bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of Samarium Oxide Deposition on Gallium Arsenide
Authors: Stewart Anthony Duane , Scheuermann Andrew G , Gerger Andy P , Gila Brent P , Abernathy Cammy R , Pearton Stephen J 
Published: February 2009

AbstractSamarium oxide (Sm2O3) and samarium gallium oxide (SmxGa1-x)2O3 have been proposed as candidate dielectric materials for the development of gallium arsenide (GaAs) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) technology. Growth of thin (20nm-50nm) Sm2O3 and (SmxGa1-x)2O3 layers on GaAs substrates via plasma-assisted molecular beam epitaxy (MBE) has been performed using a range of growth temperatures and samarium cell temperatures. X-ray photoelectron spectroscopy (XPS) of the deposited films showed evidence of unbonded Sm metal in the films which decreased with decreasing Sm cell temperature, but was relatively independent of substrate temperature. Stoichiometry of the oxide was found to be independent of substrate temperature, but increased in oxygen to metal ratio as the Sm cell temperature was decreased. Decreasing the Sm cell temperature also suppressed the formation of the monoclinic phase and promoted the growth of the cubic phase. Films grown at higher (500şC) temperature showed the presence of a crystalline interface, but relatively high surface roughness and the presence of multiple crystalline phases. Current-voltage analysis of one hundred micron diameter MOS diodes showed breakdown fields at 1 mA/cm2 of up to 4.35 MV/cm. Breakdown field was found to decrease with increasing Sm unbonded metal content in the films. The effect of stoichiometry and phase distribution on the interface state density (Dit) and capacitance-voltage behavior of MOS diodes was also investigated.
Formation of Doping Profiles in Float Zone Silicon by Helium Implantation and Plasma Hydrogenation
Authors: Job Reinhart , Niedernostheide Franz-Josef , Schulze Hans-Joachim , Schulze Holger 
Published: February 2009

AbstractBy means of two-point-probe Spreading Resistance (SR) analyses, the formation and evolution of hydrogen-related and vacancy-related donor and acceptor states were studied in helium implanted and subsequently hydrogen plasma-treated n-type Float-Zone (FZ) silicon wafers. He-implantation was carried out at 3.75 MeV, applying fluences of 1×1014 cm-2 and 2×1013 cm-2. After 15-min post-implantation H-plasma exposures at substrate temperatures between 350 °C and 500 °C, distinct surplus doping profiles were observed in the subsurface layers of the treated FZ Si samples down to about 20 μm depth. Enhanced donor concentrations could be observed as well acceptor-like states, at least partially compensating for the initial n-type doping, so that even buried p-type layers can be created under appropriate process conditions. The nature of the defect complexes that were responsible for the observed doping profiles in the subsurface layer of the studied samples will be discussed.
Search For New Piezoelectrics
Authors: Ganesh Panchapakesan , Cohen Ronald 
Published: February 2009

AbstractRecent first principles simulations using density functional theory and novel low temperature x-ray diffraction experiments show the existence of a high pressure morphtotropic phase boundary (MPB) in pure PbTiO3. In this paper we apply chemical pressure by substituting smaller atoms in the ABO3 ‘A’ and ‘B’ sites. We find that the ground state of layered PbSnTiO3 (PSnT) is Pmm2, and for rocksalt SnGeTiO3 and PbGeTiO3 is R3m. The polarization of PbSnTiO3 is large (1.13,0,0)C/m2 and is due to the large Born effective charge of the small ‘Sn’ atom. We estimate the d33 for PSnT to be about 2400 pC/N, which is as large as that of currently used relaxor ferroelectrics.
Enhanced 1.54 μm Luminescence in Er-doped ZnO Nanoparticle Films via Indirect Excitation
Authors: Pan Zhengda , Morgan S. H. , Ueda A. , Aga R. , Xu H. Y. , Hark S. K. , Mu R. 
Published: February 2009

