bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seismic Velocity Structure of the EDZ Around Drifts at the Kamaishi and Tono Mines in Japan
Authors: Sato T. , Matsui H. , Kikuchi T. , Sugihara K. , Okubo S. 
Published: April 2011

ABSTRACTThe excavation disturbed zone (EDZ) is defined as the rock zone where rock properties and conditions have been changed due to the processes induced by excavation, such as excavation damage, stress redistribution and desaturation. In-situ excavation disturbance experiment has been performed to determine the rock properties and width of the EDZ at the Kamaishi and Tono mines in Japan. Rock mass fails when blasting vibration velocity exceeds limit velocity so that we can estimate excavation damaged zone from vibration measurement. The width of the zone where blasting vibration velocity exceeded the limit velocity is roughly consistent with the width of low seismic velocity layer detected from the seismic refraction survey at both mines.
Self-Radiation-Induced Anisotropic Structure Damage in 244Cm-Doped Orthophosphate LuPO4
Authors: Liu G. K. , Luo J. S. , Li S. T. , Loong C.-K. , Abraham M. M. , Beitz J. V. , Bates J. K. , Boatner L. A. 
Published: April 2011

ABSTRACTWe have conducted a series of experiments using laser spectroscopy and analytic electron microscopy (AEM) to study the microscopic effects of radiation damage in single crystals of LuPO4 doped with 244Cm3+ ions. The crystals (body-centered tetragonal, zircon-type structure) were grown in 1980 using a flux method with an initial 244Cm(t1/2 =18.1 y) concentration of ∼1% by weight. The dimensions of the single crystals of Cm3+:LuPO4 are about 0.5×1.0×4.0 mm3. After 17 years, the crystals are no longer transparent. Dark brown to gray straps along the crystal c-axis are observable under an optical microscope. Macroscopic fractures are not obvious on the natural surfaces of the a- and b-planes. However, due to alpha-particle emission of 244Cm, significant microscopic structural damage, including microscopic cavities, has accumulated in this end member of the xenotime minerals
Conceptual Models for Geochemical Processes in Reactive Transport of Compacted Bentonites
Authors: Delgado Jorge , Samper Javier , Molinero Jorge , Juncosa Ricardo , Juanes Rubén , Carretero Pablo 
Published: April 2011

ABSTRACTSeveral agencies in charge of nuclear waste management consider the use of compacted bentonites as engineered barriers for the migration of radionuclides towards the geosphere. The geochemical processes occurring in the clay buffer system are of capital importance for the assessment of a HLW repository performance. Therefore, it is necessary to develop tools able to deal with the complex interactions between water and bentonite, submitted simultaneously to a thermal field and water flow. These tools may be referenced as thermo-hydro-geochemical (THG) modelling codes
Prediction of Solid-Aqueous Equilibria in Cementitious Systems Using Gibbs Energy Minimization: I. Multiphase Aqueous - Ideal Solid Solution Models
Authors: Sinitsyn V.A. , Kulik D.A. , Khodorivsky M.S. , Karpov I.K. 
Published: April 2011

ABSTRACTConcrete and other cement-based materials are increasingly utilized as major structural components of the disposal facilities for low-level and intermediate-level radioactive waste (LLW/ILW). At the same time. cementitious materials function as engineered barriers against migration of radionuclides and other hazardous compounds [1]. Taking into account the expected operation times of such constructions, the long-term prediction of environmental interactions and stability of concretes is important for the development of reliable facilities for LLW/ILW disposal. Thermodynamic approach has been widely used to promote understanding of chemical phenomena in cementitious systems. Recently, several authors attempted to demonstrate usefulness of computer codes for description of the available experimental data and prediction of cement/water equilibria [1-5]. These calculations were based on the Law-of-Mass Action - Reaction Stoichiometry Algorithm (LMA-RSA), widely applied so far in speciation modeling [6]
Corrosion of Carbon Steel Containers During Open Site Tests of Vitrified Radioactive Waste
Authors: Barinov A.S. , Ojovan M.I. , Ojovan N.V. 
Published: April 2011

