kinetics of the ordering reaction have been studied "in situ" in the hot stage of a HVEM. Annealing in the normal atmosphere of the microscope leads to a reduction of the compound in a way similar to that found for CoFe2O4. In order to control the stoichiometry of the compound during the ordering reaction, it is necessary to maintain an oxygen atmosphere around the specimen, hence the use of an "environmental" cell is necessary.
S.E.M. Fractography of Ultrasonic Fatigue in L65 Aluminum Alloy
Authors: Ashley K C H , Ditchfield R W , Downie G A McD
Published: June 2020

An aluminium alloy (L65) was fatigue tested in a longitudinal tension compression mode at a frequency of 20 kHz with a mean strain of 1.65.10-3. The specimens used were simple cylinderical rods of fully hardened, solution heat treated or fully annealed aluminium alloy. The effects of the variation in heat treatment on the nature of fracture were investigated by examining the fracture surfaces of these specimens in a Cambridge S4-10 scanning electron microscope.

The fracture surfaces of the fully hardened alloy exhibited the characteristics of cleavage fracture (Stage I and Stage II cracking) in agreement with Forsyth's theories. Occasionally these specimens underwent an unusual mode of centre initiated failure for which the fatigue endurance was greater than that experienced following the surface initiation in similar specimens.
Formation Mechanisms for Multiply Twinned Particles During Nucleation in the Au/MICA System
Authors: Lee Eal H. , Poppa Helmut
Published: June 2020

The formation of thin films of gold on mica has been studied in ultra-high vacuum (5xl0-10 torr) . The mica substrates were heat-treated for 24 hours at 375°C, cleaved, and annealed for 15 minutes at the deposition temperature of 300°C prior to deposition. An impingement flux of 3x1013 atoms cm-2 sec-1 was used. These conditions were found to give high number densities of multiple twin particles and are based on a systematic series of nucleation experiments described elsewhere. Individual deposits of varying deposition time were made and examined by bright and dark field TEM after "cleavage preparation" of highly transparent specimens. In the early stages of growth, the films generally consist of small particles which are either single crystals or multiply twinned; a strong preference for multiply twinned particles was found whenever the particle number densities were high. Fig. 1 shows the stable cluster density ns and the variation with deposition time of multiple twin particle and single crystal particle densities, respectively. Corresponding micrographs and diffraction patterns are shown in Fig. 2.
The Fine-Structure, Classification, and Orientation of Small Vapor-Deposited Metal Particles
Authors: Heinemann Klaus
Published: June 2020

The crystallographic structure and overgrowth orientation of small gold particles vapor deposited onto vacuum cleaved muscovite mica and {100} LiF substrate surfaces were examined by regular and selected zone dark field (SZDF) transmission electron microscopy in connection with the Bragg reflection imaging (BRI) method. In the case of Au/LiF, only very few (less than 2% particles) were found which exhibited the characteristic triangular shape of single crystalline, {111} oriented overgrowth crystallites with {220} lattice planes as lowest index planes normal to the substrate surface (Fig. 1, particle F). All other particles could be classified as multiply twinned particles, more than 90% of them having a {111} oriented nucleus.