bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual Porosity and Relaxation in Polymeric Latex Films Studied by CO2 Diffusion
Authors: Balik C. M. , Said M. A. 
Published: March 2011

AbstractSolubility and diffusivity measurements of CO2 have been used to measure amount of residual porosity (excess volume) and the kinetics of its removal in latex films cast from a terpolymer of butyl acrylate, vinyl acetate, and vinyl chloride. The pore volume fraction is very small, ranging from 0.5–0.05% for latex films aged from 62 hrs to 480 hrs, respectively. Long-term aging kinetics can be followed by sorbing to equilibrium at constant CO2 pressure and temperature, and following the weight loss as the sample relaxes and CO2 diffuses out. Relaxation data obtained at temperatures ranging from 25–50°C could be superimposed on a single master curve using the WLF equation. The implications these results have concerning the morphology of the residual porosity in latex films are discussed.
Free Volume Relaxation in Polycarbonate as a Function of Physical Aging
Authors: Heater Kenneth J. , Jones Phillip L. 
Published: March 2011

AbstractRoom temperature free volume relaxation of polycarbonate as a function of aging time at 393K has been evaluated via positron annihilation lifetime spectroscopy. Free volume response data were normalized and modeled using an expression of the Williams-Watts form. The process of physical aging is discussed in terms of the trends associated with the resultant characteristic relaxation time constants and distribution of relaxation times.
Effects of Complexation on the Glass Transition Temperature of Polymers
Authors: Roberts Michael F. , Jenekhe Samson A. 
Published: March 2011

AbstractThe effects of Lewis acid complexation on the glass transition temperature (Tg) of several polymers with strong intermolecular interactions was investigated. The decrease in the Tg due to GaCl3 complexation of aliphatic and aromatic polyamides was 40–600° C and 148° C, respectively, and was shown to originate from scission of the intermolecular hydrogen bonds. The reduction in the Tg due to GaCl3 complexation of rigid–chain polymers was greater that 325° C and can be explained by the mitigation of the otherwise strong van der Waals forces in the pristine polymers. Thus, the dominant effect of intermolecular interactions on the Tg of several polymers has been probed by Lewis acid complexation.
Effects of Aging on Polymerization Kinetics
Authors: Bowman Christopher N. , Peppas Nikolaos A. 
Published: March 2011

AbstractA theoretical model was developed to describe the physical aging during photopolymerizations and crosslinking reactions of diacrylates and dimethacrylates. The model incorporates the strong coupling between the volume relaxation and the kinetics observed in these reactions. Model predictions are presented for the reaction kinetics, volume relaxation, radical concentration and maximum conversion as a function of light intensity and relaxation time of the polymer.
Structural Changes in Glassy Polycarbonate Due to Cyclic Loading
Authors: Liu Liang Bao , Yee Albert F. , Lewis John C. , Li Xiaowei , Gidley David W. 
Published: March 2011

AbstractGlassy polycarbonate was subjected to cyclic stresses and the changes in its structure were studied by DSC, positronium annihilation lifetime spectroscopy (PALS), and small and medium angle X-ray scattering. Upon increased exposure to cyclic loading, the enthalpy overshoot near Tg increased in a manner similar to increasing physical aging. However, the “hole” size as revealed by PALS increased, unlike physical aging. SAXS reveals an increase in the short range order and the amplitude of density fluctuation. These results can be explained in a consistent manner. We conclude that mechanical loading does cause changes in the glassy structure.
Influence of Thermal History on the Glass Transition of Poly(Phenylene Sulfide)
Authors: Huo Pengtao , Cebe Peggy 
Published: March 2011

AbstractPPS is increasingly interesting as a high performance polymer material. Recently, Cheng, et al. [1] reported observation of rigid amorphous phase (RAP) in the amorphous phase of semicrystalline PPS using differential scanning calorimetry. Using the heat of fusion from DSC to obtain the degree of crystallinity of the semicrystalline samples, a simple rule of mixtures was applied to calculate the change in heat capacity step. The heat capacity decreased much more than could be accounted for using the measured crystallinity. Thus, these authors assumed the existence of a rigid amorphous phase which did not become liquid-like at Tg. The ratio of heat capacity step at Tg of semicrystalline PPS to that of the purely amorphous polymer was used to find the fraction of amorphous chains that do become liquid-like at Tg. The amount of RAP was then obtained by assuming a three phase model.
The Volumetric Response of Polymeric Glasses to Complex Thermomechanical Histories: a Critical Evaluation of the Kahr Model
Authors: Greener J. , O'reilly J. M. , Ng K. C. 
Published: March 2011

