bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure imaging of grain boundaries in F.C.C. metals
Authors: Krakow William 
Published: June 2020

One can now extract information about the projected atomic structure of tilt grain boundaries in metals from zone axes orientations which are not the most open structures as in previous lower voltage microscopic studies of a few years ago. This has been made possible in part by the development of intermediate voltage microscopes capable of a point resolution exceeding 2Å level For these studies it was also necessary to develop techniques for fabricating tilt boundary structures from epitaxially grown Au thin films placed in contact. Analysis of grain boundary micrographs further required that Fourier image filtering and enhancement be applied to the original micrographs. Subsequent computer modelling of the dynamical diffraction processes and images was also necessary to insure the proper image interpretation.An example of a ∼80Å thick thin film containing a symmetrical tilt boundary corresponding to a Σ = 17/[001]28.1° (410) is displayed in Fig. 1. There is a [100] tilt axis common to both grains and the {200} crossed sets lattice planes on each side of the interface require a resolution level of 2.03Å which is well beyond the {111} planar spacings of 2.3Å of the most open [110] orientation in Au. Here the atom columns are designated by either open circles or crosses corresponding to a two layer repeat. The boundary dislocation cores are designated by structural units of capped trigonal prisms or the same with one cap modifying to contain a rhombohedron unit.
Electron holography for magnetic property study of materials
Authors: Tonomura Akira 
Published: June 2020

An electron beam is often modulated, only in phase and not in intensity. When the beam passes through a magnetic field or a ferromagnetic thin film which can be regarded as pure phase objects. Therefore, great defocusing is indispensable for magnetic domain observation in Lorentz microscopy. Electron interference microscopy, however, can directly display the phase distribution of an electron beam in an in-focus electron micrograph, and consequently should provide direct information about magnetic fields.The development of a coherent field emission electron beam has opened a way to such a possibility using electron holography in which the phase-amplified phase distribution can be displayed as an interference micrograph. In addition, contour fringes have been interpreted as in-plane magnetic lines of force. Such an intuitive interpretation is possible for the following reason (Fig.1). An incident wavefront is displaced by the vector potential circulating around a magnetic field.
Dark-field electron spectroscopic imaging of aged microstructures in an aluminium lithium base alloy
Authors: Solórzano I. G. , Probst W. 
Published: June 2020

The examination of microstructures make very high demands on the imaging quality and, therefore, on the instrumentation. In Al-Li base alloys it is of great interest to determine parameters such as size, distribution, morphology and coherency of precipitate phases as they dictate their mechanical behavior. In order to reveal morphological features with high quality the electron spectroscopic imaging (ESI) in dark field mode has shown to be quite a powerful technique.The ESI technique in the TEM is based on the possibility that accelerated electrons can be elastic and inelastically scattered by the sample atoms, as recently reviewed. The electron distribution in the transmitted and diffracted beams through a crystalline sample is such that both energy loss and elastic electrons will enter a typical objective aperture and thus contribute to both bright field and dark field images. The effect of the polyenergetic electrons is that the image is affected by chromatic aberration of the objective lens. In CTEM’s this effect is enhanced the lower the accelerating voltage and the thicker the sample.
In situ high-resolution Electron Microscopy
Authors: Sinclair Robert 
Published: June 2020

In recent years, there have been many dramatic recordings of dynamic behavior, taken at the atomic level by high-resolution electron microscopy. However in the majority of cases, reliance has been placed on the imaging electron beam to bring about the changes in question. There are many disadvantages to this approach, not the least of which is the lack of experimental control available to the operator. Accordingly we have developed the application of a heating holder to achieve stable elevated temperatures at which reactions can be followed under atomic imaging conditions. This article briefly reviews our progress to-date.Our microscope system is quite conventional, showing that there is no major impediment to hot-stage HREM. We have employed a Philips EM 430 ST (300kV) instrument equipped with a Gatan image pick-up device and a commercial video-recorder. The heating holder is the Philips single tilt sideentry model (PW 6592) which we have found works well up to about 875°C. Of course a double tilt holder is preferable but we overcome the tilting limitations by judicious positioning of cross-section specimens. Image stability can be achieved by heating to a temperature below that of the observation for several minutes before "ramping up" to the desired level.
HREM investigations of Si/SiO2/poly-si compositions
Authors: Maksimov S.K. 
Published: June 2020

