bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mapping of the potential at the end of buckytubes by electron holography
Authors: Lin X. , Dravid V. P. 
Published: June 2020

Measuring the surface and mean inner potential at the end of buckytubes will offer a lot of information about their physical and chemical properties. Such properties are closely related to fundamental mechanisms of the growth of the buckytubes that grow on the cathode with their axes aligned along the direction of the electric field (1), implicating the presence of the field in the formation mechanism.Direct observations of surface and inner potential distribution at nanometer level by electron holography were reported in several cases (2). Holography is the only imaging technique that can retrieve the phase of the electron wave, which directly related to the surface and inner potential. In this contribution, electron holography was employed to obtain the mapping of the phase of the electron wave traveled through the end of nanotubes.The holograms were recorded on negatives using a Hitachi HF-2000 with a cold emission gun, operated at 200kv.
Electron and scanning probe microscopies in the study of YBa2Cu3O7 thin-film growth
Authors: Norton M. Grant , Biggers Rand R. , Maartense Iman , Moser E. K. , Brown Jeff L. 
Published: June 2020

Electron and scanning probe microscopies are used to examine the microstructure and surface topography of YBa2Cu3O7 (YBCO) thin films formed by pulsed-laser deposition (PLD). A major emphasis of this work has been the correlation of the observed microstructural features and the deposition parameters.The formation of microscopic features on the surface of thin films deposited by PLD seems to be an undesirable and almost unavoidable feature of this process. One such feature is often associated with microstructural changes produced in the target during laser irradiation. These are apparently spherical particles with diameters ranging from 0.1 to 10μm. These particles are produced by melting of the target and the subsequent solidification of the molten ejecta. Particles may also be produced as a result of changes in the surface morphology of the target during laser irradiation. However, notall surface features observed on the films deposited by PLD are due to ejecta from the target. Figure 1 shows an atomic force microscope (AFM) image of a YBCO film grown on a (100)-oriented LaAlO3 substrate. Usually films grown with our typical deposition conditions on (100)-oriented LaAlO3 substrates arepredominantly c-axis oriented. The film is approximately 150 nm thick. Different types of outgrowth are visible on the film surface.
Extraction replicas for the analysis of second phases in nonferrous alloys using Analytical Electron Microscopy
Authors: Carpenter G. J. C. , Ng-Yelim J. 
Published: June 2020

The technique for extracting second-phase particles from steels onto a carbon support film for analysis in the transmission electron microscope (TEM) has been in continuous use since its development by Bradley, nearly 30 years ago. However, the availability of EDX and EELS accessories, capable of giving chemical information, has provided an incentive for the technique to be used with other alloys.The purpose of this presentation is to review some applications of extraction replication to non-ferrous alloys.Briefly, extraction involves chemically etching only the matrix phase of an alloysothat second-phase particles stand proud and can be extracted onto a carbon film. The most straightforward procedure is to make a single-stage direct-carbon replica, where carbon is evapourated onto the etchedsurface of a mctallographic specimen and subsequently stripped by further etching.An alternative approach is the two-stage technique, where the particles are first stripped from an etched specimen using a plastic film, e.g. cellulose acetate, such as "Bioden". The plastic surface containing theparticles is then coated with a layer of carbon, typically 10˜20nm thick, and the plastic is dissolved, leaving the particles attached to the carbon film. Although the two-stage technique involves anextra operation, it has some advantages. In particular, it is possible to strip films after differentdegrees of etching, without the necessity to re-polish the specimen. Also, with the single-stage technique, an etchant suitable for removing the replica may react so strongly that the thin carbon film breaks up during stripping.
EM of mechanical plated Zn coating on steel
Authors: Chiou W. A. , Lin C. S. , Liu P. C. , Meshii M. 
Published: June 2020

Zn and Fe-Zn alloy coatings on steel have been widely used for various applications due to their excellent corrosion resistance. The coatings are usually applied by electroplating or hot-dipping in molten Zn, but the mechanical plating process has also been used commercially and has been found advantageous over the conventional coating technologies in some applications with special requirements. The recent progress in investigating mechanically alloyed metals revealed interesting structural features including the formation of nanocrystalline and amorphous structures. Since the microstructures of electroplated and hot-dipped Zn coatings have been studied, and are known to be different from those of mechanically milled, the different properties of mechanically plated coating must be due to different microstructure. As no microstructural information is available in literature, this research project has been undertaken, along with a study of mechanical properties.Samples of commercially produced (Johnson Matthey Co.) fine-grained (325 mesh, or 44 (a.m) Zn (99.9%)flakes (1.1 μ m thick) were used as the coating materials.
Simulation and reconstruction of light-microscope images
Authors: Sheppard C. J. R. , Gu M. , Sheridan J. T. , Connolly T. J. 
Published: June 2020

