bluuebunny/crossref_metadata_2025 huggingface dataset:
Orientation imaging microscopy: Monitoring residual stress profiles in single crystals using an image-quality parameter, IQ
Authors: Wardle S. T. , Lin L. S. , Cetel A. , Adams B. L.
Published: June 2020

Residual stresses are routinely calculated in polycrystalline materials from the residual strains determined by x-ray diffraction (XRD) analysis. Using XRD to determine residual stresses is a well-established technique, however it cannot be used for single crystals. This investigation develops a technique that readily monitors residual deformation profiles in single crystals. The technique is of particular interest to the aerospace industry as it enables the effectiveness of shot-peening single crystal turbine blades to be monitored.

Electron Back-Scattered Patterns (EBSPs) can readily be obtained from electropolished single crystals using a scanning electron microscope (SEM) in spot mode. EBSPs from cold worked metals will be of poorer quality than EBSPs from undeformed metal. Likewise the EBSPs obtained from an electropolished section cut perpendicular to a shot-peened surface will show an increase in image quality with increasing distance from the worked surface (Fig. 1). This trend could easily be monitored in single crystals by quantifying the image quality of the associated EBSPs using orientation imaging microscopy (OIM).
On the determination of stacking-fault energy from dislocation nodes observed by TEM
Authors: Ferreira Paulo J.
Published: June 2020

A fundamental understanding of the mechanical and physical behaviour of metals requires a knowledge of the stacking-fault energy (SFE). This aspect is important because the possibility of cross-slip and thus plastic deformation is a function of the SFE of the material. Impurities may segregate to the faults and change the SFE, which may affect the mechanical behaviour. For low SFE’s materials, the SFE can be determined rather accurately from transmission electron microscopy evaluation of the radius of curvature of dislocation nodes formed by the attractive interaction of dislocations (Fig. 1).

This work is directed towards applying the T.E.M. technique to determine the SFE of a 310S stable austenitic stainless steel. The specimens were observed in a JEOL 4000 microscope operated at an accelerating voltage of 200 kV, and equipped with a double tilt stage. Conventional two beam bright field images were used to determine the Burgers vector and line direction of the partial dislocations.
TEM examination of hardening and toughening phenomena in a ultrahigh-strength steel
Authors: Ayer Raghavan , Machmeier P. M.
Published: June 2020

During the development of the popular ultrahigh strength AF1410 steel, Machmeier, et.al., observed that a small variation in the chromium content had a significant improvement on the toughness of the steel in the quenched and tempered condition. The present TEM study was directed at examining the microstructural basis for this toughness enhancement.

The following samples of AF1410 type steels with two levels of chromium were examined:
Steel A: 0.16%C, 10.02%Ni, 2.97%Cr, 1.21 %Mo, 13.74%Co and bal. Fe
Steel B: 0.16%C, 10.15%Ni, 1.95%Cr, 0.98%Mo, 13.8% Co and bal. Fe.
Steel A represents the composition of AF1410 while steel B had the same base composition except for 1% higher chromium.

Figure 1 shows the strength and toughness of steels A and B when tempered in the range of 400-600°C. The yield strengths of the two steels were comparable over most of the tempering range; however, the toughness of steel B, measured by Charpy V notch impact test, was superior in the range of 482 - 538°C.
Nanoanalysis of precipitation in a modified Inconel 718 alloy
Authors: Liu J. , Dong J. X. , Chen M. Z. , Xie X. S.
Published: June 2020

The nickel-base superalloy Inconel 718 (IN718) is strengthened primarily by precipitation of two types of intermetallic phases in the austenite (γ) matrix: metastable γ' (cubic Ll2 structure) and γ" (tetragonal D022 structure) precipitates. Minor changes of the chemistry of the IN718 alloy can significantly affect its mechanical properties at high temperatures. It has been found that the microstructural stability of the precipitates and the high temperature performance of IN718 depend critically on the (Ti+Al)/Nb and Al/Ti ratios. The small sizes of these intermetallic phases and the fact that γ' precipitates are frequently associated with γ" precipitates in modified IN718 make it difficult to determine their composition. In this study, nanometer resolution analytical electron microscopy techniques have been used to characterize the structure, the morphology and the composition of the precipitated phases.

The fabrication and the heat treatment of the modified IN718 alloy and its high temperature mechanical properties have been reported elsewhere.
Alignment mark materials for projection electron lithography
Authors: Farrow R. C. , Liddle J. A. , Berger S. D. , Huggins H. A. , Kraus J. S. , Camarda R. M. , Tarascon R. G. , Fetter L.
Published: June 2020

Recent advances in projection electron lithography have led to the development of a non-imaging mark detection scheme for alignment and registration that uses backscatter electron (BSE) contrast. The detection scheme is referred to as the beamlet method and uses the measured BSE emission to detect the correct alignment condition when the image of a mask mark is scanned over a corresponding wafer mark When applied to a SCALPEL system (i.e. SCattering with Angular Limitation in Projection Electron Lithography) mark detection accuracy of better than 10 nm has been reported. Incident electrons with approximately 100 keV energy will be used in a practical SCALPEL lithography tool. In this study we compare theoretical BSE ratios with quantitative measurements in a prototype SCALPEL machine. From these results we are able to predict the suitability of materials used for conductive links in very large scale integrated (VLSI) circuits.

