bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanofiber Based Er(III) Metal Pyrochlore Oxides: Synthesis and Characterization
Authors: Wang Ruofeng , Bender Edward T. , Aljarrah Mohannad T. , Evans Edward A. , Ramsier Rex D. 
Published: April 2011

AbstractErbium(III) doped TiO2 nanofibers (Er2Ti2O7) have been synthesized by electrospinning mixtures of polymers, metal-containing materials, and erbium acetate. These electrospun nanofibers were subsequently annealed at temperatures of 550, 750, 950, and 1150 oC to remove the organics and leave behind the metal oxides. The crystal structure and optical properties of the nanofiber pyrochlores were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformation IR (FTIR) spectroscopy. Different crystal structures were formed by controlling the annealing conditions. XRD data are compared with near-IR spectra to better understand the effects of annealing temperature on the Er (III) thermally-excited selective optical emission process.
Nanocrystalline Eu3+ Doped M3Al2O6 (M: Ba, Ca and Sr) Red Phosphors Prepared by Sucrose-PVA-Metal Ion Complex Route
Authors: Manavbasi Alp , Zed Palkin , LaCombe Jeffrey C. 
Published: April 2011

AbstractNanocrystalline (<100 nm) red emitting Eu3+- doped M3Al2O6 (M = Ba, Ca and Sr) phosphors were prepared by an aqueous sucrose-PVA-metal ion complex route. The aqueous sucrose-PVA solution includes 20 mol% PVA, and the method is based on the dehydration of a transparent metal ion-sucrose-PVA solution to a highly viscous liquid and then precursor formation by heating at 250°C. The phase formation and the crystallite size measurements were made by x-ray diffraction techniques. Photon correlation analysis revealed that all synthesized phosphor particles range in size from 400 nm to a few microns. The photoluminescence (PL) and PL excitation characteristics have been investigated. All samples have broad CT bands centered at around 269 nm and only the Ca3Al2O6:Eu3+ exhibited the characteristic f-f transitions of Eu3+ ions mainly located at 396 and 465 nm in comparable levels with the CT band. The emission spectrum of Ca3Al2O6:Eu3+ is dominated by the red (5D0 ¡æ 7F2) transition band located at 614 nm, however the Eu3+ doped Sr3Al2O6 and Ba3Al2O6 phosphors have comparable emission intensity in the red (5D0 ¡æ 7F2 ) and orange (5D0 ¡æ 7F1 ) transition bands. The highest intensity of the red emission was obtained when the Ca3Al2O6:Eu3+ phosphor was excited at 396 nm.
Slow Crack Growth Analyses of Oxygen Transport Ceramic Membranes
Authors: Nagabhushana Nagendra , Zhang Jing , Nithyanantham Thangamani , Bandopadhyay Sukumar 
Published: April 2011

AbstractPerovskite-type oxides are promising materials with potential use as dense membranes for oxygen separations. We herein report slow crack growth (SCG) studies of La0.2Sr0.8Fe0.8Cr0.2O3-δ (LSFCO) perovskite membranes as Oxygen Transport Membranes (OTM). Two sample batches of perovskite were tested to investigate the effect of temperature, specific chemical environments, and loading rate on flexure strengths, using four-point bending tests. The first batch was examined at room temperature in air. The second batch was soaked in a N2/air atmosphere at 1000°C for 1 hour prior to application of load. Loading rates varied from 0.00005 mm/s to 0.01 mm/s. Flexural strength data indicate that the examined OTM material showed little susceptibility to SCG at room temperature in air. However, the sample is susceptible to SCG in a N2/air environment at 1000°C. Also, the experiments demonstrate flexural-strength rate dependency, with strength increasing with the loading rate. The observed phenomena are explained by the decomposition and microstructural transitions in the perovskite. The results provide important information about OTM mechanical degradation, which is valuable for future OTM design applications.
Synthesis and Optical Properties of SERS-active Nanocomposite Microspheres
Authors: Farah Abdiaziz , Dai Sheng , Jawabrah Al-Hourani Baker , Bravo-Vasquez Juan P. , Cho Jae-Young , Fenniri Hicham 
Published: April 2011

