bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microvoids in Polycrystalline Cvd Diamond
Authors: Mcnamara Karen M. 
Published: April 2011

AbstractSmall angle light scattering has been used to quantitatively study microvoids in polycrystalline CVD diamond. Guinier's approximation was used to calculate the average radius of gyration of these defects for diamond films made by both DC arc-jet and microwave CVD assuming a spherical defect geometry. Values of the radius of gyration varied between approximately 1 and 5 μm and were found to correlate with the thickness, relative transmission and thermal conductivity measured for the films. Some inconsistencies were observed between microwave and DC arc-jet materials which may be related to fundamental differences in the growth processes. This represents the first quantitative analysis of such defects in polycrystalline films and holds great promise for improving our understanding of the diamond CVD processing and properties.
Photoemitters Based on Glass - ITO Structures
Authors: Olesik J. 
Published: April 2011

AbstractThe sample was a silicon glass with conducting films (ITO) evaporated by reactive ion sputtering on its both sides. The internal electric field was created by applying a negative polarizing voltage Upol, to field electrode. The investigations were performed in the vacuum of the order 10−6 Pa. As a result of applying Upol and illumination, photoelectrons are released and enter electron multiplier. The electrons create voltage pulses in the multiplier which are recorded in the multichannel pulse amplitude analyzer. The amplitude spectra were measured for unilluminated samples and illuminated by a quartz lamp.Energy analysis of emitted electrons was performed by the retarding field method. Measurements of electrons energy in field induced emission showed that about 80% o electrons have energy up to 10 eV but some electrons of higher energy are also detected. The described effects can be modeled with support of the electron effects occurring during the intrinsic discharges in gases. Theoretical molecular dynamics simulations have shown that SnO4 tetrahedral interacting with SiO4 clusters of the glass substrate play central role in the observed nonlinear photoinduced changes.
Energy behavior with magnetic field of negatively charged magnetoexcitons in quantum wells and heterojunctions
Authors: Munteanu F. M. , Kim Y. , Perry C. H. , Rickel D. G. , Simmons J. A. , Reno J. L. 
Published: April 2011

AbstractWe present the results of the magneto-photoluminescence measurements performed on modulation doped GaAs/AlGaAs heterostructures in high magnetic fields (up to 60T) and low temperatures (0.37−1.5K). With increasing magnetic field we observe the formation of the triplet and singlet states of negatively charged magneto-excitons (X−) in addition to the neutral exciton (X0). Their behavior with field strongly depends on the sample geometry. In the case of a modulation doped quantum well (QW) with a well-width of 200A, the and states cross at a magnetic field of about 40T, whereas for a modulation-doped single heterojunction (SHJ) these states show no crossing over the whole range of available fields.
STM-Light Emission From Metal Deposited Semiconductor Surfaces
Authors: Yamamoto N. , Kagami S. , Minoda H. 
Published: April 2011

AbstractLight detection system combined with a UHV-scanning tunneling microscope (STM) was applied to the study of silver films deposited on Si(111) surfaces. Photon maps clearly show single atom height steps and terraces on an Ag(111) surface with high spatial resolution of nanometer scale. Chemical reaction on the Ag surface with residual gas was clearly revealed in the photon map. In the photon map of the thin Ag film of 2˜3 ML in thick, no contrast appears between the terraces, and a characteristic bright contrast appears at the single atom height steps. The local plasmon model does not readily explain those contrasts.
Optical properties of Si nanowires on a Si {111} surface
Authors: Ozaki N. , Ohno Y. , Takeda S. 
Published: April 2011

AbstractWe have investigated optical properties of straight silicon nanowires by means of in-situ cathodoluminescence spectroscopy in a transmission electron microscope. The nanowires, grown on a Si{111} surface via vapor-liquid-solid growth mechanism, have no structural defects such as kink, and the diameter and growth direction are controlled by varying the growth conditions. We have found that the nanowires emit intense light. These lines have not been observed in other kinds of Si nanostructures such as porous Si.
Synchrotron x-ray Study of Elastic Phase Strains in the Bulk of an Externally Loaded Cu/Mo Composite
Authors: Wanner A. , Dunand D.C. 
Published: April 2011