The theory for BSE emission from thin deposited films has been developed from work on thin self supporting films.
Quantitative HREM using non-linear least-squares methods
Authors: King Wayne E. , O’Keefe Michael A. , Campbell Geoffrey H.
Published: June 2020

Non-linear least-squares methods have been coupled with high resolution image simulation to determine the critical electron microscopic imaging parameters, such as thickness and defocus, from an experimental image. The method has been extended to include the optimization of atomic column positions and occupancy to determine atomic structure. As an example, the method has been applied to the refinement of the atomic structure of a Σ5(310)/[001] grain boundary in Nb.

In the past, high resolution electron microscopy has been applied in a primarily qualitative manner through the visual comparison of experimental images with simulated images. The potential for more quantitative analysis has been pointed out and recently, increasing attention is being given to more quantitative matching of experiment with simulation. Emphasis is being placed on the deduction of imaging parameters and/or the refinement of atomic structures from experimental images.

In this paper, we describe an approach to the optimization of the critical electron-optical imaging parameters of an experimental image and the atomic structure of a crystalline defect, namely a grain boundary.
Quantitative HREM analysis of planar defects in high-pressure synthesized infinite-layer superconductor
Authors: Zhang Hong , Marks L. D. , Wang Y. Y. , Zhang H. , Dravid V. P. , Han P. , Payne D. A.
Published: June 2020

Planar defects in the infinite-layer (Sr1-xCax)1-yCuO2 structure (planar CuO2 sheets separated by single Sr and Ca cations) have been suggested to be responsible for superconductivity with Tc up to about 110K. It is therefore important to understand the details of these defects at the atomic scale. In this work, we have used high resolution transmission electron microscopy to identify these defects and χ2 minimizations to best fit the experimental images; an optimized structure model from these studies is proposed.

Thin samples of the infinite layer superconductor with the nominal chemical formula (Sr1-xCax)1-y CuO2 (x=0 and 0.3; y=0.9, 1.0 and 1.1) synthesized by high pressure treatment were prepared using a combination of mechanical polishing, dimpling and ion milling techniques. Through focal (10 nm steps) [100] HREM images of the defects (Fig. 1) were obtained on a 300kV Hitachi H-9000 microscope. HREM image simulations were carried out using NUMIS software and these were quantitatively compared against the experimental images using conventional χ2 minimizations with SEMPER software.
HREM analysis of a Σ5 (210) grain boundary in rutile
Authors: Paciornik S. , Dahmen U. , Solorzano I. G. , Vandersande J. B.
Published: June 2020

The present investigation combines HREM with image processing and simulation to determine both the atomic and the step structure of a near-Σ5 (210) symmetrical grain boundary in TiO2 (rutile), produced by melt growth from an oriented bicrystal seed.

Figure 1a shows a HREM image of the boundary taken near -69nm defocus (dark atomic columns). The boundary makes an angle of about 5° with the horizontal symmetry plane . In this view five flat terraces separated by steps are apparent. The atomic structure within an individual terrace is shown at higher magnification in figure 2a. From this image it is clear that the terrace is a (210) 53.1° [001] symmetrical tilt boundary of the Σ5 coincident site lattice. In figure 2a two structural unit patterns are outlined. These patterns are distinctly different from either crystal and thus characteristic of the interface. To find similar units and to measure their degree of similarity and location, a cross correlation (CC) map between figure 2a and each of the patterns was calculated using a real-space template matching technique.
The determination of rigid-body translation vectors of twins with nearly common reflections
Authors: Seale D. J. , Sheinin S. S.
Published: June 2020

A method has previously been reported in the literature for determining the rigid body translation vector of a twin boundary using diffraction contrast. The technique relies on imaging the twin boundary with a reflection which is common to the two crystals on either side of the boundary. In order to completely define the rigid body translation vector, at least three such common reflections must be used. This procedure can become extremely difficult, however, in the case of crystals which have an element of pseudo-symmetry. These are crystals which have a Bravais lattice which is slightly distorted from a different Bravais lattice of higher symmetry. An example of this kind of crystal is the high temperature superconductor, Y1Ba2Cu3O7-δ. This material has a unit cell which is orthogonal, but which is only slightly different from tetragonal, with a=3.82 Å and b=3.89 Å. Crystals of this type often exhibit transformation twins which are formed when the crystal is transformed from the higher to the lower symmetry structure during cooling.
Characterization of GaAs/AlGaAs quantum wells and quantum wires by chemical lattice imaging
Authors: Carlsson A. , Malm J.-O. , Gustafsson A.
Published: June 2020

In this study a quantum well/quantum wire (QW/QWR) structure grown on a grating of V-grooves has been characterized by a technique related to chemical lattice imaging. This technique makes it possible to extract quantitative information from high resolution images.

