bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissolution of Plutonium (III) Hydroxide at 50 bar H2
Authors: Nilsson Hans , Albinsson Yngve , Skarnemark Gunnar 
Published: April 2011

ABSTRACTIn the proposed Swedish nuclear fuel repository, intended to be placed some 500 meters down in granitic bedrock, the aquatic conditions will be reducing. In order to investigate the plutonium dissolution properties under near repository conditions Pu(III) was prepared using H2bubbling in the presence of a platinum wire. The plutonium oxidation state was checked by spectrophotometry and a blue Pu(OH)3precipitate was produced using deoxygenated NaOH. During drying the precipitate turned brownish and was then put in 0.1 M NaCl in pressure vessels. X-ray powder diffraction (XPD) showed no crystallinity of the precipitate. Solubility experiments were performed in pressure vessels that have an insert of PEEK (polyether-etherketone) and two valves, one for gas application and one with a PEEK tube reaching down into the vessel content for sample withdrawal. A small piece of platinum wire was put in each vessel and 50 bar H2was applied. The pH was adjusted to range from about 3 to 10. All handling was performed in an inert gas (N2) glove box with active oxygen removal yielding oxygen concentrations of <10 ppm. The results after about one year showed concentrations from 10−8M to 10−5M at pH 10 and pH 3 respectively.
A New Modelling of the Kinetics of Uranium Dioxide Oxidation in Air
Authors: Desgranges L. , Poinssot C. 
Published: April 2011

ABSTRACTA finite difference based modelling of the oxidation of uranium oxide is presented. This modelling involves only oxygen diffusion from the atmosphere into the solid and then inside the solid described with Fick's law. Some calculations performed with this modelling evidenced that the shape of the weight gain curves observed experimentally could be reproduced. This modelling is compared to the formula previously used to interpret the thermograms.
Structural Analyses of Layer Structure in Na-Montmorillonite using NMR
Authors: Ohkubo Takahiro , Kanehashi Koji , Saito Koji , Ikeda Yasuhisa 
Published: April 2011

ABSTRACTThe analyses of layer structure in Na-montmorillonite have been performed using 27Al MAS and 27Al Multi Quantum (MQ) MAS NMR techniques. In 27Al 5QMAS NMR spectra measured at higher magnetic field of 16.4 T, two peaks were observed at 74.2 and 62.9 ppm. Hence, it has been suggested that the 4-coordinated Al site in Na-montmorillonite has two different structures. For detail assignment of the two peaks due to such 4-coordinated Al sites in Na-montmorillonite, 27Al MAS NMR measurements have been carried out for Na-montmorillonites with different water contents. The ratio of two 4-coordinated Al sites was found to be affected by water in the interlayer space of Na-montmorillonite, because the area ratio of peaks corresponding to two 4-coordinated Al sites changes with the water content, i.e., the peak area at around 69 ppm is increased sensitively with an increase in water content. Moreover, Cross Polarization/MAS (CP/MAS) NMR measurements have been carried out. As a result, the enhancement of peak at around 69 ppm was observed. Therefore, the two peaks observed by 27Al 5QMAS methods are assigned to AlO4 in the vicinity of water bound to tetrahedral sheets and the remote AlO4 from such water, respectively.
Fluid Flow and Solute Transport though a Fracture Intersecting a Canister - Analytical Solutions for the Parallel Plate Model
Authors: Liu L. , Neretnieks I. 
Published: April 2011

ABSTRACTIn this paper, we are concerned with a specific scenario where a large fracture intersects, at its center, a canister that contains spent nuclear fuel. Assuming that a nuclide is free to release from the canister into groundwater flowing through the fracture, a detailed formulation of the volumetric flow rate and the equivalent flow rate are made for the parallel plate model. The formulas proposed have been validated by numerical examinations; they are not only simple in forms but also universal in applications where the flow may be taken normal, inclined or parallel to the axis of the canister. Of great importance, they provide a convenient way to predict the average properties of fluid flow and solute transport through a single fracture with spatially variable apertures.
Application of the M3 code for modelling groundwater chemistry
Authors: Laaksoharju Marcus , Gascoyne Mel , Gurban Ioana 
Published: April 2011