AbstractPhotoluminescence (PL) of Er-doped ZnO nanoparticle films was studied. The films were fabricated using e-beam evaporation. The films were subsequently annealed at 700 °C in air for an hour. The atomic force microscopy (AFM) image revealed nano-sized ZnO particles. PL was measured at two excitation wavelengths, 325 and 514.5 nm. The 325 nm is used for exciting the ZnO host semiconductor and 514.5 nm is used for directly exciting Er3+ ions in the ZnO films. Er3+ luminescence was observed from the annealed film using either indirect (325 nm) or direct (514.5 nm) excitations. It has been found that the indirect excitation is about 40 times more efficient than the direct excitation in producing 1.54 μm PL. With indirect excitation, the Er3+ luminescence observed is attributed to energy transfer from ZnO host to the Er3+ ions doped. Energy transfer from e-h pairs resulting from ZnO host excitation may provide efficient routes for exciting Er3+ ions inside nano-crystalline particles of the films.
Three-Dimensional Integration Technology for Advanced Focal Planes
Authors: Keast Craig Lewis , Aull Brian , Burns James , Chen Chenson , Knecht Jeff , Tyrrell Brian , Warner Keith , Wheeler Bruce , Suntharaligam Vyshi , Wyatt Peter , Yost Donna 
Published: February 2009

AbstractWe have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using it.
Statistical Analysis of the Influence of Thinning Processes on the Strength of Silicon
Authors: Yang Yu , Cotrin Teixeira Ricardo , Roussel Philippe , Swinnen Bart , Verlinden Bert , De Wolf Ingrid 
Published: February 2009

AbstractWafer thinning, one of the key enabling techniques for 3D integration, is widely studied due to its impact on Si breakage strength. However, most studies only focused on the average strength, without checking the failure mechanisms. This may result in misleading conclusions and the mechanism of breakage is still ambiguous.
In this paper, the mechanical strength of wafers that were thinned using different methods [rough grinding(RG), fine grinding(FE), plasma etching(PE), chemical mechanical polishing(CMP)] was evaluated statistically and through failure analysis. The results provide the industry guidance on their wafer thinning strategy.
Si wafers were thinned down to 300μm by different thinning techniques: only RG; RG+FG; RG+FG+10μm CMP and RG+FG+10μm PE. Next the samples were diced into strips and the strength was tested using a 4-point bending test.
The breakage strength of the dies was plotted in Weibull graphs and on wafer maps. Both RG and PE samples showed a strong bimodal distribution. On the other hand, both FG and CMP wafers showed a monomodal behaviour. This observation was unexpected and until now never reported in literature.
The RG wafer has large surface grooves and is the weakest one, as expected. The bimodal distribution of the strength of RG-dies could be related to the direction of the grinding marks on the surface (along width or length of the Si strips). There is a direct correlation with the position of the dies on the wafer and the bimodal distribution. Samples with lines perpendicular to the tensile stress (along the width of the strips) are more vulnerable than the rest. The fracture on these samples propagates vertically from the ground surface, along the {110} plane. The others are stronger and break along the {111} plane.
FG improves both the surface roughness and the strength compared to RG. The Weibull curve, with a monomodal behavior, shifts to a higher breakage strength, indicating that the effect of the grooves on the breakage strength is removed by FG.
After CMP, the strength raises 17% compared to FG-Si due to the removal of surface roughness. Similarly, PE increases the average strength by 15% from FG. However, the Weibull plot shows that after PE, there is again a bimodal failure distribution. The weaker one falls on top of the FG distribution and the stronger one mixes up with the CMP. This indicates that although a large fraction of these samples have a similar strength as CMP, but some parts still have defects, probably local roughness related, that serve as easy initiation of fracture.
This study shows that the orientation of the grinding marks plays an important role in determining the fracture plane and thus the strength. FG can efficiently remove this effect. We also showed for the first time that even after PE there is a bimodal strength distribution. Part of the dies has the same strength as the ones after CMP, but part of the population still has a lower strength.
Characterization of texture and microstructure of electrodeposited Ni layers
Authors: Noda Homuro , Shibata Akinobu , Sone Masato , Ishiyama Chiemi , Higo Yakichi 
Published: February 2009

AbstractThe texture and microstructure of electrodeposited Ni layers formed in an additive-free Watt's bath were investigated. The microstructure of the electrodeposited Ni layer consists of fine columnar grains extending along the growth direction. The major texture components of electrodeposited Ni layers on Ni-P substrate were (112) and (110) fibers. On the other hand, electrodeposited Ni layers on Cu substrate had a strong (110) fiber texture. In the vicinity of the interface between the electrodeposited Ni layer and the Cu substrate, obvious epitaxial regions were not observed. Many twins parallel to the growth direction were observed in the electrodeposited Ni layer. It is suggested that grains with a twin relationship grew preferentially during the electrodeposition reaction.
The National Nuclear Laboratory and Collaborative University Research in the UK
Authors: Fairhall Graham A. 
Published: February 2009