ABSTRACTIn the middle of 80-s the Moscow SIA “Radon” initiates a program on long term tests of vitrified intermediate level radioactive waste from nuclear power plants with different types'of reactors and with different composition of waste. Glass blocks were prepared and disposed for tests in experimental shallow ground repository and on open testing area. Borosilicate glass as matrix material is investigated in order to obtain data on real behaviour of glass [1]. The waste glass was poured in carbon steel rectangular containers therefore containers also were subjected to aqueous and atmospheric corrosion. Exposure conditions at testing site are varying depending on season. They can be described only as average parameters with some uncertainties.
Development of Stable a-Si/a-SiGe Tandem Solar Cell Submodules Deposited by a Very High Hydrogen Dilution at Low Temperature
Authors: Shima Masaki , Isomura Masao , Maruyama Eiji , Okamoto Shingo , Haku Hisao , Wakisaka Kenichiro , Kiyama Seiichi , Tsuda Shinya 
Published: April 2011

ABSTRACTThe world's highest stabilized efficiency of 9.5% (light-soaked and measured by the Japan Quality Assurance Organization (JQA)) for an a-Si/a-SiGe superstrate-type solar cell submodule (area: 1200 cm2) has been achieved. This value was obtained by investigating the effects of very-high hydrogen dilution of up to 54:1 (= H2: SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) deposition at a low substrate temperature (Ts). It was found that deterioration of the film properties of a-SiGe:H when Ts decreases under low hydrogen dilution conditions can be suppressed by the high hydrogen dilution. This finding probably indicates that the energy provided by hydrogen radicals substitutes for the lost energy caused by the decrease in Ts and that sufficient surface reactions can occur. In addition, results from an estimation of the hydrogen and germanium contents of a-SiGe:H suggest the occurrence of some kinds of structural variations by the high hydrogen dilution. A guideline for optimization of a-SiGe:H films for solar cells can be presented on the basis of the experimental results. The possibility of a-SiGe:H as a narrow gap material for a-Si stacked solar cells in contrast with microcrystalline silicon (μ c-Si:H) will also be discussed from various standpoints. At present, a-SiGe:H is considered to have an advantage over μ1 c-Si:H.
Reaction Processes for Low Temperature (<150°C) Plasma Enhanced Deposition of Hydrogenated Amorphous Silicon Thin Film Transistors on Transparent Plastic Substrates
Authors: Parsons Gregory N. , Yang Chien-Sheng , Klein Tonya M. , Smith Laura 
Published: April 2011

ABSTRACTThis article presents mechanisms for low temperature (<150°C) rf plasma enhanced chemical vapor deposition of silicon and silicon nitride thin films that lead to sufficient electronic quality for thin film transistor (TFT) fabrication and operation. For silicon deposition, hydrogen abstraction and etching, and silicon disproportionation reactions are identified that can lead to optimized hydrogen concentration and bonding environments at <150°C. Nitrogen dilution of SiH4/NH3 mixtures during silicon nitride deposition at low temperatures helps promote N-H bonding, leading to reduced charge trapping. Good quality amorphous silicon TFT's fabricated with a maximum processing temperature of 110°C are demonstrated on flexible transparent plastic substrates. Transistors formed with the same process on glass and plastic show linear mobilities of 0.33 and 0.12 cm2/Vs, respectively, with ION/IOFF ratios > 106.
Stabilized Three Color Piinip Sensor For High Illumination Conditions
Authors: Knipp D. , Stiebig H. , Wagner H. 
Published: April 2011

ABSTRACTA stabilized three color piinip sensor for high illumination conditions was developed. The spectral response of the novel device shows a maximum at 480nm, 530nm and 630nm changing the applied bias voltage from −0·2V, −2·OV to 2·OV, respectively. Only a slight influence on the device performances is observed after more than 100h light soaking under AM1·5 illumination conditions. This is achieved by employing low temperature deposited a-Si:H with high hydrogen dilution and a microcrystalline silicon layer in the top diode of the sensor. For piinip detector systems with different absorption materials in the top diode the influence of light induced degradation on the spectral response and the dark current is discussed. Furthermore, the transient behavior of the new stabilized detector is presented.
Stepped Gate Polysilicon Thin Film Transistor for Large Area Power Applications
Authors: Aschenbeck J. , Chen Y. , Clough F. , Xu Y. Z. , Narayanan E. M. Sankara , Milne W. I. 
Published: April 2011

ABSTRACTFor the first time, we report a new poly-Si stepped gate Thin Film Transistor (SG TFT) on glass. The Density of States extracted from measured I-V characteristics has been used to evaluate the device performance with a two dimensional device simulator. The results show that the three-terminal SG TFT device has a switching speed comparable to a low voltage structure and the high on-current capability of a metal field plate (MFP) TFT and the potential for comparable breakdown characteristics.
The Tail States as Sensitizing Recombination Centers for Holes Lifetime in a-Si:H
Authors: Lubianiker Y. , Rapaport R. , Balberg I. , Fonseca L. , Weisz S.Z. 
Published: April 2011

