bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinking Characteristics of an Injectable Poly(Propylene Fumarate)/ β-Tricalcium Phosphate Paste and Mechanical Properties of the Crosslinked Composite for Use as a Biodegradable Bone Cement
Authors: Peter S.J. , Kim P. , Yasko A.W. , Yaszemski M.J. , Mikos A.G. 
Published: April 2011

AbstractWe investigated the crosslinking characteristics of an injectable composite paste of poly(propylene fumarate) (PPF), N-vinyl pyrrolidinone (N-VP), benzoyl peroxide (BP), sodium chloride (NaCl), and β-tricalcium phosphate (β-TCP). We examined the effects of PPF molecular weight, N-VP/PPF ratio, BP/PPF ratio, and NaCl weight percent on the crosslinking temperature, heat release upon crosslinking, gel point, and the composite compressive strength and modulus. The maximum crosslinking temperature did not vary widely between formulations, with the absolute values falling between 38 and 48 °C, and was much lower than that of 94°C for poly(methyl methacrylate) bone cement controls tested under the same conditions. The total heat released upon crosslinking was decreased by an increase in PPF molecular weight and a decrease in N-VP/PPF ratio. The gel point was effected strongly by the PPF molecular weight, with a decrease in PPF molecular weight leading to a more rapid gel point. An increase in initiator concentration had the same effect to a lesser degree. The time frame for curing was varied from 1 -121 minutes, allowing the composite to be tailored to specific applications. The compressive strength and compressive modulus values increased with decreasing N-VP/PPF, increasing NaCl content, and increasing BP/PPF ratio. For all formulations, the compressive strength values fell between 1 and 12 MPa, and the compressive modulus values fell between 23 and 265 MPa. These data suggest that injectable PPF/β-TCP pastes can be prepared with handling characteristics appropriate for clinical orthopaedic applications and that the mechanical properties of the cured composites are suitable for trabecular bone replacement.
Tailoring of the Nitrogen Profile in Thin Gate Oxides Using Substrate Nitridation by Nitric Oxide
Authors: Halimaoui A. , Henrisey E. , Hernandez C. , Martins J. , Paoli M. , Regache M. , Vallier L. , Bensahel D. , Blanchard B. , Rouchon D. , Martin F. 
Published: April 2011

ABSTRACTDirect nitridation of the silicon substrate using gaseous NO at 550–700°C, 10 mbar is studied using physical (SIMS, TEM, XPS) and electrical characterisations. The nitrogen profile can be tailored for the fabrication of thin nitrided oxides as in the case of implanted nitrogen. Degradation of the I(V) characteristics has been evidenced when the nitrogen amount increases.
Crystalline Structure Around the Single Vacancy in Silicon: Formation Volume and Stress Effects
Authors: Antonellip A. , Kaxiras Efthimios , Chadi D. J. 
Published: April 2011

ABSTRACTThe crystalline structure surrounding a single neutral vacancy in silicon is investigated through extensive first-principles total-energy calculations. The results indicate the existence of two distinct distortions of the lattice around the vacancy with essentially the same formation energies at zero pressure, but, however, with different formation volumes. The effect of hydrostatic and biaxial stresses on the relative concentration of each distortion is discussed, suggesting experimental ways to investigate the crystalline structure around the single vacancy and its role as a mediator of atomic diffusion in silicon.
New Tight-Binding Method for Simulation of Defect Configurations, Creation and Diffusion Mechanisms in Solids: Application to Silicon
Authors: Khakimov Zokirkhon M. 
Published: April 2011

ABSTRACTThis paper presents the self-consistent tight-binding method of new generation which, unlike other tight-binding methods, allows one to calculate structural energies of multiatomic systems (molecules, clusters, defects in solids) and their spectroscopic energies in the framework of the same computational scheme and with comparable accuracy. Reliability of the method is illustrated considering defect state problems in crystalline and amorphous silicon (electronenhanced- atomic diffusion, metastable defect creation, defects with effective-negative correlation energies, etc.) and comparing obtained results with ab initio calculations and experimental data.
Electrical Active Defects in the Band-Gap Induced by Ge-Preamorphization of Si-Substrates
Authors: Boussaid F. , Olivie F. , Benzohra M. , Alquier D. , Claverie A. , Martinez A. 
Published: April 2011

