bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Vacancies in Enhancing Oxygen Diffusion in Silicon
Authors: Oates A. S. , Newman R. C. , Tucker J. M. , Davies G. , Lightowlers E. C. 
Published: March 2011

ABSTRACTMeasurements of optical bands in irradiated Si are combined with numerical modelling of the radiation induced reactions. No evidence is found for appreciable interaction of self-interstitials with O atoms for irradiations carried out at temperatures between 25 and 500°C. The reduction during electron irradiation of stress-induced dichroism in the 9μm oxygen band is shown to occur by sequential capture of a vacancy and a self-interstitial at the oxygen for irradiations carried out between 25 and 280°C. At higher temperatures repetitive capture and release of vacancies at oxygen atoms appears to dominate in the oxygen migration process.
Direct Comparison of FTIR and SIMS Calibrations for [O] in Silicon
Authors: Chu P. K. , Hockett R. S. , Wilson R. G. 
Published: March 2011

ABSTRACTFourier Transform Infra-Red spectroscopy (FTIR) is commonly used to measure interstitial oxygen concentrations in silicon. The absorption coefficient αOX derived from the IR transmittance curve is converted to a concentration value through a multiplicative calibration factor γOX. Presently used calibration factors include 2.45 × 1017 cm−2 (ASTM F121−80), 3.03 × 1017cm−2 (JEIDA), and 4.81 × 1017 cm−2 (ASTM F121−76). These have been obtained from different analytical methods, including charged particle activation, helium carrier gas fusion-gas chromatography, vacuum fusion gas analysis, and photon activation combined with inert gas fusion. An alternative analytical method by secondary ion mass spectrometry (SIMS) is reported here. Oxygen ions of a known fluence are implanted into silicon samples of which oxygen content has been measured by FTIR. SIMS profiles of oxygen are performed using a cesium primary ion beam on a CAMECA IMS-3f. The result is a profile of the superposition of the implanted oxygen and the constant, bulk CZ oxygen. Integration of the implant signal followed by subtraction of the bulk signal can be used to calibrate the implant concentration from the implanted oxygen fluence, so that, in the same sample and during the same measurement, the SIMS calibration and FTIR calibration at the CZ bulk level can be directly compared. The γOX obtained from this method is 3.45 × 1017cm−2 and is closest to the JEIDA value of 3. 03 × 1017 cm−2.
SIMS Measurements of Oxygen in Heavily-Doped Silicon
Authors: Bleiler R. J. , Hockett R. S. , Chu P. , Strathman E. 
Published: March 2011

ABSTRACTOxygen precipitation in CZ silicon is known to provide beneficial yield improvements in integrated circuit processing if the location and amount of precipitation can be properly controlled. The concentration of oxygen in the unprocessed silicon substrate is one of the most important variables to control for achieving these improvements. Fourier Transform Infrared Spectroscopy (FTIR) has successfully been used to measure [0] in silicon when the silicon resistivity is greater than about 0.1 Ω-cm. At lower resistivities typical of p+ and n+ substrates used for epi-wafers as free carrier absorption interferes with the FTIR measurement of bulk [0].This work will focus on how to quantitatively measure oxygen in heavily-doped silicon by Secondary Ion Mass Spectrometry (SIMS) with a high sample thruput, low background signal, and tight σ/x distribution. SIMS calibration is performed against FTIR-calibrated substrates with resistivity higher than 0.1Ωcm. Typical background signals as measured in FZ are a factor of 20 below signals in CZ, and the 160− signal in CZ is over 105 count/sec. resulting in an excellent signal-to-noise ratio for each single measurement. Typical thruput is 18 samples per day where each sample is analyzed four to five times to obtain a σ/x of 3% for an oxygen level of 15 ppma (ASTM F121−80).
Structure and Properties of The Oxygen Donor
Authors: Kimerling L. C. 
Published: March 2011

