bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural characterization of granular Au-Co GMR material by Lorentz microscopy
Authors: Bernardi J. , Hütten A. , Nelson C. , Thomas G.
Published: June 2020

Giant magnetoresistance (GMR) has recently been achieved in multilayers as well as in granular alloys prepared by sputtering or melt spinning. In these granular alloys magnetic Co particles are usually embedded in a nonferromagnetic metallic matrix (Cu, Ag, Au) and have a statistical magnetic moment distribution. The GMR effect originates mainly from spin dependent scattering of conduction electrons within the ferromagnetic Co particles and at their interfaces and is controlled by the size distribution and the volume fraction of the Co particles as well as the roughness of the interfaces between the Co particles and the matrix. Au-Co was chosen as a model system to investigate systematically the microstructural influence on the transport properties. The large difference of the atomic scattering factors of Au and Co enables the distribution of ferromagnetic Co particles be distinguished by structure factor contrast. The eutectic decomposition in Au-Co (Liq. ⇔ Au + Co at TE = 995.6 °C and 28.4 at% Co) allows a multilayered structure in rapidly quenched Au-Co to be synthesized.
Self-assembly of surfactant-silicate nanophases
Authors: Walker S. A. , Zasadzinski J. A.
Published: June 2020

Nanostructured zeolites are ubiquitous throughout chemistry as catalysts and sorption media' A new variety of zeolites, constructed by templating inorganic silica on surfactant liquid crystalline phases, consist of ordered arrays of cylindrical pores with diameters ranging from 20 Å to greater than 500 Å. The nanostructure of these materials can be tailored to a variety of applications, each of which makes use of the zeolite network's large surface area and prescribed microstructure. Recent studies indicate that the initial step in the nanophase formation is a cooperative self-assembly of inorganic silicate species and organic surfactant species, dictated by ionic interaction between silicate anions and cationic surfactants. Freeze-fracture transmission electron microscopy (FF-TEM) is the only technique that can visualize this self-assembly process in situ to determine phase boundaries and examine the formation mechanism.

The nanophases form on mixing aqueous cetyl trimethylammonium bromide (CTAB) with silicate (SiO2; prepared from CAB-O-SIL M-5, tetramethylammonium hydroxide (TMA-OH), trimethyl benzene (TMB), methanol (CH3OH), and water).
Morphology of polymer-polymer dewetting in thin films
Authors: Winey K. I. , Faldi A. , Composto R. J.
Published: June 2020

Two or more thin polymer layers are frequently combined for industrial applications such as protective coatings, lubricants, packaging, and adhesives. One might refer to such multi-layered polymeric structures as planar nanocomposites. The use of multiple polymer thin films requires the control of spreading and dewetting of these films. Our studies have identified a number of important characteristics of the kinetics and morphology of polymer melt / polymer melt dewetting. Particularly noteworthy is our ability to distinguish the two polymer melts in a cross-sectional view.
At 190°C a 200 nm film of polycarbonate (PC) was found to dewet a 200 nm film of poly(styrene-co-acrylonitrile) (SAN) which had been deposited onto a rigid substrate. An optical micrograph of an intermediate stage of polymer-polymer dewetting shows the characteristic features: a circular hole in the upper layer (light gray), a rim surrounding the hole, and a small dimple in the center of the hole (dark gray), Figure 1.
In situ reversed deformation of aluminum single crystals in the HVEM: a new X-Y straining stage
Authors: Wall M. A. , Kassner M. E.
Published: June 2020

The metal fatigue phenomenon is poorly understood, partially because the dislocation dynamics of reversed deformation have not been well characterized. Little success has been realized with the direct observation of dislocations during in situ cyclic deformation. Problems associated with buckling of the specimen foil occur during applied shear, bending or compression. Buckling can preclude adequate imaging conditions and further complicate the thin foil stress-state. Recent experiments have shown that dislocation movement can be reversed by tensile stressing in alternate perpendicular directions (i.e. 90° rotation of the tensile stress to X and Y directions results in the reversal of the shear stress). Buckling of the specimen foil is also reduced in these experiments.

Results from recent in situ reversed deformation experiments are presented here. The experiments were performed on a new straining stage which is a modification of the Sleeswyk- Kassner X-Y stage. The specimen design and preparation procedures have also been modified to facilitate better and more reproducible in situ experiments. The new X-Y straining stage is illustrated in figure 1.
Crystallization of barium titanate thin films synthesized via sol-gel processing
Authors: Gust M. C. , Evans N. D. , Mecartney M. L.
Published: June 2020

Sol-gel processing of oxide thin films offers the potential to generate different microstructures by varying process parameters such as water of hydrolysis, chemical precursor, or substrate. For this work, barium titanate (BaTiO3) thin films were prepared by the sol-gel method in order to try and generate different microstructures for dielectric measurements. However, for BaTiOs prepared using alkoxide precursors, the final microstructures of the films were found to be almost process independent. Films using different precursors, different substrates, and different amounts of water of hydrolysis all showed similar TEM microstructures. All the films after final heat treatment were polycrystalline, nanoporous, and randomly oriented BaTiO3; they were also fine-grained, with an average uniform grain size of 25-50 nm (Fig. 1). This fine-grained microstructure has also been observed in other studies of sol-gel derived BaTiO3 thin films. In addition to BaTiO3, electron diffraction patterns showed the presence of trace amounts of rutile TiO2 that were not observed by x-ray diffraction (XRD).
Grain growth study of Al(Cu) lines by focused ion beam microscopy and Transmission Electron Microscopy
Authors: Sohn M.H. , Smith D.A. , Rodbell K.P. , Izai Roy
Published: June 2020