Application of poly-silicon conductive films in integrated circuits promises a number of advantages. In poly-Si technology, however, there are many unsolved problems. In particular, the cause of anomalously high current gains (β) observed by many authors is now being discussed. For their explanation two hypotheses are mostly put forward: according to the first the effect is accounted for by tunneling carriers through the boundary layer of SiO2. according to the second - it is associated with clustering the impurites at the interface. The present paper is an attempt to explain the effect by investigating the structure of the interfaces in Si/SiO2/poly-Si compositions.Layers of poly-Si 0.3μm thick were deposited at 620° on the Si (001) surface prepared by various ways: by etching in HF:H2O/(1:50).using a natural oxide or thermal oxide layers of different thickneses. Then Part of samples was doped with As+ ions with energy of 75 keV at dose 1×1016 cm-2 . The samples were annealed at 850° C during 1 hour; part of them were subjected to a repeat annealing during 30 min at 1000°C.
High-resolution Electron Microscopy of GaInAsP: Implications for the study of interfaces and decomposition phenomena
Authors: Bons A.J. , Schapink F.W. , Schryvers D. 
Published: June 2020

The quaternary semiconducting compound GaxIn1-xAsyP1-y has important applications in optoelectronic devices, in the form of heterostructures and quantum wells. Lattice matching between two materials with a composition difference (Δx,Δy) is achieved if Δy≈2.2Δx. Furthermore, decomposition structures have been described in these compounds; the decomposition is expected to follow Δy≈=Δx (Fig. 1). In the present study the sensitivity of high-resolution electron microscope (HREM) images for these composition variations is investigated.GaxIn1-xAsyP1-y layers lattice-matched to InP (x=0, y=0) have been studied with HREM in [001] plan view specimens, and in <110> and <100> cross-sections. The experimental images were interpreted using image simulations. The observations can be summarized as follows:
(1) Even small differences in composition between lattice-matched layers (Δx≈0.17, Δy≈0.37) lead to appreciable HREM-image contrast in <100> cross-section specimens (Fig. 2). <110>-orientations are less sensitive, but interfaces associated with Δx≈0.26, Δy≈0.56 still show good composition contrast (Fig. 3).
TEM characterization of Au/Polysilicon interactions
Authors: David Theodore N. , Allen Leslie H. , Barry Carter C. , Mayer James W. 
Published: June 2020

Metal/polysilicon investigations contribute to an understanding of issues relevant to the stability of electrical contacts in semiconductor devices. These investigations also contribute to an understanding of Si lateral solid-phase epitactic growth. Metals such as Au, Al and Ag form eutectics with Si. reactions in these metal/polysilicon systems lead to the formation of large-grain silicon. Of these systems, the Al/polysilicon system has been most extensively studied. In this study, the behavior upon thermal annealing of Au/polysilicon bilayers is investigated using cross-section transmission electron microscopy (XTEM). The unique feature of this system is that silicon grain-growth occurs at particularly low temperatures ∽300°C).Gold/polysilicon bilayers were fabricated on thermally oxidized single-crystal silicon substrates. Lowpressure chemical vapor deposition (LPCVD) at 620°C was used to obtain 100 to 400 nm polysilicon films. The surface of the polysilicon was cleaned with a buffered hydrofluoric acid solution. Gold was then thermally evaporated onto the samples.
TEM study of very thin InGaAsP layers grown by liquid-phase epitaxy
Authors: Bert N.A. , Kosogov A.O. 
Published: June 2020

The very thin (<100 Å) InGaAsP layers were grown not only by molecular beam epitaxy and metal-organic chemical vapor deposition but recently also by simple liquid phase epitaxy (LPE) technique. Characterization of their thickness, interfase abruptness and lattice defects is important and requires TEM methods to be used.The samples were InGaAsP/InGaP double heterostructures grown on (111)A GaAs substrate. The exact growth conditions are described in Ref.1. The salient points are that the quarternary layers were being grown at 750°C during a fast movement of substrate and a convection caused in the melt by that movement was eliminated. TEM cross-section specimens were prepared by means of conventional procedure. The studies were conducted in EM 420T and JEM 4000EX instruments.The (200) dark-field cross-sectional imaging is the most appropriate TEM technique to distinguish between individual layers in 111-v semiconductor heterostructures.
Microstructure of barium monoferrite BaFe2O4
Authors: González-Calbet J.M. , Nicolopoulos S. , Vallet-Regí M. 
Published: June 2020