ABSTRACTDuring aggregation, an assembly of oxygen atoms in silicon produces an electrically active site. The center is an effective mass, helium-like center (double donor) with a wave function of C2v symmetry. The formation reactions of the assembly reveal details of the invisible early stages of aggregation. The donor character of the center controls the aggregation process in heavily doped material. The atomic structure and the source of the electrical activity of the center remain unresolved.
Design Principles for Microwave Heating and Sintering
Authors: Tinga W.R. 
Published: March 2011

AbstractMicrowave heating equations are shown to have a complex functional dependence on material and process parameters such as composition, density, temperature, frequency and geometry. Power flow and its deposition in the presence of simple material shapes are used to illustrate relevant electromagnetic boundary conditions. Various types of applicator design using standing wave and travelling wave structures are discussed with respect to the results on power density, process efficiency and controllability. The problem of measuring and controlling the temperature inside a microwave system is addressed with emphasis on the use of thermocouples and infrared thermometry. Some of the problems peculiar to high temperature processing are considered. A review of the dielectric and magnetic property variation with temperature and frequency is given in order to understand the complexity and difficulty of uniformity of heating even with microwaves. The use of combination processing, for example, microwaves and infrared heating, is discussed. A short bibliography is presented listing some important publications in the field.
Compositional Control of Ceramic Microstructures: An Overview
Authors: Harmer M. P. , Chan H. M. , Smyth D. M. 
Published: March 2011

AbstractA review is given of the controlled use of compositional variation in the sintering of ceramics. The difficulties in determining the mechanisms of operation of sintering additives are outlined and the mechanistic approaches for studying the subject are described. Important remaining issues, new developments and opportunities for developing unique ceramic microstructures through the controlled use of compositional variation are described. Attention is focused on lattice defects and grain growth inhibition, particle pinning, multiple doping, anion effects, anisotropy effects, scavenging, surface diffusion and the formation of wavy grain boundaries.
Fabrication Reliability of Ceramics: Controlling Flaw Populations
Authors: Lange F.F. 
Published: March 2011

AbstractThe major hindrance in using structural ceramics in well defined engineering applications is their lack of reliability caused by uncontrolled flaw populations introduced during fabrication. Mechanical reliability is thus a matter of fabrication reliability. The strengthening that can be achieved by either eliminating or reducing the size of flaw populations through changing either processing or microstructure will be reviewed.
New and Old Ceramic Processes: Manufacturing Costs
Authors: Rothman E.P. , Bowen H.K. 
Published: March 2011

AbstractRecent advances in the property and performance requirements of ceramics have stimulated new approaches to ceramics processing. One approach being studied in numerous laboratories around the world involves the introduction of specialty chemicals to the sequential processing steps. Because many of these new approaches involve changes in equipment, raw materials, and processing variables, this paper focuses on an examination of the process economics. In some instances we can project the costs for these new technologies by considering the costs of similar commercial processes.
Atomic Resolution Studies of Tilt Grain Boundaries in NiO
Authors: Merkle K. L. , Reddy J. F. , Wiley C. L. , Smith David J. , Wood G. J. 
Published: March 2011

AbstractThe atomic structures of a number of <001> high-angle tilt grain boundaries in NiO have been studied by high-resolution electron microscopy (HREM). Crystal 1inity is always maintained right up to the grain boundary (GB). Grain boundary planes bounded by a (100)-plane are preferred, however symmetrical facets are also found at each misorientation. A tendency to match atomic planes across the GB is not only observed in symmetrical, but also in asymmetrical GBs. Structural units can be clearly recognized in symmetrical GBs. Contrast differences suggest that a multiplicity of structural units exists for some GB configurations. Frequently symmetric GBs also show deviations from mirror symmetry. Multislice simultations indicate that the image contrast associated with HREM GB images is not particularly sensitive to GB relaxation.
Electrical Conductivity and Seebeck Coefficient of Divalent-Metal-Doped YCrO3
Authors: Weber W. J. , Bates J. L. , Griffin C. W. , Olsen L. C. 
Published: March 2011

