bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin Microcrystalline Silicon by a Microwave Remote Plasma Deposition Scheme for Heterojunction Solar Cells and Thin Film Transistors
Authors: Jagannathan B. , Wallace R. L. , Anderson W. A. 
Published: April 2011

AbstractA microwave remote plasma system, operating in an electron cyclotron resonance (ECR) condition, has been designed to deposit microcrystalline silicon (μ c-Si). The plasma properties have been studied by Langmuir probe measurements in the deposition region. Microcrystalline silicon films of thickness < 0.3 μm have been grown by the decomposition of 2% SiH4/Ar diluted in H2. The films were analyzed for dark and photoconductivity, crystallinity and total H2 content. Raman spectroscopy indicates >50% crystallinity for films deposited between 300–400 °C at pressures of 10 mTorr with an input power in the range of 200–600 W for a H2/SiH4 ratio of 60. An increase in deposition temperature from 300 to 400 °C resulted in an increase in conductivity along with a decrease in the activation energy. H2 evolution studies indicate that the purely μ c-Si films show a total 2.5% H2 content compared with the 16.5% seen for the totally amorphous films. Better structural and electrical properties have more recently been obtained using 2% SiH4/He mixtures.
Microstructure of Thin Film Photoconductors and its Correlation with Optical and Electronic Properthss
Authors: Klement U. , Horst D. , Ernst F. 
Published: April 2011

AbstractThe objective of this work is to find a material to replace amorphous hydrogenated silicon used as photosensitive part in the “retina” of an “electronic eye”. For that reason, ZnS, ZnSe, CdS and CdSe were chosen for investigations. Thin films, prepared by chemical vapour deposition, were characterized by transmission electron microscopy. The observed microstructures were correlated with the optoelectronic properties of these materials. CdSe was found to be the most promising material for our application. Hence, the influence of a dielectric interlayer and the effects of additional annealing treatments were analyzed for CdSe and will be discussed with respect to the optimization of the material.
Single-Crystal Si Films Via a Low-Substrate-Temperature Excimer-Laser Crystallization Method
Authors: Sposili Robert S. , Crowder M. A. , Im James S. 
Published: April 2011

AbstractThis paper describes an extension of the sequential lateral solidification (SLS) method for producing single-crystal Si regions in predetermined locations on thin Si films on SiO2. This is accomplished by manipulating the shape of the solidification front in order to exploit the tendency of grain boundaries to propagate nearly perpendicular to the melt interface. Specifically, we employ a chevron-shaped beamlet to select and grow the grain at the chevron's apex for propagation, resulting in a well-defined single-crystal region. Many such chevrons are processed concurrently—each one leading to a single-crystal region at a precisely determined location, and each one being large enough for complete inclusion of an entire thin-film transistor (TFT) device. Microstructural examination of defect-etched SLS material using optical microscopy reveals unambiguously that single-crystal regions free of high-angle grain boundaries are produced.
Sintering of Sputtered Copper Nanoparticles on (001) Copper Substrates
Authors: Yeadon M. , Yang J. C. , Ghaly M. , Olynick D. L. , Averback R. S. , Gibson J. M. 
Published: April 2011

ABSTRACTThe sintering of sputtered copper nanoparticles with a thin film copper substrate has been studied in real time using a novel in-situ UHV TEM. Particles were generated by dc sputtering in argon and transferred directly into the microscope along a connecting tube. The particles were deposited onto a clean (001) copper substrate of thickness 40nm. As-deposited particles assume a random orientation on the copper substrate as evidenced by electron diffraction patterns. Upon annealing, however, the particles were observed to reorient and assume the orientation of the substrate. Reorientation of individual, isolated particles occurred at ∼200°C, primarily by grain-boundary motion and not by surface diffusion.
The Formation of Metal/Metal-Matrix Nanocomposites by the Ultrasonic Dispersion of Immiscible Liquid Metals
Authors: Keppens V. , Mandrus D. , Rankin J. , Boatner L. A. 
Published: April 2011