BaFe2O4 appears at the initial stage of the solid state reaction during the synthesis of hexaferrites with Ba as divalent cation. In the HREM study of this phase, linear defects like crystallographic shear planes are observed which could change the ideal stoichiometry. Crystals are twinned, confirming previously predicted results from X-Ray data.Although the crystal structure and superstructure of the BaFe2O4 is well established, the microstructure still remains unknown. This phase is always present during the synthesis of several hexaferrites; the study of the microstructure could help to the understanding of the solid state reaction to synthetize new ferrite phases.A series with nominal composition Ba2Cu2Fe12022 (Y type hexagonal ferrite) was prepared with different annealing conditions for each sample. Details about the thermal treatments and the final products are given elsewhere. From X-Ray powder diffraction data, the presence of BaFe204 is always identificated at the final products.
Sensitivity of various phytates to beam damage during x-ray analysis
Authors: Ockenden Irene , Lott John N.A. 
Published: June 2020

Phytic acid (myoinositol hexaphosphoric acid) has 12 hydrolyzable hydrogens and forms salts with a variety of cations. Phytic acid salts are stored in seeds and act as nutrient reserves of elements such as Mg, K, Ca and P. In diets heavily dependent on grains, phytates have been implicated in reducing the bioavailability of elements such as zinc and iron. The complexing properties of phytates have made these compounds useful in a number of medical and industrial procedures.Phytin reserves in seeds often are localized in electron dense spherical particles called globoid crystals located within protein bodies. The characteristics of globoid crystals remain poorly defined. Energy-dispersive x-ray analysis of individual globoid crystals from various species has shown that there is considerable variation in the relative proportions of Mg, K, Ca and P species-to-species.
Electron irradiation effects in quartz single crystals and polycrystalline materials
Authors: Flörke O. W. , Martin B. , Röller K. , Wirth R. 
Published: June 2020

Electron irradiation damage in quartz and irradiation induced amorphism (metamict transformation in α-quartz) have been studied by several authors.The present investigations are focused on the orientation dependence of the irradiation damage, the influence of the proton and OH−concentration and the behaviour of grain boundaries during electron irradiation. Starting materials were synthetically grown quartz crystals with well defined OH−content and the crystallographic orientations (0001) (c-cut) and (2110) (x-cut). Polycrystalline quartz from metamorphic rocks (Western Alps) were used for studying the influence of electron irradiation on grain boundaries. Samples were prepared from thin sections (thickness about 30 μm) by ion milling and coated with carbon. The irradiation experiments were carried out in a JEOL JEM 200 CX electron microscope at 200 kV acceleration voltage at room temperature and at about 117 K.
Applications of SEM/EDXA in cement clinker investigation
Authors: Tagnit-Hamou Arezki , Sarkar Shondeep L. 
Published: June 2020

All the desired properties of cement primarily depend on the physicochemical characteristics of clinker from which the cement is produced. The mineralogical composition of the clinker forms the most important parameter influencing these properties.Optical microscopy provides reasonably accurate information pertaining to the thermal history of the clinker, while XRDA still remains the proven method of phase identification, and bulk chemical composition of the clinker can be readily obtained from XRFA. Nevertheless, all these microanalytical techniques are somewhat limited in their applications, and SEM/EDXA combination fills this gap uniquely by virtue of its high resolution imaging capability and possibility of instantaneous chemical analysis of individual phases.Inhomogeneities and impurities in the raw meal, influence of kiln conditions such as sintering and cooling rate being directly related to the microstructure can be effectively determined by SEM/EDXA. In addition, several physical characteristics of cement, such as rhcology, grindability and hydraulicity also depend on the clinker microstructure.
Imaging of chemical reactions in Pt-Sn thin films
Authors: Dufner D. C. 
Published: June 2020