The QW/QWR structure was grown on a GaAs substrate patterned with a grating of V-grooves. The growth rate was approximately three monolayers per second without growth interruption at the interfaces. On this substrate a barrier of nominally Al0.35 Ga0.65 As was deposited to a thickness of approximately 300 nm using metalorganic vapour phase epitaxy . On top of the Al0.35Ga0.65As barrier a 3.5 nm GaAs quantum well was deposited and to conclude the structure an additional approximate 300 nm Al0.35Ga0.65 As was deposited. The GaAs QW deposited in this manner turns out to be significantly thicker at the bottom of the grooves giving a QWR running along the grooves. During the growth of the barriers an approximately 30 nm wide Ga-rich region is formed at the bottom of the grooves giving a Ga-rich stripe extending from the bottom of each groove to the surface.
Verification of sub-Å information transfer and its influence on the precision of structure determination by quantitative HRTEM
Authors: Möbus G. , Phillipp F. , Rühle M.
Published: June 2020

Using quantitative diffractometry from a micrograph of an amorphous germanium film, the total contribution to the chromatic damping envelope by focus spread could be determined for a high-voltage ultra-high-resolution microscope operating at 1250kV. The major difficulties of quantification beyond the usual analysis of the zero crossings of the diffractograms are the proper correction for scattering factor, modulation transfer function, background and noise. Nonlinear imaging, inelastic scattering and depth of focus of thick specimens are considered to be minor effects at high voltages. The Fourier transform of a hyperbolic astigmatic image can be converted into a Thon diagram (or contrast transfer nomogram) using a special (modified polar-to-cartesian) coordinate transformation The resulting Thon diagram of Fig. la shows the weak phase contrast transfer as a function of spatial frequency (horizontal axes) and defocus (vertical axes). Diffractogram maxima can be seen out to 0.97 Å. A focus spread of Δ = 10nm could be determined by fitting the experimental to calculated Thon diagrams (Fig. 1 b).
Investigations on electric charging by electron holography
Authors: Frost B. , Joy D. C. , Voelkl E.
Published: June 2020

The electric charging of latex spheres was investigated by electron holography using a Hitachi HF-2000 field emission electron microscope. In order to get fringe spacings smaller than 1/20 of the diameter of the spheres (0.264 μm and 2.68 μm) and interference widths of at least twice the sphere diameter, we used different magnification modes. The low magnification mode was achieved by switching off the objective lens and imaging the specimen by the intermediate lens. For higher magnifications the specimen was imaged by the objective lens which operated as an electron optical magnifier, i.e. the front focal plane was situated above the specimen.

For easiest interpretation of the reconstructed phase distributions, a high symmetry of the sample is of advantage. Therefore we eliminated any unknown electric interaction between a supporting film and the charged sphere by placing the sphere at the edge of a bar of the copper grid. In that case the charge image method can be used as a simple model to evaluate the distribution of the electric potential.
Electron Microscopy Studies of The Chemistry And Microstructure of BaF2 / YBa2Cu3O7-x Thin Films
Authors: Lee J. L. , Weiss C. A. , Buhrman R. A. , Silcox J.
Published: June 2020

BaF2 thin films are being investigated as candidates for use in YBa2Cu3O7-x (YBCO) / BaF2 thin film multilayer systems, given the favorable dielectric properties of BaF2. In this study, the microstructural and chemical compatibility of BaF2 thin films with YBCO thin films is examined using transmission electron microscopy and microanalysis. The specimen was prepared by using laser ablation to first deposit an approximately 2500 Å thick (0 0 1) YBCO thin film onto a (0 0 1) MgO substrate. An approximately 7500 Å thick (0 0 1) BaF2 thin film was subsequendy thermally evaporated onto the YBCO film.

Images from a VG HB501A UHV scanning transmission electron microscope (STEM) operating at 100 kV show that the thickness of the BaF2 film is rather uniform, with the BaF2/YBCO interface being quite flat. Relatively few intrinsic defects, such as hillocks and depressions, were evident in the BaF2 film. Moreover, the hillocks and depressions appear to be faceted along {111} planes, suggesting that the surface is smooth and well-ordered on an atomic scale and that an island growth mechanism is involved in the evolution of the BaF2 film.
The stability of dislocation networks under various oxygen-doping conditions in superconducting Bi2Sr2CaCu2Oy single crystals and their influence on the flux pinning properties
Authors: Feng Y. , Cai X. Y. , Kelley R. J. , Larbalestier D. C.
Published: June 2020

The issue of strong flux pinning is crucial to the further development of high critical current density Bi-Sr-Ca-Cu-O (BSCCO) superconductors in conductor-like applications, yet the pinning mechanisms are still much debated. Anomalous peaks in the M-H (magnetization vs. magnetic field) loops are commonly observed in Bi2Sr2CaCu2Oy (Bi-2212) single crystals. Oxygen vacancies may be effective flux pinning centers in BSCCO, as has been found in YBCO. However, it has also been proposed that basal-plane dislocation networks also act as effective pinning centers. Yang et al. proposed that the characteristic scale of the basal-plane dislocation networksmay strongly depend on oxygen content and the anomalous peak in the M-H loop at ˜20-30K may be due tothe flux pinning of decoupled two-dimensional pancake vortices by the dislocation networks. In light of this, we have performed an insitu observation on the dislocation networks precisely at the same region before and after annealing in air, vacuumand oxygen, in order to verify whether the dislocation networks change with varying oxygen content Inall cases, we have not found any noticeable changes in dislocation structure, regardless of the drastic changes in Tc and the anomalous magnetization. Therefore, it does not appear that the anomalous peak in the M-H loops is controlled by the basal-plane dislocation networks.
TEM study of surface modification of sapphire by pulsed-laser irradiation
Authors: Cao Siqi , Pedraza A. J. , Allard L. F.
Published: June 2020