Interconnects for integrated circuits now have widths which are of the same order as the grain size. Consequently, their reliability is sensitive to the specific grain boundary properties and configurations rather than being averaged over many grains as in earlier technology when the line width was much greater than the grain diameter. From the point of view of electromigration resistance a bamboo grain structure is desirable. However, the conditions for forming a bamboo structure are not established. Walton et al. developed a model which predicts that the grain structure of aluminum lines becomes a bamboo structure, which is stagnant, upon annealing after particular time at specific temperature when the width to height ratio of the line is lower than a critical ratio (2.1-3.0). The precise value of the critical ratio depends on the ratio of the surface and grain boundary energies. Based on the modeling, we expect that the grain structure of pure aluminum stagnates after annealing at 500 °C for 2.3 hrs.
Symmetry of molecular wavefunction in BaBiO3 determined by q-resolved EELS
Authors: Wang Y.Y. , Dravid V.P. , Zhang F.C.
Published: June 2020

Momentum-transfer (q) resolved electron energy loss spectroscopy is a unique technique to investigate the symmetry of electronic excitations in materials. Under small momentum-transfer conditions, the dielectric function derived from electron energy loss spectrum (EELS) is comparable to the dielectric function obtained by optical measurement. However, relatively large momentum-transfer conditions, which optical spectroscopy cannot achieve, can be met with high energy electrons and such q-resolved EELS data can provide dynamic information of the excitations as well as possible location of optically forbidden transitions.

According to the Born approximation, the differential cross section of inelastic scattering can be written as:

(1)

where Ψo and Ψf are the initial- and final-state wave functions with energies as Eo and Ef, respectively, q is the momentum transfer. If rc is the effective radius of the excitation, then for q<1/rc, one can write:

(2)

For small q, the second term dominates the integral, permitting dipole-allowed transitions. For large q, the third term, which contains monopole and quadrupole transitions, increases in strength relative to the dipole transitions.
Observation of grain boundary segregation in advanced ceramics using high-resolution imaging SIMS
Authors: Levi-Setti R. , Soni K. K. , Chabala J. M. , Thompson A. M.
Published: June 2020

The significance of grain boundaries in controlling processing and properties of ceramics is widely acknowledged. Through the addition of suitable dopants to ceramics, their processability and properties can be improved. These dopants may segregate to grain boundaries, but the characterization of boundary chemistry is a challenging task. Studies of segregation phenomena require the application of high-lateralresolution techniques such as STEM/AEM or surface sensitive techniques such as AES, XPS. These techniques require rigorous sample preparation and have their limitations.

The scanning ion microprobe is a powerful tool that has exhibited unprecedented potential in the characterization of grain boundaries in ceramics. When interfaced to a mass spectrometer (magnetic sector in our case), this instrument allows mapping of many trace elements at nanometer level in bulk specimens. The combination of excellent sensitivity and high spatial resolution enables direct imaging of grain boundary segregants. The results thus obtained are free from artifacts that typically complicate analysis with broad beam, non-imaging techniques.
Ceramic thin-film reactions: phase boundaries and kinetics
Authors: Kotula Paul G. , Barry Carter C.
Published: June 2020

Interfacial reactions between epitactic nickel oxide thin films and single-crystal aluminum oxide substrates were investigated as a function of substrate orientation. Two thin-film reaction geometries were employed for this purpose. The first, which was used to study the nucleation of the reaction product, consisted of epitactic nickel oxide thin films on alumina substrates. The second, which was used to determine the reaction kinetics, was similar to the first except that a thin epitactic buffer layer of the reaction product was placed between the nickel oxide film and substrate. In this case, the nucleation was avoided by essentially ‘nucleating’ the reaction product artificially. As thin films were utilized, and the scale of the salient microstructural features were correspondingly small, electron microscopy techniques were applied to determine the preferred nucleation sites and measure the rate at which the reaction proceeds for the respective geometries.

Both types of thin-film reaction-couple geometry were produced by pulsed-laser deposition (PLD). PLD is a versatile thin-film deposition technique capable of producing high-quality oxide epilayers. The setup for PLD has been described elsewhere.
Step structure and 5×5 restructure of annealled LaAlO3 {100} - a substrate for electroceramic thin film growth
Authors: Wang Z. L. , Shapiro A.J.
Published: June 2020

