bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructure of Nb BASED A12O3 Composites
Authors: Scheu C , Dehm G , Kaplan W D , Garcia D E , Claussen N 
Published: July 2020

Abstract
Metal-ceramic composites possess a wide range of applications due to an increased fracture toughness and strength compared to monolithic materials. A better understanding of the correlation between properties and microstructure of these materials requires a detailed analysis of the phases which form during processing. This can be accomplished by using various transmission electron microscopy (TEM) methods. In this study Nb based AI2O3 composites were investigated. The composites were prepared by pressureless sintering 2 of compacts of attrition milled AI2O3 and prealloyed Nb(Al) powder mixtures. The addition of 7 wt.% of Al to the Nb powder is supposed to assist in rapid and complete sintering of the material. The microstructure was studied in detail by conventional TEM using selected area diffraction (SAD). The chemistry and structure of the occurring phases, second phase particles and grain boundaries were analysed by analytical TEM and high resolution TEM (HRTEM).
Photo-Electron Emission Microscopy of Semiconductor Surfaces
Authors: Nemanich RJ , English SL , Hartman JD , Yang W , Ade H , Davis RF 
Published: July 2020

Abstract
The technique of photo-electron emission microscopy (PEEM) is based on imaging of photo excited electrons from a surface. Typically ultra violet (UV) light above the work function of a metal will cause electrons to be emitted from a surface. Since photo excited electrons originate very near to the surface, they essentially reflect the electronic structure of the surface. These electrons may be accelerated and imaged, and the image will reflect the properties of the surface.
While the PEEM technique has been understood in a basic sense for many years, it has been limited by the lack of high intensity UV light sources. The most crucial part of the electron imaging system for PEEM, the objective lens, is essentially the same as for the sister technique of low energy electron microscopy (LEEM), and advances in electron optics capabilities have been exploited both for LEEM and for PEEM.
In Situ Electron Microscopy Studies of Surface Dynamical Processes
Authors: Tromp Ruud M 
Published: July 2020

Abstract
To obtain a full and detailed understanding of the spatiotemporal dynamics of surface processes such as epitaxial growth, strain relaxation, phase transformations and phase transitions, chemisorption and etching, in situ real-time observations have proven to be invaluable. The development of two experimental techniques, i.e. Low Energy Electron Microscopy (LEEM) typically operating at electron energies below 10 eV, and Ultra-High-Vacuum Transmission Electron Microscopy (UHV-TEM) at several 100 keV, has made such in situ studies routinely possible. In many cases, the videodata obtained from such experiments are amenable to detailed, quantitative analysis, yielding statistical, kinetic and thermodynamic information that cannot be obtained in any other way.
I will discuss recent experimental developments, including the design and construction of a new and improved LEEM instrument. Figure 1 shows a schematic diagram of this new machine. There are several features that distinguishes this design from most other LEEMs. One is the use of a 90 degree deflection magnetic prism array,
Tem Observations of Interfacial Defects in Mocvd GaAs on Single Crystal Ge Substrates
Authors: Jones KM , Al-Jassim MM , Olson JM 
Published: July 2020

Abstract
The growth of high quality GaAs layers on single crystal Ge substrates has attracted a great deal of interest in recent years. Currently under development at NREL is the GaAs/GalnP-on-Ge high efficiency multi-junction solar cell. Unlike other heteroepitaxial systems such as GaAs-on-Si, physical properties such as the lattice parameter and thermal expansion coefficient of the Ge and GaAs are much closer. Further, Ge has a bandgap of 0.7 eV that makes it a suitable bottom cell in a multi-junction stack. However, the growth of GaAs on Ge is not a straightforward process, and little is known about the Ge surface and the nucleation of GaAs on Ge in the MOCVD environment. In this study, TEM results show that a number microstructural defects are associated with the Ge/GaAs interface and the initial stages of growth.
Tem Investigation of Co-Si Thin Films on S1-xGex/Si
Authors: Myersa A F , Goeller P T , Steel E B , Boyanov B I , Sayers D E , Nemanich R J 
Published: July 2020