ABSTRACTHigh-energy, high-flux x-rays from a third-generation synchrotron source were used to measure average elastic strains in the bulk of 1.5 mm thick composites consisting of a copper matrix reinforced with 7.5 vol.% molybdenum particles. From the evolution of lattice strains in both phases during uniaxial tensile deformation, the internal load transfer between phases and reinforcement damage were characterized during elastic and plastic deformation of the composite. The graininess of the diffraction rings, which is related to the Bragg peak broadening, was quantified as a function of applied stress and related to plastic deformation in the matrix.
In Situ XAFS of the LixNi0.8Co0.2O2 Cathode for Lithium-Ion Batteries
Authors: Kropf A. J. , Johnson C. S. 
Published: April 2011

ABSTRACTThe layered LiNi0.8AsCo0.2O2 system is being considered as a new cathode material for the lithium-ion battery. Compared with LiCoO2, the standard cathode formulation, it possesses improved electrochemical performance at a projected lower cost. In situ x-ray absorption fine-structure spectroscopy (XAFS) measurements were conducted on a cell cycled at a moderate rate and normal Li-ion operating voltages (3.0-4.1 V). The XAFS data collected at the Ni and Co edges approximately every 30 min. revealed details about the response of the cathode to Li insertion and extraction. These measurements on the LixNi0.8AsCo0.2O2 cathode (0.29<×<0.78) demonstrated the excellent reversibility of the cathode's short-range structure. However, the Co and Ni atoms behaved differently in response to Li insertion. This study corroborates previous work that explains the XAFS of the Ni atoms in terms of a Ni3+ Jahn-Teller ion. An analysis of the metal-metal distances suggests, contrary to a qualitative analysis of the x-ray absorption near-edge structure (XANES), that the Co3+ is oxidized to the maximum extent possible (within the Li content range of this experiment) at x = 0.47 ± 0.04, and further oxidation occurs at the Ni site.
Experimental Investigations of the Interaction of SO2 with MgO
Authors: Freitag Andrea , Rodriguez J. A. , Larese J. Z. 
Published: April 2011

ABSTRACTHigh resolution adsorption isotherms, temperature programmed desorption (TPD), x-ray diffraction (XRD) and x-ray absorption near edge spectroscopy (XANES) methods were used to investigate the interaction of SO2 with high quality MgO powders. The results of these investigations indicate that when SO2 is deposited on MgO in monolayer quantities at temperatures near 100K both SO3 and SO4 species form that are not removed by simply pumping on the pre-dosed samples at room temperature. TPD and XANES studies indicate that heating of pre-dosed MgO samples to temperatures above 350 °C is required for full removal of the SO3/SO4 species. XANES measurements made as a function of film thickness indicate for coverages near monolayer completion that the SO4 species form first.
Structural Characterization Using Synchrotron Radiation of Oxide Films and Multilayers Grown by MOCVD
Authors: Dubourdieu C. , Lindner J. , Audier M. , Rosina M. , Weiss F. , Sénateur J.P. , Hodeau J.L. , Dooryhee E. , Bérar J.F. 
Published: April 2011

ABSTRACTSynchrotron radiation at the European Synchrotron Radiation Facility has been used to characterize oxide thin films and multilayers grown by metal organic chemical vapor deposition (MOCVD). Reflectometry measurements were performed in the low angle region to get information on the quality of film/substrate and film/film interfaces of the heterostructures. The experimental data were compared to simulated spectra. High angle diffraction experiments were performed on superlattices of (BaTiO3/SrTiO3)15 and (La2/3Sr1/3Mn03/SrTiO3)15. The multilayers are oriented with the [001] direction perpendicular to the substrate plane. The 001 diffraction peaks were recorded up to the 008 one. The satellite peaks observed for both types of multilayers indicate the good coherence over the whole stacking. For the (BaTiO3/SrTiO3)15 systems, the diffraction peaks were particularly well resolved even for the highest order (008 peak), showing excellent epitaxial quality with abrupt interfaces for periods up to 16 nm.
High Spatial Resolution Strain Measurements Within Bulk Materials by Slit-Imaging
Authors: Lienert U. , Martins R. , Grigull S. , Pinkerton M. , Poulsen H.F. , Kvick Å. 
Published: April 2011