ABSTRACTThe need to decode the complex groundwater information in terms of origin, mixing (transport) and reactions at site scale, necessitated the development of a new modelling tool. This new modelling concept was named M3 (Multivariate Mixing and Mass-balance calculations). Initially, the method quantifies the contribution from the flow system. Subsequently, contributions from reactions are calculated. The M3 code has been used for the following types of modelling: to calculate the mixing portions at different sites and to quantify the contribution from inorganic and organic reactions. For instance, the groundwaters at many sites have been calculated to consist of complex mixtures of different water types such as meteoric water, biogenetically modified water, modern and ancient sea water, glacial meltwater and brine water. Examples from modelling of data from Äspö in Sweden, Oklo in Gabon and the URL in Canada are given.
Near-field/Far-field Interface of a Near-Surface Low-Level Radioactive Waste Site
Authors: Beadle I. R. , Graham J. , Boult S. , Hand V. L. , Warwick P. , Randall M. G. , Trivedi D. P. , Humphreys P. N. 
Published: April 2011

ABSTRACTExperimental and Modelling studies have been used to investigate the biogeochemical processes occurring at the interface zone between the near-field and far-field of the Drigg Low-Level radioactive Waste (LLW) trenches. These have led to a conceptual model of interface biogeochemistry, which has subsequently been modelled by the BNFL code known as the Generalised Repository Model (GRM). GRM simulations suggest that as organic rich leachate migrates into the far-field, iron III minerals such as iron hydroxide will dissolve, and reduced iron minerals such as siderite will precipitate due to microbial processes. Batch and column experimental studies have verified this conceptual understanding. Some unexpected processes, such as the presence of nitrate enhancing sulphate reduction, were also observed
Geochemical Model of the Granite-Bentonite-Groundwater at Äspö (LOT Experiment)
Authors: Domènech C. , Arcos D. , Bruno J. , Karnland O. , Muurinen A. 
Published: April 2011

ABSTRACTA geochemical modelling of one of the experimental parcels of the LOT experiment (Äspö, Sweden) is presented. The model consists on a 2D reactive transport model of a perpendicular section of the experimental borehole with a stationary temperature gradient ranging from 130 to 15°C. The results of the model show that temperature has an important effect on the geochemical evolution of the system. Due to the temperature effect, anhydrite replaces gypsum and hematite precipitates instead of Fe(OH)3(am). Calcite and siderite dissolve in the warmer part of bentonite; whereas a major replacement of Na by Ca in the bentonite takes place close to the bentonite-granite boundary. pH is buffered by the equilibrium with calcite, although the effect of temperature leads to a decrease in pH.
Modeling of Aluminum Induced Lateral Crystallization of Hydrogenated Amorphous Silicon
Authors: Abbasi Mohammad Saad , Abu-Safe Husam , Naseem Hameed , Brown W. D. 
Published: April 2011

ABSTRACTMetal induced lateral crystallization (MILC) of hydrogenated amorphous silicon (a-Si:H) was studied and a model was developed based on the resistance measurement of the films. Hydrogenated amorphous silicon films of 300 nm thickness were deposited using plasma enhanced chemical vapor deposition (PECVD) on oxidized p-type (100) silicon wafers. Thermally evaporated 200 nm thick aluminum layer was deposited over amorphous silicon and patterned using photolithography. The samples were annealed at different temperatures for different time periods. After annealing the resistance of amorphous silicon between aluminum pads was measured. Based on these measurements, a model was developed to predict the lateral crystallization velocity. In this model, the resistance change due to loss of hydrogen from the film was also taken into account. For this purpose, another set of experiments was conducted. In this set, hydrogenated amorphous silicon films of 300 nm thickness were deposited on Corning 7059 glass. The samples were annealed for different period of time at different temperatures. After annealing, parallel bars of silver paint were formed on the samples and the resistance of each sample was measured. The theoretically determined lateral crystallization velocity was verified using optical microscope observations and X-ray diffraction analysis and was found to be in close agreement.
Phase diagram and microstructure of microcrystalline and amorphous silicon: a numerical growth simulation
Authors: Bailat Julien , Vallat-Sauvain Evelyne , Vallat André , Shah Arvind 
Published: April 2011