AbstractAn approach to prepare metal nanoparticle-polymer microbeads with integrated Raman tags using SERS as reliable diagnostic tool is reported. In essence, spectroscopically encoded (4-thioacetyl)styrenes were assembled on well-characterized 50 nm Au NPs and subjected to suspension polymerization conditions using styrene and methacrylic acid as comonomers and divinylbenzene as crosslinker. The resulting metal embedded nanocomposites were characterized by SEM, TEM, DSC, TGA, Raman and SERS to determine their morphology, particle size, composition, thermal stability and their optical and electronic properties.
Deconvolution of Self-encoded Polymer Beads in Random Microarrays for Antigen Biosensing by Raman Spectroscopy
Authors: Bravo-Vasquez Juan P , Alvarez-Puebla Ramon A , Blais David , Zhang Ying , Raez Jose , Pezacki John P , Fenniri Hicham 
Published: April 2011

AbstractRandom bead microarray in which each bead has been functionalized with different biomolecules are of great interest. The process by which one would identify the location of each bead is referred to as decoding. The decoding step has played a challenging role in microarray technologies due to the increase in complexity with the increase in array size. Here we report a novel, fast and reliable method of decoding randomly assembled arrays based on polymer beads with unique spectroscopic signatures. Beads were synthesized by dispersion polymerization of a family of styrene monomers and methacrylic acid to generate a spectroscopically encoded bead library. In addition to identifying the self-encoded beads through their unique spectrum in a tetraplex experiment, Raman spectroscopy was used to monitor antibody-antigen binding events on the barcoded beads. The simplicity, versatility and rapid analysis enabled by this self-encoded bead array platform technology demonstrates its potential in high-throughput biomolecular multiplex screening.
The Effect of Surface States on Secondary Electron (SE) Dopant Contrast from Silicon p-n Junctions
Authors: Chee Augustus K. W. , Rodenburg Conny , Humphreys Colin John 
Published: April 2011

AbstractDetailed computer modelling using finite-element analysis was performed for Si p-n junctions to investigate the effects of surface states and doping concentrations on surface band-bending, surface junction potentials and external patch fields. The density of surface states was determined for our Si specimens with a native oxide layer. Our calculations show that for a typical density of surface states for a Si specimen with a native oxide layer, the effects of external patch fields are negligible and the SE doping contrast is due to the built-in voltage across the p-n junction modified by surface band-bending. There is a good agreement between the experimental doping contrast and the calculated junction potential just below the surface, taking into account surface states, for a wide range of doping concentrations.
Three Dimensional Observation of Flux Pinning Centers in Dy-doped YBa2Cu3O7-x Coated Superconductors by STEM Tomography
Authors: Ortalan Volkan , Herrera Miriam , Morgan David G. , Rupich Martin W. , Browning Nigel D. 
Published: April 2011

AbstractThe spatial distribution of flux pinning centers in YBa2Cu3O7 (YBCO) coated conductors significantly affects the conductive properties. Nanoparticles acting as pinning centers can be intentionally introduced into the structure by chemical doping. In this study, a Dy-doped YBa2Cu3O7-x coated superconductor was investigated and the particle composition was found to be as (YsDy1-s)2Cu2O5 with s ∼0.6. A tomographic tilt series was acquired using a scanning transmission electron microscope (STEM) to determine the 3-D distribution of nanoparticles. In the investigated sample area, 71 particles were located with a particle size distribution ranging between 13 and 135 nm. The distribution uniformity and size of the particles appeared to be dependent on the grain boundary network structure. Large particles were observed to be located on grain boundaries indicating that fast grain boundary diffusion may determine the particle size.
Quantitative STEM and HRTEM Studies on Au Metallic Nano-Catalysts
Authors: Li Long , Menard Laurent D. , Xu Fengting , Nuzzo Ralph G. , Yang Judith C. 
Published: April 2011

AbstractNano-catalysts, Au nano-particles on TiO2 (anatase), were studied by means of quantitative scanning transmission electron microcopy (Q-STEM) and high-resolution transmission electron microcopy (HRTEM). All the Au nano-catalysts were produced from an Au13 precursor, Au13[PPh3]4[S(CH2)11CH3]4, TiO2 supports, with three treatments: (1) thermal heating in the air at 400°C for 2 hours, (2) exposure to ozone (O3) at room temperature, and (3) exposure to atomic oxygen (AO, or O) with a AO dose of 7.3 ×1018 atom/cm2 at room temperature. Both reactive oxygen species O3 and AO produced significantly small sizes of Au particles as compared to those from the heating treatment in the air (2.7 ± 0.6 nm, 324 b 264 atoms). Ozone produced the smallest (1.2 ± 0.5 nm, 40 ± 49 atoms), whereas AO produced smaller (2.1 ± 0.7 nm, 72 ± 98 atoms), with a broad size distribution and a variety of shapes. HRTEM studies on the AO treated Au/TiO2 samples found that there could exist relationship between the particles size and their shapes which also affected by the interaction with TiO2 supports. The support effect of TiO2 to the shapes of Au particles was also studied.
Plasticity Mechanism of Indium Antimony (InSb) in the Brittle Regime: Combined Study with Conventional TEM and LACBED
Authors: Kedjar Bouzid , Thilly Ludovic , Demenet Jean-Luc , Rabier Jacques 
Published: April 2011