ABSTRACTWe have measured the dependence of the holes mobility-lifetime product on temperature under various light intensities in intrinsic a-Si:H. We find that this product exhibits thermal quenching which is accompanied by a superlinear light intensity dependence. Numerical calculations that we have carried out show that these results can be accounted for within the framework of the conventional recombination model. However, to yield such an agreement the capture coefficients for both charge carriers at the tail states must be smaller than the corresponding coefficients for the dangling bonds. Thus the sensitizing nature of the tail states is revealed.
Variation of Bandgap in Nanocrystalline Silicon as Monitored by Subgap Photoluminescence
Authors: Kalkan A. Kaan , Bae Sanghoon , Cheng Shangcong , Wang Yaozu , Fonash Stephen J. 
Published: April 2011

ABSTRACTInfrared PL from νc-Si and nc-Si thin films is a potential spectroscopic tool for sensitive diagnostics of structure and defects. Bhat et al. have shown that the dominant PL band found in νc-Si centered at 0.9 eV cannot be assigned to the amorphous phase, as the energeticaly similar defect band found in a-Si:H (i.e., at 0.9 eV) shows a different temperature dependence and is much broader (i.e., FWHM of 0.15 eV compared to 0.35 eV) [1]. Recently, Carius et al. have observed a gradual lower energy shift of the 0.9 eV PL down to 0.82 eV for nc-Si as the plasma deposition excitation frequency is increased with a corresponding decrease in FWHM from 0.15 0.12 eV, respectively [2]. However, a lower energy shift in optical absorption was not observed, nor did they look for a correlation with the variation of any other physical property. Here, we report a broader range of energy variation for PL from our ECR-PECVD deposited nc-Si films accompanied with an energy shift in optical absorption and variation in dark conductivity and crystallite size. It has been argued that this PL peak in question could arise from the radiative transitions between bandtail states as in the case of ∼1.3 eV PL in a-Si:H or it may be associated with structural defects [2,3]. Our observations support both possibilities.
X-Ray Sensing Properties of a Lead Oxide Photoconductor Combined With an Amorphous Silicon Tft Array
Authors: Brauers A. , Conrads N. , Frings G. , Schiebel U. , Powell M.J. , Glasse C. 
Published: April 2011

ABSTRACTWe present first results on the performance of flat dynamic x-ray detectors (FDXD) based on arrays of amorphous silicon thin film transistors (TFT) with charge storage capacitances and lead oxide as x-ray photoconductor. In order to increase the “active area” of every pixel, the layout of the array has been made in a multilevel arrangement, where the charge collecting electrode is separated from the underlying electronics by a thick insulating layer. This allows for a geometrical overlap of the pixel electrodes and TFTs. PbO has been chosen as the x-ray sensing material due to its very high x-ray sensitivity. The relevant detector properties of evaporated PbO layers are described along with results obtained on first FDXD devices with PbO.
First Monolithic Tandem Photovoltaic-Powered Electrochromic Smart Window
Authors: Gao W. , Lee S.H. , Xu Y. , Morrison S. , Benson D.K. , Branz H.M. 
Published: April 2011

ABSTRACTWe report on the first monolithic, amorphous-silicon-based, photovoltaic-powered electrochromic window coating. The coating employs a wide bandgap a-Sil-xCx:H n-i-p photovoltaic (PV) cell as a semitransparent power supply, and a LiyWO3/LiAlF4/V205 electrochromic (EC) device as an optical-transmittance modulator. The EC device is deposited directly on top of a PV device that coats a glass substrate.The a-Sil-xCx:H PV cell has a Tauc gap of 2.2 eV and a transmittance of 60 to 80% over a large portion of the visible light spectrum. We reduced the thickness of the device to about 600 Å while maintaining a 1-sun open-circuit voltage of 0.9 V and short-circuit current of 2 mA/cm2.Our prototype 16 cm2 PV/EC device modulates the transmittance by more than 60% over a large portion of the visible spectrum. The coloring and bleaching times of the electrochromic device are approximately 1 minute under normal operating conditions (±1 volt).
Band-Offset Determination for Intrinsic a-Si/ p+μc-Si or Intrinsic a-Si/n+νc-Si Heterostructure
Authors: Zhu Hong , Fonash Stephen J 
Published: April 2011

