bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication of two-dimensional Si/Ge nanowires and nanorings
Authors: Kawamura Midori , Voigtländer Bert , Paul Neelima , Cherepanov Vasily 
Published: April 2011

ABSTRACTWe show that two-dimensional Si/Ge nanostructures with a thickness of a single atomic layer can be imaged with chemical sensitivity using a scanning tunneling microscope (STM). An atomic layer of Bi terminating the surface is used to distinguish between Si and Ge. This distinction between Si and Ge enabled us to fabricate two-dimensional Si/Ge nanostructures in a controlled way by self-organized growth. Si/Ge nanoring structures consisting of alternating Si and Ge rings having a width of ∼5 nm were grown around a Si core on a Si(111) substrate by molecular beam epitaxy (MBE). The thickness of the Si and Ge rings is only one atomic layer (0.3 nm). Alternating Si/Ge nanowires with a width of ∼3.5 nm and a thickness of 0.3 nm were also fabricated using alternating Si/Ge deposition in the step flow growth mode.
Epitaxial Metallic Islands: Charge Confinement And Templates For Atomic Wires
Authors: Mazzone A.M. , Savini G.L. 
Published: April 2011

ABSTRACTHartree-Fock calculations at semiempirical level, using the Extended Debey-Hückel Approximation, and LDA with pseudopotentials are used to investigate the properties of homoepitaxial islands formed by Cu and Ag. The islands have a three-dimensional shape and the dimensions of their height and basis are in the range of the bulk Fermi wavelength. Linear chains of Ag and Cu atoms are deposited on the island steps. The calculations describe the binding action of the island on the chain as well as the allowed energies and the density of states of the complete system. The results indicate that, due to the corrugation of the potential at the island-substrate interface, the more stable chain configurations are the ones near the island top rather than at its basis. Furthermore at these small sizes the island steps act as weak and permeable barriers. In fact, the electronic charge retains bulk-like features, though traces of quantum confinement can be identified.
Microscopic theory of electromagnetic energy transport in nanostructured media
Authors: Xue Yongqiang , Ratner Mark A. 
Published: April 2011

ABSTRACTWe present a microscopic theory of electromagnetic energy transport in nanostructured media based on the Lagrangian formulation of semiclassical electrodynamics. We show the importance of the interplay between transverse and longitudinal local fields in determining the light-matter interaction in nanostructured media. We derive rigorously the coupled-dipole equation of the local fields and apply the theory to analyze energy transport in metal nanoparticle chain waveguide.
In-situ TEM Study of the Crystallization of Thin Films composed of Sb3.6Te with Ge
Authors: Kooi Bart J. , Groot Willemijn M.G. , De Hosson Jeff Th.M. 
Published: April 2011

ABSTRACTThis paper addresses the crystallization of amorphous Sb3.6Te films (40 nm thick) and 5 at.% Ge containing Sb3.6Te films (10, 20 and 40 nm thick) as studied using in-situ annealing in a Transmission Electron Microscope (TEM). These materials show growth-dominated crystallization, in contrast to Ge2Sb2Te5 that shows nucleation-dominated crystallization. Particularly the crystal-growth velocity in these systems is measured as a function of temperature from which the activation energy for growth can be derived. The strong effect of the 5 at.% Ge addition on the total crystallization behavior is revealed: Ge increases the crystallization temperature (from 95 to 150 °C), increases the activation energy for growth (from 1.58 to 2.37 eV), increases the nucleation rate and decreases the growth anisotropy.
Modeling InSe Phase-change Materials
Authors: Kohary K. , Burlakov V. M. , Nguyen-Manh D. , Pettifor D. G. 
Published: April 2011

ABSTRACTThe amorphous structure of InxSey has been studied by a first principles tight-binding molecular dynamics technique using the program package PLATO (Package for Linear-combination of Atomic Type Orbitals). The three-dimensional amorphous structures with different densities were prepared by quick quenching from the liquid phase. The characteristics of short-range order such as coordination numbers, radial and bond angle distributions, and ring statistics have been analyzed.
Thermodynamic Properties of Pu-O-H Compounds and Alloys from Density Functional Theory
Authors: Korzhavyi P. A. , Vitos L. , Johansson B. 
Published: April 2011