Simulation of light microscope image assists in interpretation and allows comparison of different imaging techniques and their associated parameters. Further, reconstruction of specimen properties from images can in some cases be feasible.Imaging methods can be broadly divided into fluorescent and non-fluorescent techniques, the latterconsisting of brightfield transmission or reflection modes, darkfield or various phase contrast modes. The distinctive feature of these non-fluorescent modes is that they image the material properties of the specimen, including refractive index, absorption coefficient or birefringence. Sometimes the specimen is labelled with a stain, the concentration of which mirrors the concentration of a particularconstituent. In fluorescence microscopy, usually a fluorochrome is used to label particular components or constituents.In non-fluorescent microscopy, images can be simulated using rigorous diffraction methods, such asmodal analysis or coupled wave theory. Such theories take into account multiple scattering, shadowingeffects and also depletion and aberration of the light as it penetrates the object.
Interactive multiple area spectrum integration (MASI)
Authors: Hunt John A. , Leapman Richard D. , Williams David B. 
Published: June 2020

Interactive MASI involves controlling the raster of a STEM or SEM probe to areas predefined byan integration mask which is formed by image processing, drawing or selecting regions manually. EELS, x-ray, or other spectra are then acquired while the probe is scanning over the areas defined by the integration mask. The technique has several advantages: (1) Low-dose spectra can be acquired by averaging the dose over a great many similar features. (2) MASI can eliminate the risks of spatial under- or over-sampling of multiple, complicated, and irregularly shaped objects. (3) MASI is an extremely rapid and convenient way to record spectra for routine analysis. The technique is performed as follows:Acquire reference imageOptionally blank beam for beam-sensitive specimensUse image processor to select integration mask from reference imageCalculate scanning path for probeUnblank probe (if blanked)Correct for specimen drift since reference image acquisition
High-resolution SEM of biological macromolecular complexes
Authors: Wepf R. , Aebi U. , Bremer A. , Haider M. , Tittmann P. , Zach J. , Gross H. 
Published: June 2020

For HRSEM imaging of insulating specimens, thin “homogeneous” metal films with a thickness smaller than the SE-escape depth (1-2 nm for metals) and with a neglectable or very low BSE-coefficient (low Z e.g. Cr or Ge), continuous enveloping the surface fine structures, are supposed to reveal a high resolution topographic SE-1 signal (Joy 1984). Hermann and Müller (1991) have reported a resolution of about 3-4 nm on freeze-dried thin biological specimens, coated with Cr at low temperature (−80°C). High resolution SE-images were also shown on ft or W sputter coated, frozen-hydrated yeast cells (Walther et al., 1992 and Hermann and Müller, 1993) and on coated, freeze-dried macromolecular structures (Walther et al. 1992; Ya Chen et al. 1993).To study the obtainable resolution and the extractable surface information in SEM from a variety of coating techniques and metals, thin specimens (<20nm) were used as test specimens in order to reduce the signal contribution of the background (SEII).
An ultra-high resolution SEM study of the morphology of electrically switchable volume gratings formed from polymer-dispersed liquid crystals
Authors: Vezie D. L. , Bunning T. J. 
Published: June 2020

Low-voltage, ultra-high resolution SEM (UHR SEM) is becoming a valuable complementary technique to TEM, X-ray diffraction, and the scanning probe microscopies for determining polymer morphology and polymer structure-property relationships. Imaging organic materials at low voltage without significant loss in resolution allows for the visualization of structurally interesting features on the order of 50 - 1000 Å with reduced charging and improved topographic contrast. The easily interpretable nature of the data obtained from this technique and the ease of sample preparation offer advantages over more commonly used polymer morphology characterization techniques.Electrically switchable polymer dispersed liquid crystal (PDLC) volume gratings are of considerable interest for applications in diffractive optics. The system presently under investigation is a PDLC diffraction grating formed by a single-step laser induced polymerization of a penta-acrylate monomer, blended with a photoinitiator, crosslinker, and E7 liquid crystal (LC). Upon polymerization, the liquid crystal phase-separates into liquid crystal-rich planes with a periodicity of 0.56 μm.
High-resolution observation of sintered alumina (Al2O3) using the specimen-heated and electron-beam-induced conductivity method in a UHR-SEM
Authors: Ogura K. , Suzuki T. , Nielsen C. 
Published: June 2020