AbstractThe KAHR model was used to predict the transient volumetric response of poly(vinyl acetate) (PVAc) and polystyrene (PS) glasses in various experiments involving controlled variations of temperature and pressure in the vicinity of the glass transition. The experiments considered include contraction following a quench from equilibrium, expansion after a temperature “jump,” and pressure-induced densification. The model parameters of PVAc were obtained by fitting experimental data via a 4-parameter Levenberg-Marquardt optimization. The optimized parameters were then used to predict the response of the material in three different experiments. The response of PS in a pressure densification experiment was also analyzed and compared with existing data. Generally, the predicted response of PVAc in the various temperature jump experiments is in excellent agreement with observation. The prediction of the response of PS in the pressure densification experiment is also in line with observation although the data for this case is limited and the results are still inconclusive.
Integrated MSM-FET Photoreceiver Fabricated on Mocvd Grown Hg1-xCdxTe
Authors: Leech Patrick W. , Gwynn Peter J. , Pain Geoffrey N. , Petkovic Novica R. , Thompson James , Jamieson David N. 
Published: March 2011

ABSTRACTWe report on progress in the monolithic integration of a metal-semiconductor-metal (MSM) detector and transimpedence amplifier and of a photoconductive detector (PCD) with a metal-semiconductor field effect transistor (MESFET) in Hg1-xCdxTe. The layers of CdTe/n-type Hg1-xCdxTe were grown by MOCVD on semi-insulating GaAs substrates (2° misoriented 100). Fabrication of the devices was by an FET planar process; with a standard lift-off used to form Schottky metallization on both the interdigitated electrodes of the MSM detector (2μm width, 2μm spacing) and the gate of the MESFETs (5μm length, 100μm width). The MSM photodetectors exhibited breakdown voltages in the range 60 to 80V, a dark current of 1 Ona at 5V bias, and responsivities of > 1.0 A/W measured at 40V using CW 1.3um illumination. The integrated devices have been characterised by electrical and micro RBS techniques; the results were found to be strongly dependent on the stoichiometric x ratio of the Hg1-xCdxTe. This initial work demonstrates the suitability of Hg1-xCdxTe/GaAs structures in the fabrication of integrated optoelectronic circuits.
InAsSb Photodiodes Grown on InAs, GaAs and Si Substrates by Molecular Beam Epitaxy
Authors: Dobbelaere W. , Boeck J. De , Raedt W. De , Vanhellemont J. , Zou G. , Hove M. Van , Brijs B. , Mertens R. , Borghs G. 
Published: March 2011

ABSTRACTInAs and InAs0.85Sb0.15p-“i”-n structures were grown on InAs, GaAs and Si substrates by Molecular Beam Epitaxy. The structural quality of the layers is discussed using Transmission Electron Microscopy and Rutherford Back Scattering. The influence of the material quality on the 77 K current-voltage measurements is explained. The spectral response of the devices was measured demonstrating peak responsivities of 2.1 A/W at 3.5μm wavelength for InAs0.85Sb0.15 detectors with a 4.3 μm cut-off wavelength.
Low Pressure Mocvd Growth of InSb
Authors: Cunningham B.T. , Schneider R.P. , Biefeld R.M. 
Published: March 2011

ABSTRACTLow pressure (200 Torr) metalorganic chemical vapor deposition (MOCVD) of InSb has been examined through variation of the Column III (TMIn) and Column V (TMSb or TESb) precursor partial pressures. The use of lower growth pressure significantly enhanced the range of allowable Column III and Column V partial pressures in which specular morphology InSb could be obtained without the formation of In droplets or Sb crystals. In addition, a 70% improvement in the average hole mobility was obtained, compared to InSb grown in the same reactor at atmospheric pressure. SIMS analysis revealed that Si at the substrate/epitaxial layer interface is an important impurity that may contribute to degradation of the mobility. Substitution of TESb for TMSb did not result in any improvement in the purity of the InSb.
Undoped GaSb Growth by MOCVD
Authors: Su Yan Kuin , Juang Fuh Shyang 
Published: March 2011

