bluuebunny/crossref_metadata_2025_split huggingface dataset:
TEM and image analysis to quantitatively describe the phase behavior in copolymer/homopolymer/homopolymer blends: Effect of the copolymer sequence distribution
Authors: Winey Karen I. , Galvin Mary E. 
Published: June 2020

Polymers are typically immiscible with one another, that is phase separated, in the absence of specific favorable intermolecular interactions, because the combinatorial entropy of mixing is small. Copolymers, polymer molecules containing more than one type of monomer unit, are frequently used to induce miscibility in homopolymer mixtures. Extensive work has previously established the importance of the copolymer composition, though the sequence of monomers within the copolymer has received less attention. Copolymers with random and with alternating sequences of monomers have been synthesized and mixed with homopolymers to evaluate the importance of the sequence distribution on blend miscibility. Blend miscibility determinations using differential scanning calorimetry and visual inspection can be erroneous when the glass transition temperatures of the phases are similar or the domains are small compared to the wavelength of light. Thus, we have used transmission electron microscopy to study the phase behavior of these polymer blends.Blend samples (∼30 mg) of poly(styrene-co-methyl methacrylate) (PS-PMMA), homopolystyrene (PS), homopoly(methyl methacrylate) (PMMA) were prepared by casting from tetrahydrofuran and annealing at 150°C for 7 days.
Structural analysis of a Σ5 grain boundary in YBa2Cu3O7δ
Authors: Wang J.-Y. , Zhu Y. , King A.H. , Suenaga M. 
Published: June 2020

One outstanding problem in YBa2Cu3O7−δ superconductors is the weak link behavior of grain boundaries, especially boundaries with a large-angle misorientation. Increasing evidence shows that lattice mismatch at the boundaries contributes to variations in oxygen and cation concentrations at the boundaries, while the strain field surrounding a dislocation core at the boundary suppresses the superconducting order parameter. Thus, understanding the structure of the grain boundary and the grain boundary dislocations (which describe the topology of the boundary) is essential in elucidating the superconducting characteristics of boundaries. Here, we discuss our study of the structure of a Σ5 grain boundary by transmission electron microscopy. The characterization of the structure of the boundary was based on the coincidence site lattice (CSL) model.Fig.l shows two-beam images of the grain boundary near the projection. An array of grain boundary dislocations, with spacings of about 30nm, is clearly visible in Fig. 1(a), but invisible in Fig. 1(b).
Grain boundaries in ceramics for solid oxide fuel cells
Authors: Tsai F. , Cowley J. M. , Jiang S. S. , Wagner J. B. 
Published: June 2020

Calcia stabilized zirconia(CSZ) and ceria(CeO2) doped with rare-earth oxides have been used as electrolytes in solid oxide fuel cells(SOFC). Such ceramics are usually good ionic conductors for oxygen ions at elevated temperatures. A few studies have attempted to correlate the microstructures with ionic conductivity. It was suggested that the grain boundaries play a role in depressing the ionic conductivity. In their study, it was found that continuous “thick” boundary layers of secondary phases existed on the grain boundaries and blocked ion transport.In the present studies, high resolution transmission electron microscopy has been used to investigate the microstructures of grain boundaries in zirconia doped with calcia (ZrO2 + 13%CaO) and ceria ceramics doped with calcia (CeO2 + 10% CaO). The ceramics was made in our Solid State Ionics Laboratory. Transport number measurements on zirconia samples showed that the transport number tO2- =1 from PO2 = 10-17 atm to PO2 =1 atm.
Recent advances and opportunities in magnetic recording materials
Authors: Kryder Mark H. 
Published: June 2020

