bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton Irradiation Induced Grain Boundary Segregation in Austenitic Stainless Steels
Authors: Damcott D.L. , Was G.S. , Bruemmer S.M. 
Published: April 2011

AbstractRadiation induced segregation (RIS) has been implicated as a mechanism for irradiationassisted stress corrosion cracking (IASCC) in reactor core components. Proton irradiation has been shown to be useful in creating grain boundary chemistries similar to those found in neutron and charged particle irradiated materials for accelerated testing of IASCC susceptibility. This work quantifies grain boundary RIS as a function of proton irradiation dose (0.1-3.0 dpa), temperature (200°−600°C), and alloy composition (20Cr-9Ni, 24Cr-19Ni, and xCr-24Ni, x=16, 20,24). Auger electron spectroscopy revealed Cr depletion and Ni enrichment under all irradiation conditions. As a function of dose, the degree of segregation increased rapidly to near saturation prior to 1 dpa, with a boundary composition of 12.1 at.% Cr and 36.0 at.% Ni at 1 dpa. Segregation peaked at approximately 500°C with 13.0 at.% Cr and 38.6 at.% Ni at the grain boundary at 0.5 dpa; very little segregation was observed at or below 300°C or at 600°C. The trends in segregation as a function of dose agreed well with the Perks' model predictions with the exception of the measurement at 600°C, which showed the sharp decrease in segregation predicted for a higher temperature (700°C-800°C). For alloys containing constant bulk Cr but varying Ni, the Perks' model agreed well with the observed segregation trend; however, for alloys containing constant bulk Ni and varying Cr, agreement was achieved only through the use of composition dependent diffusion parameters.
MÖssbauer Study of Zircaloy After Neutron Irradiation at Power Reactor Temperatures
Authors: Sawicki Jerzy A. 
Published: April 2011

Abstract57Fe-Mössbauer spectroscopy was used to examine a specimen of Zircaloy-4 from a pressure tube extracted from a high-flux fuel channel of a CANDU* reactor. During 25 years of service the alloy was exposed to a fast-neutron fluence of 5.6×1021 n/cm2. The obtained spectra of unirradiated and neutron-irradiated specimens differ considerably. This is attributed to the radiation-induced dissolution and crystalline-to-amorphous transformation of Zr(Cr,Fe)2 precipitates, accompanied by reprecipitation and partial recrystallization of metastable Zr2Fe particles in the zirconium matrix. The correspondence between Mtssbauer and electron microscopy observations, as well as the similarity between neutron-irradiated and ion-implanted specimens, is discussed.
A Thermal Spike Model of the Amorphization of Insulators by High-Energy Heavy-Ion Irradiation
Authors: Szenes G. 
Published: April 2011

AbstractA model based on the assumption of a Gaussian temperature distribution in the thermal spike well accounts for the basic features of latent track formation. In good agreement with the observations it predicts a logarithmic variation of the track size for 2.7≥Se/Set≥1 and a linear variation for Se/Set≥2.7, where Se is the electronic stopping power and Set is a threshold value. The model also provides a quantitative relation between Set and the thermal properties of the target. A weak temperature dependence of track formation is predicted in agreement with the experiments.
Amorphization of Graphite Under ion or Electron Irradiation
Authors: Abe Hiroaki , Naramoto Hiroshi , Kinoshita Chiken 
Published: April 2011

AbstractA transmission electron microscope interfaced with ion accelerators (TEM-Accelerator Facility) in JAERI-Takasaki has been used to get insights into the irradiation-induced amorphization of highlyoriented pyrolytic graphite. Amorphization is induced through lattice disorder under irradiation with electrons or ions at room temperature. The displacement threshold energy is determined as 27 eV and 28 eV from the electron-energy dependence of the amorphization fluence at room temperature and 373 K, respectively. The amorphization fluences in dpa are almost identical for irradiation with various kinds of ions within the experimental error. It indicates the thermal spikes do not have an important role for the amorphization over the energy density between 10-4to 10-2eV/atom.
An Examination of the Factors Which Determine the Thermal Spike Lifetime of a Displacement Cascade
Authors: Tappin D.K. , Robertson I.M. , Kirk M.A. 
Published: April 2011