AbstractThe UK has recently established its first National Nuclear Laboratory (NNL). This has been formed out of the Nexia Solutions organisation, formally the Research and Technology subsidiary of BNFL. Over the next year the NNL will develop so that it can fulfil its mission, which will include the development and maintenance of key skills and undertaking strategic R&D programmes both in the UK and in international collaborations.
A key role of the NNL will be to enhance its interactions with universities to facilitate skills transfer into the nuclear industry as well as support its R&D programmes. Over the past decade the NNL and its predecessor has already established close relationships with leading universities in the UK including Sheffield, Manchester, Leeds and Imperial College London. One of the key objectives of the NNL has been to work in an integrated way with university researchers with programmes spanning fundamental research through to applied R&D.
This paper describes the future plans for working with universities as the NNL develops, building on the success to date.
Joint R&D research programmes already cover many important areas for the nuclear industry. This includes support for the UK Pu disposition programme where R&D at the Immobilisation Science Laboratory, Sheffield has included investigating a range of ceramic and glass wasteforms which has allowed a number of ceramic wasteforms to be down selected for detailed evaluation. Cementation research has included understanding wasteform performance, for example long-term durability. This has involved work on determining free water and the implications for immobilisation of reactive wastes.
Other work involving the NNL and Universities, in particular at Leeds and Manchester, has considered the characteristics and behaviour of intermediate and high level waste sludges. This has included determining the chemical speciation of actinides and fission products, and physical properties of active and simulated sludges using experimental and modelling techniques.
A significant programme on environmental work has been undertaken by the NNL. In research applicable to low level waste disposal and contaminated land reactive transport modelling is utilised to apply experimental and field based research in environmental geochemistry and radiochemistry undertaken by university collaborators. This paper will describe a number of examples of R&D carried out by NNL in association with its university partners.
Calcium Phosphate: A Potential Host for Halide Contaminated Plutonium Wastes
Authors: Metcalfe Brian L. , Donald Ian W. , Fong Shirley K. , Gerrard Lee A. , Strachan Denis M. , Scheele Randall D 
Published: February 2009

AbstractThe presence of significant quantities of fluoride and chloride in four types of legacy wastes from plutonium pyrochemical reprocessing required the development of a new wasteform which could adequately immobilize the halides in addition to the Pu and Am. Using a simulant chloride-based waste (Type I waste) and Sm as the surrogate for the Pu3+ and Am3+ present in the waste, AWE developed a process which utilised Ca3(PO4)2 as the host material. The waste was successfully incorporated into two crystalline phases, chlorapatite, [Ca5(PO4)3Cl], and spodiosite, [Ca2(PO4)Cl]. Radioactive studies performed at PNNL with 239Pu and 241Am confirmed the process. A slightly modified version of the process in which CaHPO4 was used as the host was successful in immobilizing a more complex multi-cation oxide–based waste (Type II) which contained significant concentrations of Cl and F in addition to 239Pu and 241Am. This waste resulted in the formation of cation-doped whitlockite, Ca3-xMgx(PO4)2, β-calcium phosphate, β-Ca2P2O7 and chlor-fluorapatite rather than the chlorapatite and spodiosite formed with Type I waste.
Hybrid Membranes Based on Aromatic Polymer Blends for Fuel Cell Applications
Authors: de Bonis Catia , D'Epifanio Alessandra , Mecheri Barbara , Di Vona Maria Luisa , Trombetta Marcella , Traversa Enrico , Licoccia Silvia 
Published: February 2009

AbstractBlend membranes based on sulfonated polyetheretherketone (SPEEK) and containing 5 wt.% of silylated and sulfonated polyphenylsulfone (SiSPPSU) were prepared and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR) and by electrochemical impedance spectroscopy (EIS). Tests in a direct methanol fuel cell station were also performed.
The experimental results demonstrated that the presence of hybrid polymer SiSPPSU allowed to increase the proton conductivity of electrolyte and to improve its performance under fuel cell operating conditions. Due to its satisfactory properties, SPEEK/ SiSPPSU blend membrane has a potential use in DMFCs operating at intermediate temperatures.
Forging of Steam Turbine Blades with an Fe3Al-based Alloy
Authors: Janschek Peter , Bauer-Partenheimer Knut , Krein Ronny , Hanus Pavel , Palm M. 
Published: February 2009