Recording densities in magnetic recording products manufactured today are of the order of 200 Mbit/in. However, it is projected that densities as high as 10 Gbit/in will be achieved in the future. To achieve this, substantial improvements in the thin film magnetic materials used for magnetic heads and media are required.To support higher recording density in thin film media, it is necessary to increase the coercivity, while simultaneously achieving small grain size and small intergranular coupling. To achieve high coercivity, materials with large magnetocrystalline anisotropy are used, while to achieve small, well-isolated grains, special materials are used and deposited under conditions which promote either heavily voided grain boundaries or the segregation of non-magnetic species to the grain boundaries. It is also thought to be important to control the orientation of the crystallites so that a preferred axis of magnetization lies parallel to the direction of recording.
Correlation of microstructural and magnetic properties of longitudinal recording media using TEM
Authors: Nolan T. P. , Sinclair R. , Yamashita T. , Ranjan R. 
Published: June 2020

Cobalt alloy on chromium thin film media are used in industry because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic properties depend strongly on processing conditions and, as will be shown, the resulting microstructure.A complete structure-processing-properties analysis requires effective measurement of both magnetic and microstructural properties. Direct micromagnetic-microstructural comparison is not yet readily available, but bulk hysteresis loop parameters are reproducible and highly correlated with both desired recording characteristics and microstructures, and so provide a valuable, albeit indirect comparison. Signal to noise (S/N) measurements are also used as a more direct measure of usefulness in a high density disk drive. The nanoscale microstructural features which dramatically affect these bulk magnetic properties are difficult to observe. However, careful combination of TEM techniques, including bright-field, dark-field, high-resolution, selected area diffraction and elongated-probe microdiffraction can determine the subtle microstructural differences.
Co-Thickness dependence of the microstructure of Pt/Co multilayers
Authors: Li Z.G. , Carcia P.F. 
Published: June 2020

For Co layer thicknesses less than about 12 Å, Pt/Co multilayers have perpendicular magnetic anisotropy . However, the best magnetic properties are obtained when Co is only ∼4 Å thick, or nearly two atomic layers, and the Pt layer at least twice as thick. We have revealed the microstructure dependence of the Pt/Co multilayers on the Co thicknesses by using high resolution electron microscopy.We found that for thin Co (∼ 4 Å), Pt/Co multilayers had (111)-fcc texture and a coherent lattice with interplanar spacing of ∼ 2.2 Å. The lattice coherence depended only on the Co thickness and was independent of the film preparation method. However, multilayers synthesized by vapor-deposition or Xe-sputtering, which impart less energy to the growing film, consisted of a larger single crystal volume of Pt/Co superlattice, and also had better (111) texture than Ar- or Ne-sputtered multilayers. Fig. 1) and Fig. 2) illustrate these points with atomic resolution images of Ne-sputtered and vapor-deposited multilayers.
Signal transfer efficiency of slow-scan CCD cameras
Authors: de Ruijter W.J. , Mooney P.E. , Krivanek O.L. 
Published: June 2020

Slow-scan CCD cameras are helping transmission electron microscopy and electron holography become increasingly quantitative. Accurate characterization of the performance of the cameras can extend this trend by making it possible to extract weak signals from noisy images with optimal precision. The property to be characterized is die performance of the camera in transferring a particular spatial frequency contained in the input electron image to the output image captured by a computer, as a function of the input intensity. Using the concepts and notation of standard signal processing theory, we characterize this performance by introducing signal transfer efficiency (STE) defined as:where SNRin(K) and SNRout(K) are signal-to-noise ratios at the input and the output of the image detector as a function of spatial frequency k. Signal-to-noise ratio is defined as SNR(K)=SII(K)/Snn(K) where SII(k) and Snn(k) denote the power spectra of the signal and the noise. STE could be regarded as an extension of the use of detection quantum efficiency as a figure of merit for electron image detectors.
Electron holography of vortex lattices in superconductors
Authors: Bonevich J.E. , Harada K. , Matsuda T. , Kasai H. , Yoshida T. , Pozzi G. , Tonomura A. 
Published: June 2020

