bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Model for the Poly-Silicon thin Film Transistor for Use with Spice
Authors: M.J. Izzard , P. Migliorato , W.I. Milne 
Published: March 2011

AbstractA set of analytical equations that accurately model the large-signal current-voltage and charge-storage characteristics of the poly-silicon thin film transistor (TFT) have been developed. The model is based on theories of conduction in materials with a bulkdistribution of gap states[l]. The equations are suitable for incorporation into a circuit simulator capable of transient-analysis of circuits, such as SPICE.
The Formation of Silicon Clusters in Plasma-Enhanced Chemically Vapour Deposited Si:O:H:F Alloys
Authors: Dias A. G. , Figueiredo J. 
Published: March 2011

AbstractThe structural and optoelectronic properties of a new plasma-enhanced chemically vapour deposited Si:O:H:F alloy are reported taking into account respectively the results from X-ray diffraction, Raman and infrared absorption spectroscopy analysis and from dark and photo conductivity and optical absorption measurements. Films produced with a F2/SiH4 gas ratio (r) lower or equal than 0.4 are amorphous semiconducting Si:O:H:F alloys, whereas films deposited with r≤0.5 exhibit a multiphase structure consisting of silicon clusters embedded in an amorphous insulating fluorine doped silicon oxide tissue. The formation of silicon clusters is the result of a segregation process of the fluorine and oxygen atoms in the amorphous Si:O:H:F matrix.
Evidence for Strongly Enhanced Paramagnetic Defect Creation in Low Temperature Pecvd SiO2 Films
Authors: Devine R. A. B. , Pfeffer R. L. 
Published: March 2011

AbstractAmorphous SiO2 films have been deposited by plasma enhanced chemical vapor deposition (N2O:SiH4 flow rate ratio of 40:1) then 60Co gamma irradiated. We observe paramagnetic defects similar to oxygen vacancy centers which are created at least 100 times more efficiently in as-deposited oxide than in the same oxide annealed for 1 hr in Ar at 950°C. Positive fixed oxide charge creation in samples irradiated in the unbiased mode has a fractional yield of 0.018 defects per electron-hole pair. No enhancement of the positive fixed oxide charge creation is observed when comparing as-deposited and annealed films suggesting that the paramagnetic and electric defects do not have the same physical origin. Comments are made about the potential hazards of using such deposited oxide near a semiconductor surface where surface inversion may occur.
The Electrical and Optical Properties of Amorphous Silicon Alloys by Plasma-Enhanced CVD Method
Authors: Lin G. H. , Kapur M. , Bockris J. O'M. 
Published: March 2011

AbstractHigh and low bandgap amorphous silicon thin film alloys (a-Si:Al, a-Si:Se, a-Si:S, and a-Si:Ga) were prepared by plasma-enhanced chemical vapor deposition. It was found that Al and Ga amorphous silicon alloys are low bandgap materials whereas a:SiS and a:SiSe are high bandgap semiconductors. The optical band gap of these systems could be changed from 1.0 eV to 2.0 eV, depending on the alloying element and its concentration in the film. The dark to light conductivity ratio was measured. The elemental content and distribution was analyzed by the SIMS and EPMA techniques. The results show that some of the amorphous silicon alloys studied are promising materials for multi-bandgap photovoltaic devices.
Ftir Investigations of Plasma Modified Polymer Surfaces and Their Interfaces with Plasma Deposited Tungsten
Authors: Leu Jihperng , Dalvie Manoj , Jensen Klavs F. 
Published: March 2011

AbstractSurface modifications of thin polyimide films (100–2000 A˚) in downstream microwave CF4/NF3/Ar plasmas and radio-frequency (RF) CF4 plasmas have been studied in situ by Fourier transform infrared (FTIR) reflection-absorption spectroscopy. The downstream microwave plasma treatment produced significant surface fluorination in terms of polyfluorinated alkyl and aryl compounds as well as acyl and benzoyl fluorides. The depth of fluorination was approximately 500 Å. Similar changes in polymer surface functionalities were observed for RF plasma surface modifications, but the depth of fluorination was reduced to 30Å because of ion-bombardment. The interface between the tungsten film and polyimide surfaces has been characterized by ex situ FTIR reflection-absorption technique through the silicon side of Si/polymer/W structures. The observed spectral changes relative to polyimide-gold interfaces were interpreted in terms of interactions of tungsten with functionalities of the polyimde backbone. Tungsten deposited by both sputtering and plasma enhanced chemical vapor deposition (PECVD) showed significant chemical interactions, strongest for PECVD tungsten.
Laser-Induced Fluorescence of Silicon and Silicon Monoxide in a Glow Discharge
Authors: Hynes Anthony J. 
Published: March 2011

