bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amorphization of Zr3Al by 1-MeV electron radiation
Authors: Koike J. , Okamoto P.R. , Rehn L.E. , Meshii M. 
Published: June 2020

A crystalline to amorphous transition during high energy particle radiation has been reported in various intermetallic compounds. Chemical disordering is known to precede amorphization, which takes place only below a certain temperature. In Zr3A1, chemical disordering has been observed during 1-MeV electron radiation at temperatures between 130 and 375K but no amorphization has been reported. A large decrease in shear modulus was also observed during chemical disordering of Zr3Al by 1-MeV Kr ion irradiation at room temperature, followed by amorphization. In the present work, the possibility of amorphization of Zr3Al by electron radiation was examined, and the lattice softening due to chemical disordering was studied with electron diffraction.An alloy with a nominal composition of Zr-25at%Al was furnished by Chalk River National Laboratory. It was annealed at 925°C for 2 weeks and subsequently sliced and jet-polished. Specimen was irradiated and examined at 52K with 1-MeV electrons in the Argonne-HVEM.
Semi-coherent precipitation of silicon nitride in silicon
Authors: Kaushik V. S. 
Published: June 2020

Implantation of nitrogen into silicon, followed by high-temperature annealing causes formation of silicon nitride. At high doses, continuous polycrystalline layers are formed, while at lower doses, discrete precipitates are formed. These precipitates show preferred orientation with the silicon matrix. This paper presents the results of characterization of these semi - coherent precipitates using electron diffraction and cross-section TEM.Silicon (110) was implanted with 150 KeV N+ ions at a dose of 1 x 1018 /cm2 at 500° C at near-normal incidence. Annealing was carried out at 1200° C for thirty minutes in a nitrogen atmosphere. The samples were then analyzed by XTEM using a JEOL 2000 FX STEM operated at 200 kV with the electron beam parallel to [112] Si. A continuous polycrystalline layer of silicon nitride was observed at the mean ion range. In addition, a band of precipitates of α-Si3N4 was observed at about 1 μm below the wafer surface, presumably corresponding to the fraction of ions channeled along [110] Si.
Heterogeneous precipitation on misfit dislocations in Si/Si-2%Ge epitaxy
Authors: Posthill J.B. , Lee D.M. , Shimura F. , Rozgonyi G.A. 
Published: June 2020

Metallic impurities such as Au, Ni, Cu, Fe, etc. are known to degrade the performance of electronic devices. Therefore, necessary precautions must be taken to ensure that impurity contamination is minimized. Nevertheless, some degree of inherent and process-induced impurity introduction into silicon crystals is unavoidable. An intrinsic gettering annealing cycle can be utilized to nucleate metallic precipitates on dislocations produced upon SiO2precipitation.eg.1 Another impurity gettering approach is the intentional introduction of a controlled, stable array of dislocations to act as heterogeneous nucleation sites. This is one type of extrinsic gettering scheme. This contribution addresses our ongoing studies pertaining to extrinsic gettering by an orthogonal grid of b=1/2<011> 60° misfit dislocations generated in Si/Si-2%Ge epitaxy. Additionally, the prospect of uniformly decorating dislocations with a conducting metal presents the technological opportunity for forming buried micro-wires as proposed previously.A buried Si-2%Ge epitaxial layer of ˜ 2 μm thickness was grown on (001) silicon substrates at 1080°C by chemical vapor deposition. The Ge concentration is defined as the ratio of GeH4to SiH2Cl2. On top of the Si-2%Ge layer, a 4-13 μm pure silicon capping epilayer was grown. Misfit dislocations were generated at both of the Si/Si-2%Ge interfaces.
Ab initio band theory approach to electron energy loss near edge structures
Authors: Weng Xudong , Sankey O.F. , Rez Peter 
Published: June 2020

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.
Improving the accuracy of convergent-beam thickness measurements
Authors: Christenson K. K. 
Published: June 2020

Convergent-beam diffraction patterns taken at appropriate “two-beam” conditions allow simple, rapid determinations of a specimen's thickness, extinction length and even its anomalous absorption coefficient (1,2). We here note three points to consider when obtaining the pattern.First, in thickness measurements the ratio of the fringe spacing to the spacing between the disks is utilized; there is an underlying assumption that the two distances are on the same angular scale. This assumption is incorrect if the illumination crossover is not in the plane of the specimen and simultaneously, the diffraction lens is focused incorrectly. If the crossover is at the specimen (Fig. 1a), varying the focus of the diffraction lens (changing w) varies the distance between the disks and the sizes of features within the disks in the same way, only the magnification of the pattern is changed. Likewise, if the diffraction lens is focused correctly, on the back focal plane of the objective lens, the angular scale within the disks matches that between the disks and neither scale is affected by variations in the illumination.
The effects of chromate deoxidizer treatment parameter variation on surface morphology and adhesive bonding of 2219-T87 aluminum
Authors: Rowland L. J. , Allgeyer D. F. , Brown R. J. 
Published: June 2020