The mechanical strength of a metal-ceramic couple is primarily determined by the bonding force developed at the interface. The nature and magnitude of these forces depend upon the characteristics of the couples as well as the deposition process. In particular, noble metals show very poor adhesion onsapphire substrates in the as-deposited condition. However, the bonding of a metal-ceramic couple canbe improved by various surface modification methods such as laser irradiation and ion bombardment. Pedraza et al. studied the adhesion enhancement of metallic films ion-beam sputter-deposited on ceramicsubstrates. It was found that a very strong increase in the adherence of the metallic films could be achieved if the substrate had been laser-irradiated prior to film deposition. In this paper, the interfacial microstructure of cross-sectional samples of Au films deposited on laser irradiated sapphire was examined by TEM in order to gain some insight into the bonding mechanisms of these couples.

Optically polished c-axis sapphire substrates were laser-irradiated in air with twenty sequential pulses of 3 J/cm2 each.
The role of atom-probe field ion microscopy in alloy development and phase transformation studies
Authors: Miller M. K. , Jayaram R. , Russell K. F.
Published: June 2020

One of the important parameters in the design of new materials is the distribution of the alloyingelements in the microstructure and whether these elements are involved in the formation of precipitates or in segregation to internal interfaces such as grain boundaries. The atom probe field ion microscope is an extremely effective tool for these types of fine scale characterizations. Recently, therehas been a large effort to develop new, more efficient materials for high temperature applications such as gas turbines. A candidate material for this application is NiAl. However, the low temperature ductility of NiAl is extremely small and hinders fabrication. Therefore, attempts have been made to alleviate these problems with the use of microalloying additions such as boron. The atom probe has beenused to determine the location of boron in the microstructure and correlate its distribution with themechanical properties. Atom probe analyses have revealed that the solubility of boron in NiAl is extremely low and most of the excess boron is precipitated in the form of ultrafine MB2 precipitates as shown in Fig. 1. In addition, boron segregation to the grain boundaries has been observed, Fig. 2. Theobserved increase in the yield strength is therefore primarily due to a precipitation hardening mechanism with a contribution from solid solution hardening and this offsets the beneficial effect of the boron at the grain boundaries.
Structural analysis of TiN/Si and TiN/GaAs epitaxial systems by TEM and multi-slice simulation
Authors: Zheleva Ts. , Jagannadham K. , Iamakov V. , Narayan J.
Published: June 2020

Low resistivity and diffusivity of epitaxial films of TiN (a=4.24Å) on Si (a=5.43Å) and GaAs (a=5.65Å) make these films excellent choice as barrier layers in VLSI metalization. Epitaxial structural relationships at the interface in large mismatch systems, such as TiN/Si and TiN/GaAs were investigated by transmission electron microscopy, and multi-slice simulation technique. Studies wereperformed on TOPCON 002B high resolution microscope operated at 200 kV, with resolution limit at 1.8Å. Computer simulations with image processing was carried out on IBM/PC-AT computer incombination with IBAS/IPS image processing system of KONTRON electronic group. Epitaxial (100)TiN films on Si(100) and (110)TiN films on GaAs(100) have been deposited by laser physical vapor deposition.From the SAED patterns the orientation relationships have been found to be cube-on-cube for the TiN/Si interface i.e. <100>TiN//>100>Si (Fig.l); and [001]TiN//[110]GaAs and [10]TiN//[10]GaAs (Fig.2a,b). The analysis of the diffraction data for the TiN/GaAs interface reveals that TiN unit cell is rotated twice by 45° - with respect to [001] GaAs and with respect [110] GaAs (Fig.3). Thus the coordinates of the TiN unit cell axes a', b', and c' are expressed in the bases of GaAs axes a,b,c as: a'= -0.375a + 0.375b + 0.531c; b'= 0.375a - 0.375b + 0.531c; and c'= 0.531a + 0.531b.
Behavior of contact-silicided TFSOI gate structures
Authors: Theodore N. David , Foerstner Juergen , Fejes Peter
Published: June 2020

As semiconductor device dimensions shrink and packing-densities rise, issues of parasitic capacitance and circuit speed become increasingly important. The use of thin-film silicon-on-insulator (TFSOI) substrates for device fabrication is being explored in order to increase switching speeds. One version of TFSOI being explored for device fabrication is SIMOX (Silicon-separation by Implanted OXygen).A buried oxide layer is created by highdose oxygen implantation into silicon wafers followed by annealing to cause coalescence of oxide regions into a continuous layer. A thin silicon layer remains above the buried oxide (~220 nm Si after additional thinning). Device structures can now be fabricated upon this thin silicon layer.Current fabrication of metal-oxidesemiconductor field-effect transistors (MOSFETs) requires formation of a polysilicon/oxide gate between source and drain regions. Contact to the source/drain and gate regions is typically made by use of TiSi2 layers followedby Al(Cu) metal lines. TiSi2 has a relatively low contact resistance and reduces the series resistance of both source/drain as well as gate regions
Oxide-induced deterioration of TiSi2 source/drain MOSFET contacts
Authors: Theodore N. David , Ilderem Vida , Pan Ming
Published: June 2020