Abstract
Cobalt disilicide (CoSi2) is an attractive contact material for Si1-xGex devices due to its low resistivity, low Schottky barrier, and good thermal and chemical stability. Previous studies have shown that blanket Co films on Si0.80Ge0.20 react at annealing temperatures of 700 °C to form CoSi, CoSi2 and a Ge-rich Si1-xGex alloy; no Co-Ge phases were found. The Co preferentially reacts with the Si, which can lead to Ge segregation and island formation. To gain a better understanding of cobalt silicide formation, an electron microscopy investigation of Co/Si1-xGex/Si was performed.
Si1-xGex films (x ≤ 0.3) 64 nm to 260-nm thick were grown by molecular beam epitaxy at 550 °C on phosphorus-doped Si &lt;001&gt; substrates. Co films ranging in thickness from 5 nm to 25 nm were electron-beam evaporated (evaporator base pressure &lt; 6.67 x 10-8 Pa) at room temperature on the Si1-xGex films.
Ge distribution in Gi80Ge20 Islands Grown in the High Mobility Regime.
Authors: Twesten RD , Floro JA , Chasonf E 
Published: July 2020

Abstract
Strained epitaxial films are often unstable to morphological transformations. The classic example of this phenomenon is the SiGe system. A nonplanar morphology results in non-uniform strains in the system (Figure 1). These strain fields can modify the local chemical potential of a uniform alloy driving Ge enrichment in the regions of low compression.
Recent work has shown that annealed films of SiGe on Si{001} exhibit both vertical and lateral segregation during the transition from a metastable planar film to an array of ﹛100﹜ directed island. Vertical segregation is evidenced by an enrichment of Ge in the last few monolayers of the film while lateral segregation is seen as an enhancement of this surface layer in the region near the island peaks. This segregation is due to surface diffusion as the bulk diffusion lengths are too short. The case of annealed, metastable films can be compared to growing films.
Kinetics of the C-Axis Aligned YBa2Cu3O7 Thick Film By a BaF2 Process
Authors: Wu Lijun , Zhu Yimei , Solovyov VF , Wiesmann H , Suenaga M 
Published: July 2020

Abstract
Over the last few years, considerable efforts have been made in developing fabrication processes for thick superconducting YBa2Cu3O7-δ film on a metallic substrate for electric power applications. Since these applications require the composite tape to be longer than 4-500m, any methods chosen need to be compatible with such length requirement. One possible approach is the so-called BaF2 process which involves deposition of a unreacted mixture of a BaF2-Y-Cu-O layer on a substrate by an electron beam evaporation method, followed by heat-treatment of the layer in a mixed-gas atmosphere of a low partial pressure O2, saturated H2O, and N2. Although it was shown previously that c-axis aligned films up to ∼ I m long can be produced under these conditions it is uncertain how thick the films can be made and this is of crucial importance as most applications require film thickness to be greater than ∼5μm to carry a large, dissipationless current.
Microstructure of YBCO/Co-PBCO/YBCO edge Josephson junctions
Authors: Huang Y , Moeckly BH , Merkle KL 
Published: July 2020

Abstract
In recent years, many efforts have been made to fabricate high-Tc superconductor/normal-metal/ superconductor (SNS) Josephson junctions, but no breakthrough has been made. The major difficulties are the poor reproducibility of the junction parameters due to the structural complexity and defects in the barrier layer. Some junctions, such as the one with Co-doped YBCO barrier, have relatively small spreads in properties. However, the value of their normal state resistance Rn is low, which limits their use for many applications. One approach to solve this “low-Rn” problem is to use materials of high resistivity for the barrier layer. PBCO is an insulator near the metal-insulator transition. Doping with Co drives it further into the insulating regime. The lattice constants of PBCO are close to that of YBCO, even closer when doped with Co. Therefore, Co-PBCO may form a high-resistivity barrier which matches with YBCO very well and hence is a potential candidate barrier material.
Graphitic Disks or Polygons? Faceting of Graphite Disks
Authors: Krishnan A , Dujardin E , Ebbesen TW , Treacy MMJ 
Published: July 2020

Abstract
The recent discovery of graphite cones [1,2] has raised some interesting questions about the nucleation and growth of curved graphitic structures. Here we report the structural peculiarities of one member of the ensemble, i.e. the flat graphite disks. Unlike graphite flakes seen in carbon soot which are irregularly shaped, the disks in this sample often show regular faceting which might give us additional insight into the growth mechanisms.
The samples were examined in a Hitachi H9000 NAR TEM. Samples were sonicated in high purity methanol and dispersed on a 300 mesh Cu grid coated with a 20 nm thick amorphous carbon layer. Typical disk diameters range from 0.5 to 3.0 μm, with thickness ranging from 10 nm to 50 nm.
A close examination reveals that the edges of the disks are faceted and typically have 12 sides. In most cases, the edges show a long facet alternating with a shorter facet.
A Study of Amorphous Chalcogenides by Electron Microscopy and Analysis
Authors: Fitzgerald A G , Mietzsch K 
Published: July 2020