AbstractIndium antimony (InSb) has been deformed in compression under gaseous confining pressure (Paterson apparatus) above and below the brittle to ductile transition occurring around 150°C. Thin foils have been prepared from the deformed samples and dislocations were characterized with conventional TEM as well as LACBED. This paper focuses on the room temperature deformation microstructures which appeared to be extremely complex with the observation of very well arranged network of perfect and partial dislocations. In such case, the traditional dislocation extinction conditions were extremely difficult to apply and only the use of the LACBED technique uncovered the nature of the observed dislocations and gave further insight to their interactions, revealing in particular the presence of partial dislocation dipoles. These original observations suggest a change of deformation mechanism at the brittle to ductile transition temperature.
Reduction of Contrast in ADF-STEM Images Due To Amorphous Layer
Authors: Maccagnano-Zacher Sara , Mkhoyan Andre , Silcox John 
Published: April 2011

AbstractA study of high-resolution ADF imaging in uncorrected and aberration-corrected STEMs was carried out by multislice simulation. The presence of amorphous layers at the surface of a crystalline specimen is shown to significantly alter the visibility of the atomic columns in ADF images. After propagating through an amorphous layer a portion of the beam passes without any alteration while scattered electrons introduce a Gaussian background. An amorphous layer at the beam entry surface appears to have slightly more of an effect on the ADF image contrast than that of an amorphous layer at the exit surface, and this difference increases with increasing atomic number. With constant crystal layer thickness, the reduction of contrast as a function of increasing amorphous layer is found to have the same behavior, regardless of the thickness of the initial crystal layer thickness.
The Atomic, Electronic and Defect Structure of the Dynamically Formed Cu2O/Cu Interfaces
Authors: Han Xuetian , Yang Judith C. 
Published: April 2011

AbstractTo gain fundamental insights into metal oxidation, the dynamically formed Cu/Cu2O interface was investigated by cross-sectional TEM (Transmission Electron Microscopy) methods. Copper (001) films were oxidized in oxygen within a UHV chamber to create Cu2O islands that formed epitaxially with respect to the Cu film. The cross-sectional Cu2O/Cu TEM sample was prepared by dual beam (DB) focused ion beam (FIB) instrument and the interface was probed by high-resolution TEM (HREM) and electron energy loss spectrum (EELS). It is found that Cu2O {110} layer distance significantly decreases from the interface area to the bulk Cu2O region, which is about 3∼4 unit cell thickness in Cu2O side; while the {100Cu2O layer distance increases with increasing distance from the interface region. The chemical Cu/Cu2O interface thickness has been measured with EELS analysis, which is about 2nm where the oxidation state of Cu gradually changes from Cu0 to Cu+1. This transition region indicates the area where Cu/Cu2O interface exists and suggests the existence of metastable Cu oxides. The Cu2O island growth mechanism of predominantly anion interfacial diffusion at the initial stage oxidation has been proposed.
Off-Axis Electron Holography of Self-Assembled Co Nanoparticle Rings
Authors: Kasama Takeshi , Dunin-Borkowski Rafal E. , Scheinfein Michael R. , Tripp Steven L. , Liu Jie , Wei Alexander 
Published: April 2011

AbstractWe use off-axis electron holography in the transmission electron microscope (TEM) to study magnetic flux closure (FC) states in self-assembled nanoparticle rings that each contain between five and eleven 25-nm-diameter Co crystals. Electron holograms are acquired at room temperature in zero-field conditions after applying chosen magnetic fields to the samples in situ in the TEM by partially exciting the conventional microscope objective lens. Mean inner potential contributions to the phase shift are determined by turning the samples over, and subsequently subtracted from each recorded phase image to obtain magnetic induction maps. Our results show that most nanoparticle rings form FC remanent magnetic states, and occasionally onion-like states. Although the chiralities (the directions of magnetization) of the FC states are determined by the shapes, sizes and positions of the constituent nanoparticles, reproducible magnetization reversal of each ring can be achieved by using an out-of-plane magnetic field of between 1600 and 2500 Oe.
Synchrotron Characterization of Texture and Stress Evolution in Ag Films
Authors: Vodnick Aaron , Lawrence Michael , Little Bethany , Worden Derek , Baker Shefford 
Published: April 2011