AbstractThe thermal spike phase of a displacement cascade is thought to be of fundamental importance to a number of issues in radiation effects. For example, the formation of stable vacancy clusters and the efficiency of ion mixing are thought to be directly controlled by the duration of the liquid-like state during the thermal spike. A number of factors have been proposed to be of significance to the lifetime of the thermal spike. For example, materials which have a high melting temperature, or which exhibit strong electron-phonon coupling, which provides an efficient method of energy transport to the surrounding material, are expected to have short lifetimes. We have examined these factors in detail and demonstrated that, in both elemental metals and alloys, electron-phonon coupling provides the most consistent explanation for variations in the thermal spike lifetime and, hence, the efficiency of ion mixing and the number of stable vacancy defect clusters formed.
Analytical Electron Microscopy of Precipitates in Ion-Implanted Mgal2O4 Spinel
Authors: Evans N. D. , Zinkle S. J. , Bentley J. 
Published: April 2011

AbstractAnalytical electron microscopy (AEM) has been used to investigate precipitates in MgAl2O4 spinel implantated with Al+, Mg+, or Fe2+ ions. Experiments combining diffraction, energy dispersive X-ray spectrometry (EDS), electron energy-loss spectrometry (EELS), and energy-filtered imaging were employed to identify and characterize precipitates observed in the implanted ion region. Diffraction studies suggested these are metallic aluminum colloids, although EELS and energy-filtered images revealed this to be so only for the Al+ and Mg+ implantations, but not for Fe2+ ion implantations. Multiple-least-squares (MLS) fitting of EELS plasmon spectra was employed to quantify the volume fraction of metallic aluminum in the implanted ion region. Energy-filtered plasmon images of the implanted ion region clearly show the colloid distribution in the Al+ and Mg+ implanted spinel. Energy-filtered images from the Fe2+ ion implanted spinel indicate that the features visible in diffraction contrast cannot be associated with either metallic aluminum or iron-rich precipitates.
Materials for Reverse Saturable Absorption Optical Limiters
Authors: Shirk James S. , Pong Richard G. S. , Flom Steven R. , Boyle Michael E. , Snow Arthur W. 
Published: April 2011

AbstractSystematic studies of the nonlinear optical properties of metallo-organic materials have led to the development of promising new phthalocyanine materials for optical limiting. Several heavy metal substituted phthalocyanines exhibit a strong nonlinear absorption that is useful for optical limiters in the visible. In fast optical systems, other mechanisms, such as the thermal refraction, contribute to the limiting. The spectral window for limiting can by modified by altering the molecular structure.
Nonlinear Absorption in Organic Dyes
Authors: Welford K. R. , Swatton S. N. R. , Hughes S. , Till S. J. , Spruce G. , Hollins R. C. , Wherrett B. S. 
Published: April 2011

AbstractThe non-linear optical properties of chloro-aluminium phthalocyanine and 1,3,3,1′,3′,3′- hexamethylindotricarbocyanine have been studied as model systems using z-scan and time resolved experimental techniques. Excited state lifetimes and absorption cross sections have been measured as well as the spectral response of the induced absorption. Excited state lifetimes are critical in determining the performance of a reverse saturable absorber. Even though a first excited state absorption cross section may be large compared with the ground state absorption cross section the lifetimes and transition probabilities of higher lying states can lead to constraints upon how effective organic dyes are as optical limiting materials.Both novel saturation of the induced absorption at high laser fluences and intermolecular quantum beats in 1,3,3, 1′,3′,3′-hexamethylindotricarbocyanine are demonstrated experimentally and accounted for theoretically. Quantum chemical calculations have been developed to propose a probable inter-molecular mechanism for the observed quantum beats.
Metal Organic Complexes for Optical Power Limiting
Authors: Lawson Chris M. , Zhai Tianyi , Gale David C. , Gray Gary M. 
Published: April 2011

AbstractNonlinear optical properties of transition metal-phosphine complexes have been measured at 532 nm by degenerate four-wave mixing. Large second-order molecular hyperpolarizabilities, γ, have been found for complexes containing two phosphine ligands. The measured γ values are closely related to the type and coordination geometry of the phosphine ligands, and the γ values vary as the fifth power of the number of substituents with π-electrons structure.
Thin Film Optical Switching Materials
Authors: Natale J. F. DE 
Published: April 2011

AbstractThe oxides of vanadium, VO2 and V2O3, are attractive materials for optical switching applications due to their large excursions in both electrical and IR optical properties. These materials can be prepared in thin film form by a number of deposition techniques, making them compatible with optical and electrical device applications. The performance of these films is a sensitive function of microstructure and processing conditions. The effects of these variables are discussed.
Is Thermalization Due to Electronic Self-Trapplng?
Authors: Kemp Mathieu 
Published: April 2011