ABSTRACTHigh energy synchrotron radiation is employed for residual strain measurements from local gauge volumes within the bulk of polycrystalline materials. The longitudinal spatial resolution is defined by placing a narrow imaging slit behind the sample and recording the intensity distribution on a position sensitive detector. It is shown that the sample to slit distance can be increased without sacrificing longitudinal resolution by applying a reconstruction technique. Hence, space is provided for large samples and sample environments. The reconstruction technique is described and validated by measuring the residual strain profile of a shot-peened Al sample. A longitudinal gauge length of 95 üm is achieved at 52 keV with a sample to slit distance of 10 cm.
X-ray phase contrast imaging study of activated carbon/carbon composite
Authors: Kobayashi Kenji , Izumi Koichi , Kimura Hidekazu , Kimura Shigeru , Ohira Tomoaki , Saito Takashi , Kibi Yukari , Ibuki Takashi , Takai Kengo , Tsusaka Yoshiyiki , Kagoshima Yasushi , Matsui Junji 
Published: April 2011

ABSTRACTWe have obtained the x-ray phase contrast images of the activated carbon/carbon (AC/C) composite used as electrodes in an electric double-layer capacitor (EDLC). To improve the spatial resolution, the beam size of x-ray transmitted from a sample were expanded by using asymmetric Bragg diffraction (asymmetric factor b) of analyzer crystal. Since the analyzer crystals were placed in (+, -) arrangements in both vertical and horizontal directions, the total magnification factor was 1/b2 for each direction. By using the 511 asymmetric Bragg diffraction of Si (100) analyzer with an asymmetric factor of 0.207, we could obtain the magnification factor of about 23.3. We applied this optical system to the AC/C composite. The phase contrast image corresponding to the carbon particles with the diameter of about 10 μm could be detected with the spatial resolution of 5 μm. Furthermore, we also obtained realtime images of bubble formation and movement during the overcharging of an EDLC with the time resolution of 30 frames number per second.
Growth Twins in YbxY1−xAl3(BO3)4 and NdxGd1−xAl(BO3)4 Crystals Observed by White-Beam Synchrotron Radiation Topography
Authors: Hu X.B. , Wang J.Y. , Guo M. , Zhao S.R. , Gong B. , Wei J.Q. , Liu Y.G. 
Published: April 2011

ABSTRACTGrowth twins in Ybx Y1−xAl3(BO3)4 (YbYAB) and NdxGd1−xAl3(BO3)4 (NGAB) crystals were observed by white-beam synchrotron radiation topography combined with chemical etch. It was found that growth twins in YbYAB crystals are of inversion types in which two twinned pairs have the central inversion relationship. This kind of twinning was visible in x-ray topography not by ‘domain contrast’ but by ‘boundary contrast’ stemming from the kinematical x-ray diffraction at the boundary. Growth twins in NGAB crystals are of 1800 rotation types in which the twofold symmetric operation axis is parallel to the [0001] axis. This kind of twinning often shows black-and-white contrast in x-ray topography which originates from the different structure factors between twinned pairs. In addition. the formation mechanisms of growth twins are discussed.
The Structure of Actinide Ions Exchanged into Native and Modified Zeolites and Clays
Authors: Wasserman Stephen R. , Soderholm L. , Giaquinta Daniel M. 
Published: April 2011

ABSTRACTx-ray absorption spectroscopy (XAS) has been used to investigate the structure and valence of thorium (Th4+) and uranyl () cations exchanged into two classes of microporous aluminosilicate minerals: zeolites and smectite clays. XAS is also employed to examine the fate of the exchanged cations after modification of the mineral surface using self-assembled organic films and/or exposure to hydrothermal conditions. These treatments serve as models for the forces that ultimately determine the chemical fate of the actinide cations in the environment. The speciation of the cations depends on the pore size of the aluminosilicate, which is fixed for the zeolites and variable for the smectites.
EXAFS and Raman Studies of PTMGn:MCl2 and PTMG/PEGn:MCl2 Complexes (M = Co, Zn)
Authors: Furtado C.A. , Porto A.O. , Silva G.G. , Silva R.A. , Alves M.C. Martins , Schilling P.J. , Tittsworth R. 
Published: April 2011