ABSTRACTGrowth dynamics and microstructure of thin-film silicon simulated by a 3D dynamical numerical model are investigated. The model, recently introduced, is characterized here with its phase diagram. It reproduces the main features of the growth and microstructure of thin film silicon: amorphous to crystalline phase transition, conical/columnar shape of the conglomerates of nanocrystals, surface roughness evolution of the layer. It is observed that preferential etching of the amorphous silicon is sufficient to reproduce qualitatively the surface evolution observed experimentally. In the presence of preferential etching, nucleation of the microcrystalline phase in the simulated layers always coincides with a surface roughness increase as observed experimentally. This model opens new perspectives for the simulation of thin-film microstructure and surface morphology.
An Investigation of Silicon Oxide Thin Film by Atomic Layer Deposition
Authors: Lee Joo-Hyeon , Han Chang-Hee , Kim Un-Jung , Park Chong-Ook , Rha Sa-Kyun , Lee Won-Jun 
Published: April 2011

ABSTRACTSiO2 thin films were prepared on p-type Si (100) substrates by atomic layer deposition (ALD) using SiH2Cl2 and O3(1.5 at.%)/O2 as precursors at 300. The growth rate of the deposited films increased linearly with increasing amount of simultaneous SiH2Cl2 and O3 exposures, and was saturated at about 0.35 nm/cycle with the reactant exposures of more than 3.6×109L. A larger amount of O3/O2 than that of SiH2Cl2 was required to obtain a saturated deposition reaction. The composition of the deposited film also varied with O3/O2 exposure at a fixed SiH2Cl2 exposure. The Si/O ratio gradually decreased to 0.5 with increasing amount of O3/O2 exposure. Finally, we also compared the physical and electrical characteristics of the ALD films with those of the films deposited by conventional chemical vapor deposition (CVD) methods. In spite of low process temperature, the SiO2 film prepared by the ALD method was in wet etch rate, surface roughness, leakage current and breakdown voltage superior to that by other several CVD methods.
Development of Top-Gate Nanocrystalline Si:H Thin Film Transistors
Authors: McDonald Jarrod , Dalal Vikram L. , Noack Max 
Published: April 2011

ABSTRACTWe report on the growth and fabrication of top gate thin film transistors at low temperatures in nanocrystalline Si:H. The nanocrystalline Si:H was deposited using a VHF-PECVD plasma process at 45 MHz in a diode reactor. The material was deposited from a mixture of silane and hydrogen at a temperature of 250-300°C. Higher temperatures resulted in a loss of hydrogen from the material. The properties of the nanocrystalline Si:H were studied using x-ray diffraction and Raman spectroscopy. The material showed a high ratio (3.8) between the crystalline and amorphous peaks in the Raman spectrum. X-ray diffraction data showed the films to be predominantly oriented in <111> direction, and the grain size estimated from Scherer's formula was in the range of 12-15 nm. The doping of the material could be changed by introducing ppm levels of Boron or Phosphorus. The as-grown material was generally n type. By adding controlled amounts of B, the material could be made p type. The devices made were n-channel MISFET's with p body. The n+ source and drain layers were made from amorphous Si:H. A systematic investigation of the appropriate oxide/nitride layer to be used was undertaken. The nitride layers were grown at 250-300°C using mixtures of silane and ammonia, with a high degree of dilution by helium. The presence of helium dilution, along with post-deposition passivation by a hydrogen plasma, was found to produce reproducible, low interface defect density nitride materials. Interface state densities were measured using capacitance spectroscopy at different frequencies and temperatures and found to be in the range of 4.5x1011/cm2-eV. The breakdown strength of the nitride was measured and found to be 4 MV/cm. Proof-of-concept TFT devices were fabricated using reactive ion etching. The threshold voltage was in the range of 13-15 V, and the on/off ratio was in the range of 103.
Influence of catalyzer area and design on the growth of intrinsic hot-wire CVD thin-film silicon for photovoltaic applications
Authors: Kupich Markus , Grunsky Dmitry , Hofferberth Bernd , Schröder Bernd 
Published: April 2011