AbstractSi atoms and SiO radicals have been monitored in DC ulow discharges via laser-induced fluorescence on the Si 4s 3P0-3P2−3P and SiO A1 π-x1Σ+ (0−0), (1−0) and (1−1) transitions. Production of Si 4s 3P0 in the 193 and 251 nm multiphoton dissociation of silanes has been observed and the implications for Si atom diagnostics discussed.
Spatial Generation Profiles of Active Radicals in Plasma-Enhanced CVD Of a-Si:H
Authors: Mataras D. , Cavadias S. , Rapakoulias D. 
Published: March 2011

AbstractSpatially resolved Laser Induced Fluorescence and Optical Emission Spectroscopy were applied in an rf silane discharge, for the simultaneous detection of both ground and excited states of SiH radicals. Axial intensity profiles of these radicals were recorded under various conditions. The experimental observations indicate that the two radicals have different generation paths. LIF profiles are considered to represent the generation profile of all the ground state radicals and they were used as such in kinetic calculations.
Nitrogen Incorporation in a-Si,N:H Alloy Films Produced by Remote PECVD
Authors: Parsons G. N. , Lucovsky G. 
Published: March 2011

AbstractWe have produced a-Si,N:H alloy films using remote PECVD at a substrate temperature of 200°C with Si/N ratios between 0 (a-Si:H) and 3/4 (Si3N4). Films were prepared using nitrogen or ammonia source-gases, introduced downstream from a helium rf plasma. Nitrogen and hydrogen bonding environments were investigated using infrared absorbance. For films produced from N2, [N] and [H] concentrations were determined by SIMS. A random bonding model is used for a quantitative analysis of Si-H and Si-N bonding distributions, and to estimate the N/Si ratio in films produced from NH3. A comparison of N2 and NH3 source gases for nitrogen incorporation is also presented.
The Morphology of Symietric Diblock Copolymers as Revealed by Neutron Reflectivity
Authors: Satija S. K. , Majkrzak C. F. , Anastasiadis S. H. , Russell T. P. 
Published: March 2011

ABSTRACTThe specular reflectivity of neutrons has been used to characterize quantitatively the microphase separated morphology of symmetric, diblock copolymers of polystyrene, PS and polymethylmethacrylate, PMMA, as a function of the total molecular weight of the copolymer where either block is perdeuterated. It is shown that the hyperbolic tangent function, as opposed to a linear or cosine squared function, most closely describes the concentration gradient at the interface between the lamellar copolymer microdomains. The effective width of the interface is found to be independent of the molecular weight of the copolymer blocks and has a value of 50 ± 3Å. This interface is also found to be identical to that of PS and PMMA, homopolymers. However, using measured values of the Flory-Huggins interaction parameter for PS and PMMA current theoretical treatments cannot describe the observed widths of the interface.
Structure of ErBa2Cu3Ox in the Composition Range 6.1 < x < 7.0
Authors: Pörschke E. , Meuffels P. , Rupp B. 
Published: March 2011

ABSTRACTThe structure of a series of homogeneous ErBa2Cu3Ox powder samples (6.1 < x < 7.0) has been determined by elastic neutron scattering using the Rietveld method of profile refinement. All samples were prepared in the same way using a defined absorption-desorption method.By removing oxygen the c axis expands, whilst the Cu2–Cu2 and the Ba–Ba distances contract. Accordingly, the most significant changes in atomic distances occur between the Cu2–O2,3 planes and the Cul–O4–Cul chains. With decreasing oxygen content the distance between the Cu–O planes and the Cu–O–Cu chains increases and the oxygen (0, 0, z) apex atom O1 moves closer to the Cu–O–Cu chains withdrawing from the Cu–O planes. The O1–plane and O1–chain distances are monotonic functions of the oxygen content, but the x dependence of these bonding lengths seems to be much stronger below x < 6.5. The change of the interatomic distances can be correlated to the suppression of superconductivity which clearly occurs within the orthorhombic phase.
Short-Range Order in α-Brass
Authors: Reinhard L. , Schoenfeld B. , Kostorz G. , Buehrer W. 
Published: March 2011