In spite of the complicated specimen preparation, Transmission Electron Microscopes (TEM) have traditionally been used for the investigation of the fine grain structures of sintered ceramics. Scanning Electron Microscopes (SEM) have not been used much for the same purpose as TEM because of poor results caused by the specimen charging effect, and also the lack of sufficient resolution. Here, we are presenting a successful result of high resolution imaging of sintered alumina (pure Al2O3) using the Specimen Heated and Electron Beam Induced Conductivity (SHEBIC) method, which we recently reported, in an ultrahigh resolution SEM (UHR-SEM). The JSM-6000F, equipped with a Field Emission Gun (FEG) and an in-lens specimen position, was used for this application.After sintered Al2O3 was sliced into a piece approximately 0.5 mm in thickness, one side was mechanically polished to get a shiny plane for the observation. When the observation was started at 20 kV, an enormous charging effect occured, and it was impossible to obtain a clear Secondary Electron (SE) image (Fig.1).
Effects of deposition parameters on morphology of Langmuir-blodgett films of poly(γ-Benzyl-L-Glutamate) by scanning-probe-microscopy
Authors: Smith D. L. , Musselman I. H. , Enriquez E. P. , Guarisco V. F. , Samulski E. T. 
Published: June 2020

Synthetic homopolypeptides, such as poly(γ-benzyl-L-glutamate)(PBLG) bear oc-helical secondary structure and exhibit liquid-crystalline behavior. These properties are useful for a range of materials applications, among them nonlinear optics (NLO). The α-helical structural motif of PBLG can be exploited by regular substitution of chemical functionalities in the sidechains along the main axis. Macromolecular order can then be established in polypeptide thin films using Langmuir-Blodgett (LB) deposition. Monolayer films of PBLG have been investigated by surface spectroscopic techniques, without having an understanding of the local morphology.Atomic force microscopy (AFM) has the potential for elucidating the microstructure of LB films, providing a mechanism for relating differing morphologies to deposition parameters. Excessive contact forces exerted by an AFM tip at small size scales, however, make the technique less viable for delicate organic monolayers. By intermittently striking a sample surface with a sharp probe, the tapping mode AFM provides a means for nondestructively imaging such soft samples.
Microstructure of thin YBa2Cu3O7−δ films
Authors: Grant Norton M. , Barry Carter C. 
Published: June 2020

The microstructure of superconducting thin-films often strongly influences their electrical properties. The actual microstructure of the film will be dependent on the nucleation and early stages of film growth, although the substrate will also be expected to exert an influence during the early stages of growth by the establishment of epitaxy. The highest critical currents have been obtained with films grown on SrTiO3, however MgO is of fundamental interest because patterned films on MgO have been shown to possess Josephson weak-link structure. The presence of the Josephson weak-links has been correlated with the occurrence of misaligned grains in films grown on MgO. Ultra-thin films of high-Tc superconductors are of interest for understanding the properties of these materials and may also be of use in technical applications.The microstructure of ultra-thin YBa2Cu3O7−δ films prepared by pulsed-laser ablation onto (001)- oriented MgO has been studied using transmission electron microscopy (TEM) and selected-area diffraction (SAD).
Interfaces and defect structures in epitaxial heterostructures of YBa2Cu3O7 and PrBa2Cu3O7
Authors: Jia C. L. , Kabius B. , Soltner H. , Poppe U. , Urban K. , Schubert J. , Buchal Ch. 
Published: June 2020