ABSTRACTUltrasonic energy has been used to disperse one liquid metallic component in a second immiscible liquid metal, thereby producing a metallic emulsion. Upon lowering the temperature of this emulsion below the melting point of the lowest-melting constituent, a metal/metal-matrix composite is formed. This composite consists of sub-micron-to-micron-sized particles of the minor metallic phase that are embedded in a matrix consisting of the major metallic phase. The zinc-bismuth case was used as a model system, and ultrasonic dispersion of a minor bismuth liquid phase was used to synthesize metal/metal-matrix composites. These materials were subsequently characterized using scanning electron microscopy and energy-dispersive x-ray analysis.
Energetic-Particle Synthesis of Nanocomposite Al Alloys
Authors: Follstaedt D. M. , Knapp J. A. , Barbour J. C. , Myers S. M. , Dugger M. T. 
Published: April 2011

ABSTRACTlon implantation of O into Al and growth of Al(O) layers using electron-cyclotron resonance plasma and pulsed laser depositions produce composite alloys with a high density of nanometer-size oxide precipitates in an Al matrix. The precipitates impart high strength to the alloy and reduced adhesion during sliding contact, while electrical conductivity and ductility are retained. Implantation of N into Al produces similar microstructures and mechanical properties. The athermal energies of deposited atoms are a key factor in achieving these properties.
Nanocrystalline Solid Solutions of Cu/Co and Other Novel Nanomaterials
Authors: Edelstein A. S. , Harris V. G. , Rolison D. , Perepezko J. H. , Smith D. 
Published: April 2011

ABSTRACTA brief review will be given of the preparation, synthesis and properties of the Cu/Co system. The special case of the synthesis of nanocrystalline Cu.80Co.20 by precipitation and reduction of hydroxides is discussed in more detail. It was found that the lattice constant of nanocrystalline Cu.80Co.20. determined from x-ray diffraction measurements, approximately fits Vegard's Law and the average nearest neighbor distance from both the Cu and Co atoms, determined from EXAFS measurements, ir shifted from their bulk values. Samples given the minimum heat treatment needed to reduce the hydroxides contained Co-rich regions. Heat treatments cause the Co to segregate preferentially onto the surface of the Cu crystals. The presence of the Co delays the oxidation of the Cu surfaces.
Micro-Tensile Testing of Nanocrystalline Al/Zr Alloys
Authors: Legros M. , Hemker K. J. , LaVan D. A. , Sharpe W. N. , Rittner M. N. , Weertman J. R. 
Published: April 2011

ABSTRACTA novel micro testing machine has been used to perform tensile tests on nanocrystalline Al/Zr microsamples with grain sizes ranging from 10 to 250 nm. The problems associated with testing such small specimens (200μm × 200μm in the gage section) were overcome by using a contact-free interferometrie strain gage (ISDG) and alignment and low friction loading were assured by use of a linear air bearing. The postulated relationship between yield stress and hardness was investigated and will be discussed. The effect of the microstructure and the grain size of the compacts on their mechanical behaviour are also analysed.
Preparation of Ceramic Nanocomposite with Perovskite Dispersoid
Authors: Nagai T. , Hwang H. J. , Sando M. , Niihara K. 
Published: April 2011

ABSTRACTIn order to introduce ferroelectricity into structural ceramics, we synthesized novel ceramic composites containing submicron sized perovskite-type ferroelectrics (ceramic / perovskite-type ferroelectrics nanocomposites). Although perovskite compounds easily react with other ceramics, MgO/BaTiO3 nanocomposites were successfully fabricated using conventional sintering technique. The microstructure of nanocomposites and the phase stability of the dispersed BaTiO3 particulate are discussed.
Preparation and Characterization of Ag-Cluster in Poly(Methylmethacrylate)
Authors: Yanagihara Naohisa , Ishii Yoshitaka , Kawase Takanori , Kaneko Toshimare , Horie Hisashi , Hara Toru 
Published: April 2011

ABSTRACTSolid sols of silver in poly(methylmethacrylate), Ag/PMMA, were prepared by bulk polymerization of methyl methacrylaite (MMA) with benzoyl peroxide (BPO) as an initiator in the presence of silver(I) trifluoroacetate. Ag/PMMAs were characterized by visible spectroscopy. Effects of the concentration of initiator, the concentration of silver (I) complex and the heat-treatment time on the formation of silver cluster were studied in detail.
Enhancement of Ion Mobility in Aluminosilicate-Polyphosphazene Nanocomposites
Authors: Hutchison J. C. , Bissessur R. , Shriver D. F. 
Published: April 2011