ABSTRACTA theoretical approach has been developed that allows one to obtain thermodynamic properties of plutonium-based alloys and compounds from first-principles electronic structure calculations based on density functional theory. The approach is applied to study the defect structure in non-stoichiometric PuO2±δ.
Iron – Phosphate Glass (IPG) Waste Forms Produced using Induction Melter with Cold Crucible
Authors: Aloy A.S , Soshnikov R. A. , Trofimenko A. V. , Gombert D. , Day D. , Kim C. W. 
Published: April 2011

ABSTRACTA simulated sodium bearing waste (SBW), which represented a type of high sodium and sulfate waste, was successfully vitrified in iron phosphate glasses (IPG), at a maximum waste loading of 40 wt%, using a cold crucible induction melter (CCIM). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that all of the IPG waste forms did not contain sulfate salt segregation or crystalline phases. The calculated composition and the average analytical composition obtained by Electron Probe Microanalysis (EPMA) were in good agreement. The major elements were uniformly distributed throughout the samples. The chemical durability of the IPG waste forms containing 40wt% SBW was evaluated by the product consistency test (PCT) and met current DOE requirements. IPG waste forms were melted at a relatively low temperature and for short times compared to borosilicate glasses. These advantages, combined with those of a significantly higher waste loading and the feasibility for CCIM melting, offer a considerable savings in time, energy, and cost for vitrifying this high sodium and sulfate waste.
Development Of A Glass-Encapsulated Ceramic Wasteform For The Immobilization Of Chloride-Containing ILW
Authors: Metcalfe Brian L. , Fong Shirley K. , Donald Ian W. 
Published: April 2011

ABSTRACTPyrochemical reprocessing of plutonium generates several ILW waste-streams and a simple process has been developed at AWE to immobilize the chloride and actinide ions present in one of these waste-streams (Type 1) by calcining the waste with calcium phosphate. We have now investigated the possibility of using this process as the basis for treating a more complex waste-stream (Type 2) and have determined that with some minor modification the original process can effectively immobilize the greater range of cations present in Type 2 waste to again produce a free-flowing non-hygroscopic powder. Weight for weight replacement of the Type 1 waste by Type 2 produced a powder which was approximately 20% deficient in PO43- when compared with stoichiometric powder. Addition of phosphorus pentoxide to the simulant waste/calcium phosphate powder mixture prior to calcination to produce stoichiometric powder significantly improved the chloride ion uptake. In order to comply with safety requirements it is necessary to convert the free-flowing powder into a monolithic wasteform suitable for long term storage. Conversion of the powder to a monolithic wasteform by sintering using a sodium aluminophosphate glass as a binder has been investigated and has proved successful, but to achieve high densities it has been necessary to cold press the samples prior to sintering.
Structural Studies of Hollandite-Based Radioactive Waste Forms
Authors: Whittle K. R. , Ashbrook S. E. , Redfern S.A.T. , Lumpkin G. R. , Attfield J. P. , Dove M. , Farnan I. 
Published: April 2011

ABSTRACTHollandites with compositions Ba1.2-xCsxMg1.2-x/2Ti6.8+x/2 O16, and Ba1.2-xCsxAl2.4-xTi5.6+xO16 (x=0, 0.1, 0.25) have been synthesised using a modified alkoxide/acetate precursor route. The samples have been sintered using two procedures; hot isostatic pressing and sintering at ambient pressure. X-ray powder diffraction has shown samples from both systems to form tetragonal hollandites, with little change when pressed by both methods. Cs-133 MAS NMR spectra have been recorded showing the chemical shift in Al containing samples to be ∼250ppm, and in Mg hollandites ∼175ppm and 200ppm, with little change when prepared by both methods.
Zeolite - Salt Occlusion: A Potential Route for the Immobilisation of Iodine-129?
Authors: Hyatt Neil C. , Hriljac Joseph A. , Choudhry Alia , Malpass Laura , Sheppard Gareth P. , Maddrell Ewan R. 
Published: April 2011

ABSTRACTReactions of zeolite Na-A with AgI, and the sodium, copper and lead forms of zeolites A, LTA, X and Y with NaI, have been examined as possible starting routes to the long term immobilisation of iodine-129. Heating the salts in air, at 500°C, with the sodium forms of the zeolites leads to the formation of occlusion products, where the iodide salt migrates into the zeolite pores. Detailed studies of the Na-A / 5AgI complex indicate it has a uniform distribution of Na, Si, Al, Ag and I, and is thermally stable to ca. 750°C, where there is a substantial weight loss as iodine is released. In situ powder X-ray diffraction studies have been used to monitor the occlusion reaction at 400°C, and show that the occlusion product decomposes to produce a single crystalline phase at 800°C prior to further decomposition at 850°C to a mixture of nepheline and elemental silver.
Thermodynamic Modeling and Sensitivity Analysis of Kd Values for Radionuclide Migration in Sedimentary Host Rocks
Authors: Talerico Caterina , Ochs Michael , Ueta Shinzo , Sasaki Noriyuki 
Published: April 2011