Nucleation and growth of thin films are strongly affected by the microstructures of the substrate surfaces. Although LaA1O3 {100} surfaces have been widely used as substrates for growing high Tc superconductor and ferroelectric thin films, the surface structure of the material has not been extensively analyzed using electron microscopy techniques. In this paper, reflection electron microscopy (REM) [1] is applied to examine the structures of LaA1O3 {100}. REM experiments were carried out at 300 kV and 120 kV in transmission electron microscopes. The {100} surfaces were mechanically polished and subsequently annealed at 1500 °C for 20 h in air. The LaA1O3 unit cell is the distorted-perovskite structure with lattice constant a = b = c = 0.3788 nm and α = β = γ = 90.066°, in which the La+3 ion locates at (000), the A1+3 ion at (0.5 0.5 0.5), and the O−2 ions at the face-centers {0.5 0.5 0}.
Experimental realization of diamond-like carbonitride
Authors: Sarikaya Mehmet , Qian M. , Gil J. M. , Gil F. M. , Yacamán M. J.
Published: June 2020

Recently Cohen has predicted, based on an empirical model, that tetrahedral solids of low ionicity with high bulk moduli approaching that of diamond may be candidates as new hard materials. Several groups have attempted to synthesize these covalent C-N solids using vacuum deposition techniques. Although many of the literature results give C-N compounds with amorphous structures, two groups have reported the presence of a few percent of a crystalline phase, the so-called β-C3N4, after β-Si3N4 (hex.) structure, in an otherwise amorphous matrix. It has generally been difficult to synthesize samples with higher crystalline phase content and to confirm these early results. In samples prepared by a chemical precursor route, we report the presence of a crystalline carbonitride phase with zinc blende structure from electron diffraction and spectroscopy investigation. Based on a scaling relationship from Cohen, we estimate the bulk modulus of the new crystalline compound (denoted as α-C4N4 heretofore) to be comparable to c-BN and diamond from the C - N bond length determined from extended energy loss fine structure analysis, EXELFS, that allows a precise measurement of the first and second nearest neighbor distances between C and N atoms.
Structure and symmetry of CaFeTi2O6 perovskite
Authors: Yao Nan , Navrotsky Alexandra , Leinenweber Kurt
Published: June 2020

A new calcium iron (II) titanate ordered perovskite (CaFeTi2O6) was recently synthesized from an equimolar mixture of CaTiO3 and FeTiO3 at 12-15 GPa and 1200-1400 °C. In the present paper, we discuss the structure and symmetry studies of this new compound CaFeTi2O6 using CBED and HREM techniques. The CaFeTi2O6 powder sample was crushed to small fragments with an agate mortar and pestle under purified methanol. A drop of the resulting suspension was placed on a copper grid coated with holey-carbon film. CBED and HREM studies were performed on a Philips-CM20 ST transmission electron microscope equipped with a double tilt, liquid-nitrogen-cooled specimen holder under moderate vacuum conditions over the range from 10-6-10-7 Torr. CBED makes it possible to examine the diffraction symmetry of key orientations of the crystal and therefore determine the point-group symmetry of the crystal. This information, along with the dynamic extinction information on systematic absences, can be used to determine the crystallographic space group uniquely.
A TEM study of the incommensurate modulated structure in Sr2CuO3+δ
Authors: Wang Y.Y. , Zhang H. , Dravid V.P. , Marks L.D. , Han P.D. , Payne D.A.
Published: June 2020

Hiroi et al. have recently reported the occurrence of superconductivity at a transition temperature of ~ 70 K in Sr2CuO3+δ. They observed a superstructure with lattice constants of Neutron diffraction studies on this compound by Shimakawa et al. indicate that the apical oxygen is fully occupied, whereas the oxygen in CuO2 plane is half occupied. If oxygen does not fully occupy in the conducting CuO2 planes, it raises doubts about our current understanding of superconductivity in the cuprates, which relies on full oxygen occupancy for the CuO2 planes.

Recently, Han et al. observed a dependence of Tc on post annealing treatment of the high pressure synthesized Sr2CuO3+δ. They noticed that heating the sample to 300°C increased the Tc from 70 K to 94 K and that further heating to 450°C caused the sample to lose superconductivity.

In order to investigate the structural and microchemical details of Sr2CuO3+δ, transmission electron diffraction, high resolution electron microscopy, and electron energy loss spectroscopy are employed.
Scanning probe microscopy study of the growth of YBa2Cu3O7 thin films
Authors: Grant Norton M. , Biggers Rand R. , Moser E.K. , Peterson T.L. , Maartense I.
Published: June 2020

Previous work in our laboratory has demonstrated the use of scanning probe microscopy (SPM) techniques in the study of microstructure development in YBa2Cu3O7 (YBCO) thin films formed by pulsed-laser deposition (PLD) [e.g., Ref. 1]. Under certain deposition conditions a high density of surface outgrowths was observed. These outgrowths have been identified as a-axis-oriented YBCO grains nucleated at the substrate surface which grow in concert with the c-axis-oriented YBCO grains. This growth mechanism differs from that previously suggested for the formation of mixed a-axis-oriented/c-axis-oriented YBCO films. The microstructure of YBCO thin films deposited on vicinal substrates by PLD is very different from that observed for films grown on oriented substrates (even under equivalent deposition conditions). Films grown on vicinal LaA1O3 substrates consisted of elongated granular features oriented along common directions. The shape of these features is the result of step-flow growth where the ledges on the miscut substrates provide aligned and enhanced nucleation sites. Such features have been observed on films grown using several different deposition conditions: only the width of the features changed.
Evidence for a raised rim on pits in mica induced by keV/nucleon ions
Authors: Fei L. , Fraundorf P.
Published: June 2020

Nuclear tracks have been extensively studied and widely used in applications like archeological and geological dating, solar flare iostope determination, extraterrestrial material studies, super heavy elementary particle searches, etc. for more than three decades. Recently, scanning force microscopy (SFM) has proven to be useful for studying the pits induced by ions in the track recording energy range from several keV to several MeV per nucleaon on track recording material (e.g. mica) surfaces. SFM can provide topographical information on chemically etched orunetchedtrack pits at near atomic resolution in all three dimensions.