AbstractReal-time in-situ synchrotron x-ray diffraction measurements were performed at the Cornell High Energy Synchrotron Source to characterize both the texture evolution and stresses within the individual texture components of Ag films during recrystallization. As deposited films had a nearly perfect (111) fiber texture. During isothermal anneals, stress and texture were characterized in real-time as the texture evolved into a strong (001) fiber. An Avrami analysis of the evolving texture fractions yielded very different activation energies for films on different barrier layers, suggesting different governing mechanisms were responsible for secondary grain growth. The strains were used to test a common model for texture prediction that assumes the same strain within each texture component. It was found that secondary (001) grains were able to grow primarily strain free. Selection for this strain energy minimizing orientation occurred during the nucleation process during which texture interactions play an important role. By using these real time measurements, we are able to show that driving forces for texture transformations in metal films may not be as simple previously described.
In-Situ Neutron Diffraction Study of the Behavior of AL6XN Stainless Steel Under Biaxial Loading
Authors: Gharghouri Michael , Marin Tito , Rogge Ronald B , Dawson Paul R 
Published: April 2011

AbstractIn–situ neutron diffraction has been used to measure lattice strains parallel to two principal stress directions in biaxially-loaded AL6XN stainless steel. A new fixture was developed for loading thin-walled tubular specimens through combinations of internal pressure and axial loading. Under these conditions, the principal directions (σzz and σθθ in a cylindrical r, θ, z coordinate system) remain constant with respect to the initial crystallographic texture regardless of the level of biaxiality, a distinct advantage for diffraction experiments over the traditional tension/torsion tests for which this condition does not hold. Specimens were first pressurized to the level required to obtain a chosen value of σθθ. The axial load was then increased to reach the yield surface at different σθθ/σzz ratios, ranging from uniaxial to balanced biaxial loading (0, 0.4, 0.7, 1 according to Tresca). The {200}, {220}, {222}, and {311} reflections were measured in the axial and hoop directions as a function of axial load. A sequence of axial loading/unloading episodes was applied for different levels of plastic deformation. Under uniaxial tension, the {200} reflection showed the highest axial strains, followed by the {311}, and {220}/{222} reflections. With increasing internal pressure (biaxiality), the axial lattice strains corresponding to a given axial stress tended to decrease, and the responses of the various reflections tended to merge.
Modeling of Charge Transport in a Hybrid Metal / Organic / Inorganic Device
Authors: Mendez Henry Alberto 
Published: April 2011

AbstractA Metal / Organic / Inorganic semiconductor heterostructure was built and characterized in situ under ultra-high vacuum conditions (UHV). The aim was to investigate the influence of a perylene-derivative organic thin film on the transport electronic properties of Schottky Ag / GaAs diodes. The device was studied using a combination of photoemission spectroscopy (PES) and electrical measurements. The obtained results were discussed using the analytical expressions of a trapped charge limited current (TCLC) model.
Specialty High Performance Coatings for Optical Fiber Applications via Perfluorocyclobutyl (PFCB) Aryl Ether Polymers
Authors: Budy Stephen M. , Iacono Scott T. , Hawkins Wade , Foy Paul , Ballato John , Smith Dennis W. 
Published: April 2011

AbstractThere is a growing need for optical fiber coatings that can sustain higher temperatures than present materials permit. To date, polyimides are used predominantly but they generally are difficult to process and usually require multiple depositions to achieve the desired film thickness. Perfluorocyclobutyl (PFCB) aryl ether polymers have demonstrated much success as processable and amorphous fluoropolymers,[1] with particular emphasis on high performance optical applications.[2] This work discusses recent efforts into perfluorocyclobutyl aryl ether polymer-based optical fiber coatings.[3] A series of silica-based optical fibers were drawn with differing PFCB polymer coatings compositions and molecular weights on a Heathway draw tower. Results include a more than doubled usage temperature of coating (decomposition temperatures (Td) in nitrogen and air were above 450 °C) without affecting fiber mechanical properties and comparable isothermal stability to conventional coatings, except with a >150 °C higher temperature. Preliminary results of the first successful coating of optical fibers by PFCB polymers will be presented herein, as well as future endeavors.
Poly and Nano-crystalline High Electron Mobility Thin Film Transistors on Plastic Substrates for Large Area Applications
Authors: Paydavosi Sara , Tamaddon Amir-Hossein , Mohajerzadeh Shams , Robertson Michael D 
Published: April 2011