Abstract
Amorphous chalcogenides films coated with certain metals are known to possess a remarkable sensitivity to radiation. Based on these effects they have found several important applications in the production of microcircuits, e.g. as resists in photo- and electron beam lithography. A variety of chalcogenides in combination with a range of metals has been extensively investigated with regard to potential applications in the fabrication of semiconductor devices.
The objectives of the present project are to extend knowledge of the behaviour of amorphous chalcogenides in contact with metals. This includes studying the metal diffusion process, understanding the film-electron beam interaction process and evaluating the potential of the metal lines formed by the electron beam in fabrication of photomasks for the production of higher densities of silicon microcircuits.
Structural Stability of Nanocrystalline NiAl
Authors: Chen T , Hampikian JM , Thadhani NN , Wang ZL 
Published: July 2020

Abstract
NiAl is an important high temperature structural material, with a high melting point (1640°C), low density and excellent high temperature oxidation resistance. The room temperature ductility of NiAl may potentially be improved with the use of nanocrystalline grain size. However, a key question concerning the application of nanostructured NiAl is about its structural stability at high temperature. The current study is thus focused on the investigation of the structural stability of nanocrystalline NiAl using in-situ transmission electron microscopy (TEM) and differential thermal analysis (DTA).
Nanocrystalline B2-NiAl was prepared by ball milling (24 hrs) from elemental Ni and Al powders. Subsequent consolidation into bulk form was performed using dynamic consolidation employing a 3-capsule plate-impact fixture at approximately 400 m/s [1-3]. Powder nanocrystalline NiAl was dispersed on a holey carbon film for TEM observation. TEM specimens of shock compacted bulk NiAl nanocrystals were prepared by cutting, polishing, dimpling and ion milling.
The Experimental Accuracy of Lattice Spacing Determination on Small Metal Particles in Commercial Catalysts
Authors: Tsen S-C Y , Crozier P A , Liu J 
Published: July 2020

Abstract
A description of the microstructure of heterogeneous catalysts is important in understanding the mechanisms for catalysis and may result in improvements in catalyst performance. Many commercial catalysts consist of small metal particles and/or metal oxide particles dispersed on a porous support. For bimetallic catalysts, the metals may be in the form of alloys, metal mixtures or completely phase separated. HREM has been demonstrated to be a powerful technique for determining the lattice spacing from small particles[l]. In many studies of catalysts it is necessary to prepare TEM samples by microtomy so that the particle location relative to the porous support is preserved. However, such samples show a reduction in particle visibility and signal-to-noise ratio of lattice fringes. In spite of these difficulties, we have been able to routinely use HREM to rapidly determine the relative distributions of metal and metal oxides in many systems because of the large difference in spacing between strong reflections from the metal and metal oxide (typically 20 %).
Microstructural Analysis of Disordered and Ordered Mesoporous Silica Films
Authors: Drewien C A , Lu Y , Brinker C J , Ganguli R , Anderson M T 
Published: July 2020

Abstract
Processing can be controlled to produce a family of mesoporous silica films with either disordered, lamellar, hexagonal, or cubic pore distributions[l]. These films, formed by surfactant-templated synthesis and exhibiting a unimodal pore size, promise potential use as inorganic membranes, catalysts, and optically-based sensors[l,2]. The mesoporous films can be formed from initially homogeneous silica sols by a continuous, surfactant-templated process, which relies upon solvent evaporation during the sol-gel dip-coating process. Films of 100-500 nm thick are formed within seconds in a continuous coating operation. The microstructure of the films is dependent upon the cationic surfactant concentration CTAB (CH3(CH2)15N+(CH3)3Br-) and the dip-coating rate. Several films, processed under differing conditions, were investigated by TEM to characterize pore size, structure, and orientation.
Figures 1 a & b show the plan view and cross-sectional microstructure of a 2-d hexagonal mesoporous silica film deposited on silicon; the sample was calcined at 400 °C for 3 hours in air. The images were obtained on a Philips CM30 TEM, operated at 300 kV.
Interfacial Solute-Atom Segregation: An Atomic-scale Ahenomenon with Implications for the Oxidation Kinetics of Pt-Al Alloys
Authors: Dickey EC , Alexander KB , Pint BA 
Published: July 2020