The recent success in observing magnetic vortices in superconductors by means of transmission electron microscopy techniques has opened a new window to investigate the behavior of vortex lattices. We report the first direct observation of 2-D vortex lattices in niobium thin films taking advantage of the high resolution and sensitivity of electron holography.The experiments were conducted in a 300 keV field emission electron microscope equipped with a cold stage that allows magnetic fields to be applied while the specimen can be maintained from 30 K down to 4.5 K. The Nb specimen is tilted by 45° to the electron beam and the magnetic field is applied in the horizontal direction. The microscope also has a rotatable electron biprism used to form holograms. The thin (70±20 nm) foil specimens were prepared by chemically polishing 2 mm × 2 mm × 30 μm sections of Nb that had been annealed to ∼2000°C in a vacuum of 10-6 Pa.
TiO2 on MgO by PLD: The effect of the substrate treatment
Authors: King Simon , Barry Carter C. 
Published: June 2020

The recent demonstration of the epitactic growth of YBa2Cu3O7-x (YBCO) onto (100) MgO passivated by a layer of the inverse spinel Mg2TiO4, combined with the large number of possible reaction products of” widely differing structure (normal spinel (Ti3+), inverse spinel, pseudo-brookite, perovskite) make the MgO-TiO2 system one of the more interesting, and complex, currently under examination.Over the last few years, Hesse, Bethge and co-workers (see 1 for refs), have applied various microscopal techniques to the study of e-beam evaporated TiO2 onto MgO. The present paper extends this investigation to pulsed-laser deposited (PLD) TiO2 onto MgO. Unlike almost all previous studies of PLD films, pre-characterized “TEM-ready” substrates are used, a technique pioneered by Norton et al, thereby circumventing the possibility of affecting the film morphology during the thinning process. This technique also allows the imaging in the TEM of identical areas both before and after deposition.
TEM study on the thermostability of hafnium carbide dispersoids in tungsten at ultrahigh temperatures
Authors: Liu Mingqi , Cowley John M. 
Published: June 2020

Tungsten dispersed by hafnium carbide (HfC) particles has been found to be the strongest metallic material at temperatures above 2000 K. The strength of W-HfC alloy is directly related to the thermostability of HfC particles at ultrahigh temperatures. In the present study, the growth behavior and growth mechanism of HfC particles from 2200 to 3000 K are examined with transmission electron microscopy (TEM) and a correlation between the particle size and alloy strength is established.The examined material was a tungsten-3.6 wt%rhenium-0.35 wt%HfC alloy. The solid solution element rhenium was to improve the fabricability of tungsten at room temperature. Specimens were heated to a temperature between 2200 and 3000 K for two hours and then deformed in tension. After a 5% elongation, the specimens were rapidly cooled down to room temperature at a cooling rate greater than 200 K/s in order to maintain the high temperature substructures which were examined with a JEM-2000FX high resolution TEM.
EELS and stopping-power calculation of the superconductor Bi1.8Pb0.3Sr2Ca2Cu3O10
Authors: Dunlap J. R. , Luo S. , Joy D. C. , Chakoumakos D. C. , Zhu S. , Sun Y. 
Published: June 2020

Several studies have been undertaken to investigate the fine structure and superconductive properties of high temperature superconductors. Yuan et al. utilized electron energy loss spectroscopy (EELS) to determine the dielectric function of the superconductor Ba2YCu3O7-x. In this study we performed EELS on the superconductor Bi1.8Pb0.3Sr2Ca2Cu3O10at both room temperature and below the transition temperature and calculated such properties as the dielectric fuction, the inelastic mean free path and the stopping power for this material.Powdered Bi1.8Pb0.3Sr2Ca2Cu3O10was dispersed by sonication in a 0.2% (wt/v) solution of poly-(N-vinylpyrrolidone) in isoproponal. Individual crystals were allowed to settle and dry on a lacey cabon film. Figure 1 shows a typical individual crystal and Fig.2 shows a typical diffraction pattern. Electron energy loss spectra were recorded from single crystals which extended into holes in the film. The EEL spectra were recorded at room temperature and at 95°K which is below the transition temperature of 105 °K.
High resolution Scanning Electron Microscopy
Authors: Joy David C. 
Published: June 2020