ABSTRACTThe effects of key geochemical parameters on Kd values for radionuclides in the host rock (pumice, sandstone) of a LLW repository were elucidated through a sensitivity analysis, using a thermodynamic speciation/sorption model for the elements Sr and Ni. The complex mineral assemblage of the rock was approximated by a component-additivity approach. Using published ion exchange and surface complexation parameters, Kd for both Sr and Ni could be well explained by the same model mineralogy and surface chemistry. Model results suggest that pCO2 can have a significant effect on Kd, and that a correct approximation of groundwater chemistry is a critical component of sorption modeling.
Smectite Dissolution Kinetics in High-Alkaline Conditions
Authors: Ohmoto Hiroshi , Spangler Kathryn R. , Watanabe Yumiko , Kamei Gento 
Published: April 2011

ABSTRACTTo determine the initial rates and effects of silica in solution on the dissolution kinetics of smectite, short- and long-term batch experiments (0.5 hour to 30 days) were completed at three temperatures (T = 25, 50, and 75°C) using stock solutions pH adjusted by NaOH (pH = 12, 13, and 13.5) with varying initial silica concentrations (0, 30, 60, and 100 ppm). The following important characteristics were observed at pH = 12: (1) The concentrations of Al, Si, Mg, Fe, and Ti in solutions increase rapidly during the first ∼2 hours and reach steady state (equilibrium) within ∼5 days. (2) The concentration ratios of Al, Si, Fe, Mg, and Ti in solutions during the early (<2 hours) reaction phase differ significantly from those of smectite, indicating initial dissolution proceeds non-stoichiometrically; Al dissolves much faster than Si, Mg, Fe, and Ti. (3) Further dissolution of smectite proceeds nearly stoichiometrically, including Fe and Ti. (4) The high solubility of Ti in highly alkaline solutions may be due to the formation of aqueous complexes, such as TiO(OH)3− and TiO2(OH)22−, similar to aqueous silica species. (5) The initial rate of smectite dissolution increases with increasing pH, T, and initial silica content of solution. (6) The silica in solution acts as a promoter and a catalyst, rather than an inhibitor, of smectite dissolution in high-alkaline solutions. This role is easily recognizable when the solubility of smectite and amorphous silica are very high, i.e., at pH >∼9.
Reactive Transport Modeling of Radionuclide Source-Terms in an Underground Spent Fuel Disposal
Authors: De Windt L. , Catalette H. , Gras J. M. 
Published: April 2011

ABSTRACTThe reactive transport model HYTEC was used to simulate the migration over 100,000 years of cesium, americium and uranium released from spent fuel packages in the near-field components of an underground stiff clay disposal site. A global equilibrium thermodynamic approach including kinetic control of the spent fuel pellets was used with instantaneous release fractions and congruent dissolutions of the rim and the core zones. A failure scenario of the waste package after 10,000 years was considered with magnetite as the main corrosion product. The retention properties of magnetite and the different effects of bentonite and cementitious backfill materials were specifically analysed.
Geochemical Indicators of Groundwater Stability
Authors: Bath Adrian , Strömberg Bo 
Published: April 2011

ABSTRACTThe interpretation of geochemical and isotopic data as indicators of past hydrodynamic stability of groundwaters in fractured rock is discussed. Knowledge of the conditions and timing of past groundwater stability supports scenarios for safety assessments. Stratification of water masses according to densities is an important factor affecting stability. Chloride variations and concentration gradients are therefore diagnostic of mixing and the duration of stable conditions. Further evidence of timescales is provided by carbon-14 and tritium data although sampling difficulties and other uncertainties may allow only qualitative interpretations. Data from Äspö and other Swedish sites, Sellafield (UK) and Olkiluoto (Finland) are used to illustrate the approach. The palaeohydrogeology of such sites has been strongly influenced by distributions of saline waters. Scenarios for groundwater stability should consider these as well as glacial melt waters.
Study on Unearthed Bronzes Relics of Xizhou Dynasty, China
Authors: Zhangru Chen , Zhijian Wen , Guang Fan , Yuemiao Liu 
Published: April 2011