The shell of the Space Shuttle's External Tank is 2219-T87 aluminum to which an epoxy primer is applied to allow bonding of the Thermal Protection System (TPS). A chromate deoxidizer is used to prepare the aluminum surface for primer bonding. In this study, scanning electron microscopy (SEM) was used to characterize the surface morphology of 2219-T87 aluminum associated with different bond strengths produced by varying the deoxidizer treatment parameters.Eight sets of two 2219-T87 aluminum panels were treated with chromate deoxidizer. One set was used as a control. The second set was subjected to an additional deoxidizer treatment, while the third set received two additional deoxidizer treatments. The fourth, fifth, and sixth sets were held for 5, 10, and 15 minute post deoxidiation and prior to final rinse with demineralized water. The two remaining sets were deliberately contaminated with 25:1 and 100:1 water:deoxidizer solutions, which were allowed to dry on their surfaces.
HRTEM of antigorite: The structure as a polysomatic series
Authors: Spinnler Gerard E. , Otten Max T. 
Published: June 2020

Antigorite is one of the serpentine minerals, a group of 1:1 layer silicates with the approximate composition of Mg3Si2O5(OH)4. These minerals display an unusual variety of crystal structures even though they are almost identical in composition; chrysotile has an elongated-tube structure, lizardite occurs as flat plates, and antigorite has corrugates layers.The details of the crystal structures of the serpentine minerals are not completely known. Threedimensional structure refinements only exist for one- and two- layer lizardite. For antigorite, the only direct structural information consists of a two-dimensional Fourier synthesis of hOI diffractions. The lack of detailed structural data on these minerals arises from the complexity of the structures as well as the paucity of sufficiently large, well-formed single crystals. In addition, structural disorder is common in these minerals, making structure refinement difficult.High resolution transmission electron microscopy (HRTEM) has been used to study antigorite in order to discriminate among various structural models of antigorite and to characterize its microstructures
TEM Studies of modulated structures in the monoclinic (B) phase Of CaO-stabilized Dy2O3
Authors: Kim Y. J. , Kriven W. M. 
Published: June 2020

Dysprosia (Dy2O3) undergoes a monoclinic (B) to cubic (C) transformation on cooling through 1950°C, which is accompanied by an 8% volume increase and shattering. Minor additions of CaO combined with rapid quenching, however, are able to stabilize the high temperature phase down to room temperature. The similarities with the tetragonal to monoclinic transformation of ZrO2 suggest that it may be a possible high temperature transformation toughener. A sample of 8 mol% CaO was sintered at 1900°C and cooled at an intermediate rate. About 90% of B phase, which invariably had a modulated structure, was retained.From TEM studies of this B phase, it was shown that most of the selected area diffraction (SAD) patterns in different orientations consisted mainly of three types of reflections: (i) major reflections from the monoclinic lattice; (ii) satellites associated with each major reflection; and (iii) split reflections at the middle of the framework of major reflections. Depending on the orientation, (ii) and (iii) were accompanied by twinned reflections. Fig. 1 displays (i) and (iii) type reflections.
Microstructural analysis of sputtered titanium nitride ceramics
Authors: Dabrowski B. W. 
Published: June 2020

Titanium Nitride, TiN, is an attractive ceramic material in the tool and electronic industries because of its high hardness, corrosion resistance and high electrical conductivity. TiN was investigated for use as a high reliability electrical contact material to replace gold in certain microelectronics applications. However, the optimal contact resistance values were not always reproducible despite processing with stable and repeatable sputtering parameters, use of ultra-pure gases, and a high-base vacuum. It was suspected that these inconsistentcies could be due to subtle changes in the microstructure. Therefore, the purpose of this paper is to present the initial results from a TEM study of TiN thin films.Approximately 5μm thick TiN films were deposited onto a variety of substrates by the CTS Corporation in a UHV reactive sputtering system [1], Through-foil orientations of the films were obtained by grinding the substrate side to a total thickness of ∼15 μm.
Structure of an asymmetrical tilt boundary in gold
Authors: Norden Hans , Smith David A. 
Published: June 2020