A simple process for formation of a metal-oxide-semiconductor field-effect transistor (MOSFET) involves fabrication of a polysilicon/oxide gate between source and drain regions. Contact is made to source/drain regions by use of TiSi2 layers followed by Al(Cu) metal lines. A silicide layeris used toreduce contact resistance. TiSi2 is chosen as a contact layer because in the C54phase, the silicide has a lower resistivity (~12 μΏ-cm) than most other silicides (except for CoSi2 ~10-15 μΏ-cm). During formation of TiSi2 contact layers to MOSFET source/drain regions, a deterioration of the TiSi2 is occasionally observed. The deterioration typically consists of buckling and delamination of Ti(TiSi2) films from the source/drain regions. When buckling occurs, electrical contact between Al metal and MOSFET source/drain regions is quite poor. The present study investigates the microstructure and behavior of TiSi2 contact layers used at source/drain regions of MOSFETs. The cause of deterioration of contact-layers is investigated and a potential solution to this problem is explored.
Microstructure and contact-resistance temperature dependence of Pt/Ti/Ge/Pd ohmic contacts to GaAs
Authors: Cole M. W. , Han W. Y. , Eckart D. W. , Casas L. M. , Jones K. A.
Published: June 2020

The development of GaAs device technology has demonstrated the need for fabrication of low resistance thermally stable ohmic contacts. Gold based contacts have been the overwhelming choice for ohmic contacts in device applications. In particular, Au/Ge/Ni and Zn/Au alloyed contacts have been used for n and p-GaAs respectively. Numerous investigations have shown that Au-based contacts to GaAs have avery complex morphology after annealing. Specifically, structural interface inhomogeneities, such as protrusions and newly formed lateral interface phases lead to non-planar metalsemiconductor interfaces which in turn cause nonuniform current flow and consumption of the GaAs substrate. This type of interface morphology is not acceptable for device applications where a large electrical field or a shallow contact is required. In particular, devices such as heterojunction bipolar transistors (HBT's) cannot tolerate contacts with lateral and vertical interface inhomogeneities.This study employed crosssectional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and electrical measurements (transmission line mode), to systematically investigate the structural, chemical and electrical properties of the Pt/Ti/Ge/Pd contacts to both n and p+ GaAs as a function of annealing temperatures.
Morphology and development of flow-pattern defect with extended nonagitated Secco etching
Authors: Pan Y.
Published: June 2020

The D defect, which causes the degradation of gate oxide integrities (GOI), can be revealed by Secco etching as flow pattern defect (FPD) in both float zone (FZ) and Czochralski (Cz) silicon crystal or as crystal originated particles (COP) by a multiple-step SC-1 cleaning process. By decreasing the crystal growth rate or high temperature annealing, the FPD density can be reduced, while the D defectsize increased. During the etching, the FPD surface density and etch pit size (FPD #1) increased withthe etch depth, while the wedge shaped contours do not change their positions and curvatures (FIG.l).In this paper, with atomic force microscopy (AFM), a simple model for FPD morphology by non-crystallographic preferential etching, such as Secco etching, was established.

One sample wafer (FPD #2) was Secco etched with surface removed by 4 μm (FIG.2). The cross section view shows the FPD has a circular saucer pit and the wedge contours are actually the side surfaces of a terrace structure with very small slopes. Note that the scale in z direction is purposely enhanced in the AFM images. The pit dimensions are listed in TABLE 1.
Microstructural and magneto-optical characterization of ferrimagnetic multilayered thin-film rare-earth iron garnet heterostructures
Authors: Simion B. M. , Ramesh R. , Marinero E. , Pfeffer R. L. , Thomas G.
Published: June 2020

The continuous demands of the computer industry for increased reliability, portability, and density of storage media, has opened a new chapter in the magnetic recording research, by focusing on the viability of magneto-optical materials for storage. Several materials are considered presently to be at the forefront of this new quest: ternary rare-earth transition-metal alloys (such as GdTbFe or TbFeCo), garnets, and Co/Pt or Co/Pd mutilayers. Of these, the ferrimagnetic garnets, due to their relatively flexible structure, may accommodate a large number of substituting ions, allowing thus for a very good control of their magnetic and magneto-optical properties. The good results obtained during thegrowth of epitaxial superconducting oxide thin films by pulsed laser deposition (PLD), has encouragedus to try this novel deposition technique in the growth of multilayered heteroepitaxial ferrimagneticiron garnet thin films.