ABSTRACTUndoped GaSb epilayers have been grown on (100) GaSb and S.I. GaAs substrates. The effects of growth temperatures and TMSb/TEGa mole fraction ratios on the epitaxial properties of surface morphology, growth rate, hole concentration and mobility (300K and 77K) have been studied. The lowest concentration 1.8x101 6 cm- 3 (77K) and the highest mdobility 1447 cm2/V.s (77K) can be obtained under V/III ratio of 6.64 at 550°C. Photoluminescence intensity was found to be a function of the V/III ratios. When V/III ratios increased or decreased beyond 6-8, the BE peaks disappeared and PL spectra became roughened.To reduce the effects of large lattice-mismatch in highly strained GaSb/GaAs system (7% mismatch) on the electrical properties, a 10-period In0.3Ga0.7As/GaAs (60A/40A) strain layer superlattice (SLS) has been grown on GaAs substrates as a dislocation filter before the GaSb epitaxial growth. From the comparison of 77K Hall mobility of GaSb/GaAs as a function of growth temperature with that of GaSb/SLS/GaAs, it was clearly observed that the epilayers grown on SLS structures have higher mobility than those grown directly on GaAs substrates. From the TEM analysis, we observed that all dislocations propagated up to the GaSb epilayer surface in the GaSb/GaAs system but some of the dislocations bending before reaching the epilayer surface in the GaSb/SLS/GaAs system.
Properties of Pt/Ti Contacts to III-V Materials
Authors: Katz A. , Nakahara S. , Chu S. N. G. , Weir B. E. , Abemathy C. R. , Hobson W. S. , Pearton S. J. , Savin W. 
Published: March 2011

ABSTRACTPt/Ti contact to variety of binary III-V and related ternary semiconductor materials were established. These contacts were formed by electron beam evaporation and subsequent rapid thermal processing in order to sinter the metal-semiconductor systems. The contacts to p-type InAs, GaAs, In0.53Ga0.43As, In0.52Al0.4As and Ga0.7Al0.3As were ohmic, as a result of heating at temperatures of 450°C or higher. The Pt/Ti contacts to InP and GaP displayed Schottky behavior as-deposited and preserved the rectifying nature through heat treatments, regardless of the processing conditions. The electrical properties and the microstructure evolution in these 7 systems is discussed in this paper.
Traps in ZnS/Anodic Sulfide Film on Mercury Cadmium Telluride
Authors: Hikida S. , Kajihara N. , Miyamoto Y. 
Published: March 2011

ABSTRACTWe studied the influence of visible light on the ZnS/anodic sulfide/HgCdTe interface.We measured flatband voltage of metal-insulator-semiconductor diodes with semitransparent electrodes at 77 K. In the dark (i.e., without visible light). The flatband voltage of an metal-insulator-semiconductor diode is 0 V. We scanned visible light from 400 to 800 nm and measured the flatband voltage using the photocapacitance measurement. After an initial positive shift, the flatband voltage moved negative by as the wavelength shortened. We studied the relationship between the flatband voltage shift and photon energy using Fowler plots. Results suggest one electron trap level 1.5 eV above the valence band and two hole trap levels 1.7 and 2.3 eV below the conduction band.ZnS/anodic sulfide films on mercury cadmium telluride, studied using photoluminescence spectroscopy, showed broad photoluminescence peaks at 1.5, 1.7, and 2.3 eV, and the edge emission of the anodic sulfide.These results suggest that photoionization of the electron trap and two hole traps in the ZnS/anodic sulfide film causes the flatband shift.
Local Phonon Heating and Recombination-Enhanced Defect Annealing
Authors: Abakumov V.N. , Pakhomov A.A. , Yassievich I.N. 
Published: March 2011

ABSTRACTA detailed study of local phonon heating due to multiphonon recombination process is presented. Nonequilibrium distribution of defects by vibration energy is calculated taking into account the dependence of capture and emission rates on the defect energy. It is shown that multiphonon generation and recombination of electron-hole pairs stimulate diffusion of defects in energy space. The results are used to calculate the rate of recombination-enhanced defect annealing.
NDT Applications of the 3D Radon Transform Algorithm for Cone Beam Reconstruction
Authors: Sire P. , Grangeat P. , Lemasson P. , Mélennec P. , Rizo P. 
Published: March 2011

ABSTRACTThe paper describes our 3D X-ray CT algorithm “RADON” using attenuation measurements acquired with a bidimensional detector. Our inversion diagram uses the first derivative of the Radon transform synthesis then its inversion. The potentiality of that new method, particularly for the large aperture, prompted us to develop an optimized software offering convenience and high performances on a modem scientific computer. After a brief recall of the basic principle of X-ray imaging processing, we will introduce the theoretical developments resulting in the present inversion diagram. A general algorithm structure will be proposed afterwards. As a conclusion we will present the performances and the results obtained with ceramic rotors examination.
Preprocessing of Ion Microtomography Data for Improved Reconstruction Quality
Authors: Weirup David L. , Pontau Arthur E. , Antolak Arlyn J. , Morse Dan H. , Bench G. , Cholewa M. , Saint A. , Legge G.J.F. 
Published: March 2011