AbstractThe forging capabilities of two high-strength Fe3Al-based alloys have been evaluated. Based on these results one alloy has been used for forging steam turbine blades. Blades of about 600 mm length were successfully forged by a standard procedure otherwise employed for forging of 9-12 wt.% Cr steels. The forged steam turbine blades showed very good form filling, no pores and smooth surfaces. The blades were finished by cutting and grinding by standard procedures. The microstructure consists out of a Fe3Al matrix with additional Laves phase which predominantly precipitated on grain boundaries. The large Fe3Al grains in the cast precursors did only partially recrystallise during forging. This may be partially due to pinning of the grain boundaries by Laves phase precipitates. Cracks may form at those grain boundaries which are decorated with these brittle precipitates.
On the Effect of Strain Rate and Temperature on the Yield Strength Anomaly in L21-structured Fe2AlMn
Authors: Wittmann Markus W. , Chang Janelle M. , Liao Yifeng , Baker Ian 
Published: February 2009

AbstractThe effects of strain rate and temperature on the yield strength of near-stoichiometric Fe2AlMn single crystals were investigated. In the temperature range 600-800K the yield stress increased with increasing temperature, a response commonly referred to as a yield strength anomaly. No strain rate sensitivity was observed below 750K, but at higher temperatures the yield stress increased with increasing strain rate. Possible mechanisms to explaining the effects of temperature and strain rate are discussed.
Intermetallic Compounds in Co-base Alloys–Phase Stability and Application to Superalloys
Authors: Ishida Kiyohito 
Published: February 2009

AbstractThe phase stability of intermetallic compounds of Co3X has been discussed with a focus on the γ' phase of Co3Al, Co3W and Co3(Al, W) with the L12 structure. The critical temperatures of the γ' phase of Co3Al, Co3W and Co3(Al, W) compounds are estimated to be about 870 , 980 and 1076 , respectively. The effect of alloying elements on the Co-Al-W -base alloys was found to be very similar to that of Ni-base superalloys, where Ti, Ta, Nb and V are the γ' stabilizing elements, while Mn, Fe and Cr are the γ' forming elements. The mechanical properties of Co-Al-W-base alloys were also found to be similar to those of Ni-base alloys. In particular, the flow strengths of Co-Al-W-base alloys at temperatures above 800 were comparable or higher than those of Ni-base superalloys, which implies that the Co-base superalloys strengthened by the γ' phase have great potential as a new type of high-temperature alloys.
Mechanical Testing and Material Modeling of Thermoplastics: Polycarbonate, Polypropylene and Acrylonitrile-Butadiene-Styrene
Authors: Bouvard Jean-Luc , Brown Hayley , Marin Esteban , Wang Paul , Horstemeyer Mark 
Published: February 2009

AbstractThe work presents some results of an ongoing research program aimed at building a material database and material models for specific types of polymers. Results for three thermoplastics are the focus of the present article: polycarbonate, polypropylene, and acrylonitrile-butadiene-styrene. Uniaxial compression / tension tests at room temperature and different strain rates have been performed to characterize their mechanical response. A rate-dependent material model has been developed and implemented in a finite element code to predict such mechanical behavior. The model predictions have shown good agreement with the tests results.
A Molecular Dynamics Study of the Rotational Dynamics and Polymerization of C60 in C60-Cubane Crystals
Authors: Coluci Vitor , Sato Fernando , Braga Scheila F. , Skaf Munir S. , Galvao Douglas S 
Published: February 2009