Superlattice heterostructures consisting of alternating single crystalline ferrimagnetic yttrium-iron-garnet (YIG) and bismuth-iron-garnet (BIG) thin film layers, as well as alternating YIG and europiumsubstituted BIG (EBIG), were deposited on single crystalline (111) paramagnetic gadolinium-galliumgarnet (GGG) substrates.
Automatic/interactive bead alignment in electron tomographic image processing
Authors: Liu Weiping , Fung Jennifer , Abbey Craig , Sedat John W. , Agard David A.
Published: June 2020

In the electron tomographic (EM) reconstruction process the mutual alignment between projections of different view angles is a crucial step. The routinely used alignment method is based on fiducial markers': a single-axis tilt projection series is collected with gold particles distributed on the specimen, the positions of high density gold beads on the projections are found, and the relationship between the specimen and the digital projection coordinate systems is determined from least-square fitting these found bead positions. There are four alignment parameters for each projection: two in shifts, one in in-plane rotation, and one in magnification. In the threedimensional studies of subcellular biological structures, we routinely collect data sets of more than 100 projections in the tilt range of ±75 ° with our automated EM set-up. Normally around 10 bead positions are used on each projection to achieve the alignment. Bead alignment used to be a laborious task since approximately 1000 bead positions need to be hand-picked for each data set.
Energy-filtering Transmission Electron Microscopy in materials and life science
Authors: Reimer L.
Published: June 2020

Energy-filtering transmission electron microscopy can be realized by an imaging filter lens in thecolumn of a TEM, a post-column electron energy-loss spectrometer or a dedicated STEM. This offers new possibilities in analytical electron microscopy by combining the operation modes of electron-spectroscopic imaging (ESI), electron-spectroscopic diffraction (ESD) and the record of an electron energy-loss spectrum (EELS).

ESI can be used in the zero-loss mode to remove all inelastically scattered electrons. Thicker amorphous and crystalline specimens can be observed without chromatic aberration and with a transmissionof 10−3 up to 80(110) and 150(200) μg/cm2 at 80(120) keV, respectively. This results in a condiserable increase of scattering, phase and Bragg contrast, especially for low Z material because the ratio of inelastic-to-elastic cross section increases as 20/Z with decreasing atomic number. In future energy-filtered high-resolution crystal-lattice images will offer us a better comparison with dynamical simulations. Plasmon loss filtering can be applied for a better separation of phases (e.g. precipitates in a matrix), which differ in their plasmon loss by about 1 eV. Owing to intersections of the energy loss spectra, different parts of a specimen can change their contrast when tuning the selected energy window. Structures containing non carbon atoms will beconsiderably increased in a bright field like contrast relative to the carboneous matrix just below the carbon K edge (structure—sensitive imaging).
Atomic-resolution characterization of an SrTiO3 grain boundary in the STEM
Authors: McGibbon M. M. , Browning N. D. , Chisholm M. F. , McGibbon A. J. , Pennycook S. J. , Ravikumar V. , Dravid V. P.
Published: June 2020

High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted intuitively without the need for preconcieved atomic structure models. Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale. The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface. In this paper we use the complimentary techniques of high resolution Z-contrast imaging and PEELS to investigate the atomic structure and chemistry of a 25 degree symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.

Figure 1(a) shows a Z-contrast image of a symmetric region of the tilt boundary. The brightest spots in the image correspond to the increased scattering power of the Sr atomic columns (Z=38) with theless bright spots corresponding to the Ti atomic columns (Z=22). The lighter O atomic columns are notvisible in a Z-contrast image.
Correlative microscopy of colloidal gold-labeled and unlabeled cell-surface-associated molecules: LV-SEM, SEM, and VLM
Authors: Albrecht R. M. , Simmons S. R. , Eppell S. J. , Marchant R. E.
Published: June 2020

Video enhanced, interference based light microscopy (VLM) is sufficiently sensitive to permit observation, via the inflated diffraction image, of colloidal gold particles as small as 15nm. These particles can be directly coupled to ligands such that ligand binding, distribution, and ligand-receptor complex movement can be observed on living cells (Fig.1a-d) and correlated subsequently with HVEM and/or SEM images of the same cell (Fig. 1e). The size of the gold particles used in these studies is such that, other than for very large ligands, generally two or more ligand molecules are bound per particle. Thus questions regarding the role of the polyvalent “particle” (ligand-gold conjugate) vs. soluble ligand can arise. Observation of individual labeled or unlabeled ligand molecules can therefore become useful in resolving such questions when they occur.
Epitaxial growth manner and structure of superconducting oxide films
Authors: Bando Yoshichika , Terashima Takahito , Iijima Kenji , Yamamoto Kazunuki , Hirata Kazuto , Hayashi Katsuhiko , Kamigaki Kousei , Terauchi Hikaru
Published: June 2020

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.
Oxygen-related defects in YBa2Cu3O7-δ
Authors: Van Tendeloo G. , Amelinckx S.
Published: June 2020

Structural defects associated with the ordering of oxygen in YBa2Cu3O7−δ are discussed. The simplest among these phenomena is the twinning resulting from the tetragonal to orthorhombic phase transition. The geometry and the mechanism of twin formation have been studied “in situ” in the electron microscope. From detailed high resolution observations (fig.1,2), it is possible to propose models for twinning dislocations (see fig.3). Ordering stresses resulting from the T-O transformation induce a “synchro-shear” glide motion of such dislocations along twin interfaces, causing hereby a latteral shift (see fig.3). The model also leads to an atomic mechanism for the detwinning of crystals under uniaxial compressive stress. Sharp as well as diffuse twin boundaries are observed, depending on composition and thermal history of the sample. It is shown by Monte Carlo simulations based on a two dimensional anisotropic Ising model that the concentration of oxygen ions in the CuO1−x layers exhibits a minimum in the region adjacent to the twin interface. The vacancy enriched region is more pronounced at low temperature and disappears at high temperature.
Twinning and oxygen ordering in Ba2YCu3O7−x crystals
Authors: Iijima Sumio , Ichihashi Toshinari
Published: June 2020

Formation of twins in Or-BYCO crystals was studied by transforming them to T-phase by electron beam irradiation in the microscope. It is known that during the transformation the crystals developed twinning (STW), Ortho-II phase (1×2 superstructure), tweed structure. These structures occur in that order by the irradiation and the structural changes are caused by oxygen deficiency and oxygen atoms ordering. This work is aimed at elucidation of oxygen atom ordering by examining the structural evolution in terms of morphologies of the twins.

