bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.