ABSTRACTNanocomposites of poly(bis-(2(2-memoxyethoxy)ethoxy)phosphazene) (MEEP) or cryptand[2.2.2] with the aluminosilicate Na-montmorillonite (NaMont) were studied to develop new solid electrolytes with high conductivity and a unity cation transport number. An aluminosilicate was chosen because the low basicity of the Si-0-Al framework should minimize ion pairing. To further reduce ion pairing, solvating molecules or polymers such as cryptand[2.2.2] or MEEP were introduced into the aluminosilicate. When compared to pristine Na-montmorillonite, impedance spectroscopy indicates an increase in conductivity of up to 100 for MEEP-NaMont intercalates, and of 50 for cryptand[2.2.2]·NaMont intercalates. The MEEP·NaMont intercalate exhibits high ionic conductivity anisotropy with respect to the montmorillonite layers (σpara./σperp. = 100), which is consistent with increased tortuosity of the cation diffusion path perpendicular to the structure layers. The temperature dependance of the conductivity suggests that cation transport is coupled to segmental motion of the intercalated polymer, as observed previously for simple polymer-salt complexes. Nanocomposites of solvating polymers or molecules with aluminosilicates provide a promising new direction in solid-state electrolytes.
The Effect of sulfating on the Crystalline Structure of Sol-Gel Zirconia Nanophases
Authors: Bokhimi  , Morales A. , Novaro O. , Portilla M. , Lopez T. , Tzompantzi F. , Gomez R. 
Published: April 2011

ABSTRACTNanophases of sol-gel zirconia were prepared with HCl, C2H4O2 and NH4OH as hydrolysis catalysts, and sulfated with H2SO4. They were analyzed by using X-ray powder diffraction, and their crystalline structure was refined by using the Rietveld method. All samples annealed below 300 °C were amorphous. The non-sulfated samples crystallized around 350 °C, while the sulfated samples crystallized around 600 °C, when they started loosing sulfate ions. In the initial stage of crystallization, both the tetragonal and monoclinic nanophases coexisted, with the tetragonal as the main phase. Annealing the samples at higher temperatures transformed the tetragonal nanophase, stabilized by OH ions, into the monoclinic one.
Synthesis of self-assembled functional molecules in mesoporous materials
Authors: Honma Itaru , Sasabe H. , Zhou H-S. 
Published: April 2011

ABSTRACTSelf-assembled functional molecules in mesoporous materials are synthesized directly either by co-assembly of dye-bound surfactant of ferrocenyl TMA with silicate or Pc (phthalocyanine) molecules doped in the C16TMA micelles with oxides framework such as V2O5, MoO3, WO3and SiO2. The process provides well-organized molecular dopoed mesoporous structure by direct and simple procedure.
Shear Transmission in lamellar Ti-48at.%Al
Authors: Wiezorek J. M. K. , Zhang X. D. , Clark W. A. T. , Fraser H. L. 
Published: April 2011

ABSTRACTThe transmission of shear across the interfaces between lamellae of γ-TiAl and α2-Ti3Al has been studied in the case of a room temperature deformed Ti-48A1 alloy containing a significant proportion of the lamellar microstructure. The mechanisms of shear transmission due to dislocation slip has been studiedusing transmission electron microscopy. Dislocations with Burgers vectors given by b=1/3 <1120>are the only products of slip transmission from the γ-TiAl phase to the α2-Ti3Al phase, and essentially no dislocations with b=1/3 <1126> i.e. c-component dislocations, have been observed. Slip transmission has been associated with impingement of certain cross-lamellar twins, formed by deformation in γ-TiAl, with the α2 lamellae. Dislocation based models for the slip transmission processes are proposed.
Slip of c + a/2 Dislocations in Ti3Al Single Crystals Strained in Tension Along the C-Axis
Authors: Minonishi Y. , Legros M. , Caillard D. 
Published: April 2011

ABSTRACTIn situ TEM straining experiments have been performed on a Ti3Al single crystal, along the c-axis, in order to study the slip of 2c+a dislocations in pyramidal planes. The results show that slip takes place in π1 planes, in contrast with what has been observed after compression tests (slip in π2 planes), and that rows of loops are nucleated in the slip plane. The mechanisms which may control slip in the π1 planes are briefly discussed.
Measurement of Twinning Elements in PST TiAl Single Crystal
Authors: Lu Lei , Pope David P. 
Published: April 2011