ABSTRACTUltra-shallow p+ -n junctions have been obtained from Ge+ -preamorphized and crystalline <100> silicon substrates. B+ and BF2+ dopants have been used. Boron was implanted at low energy 3 keV / 1015 cm−2 while an equivalent energy of 15 keV / 1015 cm−2 was chosen for BF2+. Rapid Thermal Annealing (RTA) for 15 s at 950 °C was then used for dopant electrical activation and implantation damage removal. Electrically active defects in these samples were characterized using Deep Level Transient Spectroscopy (DLTS) and isothermal transient capacitance (ΔC(t, T)). Two electron traps were detected in the upper half of the band gap at Ec – 0.20 eV and Ec – 0.45 eV, respectively. These traps are shown to be induced by the Ge+ preamorphization stage. Dopant implantation along with RTA result in the formation of a depth distributed energy continuum for B+ and BF2+ implants. Each continuum has been ascribed to annealing residual defects. Low energy B+ implantation is seen to induce twice as many defects as BF2+, implantation. From isothermal transient capacitance (ΔC(t, T)), reliable damage concentration profiles have been obtained, revealing that preamorphization induces not only defects in the regrown silicon layer but also a relatively high concentration of electrically active defects up to 3.5 μm into the bulk.
Erbium Doped Si/Sige Waveguide Diodes: Optical And Electrical Characterization
Authors: Neufeld E. , Luigart A. , Sticht A. , Brunner K. , Abstreiter G. 
Published: April 2011

AbstractWe have fabricated erbium- and oxygen-doped Si/SiGe waveguide diodes showing the characteristic 1.54 µm electroluminescence (EL) from incorporated Er+3, ions. All samples were grown by molecular beam epitaxy (MBE). The EL from the polished end facet of the waveguide was measured with a confocal microscope revealing a spatially narrow emission. Additional annealing was not necessary to improve the luminescence characteristics. Only a weak temperature dependence is found for the EL intensity between 4K and room temperature.
Measurements of Confined Energy Levels and Coulomb Charging Effect in Self-Assembled Ge Quantum Dots by Admittance Spectroscopy
Authors: Zhang S. K. , Jiang Z. M. , Zhu H. J. , Lu F. 
Published: April 2011

AbstractWe perform measurements of the discrete quantum energy levels and Coulomb charging of self-assembled Ge quantum dots imbedded in Si barriers by using the admittance spectroscopy technique that was originally developed to measure the defect levels of bulk materials and the band offsets of heterojunctions. By varying the bias voltage, the population of carriers in the dot changes and the Coulomb charging effect could be clearly seen from the step-like change of the activation energy for hole emission in the admittance spectra. Up to five holes charged in a Ge dot with a lateral dimension of 13nm is observed. The energy levels of ground state and first excited state are determined. The advantages of this method are the relatively high measuring temperature, large signal to noise ratio, and its simple and straightforward use and interpretation. The requirement on the uniformity of the dot size distribution of the sample is quite tolerant.
Real-Time Observation of Ti Silicide Epitaxial Islands Growth with the Photoelectron Emission Microscopy
Authors: Yang W. , Ade H. , Nemanich R. J. 
Published: April 2011

AbstractThe formation of nanoscale Ti silicide islands was observed by Photo-electron emission microscopy (PEEM). The islands were prepared by deposition of an ultrathin Ti (3–12ML) on Si(001) at room temperature and at an elevated temperature of 950°C. The island formation was initiated by in situ annealing to 1150° C. It was observed that initially Ti silicide islands form while longer annealing indicates some islands move and coalesce with other islands. Most of the islands are similar in size and have relatively uniform separation. Also, it was shown that for continued Ti deposition at a temperature of 950°C, the density of islands did not increase. However, islands grew together when their perimeter lines touch each other. The results are described in terms of island growth processes of coalescence and ripening.
Low-Energy Plasma Enhanced Chemical Vapor Deposition
Authors: Rosenblad Carsten , Graf Thomas , Dommann Alex , Von känel Hans 
Published: April 2011

AbstractWe discuss a new method for plasma enhanced chemical vapor deposition, applied to the epitaxial growth of Si and of Si-Ge heterostructures. Growth rates up to 5 nm/s become possible at substrate temperatures below 600°C, by utilizing very intense but low energy plasmas to crack the reactive gases, SiH4 and GeH4, and to speed up the surface kinetics. The method is applied to the synthesis of step-graded Si-Ge buffer layers, exhibiting the well known cross-hatched surface morphology.
Characteristics of Surface-Channel Strained Si1-yCyn-MOSFETS
Authors: Rim K. , Mitchell T. O. , Hoyt J. L. , Fountain G. , Gibbons J. F. 
Published: April 2011

