bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Cluster Ion Beam Processing of GaSb and InSb Surfaces
Authors: Krishnaswami K. , Vangala S.R. , Krejca B. , Allen L.P. , Santeufemio C. , Dauplaise H. , Liu X. , Whitten J. , Ospina M. , Sung C. , Bliss D. , Goodhue W.D. 
Published: April 2011

ABSTRACTGas Cluster Ion Beam (GCIB) processing has recently emerged as a novel surface smoothing technique to improve the finish of chemical-mechanical polished (CMP) GaSb (100) and InSb (111) wafers. This technique is capable of improving the smoothness CMP surfaces and simultaneously producing a thin desorbable oxide layer for molecular beam epitaxial growth. By implementing recipes with specific gas mixtures, cluster energy sequences, and doses, an engineered oxide can be produced. Using GaSb wafers with a high quality CMP finish, we have demonstrated surface smoothing of GaSb by reducing the average roughness from 2.8Å to 1.7Å using a dual energy CF4/O2-GCIB process with a total charge fluence of 4×1015ions/cm2. For the first time, a GCIB grown oxide layer that is comprised of mostly gallium oxides which desorbed at 530°C in our molecular beam epitaxy system is reported, after which GaSb/AlGaSb epilayers have been successfully grown. Using InSb, we successfully demonstrated substrate smoothing by reducing the average roughness from 2.5Å to 1.6Å using a triple energy O2-GCIB process with a charge fluence 9×1015ions/cm2. In order to further demonstrate the ability of GCIB to smooth InSb surfaces, sharp ∼900nm high tips have been formed on a poorly mechanically polished InSb (111)A wafer and subsequently reduced to a height of ∼100nm, an improvement by a factor of eight, using a triple energy SF6/O2-GCIB process with a total charge fluence of 6×1016ions/cm3.
Influence of High-Fluence Proton Irradiation on the Optical Absorption and Microstructure of Rutile
Authors: Lu Tiecheng , Zhu Sha , Wang Lumin 
Published: April 2011

ABSTRACTRutile (TiO2) single crystals of (110) or (001) orientation were irradiated by high fluence protons with the energy of 0.5, 4.9 and 18 MeV and with the fluence of 1×1018 and 1.9×1022 m-2. UV-VIS-IR, LRS and HRTEM were used to analyze the optical absorption and microstructure of samples. The UV-VIS-IR results showed that proton irradiation induces two absorption peaks centered at 760 and 1700 nm respectively, even high fluence irradiation induces absorption plateau at 600∼2500 nm. LRS results showed that the related intensity of common vibration modes is different for different planes. Proton irradiation induces the vibration frequency and related intensity change for inherent LRS modes, and several new vibration modes also appear. High fluence proton irradiation induced large defect clusters, i.e. stacking faults, which is demonstrated by HRTEM observation. The optical absorption mechanism also has been discussed.
Influence of Hydrogen Plasma Treatment on He Implantation-Induced Nanocavities in Silicon
Authors: Vengurlekar A. , Ashok S. , Liu C. L. , Ntsoenzok E. , Barthe M. F. , Desgardin P. , Ruault M. O. 
Published: April 2011

ABSTRACTHe implantation followed by thermal anneal is a well-established technique for creating layers or bands of cavities in silicon. This process is a consequence of the interaction between He and ion-implant-induced vacancies. Applications of such cavity layers include gettering and localized minority carrier lifetime control, and compliant substrates for lattice-mismatched heteroepitaxy. Studies have shown that the presence of interstitial-type defects can lead to the shrinkage of He-cavities due to the interstitial capture by the cavities. However, few of them deal with the interaction of cavities with vacancies. Here we present results on the formation of He-cavities in Si in the presence of atomic hydrogen and vacancies produced by effusion of hydrogen. Following a helium implant, samples were hydrogenated with an electron cyclotron resonance (ECR) hydrogen plasma. Control samples without any hydrogenation were also used. We studied the influence of hydrogen on void morphology. While hydrogen enhances void size at higher energy implants, the enhancement effect is absent in lower energy implants. The results underscore the role of vacancies in void formation and growth.
The Origin of Radiation Resistance of Magnesium Aluminate Spinel
Authors: Gritsyna Vasyl T. , Kazarinov Yurij G. , Kobyakov Volodymyr A. , Sickafus Kurt E. 
Published: April 2011