AbstractRecently, heteromolecular crystals of fullerene C60 and cubane (C8H8) have been synthesized. For some temperatures the C60 molecules are free to rotate whereas cubanes behave like a static bearing in a so-called rotor-stator phases. In this work we report classical and tight-binding molecular dynamics simulations in order to investigate the rotor-stator dynamics and polymerization processes. Our results show that, for 200 K and 400 K, cubane molecules remain basically fixed, presenting only thermal vibrations within the timescale of our simulations, while C60 fullerenes show rotational motions. Fullerenes perform “free” rotational motions at short times (< 1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times (> 10 ps). Random copolymerization among cubanes and fullerenes were observed when temperature is increased, leading to the formation of a disordered structure.
Statistics of Internal Elastic Fields and Dislocation Density Tensor in Deformed FCC Crystals
Authors: Deng Jie , El-Azab Anter , Larson B.C. 
Published: February 2009

ABSTRACTThe statistics of internal elastic fields and dislocation density tensor associated with arbitrary 3D dislocation distributions have been modeled using probability density function and pair correlations. Numerical results for these quantities have been obtained for dislocation structures generated by the method of dislocation dynamics simulation.
Nanomechanical study of synthesis of metallic core-shell clusters via coalescence
Authors: Shintani K. , Mizuno S. 
Published: February 2009

AbstractMorphological evolution of two metallic clusters of different elements at coalescence is investigated using molecular-dynamics (MD) simulation. All the pair combinations of the elements Ni, Cu, Au, Ag, Pt, and Pd are considered. The final structures of united bimetallic clusters are classified into three categories: epitaxial, core-shell, and alloyed. Which type of structure appears via coalescence depends on the size and temperature of clusters, which can be summarized in an observed structure map.
Simulation of Initial Growth Process of Pt Clusters on Carbon Materials – First-Principles Calculations
Authors: Okazaki-Maeda Kazuyuki , Yamakawa Shunsuke , Morikawa Yoshitada , Hyodo Shiaki , Akita Tomoki , Maeda Yasushi , Tanaka Shingo , Kohyama Masanori 
Published: February 2009

AbstractFirst-principles calculations have been applied to investigate the interactions between Ptn (n=1˜13) clusters and a graphene sheet to model the Pt/C fuel-cell catalytic electrode. For the small clustesr (n<7), planar configurations vertically adsorbed on graphene (V-2D) are more stable than the three-dimensional (3D) configurations. For the large clusters (n>7), the 3D clusters are more stable than the V-2D clusters. In order to investigate the effects of defects and dopants in a graphene sheet, the interactions between the Pt13 cluster and the graphene sheet with an atomic vacancy and an dopant atom, such as boron and nitrogen atoms have been examined. For the atomic vacancy, the Pt atom is directly adsorbed on the C atom vacant site. For the Pt13 cluster adsorbed on the graphene sheet doped with the B or N atoms, the Pt atom is not directly adsorbed on the impurity atoms. The adsorption of the Pt13 cluster above the vacancy of the graphene sheet is more stable that that on the doped graphene sheet in the present calculations.
Micromechanics-based conversion of CT data into anisotropic elasticity tensors, applied to FE simulations of a mandible
Authors: Hellmich Christian , Kober Cornelia , Erdmann Bodo 
Published: February 2009

ABSTRACTComputer Tomographic (CT) image data have become a standard basis for structural analyses of bony organs. In this context, regression functions between stiffness components and Hounsfields units (HU) from Computer Tomography, related to X-ray attenuation coefficients, are widely used for the definition of the (actually inhomogeneous and anisotropic) material behavior inside the organ. Herein, we suggest to derive the functional dependence of the fully orthotropic stiffness tensors on the Hounsfield units from the physical information contained in the X-ray attenuation coefficients: (i) Based on voxel average rules for the X-ray attenuation coefficients, we assign to each voxel the volume fraction occupied by water (marrow) and that occupied by solid bone matrix. (ii) By means of a continuum micromechanics representation for bone, which is based on voxel-invariant (species and whole bone-specific) stiffness properties of solid bone matrix and of water, we convert the aforementioned volume fractions into voxel-specific orthotropic stiffness tensor components. The micromechanics model, in combination with the average rule for X-ray attenuation coefficients, predicts a quasi-linear relationship between axial Young's modulus and HU, and highly nonlinear relationships for both circumferential and radial Young's moduli as well as for the shear moduli in all principal material directions. Corresponding whole-organ Finite Element analyses of a partially dentulous human mandible characterized by atrophy of the alveolar ridge show that volumetric strain concentrations/peaks within the organ are decreased when considering material anisotropy, and increased when considering material inhomogeneity.