Atypical evolution of an Or-BYCO crystal is shown in a series of micrographs in Figs. 1 to 5. As-grown twin (FTW) boundaries have a characteristic lens shape extending in the < 110> direction and terminate at a twin boundary in horizontal direction (Fig.1). These boundaries don't accompany strain contrast which is developed in the crystal after a brief irradiation (Fig.2). The strain contrasts, which are differentiated easily from the thickness contrast, appear parallel to the boundaries and change slowly across the boundaries.
TEM study of a laser ablated YBa2Cu3O7−x thin film on MgO substrate
Authors: Traeholt C.
Published: June 2020

Since the high Tc superconductors were discovered, the most common compounds have been investigated in detail. This work has mainly been done on bulk specimens. Now as the preparation of these high Tc superconductors is well controlled with respect to the common compounds, thin films become of major interest. In order to study the film—substrate interface cross-sectional specimens for TEM have here been prepared and investigated considering the process of image formation.

Thin films, about 100 nm thick, were laser ablated onto a single crystal MgO substrate. This was done in an oxygen atmosphere and with a rotating target of stoichiometric YBa2Cu3O7−x. The subsequent X—ray analysis showed what was believed to be an epitaxially grown film, with its c—axis only deviating a few degrees from the substrate normal. The a— and b—axes of the film were oriented parallel to the <100> directions of the substrate, in spite of a lattice mismatch (YBa2Cu3O7−x a = 3.82 Å, b = 3.89 Å, c = 11.68 Å; MgO a = b = c = 4.2 Å).
Crystallographic studies on single crystals of doped and undoped Bi-Sr-Ca-Cu-O superconductors
Authors: Krause Brigitte H. , Chang Y. C. , Jiang P. Z. , Lam D. J.
Published: June 2020

Diffraction data on single crystals of low Tc phase of Bi-Sr-Ca-Cu-O superconductor indicated a well developed layer structure, but with structural and chemical disorder within the layers. The lattice constant c and the layer sequence for the pseudo-tetragonal unit cell were determined from x-ray diffraction measurements of the 006 reflections. They were found to be 30.84(2) Å for the undoped compound and the same 30.84(2) Å for the lead doped crystals indicating the low superconducting transition temperature (Tc = 80 K) phase. The c-dimension for single crystals doped with both antimony and lead was 29.02(5) Å. Polycrystalline samples of that compound on the other hand formed the high temperature (Tc = 107 K) modification with c = 36.9(6) Å, determined from electron diffraction. A mixture of phases with different stacking of layers was indicated by splitting of diffraction spots. The direction of c was also less well defined in the lead-antimony doped single crystals than in the other two compounds.
HRTEM observation of the phase transition from Bi2Sr2CaCu2O8 to Bi2Sr2Ca2Cu3O10
Authors: Wen Shulin , Ernst F. , Jaeger H. , Mader W. , Majewski P. , Marie M. , Petzow G. , Rühle M.
Published: June 2020

The investigation of the phase transiton from Bi2Sr2CaCu2O8 (2212) to Bi2Sr2Ca2Cu3O10 (2223) in the system of Bi — Sr — Ca — Cu — O is of interest both from a theoretical and a practical point of view. The result from this investigation may probably lead to a successful pure 2223 phase preparation. The preparation of pure 2223 phase with a simple and satisfactory method still remains a problem although many efforts have been made recently to produce a large percentage of 2223 phase.

In order to produce pure 2223 phase most efficiently, the investigation of the transition mechanism from the 2212 to the 2223 phase is necessary. Using a JEM4000EX high resolution transmission electron microscope (HRTEM)we observed this phase transition process at atomic level. The following equation describes the phase transition from 2212 to 2223:
The HREM observation of the boundary between YBCO thin film and substrate
Authors: Liu W. , Wang Y. G. , Li L.
Published: June 2020

It is a very important problem to obtain high critical current density Jc in high critical temperature Tc superconductors. For high Tc thin film superconductors, the Jc value can reach >106 A/cm2 at 77K. We have prepared YBa2Cu3Oy (YBCO) thin films by magnetron sputtering method, the Jc values ranged from 104 -106 A/cm2, the films were deposited both on (100) SrTiO3 and (100) LaAlO3 substrates. It is well known that Jc is closely related to the microstructure of the film, in this paper we report the observation by high resolution electron microscopy of the boundary between film and substrate and analysis the result with relation to the Jc values of the films.