High resolution scanning electron microscopy is still a relatively new and unfamiliar concept because in the early days of the SEM it was expected, that secondary electron imaging would be limited to a resolution of between 5 and 10nm at best. Now, however, because of improvements in instrumentation and technique based on advances in the understanding of electron beam interactions with solids current SEMs can demonstrate spatial resolutions below 1nm, rivaling those obtained by transmission instruments.High performance scanning electron microscopes always incorporate two advanced items of instrumentation. Firstly they use field emission guns (FEGs). The high brightness, low energy spread, and small source size of the FEG makes it possible to produce an electron probe of sub-nanometer size which contains sufficient current for secondary electron imaging (i.e 10-12 amps or more) and which can maintain this performance over a wide energy range (3 to 30keV). Secondly, the new high performance instruments place the specimen within a high excitation, immersion, probe forming lens.
Practical applications of scanning tunneling microscopy
Authors: Denley D. R. 
Published: June 2020

Scanning tunneling microscopy (STM) has recently been introduced as a promising tool for analyzing surface atomic structure. We have used STM for its extremely high resolution (especially the direction normal to surfaces) and its ability for imaging in ambient atmosphere. We have examined surfaces of metals, semiconductors, and molecules deposited on these materials to achieve atomic resolution in favorable cases.When the high resolution capability is coupled with digital data acquisition, it is simple to get quantitative information on surface texture. This is illustrated for the measurement of surface roughness of evaporated gold films as a function of deposition temperature and annealing time in Figure 1. These results show a clear trend for which the roughness, as well as the experimental deviance of the roughness is found to be minimal for evaporation at 300°C. It is also possible to contrast different measures of roughness.
Scanning tunneling microscopy (STM) of DNA and RNA
Authors: Arscott Patricia G. , Lee Gil , Bloomfield Victor A. , Evans D. Fennell 
Published: June 2020

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).
Computer controlled TEM
Authors: Kersker M. , Lehman J. , Rowlands N. 
Published: June 2020

The use of the microprocessor and/or computer for the control of lenses, deflectors, stigmators, camera, gun, accelerating voltage, vacuum system, etc. in the transmission microscope has resulted in improved and simplified operation of the microscope without a consequent sacrifice in the operating flexibility of the TEM. Based on years of experience with electron microscopists, the basic ergonometric design of the microprocessor/computer controlled instrument remains unchanged since the microscopist still has to stradle the microscope in order to operate the stage and apertures. Potentiometers are replaced by rotary encoders, programming of the encoders and of the entire instrument is accomplished by factory upgradable PROMs, and function switches have been added that are uniquely programmable and hence upgradable. Operating simplicity and improved performance were a consequence of the major design consideration, “keep the microscope properly aligned.”Under properly aligned conditions an operator can then easily operate in STEM mode, normal TEM imaging mode, diffraction mode, low mag mode.
In environmental Scanning Electron Microscopy, the secondary electron signal reveals surface information not accessible by conventional backscattered electron signals
Authors: Peters Klaus-Ruediger 
Published: June 2020

Environmental scanning electron microscopes (ESEM) operate at high as well as at low vacuum (<2.5 kPa: ~20 Torr) but utilize all advantages of conventional high vacuum SEM (large specimen size, high depth of focus and specimen tilt capability, TV-rate scanning for imaging dynamic events). They have the advantage of imaging wet specimens as well as insulators without the need of any specimen preparation. Previously, environmental scanning microscopy was restricted to the BSE signal collected with BSE detectors. SE signals cannot be collected with the Everhart-Thornley detector because it cannot operate at low vacuum. Using positively biased electron collectors, it is now possible to collect an SE signal. However, the origin and quality of this signal need to be further characterized.An ElectroScan ESEM was used equipped with SE and BSE detectors and operated at 7-30 kV with partial water pressures of 0.1-2.5 kPa (∼1-20 Torr).
Secondary electron imaging of MoO3 reduction in a UHV STEM
Authors: Crozier P. A. , Liu J. , Cowley J. M. 
Published: June 2020