ABSTRACTRecently, hot-wire deposited microcrystalline silicon has attracted increasing attention. The use of hot-wire deposited intrinsic μc-Si:H for high efficiency solar cells was demonstrated by Klein et al. [1]. Integration of high-quality intrinsic μc-Si:H into all-hot-wire nip solar cells, prepared close to the transition to amorphous growth using a tantalum catalyzer, resulted in initial and stable efficiencies of 5.4 % on simple stainless steel substrates [2]. However, the deposition rates for the absorber material in both cases remained low, at values around 1 Å/s.In the present study we report on the dependence of deposition rate and material quality on the design and area of the tantalum catalyzer. It was found that different filament geometries require considerable changes in certain deposition conditions to optimize material properties. So, for example, enlarging the catalyzer surface made it necessary to decrease the hydrogen dilution of the process gas, in order to obtain the desired microcrystalline material close to the phase transition. These changes might be understood in terms of alterations of the gas decomposition relations on the catalyzer surface. For these modified conditions, deposition rates in the range of 2.5-10 Å/s could be achieved for μc-Si:H due to the fact that a higher silane fraction of the process gas could be used. For different wire geometries, the optimized intrinsic layers were incorporated into solar cells. Using a catalyzer with modified geometry and enlarged surface area, conversion efficiencies of ν = 4.4 % could be achieved for all-μc-Si:H, all-HWCVD solar cells at a rate of about 3 Å/s.
Measurement of the Electric Potential on Amorphous Silicon and Amorphous Silicon Germanium Alloy Thin-Film Solar Cells by Scanning Kelvin Probe Microscopy
Authors: Jiang C.-S. , Moutinho H. R. , Wang Q. , Al-Jassim M. M. , Yan B. , Yang J. , Guha S. 
Published: April 2011

ABSTRACTWe report on direct measurements of surface potentials on cross sections of a-Si:H and a-SiGe:H n-i-p solar cells using scanning Kelvin probe microscopy. External bias voltage (Vb)induced changes in the electric field distributions in the i layer were further deduced by taking the derivative of the Vb-induced potential changes. This procedure avoids the effect of surface charges or surface Fermi-level pinning on the potential measurement. We found that the electric field does not distribute uniformly through the i layer of a-Si:H cells, but it is stronger in the regions near the n and p layers than in the middle of the i layer. The non-uniformity is reduced by incorporating buffer layers at the n/i and i/p interfaces in the a-Si:H solar cells. For a-SiGe:H solar cells, the electric field at the p side of the i layer is much stronger than at the n side and the middle. The non-uniformity becomes more severe when a profiled Ge content is incorporated with a high Ge content on the p side. We speculate that the increase in defect density with increasing of Ge content causes charge accumulation at the i/p interface.
Electric-Field Dependence of Photocarrier Properties in the Steady-State Photocarrier Grating Experiment
Authors: Brüggemann R. , Badran R.I. 
Published: April 2011

ABSTRACTWe apply an experimental variation of the steady-state photocarrier grating technique by monitoring the photoresponse at higher electric fields and thus changing from diffusion to drift determined transport. Evaluation of the field-dependen experimental data is achieved with the analysis by Abel et al. [C.-D. Anel, G.H. Bauer and W. Bloss, Philos. Mag. B 72, 551 (1995)]. We study the photoelectronic properties of microcrystalline silicon samples and deduce the minority carrier diffusion length. From the variation in electric field the trapped charge density, responsible for charge neutrality under illumination, can also be determined. Thus additional information is gained which can be related to the density of states in the material.
Boron Diffusion and Silicon Self-Interstitial Recycling between SiGeC layers
Authors: Carroll M. S. , Sturm J. C. 
Published: April 2011

ABSTRACTSubstitutional carbon is known to locally reduce silicon self-interstitial concentrations and act as a barrier to self-interstitial migration through the carbon rich regions. A silicon spacer between two carbon rich SiGe layers is fabricated in this work to examine self-interstitial generation in a region that is isolated from self-interstitial formation at the surface or in the silicon bulk. Boron marker layers above, below and in between two SiGeC layers are used to monitor the self-interstitial concentration between the substitutional carbon. No evidence of self- interstitial depletion in the silicon spacer is observed, despite annealing in conditions believed sufficient to allow the self-interstitials to reach and react with surrounding substitutional carbon. Simulations of the self-interstitial and carbon indicate that the silicon self interstitial concentration in the spacer layer can be sustained in part due to a silicon self-interstitial recycling process through a reverse “kick-out” reaction.
Suppression of Ni Silicide Formation by Se Passivation of Si(001)
Authors: Shanmugam Janadass , Coviello Michael , Udeshi Darshak , Kirk Wiley P. , Nano Meng Tao 
Published: April 2011