ABSTRACTTwinning is the major deformation mode at room temperature in TiAl polysynthetically twinned (PST) crystals (lamellar structure, TiAl is the major phase and Ti3Al is the minor phase). We present here the results of Atomic Force Microscope (AFM) observations of deformation twinning displacements measured on the free surfaces of PST single crystals. AFM is used in this experiment because of its very high resolution for topological measurements and its ability to measure surface displacements from very small twins.Measurements were made on samples with different compression axes and surface orientations. When a twin intersects a free surface, a definite displacement is produced which is easily related to the twinning elements. The majority of the surface offsets observed correspond to those for ordinary twinning, within a very small deviation. Thus it is concluded that these are ordinary twins. The widths of the twinning bands are around 300nm, smaller than the widths of the TiAl lamellae. Slip bands are also observed. They are characterized by a much more irregular geometry than the twinning bands. At some places where twins intersect a domain boundary slip bands are produced in the adjacent domain.
Effect of Prestraining on the Brittle-To-Ductile Transition of NiAl Single Crystals
Authors: Shrivastava S. , Ebrahimi F. 
Published: April 2011

ABSTRACTThe brittle-to-ductile transition (BDT) has been established for NiAl single crystals as evaluated by fracture toughness testing and also the effects of prestraining on the brittle-to-ductile transition temperature (BDTT) have been investigated. Specimens were prestrained to a 10% plastic strain level at 200°C under tension prior to toughness testing. The BDT of the prestrained specimens was compared to that of the as homogenized specimens. The results have revealed the occurrence of two competing effects upon prestraining: (1) an increase in dislocation sources causing a difficulty in micro-crack initiation and resulting in an increase in toughness at low temperatures, and (2) an increase in the flow stress resulting in an increase in BDT temperature. The crack initiation and propagation mechanisms were also analyzed and have been discussed.
Chemistry, Bonding and Fracture of Grain Boundaries in Ni3Si
Authors: Subramanian Shanthi , Muller David A. , Silcox John , Sass Stephen. L. 
Published: April 2011

ABSTRACTTo obtain insight into the effect of dopants on the bonding and cohesive energy of gram boundaries in Ll2 intermetallic compounds, the chemistry and electronic structure at grain boundaries in B-free and B-doped Ni-23 at % Si alloys were examined, with electron energy loss spectroscopy (EELS) providing information on the former and energy dispersive X-ray spectroscopy (EDX) on the latter. Ni-enrichment was seen at large angle boundaries, both in the absence and presence of B. EELS of the Ni L3 edge showed that the bonding at Ni-rich grain boundaries was similar in both undoped and doped alloys. Comparison of the Ni L3 edge recorded at the grain boundary and in the bulk suggests that reduced hybridization and weaker bonding occurs at Ni-rich grain boundaries in both doped and undoped alloys. These changes in bonding are interpreted in terms of changes in the cohesive energy of the boundaries.
Mechanical Behavior of Reactively Hot-Pressed Aluminide Matrix Composites
Authors: Inoue M. , Suganuma K. , Niihara K. 
Published: April 2011

ABSTRACTFeAl and Ni3Al matrix composites containing various fine particles were fabricated successfully by reactive hot-pressing. The strength and the fracture toughness of these composites at ambient temperatures were evaluated. The addition of β-SiC particles was effective for strengthening of the Fe-40at%Al matrix, however, an extreme decrease of fracture toughness occurred due to the suppression of stress relaxation effect by plastic deformation at a crack tip. The fracture toughness of the reactively hot pressed Fe-40at%Al and its composites was also affected by the environmental embrittlement effect. TiB2 and ZrB2 particles in the Fe-40at%Al matrix composites were clarified to play a role in the reduction of the environmental effect. For the Ni-25at%Al matrix, higher flexural strength was achieved by the addition of TiB2, TiC and TiN particles. TiB2 particles reacted with the matrix during hot-pressing. The Ni-25at%Al/TiB2 composite had a fracture strength of 1.5 GPa in spite of large grain size of the matrix. TiC and TiN were the best choices as effective reinforcing matrials for the Ni3Al matrix among the chemical compatible ones.
Alloying Effect of Vanadium Upon Structure and Strength of σ-Phase Titanium Trialuminide
Authors: Takahashi Tohru , Iwami Kenji , Hasegawa TAdashi 
Published: April 2011