ABSTRACTIn Ion Microtomography (IMT), material densities are determined from the energy lost by ions as they pass through a specimen. For fine-scale measurements with micron-size beams, mechanical stability and precision of motion can impact the quality of the reconstruction. We describe several preprocessing procedures used to minimize imperfect specimen manipulation, including adjustment of the center of mass motion in sinograms and correction for vertical translations. In addition, the amount of noise in the reconstruction is reduced by utilizing median (as opposed to mean) ion energy loss values for density determinations. Furthermore, particular portions of the sampled image can be enhanced with minimal degradation of spatial resolution by a judicial choice of spatial filter in the reconstruction algorithm. The benefits and limitations of these preprocessing techniques are discussed.
NMR Imaging of Solids Using Imaging Instrumentation Designed for Liquids
Authors: Cory D. G. , Gravina S. J. 
Published: March 2011

ABSTRACTThe possibilities of acquiring NMR images of solids with conventional imaging apparatuses are explored. To this end a multiple-pulse line-narrowing sequence is introduced which averages both homonuclear dipolar couplings and time independent linear lz, interactions such as chemical shifts and susceplibility shifts. For imaging the multiple-pulse cycle is accompanied by an oscillating magnetic field gradient which phase encodes the spatial location o each spin. The period of the gradient oscillation is matched to the period of effective field toggling such that the multiple-pulse cycle does not average to zero the gradient induced spin evolution. A small radio frequency coil of 3.0 mm i.d. is used since then only modest radio frequency (RF) power is sufficient to generate a strong RF field, and the RF homogeneity is quite good over the sample volume. The resolution of the image is not spatially uniform, but near the center the resolution is better than 100 μm and the resolution at the edges of the image is degraded by only a factor of 3 to 5. Images of solids with acceptable resolution and sensitivity can be collected by this method- with minimal setup time and difficulties.
Comparative Imaging of Liquids in Rocks by NMR and Differential X Ray CT
Authors: Jeandey C. , Casagrande J.M. , Briguet A. , Ntoutoume T. , Guillot G. 
Published: March 2011

ABSTRACTWe have applied NMR Imaging and X_Ray Computerized Tomography to the study of the structural properties of rocks. Samples from different porous rocks; sandstones, granites, limestones have been successively examined by both techniques. NMR images have been obtained on water saturated samples. The spatial distribution of liquid indicates the effective porosity. By constrast, X_Ray images display the mineral content of rocks. Standard tomographs do not have the required resolution to see pores smaller than 100 μm. We used water as a constrast agent to localize porosities by “differential” CT. Comparative results are shown.
The Study of Materials Using Wavelet Image Processing Techniques
Authors: Beltrán-Del-Rŕo L. , Gónez A. , José-Yacamán M. 
Published: March 2011

ABSTRACTIn this work the wavelet transform is used to process high- and medium resolution electron micrographs from small particles and their substrates. It is concluded that the edge sensitivity of the technique and its contrast enhancement capabilities are most useful in the processing of electron micrographs.
Neutron Tomography: A Survey and Some Recent Applications
Authors: Rodes E. A. , Morman J. A. , Mcclellan G. C. 
Published: March 2011

ABSTRACTA survey is given of recent developments in selected areas of neutron tomography, within the context of several applications Argonne is involved in, including high penetration of reactor-fuel bundles in thick containers (involving TREAT and NRAD facilities), dual-energy hydrogen imaging (performed at IPNS), dynamic coarse-resolution emission tomography of reactor fuel under test (a proposed modification to the TREAT hodoscope), and an associated-particle system that uses neutron flight-time to electronically collimate transmitted neutrons and to tomographically image nuclides identified by reaction gamma-rays.
NMR Imaging and the Electric Quadrupole Interaction in Solid Materials
Authors: Suits B. H. 
Published: March 2011