ABSTRACTValence mending of a semiconductor surface, such as the Se-passivated Si(001) surface, improves the chemical and thermal stability of the surface as compared to the bare Si(001) surface. In this paper, we report the suppression of Ni silicide formation between Ni and Si(001) through monolayer passivation of Si(001) by Se. Ni was deposited on both Se-passivated and bare Si(001) surfaces. The samples were annealed at temperatures from 400°C to 700°C. Cross-sectional TEM (Transmission Electron Microscopy) revealed that Ni on bare samples reacted with Si at 400°C and formed silicide, whereas Ni on Se-passivated samples did not react with Si at 500°C. Surface composition analysis by XPS (X-Ray Photoelectron Spectroscopy) showed pure Ni surface on Se-passivated samples annealed at 400°C and 500°C, but silicide surface on bare samples annealed at the same temperatures. Hence, Se passivation suppresses the formation of Ni silicide on the Si(001) surface by over 100°C as compared to the bare Si(001) surface. These results may have important implications in source/drain engineering in sub-100 nm Si CMOS (Complementary Metal Oxide Semiconductor) devices.
The Use of SiGe Barriers During the Formation of p+ Shallow Junctions by Ion Implantation
Authors: Thompson Phillip E. , Bennett Joe , Felch Susan 
Published: April 2011

ABSTRACTUltra-shallow p+ junctions are required for next generation electronics. We present a technique for the formation of ultra-shallow p+ junctions that increases the thermal stability of the junctions formed by ion implantation. By using a 10 nm Si1−xGex barrier layer, the diffusion of B is inhibited during high temperature processes. Alloys having a composition from x = 0 to 0.4 were investigated and it is shown that the most effective barrier had the maximum Ge fraction. The junction depth decreased to 36.7 nm for a 5×1015/cm2 1kV BF3 plasma implant spike annealed at 1050°C, compared to a junction depth of 48 nm for a Si control sample having the identical implant and anneal. It is hypothesized that the inhibition of B diffusion in the alloy layer is caused by a reduction of the Si self-interstitials in the alloy.
Lattice strain and composition of Boron-Interstitial Clusters in Crystalline Silicon
Authors: Salvador D. De , Bisognin G. , Napolitani E. , Aldegheri L. , Drigo A.V. , Carnera A. , Mirabella S. , Bruno E. , Impellizzeri G. , Priolo F. 
Published: April 2011

ABSTRACTIn this work we have investigated the average composition of Boron Interstitials Clusters (BICs) and the strain induced in the Si crystal by BICs. We have formed BICs by Si implantation and subsequent annealing of two Si samples, grown by molecular beam epitaxy, containing thin buried layers doped with different B concentrations (1019 and 1020at/cm3). By B chemical profiles diffusion analysis, we have extracted the doses of Si self-interstitials (I) and Boron atoms trapped at the BICs. The B/I stoichiometric ratio is about 1 for the low B concentration and about 3.5 for the high B concentration sample. High-resolution x-ray diffraction analyses provided an estimate of strain profile. While in the low B concentration sample no appreciable strain was detected after BIC formation, at the higher B concentration we found that the tensile strain present in the as grown B doped layer changes to a strong compressive strain as a consequence of BICs formation. For this kind of clusters, the mean volume expansion with respect to the Si matrix is of (29 ± 6) Å3 for each B atom trapped at the BICs.
Effect of Annealing on the Structural, Mechanical and Tribological Properties of Electroplated Cu Thin Films
Authors: Shukla P. , Sikder A. K. , Zantye P.B. , Kumar Ashok , Sanganaria M. 
Published: April 2011

AbstractThe increasing demand for faster and more reliable integrated circuits (ICs) has promoted the integration of Copper-based metallization. Electroplated Cu films demonstrate a microstructural transition at room temperature, known as self annealing. In this paper we intend to investigate the annealing behavior of electroplated Cu films grown on a seed Cu layer on top of the barrier layers over a single crystal silicon substrate. All the samples were undergone through a multistep annealing process. Grazing incident x-ray diffraction pattern shows stronger x-ray reflections from Cu (111) and (220) planes but weaker reflections from (200), (311) and (222) planes in all the electroplated Cu samples. Transmission electron microscopy was performed on the cross section of the samples and the diffraction pattern showed the crystalline behavior of both seed layer and electroplated Cu. Nanoindentation was performed on all the samples using the continuous stiffness measurement (CSM) technique and it was found that the elastic modulus varies from 110 to 130 GPa while the hardness varies from 1 to 1.6 GPa depending on the annealing conditions. The tribological properties of all the copper films were also measured using the Bench Top CMP tester. Subsequently, Nanoindentation was performed on the samples after polishing the top surface in order to investigate the work hardening and an increase in hardness and modulus was observed. Finite Element Modeling was performed in order to investigate the stress behavior during nanoindentation.