For the realization of electronic devices using high-Tc superconductors it is necessary to produce multilayers of superconducting and nonsuperconducting or insulating films. It was suggested by Poppe et al. to prepare epitaxial heterostructures on the basis of superconducting YBa2Cu3O7 and semiconducting PrBa2Cu3O7. Heterostructures with similar composition have also been investigated by other authors. The two materials are isomorphic and have the advantage of a small lattice mismatch.The microstructure of YBa2Cu3O7/PrBa2Cu3O7/YBa2Cu3O7 heterostructures, which have been sputtered epitaxially on SrTiO3 substrates, was examined by high-resolution transmission electron microscopy (HREM), Rutherford backscattering (RBS), and energy-dispersive X-ray analysis (EDX). Measurement of the resistivity vs. temperature of the superconducting layer gave a value of about 90 K for the onset of the superconducting transition. Zero resistance was obtained at temperatures between 80 K and 88 K depending on the specific sample.
Effects of local oxygen ordering on superconducting properties of YBa2Cu3O7−x
Authors: Thiel Bradley L. , Sarikaya Mehmet , Javadpour Jafar , Aksay Ilhan A. 
Published: June 2020

The amount of oxygen in high temperature superconducting ceramics is generally recognized as a critical factor affecting the superconducting properties. In this work, nanometer-scale variations in the oxygen ordering of powdered YBa2Cu3O7−x samples, having nominally identical oxygen contents, have been quantified using a novel deconvolution technique on electron diffraction patterns. These variations were correlated with the superconducting properties as studied by magnetic flux exclusion.Microdensitometer traces of the twin-split (110) type spots in the orientation were deconvoluted to extract the orthorhombicity distribution within the diffracting region. The deconvolution process is shown schematically in Fig. 1. The orthorhombicity is defined as:where a and b are lattice parameters of the orthorhombic unit cell on the Cu-O basal plane. In the samples studied, materials showing the highest Δa/a (about 2.05%) were also those that displayed the highest Tc values. Furthermore, the width of the superconducting onset, ΔTC, reflected the width of the Δa/a distribution.
HREM study of high Tc oxide superconductor wires made by laser heated pedestal growth technique
Authors: Qiao G. W. 
Published: June 2020

Laser Heated Pedestal Growth (LHPG) technique has many advantages, such as crucible-free, no contamination, steep temperature gradients, high density and low defects, etc. for preparing the high Tc oxide superconductor fibers with high transport critical current density due to the floating zone melting and textured structure. For incongruently melt compounds, the technique is probably the best available for growing homogeneous crystals of these materials and was successfully used for making Y and Bi system fibers in Stanford University, IMR and MIT.The HREM investigation was carried out on the grainboundaries situation which plays an important role in reducing the weak links and enhancing the current transporting ability. The as-grown crystals are 0.5-1.5mm in diameters. X-ray diffraction patterns on plane films showed the textured structures with a-b plane parallel to the growth axis both in Y and Bi system compounds. Fig.1 shows the aligned structures in asgrown crystal of BSCCO.
Microstructure and crystal symmetry of Pb2Sr2(Y/Ca)Cu3O9−δ
Authors: Lin Y. P. , Xue J. S. , Greedan J. E. 
Published: June 2020

A new family of high temperature superconductors based on Pb2Sr2YCu3O9−δ has recently been reported. One method of improving Tc has been to replace Y partially with Ca. Although the basic structure of this type of superconductors is known, the detailed structure is still unclear, and various space groups has been proposed. In our work, crystals of Pb2Sr2YCu3O9−δ with dimensions up to 1 × 1 × 0.25.mm and with Tc of 84 K have been grown and their superconducting properties described. The defects and crystal symmetry have been investigated using electron microscopy performed on crushed crystals supported on a holey carbon film.Electron diffraction confirmed x-ray diffraction results which showed that the crystals are primitive orthorhombic with a=0.5383, b=0.5423 and c=1.5765 nm. Convergent Beam Electron Diffraction (CBED) patterns for the and axes are shown in Figs. 1 and 2 respectively.
Epitaxy and texture analysis of Bi-Sr-Ca-Cu-O thin films on (100) MgO using Transmission Electron Microscopy
Authors: Sizemore J. T. , Schlom D. G. , Chen Z. J. , Eckstein J. N. , Bozovic I. , von Dessonneck K. E. , Bravman J. C. , Harris J. S. 
Published: June 2020