ABSTRACTNuclei with a spin, 1 > 1/2, possess a nuclear quadrupole moment which can couple to the electric field gradients in a material. They can be static, leading to NMR frequency shifts, or dynamic, which can influence relaxation times. In either case, an NMR image can be made which is sensitized to changes in the electric quadrupole interaction to provide a sensitive measure of the macroscopic spatial dependence of the microscopic changes in the material. Several examples are presented. Special considerations need to be given in the case when the strength of the Zeeman interaction between the nucleus and the magnetic field and/or the rf field is small compared to the electric quadrupole interaction.
Schottky Barriers on Magnetron Sputtered a-Si:H: Depletion width Effects on Photocarrier Collection vs Bandgap and Light Soaking
Authors: Doyle James R. , Maley N. , Abelson John R. 
Published: March 2011

ABSTRACTWe present a study of depletion width effects on the photocarrier collection efficiency in reactive magnetron sputtered a-Si:H films. Results are presented for as-deposited and light soaked 1.75 eV optical gap samples, and an as-deposited 1.60 eV gap film. The depletion width behavior with reverse bias is inferred from capacitance measurements. Comparison with photocurrent collection versus reverse bias voltage suggests that space charge effects can have an important role in the interpretation of collection efficiency on Schottky barriers.
Degradation Study of single a-Si:H Alloy Solar Cells
Authors: Pawlikiewicz Adam H. , Banerjee A. , Guha S. 
Published: March 2011

ABSTRACTThe paper presents the experimental data of single a-Si:H cells degraded under high intensity illumination and compares them to the numerically calculated J-V characteristics of degraded a-Si:H solar cells. The cells were deposited at two different substrate temperatures. The current voltage characteristics were calculated using our simulation program which allows for accurate determination of cell response under monochromatic or global AM1.5 spectrum.We have simulated the light-induced metastable defects (Staebler-Wronski degradation) by increasing the density of localized states. In order to test the validity of this approach we compared the calculated fill factors under AM1.5, blue and red illumination with the measured fill factors for the same light.From the experimental data we observed mat at near room temperature (∼35°C) both cells reach saturation in degradation of fill factors under high intensity illumination. The saturation level corresponded to the minimum density of localized states (gmin) of 1.2×1017 cm-3eV-1 and is independent of the light intensity used in experiment.
The Dynamic Response of Htdrogenated Amorphous Silicon Imaging Pixels
Authors: Yorkston J. , Antonuk L. E. , Morton E. J. , Boudry J. , Huang V. , Kim C. W. , Longo M. J. , Street R. A. 
Published: March 2011

ABSTRACTThe dynamic response of pixels from an a-Si:H imaging array are investigated and a model is developed to explain their observed behavior. Such arrays are under development for radiotherapy and diagnostic x-ray applications.
Correlation of Structure and Structural Changes with Photovoltaic Quality of a-Si:D,H and a-Ge:D,H Films
Authors: Norberg R. E. , Fedders P. A. , Bodart J. , Corey R. , Kim Y. W. , Paul W. , Turner W. 
Published: March 2011

ABSTRACTDeuteron magnetic resonance (DMR) resolves structures such as tightly bound D, weakly bound D, molecular HD and D2 in microvoids and trapped on nanovoid internal surfaces in plasma-deposited a-Si:D,H and a-Ge:D,H. The relative populations of these structures correlate with photovoltaic quality as characterized by photo response function ημτ in a series of deuterated a-Ge and a-Si films. It is found that photo-illumination produces DMR-detected changes in these populations. The changes, which are reversible upon a 150°C dark anneal, include a quadrupolar doublet from strained-bond configurations and a shift from metastable electronic species. The spin-lattice relaxation of most of the components follows an error-function behavior characteristic of magnetization transport under extreme inhomogeneity.
Correlation Between Structural and Photo Electrical Properties of a-Si1−xGex:H Alloy Films - New Interpretation Concerning the Preferential Attachment of Hydrogen
Authors: Schroeder B. , Leidner M. , Oechsner H. 
Published: March 2011

ABSTRACTa—Si1−xGex:H alloy films with 0 > × > 1 have been prepared by reactive co— sputtering (rf—magnetron) from separate targets. The preparation conditions which have been optimized for each composition x must be changed from a—Si:H—like (0 > × > 0.4) to a—Ge:H—like (× < 0.7) to obtain the best photoelectrical quality of the alloy material. The preferential attachment of hydrogen was quantitatively investigated by detailed ir—spectrometric studies. Its monotonic change with x is attributed to fundamental preferential attachment of hydrogen to silicon superimposed by a further preferential attachment to the respective minority alloy partner. The preferential attachment of hydrogen essentially influences the microstructure of the film and thus the material properties.