The cross sectional specimens of the film and substrate boundary were
prepared by cutting the film-substrate sample into thin slices, then
stick the slices with film surface face to face by epoxy resin.
Recent progress in the Electron Microscopic studies of Sb and Pb doped Bi-Sr-Ca-Cu-O system
Authors: Fan Chenggao , Yang Li , Xu Qinlun , Cheng Tingzhu , Zhou Guien , Wang Xueqin , Zhang Yuheng
Published: June 2020

Since 132K superconductivity in Sb and Pb doped Bi-Sr-Ca-Cu-O system was discovered by H.B.Liu et al, the experimental phenomenon has been repeated by many research groups in the world. It is well known that there always coexist several phases in such superconductors. Researchers in our university have attempted to find out which phase takes the responsibility for the high Tc transition by using different preparation methods, varying mixture ratio, changing heat treatment condition. In this contribution,some recent progress in the studies of Sb and Pb doped Bi-Sr-Ca-Cu-O system by electron microscope is presented.

An unknown phase is always observed in the Sb and Pb doped Bi-Sr-Ca-Cu-O system.TEM images show that fractures of the phase are quite thick,but they can give sharp electron diffraction patterns accompanying with Laue Zone,and they contain little Cu and Pb which are hardly detectable by EDS. A nearly pure 110K phase specimen was prepared by Qinlun Xu et al, using codeposition of coprecipitated oxalats technique, Only two kinds of fractures have been observed in this sample by TEM, One appeared thin,another thick and small.It was difficult to take series electron diffraction patterns of the latter one, which had been proved to belong to the unknown phase. Considering the preparation condition,the presence of Sb and Pb served to enhance the formation of 80K phase to 110K phase.
In-situ observation of superstructure transformation in Gd2CuO4crystals at elevated temperatures
Authors: Chen C. H. , Cheong S-W. , Werder D. J.
Published: June 2020

Recently, a commensurate superlattice modulation characterized by a wave vector of= (l/4, l/4, 0) was observed in both pure Nd2CuO4and electron-doped Nd2CuO4−xFx/Nd2−xCexCuO4compounds. The orthorhombic superlattice phase was found to exist in four possible variants with its c-axis parallel to the four equivalent zone-axes of the underlying tetragonal lattice. The origin of this modulation which is commonly observed in the beginning members of the rare-earth-based T' —214 compounds is not yet known. Gd2CuO4which represents the end member to this series has shown to exhibit anomalous magnetic properties.The present study was undertaken to investigate the superstructure in Gd2CuO4single crystals.

Thin plate-like crystals of Gd2CuO4were grown from PbO- and CuO-based flux. TEM samples were prepared by ion-milling with a liquid-nitrogen-cooled sample holder.In-situheating experiments were carried out in a JEOL 2000FX electron microscope equipped with a Gatan hot stage.
HRTEM simulation of amorphous materials
Authors: O’Keefe Michael A. , Sattler Margaret L.
Published: June 2020

Image simulation has become one of the preferred techniques for analysis of high-resolution transmission electron micrographs, in both bright-field and dark-field modes. This is especially true of microscope images used in stuctural studies, both for perfect crystal structures, and for defects within periodic structures. In using image simulation for structural analysis, comparison is made point-by-point (pixel by pixel) between the experimental image and one simulated under identical imaging conditions for a model structure. Comparison with a matching simulated image enables features in the experimental image to be identified as belonging to structural features in the specimen, such as groups of atoms, or individual atoms. In the case of amorphous structures, however, no such one-to-one correspondence between simulations and experimental high-resolution images can be expected. It is thus much more difficult to determine whether the model from which one is simulating images really does describe the appropriate amorphous structure. Amorphous structures are characterized not in terms of atom positions within a well-defined unit cell, but interms of a “radial distribution function” (RDF), a function that gives the average number of atoms lying at any given distance from an average atom. The RDF is thus a non-periodic Patterson function, and a single RDF can arise from many different arrangements of atoms, provided only that atomic positions within the structure have the “right” statistical distribution.
Structure of carbon in SCS-6 fibers
Authors: Ning X. J. , Pirouz P.
Published: June 2020

SCS-6 is a high strength (≈3950 MPa), high tensile modulus (≈400 GPa), low density (≈3050 kg/m3) commercial SiC fiber which is of considerable interest as a reinforcement in metal- and ceramic-matrix composites. The microstructure of this fiber has been recently studied in detail by TEM. The fiber microstructure is complicated and consists of an inner coating of carbon and four distinct layers of SiC all deposited on a carbon filament by CVD. In the coated SCS-6 fibers, three sub-layers of carbon, with a total thickness of ≈3μm, containing different densities of SiC particulates, cover the outermost SiC layer. In this paper, the microstructure of the carbon core (filament), the inner carbon coating and the outermost carbon sub-layers are discussed.

Cross-sectional TEM specimens were prepared from as-received SCS-6 fibers. Fig. 1 shows a SEM micrograph of the fiber which has a total thickness of 142 μm. A high resolution electron micrograph (HREM) and an electron diffraction pattern (EDP) of the carbon core - of diameter 33 μm - is shown in Fig. 2. Both the HREM micrograph and the EDP are consistent with an assembly of Basic Structure Units (BSUs). A BSU is a small block of parallel graphitic planes stacked in a random manner about a common (c-) axis. The bonding in each plane is of the strong sp type which contrasts with the weak Van der Waals bonding between the planes.