AbstractThe first demonstration of n-MOSFETs fabricated using strained Si1-yCy surface channels is reported. Tensile-strained Si1-yCy layers with substitutional carbon contents up to 0.8 atomic percent were epitaxially grown on <100> Si substrates by rapid thermal chemical vapor deposition, using silane and methylsilane as the silicon and carbon precursors. n-MOSFETS were fabricated using standard MOS processing with reduced thermal exposure to minimize the possibility of strain relaxation. A remote plasma CVD oxide was employed to form the gate oxide. The Si1-yCy devices exhibit electrical characteristics that are typical for Si n-MOSFETs, with good turn-on and subthreshold characteristics. MOS capacitance-voltage analysis demonstrates comparable oxide interface qualities for the Si1-yCy and Si control devices. No carbon-related leakage current is observed in source and drain diode junctions. Characterization of the MOSFET electron inversion layer mobility at room temperature shows comparable mobilities, within the sensitivity of the measurement, for the Si1-yCy and Si control devices. This is in contrast to the mobility enhancement observed in n-MOSFETs fabricated using tensile- strained Si grown on relaxed Si1-xGex layers. At low temperatures, the inversion layer mobility of Si1-yCy devices is lower than that of the Si controls, and appears to be affected by Coulomb and possibly random alloy scattering.
Quantitative Experimental Determination of The Effect of Dislocation - Dislocation Interactions on Strain Relaxation in Lattice Mismatched Heterostructures
Authors: Stach E. A. , Hull R. , Tromp R. M. , ROSS F. M. , Reuter M. C. , Bean J. C. 
Published: April 2011

AbstractWe present real time observations of the interaction of dislocations in heteroepitaxial strained layers using a specially modified ultrahigh vacuum transmission electron microscope equipped with in-situ deposition capabilities. These observations have led to delineation of the regime of epilayer thickness and composition where dislocation interactions result in blocking of the propagating threading segment. It is found that both the blocking probability as well as the magnitude of the dislocation interaction force are strongly dependent on the Burgers vectors of the dislocations involved, with the greatest effects observed when the Burgers vectors of the two dislocations are parallel with respect to each other. Frame-by-frame analysis of the motion of the dislocation threading segment during interaction is used to extract the magnitude of the interaction stresses as a function of both the level of heteroepitaxial strain and the dislocation geometry. Finally, by continuing growth following observations of blocking during annealing, we find that blocked dislocations are likely to remain in that configuration until substantial additional heteroepitaxial stresses are incorporated into the layer. These results have direct relevance to the successful integration of strained layer heterostructures into electronic device applications. This is because blocked threading segments result in the introduction of undesired band gap states, enhance impurity diffusion, modify surface morphology and act to limit the dislocation density reductions achievable in graded buffer structures.
Thermal Reliability of Pt/Ti/Pt/Au Schottky Contact on InP with a GalnP Schottky Barrier Enhancement Layer
Authors: Kuo H. C. , Lin C. H. , Moser B. G. , Hsia H. , Tang Z. , Chen H. , Feng M. , Stillman G. E. 
Published: April 2011

AbstractWe present the studies of the thermal stability of various metal including Au, Ti, Pt, Pd and Pt/Ti/Pt/Au Schottky contacts on strained Ga0.2In0.8P/InP semiconductors. Auger electron spectroscopy (AES) analysis and cross-sectional TEM of the thermally annealed Schottky diode were performed to investigate the failure mechanism. For Pt/Ti/Pt/Au schottky contacts on strained GalnP/InP, no significant change was found for samples annealed up to 350°C. However, a drastic degradation of the barrier height and the ideality factor was observed in samples annealed at 400°C, which may be caused by the interdiffusion and penetration of metals into the semiconductor. Finally InGaAs/InP doped channel heterojunction FET's (DC-HFET's) with a GaInP Schottky barrier enhancement layer (SBEL) were grown and fabricated. The 0.25 μm gate-length devices showed excellent DC and RF performance, with anfi of 117 GHz and an fmax of 168 GHz.
Fermi-Level Effect and Junction Carrier Concentration Effect on Boron Distribution in GexSil−x/Si Heterostructures
Authors: Chen CHang-Ho , Gösele Ulrich M. , Tan Teh Y. 
Published: April 2011