ABSTRACTEngineered barrier for HLW repository is composed of the waste form, the canister and the buffer/backfill material. Assessment of the applicability of metal as candidate materials of canister for HLW has been conducted in some countries. Many bronze relics from the XiZhou Dynasty, China, dated from more than 3,000 years ago, have been preserved perfectly. The study on the corrosion of the bronze relics could contribute to the material selection and design of canisters for HLW. The corrosion products of ancient bronzes consist of copper carbonate hydrate, lead carbonate, copper oxides etc. The corrosion mechanism of the substrate was mainly characterized by electrochemical corrosion, whereas the corrosion mechanism of surface layers was characterized by direct chemical corrosion and electrochemical corrosion.
Granite Recrystallization - The Key to an Alternative Strategy for HLW Disposal?
Authors: Gibb Fergus G. F. 
Published: April 2011

ABSTRACTAn alternative strategy is proposed for the disposal of spent nuclear fuel (SNF) and other forms of high-level waste (HLW) whereby the integrity of a mined and engineered repository for the bulk of the waste need be preserved for only a few thousand years. This is achieved by separating the particularly problematic components, notably heat generating radionuclides (HGRs) and very long lived radionuclides (VLLRs) from the waste prior to disposal. Such a solution requires a satisfactory means of disposing of the relatively minor amounts of HGRs and VLLRs removed from the waste. This could be by high-temperature very deep disposal (HTVDD) in boreholes in the continental crust [1,2]. However, the viability of HTVDD, and hence the key to the entire strategy, depends on whether sufficient melting of granite host rock can occur at suitable temperatures and whether the melt can be completely recrystallized. The high-temperature, high-pressure experiments reported here demonstrate that granite can be partially melted and completely recrystallized on a time scale of years, as opposed to millennia as widely believed. Furthermore, both can be achieved at temperatures and on a time scale appropriate to the disposal of packages of heat generating HLW. It is therefore concluded that the proposed strategy, which offers, environmental, safety and economic benefits, could be a viable option for a substantial proportion of HLWs.
Vertically Integrated Amorphous Silicon Particle Sensors
Authors: Wyrsch N. , Miazza C. , Dunand S. , Shah A. , Moraes D. , Anelli G. , Despeisse M. , Jarron P. , Dissertori G. , Viertel G. 
Published: April 2011

ABSTRACTVertically integrated particle sensors have been developed using thin-film on ASIC technology. Hydrogenated amorphous silicon n-i-p diodes have been optimized for particle detection. These devices were first deposited on glass substrates to optimize the material properties and the dark current of very thick diodes (with thickness up to 50 m). Corresponding diodes were later directly deposited on two types of CMOS readout chips. These vertically integrated particle sensors were tested in beta particle beam from 63Ni and 90Sr sources. Detection of single low- and high- energy beta particle was achieved.
Solar Cells on Foreign Substrates Using Poly-Si Thin Films by Metal Induced Growth
Authors: Ji Chunhai , Anderson Wayne A. 
Published: April 2011

ABSTRACTThe poly-Si film was deposited by using the metal-induced growth (MIG) method on tungsten substrates. By making Au/n-Si Schottky photo-diodes, doping density effect was studied by using three different doping level Si sputtering targets. Increasing the Si target resistivities from 0.02Ω-cm to 50Ω-cm, open-circuit-voltage (Voc) decreased from 0.22V to 0.14V while short-circuit-current density (Jsc) increased from 1.55mA/cm2 to 2.42mA/cm2. C-V results revealed a high charge density in the device, which may be due to the oxygen thermal donor effects. Using an oxygen filter for the sputtering gas effectively reduced the charge densities and increased the Jsc value. The p/n junction solar cells were fabricated by using ion implantation at 1013∼1014cm−2 dose and 100∼200keV. The cells with wider emitter layer by double-ion implantation gave higher Jsc and Voc values. Passivation of the Si film by using hydrogenation improved the Jsc, Voc and spectral response of the solar cells.
Development of a Porous Silicon Product for Small Molecule Mass Spectrometry
Authors: Credo Grace , Hewitson Hillary , Benevides Christopher , Bouvier Edouard S. P. 
Published: April 2011