We report here using a commercial SFM (NanoScope III, Digital Instruments, CA) in the study of a muscovite mica surfaces irradiated with 150keV Ar+ions. The mica was freshly cleaved before the irradiation. The SFM was operated with the amplitude resonance (tapping) mode to lower the interaction between a tip and specimen. We found pits on the mica surface after, but not before the irradiation, like those shown in Fig. la. Their number density was orders of magnitude less than the expected argon flux.
In or on? Location of noble metal particles on zeolite/binder support
Authors: Spinnler G. E. , Liu J.
Published: June 2020

The location of metal particles contained in a zeolite-alumina binder support matrix has been difficult to solve using analytical techniques including electron microscopy. Imaging of metal particles, particularly noble metal particles on relatively light matrices such as zeolites or aluminas, has been easily accomplished using high angle annular darkfield imaging (HAADF). Since transmission imaging provides a projection through the sample, location of the particles in the sample or on the surface is not obvious. Surfacesensitive signals such as secondary electrons (SE) and Auger electrons (AE) are necessary to detect particles on the sample surface. HAADF, SE, and AE imaging have been applied to locate noble metal particles in a zeolite support with an alpha alumina binder.

The samples were analyzed in a UHV HB501S STEM (MIDAS, Microscope for Imaging and Diffraction Analysis of Surfaces) at the Center for High Resolution Electron Microscopy at Arizona State University. The samples were prepared by crushing and dry deposition on a holey carbon grid.
Characterization of carbides in iron Fischer-Tropsch catalysts
Authors: Shroff Mehul D. , Kalakkad Dinesh S. , Jackson Nancy B. , Harrington Mark S. , Sault Allen G. , Datye Abhaya K.
Published: June 2020

The Fischer - Tropsch synthesis (FTS) for the production of synthetic hydrocarbons from the indirect liquefaction of coal has tremendous potential as an alternative to petroleum - based fuels. The use of iron catalysts is desirable due to their low cost, easy availability, good FTS activity and high water - gas shift activity thus enabling use with low H2 / CO ratios. However, problems relating to attrition and deactivation need to be addressed. In addition, there has been a controversy in the literature regarding the role of the carbide phase and the identity of the active catalytic phase. The main reason for the existence of this debate has been the use of different characterization techniques. Our results with a commercial, precipitated and spray-dried, Fe2O3 - CuO - K2O Fischer-Tropsch catalyst point to the fact that conventional techniques like X - ray Diffraction (XRD), X - ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) which have been traditionally used to characterize these catalysts (1,2) are not very successful in detecting the existence of the carbide phase, which generally forms as 20 - 30 nm crystallites on the surface of the micron - sized magnetite crystals.
Defect formation in oxygen-multiply implanted silicon-on-insulator material
Authors: Park J.C. , Lee J.D. , Krause S.J.
Published: June 2020

High dose oxygen implantation (SIMOX) has been a successful fabrication technology of silicon-on-insulator (SOI) material for CMOS circuits with reduced power consumption and higher operating speed. However, high density (~108 cm-2) of the through-thickness defects (TTD) in the top Si layer of SIMOX is one of the most serious problems. Hill et al. reported multiple implant/anneal method to remarkably reduce defect densities to <104 cm-2. In the multiple implant/anneal material, however, ~106 cm2 of the final dominant defects, including stacking fault pyramids (SFP) and the precipitate-dislocation complexes (PDC), still remained after high temperature annealing. In this work, the microstructures and formation mechanism of the final defects were studied by various TEM techniques.

Silicon (100) wafers were sequentially triple implanted to doses of 6/6/6×l017 at 200kev and 620°C. After each implantation the wafers were held at 1000°C for 2 hours and annealed at 1325°C for 4 hours in argon ambient plus 5% oxygen. Cross-section (XTEM) and plan-view (PTEM) transmission electron microscopy specimens were examined by using a weak beam dark field (WBDF) and high resolution electron microscopy (HREM) techniques in JEM 2000FX and Topcon 002B operating at 200kev.
TEM and AFM studies of structural defects in α-GaN films
Authors: Qian W. , Skowronski M. , De Graef M. , Rohrer G. , Doverspike K. , Rowland L. B. , Gaskill D. K.
Published: June 2020

Interest in wide band-gap GaN and related group-III nitrides has grown recently due to their potential applications for short wavelength optoelectronic devices. One of the main obstacles for their application is the high density of defects formed during heteroepitaxy. Though important progress has been made by using a low temperature A1N buffer layer% recently reported films still contain a defect density (mainly threading dislocations) on the order of 1010 cm-2. This paper reports our current studies of structural defects in α-GaN thin films grown on a-plane (110) and c-plane (0001) sapphire substrates by organometallic vapor phase epitaxy (OMVPE). Atomic force microscopy (AFM), conventional and high resolution transmission electron microscopy (TEM) were used to investigate the nature and origin of these defects.