ABSTRACTQuenched equilibrium states of Cu–31.1 at.% Zn and Cu–22.4 at.% Zn single crystals (prepared with the Cu-65 isotope) were investigated by elastic diffuse neutron scattering. The diffuse intensity showed maxima which are attributed to the flat portions of the Fermi surface in the <110> directions. Short–range order parameters and linear displacement parameters were obtained from a fit to the measured data. Pair interaction energies were determined based on the inverse Monte–Carlo method. An ordered low-temperature phase Cu3Zn with the DO23 structure is suggested.
Ordering Mechanism in Ni-Cr Alloys: Theory and Experiment
Authors: Turchi P.E.A. , Pinski F.J. , Howell R. H. , Wachs A.L. , Fluss M.J. , Johnson D.D. , Stocks G.M. , Nicholson D. M. , Schweika W. 
Published: March 2011

ABSTRACTRecently, short range order (SRO) parameters have been extracted from the neutron diffuse scattering intensities on Ni-Cr alloys with 11 to 25 at. pct. chromium. These data were analyzed using inverse-Monte Carlo simulations to extract atomic interactions and the results suggested the existence of a well defined, flat sheet of Fermi surface normal to the [110] direction. In this paper, this suggestion is investigated with a series of calculations which are based on the first-principles Korringa-Kohn-Rostoker-coherent-potential-approximation (KKRCPA). We calculate the electronic structure and the Bloch spectral function at the Fermi energy. We then proceed to calculate the effective cluster interactions using the generalized perturbation method (GPM) and compare them with the above-mentioned experimentally deduced interactions. In addition, we present preliminary results of two-dimensional angular correlation of positron annihilation radiation (2D-ACPAR) measurements, which probe the fermiology of this alloy system. The positron experiments demonstrate the existence of well-defined features in the Fermi surface of Ni89Cr11 but our calculations still have not yet established the origin of SRO in this system.
Phonon Dispersion and Kohn Anomaues in the Alloy Cu0.84Al0.16
Authors: Chou Henry , Shapiro S. M. , Moss S. C. , Mostoller Mark 
Published: March 2011

ABSTRACTWe have made detailed measurements of phonon frequencies along all high-symmetry directions on a large single crystal of Cu0.84Al0.16 at room temperature. Phonon frequencies were ascertained to better than ±0.03 meV. Inter-atomic force constants and vibrational density of states were calculated by performing a Born-von Karman analysis on the complete set of phonon dispersion curves. In contrast to the case of pure Cu, no evident Kohn anomaly (neither in the phonon dispersion itself nor in the derivatives) was observed near the expected wave vector q=2kF. The absence of Kohn anomalies in the present system could be due either to a smeared out Fermi surface or to the possibility that the electron-electron interaction which screens the inter-ionic potential is not the dominant interaction in the system; i.e. the existence of Kohn anomalies in these alloys may depend mainly on the details of the electron-phonon interaction.
Influence of Interstitial Oxygen on the Lattice Parameters of Solution-Treated and Aged Ti-8.6 wt% Al Alloys
Authors: Gray G. T. , Lawson A. C. 
Published: March 2011

ABSTRACTNeutron powder diffraction data have been obtained on Ti-8.6wt.% Al alloys with three different oxygen contents ( 500, 1000, and 2000 ppm) in the solution-treated and aged condition ( containing α2) to investigate possible oxygen and aluminum ordering and lattice parameter variations. The lattice parameters “a” and “c” were found to depend on the oxygen content and heat-treatment condition. Consistent with the literature lattice parameter data on pure Ti, the “a” lattice parameter of the solution-treated Ti-8.6Al material is relatively insensitive to the oxygen content while the “c” parameter increases with increasing oxygen. Following aging to precipitate the ordered α2, the “c” lattice parameter in the Ti-8.6Al alloys still exhibits a positive dependence on oxygen content with aging and a slight “c” increase over the solution-treated condition. The “a” lattice parameter following aging is observed to be lower than the solution-treated value, particularly for the 1000 and 2000ppm alloys. The diffraction data will be discussed in light of parallel electron microscopy results and literature data.
Sans Measurement of Deuterium-Dislocation Correlation in Palladium
Authors: Heuser Brent J. , Summerfield G.C. , King J.S. , Epperson J.E. 
Published: March 2011