ABSTRACTExtended x-ray absorption fine structure (EXAFS) and Raman spectroscopy measurements have been performed in a series of liquid polymer electrolytes prepared using poly(tetramethylene glycol) (PTMG), and copolymer poly(tetramethylene glycol/poly(ethylene glycol) (PTMG/PEG), as matrices, and ZnCl2or COCl2 as dopants in the concentration range of n = 30 to 90, where n is the molar ratio of Oxigen/Metal cation. EXAFS results have shown the presence of Co-O and Co-Cl coordination shells for PTMG/CoCl2 and PTMG/PEG/CoCl2 systems. Zn-based systems have shown only Zn-Cl bonds in all the concentration range studied. The presence of ZnCl2 and COCl2 species was confirmed by Raman measurements, by the presence of bands characteristic of CI-Zn-Cl and Co-Cl stretching modes.
Synchrotron-Based Studies of Transition Metal Incorporation into Silica-Based Sol-Gel Materials
Authors: Mountjoy G. , Pickup D.M. , Holland M.A. , Wallidge G.W. , Newport R.J. , Smith M.E 
Published: April 2011

ABSTRACTPrevious structural studies on titania- and zirconia-silica xerogels have shown the occurrence of homogeneous mixing at low metal content, and phase separation at high metal content. The use of additional, complementary, synchrotron-based methods can contribute to a fuller structural description of these materials. We present new x-ray absorption near edge structure (XANES) and SAXS results for (ZrO2)x(SiO2)1-x, xerogels and compare them with previous results for (TiO2)x(SiO2)1-x xerogels. Significant differences between (TiO2)x(SiO2)1. and (ZrO2)X(SiO2)1-x xerogels are observed in the affects of heat treatment on the coordination of homogeneously mixed metal atoms, and in the development of phase separated metal oxide regions.
Non-Destructive Dielectric Assessment of Water Permeation in Composite Structures
Authors: Boinard P. , Boinard E. , Pethrick R.A. , Banks W.M. , Crane R.L. 
Published: April 2011

ABSTRACTOver the last ten years, the application of high frequency dielectric spectroscopy techniques for the assessment of composite structures has been investigated. Novel approaches to assess non-destructively the evolution during ageing of adhesively bonded carbon fibre reinforced plastic (CFRP) structures and bulk glass fibre reinforced plastic (GRP) structures are presented in this paper and the results are critically assessed.The applicability and limitations of dielectric measurements, in both frequency and time domain, to the monitoring of water ingress at 30°C and 60°C are examined. The correlation between gravimetric and high frequency dielectric spectroscopy data demonstrates the suitability of the techniques regarding the assessment of water uptake in composites structures and illustrates its potential as a non-destructive evaluation (NDE) technique. The dielectric time domain response (TDR) study of adhesively bonded structures indicates a new way to assess such structures. The approach for frequency domain analysis of bulk GRP using a coaxial probe technique indicates the potential portability of the technique for in-situ measurements.
Nondestructive Damage Evaluation of Electro-Mechanical Components Using a Hybrid, Computational and Experimental Approach
Authors: Furlong C. , Pryputniewicz R. J. 
Published: April 2011

ABSTRACTWith the electronic industry being one of the most dynamic, in terms of new technologies, electronic packages have to be designed and optimized for new and ever more demanding applications in relatively short periods of time. This, in turn, indicates a need for effective quantitative testing methodologies. In this paper, a novel hybridized use of nondestructive, noninvasive, remote, full field of view, quantitative opto-electronic holography techniques with computational modeling is presented. The hybridization is illustrated with a representative application, which shows that the combined use of opto-electronic holography techniques and computational modeling provides an effective engineering tool for nondestructive study of electro-mechanical components.
Non-Destructive Evaluation of Mechanical Properties of Magnetic Materials
Authors: Kankolenski Kevin P. , Hua Susan Z. , Yang David X. , Hicho G. E. , Swartzendruber L. J. , Zang Z. , Chopra Harsh Deep 
Published: April 2011

ABSTRACTA magnetic-based non-destructive evaluation (NDE) method, which employs Barkhausen effect and measurement of the hysteresis loops, is used to correlate the magnetic and mechanical properties of ultra low carbon (ULC) steel. In particular, the NDE method was used to detect small deviations from linearity that occur in the stress-strain curve well below the 0.2% offset strain, and which generally defines the yield point in materials. Results show that three parameters: jumpsum and jumpsum rate (derived from the Barkhausen spectrum), and the relative permeability (derived from the B-H loops) varies sensitively with small permanent strains, and can be related to the plastic deformation in ULC steels. Investigation of micromagnetic structure revealed that plastic deformation leaves a residual stress state in the samples; the associated magneto-elastic energy makes the favorable easy axis of magnetization in a given grain to be the one that lies closest to the tensile axis. The consequence of this realignment of domains is that wall motion becomes intergranular in nature (as opposed to intragranular in unstrained samples). As a result, the more complex grain boundaries instead of dislocations, become the dominant pinning sites for domain walls. These observations provide a microscopic interpretation of the observed changes in the measured magnetic properties.
Non-Destructive Evaluation of 304 Stainless Steels Using a Scanning Hall-Sensor Microscope: Visualization of Strain-Induced Austenite-Phase Breakdown
Authors: Oota A. , Miyake K. , Sugiyama D. , Aoki H. 
Published: April 2011