AbstractThin-film transistors (TFT) of poly and nano crystalline silicon have been made at temperature as low as 170°C on flexible PET (polyethylene terephthalate) substrates.The crystallization of the silicon film has been achieved using external mechanical stress assisted by a plasma hydrogenation technique. The formation of TFT is possible by means of a lateral crystallization of amorphous silicon under the channel region. High mobility TFTs with an electron mobility of 25cm2/Vs and an on/off ratio of 2000 have been obtained. Scanning electron microscopy, X-ray diffraction analysis and optical microscopy have been used to examine the crystallinity of the layer. In addition we report the deposition of high quality low-temperature silicon-oxide layers on PET substrates using an RF-plasma enhanced chemical vapor deposition unit with direct introduction of oxygen gas into the chamber and its reaction with Silane. Infrared spectroscopy was used to examine the quality of the oxide layer.
Rigid-Rod Sensitizers bound to Semiconductor Nanoparticles
Authors: Taratula Olena , Galoppini Elena 
Published: April 2011

AbstractA series of “rigid-rod” dyes with an organic chromophore (pyrene or coumarin) attached through an oligophenylenethynylene (OPE) rigid bridge, linear or branched, to an anchoring isopthalic acid unit (Ipa) were synthesized and studied for solar cells (DSSCs) applications. The new dyes were attached to metal oxide (MOn = TiO2, ZrO2 and ZnO) nanoparticles films via the two COOH binding groups on the Ipa unit to investigate their binding and photophysical properties at the semiconductor surface. FTIR-ATR spectra show that all dyes did bind to the metal oxide films through carboxylate bonds. Fluorescence emission on insulating ZrO2 films was employed to study aggregation of the organic rigid-rods. Studies of the pyrene rigid-rods in solar cells showed near quantitative conversation of absorbed photons into electricity.
Energy Band Engineering for Improved Vertical Transport in Quantum Structured III-V p-i-n Solar Cells
Authors: Alemu Andenet , Freundlich Alex 
Published: April 2011

AbstractThe use of InGaAsN and GaBiAsN quantum structures in the intrinsic region of conventional III-V p-i-n solar cells, lattice matched to GaAs, presents several advantages for photovoltaic (PV) application. First they allow for very shallow to zero valence band offsets thus permitting the free movement of holes. Second, a wide range of band-gap values are made possible due to the large band gap decrease upon the introduction of minute amounts of N and Bi. Using band structure calculations that include the strain effects, conduction and valence band anti-crossing models describing the large band gap bowing and the transfer matrix method, we present the theoretical investigation of optimum design conditions for enhanced vertical transport. The direct quantum mechanical resonant tunneling of electrons out of the quantum structures and into the continuum of the conduction band of the host semiconductor material can be facilitated provided that an adequate choice of material parameters is made. The high electron transmission probability together with the free movement of quasi-3 D holes is predicted to result in enhanced PV device performance. Furthermore, the increase in electron effective mass due to the incorporation of N translates in enhanced absorptive properties, ideal for PV application.
Factors Affecting Exchange Bias in Polycrystalline Metallic Thin Films
Authors: Fernandez-Outon Luis Eugenio , Vallejo-Fernandez Gonzalo , O'Grady Kevin 
Published: April 2011

AbstractWe describe the factors which control the measured value of exchange bias (HEX) in bilayers consisting of sputtered metallic thin films of an antiferromagnet (AF) in contact with a ferromagnetic (F) layer. Experimental measurements show that the value of HEX is determined by the grain volume distribution which limits the exchange bias via small grains which are thermally unstable, and large grains which cannot be set when the system is field annealed to set the AF at temperatures below TN. All the results are interpreted in terms of a granular model where the energy barrier to reversal within the AF is grain volume dependent. We show how this affects setting in metallic AFs at T<TN. We have also found that exchange bias is moderated by disordered spins at the F/AF interface. These spins can be ordered at low temperatures and by field annealing. Ordering of interfacial spins leads to an increase in HEX of up to 30%.