ABSTRACTWe propose here a new mechanism to explain the observed high radiation tolerance of magnesium aluminate compounds with crystal structures known as spinel. By using optical methods, we found that the kinetics of accumulation of optical absorption centers under different types of irradiation, as well as the kinetics of absorption decay after termination of irradiation, along with radio-luminescence processes, are consistent with a new model regarding defects and radiation damage in spinel. This model assumes the existence of spatially-correlated antisite defects in the form of dipoles: (Al3+tet)+-(Mg2+oct)-. These spatially-correlated point defect complexes serve as centers for annihilation of radiation-induced cation Frenkel pairs. In addition to the spatially-correlated defects, the high concentration of cation structural vacancies inherent to the spinel lattice also serves to promote high mobility of both Mg and Al interstitial species. This enhanced mobility leads to increased probability of annihilation at the dipole centers proposed in this model. Such annihilation then diminishes the probability for formation of defect clusters, dislocation loops, or amorphization of the irrradiated spinel.
Structural Disordering in Magnesium Aluminate Spinel Compounds under Ion-Beam Irradiation
Authors: Matsumura Syo , Shimada Mikio , Yasuda Kazuhiro , Kinoshita Chiken 
Published: April 2011

ABSTRACTHigh Angular Resolution Electron Channeling X-ray Spectroscopy (HARECXS) of analytical electron microscopy was employed in quantitative analysis of irradiation-induced structural disordering in MgO·n Al2O3 spinel compounds irradiated with 1 MeV Ne+ ions and 200 MeV Xe14+ ions. The results successfully show the disordering behavior in MgO·n Al2O3 as a function of composition and irradiation condition. It has been revealed by HARECXS that 1 MeV Ne+ irradiation at 873 K causes significant cation-disordering in the pre-peak damaged area where no indication is recognized in conventional TEM observation. Displacement of O2- ions is also recognized in heavily damaged areas. Irradiation with 200 MeV Xe14+ swift ions, on the other hand, forms structurally-disordered cylinders of 4 nm in diameter along their tracks. HARECXS profiles indicate that the disordering takes place over extended areas of about 10 nm in radius centered on the ion tracks.
Low-Energy Ne+ Ion Channeling and Implantation into Cu(100) and Cu3Au(100)
Authors: Rasulov Akbarali M. , Dzhurakhalov Abdurauf A. 
Published: April 2011

ABSTRACTBy computer simulation details have been observed regarding the dynamics of the change of the character of trajectories, the range and energy losses of channeled ions, as well as the angular and energy distributions of ions transmitted through thin crystal versus the composition of single crystal, the impact parameters from the center of the channel and the initial energy. It has been established that for a paraxial part of a channeled beam the inelastic energy losses comprise the main loss of energy. The elastic energy losses of the channeling ions in the case of Cu3Au(100) crystal are larger than in the case of Cu(100). As Au atoms are heavier than Cu atoms, in the case of Cu3Au(100) the degree of the dechanneling of particles is greater and the range is smaller in comparison with the similar characteristics for Cu(100).
Pit nucleation in compound semiconductor thin films
Authors: Bouville Mathieu , Falk Michael L. , Millunchick Joanna Mirecki 
Published: April 2011

ABSTRACTPit nucleation has been observed in a variety of semiconductor thin films. We present a model in which pit nucleation is considered to arise from a near-equilibrium nucleation process in which the adatom concentration plays an important role. Although pits relieve elastic energy more efficiently than islands, pit nucleation is prevented if the adatom concentration is too high. Inhomogeneities in the adatom density on the surface due to three-dimensional islands enhance pit nucleation. Thermodynamic considerations predict several different growth regimes in which pits may nucleate at different stages of growth depending on the materials system and growth conditions. However kinetics must be taken into account to make direct comparisons to experimental observations. These comparisons show good agreement given the uncertainties in quantifying experimental parameters such as the surface energy.
Effects of clustering and dimensionality on the magnetic properties of diluted magnetic semiconductors
Authors: Bhatt R. N. , Kennett Malcolm. P. , Kassaian Adel 
Published: April 2011