ABSTRACTUsing a scanning Hall-sensor microscope with an active area 50pμm × 50μm, we succeeded in visualizing a breakdown of paramagnetic austenite-phase in 304 stainless steels induced by a plastic strain at room temperature, resulting from a transformation to ferromagnetic martensite-phase. Magnetic images of spontaneous magnetic fields on a surface of strained sample show the degree and the place (and/or the extent) of phase breakdown. Furthermore, the images nearly agree with the calculated results for the principal shear stress rather than the principal stress under plastic deformation, indicative of the driving force of this breakdown. The study should open a way for non-destructive evaluation of 304 stainless steels.
Quantitative Measurement of Local Carrier Concentration of Semiconductor From Displacement Current-Voltage Curve Using a Scanning Vibrating Tip
Authors: Majima Yutaka , Oyama Yutaka , Iwamoto Mitsumasa 
Published: April 2011

ABSTRACTA new scanning probe method for evaluating the local carrier concentration of semiconductors is presented. The distance between a semiconductor surface and a vibrating tip is changed sinusoidally, and is adjusted to as small as a few nm across which tunneling current IT flows between the semiconductor surface and the vibrating tip. Displacement current ID due to the change in electric flux from the semiconductor surface to the vibrating tip flows periodically in accordance with the vibration of the tip. IT also flows when the distance becomes minimum. Both IT and ID flow simultaneously when a d.c. tip voltage V is applied, and these two currents are separated by using a two-phase lock-in amplifier. ID-V curve is analyzed by taking into account two-dimensional electric flux profile under the tip. In the tip voltage range within which majority carriers are accumulated, ID-V curve is extrapolated by a straight line. On the contrary, the slope of the curve decreases as the tip voltage is reduced from the voltage range of the accumulation, indicating that the majority carriers are depleted at the center of the Si surface. The theoretical ID-V curves are in good agreement with the measurement in the tip voltage region where the majority carriers are both accumulated and depleted. The local carrier concentration is able to be determined by makingthe theoretical ID-V curve fit the experimental results without contacting the semiconductor surface.
Monitoring Silicon Quality From Diffusion Furnaces Using In-Line Measurements
Authors: Stoker Matt , Catmull Kelvin , Horner Greg , Letherer Brian 
Published: April 2011

ABSTRACTCarrier lifetimes provide an excellent indication of the concentration of impurities and defects in semiconducting materials. This paper describes a non-contact technique for measuring generation and recombination lifetimes. This technique, which is incorporated into the KLATencor Quantox system, provides a highly sensitive method for monitoring the formation of defects or incorporation of impurities in silicon wafers during processing. Several applications of these measurements are investigated, such as monitoring the effects of various thermal cycles on the formation of a high-lifetime denuded zone near the wafer surface and monitoring diffusion furnace contamination after a quartz change.
Optimization of x-ray Techniques for Nondestructive Characterization of Single Crystal Turbine Blades
Authors: Winter J.M. , Lipetzky K.G. , Green R.E. 
Published: April 2011

ABSTRACTThis paper describes nondestructive x-ray characterization techniques which detect macroscopic and microscopic defects, determine the overall crystallographic perfection, and detect any unwanted secondary crystals both on the external surface as well as in the interior of single crystal blades. The method of Asymmetric Crystal Topography for diffraction imaging the surfaces of single crystal turbine blades and the method of White Beam Transmission Topography for diffraction imaging through the thickness of single crystal turbine blades are both discussed and illustrated with representive diffraction images (topographs). It is clear that the images gained from these methods have a capability for providing information about the details of crystalline perfection (or lack thereof) in nickel-based alloy single crystal turbine blades. Such information can provide considerable leverage for the crystal grower to help in adjusting processing variables to enhance quality of a critical product. And the same methods of topography can conceiveably provide tools for evaluating the finished product in a way which has not been available to date.