ABSTRACTThe interpretation that the red shift of the a-Si:H photoluminescence spectrum is due to carrier hopping is incompatible with Monte-Carlo simulations. We suggest that thermalization is instead the result of slow, gradual, electronic self-trapping. We show how this model reconciles the narrowness of the photoluminescence lifetime distribution with the observed red-shift of the energy spectrum.
Characterization of Localized Density of States in Intrinsic a-Si and poly-Si Films by Transient Voltage Spectroscopy
Authors: Kawachi G. , Ishii M. , Tanaka T. , Konishi N. 
Published: April 2011

ABSTRACTThe localized density of states (LDOS) at interfaces between intrinsic silicon and silicon nitride (Si3N4 films are studied using transient voltage spectroscopy (TVS). In the TVS technique, the transient of the voltage across a MIS-diode after a trap filling voltage pulse is measured using a high-impedance voltage probe. This allows us to make a precise measurement of the LDOS at undoped Si/insulator interfaces. The LDOS in a-Si:H/Si3N4systems has a broad peak around the energy of 0.9 eV below the conduction-band edge. A modification of the LDOS at a-Si:H/Si3N4 interfaces by bias-annealing is clearly observed using this technique. The results are consistent with the defect pool model. The LDOS in laser annealed poly-Si/Si3N4 systems has a peak centered 0.6eV below the conduction-band edge, which seems to be the Si dangling bond states in the poly-Si films.
The Role of Deep Defect Relaxation Dynamics in Optical Processes in Hydrogenated Amorphous Silicon
Authors: Zhong Fan , David Cohen J. 
Published: April 2011

ABSTRACTWe report results of a transient modulated photocurrent technique which allows us to observe the time evolution of the D0 sub-band under the application of optical bias light and after turning off this bias light Our measurements show that the D0 band shifts monotonically to shallower thermal energies after the bias light is applied, with roughly 10 seconds to saturation at 300K and to deeper thermal energies after removing the bias light, with a decay time of over 1000 seconds. We have also found there exists an intimate relation between the motion of the D0 band and that of the quasi Fermi level as deduced from the transient photoconductivity and therefore, in particular, to the long time photoconductivity decay. This relation is exactly reproduced by the assumption of a D0 band whose energy position evolves in time, together with a recombination process dominated by changes in the charge state of a deeper defect band under light bias.
Origin of Photodegradation in a-Si:H - Bond Breaking or Charge Trapplng?
Authors: Shimizu Tatsuo , Kumeda Minoru , Zhang Qing , Zhang Jinyan , Ohtsuka Toshihiro 
Published: April 2011

ABSTRACTIn order to clarify the microscopic origin of the photodegradation in a-Si:II, two kinds of approaches have been done. One approach is to carry out the light soaking both at room temperature (RT) and 77 K to cause the photodegradation and to investigate the recovery by thermal annealing. The other approach is to investigate the light-induced ESR in hydrogenated amorphous silicon-nitrogen alloys (a-Si1-xNx:H) and to see the x-dependence down to x = 0. From the first approach, it is found that there is a very broad continuous distribution of annealing activation energies from a few eV through 1.4 eV. It appears less likely that such a wide distribution of annealing activation energy is related with the bond-breaking model. On the other hand, it is found from the second approach that there exist two distinct origins for the light-induced spins, the fast process and the slow process, which are likely to be the carrier capture and the bond breaking, respectively. From the continuation of the observed behavior to a-Si:H, that is, x = 0 in a-Si1-xNx:H, the RT photodegradation in a-Si:H appears to be the bond breaking.
Thermodynamics and Kinetics of Hydrogen Evolution in Hydrogenated Amorphous Silicon Films
Authors: Sridhar Nagarajan , Chung D. D. L. , Anderson W. A. 
Published: April 2011

ABSTRACTThe enthalpy (endothermic) of hydrogen evolution from p-type (boron doped) amorphous silicon with 17 at. % H was 4.8, 10.3, 15.8 and 17.3 kJ/g, the evolution temperature was 585, 606, 625 and 644 °C and the entropy of evolution was 5.6, 11.7, 17.5 and 18.9 J/g.K at heating rates of 5, 10, 20 and 30 °C/min respectively. That the enthalpy and entropy increased with heating rate means that the evolution involves not only Si-H bond breaking, but also Si-Si bond breaking and other defect formation. The Si-Si bond breaking and defect formation were enhanced at high heating rates, which caused high rates of hydrogen evolution. For n-type (phosphorous-doped) and intrinsic amorphous silicon with 25 and 23 at. % H respectively, the enthalpy and entropy of hydrogen evolution were higher than the p-type case, due to severe defect formation resulting from the higher hydrogen content. The activation energy of hydrogen evolution was 1.38, 2.5 and 4 kJ/g for the p-type, intrinsic and n-type materials respectively. Crystallization which occurred at temperatures higher than hydrogen evolution, was delayed for the amorphous silicon film in a higher disordered state after hydrogen evolution, suggesting that hydrogen evolution influenced the crystallization process.
Thermal Equilibrium Processes in a-Si:H Solar Cells
Authors: Lee Jae-Hee , Koh Jae-Seog , Jang Jin 
Published: April 2011