ABSTRACTThe magnetic properties of films of diluted magnetic semiconductors (DMS) such as (Ga,Mn)As, as well as bulk grown crystals of similar materials, have been found to be extremely sensitive to growth conditions, both in terms of the ferromagnetic transition temperature, and the details of their magnetization curves. We study an impurity band model for carriers in Mn-doped DMS applicable in the low carrier density regime, and discuss the effects of clustering on the magnetic properties of DMS, using both numerical mean field and Monte Carlo simulations. In addition, we study the effects of dimensionality on the transition temperature and other magnetic behaviour, and compare our results with experimental data.
Aperiodic lattices for photonic bandgap engineering
Authors: Chakraborty Subhasish , Hasko David G. , Mears Robert. J. 
Published: April 2011

ABSTRACTA new method is presented, based on the discrete Fourier Transform, for the design of aperiodic lattices to be used in photonic bandgap engineering. Designing an aperiodic lattice by randomly choosing defects is unlikely to result in useful optical transmission characteristics. By contrast, this new method allows an aperiodic lattice to be designed directly from the desired optical characteristic. The use of this method is illustrated with a design for a structure to realise two transmission wavelengths in the stopband of a one-dimensional photonic lattice. This design has been fabricated in silicon-on-insulator and some optical characteristics are given.
Quantifying Field-Induced Contrast Effects in Photoelectron Emission Microscopy
Authors: Siegrist K. , Ballarotto V. W. , Williams E. D. 
Published: April 2011

ABSTRACTSamples consisting of electrically isolated titanium lines fabricated on a titanium surface were used to quantify voltage-induced contrast effects in photoelectron emission microscopy (PEEM). Induced contrast effects were observed to extend 6 μm for a -5 V bias applied to a 303 nm tall raised line. We therefore explored, via numerical calculation, the spatial extent of the perturbation to the PEEM accelerating field caused by the bias applied across the step height. The intensity full width at half minimum agreed well with the calculated width defined by the 10% level of lateral field strength. For a line 550 nm tall, a correspondence was found for a calculated width defined by a 5% lateral field strength. It was observed that neighboring structures a few μm away affected the image contrast, for sufficiently strong applied bias. This suggests that effects can easily be induced at distances of 0.5 μm for modest applied voltages, as has been previously observed for structures buried under oxide layers 0.5 μm thick [1].
Femtosecond Laser-induced Crystallization in As-deposited Ge1Sb2Te4 Films
Authors: Wang Qin F. , Shi Lu P. , Huang Su M. , Miao Xiang S. , Wong Kai P. , Chong Tow C. 
Published: April 2011

ABSTRACTTime resolved imaging has been used to investigate the whole process of the crystallization induced by intense 130 femtosecond laser pulses in as-deposited Ge1Sb2Te4 films. With an average fluence of 24mJ/cm2 a transient non-equilibrium state of the excited material is formed within 1 picosecond. The results are consistent with an electronically induced non-thermal phase transition.
Multi Layer Disk Design For Near Field Phase-Change Recording
Authors: Kishima Koichiro , Ichimura Isao , Saito Kimihiro , Yamamoto Kenji , Iida Atsushi , Osato Kiyoshi 
Published: April 2011

ABSTRACTWe propose multi-layer near-field recording with using inner focus mode. The restricted conditions for multi-layer near-field recording are discussed from the viewpoint of both media structure and optical setup. One solution is presented for dual layer recording with a numerical aperture (NA) of 1.5 and a wavelength of 405 nm as a light source of GaN laser diode.In the proposed layer structure, a Nb2O5 material has been adopted as the intermediate layer because of its high refractive index, n = 2.4, in order to prevent the decrease of beam propagation that corresponds to NA>1. Almost the same signal characteristics can be obtained from both recording layers at the air gap of 40 nm. The adjustment of focusing position and the compensation of spherical aberrations have been implemented by the combination of an expander lens unit and a liquid crystal (LC) panel in the optical setup.
Microstructure and Chemistry of an Aluminophosphate Glass Waste Form under Electron Beam Irradiation
Authors: Sun K. , Wang L. M. , Ewing R. C. 
Published: April 2011

ABSTRACTAn alkali-containing (mainly sodium) aluminophosphate glass waste form was studied by analytical electron microscopy. Bright-field imaging showed that small bubbles formed under the electron irradiation even at a low electron dose (8×1022e/m2). These bubbles grew with the increase of the electron dose and were finally released at the surface of the sample. At the same time alkali elements were also lost under irradiation. At an electron dose of about 2.2×1026e/m2 (6.6×1011Gy), all the bubbles were released and no bubbles were formed with further irradiation. The glass was finally transformed to a pure aluminophosphate glass. Further irradiation resulted in the phase separation between the Al-rich and the P-rich phases. The electron irradiation damage effects on the aluminophosphate glass are compared to those observed in iron phosphate glasses.
Hollandite-rich Ceramic Melts for the Immobilisation of Cs
Authors: Carter M. L. , Vance E. R. , Li H. 
Published: April 2011