ABSTRACTThe conduction band ΔEcand valance band ΔEv, off-sets at interfaces are critical parameters for device simulation. With the transport simulation code AMPS we demonstrate the possibility of using an analysis of the far forward I-V characteristics versus temperature for i- layer /n+or i-layer /p+hetero structures to obtain ΔEcor AE., respectively. For example, if one wants to extract AE, from experimental data for the interface a-Si/uc n+Si interface, we show this can be done using a metal/intrinsic a-Si:H/uc n+Si structure. With proper choice of the metal, the hole barrier height at the metal can be made large enough that the far forward current is only carried by electrons. We have found that, with the proper choice of structure thickness this far forward current can be controlled by ΔEcand not by space charge limited current. Unlike the work of Arnold et al [1], we have found that the choice of structure thickness is critical. In this case of an a-Si/uc n+structure this far forward current is actually controlled by ΔEC+ΔVnwhere ΔVnis the activation energy in the n+uc-Si layer. Since ΔVncan typically be ∼ 0.05eV in uc-Si, we see that ΔEcis essentially controlling this far forward current. To demonstrate the approach for the case of an a-Si/uc n+Si interface we consider different i-layer thicknesses.
Plasma Deposition of Silicon Clusters: A Way to Produce Silicon Thin Films With Medium-Range Order ?
Authors: Cabarrocas P. Roca i 
Published: April 2011

ABSTRACTThe growth of hydrogenated amorphous silicon films is often explained by the arrival of SiHx radicals on the substrate and the subsequent cross-linking reactions leading to an homogeneous material which can be described by a continuous random network. Here we summarize our recent Work on a new class of silicon thin films produced under plasma conditions where silicon clusters and radicals contribute to the deposition. The main aspects are: i) silicon clusters with sizes of the order of 1-5 nm are easily formed in silane plasmas; ii) these silicon clusters can contribute to the deposition and lead to the formation of films with medium-range order (“polymorphous silicon”); iii) despite their heterogeneity, the films have improved transport properties and stability with respect to a-Si:H. The excellent transport properties are confirmed by the achievement of stable single junction p-i-n solar cells with efficiencies close to 10 %.
Investigation of the Electronic Transport in Pin Solar Cells Based on Microcrystalline Silicon by 2D Numerical Modeling
Authors: Zimmer J. , Stiebig H. , Wagner H. 
Published: April 2011

ABSTRACTWe investigated the transport and recombination behavior of pin solar cells based on micro- crystalline silicon (μc-Si:H). A comparison of experimental and simulated data of the dark I/V- curves, the I/V-behavior under AM1.5 illumination as well as the quantum efficiency reveals an enhanced defect density in μc-Si:H compared to c-Si which could be located as defect rich grain boundaries around the crystallites. Further, in case there is amorphous phase in the material, the distribution of a-Si:H around the crystallites is unlikely, since the electronic transport properties are disturbed, whereas an arrangement in the shape of extended areas does not affect the transport behavior significantly due to occurrence of percolation.
Small-Signal Admittance of Forward-Biased a-Si:H p+-i-n+ Diodes by Time Domain Analysis
Authors: Lemmi F. , Johnson N. M. 
Published: April 2011

ABSTRACTIn order to study the observed frequency variation of small-signal admittance of forward- biased amorphous silicon (a-Si:H) p-i-n diodes, we performed time-resolved measurements of currents induced by application of a small voltage step superimposed on a constant DC bias. The small amplitude ensures a linear behavior of the system under study. The transient current response includes all the details necessary to explain the stationary response to small sine-wave excitation. Details are obtained through a Fourier transform of the transient current. The real and imaginary parts of the resulting complex current are related to the capacitance and conductance spectra. This approach can explain phenomena taking place in the stationary regime such as negative capacitance values measured at low frequencies.In the frequency domain, measured capacitances do show negative values, as well as a clear dependence on the applied forward bias voltage. Namely, higher voltages extend the region in which the phenomenon occurs to higher frequencies of the probe signal. In the time domain, all measured transient currents exhibit common features such as an initial decay after the displacement current and, for higher DC biases, a gradual increase. A physical explanation of the current transient is proposed which accounts for the dependence on applied DC bias. A mathematical model is used to show how a delayed increase in the current leads to a modulation of the capacitance and conductance in the frequency domain, the two being related to each other. This finally allows the comprehension of the observed frequency domain behavior.
Investigation of a-Si:H PH(1)N Color Detector Operation
Authors: Topiĉ M. , Smole F. , Furlan J. 
Published: April 2011