ABSTRACTHydrogenated amorphous silicon (a-Si:H) solar cells are prepared by plasma enhanced chemical vapor deposition (PECVD). Before quenching the solar cells, the short circuit current (Jsc), open circuit voltage (Voc), fill factor (F. F.) and conversion efficiency (η) are 17.79 mA/cm2, 0.79 V, 53.29, and 7.49 %, respectively. After thermal quenchine the solar cells from 200°C, Jsc, Voc, F. F., and η are 18.64 mA/cm2, 0.8 V, 53.79, and 8.02 %, respectively. We investigated the thermal equilibrium processes of each P, I, and N layers. Also, we obtained the dark current-voltage characteristics of a-Si:H solar cells before and after quenching. We analyze the results in terms of the change of the internal electric field in a-Si:H solar cells, caused by the shift of the Fermi level of P layer toward valence band.
Light-Induced Changes Among Fast-Relaxing Hydrogens in Plasma-Deposited Hydrogenated Amorphous Silicon
Authors: Kernan M. J. , Corey R. L. , Fedders P. A. , Leopold D. J. , Norberg R. E. , Turner W. A. , Paul W. 
Published: April 2011

ABSTRACTLight-induced rearrangements in a-Si:H,D during and after illumination have been studied by deuteron magnetic resonance (DMR). A film sample was deposited on a 230°C Al substrate by plasma decomposition of S1H4 and D2. The high quality film contained 4 at.% H and 4 at. % D. DMR spectra of fast-relaxing components were examined at 700 msec or less after radio frequency saturation. At 30 K these showed a broad central signal (primarily nanovoid-trapped HD and D2), part of which shifted paramagnetically during illumination. No comparable shifts were shown by spectral components from Si-bonded hydrogen or from microvoid-contained dense fluid hydrogen. The observed post-illumination shifts vanished upon 150°C dark anneal and reflected light-induced metastable magnetic changes in the surroundings of hydrogen trapped in nanovoids.
Optoelectronic Properties of High-Gap Amorphous Silicon-Carbon Alloys
Authors: Chu V. , Conde J. P. , Brogueira P. , Micaelo P. , Jarego J. P. , da Silva M. F. , Soares J. C. 
Published: April 2011

ABSTRACTThe dependence of the properties of hydrogenated amorphous silicon-carbon alloys deposited with a 1:10 silane (SiH4) to methane (CH4) or ethylene (C2H4) gas flow ratios with the hydrogen dilution, deposition pressure and power is studied. In methane-based films the carbon content shows a decrease (from ≈0.75 to 0.55) with increasing hydrogen dilution from 0 to 98%, while the ethylene-based films show no dependence of the carbon fraction (≈0.9) on hydrogen dilution. The photoconductivity shows an increase for hydrogen dilutions above 90= for both methane and ethylene-based films. While this increase is attributed, in the case of methane, to the observed decrease in carbon content, no corresponding decrease in carbon content is observed in the ethylene-based films, suggesting a decrease in the density of recombination centers with hydrogen dilution. The Urbach tail and the room-temperature photoluminescence peak correlate with carbon content independent of the carbon source-gas and deposition conditions used.
Thermopower and 1/f Noise Measurements in Amorphous Silicon-Carbon Alloys
Authors: Dyalsingh H. M. , Khera G. M. , Kakalios J. 
Published: April 2011

ABSTRACTThermopower, conductivity and 1/f noise measurements have been performed on a series of n-type doped hydrogenated amorphous silicon carbon films that are prepared with varying gas phase concentrations of CH4. The increased disorder at the mobility edge associated with alloying is characterized by the Q-function, which is obtained by combining thermopower and conductivity measurements, and is also reflected in the noise power spectra and noise statistics.
Spectral Response of a-Si:H p-i-n Solar Cells Degraded by Blue and Red Light
Authors: Mittiga A. , Mariuc L. , Fasolino T. , Romano A. , Fiorini P. , Bonito P. 
Published: April 2011