ABSTRACTCeramic wasteforms designed to be processed by melting in air has been developed to immobilise Cs-rich wastes. Detailed characterisation electron microscopy is presented on versions of these melted materials which are rich in Cr-, Ni-, Zn or Co- substituted titanate hollandites and which have PCT-B normalised Cs leachate concentrations of < 0.2 g/L. To assist in understanding the general crystal chemistry of titanate hollandites, this study also investigates the solubility limits of Cs in single-phase hollandite BaxCsy(M3+)2x+yTi8–2x-yO16 where M = Cr and BaxCsy(M2+)x+y/2Ti8-x-y/2O16 formulations where M = Zn, Co or Ni.
Posiva's Site Investigations Programme
Authors: Ryhänen Veijo 
Published: April 2011

Four nuclear power plant units have been operated in Finland over 20 years. The plants are located at two sites, Olkiluoto and Loviisa. Responsibility for nuclear waste management lies on the utilities, which have established a joint company POSIVA to take care of spent fuel disposal and other expert tasks of nuclear waste management.Already in 1983 the Finnish Government set the objectives and the schedule for the national waste management programme. Since then, two shallow underground repositories have been constructed for low- and medium-level operating waste in crystalline rock at the power plant sites. At the end of 2002 the amount of operating waste emplaced in these two facilities was 4923 m3 (total accumulation 6724 m3).Spent nuclear fuel is stored in interim storage pools at the nuclear power plant sites. The total accumulation was 1228 tU at the end of 2002. Today, the main activities in nuclear waste management concern spent fuel disposal deep in the Finnish bedrock. Apart from technical and scientific issues, a major challenge faced has been the creation of sufficient public acceptance, which is a must in order to obtain favourable political decisions.
The Immobilization of Cesium and Strontium in Ceramic Materials Derived from Tungstate Sorbents
Authors: Luca Vittorio , Drabarek Elizabeth , Griffith Christopher S. , Chronis Harriet , Foy James 
Published: April 2011

ABSTRACTThe effective immobilization of Cs+ and/or Sr2+ sorbed on hexagonal tungsten oxide bronze (HTB) adsorbent materials can be achieved by heating in air at temperatures in the range 500 – 1000 °C. Crystalline powdered HTB materials formed by heating at 800 °C show leach characteristics comparable to Cs-containing hot-pressed hollandites in the pH range from 0 to 12. If the Cs-loaded HTB sorbents are pressed into pellets prior to calcination, ceramic monoliths can be prepared. Heating to temperatures in excess of 1250 °C results in the melting of the sorbent to form millimetre-sized crystals of bronzoid phases. Thermal analysis shows that melting of the cation-exchanged tungstate sorbents is initiated at temperatures as low as 850 °C and concludes by 1300 °C. The absence of any significant mass loss immediately after melting, as well as chemical analyses before and after melting, confirm that Cs is not volatilized to any significant extent at the temperatures required to generate durable, coarsely crystalline products. The melted bronzoid product is a multiphase ceramic in which Cs+ remains bound within, and appears to stabilize, the hexagonal bronze phase, even after complete melting at 1300 °C, while elements such as Sr2+ are present within other tungstate phases. The bronzoid chemical system appears capable of accommodating a wide range of other elements. Here we have demonstrated that modification of the sorbent properties by incorporation Mo does not impact severely on the durability of materials prepared below 1000 °C, even when exposed to strong acid (pH=1) and elevated temperature (150 °C). As an example, one-day MCC1 leach rates lower than 1×10−5g/m2/day were measured using demineralized water at 90 °C for Cs-saturated Mo-doped sorbents that had been heated in air at 900 °C, while the fraction of Cs leached from powdered samples in 0.1 M HNO3 solutions at 150 °C for 4 days is only 4×10−3 g/m2/day.
Effects of Technical Adsorbents and Cleaning Agents in a Cement Matrix – A Case Study
Authors: Dario Mårten , Molera Mireia , Allard Bert 
Published: April 2011