AbstractDopant segregation mechanism in general involves the chemical effect, the Fermi-level effect, and the effect of the junction carrier concentrations. Satisfactory fits of available B distribution profiles in GexSil−x/Si heterostructures have been obtained using such a model, but with the chemical effect not important. The Fermi-level effect determines the difference in the ionized B solubilities in GexSil−x and Si. The singly-positively charged crystal self-interstitials I+ governs the boron diffusion process. The junction carrier concentration affects the concentration of I+ and solubility of B in the region and hence controls B diffusion across the heterojunction.
A Mechanism for the Removal Of Dislocations in SOI Compliant Substrate Systems
Authors: Kukta R. V. , Freund L. B. 
Published: April 2011

AbstractIt is demonstrated that the time required for strain transference during the postgrowth anneal of a SOI compliant substrate system is much too long to explain the observed reduction in dislocation density in the resulting microstructure. A mechanism by which misfit dislocation segments are drawn out of the system through viscous dissipation in the bonding layer is proposed and demonstrated to be consistent with observation. The mechanism is mtodeled in the context of elastic dislocation theory and linear viscoelasticity.
Optical Absorption in ZnSe-GaAs Heterovalent Quantum Structures
Authors: Funato Mitsuru , Fujita Shizuo , Fujita Shigeo 
Published: April 2011

AbstractZnSe-GaAs(001) heterovalent quantum structures, multiple quantum wells (MQWs), were fabricated. Since the band offsets in this heterovalent heterostructure are controllable, different offsets can artificially be put at both sides of the GaAs wells, which may lead to modification of the electronic properties of the MQWs. This hypothesis was examined by the optical absorption measurement. Consequently, by changing the valence band offset at the GaAs-on-ZnSe interface from 0.6 to 1.1 eV, while keeping that at ZnSe-on- GaAs constant at 0.6 eV, the absorption edge energies of the MQWs shifted from 1.43 to 1.37 eV. This indicates the presence of an internal electric field and the capability of controlling the electronic properties of heterovalent MQWs with the completely same structural parameters. The numerical analyses of the Poisson and Schrddinger equations well explain the trend of this experimental result.
Finite Temperature Quasicontinuum Methods
Authors: Shenoy Vivek , Shenoy Vijay , Phillips Rob 
Published: April 2011

AbstractIn this paper we extend the quasi-continuum method to study equilibrium properties of defects at finite temperatures. We present a derivation of an effective energy function to perform Monte Carlo simulations in a mixed atomistic and continuum setting. It is shown that the free energy minimization technique can be easily incorporated into the quasi-continuum frame work, permitting a reduction of the full set of atomistic degrees of freedom even in the finite temperature setting. The validity of the proposed methods is demonstrated by computing the thermal expansion and the temperature dependence of the elastic moduli for Cu. We also employ the quasi-continuum free energy minimization method to study the finite temperarure structure of a dislocation core in Al.
Effect of Non-Glide Components of the Stress Tensor on Deformation Behavior of Bcc Transition Metals
Authors: Ito K. , Vitek V. 
Published: April 2011

AbstractIn this paper we demonstrate by atomic computer simulation that the non-Schmid slip behavior in bcc metals is a direct consequence of the non-planar core structure of 1/2<111> screw dislocations and their response to the applied stress tensor. The analysis has been carried out in detail for tantalum using the Finnis-Sinclair type central force many-body potentials. Two distinct non-Schmid effects have been discerned. The first is twinning-antitwinning slip asymmetry on {112} planes. This is an intrinsic property of the bcc structure and depends on the sense of the applied glide stress. The second non-Schmid effect is extrinsic and is controlled by the non-glide shear stresses perpendicular to the total Burgers vector on {110} planes into which the stress-free core of screw dislocations spread.
Noncrucial Role of the Defects in the Splitting for Hydrogen Implanted Silicon With High Boron Concentration
Authors: Popov V.P. , Stas V.F. , Antonova I.V. 
Published: April 2011

AbstractThe present work deals with the investigation of the electrical and structural properties of heavily boron-doped silicon irradiated by hydrogen. Blistering and splitting processes are enhanced with an increase in boron concentration in the crystal. The measured values of perpendicular strain are over 0.7% which corresponds to a gas overpressure of 0.5 GPa. Processes which lead to blistering and splitting is better described in the frame of a gas pressure model than a model of local stress caused by the defects.
Optical Properties of Laser-Modified Diamond Surfaces
Authors: Khomich A.V. , Polyakov V.I. , Pimenov S.M. , Kononenko V.V. , Konov V.I. , Gloor S. , Lüthy W. , Weber H.P. 
Published: April 2011