Balluffi and coworkers developed a technique for making grain boundaries, with chosen misorientations, by welding together appropriately oriented single crystal films. This technique has been used to make gold bicrystals with a misorientation which does not correspond to any short period structure of the kind which is usually thought to have low energy. The procedure followed was to join {100} and {111} single films with <110> directions in each film approximately parallel. With [110](001) and [110](111) exactly parallel an asymmetrical tilt boundary with misorientation 54.73°/[110] is produced. For Σ, the reciprocal fraction of coincidence sites <50, the periodic boundary structures nearest in misorientation are 50.48°/[l10], Σ=11; 55.88°/[110], Σ = 33. Analysis of the present boundaries can therefore give direct evidence relating to the controversial question of the extent of the physical significance of the dislocation model for grain boundaries.Fig. 1 shows a typical region of the interface. Patches of grain boundary are surrounded by regions where the two films are not in contact.
Contrast effects at grooved interfaces
Authors: Rasmussen D.René , Simpson Yonn Kouh , Kilaas Roar , Carter C. Barry 
Published: June 2020

Recent studies have shown that the characterization of the microstructure of ceramics such as polycrystalline alumina is complicated by the surface grooving of the grain boundary (thermal grooving and preferential mechanical damage produced by specimen preparation processes). Many of the TEM techniques, such as the Fresnel-fringe technique and the dark-field diffuse scattering technique, that are used to test for the presence of a glassy phase at grain boundaries do not give unambiguous results due to this grooving effect. Fig. 1 shows an example of such a grain boundary in alumina: the grain boundary has been inclined to show grooving at both surfaces, see fig. 2a. It is the aim of this investigation to study the effect of grooving on the Fresnel-fringe contrast and on high resolution images of grain boundaries by computer simulations.The simulations were performed using the multislice program TEMPAS installed on a CONVEX computer.
Quantitative measurements of stresses at grain boundaries in polycrystalline metals
Authors: Clark W. A. T. 
Published: June 2020

It has long been recognized that the deformation of polycrystalline metals proceeds by the movement of individual dislocations both within the grains and across the grain boundaries which separate them. It is known, for example, that the yield stress is directly affected by the density of grain boundaries in a metal; in the familiar Hall-Petch relationship it is inversely proportional to the grain diameter. Various models have been proposed to account for this behaviour, all of which involve the interaction between dislocations and grain boundaries (for a review see e.g. ref. 1). Microscopically, these interactions can be accomplished by several different mechanisms, which include the nucleation of new dislocations, direct transmission of dislocations across the interface, the absorption and desorption of dislocations into and out of the interface.The TEM can be used for both static and in-situ dynamic studies of these interactions. In the static mode, a TEM is used to analyze fully the crystallography of dislocation pile-up/grain boundary interactions; one such pile-up is shown in Fig. 1.
Dissociated Σ=27 boundaries in silicon
Authors: Garg A. , Clark W.A.T. , Hirth J.P. 
Published: June 2020

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.
A series of JEOL 2000 FX vacuum system upgrades to provide substantial performance improvements at modest cost
Authors: Mardinly A. J. 
Published: June 2020

Since its introduction three years ago, the JEOL 2000 EX/FX series of transmission electron microscopes has been extremely popular. However, there is one aspect of the instrument that could be improved; that is the vacuum system. The factory supplied 150 l/s ion pump provides satisfactory, but not outstanding performance. Ultimate vacuum of 3x10-7 Torr could be achieved, but was difficult to maintain during operation. In addition, the conductance of the manifold limited pumping speeds at the accelerator. Evacuation times after column or gun maintenance and recovery time after specimen exchange required improvement. Finally, some specimen contamination occurred during focussed probe operation, and ice formation made cold stage work difficult.It was decided to improve the vacuum system in a mannner which would be as non-invasive as possible to the microscope. The pumping system could be augmented, but there should be no dismantling of the microscope and any changes should be compatible with the microprocessor controlled valve system.
Calculation of knock-on sputtering cross sections
Authors: Bradley Charles R. 
Published: June 2020

Electrons in a TEM can be energetic enough to remove atoms from the exit surface of a sample. The probability of a collision imparting enough energy to dislodge an atom from the surface is expressed in terms of a cross-section which depends on the nuclear charge, the atomic mass, surface binding energy, and incident electron kinetic energy. McKinley and Feshbach have given an asymptotic relation for the Mott cross-section which has been widely used in studies of this process. However the expression is accurate only for low Z, and low incident electron energies (see Figure 1). Since modem TEMs often have accelerating voltages up to 300 or 400kV and occasionally over 1MV the assumption of low incident electron energies is not valid and the restriction to low Z is prohibitive.We have developed a program to evaluate numerically the total Mott cross-section. This program uses an algorithm like that described by Doggett and Spencer to evaluate two conditionally convergent Legendre series.
Nanometer-area diffraction of small iron crystallites in single crystalline Fe-MgO composite films
Authors: Tanaka N. , Mihama K. , Ou H. , Cowley J.M. 
Published: June 2020