Single crystal α-GaN films were grown using a low temperature A1N or GaN buffer layer in an inductively-heated, water cooled, vertical OMVPE reactor operated at 57 torr.
High energy As ion implantation to GaAs
Authors: Jasinski J. , Liliental-Weber Z. , Kaminska M. , Washburn J. , Jagadish C.
Published: June 2020

Over the last few years there have been many studies of GaAs layers grown in the temperature range from 180°C to 300°C called LT-GaAs. These studies were motivated by the potential applications of that material in microwave and fast optoelectronic devices. Annealed LT-GaAs layers have interesting electrical properties including high resistivity and short photocarrier lifetime connected with the nonstoichiometry of that material. However, it is still not clear whether arsenic antisite point defects or arsenic precipitates formed during annealing cause these interesting properties of LT GaAs.

A second method of creating highly nonstoichiometric GaAs beside low temperature MBE growth is implantation with a high dose of arsenic. This method first applied two years ago showed that 200 keV arsenic ion implantation also leads to semi-insulating properties and that successive post-implantation annealing results in arsenic precipitate formation, similar to that observed in LT GaAs. Recently, more elaborate studies concerning photocarrier lifetime, resistivity, mobility and some structural characteristics were performed on GaAs implanted with high energy arsenic ions.
Microstructure and microanalysis of neodymium iron boron magnets sintered with aluminum
Authors: Chandramouli M. , Thomas G.
Published: June 2020

The magnetic properties of NdFeB magnets sintered with 15 vol.% Al at 850 °C and 1000 °C for 1 hour are dependent on microstructure. Complementary use of SEM and TEM techniques are crucial to elucidate the microstructural differences responsible for the properties. The hysterisis loops shown in Fig. 1 indicate that the higher sintering temperature sample has a larger dip near zero applied field and lower coercivity. This behavior is consistent with a larger volume fraction of soft magnetic phases.

Microstructural analysis performed using a JEOL 35 CF SEM does not show significant differences between the samples. As revealed in Fig. 2, a representative backscattered image of the 850 °C sample, the microstructure consists of dark pockets with a gray matrix region with small, bright contrast pockets. Quantitative microanalysis confirmed that the gray matrix phase had a composition consistent with Nd2Fe14B, the ferromagnetic phase in conventionally prepared Nd-Fe-B permanent magnets. The small bright pockets were found to have a high Nd content while the large dark pockets were rich in Al.
Determination of the degree of radial order in Kevlar fibers using x-ray linear dichroism microscopy
Authors: Smith A. P. , Ade H. , Hsiao B. , Subramoney S.
Published: June 2020

The Scanning Transmission X-ray Microscope (STXM) located at beamline X1A at the National Synchrotron Light Source at Brookhaven National Laboratory can be used to acquires high resolution, chemically and orientationally sensitive images with 50 nm spatial resolution, as well as point spectra from 0.1 μm2 areas. Chemical (valence) sensitivity can be achieved via the X-ray Absorption Near Edge Structure (XANES) at the carbon K edge. In addition, linear dichroism microscopy exploits the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays. Previous x-ray linear dichroism microscopy work has demonstrated the ability to determine the orientation of specific chemical groups within polymeric systems at high spatial resolution. Here, we have extended this technique to quantitatively determine the degree of radial order in various grades of poly(p-phenylene terephthalamide) (Kevlar™) fibers.

The orientational dependence of the absorption cross-section yields “butterfly” patterns when thin sections of certain grades of Kevlar fibers cut at 45° with respect to the fiber axis are imaged at specific photon energies.
Temperature ramp dependent reaction kinetics of internal tin processed Nb3Sn wires
Authors: Sabatini R. L. , Zhu Yimei , Suenaga M.
Published: June 2020

Multifilamentary Nb3Sn wires will be a critical component of a magnetic fusion reactor, which requires a high magnetic field for confinement of the plasma. The international effort to demonstrate the feasibility of the reactor design (International Toroidal Engineering Reactor, ITER) has very stringent requirements for the hysteresis loss and the critical current density Jc(≤ 600 mJ/cm3 and ≥700 A/mm2, respectively) of the Nb3Sn wires which are to be used for the central toroidal field coil magnet. Although short wire specimens can meet these requirements, consistently fabricating long lengths of wire meeting these specifications is not trivial. A part of this inconsistency is related to the effects of the temperature ramp rate on these critical properties. Thus, to investigate the observed ramp rate dependencies a metallurgical examination was performed. Samples of wires were subjected to two controlled temperature ramp cycles. Wire cross-sections were examined from samples removed at various stages of the two ramp cycles.
Characterization of pulsed laser deposited Zno-WS2 thin solid film lubricants
Authors: Walck S. D. , Zabinski J. S. , McDevitt N.T. , Bultman J. E.
Published: June 2020

ZnO-WS2 is a potential high temperature solid film lubricant for aerospace applications that exhibits adaptive lubricant behavior. An adaptive lubricant undergoes phase and/or chemical changes in response to thermal, environmental, and tribological conditions; with the resulting phase or wear debris also being lubricious. Pulsed laser deposited (PLD) ZnO-WS2 thin films deposited at room temperature (RT) and wear-tested at room temperature have been shown to have coefficients of friction of 0.04 or less which are comparable to WS2 films, but have much longer wear lives. In the as-deposited state, PLD ZnO-WS2 films are amorphous, but when wear-tested, the phases WS2, WO3, and ZnWO4 are produced. Of these, WS2 is a lubricant phase at low temperatures (⪯ ~450°C) while ZnWO4 is a lubricant phase above about 600°C. The purpose of this work was to characterize the microstructural and chemical changes that occur when the RT-PLD ZnO-WS2 films are heated in air.