ABSTRACTUsing numerical simulator, the operational principle of two-terminal a-Si:H based three-color detectors with the multi-layer multi-bandgap PIN or PIIiN structure is investigated. Two different approaches, which lead to bias-controlled three-color detection, are described and evaluated in terms of spectral response, rejection ratio, color suppression, illumination intensity and bias-light. For both PIIN and PIIN structure, bias-light dependence and intensity dependence is investigated. Numerical simulation results showed strong negative correlation between color separation and bias-light sensitivity. The importance of the transparent conducting oxide for the three-color detection limits is demonstrated.
Enhanced Crystallinity of Microcrystalline Silicon Thin Films Using Deuterium in Reactive Magnetron Sputter Deposition at 230°C
Authors: Gerbi J. E. , Voyles P. , Gibson J. M. , Abelson O J. R. 
Published: April 2011

ABSTRACTWe analyze the formation kinetics and microstructure of hydrogenated vs. deuterated microcrystalline (μc-Si:H or D) thin films using real-time spectroscopic ellipsometry, post- deposition thermal hydrogen evolution, and TEM. The films are deposited by reactive magnetron sputtering of a silicon target in Ar (1.65 mT) with added partial pressures of H2or D2(0-5.5mT) on Coming 7059 glass substrates at 230°C. Amorphous films are deposited when PH2=0. When hydrogen is added to the chamber, the reactive magnetron sputtering process generates a flux of fast neutral H which promotes stc-Si growth. The substitution of D for H varies the kinetics of hydrogen reflection from the target and implantation into the growing film. We analyze the amorphous to microcrystalline transition as a function of the isotope (H2or D2) and pressure used in the deposition process. We find that the films enter the microcrystalline regime at lower D2pressures than H2pressures. Furthermore, the <ε2> data determined by ellipsometry have a different shape for deuterated films, compared to hydrogenated films at similar growth pressures. This indicates changes in band structure which we interpret as evidence for enhanced crystallinity.
Influence of Plasma Chemistry on the Properties of Amorphous (Si,Ge) Alloy Devices
Authors: Dalal Vikram L. , Maxson Tim , Haroon Sohail 
Published: April 2011

ABSTRACTWe report on the growth and properties of a-(Si,Ge):H films and p-i-n solar cell devices prepared using a remote, low pressure ECR plasma deposition technique. The films and devices were prepared using either He or H2 as the diluent gas. The plasma conditions were controlled so as to induce significant ion bombardment during growth. We find that there is a dramatic influence of plasma chemistry on the growth and properties of a-(Si,Ge):H films and devices. In particular, with hydrogen as the diluent gas, changing the pressure in the reactor dramatically changes both the Germanium incorporation in the film, and the electronic properties. Lower pressures lead to less Ge being incorporated, and higher mobility-lifetime product for holes for a given Tauc gap, as well as better p-i-n devices. In contrast, changing the pressure when He is the diluent gas does not produce such large changes. We speculate that the changes in device and film properties are due to the influence of ion bombardment on growth chemistry, and that both efficient energy and momentum transfer to the growing surface are necessary to achieve the best devices. The differences between He and hydrogen may simply be due to the fact that He plasma is much more energetic than a comparable hydrogen plasma, and there is more efficient momentum transfer when He is used as compared to when hydrogen is used. We have also produced very good single junction a-(Si,Ge) devices using the ECR technique.
Silicon Clathrates: Synthesis and Characterization
Authors: Ramachandran Ganesh K. , Diefenbacher Jason , Sankey Otio F. , Sharma Renu , Marzke Robert F. , O'keeffe Michael , Gryko Jan , Mcmillan Paul F. 
Published: April 2011

ABSTRACTTwo types of silicon clathrates, NaxSi136 (0≤ × ≤ 24) and Na8Si46 and a mixed clathrate (Na,Ba)Si46 were synthesized and characterized by X-ray diffraction, 23Na NMR and high resolution TEM. Systematic changes in X-ray diffraction intensities enabled the sodium content and site occupancy in the NaxSi136 series to be followed and then refined by Rietveld profile analysis. 23Na NMR spectra of Na8Si46 and NaxSi136 samples reveals two peaks with large paramagnetic shifts (1600-2000 ppm) for each phase, associated with the presence of Na atoms in two different environments. High resolution electron microscopy reveals the clathrate structures of these samples, and allows classes of defects to be characterized.