Nanometer-sized iron(Fe) crystallites can be prepared in a single crystalline magnesium oxide(MgO) film by a simultaneous vacuum deposition of Fe and MgO. The crystallites are grown epitaxially and almost coherently in the film, the orientation being (001) [110]Fe//(001)[100]MgOand (011) [100]Fe//(001) [100]MgO. A heat treatment of the as-grown composite films at 500-1000°C brings about a phase-transformation from α -iron(b.c.c.) to γ -iron(f.c.c.). In the present study, the phase-transformation and the structure of the γ-iron crystallites are studied by nanometer-area electron diffraction(nanodiffraction) in TEM and STEM as well as high-resolution electron microscopy.The specimens were single crystalline Fe-MgO composite films prepared on a NaCl (001 ) surface by co-evaporation of Fe and MgO. The films were separated from the substrate in water and mounted on a perforated carbon film. Nanodiffraction in TEM was performed in a 200 kV transmission electron microscope(JEM- 2000FX)2 and that in STEM3was carried out in a 100 kV scanning transmission electron microscope (VG-HB5) equipped with a specimen-preparation chamber.
Microstructural evolution of an iron silicate catalyst with thermal and hydrothermal treatments
Authors: Csencsits Roseann 
Published: June 2020

Iron silicate analogs of the zeolite ZSM-5 may be directly synthesized from iron silicate gels in a manner which differs slightly from the alumino-silicate ZSM-5. The resultant white, crystalline iron silicate is referred to as FeZSM-5 in the as-synthesized form. Thermal treatment removes the organic crystal-directing agent and moves some of the framework iron into non-framework sites producing the calcined form of the molecular sieve FeZSM-5. Subsequent hydrothermal treatment moves more of the iron out of the molecular sieve framework. This iron-rich second phase and the ZSM-5 pore structure can be used to convert synthesis gas (CO and H2) to “gasoline range” hydrocarbons and water (Fischer-Tropsch synthesis). To optimize the Fischer-Tropsch catalyst, homogeneity in the particle size distribution and in the distribution of catalytic iron throughout the particles is desired.Scanning electron microscopy (SEM) was used to characterize the overall molecular sieve particle sizes and morphologies as a function of preparation conditions.
X-ray emission spectroscopy study of iron silicate catalyst FeZSM-5
Authors: Csencsits R. , Lyman C.E. , Gronsky R. 
Published: June 2020

Iron silicate analogs of the zeolite ZSM-5 may be directly synthesized from iron silicate gels in a manner which differs slightly from the alumino-silicate ZSM-5. The resultant white, crystalline iron silicate is referred to as FeZSM-5 in the as-synthesized form. Thermal treatment removes the organic crystaldirecting agent and moves some of the framework iron into non-framework sites producing the calcined form of the molecular sieve FeZSM-5. Homogeneity in the distribution of catalytic iron throughout the particles is desired in an optimal catalyst. Distribution of the iron throughout the framework in the assynthesized forms would affect the final distribution of catalytic iron in the calcined and steamed forms; thus, the iron distribution throughout the as-synthesized and calcined forms of FeZSM-5 were studied using the high spatial resolution of the analytical electron microscope.X-ray emission spectroscopy (XES) performed in the transmission electron microscope (TEM) and the scanning transmission electron microscope (STEM) was used to determine the inter- and intra-particle composition variations for FeZSM-5.
What may theoreticians and electron microscopists learn from each other about phase transformations?
Authors: Russell K.C. 
Published: June 2020

Plenty! Unfortunately theoreticians and experimentalists generally live in separate worlds, if not universes, and are oftentimes happier that way. Dealing with the other party requires work, both to master unfamiliar concepts and to develop one's research in the direction and to the point that the other can understand and deal with it. More usually the theorists make predictions on what pleases them while the experimentalists measure the quantities which please them. The overlap between the two sets is often minimal, and sometimes nil.Real cooperation and learning occurs when each develops his research product to the point that it is useful to the other, and in addition can explain his needs to the other.Unfortunately, sometimes in spite of the best of efforts common ground cannot be found. I refer in particular to early attempts in solid state phase transformation studies to relate nucleation theory and experiment. The theorist typically views the progress of a phase transformation as starting with an incubation period after which steady state nucleation conditions are established and the particle number density increases linearly with time. Then nucleation ceases and the particles grow at constant number density. Finally coarsening occurs and the number density decreases with time while the remaining particles get bigger.