The RT-PLD ZnO-WS2 films were deposited in a system having a base pressure of 9×l0-7 Pa with a typical pressure during deposition of 6×10-5 Pa.
Quantitative measurement of experimental parameters for high-resolution EM images in fourier space
Authors: Zheng T. , Gibson J. Murray
Published: June 2020

Due to the multiple scattering and interference intrinsic in high resolution transmission electron microscopy (HRTEM) images, interpretation of HRTEM images is difficult. In order to interpret contrast details in a HRTEM image, simulated images for various proposed structure have to be obtained until good agreement is reached. The usual multislice method for image simulation is extremely time-consuming and has to be repeated for each structure under consideration. Also, the experimental parameters, for example objective lens defocus and sample thickness etc., are related to image details in HRTEM images. Knowledge of these experimental parameters is essential for the image interpretation and is important for quantitative interface analysis, for example chemical mapping by Ourmazd and colleagues. Thust and Urban have reviewed the conventional method for measuring sample thickness and objective lens defocus value and proposed a method for sample thickness and defocus determination. But their method requires synchronous sampling of experimental images under consideration, which is not always possible for on-line digitized images in order to retain the resolution. And experimental and simulated images have to be perfectly aligned.
Surface chemical sensitivity combined with high-resolution EM
Authors: Landree E. , Collazo-Davila C. , Grozea D. , Plass R. , Jayaram G. , Marks L.D. , Stair P.C.
Published: June 2020

Although high resolution electron microscopy (HREM) has proved to be an invaluable tool in the study of surfaces, one critical drawback is its inability to obtain specific surface chemical state information. The ideal investigation would combine the imaging capabilities of HREM with the surface chemical information obtainable from X-ray Photon Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) without exposing the sample surface to possible contaminants. We have taken a step in this regard with the addition of a new Specimen Preparation Evaluation and Analysis for Research (SPEAR) side chamber to the existing Hitachi UHV-9000 microscope, designed by Superior Vacuum Technology (Figure 1). Currently we are able to combine all of the imaging tools of HREM with surface chemical sensitivity, in an attempt to achieve the ideal surface analysis instrument.

Samples are introduced and retrieved from the system through a load-lock mechanism. Pumped by a 210 Liter/sec Balzers’ Turbomolecular pump, this introduction chamber is capable of going from atmospheric pressure to 10-10 torr in four to eight hours.
The CM120 Biotwin: a high-contrast objective lens, optimum cryo-vacuum and improved EDX performance
Authors: Lücken Uwe , Felsmann Michael , Busing Wim M. , de Jong Frank
Published: June 2020

A new microscope for the study of life science specimen has been developed. Special attention has been given to the problems of unstained samples, cryo-specimens and x-ray analysis at low concentrations.

A new objective lens with a Cs of 6.2 mm and a focal length of 5.9 mm for high-contrast imaging has been developed. The contrast of a TWIN lens (f = 2.8 mm, Cs = 2 mm) and the BioTWTN are compared at the level of mean and SD of slow scan CCD images. Figure 1a shows 500 +/- 150 and Fig. 1b only 500 +/- 40 counts/pixel. The contrast-forming mechanism for amplitude contrast is dependent on the wavelength, the objective aperture and the focal length. For similar image conditions (same voltage, same objective aperture) the BioTWIN shows more than double the contrast of the TWIN lens. For phasecontrast specimens (like thin frozen-hydrated films) the contrast at Scherzer focus is approximately proportional to the √ Cs.
The information limit of a 200kv field emission TEM
Authors: Kaneyama T. , Kawasaki M. , Tomita T. , Honda T. , Kersker M.
Published: June 2020

The Point resolution of a transmission electron microscope is normally defined by the reciprocal of the spatial frequency of the first zero in the phase contrast transfer function at the Scherzer defocus condition. When a field emission gun (FEG) is used as the electron source, the information limit, that point at which the contrast beyond the first zero goes to zero contrast, becomes equally important. We have investigated the primary microscope parameters that affect the information limit.

A 200kV FE-TEM (JEM-2010F) equipped with a ZrO/W shottkey emitter and Gatan Parallel EELS (PEELS) was used for the experiments. The aberration coefficients of the objective lens are Cs = 1mm and Cc = 1.4mm. The specimen used is an evaporated amorphous Ge thin film with small gold islands.