AbstractResults are reported on laser-induced surface modification of 150-400 µm thick free-standing diamond films with excimer lasers under different irradiation regimes, including laser polishing at a grazing beam incidence or ablative etching of the films at the normal beam incidence. Properties of the laser-graphitized layer at the diamond surface were studied with optical spectroscopy techniques in the process of oxidative removal of the layer with increasing temperature of oxidation in ambient air. The optical properties and oxidation stability of the laser-modified surface layer were found to change through its thickness from the surface to the diamond interface, depending on the laser ablation regime.
Self-Compression and Diamond Nucleation In Irradiated Carbon Onions - A Theoretical Model
Authors: Zaiser M. 
Published: April 2011

AbstractThe nucleation of small diamond crystals during irradiation of spherical graphitic particles (’bucky onions’) is discussed. A mechanism for irradiation-induced self-compression of such ’onions’ is proposed. It is demonstrated that this may yield pressures which are sufficiently high for diamond formation. The theoretical results are in good agreement with experimental findings.
Behaviour of CS and I In Zirconia Based Fuel
Authors: Degueldre C. , Pouchon M. , Doebli M. , Ledergerber G. 
Published: April 2011

AbstractA zirconia based ceramic is foreseen as an inert matrix fuel for burning excess plutonium in light water nuclear reactors. For reactor safety reasons the behaviour of volatile fission products such as cesium and iodine must be studied since a retention of fission products is favourable for licensing the studied inert matrix fuel. In this study, implantation of Cs and I was performed into polycrystalline (Zr0.85, Y0.15)O1.925 samples. The implantation depth was selected on the basis of the ability to observe by Rutherford backscattering spectroscopy (RBS) the behaviour of Cs and I after treatment. With a 1 MeV incident energy, the ions are implanted at a depth of 200 nm as predicted by TRIM. After implantations full quantification of I and Cs concentration profiles was performed by RBS. The implantation profiles are measured as a function of sample temperature during stepwise heating programs. It is interesting to observe retention of Cs and I at relatively high temperature (e.g. for 2 h, below 900 K for Cs and below 1400 K for I). This behaviour is likely to be due to the size and interactions of these species in the zirconia solid solution.
Ion Irradiation Effects for Two Pyrochlore Compositions: Gd2Ti2O7and Gd2Zr207
Authors: Wang S. X. , Wang L. M. , Ewing R. C. , Govindan Kutty K. V. 
Published: April 2011

AbstractPyrochlore is an important nuclear waste form phase for actinide immobilization. Two synthetic pyrochlores, Gd2Ti2O7and Gd2Zr2O7were irradiated at various temperatures (25 K to 1073 K) by different ion species (1.5 MeV Xe+, 1.0 MeV Kr+, and 0.6 MeV Ar+). The titanate pyrochlore amorphized at relatively low doses (0.5 ∼ 0.6 dpa). Temperature dependence of the amorphization dose for titanate pyrochlore was measured, and the critical temperatures for amorphization were 1300 K, 1100 K and 950 K by 1.5 MeV Xe+, 1.0 MeV Kr+and 0.6 MeV Ar+, respectively. The higher critical temperature for the heavier ion irradiation is consistent with an amorphization mechanism by which the heavier ion produces a larger cascade. The zirconate pyrochlore, Gd2Zr2O7, showed a strong amorphization “resistance”. Gd2Zr2O7did not become amorphous under 1.0 MeV Kr+and 1.5 MeV Xe+irradiation. After prolonged irradiation (up to 7 dpa) even at a temperature of 25 K, no amorphization was observed. The irradiated zirconate pyrochlore showed abundant dislocations as observed by TEM. The pyrochlore structure of Gd2Zr2O7transformed to the fluorite structure after irradiation. The diffraction patterns of irradiated Gd2Zr2O7showed the existence of short-range ordering of cations. The large difference between these two pyrochlores emphasizes the strong effect of chemical composition on radiation-induced amorphization.
Structural Evolution of Simplified Nuclear Glasses Under β-Irradiation: A Raman Spectroscopy Study
Authors: Boizot B. , Petite G. , Ghaleb D. , Reynard B. , Calas G. 
Published: April 2011

AbstractThe ageing processes of simplified nuclear glasses under β-irradiation have been investigated on zirconium-bearing aluminoborosilicate glasses by micro Raman spectroscopy. No dose rate effect has been detected between 2.103 and 2.104 Gy/s for a 3.107 Gy integrated β dose. Important structural differences appear between the volume and the surface, with an increase of the polymerisation and a better defined danburite-like ring structure in the bulk relative to the surface. Molecular 02 is created during glass ageing, mostly close to the sample surface. Both processes indicate an important reorganisation of the glassy matrix during β-irradiation.