The general goal of this research is to clarify mechanisms of solid state reactions at the atomic level as a step in the rationalization of macroscopic reaction behavior in solids. A study of chemical reactions occurring as interdiffusion or other transport processes proceed in thin films can be made by means of HRTEM. In this research, chemical changes occurring near interfaces in solid specimens which are very thin (<20nm) in at least one direction are studied.As previously studied with the Au-Sn system, the chemical reactions in the Pt-Sn system are being observed in this investigation. Thin film samples were prepared by the two-film method introduced by Shiojiri. Several hundred nanometers of Pt were vacuum deposited onto holey carbon films mounted on TEM grids. Sn films with an average thickness of 20nm were created by evaporation at rates of 1.5-3.0 nm/sec onto air-cleaved KBr substrates. The Sn films were wet-stripped and collected on the holey Pt grids. This combination of Pt and Sn films formed a solid-solid interface through which interdiffusion of Pt and Sn can take place and allowed for compositional and structural changes to be observed in the TEM. In some preparations, islands of Pt were evaporated directly onto the Sn films. TEM was carried out on the Philips 400T at 120kV or on the JEOL 2000FX at the Texas Center for Superconductivity at the University of Houston.
A symmetry-violating precipitation process induced under irradiation
Authors: Kesternich W. 
Published: June 2020

TiC precipitates in austenitic steel have been found to reveal a very unusual precipitation behaviour /l,2/. As a consequence, nucleation initiated by dislocation recovery or growth induced during recrystallization can be used to create predesired modifications of the microstructure and the mechanical properties /2—3/. The extraordinary high resistance to precipitate growth and coarsening /l/ appears to be the key property in these applications and also appears to be the origin for a unique precipitate phenomenon which was observed in the present irradiation experiment.A 1.4970 type steel (15Ni—15Cr austenite, containing Ti and C) was neutron irradiated at 845 K to a dose of 2.6 x 1025 m-2 thermal neutrons (helium production) and 3.0 x 1025 fast neutrons (1.5dpa). Before irradiation the steel was solution annealed leaving about half of the Ti and C in supersaturated solution. Defect cascades introduced by the neutron irradiation acted as nucleation centres for MC (M=Ti, Nb, Mo...) precipitates as has already previously been demonstrated in Ti- and Nb-stabilized steels /4/. In addition to the common, irregularly shaped MC precipitates, however, two further precipitate variants were created during the present high temperature neutron irradiation. One precipitate variant was star—shaped with cube—on—cube orientation relationship with the matrix. The other variant was nail—shaped. Analysis of crystal structure and orientation relationship of the nail—shaped precipitates was made difficult by their small shape and by double diffraction effects. Fig. la shows a (001) SAD pattern of matrix (heavy spots) and precipitates (fine spots). The quadruplets in the vicinity of <110> are created from the new precipitates. Each of the four quadruplet spots actually consists of three closely spaced spots (Fig. lb), and the eight precipitate spots surrounding each of the matrix spots in Fig. la each consist of two spots. After the double diffraction effects had been assigned (schematic in Fig. lb for example) they were reduced by specified specimen tilting around two axes (Fig. lc). It was found by combined dark- field and diffraction analyses that all diffraction spots originated from TiC precipitates and that four orientation variants of the TiC precipitates were distinguishable. They are imaged in Fig. 1d in bright field and in Fig. 2 in four corresponding dark field images by using reflections 0 to 3 of Fig. lc. 0 shows precipitates of the common cube—on— cube orientation relationship. 1 to 3 shows nail—shaped precipitates with nail axes pointing along the three <110> directions. The diffraction analysis revealed that the lattice of the nail precipitates is rotated by 45 degrees around the nail axes from cube-on-cube orientation, thus giving rise to the three orientation variants.
The effect of radiation-induced segregation on void swelling in electron-irradiated austenitic Fe-Cr-Ni-Ti-P Alloy
Authors: Watanabe H. , Muroga T. , Yoshida N. 
Published: June 2020