Abstract
Interfacial solute-atom segregation is known to have profound effects on macroscopic physical properties (e.g. electronic transport or fracture toughness) in interface-influenced or controlled materials. It has recently been shown that solute-atom segregation also can play an influential role in the dynamics of phase transformations, in particular the oxidation kinetics of alumina-forming alloys such as PtAl. By coupling analytical electron microscopy (AEM) with conventional macroscopic oxidation studies, we have demonstrated that oxidation kinetics are affected by atomic-scale segregation of dopant species to the grain boundaries and metal-oxide boundaries in the system. Furthermore, these studies illustrate the utility of AEM techniques in elucidating the atomic-scale aspects of macroscopic physical phenomena such as phase transformations.
Oxidation studies were carried out on PtAl alloys with and without small additions of Zr to the alloy. While the pure PtAl alloys exhibited oxide scale spallation and very fast oxidation rates, the Zrcontaining alloys maintained a well-adhered oxide scale and significantly lower oxidation rates.
The Measurement of Light Element Segregation Using EDS and EELS
Authors: Busby JT , Kenik EA , Was GS 
Published: July 2020

Abstract
Radiation-induced segregation (RIS) is the spatial redistribution of elements at defect sinks such as grain boundaries and free surfaces during irradiation. This phenomenon has been studied in a wide variety of alloys and has been linked to irradiation-assisted stress corrosion cracking (IASCC) of nuclear reactor core components. However, several recent studies have shown that Cr and Mo can be enriched to significant levels at grain boundaries prior to irradiation as a result of heat treatment. Segregation of this type may delay the onset of radiation-induced Cr depletion at the grain boundary, thus reducing IASCC susceptibility. Unfortunately, existing models of segregation phenomena do not correctly describe the physical processes and therefore are grossly inaccurate in predicting pre-existing segregation and subsequent redistribution during irradiation. Disagreement between existing models and measurement has been linked to potential interactions between the major alloying elements and lighter impurity elements such as S, P, and B.
Interface Characterization of Metallized CVD Diamond
Authors: Menon E S K , Saunders M , Dutta I 
Published: July 2020

Abstract
Progress towards the large scale integration of active devices within electronics packages has imposed stringent heat dissipation requirements necessitating the development of innovative materials solutions. One possibility being considered is the use of chemically vapor deposited diamond (CVDD) thin films as heat sinks. However, there are technological challenges which must be overcome before these materials become commercially viable. For example, the CVDD substrate must be metallized to provide interconnections between the various devices in the package. Conventional metallizations, such as Au, Cu or Al, display poor adhesion to the diamond causing problems associated with the reliability and stability of metallized diamond packages. A novel solution has been proposed involving the consecutive deposition of a thin layer of Cr and an electrically insulating layer of alumina on the diamond substrate such that the thermal conductivity of the treated substrate is not degraded significantly.
Hrem Characterization of Magnetic Tunnel Junctions and Discontinuous Multilayers
Authors: Smith David J , Ge Fuding , Piatt CL , Sankar S , Berkowitz AE 
Published: July 2020

Abstract
There is much current interest in the magnetotransport properties of systems consisting of two (or more) magnetic metal layers separated by thin insulating layers. Traditional magnetic tunnel junctions (MTJs) are comprised of simple ferromagnet-insulator-ferromagnet trilayer structures and the conductance depends on the relative alignments of the magnetizations in the two ferromagnets. In the case of discontinuous metal/insulator multilayers, negative magnetoresistance (MR) results from spindependent tunneling. In both types of systems, the tunneling phenomena are strongly influenced by the microstructure of the films, particularly the metal/insulator interfaces and the nature and uniformity of the thin oxide barrier layers. In this study, we have used cross-sectional HREM to characterize a variety of magnetic tunnel junctions and discontinuous multilayers.
The MTJs were prepared by rf and dc magnetron sputtering onto thermally oxidized (100) silicon wafers at room temperature. The magnetic layers consisted of thin films of Co, Fe and/or CoFe alloys with thicknesses ∼ 30-50nm, and the barriers included MgO, HfO2, CoO, SiO2 as well as Al2O3 (thicknesses in the range 2-10nm).
Quantitative Chemical Speciation of Multi-Phase Polymers Using Zone Plate x-ray Microscopy
Authors: Hitchcock AP , Urquhart SG , Ade H , Rightor EG , Lidy W 
Published: July 2020