AbstractThe substitution of divalent metal ions for γ(+3) in γCrO3 results in a charge compensating transition of Cr(+3) to Cr(+4) and the formation of small polarons as charge carriers. The experimentally measured electrical conductivity, σ, and Seebeck coefficient, S, exhibit behavior consistent with a theoretical model developed for small polaron transport in these narrow-band semiconductors. The small polaron transport is a thermally-activated process with a measured activation energy, E, of about 0.18 to 0.25 eV in these materials. Both σ and S increase with temperature and show a near linear dependence on dopant concentration and a strong dependence on dopant (ionic) size. Analysis of the results in terms of the model indicates that Ca is much more effective in polaron formation than any of the other dopants in γCrO3; this is due to the similar ionic size of Ca(+2) and γ(+3) which minimizes the lattice distortion from substitution.
The Study of the Formation and Growth of Ni-Al Spinel Using a New, Thin-Film, Specimen Geometry
Authors: Simpson Y. Kouh , Carter C. B. 
Published: March 2011

AbstractThe formation of nickel-aluminate spinel during the reaction between nickel oxide and alumina has been studied by a new approach which utilizes a thin-film substrate of alumina. It is found that the spinel grows in either near- or exact-topotactic alignment along the edges of the thin-film substrate. It also grows on and into the surface of the substrate, but the deviation from exact topotaxy then tends to be larger. The topotactic relationship is such that the (0001) of the alumina is parallel or nearly parallel to the {111} planes of the spinel with <1100> parallel to <110>. A second orientation relatioship is found where the {1120} of the alumina is parallel or nearly parallel to the {111} planes of the spinel; <1100> is again parallel to <110>. First order twin boundaries are found to be common in the spinel particles which have grown on the edge of the thin alumina substrate. Direct observation of the change in the orientation of the spinel twins with respect to the alumina substrate after reannealing is reported. The morphology of the various types of spinel particles is discussed briefly.
Probability of Detection of Internal Voids in Structural Ceramics Using Microfocus Radiography
Authors: Baaklini George Y. , Roth Don J. 
Published: March 2011

AbstractThe reliability of mlcrofocus x-rad1ogrphy for detecting Internal voids 1n structural ceramic test specimens was statistically evaluated. The micro-focus system was operated in the projection mode using low x-ray photon energies (≤;20 keV) and a 10 μm focal spot. The statistics were developed for Implanted Internal voids 1n green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Statistical results are given as probability-of-detection curves at a 95 percent confidence level for voids ranging in size from 20 to 528 μm in diameter.
Calculated Impurity Segregation at the Surfaces of α-Al2O3
Authors: MacKrodt W. C. , Tasker P. W. 
Published: March 2011

AbstractAtomistic lattice simulations are reported of the segregation of yttrium at the {0001}, {1010} and {0112} surfaces and magnesium at the {0001} surface of α-Al2O3. Equilibrium coverages are deduced from the calculated enthalpies of segregation on the basis of a non-Arrhenius isotherm. For magnesium the calculated enthalpy of segregation at low coverage, ∼158 kJ mole−1, is in good agreement with a measured value of ∼146 kJ mole−1 reported recently.
Ceramics and Ceramic Composites: Opportunities and Cooperative Research Modes
Authors: Wachtman John B. 
Published: March 2011

AbstractCeramics and ceramic composites are a rapidly evolving category of materials capable of being tailored to have unique combinations of electrical, optical, mechanical, and chemical properties that make them essential and irreplacable in many engineering applications. Conventional ceramics have both enabled and enhanced many important aspects of our modern technological society; the next generation of ceramics will play a further enabling role for still higher performance devices.A briefing panel of the National Academies of Science and Engineering recently identified four areas into which promising research areas for advanced ceramics can be grouped:
1.New thin films and layer structures with improved properties.2.Exploration of completely new, multicomponent ceramic crystal structures and composites.3.The mechanical behavior of ceramics and tough composites.4.Ceramic processing of large parts and assemblies.Three mechanisms for achieving critical mass in ceramics research were recommended:
1.University/industry programs.2.A summer institute.3.A large interdisciplinary center.
Interaction of Copper With Single Crystal Sapphire
Authors: Schrott A. G. , Thompson R. D. , Tu K. N. 
Published: March 2011