The resolution performance of the microscope depends not only on the performance of the objective lens, the high voltage stability, stability of the lens and deflector power supplies, operating parameters of the FEG, and the overall mechanical stability of the microscopes.
Reconstruction of low-voltage point-projection holograms of mask-like objects
Authors: Zhang X. , Kruit P. , Qian W. , Spence J. C. H.
Published: June 2020

Point-projection shadow images (PPM) are obtained by placing a nanotip field emitter at a potential of a few hundred volts close to a grounded sample, which acts as the anode. It can be shown that the shadow image is identical to an conventional out-of-focus TEM image with a defocus equal to the tip-to-sample distance z1, and is an in-line hologram. Recent work shows that most objects used for PPM may be treated as opaque masks containing holes, since the inelastic mean free path (IMF) for 100 eV electrons is 6-8Å in carbon. The question arises if the mask shape can be reconstructed from the shadow image, i.e. if the image can be brought back into focus. For masks, Fresnel edge fringes constitute most of the hologram (apart from interference between different holes). Fresnel fringes and shadow images were first observed by Boersch, prior to Gabor's demonstration that, for small opaque objects, they could be removed by holographic reconstruction or “focus restoration”.
An integrated digital image acquisition and archiving system for diagnostics and education in pathology
Authors: He F. , Schubert E. , Gross W. , Mancini M. , Mahoney T. , Wimberley F. , Roskies R. , Levine M. , Becich M.
Published: June 2020

Background Advances in digital imaging technology and instruments have profoundly enhanced the way of decision-making in diagnostic pathology. The image that was typically recorded on film and stored in different divisions of the department in the past can now be stored via a centralized image file server. Since pathology images are derived from gross surgical specimens, light, immunoflourescence, electron microscopy and clinical laboratory data in graphical forms, it is essential to have an integrated system to manage and distribute the images. The images along with attached text information should be rapidly stored in a fashion of pathologist's perspective, and be viewed on their desktop computers with an absolutely minimal impact on existing work flow. In addition, the images originated from individual patients should be easily reorganized or grouped for the purposes of medical training and on-line conferences. Having identified these basic requisitions, we have recently implemented such a system in our department.
Estimation and analysis of 3-D chromosome motion
Authors: Marshall W.F. , Agard D.A. , Sedat J.W.
Published: June 2020

The mechanical properties of chromosomes in vivo are at present poorly characterized, yet an understanding of such properties is likely to be important for understanding both the behavior of chromosomes during mitosis as well as the establishment and maintenance of specific chromosome configurations in the nucleus. In order to better investigate the mechanics of chromosomes inside living cells we have developed algorithms for quantitative analysis of chromosome motion. This allows us to directly determine chromosome mobility, and to visualize the trajectories of specific regions, such as telomeres or centromeres. Previously developed tools for analysis of 3D structure can then be extended to 4 dimensions, allowing quantitative description of chromosome behavior. The motion vector field itself can also be analyzed for specific patterns of motion.

Three dimensional motion estimation is difficult in fluorescence microscopic images, due to limited spatial resolution, particularly in the axial direction, which result in a significant aperture problem because each part of a chromosome looks identical to any other part of any other chromosome, such that intensity patterns are not useful in motion estimation.
The energy filtering TEM (EFTEM) in modern biological transmisson Electron Microscopy
Authors: Probst W. , Bayer V.E.
Published: June 2020

Modern biological electron microscopy can no longer be a static tool merely describing morphology. In addition to ultrastructural information, insights into the molecular and chemical composition of a sample are needed so that new findings stemming from molecular biological and biochemical analyses can be given meaning in an ultrastructural context. Biological electron microscopy will be an essential tool for future discoveries involving the ultrastructural localization of molecules and chemical elements, and it will provide a means to identify the ultrastructural basis for a variety of reaction mechanisms. Many messenger compounds are currently known which can produce dynamic changes of either a subtle or dramatic nature at the ultrastructural level, but only the most basic of these can be examined using a conventional transmission electron microscope (CTEM). CTEMs provide limited information because they perform conventional imaging and do not employ all the signals available for analysis. Unlike a CTEM, an EFTEM permits the selection of a defined energy (wavelength) of electrons which are then used for imaging.
A few words on bits & bytes: a tutorial on image and spectral processing for the novice
Authors: Mansfield John F.
Published: June 2020

We are now in a position, in the world of microscopy and microanalysis, to record all of our data digitally and often, the first time that the data is printed out is when it is submitted for publication, although there are distinct possibilities that we shall soon be publishing electronically too. Digital image acquisition schemes are largely the realm of the microscope manufacturers, however, there are also a multitude of “homemade” acquisition systems in microscope laboratories around the world. Such a wide variety of systems leads to a wide variety of data storage formats. For example, a any one time there have been at least 6 manufacturers of X-ray Energy Dispersive Spectroscopy (XEDS) systems, each with their own proprietary data format, which, frequently, was not explained to the user. The philosophy was: “Our system is all you will ever need, so you don't need to know how the data is stored”.
Analytical solutions for complex problems using multiple diagnostic techniques
Authors: Heimbrook L. A.
Published: June 2020

The ability to apply multiple diagnostic techniques to complex material, biological, and device problems with the goal of obtaining analytical solutions is the daily objective of the typical analytical laboratory. This paper will describe the use of both microscopy and surface analysis diagnostic tools to evaluate routine and highly complex material and device problems often found in the semiconductor industry. The characterization requirements for silicon and III-V materials and devices cover a wide range of technology research and development programs. These programs involve the characterization of starting materials, doping and implant technologies, thin film technology, particle and contamination issues and final device inspection. Continued advances in ultra-shallow silicon devices and multi-quantum-well (MQW) lasers rely on the accurate introduction of doping elements, the ability to deposit high quality materials of specified layer thicknesses and on advances in fabrication and characterization tools.