ABSTRACTSmall angle neutron scattering (SANS) measurements have been made on deformed polycrystal palladium samples with and without deuterium dissolved in the solution phase (a) at room temperature. Concentrations were held constant during SANS experiments by an equilibrium gas pressure cell. The difference scattering cross section for the same sample with and without deuterium loading has a 1/Q behavior (Q=4Φ/λsinθ/2) at intermediate values of Q. At very low values of Q the dependence is much stronger than 1/Q. The 1/Q behavior is attributed to deuterium trapping close to long dislocation cores forming rod-like scattering structures.
Residual Stress Measurements by Means of Neutron Diffraction
Authors: Prask H. J. , Choi C. S. 
Published: March 2011

ABSTRACTEnergy-dispersive neutron diffraction has been developed at the NIST reactor as a probe of sub- and near-surface residual stresses in technological samples. Application of the technique has been made to a variety of metallurgical specimens which includes the determination of tri-axial stresses as a function of depth in a number of uranium-3/4wt%Ti samples with different thermo-mechanical histories, and in two types of 7075-T6 aluminum “ogives”- of interest to the Army. Preliminary results have been obtained for an induction-hardened steel shaft, a fatigue lifetime test specimen for the SAE.
Neutron Diffraction Measurement of the Stress Field During Fatigue Cycling of a Cracked Test Specimen
Authors: Hutchings M.T. , Hippsley C.A. , Rainey V. 
Published: March 2011

ABSTRACTThe triaxial stress field has been measured along the centre line of a compact tension specimen in the direction of cracking. The specimen had been subjected to ∼60,000 cycles at δK=31 and Kmax = 34 MPa mm½ and was bolted open at maximum stress. The field was remeasured after the stress had been fully relaxed. The results are discussed in terms of expectations from fracture mechanics calculations.
Diffuse Neutron Scattering from Excess Oxygen in UO2.13
Authors: Goff J.P. , Hutchings M.T. , Brown K. , Hayes W. , Godfrin H. 
Published: March 2011

ABSTRACTCoherent diffuse neutron scattering from single crystal UO2.13 has been investigated at temperatures up to 2100K. Above 850K the crystal as a single phase and the excess anions give rise to a characteristic pattern of elastic diffuse scattering. This can be interpreted in terms of uncorrelated simple clusters of defective anions first postulated by Willis. The intensity distribution changes with temperature increase but no quasielastic scattering has yet been resolved. On cooling to 293K a strong hysteresis is exhibited.
Observation of Micellar Formation in the Cavity of Porous Silica Glass
Authors: Bradley K.F. , Chen S-H , Thiyagarajan P. 
Published: March 2011

ABSTRACTThe small angle neutron scattering intensity distribution from the empty pores of the silica glass Vycor can be satisfactorily interpreted using a simplified late stage spinodal decomposition model, due to Cahn', if one allows for a distribution of wave numbers in the material's density function. The result confirms that the porosity of the glass is 28% and gives the mean wave number of the density wave to be k0 = 0.0285 Å-−1 with a dispersion, δk / k0, of about 0.29. Small angle neutron scattering measurements of the anionic surfactant SDS in the Vycor pores indicate that when the surfactant is introduced into the pores at 80 × CMC in bulk solution, the surfactant forms micelles with the same average micelle separation distance as in the bulk solution, but the distribution of micelle separations is much greater in the glass pores.
Characterization of Chemically Modified Pore Surfaces by Small Angle Neutron Scattering
Authors: Glinka C. J. , Sandert L. C. , Wiset S. A. , Berk N. F. 
Published: March 2011

ABSTRACTSmall angle neutron scattering has been used to characterize the structure of linear hydrocarbon chains chemically grafted to the internal pore surfaces of microporous silica particles. The aim of this work has been to relate the structure of the bonded adsorbate layers in these particles to their performance in, for example, reverse-phase liquid chromatography. By filling the pore space in the modified silica with a solution that matches the scattering density of the silica framework, the scattering from the adsorbate layers is enhanced and provides a sensitive probe of the effective thickness, uniformity and degree of solvent penetration in the layers. Results are presented for both monomeric and polymeric phases of alkyl chains ranging from C8 to C30 bonded to silica particles with a mean pore size of 100 nm.
Small Angle Neutron Scattering and Small Angle X-Ray Scattering from Bulk Microporous Silica
Authors: Long G. G. , Krueger S. , Black D. R. , Cline J. P. , Jemian P. R. , Gerhardt R. A. 
Published: March 2011