ABSTRACTThe effects of organic cleaning agents (totally three) and degradation products from solid technical adsorbents (two) on the sorption of Eu on cement and TiO2 were measured with variation of concentration (0.001–10 % of the water phase for the cleaning agents, alkaline degradation products corresponding to 0.03–8 mM DOC for the adsorbents) and reaction time (up to 420 d). The effects of the cleaning agents Industrikombi and Prefect Citron were minor. The degradation of the ion exchanger (metaacrylic polymer) had no significant effect on the Eu-sorption. The other adsorbent (filter aid, inert fibre; acrylonitrile polymer) was rapidly degrading at high pH, and the degradation products had a significant reducing effect on the sorption of Eu at added DOC-levels in the mM-range. This category of adsorbent materials should not be incorporated in a cement waste matrix or be stored in a cementitious environment together with radionuclides.
Atmospheric Corrosion of Copper 450 Metres Underground. Results From Three Years Exposure in the Äspö HRL
Authors: Taxén Claes 
Published: April 2011

ABSTRACTResults from an atmospheric exposure of copper at the Äspö Hard Rock Laboratory (HRL) are reported. Corrosion test coupons were exposed under sheltered conditions at 450 meters depth. The exposure was performed in order to gain insight into the likely state of a copper canister surface at the time when water begins to fill a repository for nuclear waste. The conditions for the experiment were selected to be relevant for the conditions predicted for a repository during an initial dry phase. Visual observations show that copper exposed at ambient temperature remained bright and shiny whereas coupons exposed at elevated temperature had a dull greenish appearance.
Anaerobic Corrosion of Steel in Bentonite
Authors: Smart Nicholas R. , Rance Andrew P. , Werme Lars O. 
Published: April 2011

ABSTRACTIn Sweden, spent nuclear fuel will be encapsulated in sealed cylindrical canisters, consisting of a ferrous insert and a copper outer container, for disposal in a geologic repository. Ferrous support structures will also be used in the repository, which will be backfilled with bentonite clay. Once any residual oxygen has been consumed, any ferrous material exposed to anoxic groundwater will undergo anaerobic corrosion, liberating hydrogen, forming a magnetite film, and releasing iron ions into the surrounding matrix. In order to characterise these processes the rate of hydrogen generation of steel in bentonite was measured using a barometric gas cell technique. The initial corrosion rates were found to be higher than measured previously in comparable aqueous solutions, but the long-term corrosion rates were similar. Analysis of the bentonite matrix showed that iron produced by corrosion had penetrated into the bentonite matrix, suggesting that ferrous ion exchange had occurred.
Development of a Used Fuel Container for Nuclear Fuel Waste
Authors: Maak Peter 
Published: April 2011

ABSTRACTThe deep geologic repository (DGR) concept is one of the approaches being considered in Canada for long-term management of used CANDU fuel. The Canadian concept entails encapsulating used CANDU fuel bundles in durable used-fuel containers (UFCs) and burying the UFCs in an engineered repository at depth in the Canadian Shield. Currently, an updated concept for a DGR is being prepared by Ontario Power Generation (OPG).This technical paper describes OPG's studies from 1999 to 2002 that have led to the development of an updated reference UFC design. The updated UFC design holds 324 used CANDU fuel bundles. It consists of an outer corrosion-resistant oxygen-free phosphorous-doped copper vessel and an inner load-bearing steel vessel. The used-fuel bundles are placed within a fuel basket for handling and loading into the UFC. This reference UFC design would be used for future safety assessment and engineering studies.
Groundwater Flow and Transport Modelling at Äspö for a Glaciation Period
Authors: Jaquet O. , Siegel P. , Klemenz W. , Selroos J. O. 
Published: April 2011

This study [1] was performed for SKB (Swedish Nuclear Fuel and Waste Management Co) within the framework of the assessment of the long-term safety of a deep repository for spent nuclear fuel.Subsequent to work performed by [5], SKB decided to carry out additional hydrogeological modelling studies related to glaciation effects at Äspö. In particular, subglacial groundwaterflow and the impact assessment on a repository required further studies. The presence of subglacial groundwater flow beneath ice sheets is due to basal melting occurring during glaciation periods.As compared to the previous model [5], the domain geometry and processes involved remained identical but this time numerical calculations are performed with the NAMMU program. Modified assumptions corresponding to specific boundary conditions were implemented and additional variations of the base case were simulated.