Recently, a number of people have studied the ability of focussed electron beams to form lines and holes in metal oxides. Many metal oxides decompose when irradiated under the high intensity focussed probes used in field emission STEMS. Initially, many of these oxides reduce to the metal and in some cases it is possible to drill holes in the material. Understanding the nature of the interaction between the electron beam and the sample is important for materials characterisation. These studies may also lead to the development of new electron beam resists and masks. Here we present some preliminary results on the effect of electron irradiation on MoO3 in a field emission UHV STEM. We show, for the first time, secondary electron (SE)images of the entrance and exit surface of the sample after radiation damage has occurred.The experiments described here were performed on the VG HB501S; a dedicated STEM in which vacuums better than 10-10 torr are routinely available in the column.
Design of a TEM/STEM Auger Detector
Authors: Ai R. 
Published: June 2020

In order to perform surface studies in an electron microscope, one has to be able to detect atoms adsorbed on the surface. The standard approach in surface science is to attach an Auger spectrometer using a CMA or CHA, but such an instrument is intrinsically incompatible with the performance of a TEM/STEM. In this note we describe a design which uses a far smaller analyzer which should be compatible with almost all microscopes.One important aspect of the design is to recognize that due to the strong magnetic lenses, low energy electrons are refocussed along the optic axis of the microscope, based on our trajectory calculations. As an example, Figure 1 shows the calculated trajectories for 500 eV electrons through the upper pole piece of the UHV-H9000 microscope. Figure 2 shows a graph of the final focus position as a function of energy, from which it is apparent that for most energies a final focus occurs between 5mm to 9mm from the specimen;
High-voltage Electron Microscopy and 3-D reconstruction of human hair fiber ultrastructure
Authors: Rudy L. , Sneath R. , Song M. 
Published: June 2020

The basic morphology of the non-keratinous regions of human hair fibers was studied using both conventional and high voltage electron microscopy. The non-keratinous regions of hair include the endocuticle, the cell membrane complex, and the nuclear remnants of the cortex. By characterizing these regions more clearly, the mechanisms by which external influences affect the hair can be understood. The nuclear remnants are surrounded by a cell membrane complex. Since thin sectioning often causes artifacts in these fragile structures, a three-dimensional reconstruction using serial, semi-thick sections was completed to reveal their morphological nature.Human hair fibers collected from a female subject, had not been treated with any chemically active processes. One centimeter samples were collected near the scalp region of the back of the head. The fibers were embedded in Epon-812. Serial, semi-thick sections, 0.25u thick, were sectioned and collected on copper slot, formvar-coated grids. Post-staining was completed with uranyl acetate and lead citrate. Sections were examined in an AEl EM7 Mk 1.2MV HVEM at an accelerating voltage of 1.0 MV.
Real-time confocal imaging ofStentor coeruleusin epi-reflective mode by using a Tracor Northern tandem scanning microscope
Authors: Chen V. K-H. , Cheng P. C. 
Published: June 2020

Confocal microscopes with a spinning disk design are potentially useful in the study of dynamic processes in biological systems. However, the image brightness of the spinning disk type confocal microscope is generally quite low.A Tracor Northern Tandem Scanning confocal microscope (TSM) modified to accept a TV camera-coupled second generation image intensifier was used in this study. An Olympus 38mm Macro lens (f/2.8) was used in place of the original eyepiece to relay the image of the spinning disk onto the photocathod of the image intensifier. In order to fit the macro lens and the image intensifier onto the microscope, a set of adaptors were designed and fabricated. Figure 1 shows the microscope set-ups. To increase the image intensity, a 200W Mercury short arc lamp was used as the light source. An UV filter was used to remove radiations harmful for living specimen.