Investigators observe large critical currents for superconducting thin films deposited epitaxially on single crystal substrates. The orientation of these films is often characterized by specifying the unit cell axis that is perpendicular to the substrate. This omits specifying the orientation of the other unit cell axes and grain boundary angles between grains of the thin film. Misorientation between grains of YBa2Cu3O7−δ decreases the critical current, even in those films that are c axis oriented. We presume that these results are similar for bismuth based superconductors and report the epitaxial orientations and textures observed in such films.Thin films of nominally Bi2Sr2CaCu2Ox were deposited on MgO using molecular beam epitaxy (MBE). These films were in situ grown (during growth oxygen was incorporated and the films were not oxygen post-annealed) and shuttering was used to encourage c axis growth. Other papers report the details of the synthesis procedure. The films were characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM).
Modulated structures of Bi-based high-Tc superconducting oxides studied by High Resolution Electron Microscopy and electron diffraction
Authors: Nagakura Sigemaro , Hirotsu Yoshihiko , Yamamoto Naoki , Miyagawa Katsumi , Ikeda Yuji , Nakamura Yoshio 
Published: June 2020

In the superconducting Bi-Sr-Ca-Cu-O system, ideal compositions of the low Tc(Tc∼90 K) and the high Tc(Tc∼110K) phases are Bi2Sr2CaCu2Oy(y∼8:2212 phase) and Bi2Sr2Ca2 Cu3Oy (y∼10:2223 phase), respectively. The fundamental structures of these phases are tetragonal with parameters: at=bt=0.54 and ct=3.08 nm for the 2212 phase, and at=bt=0.54 and ct=3.71 nm for the 2223 phase. These phases have incommensurate structures with modulation along their b-axes. In this study, the modulated structures of Pb-doped 2212 and 2223 phases have been investigated by means of high resolution electron microscopy and electron diffraction. Samples Bi2-xPbxSr2CaCu2Oy(x=0-0.4, melt-quenched and annealed) and Bi2−xPbxSr2Ca2Cu3Oy(x=0-0.6, sintered) were observed in high resolution electron microscopes operating at 200 kV and 1 MV.Analysis of the incommensurate modulated structures of the 2212 and 2223 phases was made by using samples Bi2Sr2CaCu2Oy and Bi1.6Pb0.4Sr2Ca2Cu3Oy. The lattice parameters of the incommensurate superstructures are a=at and c=ct for both of these phases, but b∼5bt and b∼bt for the 2212 and 2223 phases, respectively.
Electron Microscopic study of modulated structure in a Bi-Pb-Sr-Ca-Cu-O system
Authors: Kumao Akihiro , Uyeda Shin’ichiro , Endoh Hisamitsu 
Published: June 2020

The preparation of high-Tc superconductor Bi-Sr-Ca-Cu-O is difficult because the strict heat treatment is requested. Takano et al. reported that the partial substitution of Pb for Bi in the system increases the volume of the high-Tc phase, namely it relieves the preparation condition of a superconductor both in the composition of starting materials and heating process. In this paper long-period structure and modulated structure in the Bi-Pb-Sr-Ca-Cu-O system is described.Powders of Bi2O3, PbO, SrCO3, CaCO3 and CuO, which were weighed such that the ratio of Bi:Pb:Sr: Ca:Cu = 0.96:0.15:1:1.1:1.6 (Sample 1), were dissolved in nitric acid. The compound produced by heating and evaporating solvent was ground in an agate mortar and heated in air at 800°C for 12h. After the reaction the mixture was ground again and made as a pellet, which was heated at 850°C for 48h. Other compositions, Bi:Pb:Sr:Ca:Cu = 0.96:0.24:1:1.1:1.6(Sample 2) and =0.7:0.3:1:1:1.8 (Sample 3), were also prepared with the same manner.
Evidence for a new quasicrystalline transition state in Al65Cu20Fe15 alloy
Authors: Zhang Z. , Li N.C. , Urban K. 
Published: June 2020

In Al65Cu20Fe15 alloy icosahedral quasicrystals are formed of extraordinary perfection. On the other hand, there are indications that the quasicrystalline phase is only stable at temperatures above about 800°C. Here we report on a transmission electron microscopy study of a new phase which represents a transition stage between the icosahedral quasicrystalline (IQ) phase and a crystalline phase. It can be described by a modulation of the IQ phase along one of the five-fold axes (A5) of the original IQ phase.The icosahedral phase in Al65Cu20Fe15 was obtained by arc melting the high purity elements and subsequent slow cooling. The material was then heat treated at 700°C for 24 hours and again slowly cooled to room temperature. During this treatment the regular IQ phase transformed into a phase characterized by the occurence of translation periodicity along one of the five-fold axes of the original IQ phase.
This is demonstrated by a commensurate arrangement of electron diffraction spots only along one of the original A5 (Fig. 1). High-resolution electron microscopy (HREM) corroborates this observation (Fig. 2).