ABSTRACTWe have degraded a-Si:H p-i-n solar cells at Voc using both red and blue light to investigate the effect of a possible different spatial distribution of defects in the intrinsic layer. We have found that the I-V and the spectral response curves of the degraded cells depend on the total density of defects only and are not sensitive to the wavelength of the degradation light. These experimental results and some peculiar features of the spectral response of the degraded cells are explained with the aid of a numerical simulation program.
Fabrication of Undoped and N+ Microcrystalline si Films Using SiH2Ci2
Authors: Byun Jae Seong , Jeon Hong Bin , Jun Jung Mok , Yoo Jae Ho , Lee Kyung Ha , Park Min , Jang Jin 
Published: April 2011

ABSTRACTWe have studied the growth of undoped and n+ μc-Si:H (:CI) films by Remote Plasma CVD using SiH4/SiH2Cl2/H2/He mixtures. It was found that the μc-Si film can be fabricated by increasing flow rate of SiH2Cl2 and/or H2. The deposited undoped μc-Si film exhibited a maximum crystalline volume fraction of 85 %, obtained from Raman spectroscopy. The n-type μc-Si film, deposited with SiH4/SiH2Cl2/H2/PH3/He mixtures, shows a room temperature conductivity of 2 S/cm, conductivity activation energy of 29.8 meV and optical band gap of-2.0 eV. The optical band gap of n-type μc-S1 deposited using SiH2Cl2 is much higher compared to conventional μc-Si film.
c-Si (n +)/a-Si Alloy/Pd Schottky Barrier Device for the Effective Evaluation of Photovoltaic Performance of a-Si Alloy Materials
Authors: Deng X. , Jones S. J. , Evans J. , Izu M. 
Published: April 2011

ABSTRACTThe Schottky barrier device with a metal/a-Si (n+) /a-Si alloy/metal structure has been widely used as an alternative evaluation tool for the photovoltaic performance of a-Si alloy material since it more reliably reflects the carrier transport in a solar cell than the conventional material characterization tool such as PDS, CPM, and SSPG, and is easier to be fabricated compared with a complete nip solar cell. However, a multiple chamber device making system is still needed to fabricate such a device since one does not want to deposit the a-Si intrinsic material to be studied together with an n+ layer in the same chamber. We have explored the use of a Schottky barrier device deposited on heavily doped n-type crystalline wafer substrate, c-Si (n+) /a-Si alloy/metal, as an evaluation tool for a-Si alloy materials. In this device, besides the evaporation of a thin semi-transparent metal layer, only the active a-Si alloy layer needs to be deposited using the plasma enhanced or other deposition techniques. We have compared the performance of such a device with that of reference n-i-p solar cells deposited at the same time and demonstrated that the FF measured under weak red light show a good correlation between these two types of devices. Therefore the c-Si (n+) /a-Si alloy/metal device can be used as a convenient technique to reliably evaluate the material performance in a solar cell device.
Properties of Glass Substrates for Poly-Si Amlcd Technology
Authors: Moffatt Dawne M. 
Published: April 2011

ABSTRACTA major force for change in substrate requirements in the late 90's may well be the commercialization of poly-silicon thin film transistor (TFT) Active Matrix Liquid Crystal Display (AMLCDs) technology. The processes necessary for “poly-Si” occur at temperatures that are 150–300°C higher than the current amorphous-Si LCD processes. This impacts the thermal shrinkage and thermal gravimetric warp requirements of the glass, particularly as display resolutions tighten, as enabled by poly-Si. In addition, the expected integration of more components (e.g. chip-on-glass) impacts the requirements for the thermal expansion of the substrate.One approach for meeting the poly-Si demands for greater thermal-dimensional stability is to use glasses with higher temperature capability. A new glass, Code 1737, with the highest strain point commercially available at over 660°C, now enables poly-Si processing with acceptable sag and shrinkage after annealing. A logical goal for the next significant glass advancement would be to eliminate annealing altogether, but it is unclear what temperature capability is required. In this study, various glasses with strain points ranging from 600–800°C have been evaluated in terms of their density, thermal expansion, and thermal shrinkage following poly-Si thermal process simulations. It has been confirmed that the magnitude of shrinkage decreases with increasing strain point for glasses in this compositional family. In addition, future new insight into the effect of thermal expansion coefficient has been developed; the lower the thermal expansion coefficient (for a given strain point), the lower the magnitude of the shrinkage for a given strain point and high temperature thermal cycle. This is important new learning in the area of substrates for flat panel displays that will help in further design and development of glasses for future AMLCDs.