ABSTRACTThe alloying effect of vanadium upon σ-phase titanium trialuminide has been investigated using materials whose compositions were of the type Al3(Ti,V). Six types of ternary aluminum-titanium-vanadium alloys, ranging from Al3Ti to Al3V at 5 atomic % intervals, have been prepared by arc melting. All the materials showed the D022 tetragonal structure, suggesting vanadium atoms substitute titanium atoms. The 0.2% proof stress increased with increasing vanadium content up to about 10 atomic %, and then decreased toward that of Al3V both at room temperature and at elevated temperatures. Such behavior can be interpreted as substitutional solid solution strengthening.
Investigation of Diblock Copolymer thin film Morphology for Nanolithography
Authors: Park Miri , Harrison Christopher , Chaikin Paul M. , Register Richard A. , Adamson Douglas , Yao Nan 
Published: April 2011

ABSTRACTThe microphase separated morphology of diblock copolymers can be used to generate well-ordered nanometer scale patterns over a large area. To achieve this goal, it is important to understand and control the behavior of diblock copolymer thin films on substrates, which can differ from the bulk behavior. We have investigated the morphologies and ordering in thin polystyrene-polybutadiene (PS-PB) diblock copolymer films on bare silicon and silicon nitride substrates, and also on polymethylmethacrylate (PMMA) coated substrates. The PS-PB copolymers are synthesized to form, in bulk, PB cylinders or spheres in a PS matrix. In thin films (10–60 nm thick), prepared by spin-coating, we observe that the morphology and ordering of the microdomains are affected by strong wetting constraints and a reduced chain mobility on the substrate. The thinnest self-assembled layer of the copolymer films shows no in-plane microphase separation on both types of substrates. The PS blocks wet the PMMA substrates whereas the PB blocks wet the bare substrates as well as the air interface. Hence, different film thicknesses are necessary on the two types of substrates to obtain a uniform film of the first self-assembled cylindrical or spherical microdomain layer. The first layer of the cylindrical copolymer can vary from cylindrical to spherical morphology with a few nanometer decrease in film thickness. In the case of spherical PS-PB diblock copolymer films, we observe that the ordering of the microdomains is improved in the films on the PMMA substrates, compared to those on the bare substrates. We also demonstrate a successful transfer of the microdomain patterns to silicon nitride substrates by a reactive ion etching technique.
Measuring Polymer Microstructure using Spatially-Resolved Eels in the Stem
Authors: Siangchaew K. , Arayasantiparb D. , Libera M. 
Published: April 2011

ABSTRACTImage contrast for the examination of multiphase polymers in the transmission electron microscope (TEM) usually requires differential staining by a heavy element (Os, Ru, U). Staining methods have provided a wealth of microstructural information in polymers, but there are situations, particularly where high resolution is needed, where staining is undesirable or impossible. This research has collected microstructural information from multiphase polymers without heavy-element stains using spatially-resolved electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). The technique is known as spectrum imaging. The principal problems facing spectrum imaging in polymer applications are: (1) the identification of spectral fingerprints distinguishing different polymer phases; and (2) the extraction of meaningful microstructural data from large data sets where the signal is weak due to instrumentation and materials constraints. This paper describes applications of spectrum imaging to PE/PS and HDPE/Nylon 6 blends. The aim is to identify adequate spectral features and establish data acquisition and extraction procedures for applications to general, unstained, multiphase polymers.
Ultra-High Resolution Small-Angle Neutron Scattering Investigations of Liquid-Liquid Phase Separation in Linear Low-Density Polyethylene
Authors: Agamalian M. M. , Alamo R. G. , Londono J. D. , Mandelkern L. , Spooner S. , Stehling F. C. , Wignall G. D. 
Published: April 2011

ABSTRACTPrevious small-angle neutron scattering (SANS) studies [1] of heterogeneous ethylene-hexene linear low-density polyethylene (LLDPE) copolymers have confirmed the existence of a dispersed minority phase (volume fraction φ ∼ 10−2) consisting of highly branched, amorphous material. However, these experiments were conducted via a pinhole SANS spectrometer with an upper resolution limit ∼ 103 Å, whereas microscopy indicates that the dimensions of the disperse phase extend to the μm-range. We have therefore complemented these investigations via a Bonse-Hart ultra-small angle neutron scattering (USANS) instrument which increases the instrumental resolution in reciprocal space by a factor - 100, and thus particle size up to 30 μm can be resolved. The sensitivity of the USANS camera has recently been increased by two orders of magnitude by using the modified channel cut crystals [2], and the performance is therefore comparable to the best x-ray Bonse-Hart cameras. Xylene extraction removes the highly branched molecules and hence the volume fraction of the disperse phase is higher (φ ∼ 0.3) in the extracted material.