ABSTRACTThe microstructure of low-density porous silica precursor (unsintered) bodies was studied as a function of starting chemistry. The ratio of colloidal silica sol to potassium silicate is known to have a marked effect on the size distribution of pores in this material, which in turn have a major impact on the resultant physical properties of the sintered product. In the present research, the sizes and the size distributions of particles underlying the pore microstructure was investigated, and it was found that the lower the amount of colloidal silica, the greater the size distribution of particle aggregates.
Small Angle Neutron Scatitering Study of Sol-Gel Glasses
Authors: Wiltzius P. , Dierker S. B. 
Published: March 2011

ABSTRACTWe present small angle neutron scattering data of porous glasses. Analysis of the structure factor shows that the morphology on length scales between 30 A and 800 A depends on fabrication procedures. Fast gelation leads to a clumpy glass, whereas slow gelation produces a random smooth internal interface.
Dynamics of Star-Branched Polymers in Solution
Authors: Huangi J. S. , Fetters L. J. , Richter D. , Farago B. , Ewen B. 
Published: March 2011

ABSTRACTWe have studied star-branched polymers in solution under various labelling and contrast matching conditions by small angle neutron scattering and neutron spin echo spectroscopy. We have investigated the relation between the static and dynamic partial structure factors of the variously labeled star polymers. The system of interest is a set of solutions containing 12-arm star branched polyisoprene of arm-molecular weight of 8000, and two polystyrene 12-arm stars, one fully labelled, the other with one arm labelled. The polyisoprene star polymer arms consisted of diblock copolymers, half-deuterated, and half-protonated. Measurements were performed on a center-deuterated star in a contrasted matching deuterated solvent (shell contrast), and on a reverse labelled star with core contrast. We have also studied a solution with the solvent matched the average star scattering length density and solutions containing identical stars with protonated homopolymers. It is found that in the frame-work of the random phase approximations, the initial relaxation rate of the partial dynamic structure factors can be quantitatively accounted for by a function of the eigenmodes of the mobility matrix weighted by an appropriate combinations of the various partial static structure factors.
Surface Enrichment and Evaporation in a Polymer Mixture of Long and Short Chains
Authors: Composto Russell J. , Stein Richard S. , Felcher Gian P. , Mansour Abdelkader , Karim Alamgir 
Published: March 2011

ABSTRACTNeutron reflectivity has been used to determine the concentration profile at the vacuum-polymer interface for a two polymer blend. To quantify surface enrichment and evaporation due to differences in chain length, we have measured the reflectivity of a mixture of short deuterated and long protonated polystyrene chains (DPS & PS), with a weight fraction of 0.5. When a mixture of DPS and PS chains of molecular weight 720 and 910k respectively were annealed, a small but measurable increase in asymptotic reflectivity occured, coupled with a decrease of film thickness and scattering length density. This is indicative of surface enrichment and evaporation of the light chains (DPS). Ellipsometry studies confirmed that the short chains evaporated and its rate was established as a function of the temperature. Upon increasing the DPS molecular weight to 9600, the enrichment becomes considerably greater whilst the evaporation becomes negligible.
Multiple Small Angle Neutron Scattering Characterization of the Densification of Alumina
Authors: Krueger S. , Long G.C. , Page R.A. 
Published: March 2011

ABSTRACTMultiple small angle neutron scattering (MSANS) was used to follow the evolution of the pore size distribution in α-Al2O3through the intermediate and final stages of sintering. This technique makes it possible to determine microstructure morphology in the 0.08 to 10 μm size regime under conditions where the total scattering cross-section is dominated by elastic incoherent multiple scattering, as is often the case for ceramics. The MSANS results indicate an initial decrease in the effective pore radius from 0.19 μm at 57% of theoretical density (TD) to 0.17 μm at 79% TD. As the sample density further increased, there was a transition region after which the effective pore radius grew rapidly to ≤0.5 μm at 98% TD. Standard Porod analysis on scattering by the same samples also indicates a transition between the intermediate and final stages of processing. Both sets of results support a topological model of sintering in which the interconnected pore network in the intermediate stage of sintering decays in a stable manner. The pores become fewer, while retaining the same diameter, as densification proceeds. In the final stage, isolated pores remain.