The complex analysis problems of evaluating ultra shallow junctions in sub-micron silicon devices and the measurement of grating depths and duty cycles in semiconductor lasers are the characterization challenges which will be addressed in this paper.
Comparative investigation of a Pd/Al2O3 catalyst system with TEM and STEM
Authors: Liu D. R. , Pennycook S.J. , Yao M. H. , Hoost T. E.
Published: June 2020

Pd-only catalysts are attractive for automotive applications because of the low cost and wide availability of Pd compared with that of Pt and Rh. Analytical electron microscopy may be used to investigate the dispersion, which is a very important parameter in catalyst characterization, of the Pd particles on γ-Al2O3 supports. It was of interest to compare how two different techniques, TEM and STEM, might be used for the Pd-particle size determination in a model catalyst. The model system of 1wt%Pd/γ-Al2O3 used in the present study was prepared by the incipient wetness technique from a palladium nitrate solution. It was then dried at 120°C and calcined at 400°C, followed by steam aging at 600 °C for 24 hours. The TEM used was a JEOL 2000FX operated at 200 kV whereas the STEM used was a VG Microscopes HB-501UX operated in the Z-contrast mode at 100 kV.
Structural studies of immunodeficiency viruses
Authors: Maleeff Beverly E. , Hart Timothy K. , Hoxie James A. , Bugelski Peter J.
Published: June 2020

Immunodeficiency viruses (IV) are retroviruses belonging to the subfamily Lentivirinae and include human (HIV) and simian (SIV) immunodeficiency viruses. In this study, we focus on the structure of proteins in SIV isolated from macaques (SIVmac). IV form by budding through the surface of an infected cell, where viral proteins and RNA are enveloped by the host cell bilayer membrane. Immature virions consist of this outer membrane studded with surface glycoprotein projections and a thick sub-envelope protein plaque composed of unprocessed Pr55gag protein. Viral maturation is marked by cleavage of this protein by a viral protease into the structural proteins p17, p24 and p15. Mature virus particles are icosahedral, approximately 120 nm in diameter, consisting of membrane surface glycoprotein projections, a thin submembrane p17 protein layer, a centrally located core capsid composed of p24 protein subunits surrounding the viral ribonucleic acid, and nucleocapsid proteins p7 and p6, derived from processed p15. One step in the development of anti-IV treatments is to understand the organization of the proteins in order to determine specific sites to target chemotherapeutic agents.
Microscopy and microanalysis of calcification in the developing and adult barnacle
Authors: Brimer Crystal M. , Roberts Edward , Hockett Daniel , Freudenrich Craig C. , LeFurgey Ann
Published: June 2020

The barnacle begins its development in its first larval stage, the naupilus, and matures to the larval cyprid stage. Permanent attachment of the barnacle occurs between the cyprid and juvenile stages. Soon after, calcification takes place and the shells of the barnacle grow upward. The application of secondary electron imaging (SEI) and electron probe microanalysis (EPXMA) has defined the time course of calcification and shell growth in the barnacle. Freeze-dried cryosections of the larval cyprid stage can also be employed for localization of calcium at the cellular level with scanning transmission electron microscopy (STEM)/EPXMA; however these sections are unstained, thereby offering very little contrast and making the recognition of ultrastuctural compartments difficult. In an attempt to identify these structures, conventional fixation staining and transmission electron microscopy (TEM) will be used. The light microscopic study of the cyprid has been extensive, but very little ultrastructural research has been conducted. The goal of this study is twofold: to use light microscopy (LM) and TEM as guides in identifying structures of the STEM/EPXMA cryosections; and to follow the growth of the barnacle by using STEM/EPXMA to detect calcium tracers in the shell.
Three muscle isoforms of α-actinin form unipolar actin bundles
Authors: Taylor K. A. , Taylor D. W.
Published: June 2020

α-Actinin is an F-actin binding protein that is ubiquitous in eucaryotic cells. It is the smallest member of the spectrin superfamily and consists of two, identical polypeptide chains of 95-103 kDa. α-Actinin is an elongated molecule of 34 nm length and consists of a string of peptide domains with different functions. The N-terminal domain of ˜255 residues has actin binding activity, the central core consists of four 122 residues triple-helical repeats and the C-terminal domain contains two E-F hand Ca2+ binding motifs.

The physiological importance α-actinin lies in its subcellular location and its interactions with other proteins. The F-actin crosslinking activity of α-actinin is its best known function. In striated muscle aactinin is found in the Z-disk. In smooth muscle, α-actinin is found in both cytoplasmic dense bodies, which are analogs of the Z-disk, and adhesion plaques, which are cell membrane anchoring sites of actin filaments. In dense bodies and Z-disks, oppositely oriented, unipolar bundles of actin filaments overlap so it has been commonly assumed that α-actinin is functioning as a bipolar crosslinker but the unipolar orientation of actin filaments at the cell membrane implies a unipolar bundling activity.