It has been reported that the void swelling in austenitic steels at higher temperatures is enhanced by a nickel depletion in matrix . The objective of the present study is to understand the effect of solute addition on void swelling, in association with microchemical changes, in austenitic steels during electron irradiation.Four types of model alloys (Fe-16Cr-17Ni, Fe-16Cr-17Ni-0.25Ti, Fe- 16Cr-17Ni-0.1P, Fe-16Cr-17Ni-0.25Ti-0.IP) and JPCA-2 were used in this study. Irradiation and in-situ observation were carried out with 1.0 MeV electrons utilizing JEM-1000 of HVEM Lab. Kyushu Univ.Fig. 1 shows the irradiation temperature dependence of nickel concentration in matrix after irradiated at 2 dpa. The ternary alloy and alloys containing phosphorus(or titanium) only show a strong nickel depletion in matrix due to nickel segregation to defect sinks. Our previous results about void swelling in these alloys showed that the temperature, where nickel depletion in matrix became prominent, corresponded to that of maxium void swelling. On the other hand, void swelling and the nickel depletion were not detected in Fe-16Cr-17Ni-0.25Ti-0.IP and JPCA-2.
“Cavity” formation in superplastically deformed aluminium alloys
Authors: Cziráki A. , Ková-csetényi E. , Torma T. , Turmezey T. 
Published: June 2020

It is known that the formation of cavities during superplastic deformation can be correlated with the development of stress concentrations at irregularities along grain boundaries such as particles, ledges and triple points. In commercial aluminium alloys Al-Fe-Si particles or other coarse constituents may play an important role in cavity formation.Cavity formation during superplastic deformation was studied by optical metallography and transmission scanning electron microscopic investigations on Al-Mg-Si and Al-Mg-Mn alloys. The structure of particles was characterized by selected area diffraction and X-ray micro analysis. The volume fraction of “voids” was determined on mechanically polished surface.It was found by electron microscopy that strongly deformed regions are formed during superplastic forming at grain boundaries and around coarse particles.According to electron diffraction measurements these areas consist of small micro crystallized regions. See Fig.l.Comparing the volume fraction and morphology of cavities found by optical microscopy a good correlation was established between that of micro crystalline regions.
Structure of a new orthorhombic phase in NiTi: Mn shape memory alloys
Authors: Beyer Jenö , Tóth Lajos 
Published: June 2020

The structural changes during reversible martensitic transformation of near-equiatomic NiTi alloys can best be studied in TEM at around room temperature. Ternary additions like Mn offer this possibility by suppressing the Ms temperature below RT. Besides the stable intermetallic phases (Ti2Ni, TiNi, TiNi3) several metastable phases with various crystallographic structures (rhombohedral, hexagonal, monoclinic, cubic) have also been reported to precipitate due to suitable annealing procedures.TiNi:Mn samples with 0.9 and 1.3 at% Mn were arc melted in argon atmosphere and homogenized at 948 °C for 72 hours in high vacuum in an infrared furnace. After spark cutting slices of 0.2 mm, TEM specimens were prepared by electrochemical polishing with the twin-jet technique in methanol - perchloric acid electrolyte. The TEM study was carried out in a JEOL 200 CX analytical electron microscope.In this paper a new intermetallic phase is reported which has been observed in both samples by TEM during the martensitic transformation process.
A HVEM study on the deformation microstructures of quartz in the fault rocks from a seismic fault zone in west china
Authors: Zhuoran Lin , Zhuen Yang , Chunping Zhou 
Published: June 2020

Our work has been aimed at the exploratory observation and study on the intracrystalline submicron deformation structures of quartz in a series of deformed rocks occurred along the Fuyun fault zone in Xinjian, West China, which is a typical seismic one with strong activities since Cenozoic period, in connection with the corresponding works on seismology and structural petrology, using the ultra high voltage electron microscope (HVEM).With the successful method of sample preparation by select area stripping from a petrographic microscopy section and ion thinning, and with the advantages of stronger penetration power and lower radiation damage of HVEM, our observation on the intracrystalline deformation microstructure has been made more reliable and productive.In the light of dislocation theory and the experimental results of quartz deformation, up to hundred of HVEM micrographs have been analysed and summarized with reference to the current conceptual model of fault.