ABSTRACTPrevious work has demonstrated the utility of desorption/ionization on silicon (DIOS) time-of-flight mass spectrometry (TOFMS) in drug molecule and peptide detection[1-7]. In this work, the utility of DIOS for small molecule detection is established using commercially available porous silicon (por Si)-based target plates for MS. Since the morphology and handling of the substrates can have dramatic effects on the MS characteristics, the development of consistent manufacturing methods and characterization protocols has been central to the production of reproducible target plates[7]. Using sample substrates manufactured in-house, we show that 1) small molecules and protein digests were detected without matrix-related peaks, 2) por Si morphology was optimized for small molecule detection, 3) reproducible DIOS plates were produced, 4) although the target plates were shown to be sensitive to contamination, a consistent cleaning procedure was developed to remove contaminants, and 5) stability and shelf life were characterized as a function of surface derivatization. Dynamic range, sensitivity, quantitation, speed of analysis, solution composition, and automated deposition have also been evaluated and are described in related work[7-9]. Potential applications include high-throughput small molecule assays for drug discovery[10a] and high sensitivity (sub-femtomole) peptide identification for proteomics[10b].
Excimer-Laser Growth of Si Large-Grain Arrays
Authors: Matsumura Masakiyo 
Published: April 2011

ABSTRACTAmorphous silicon (a-Si) Thin Film Transistors (TFT) will continue to play an important role in large-area liquid crystal displays (LCD), however, there is also a strong demand for ultra-high performance TFTs aimed at intelligent small (or medium) size displays. For this reason, “Crystal Si on glass” has become an increasingly attractive solution. This paper reviews recent work performed at ALTEDEC (Advanced LCD Technologies Development Center Co., Ltd, with regard to growing an array of large Si grains at low temperature. The results obtained so far indicate that satisfactory progress has been made towards the achievement of this goal.
Electronic Properties of RF Glow Discharge Intrinsic Microcrystalline Silicon near the Amorphous Silicon Phase Boundary
Authors: Gutierrez James J. , Halverson Adam F. , Tweeten Eric D. , Cohen J. David , Yan Baojie , Yang Jeffrey C. , Guha Subhendu 
Published: April 2011

ABSTRACTThe electronic properties of microcrystalline silicon have been characterized for the first time using transient photocapacitance spectroscopy (TPC) and drive-level capacitance profiling (DLCP). These methods were applied to microcrystalline films deposited by the RF glow discharge method at United Solar. The DLCP method allowed the shallow doping density to be profiled and the deep defect densities to be estimated. The TPC spectra were found to reveal that both a microcrystalline as well as an amorphous component are present in these samples. By varying the measurement temperature for these TPC spectra we were also able to directly monitor the degree of minority carrier collection in these films. Significant effects due to light soaking on the TPC spectral properties were also observed.
Surface Potential and Surface Photovoltage of Oxide and Nitride coated multicrystalline Silicon Solar Cells using a Scanning Kelvin Probe
Authors: Baikie Iain D. 
Published: April 2011

ABSTRACTWe have applied a high resolution scanning Kelvin probe to perform dark surface potential topographies of multicrystalline silicon solar cells having thin coatings of Si3N4 and SiO2. We clearly observe the electrical characteristics of the screen printed bus-bar and associated fingers, grain boundaries, together with characteristic structures on the oxide and nitride, coupled to significant surface potential variations across larger sections of the wafer. Associated surface photovoltage measurements can be unambiguously decoded to show coating and bulk contributions. The nitride coating exhibits carrier trapping lifetimes in excess of 13 minutes at 300K.
New ultrahigh vacuum setup and advanced diagnostic techniques for studying a-Si:H film growth by radical beams
Authors: Hoefnagels J.P.M. , Langereis E. , Sanden M.C.M. van de , Kessels W.M.M. 
Published: April 2011

ABSTRACTA new ultrahigh vacuum setup is presented which is designed for studying the surface science aspects of a-Si:H film growth using various advanced optical diagnostic techniques. The setup is equipped with plasma and radical sources which produce well-defined radicals beams such that the a-Si:H deposition process can be mimicked. In this paper the initial experiments with respect to deposition of a-Si:H using a hot wire source and etching of a-Si:H by atomic hydrogen are presented. These processes are monitored by real time spectroscopic ellipsometry and the etch yield of Si by atomic hydrogen is quantified to be 0.005±0.002 Si atoms per incoming H atom.