Abstract
Phase segregation is important in determining the properties of many complex polymers, including polyurethanes. Achieving a better understanding of the links between formulation, chemical nature of segregated phases, and physical properties, has the potential to aid development of improved polymers. However, the sub-micron size of segregated features precludes detailed chemical analysis by most existing methods. Zone-plate based, scanning transmission X-ray microscopes (STXM) at NSLS and ALS provide quantitative chemical analysis (speciation) of segregated polymer phases at ∼50 nm spatial resolution. Image sequences acquire much more data with less radiation damage, than spot spectra. After alignment, they provide high quality near edge spectra, and thus quantitative analysis, at full spatial resolution.
Fig. 1 shows an image and spectra acquired with the NSLS STXM of a macro-phase segregated TDI polyurethane. Spectral decomposition using model polymer spectra is used to measure the local urea, urethane and polyether content.
The Morphology of Carboxylated Composite Latex and Latex Film
Authors: Shaffer O L , Sandor M W , El-Aasser M S 
Published: July 2020

Abstract
Carboxylated latex has become very important in the formation of polymer films. In order to study the film and its properties it is important to know the morphology of the latex that is forming the film. The latex for this study has been examined by transmission electron microscopy(TEM) using positive preferential stains such as ruthenium tetroxide (RuO4) and cesium hydroxide(CsOH); and uranyl acetate(UAc) as a negative stain.
The polybutyl acrylate(PBA)/ polymethylmethacrylate(PMMA) composite latex particles consist of a soft core phase and a hard second phase with varying amounts of acrylic acid in the core, the shell and in both core and shell. The latexes were examined before and after cleaning. The cleaning was necessary in order to remove the surfactant and any small particles that might have formed during the emulsion polymerization. Prior to cleaning, the small particles adhered to the surfaces of the particles making it difficult to determine the final morphology of the latex particles.
UV Absorption Microspectrophotometry and Histochemistry of Flax and Kenaf
Authors: Akin DE 
Published: July 2020

Abstract
Flax (Linum usitatissimum L.) and kenaf (Hibiscus cannabinus L.) are the sources of fibers used for textiles and other industrial applications. Both flax and kenaf produce fibers in the bast region (Fig. 1, 2) which must be separated from other tissues by retting. Although both flax and kenaf are bast fibers, their properties are vastly different. UV absorption microspectrophotometry and histochemistry elucidate their chemistry and structure related to enzymatic retting.
Aromatics such as lignins are produced by plants for protection and strength, but their presence inhibits microbial degradation, which is necessary in retting. Histochemical tests indicated variations in the site and type of aromatics within these two plants (1,2). In flax, acid phloroglucinol but not chlorine-sulfite gave positive reactions occasionally in fiber cell walls in the bast. The other cell walls in the bast did not contain aromatics by these tests, although aromatics occurred in the cuticle.
Microwave Processing of Cell Monolayers in Situ for Postembedding Immunocytochemistry with Retention of Ultrastructure and Antigenicity
Authors: Madden Victoria J 
Published: July 2020

Abstract
Increasingly, cells isolated from blood and body fluids and cells grown in culture are becoming the experimental models of choice for biological research. The demand for demonstrating biochemical processes morphologically is also becoming commonplace in the electron microscopy laboratory. Successful fixation, in situ embedment, and ultrathinsectioning of cell monolayers can be difficult to achieve for routine transmission electron microscopy. For postembedding immunocytochemistry, processing becomes more complex due to fixation constraints and the use of acrylic resins. The object of this paper is to present a reliable, rapid method for processing monolayers that preserves both the ultrastructure of the cells and antigenicity.
The equipment used for this procedure was a Pelco Model 3440 MAX laboratory microwave oven equipped with a temperature probe and a maximum power output of 800 watts. Using a neon bulb array, the oven cavity is calibrated to determine the microwave energy distribution.