AbstractThe effect of small coverages of Cu evaporated in ultra-high vacuum (UHV) on A12O3 (0001) surfaces has been investigated by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). These surfaces were cleaned either by annealing at 1000°C in O2 or by Ar sputtering. They differ both in their initial state and their interaction with Cu. The XPS spectra from as-deposited Cu on sputtered samples exhibit small shifts in the energy location of the various peaks as compared to those from a Cu standard. Annealing the Cu/sputtered A12O3 structure at 500°C produces a shoulder on the Cu 3d peak as well as a new Cu (L3 M4.5 M4.5) Auger feature. Neither of these effects are observed after similar treatment of the Cu/annealed A12O3 structure. An influence of this different bonding situation on the Cu-sapphire interfacial energy is observed.
High Temperature Studies with Co2 Laser Heated Sapphire: Reactivity and Surface Structures
Authors: Abrevaya Hayim , Nordine Paul C. 
Published: March 2011

AbstractCO2 Laser heating of c-axis sapphire filaments was used in a low pressure flow reactor in order to study evaporation and chlorination of single crystal and liquid aluminas. Reacted specimens were examined by scanning electron microscopy (SEM) to monitor the evolution of facets and other surface structures with reaction conditions.An increase of the incident energy on a laser heated sapphire filament at the melting point does not result in complete melting, because the semi-transparent melt layer that forms has a higher effective emittance than the solid. This technique allows simultaneous reactivity study of liquid and single crystal aluminas at the melting point, as well as study of reactions of single crystal alumina at lower temperatures.Sapphire specimens develop a hexagonal prism shape after reaction with chlorine containing gases whereas evaporation does not change the initially cylindrical specimen shape.The primary structural characteristic of the 0.025 cm as-received sapphire specimens from Tyco is the presence of ∼1μm voids that are produced during the growth of the crystal. These voids form conical arrays 20–30μm apart along the filament axis. Specimens reacted with chlorine containing gases below ∼1900K exhibit surface structures which form arrays with the same size and pattern as the voids in the as-received specimens.
Characterization of Sputter Deposited Al-Nitride And Al-Oxide by X-Ray Photoelectron Loss Spectroscopy
Authors: Kubiak Charlene J.G. , Aita Carolyn Rubin , Tran Ngoc C. , Barr Tery L. 
Published: March 2011

AbstractThe results of an x-ray photoelectron loss spectroscopy (XPLS) study of several wide band gap aluminum compounds are presented here. XPLS is a new application of x-ray photoelectron spectroscopy involving the determination of the energy separation, ΔE, between a particular core photoelectron peak and its principal loss peak. The materials investigated here are sputter deposited thin film Al-nitride and oxide, and bulk single crystal α-alumina. It is not possible to distinguish between these materials on the basis of the chemical shift in the binding energy of the A12p and A12s photoelectrons (Siegbahn shift). The results show that XPLS can be used to distinguish between these materials. ΔE in Al-oxides and nitride differs by several eV and is independent of sample charging. Comparison with ΔE calculated using a free electron gas model is made and related to the plasmon nature of ΔE.
Electrodiffusion of Ions in Alpha-Quartz
Authors: Lopez Augusto R. , West J. D. , Martin J. J. 
Published: March 2011

AbstractElectrodiffusion (sweeping) is a post-growth treatment which allows the selective exchange of charge compensating intersititial ions in quartz. This technique is employed commercially to enhance the radiation hardness of the material used for precision oscillator crystals. Most as-grown quartz contains substitutional Al3+ with an interstitial alkali providing the charge compensation. Additional unidentified sites also trap protons to form the OH--growth defects responsible for several IR absorption bands. When thermally released from their trapping sites, the intersitials can migrate along the large c-axis channels. Therefore, if the sample is heated with an electric field applied along the c-axis, the ions can be swept out and replaced either by protons from the surrounding atmoshpere or by the desired alkal i from a salt electrode. In order to better understand the electrodiffusion, we are systematically investigating various aspects of the process. The apparent ionic conductivity data taken as the swept sample is cooled usually shows a curved log( T) vs 1000/T plot. The conductivity of H+ in is much less than that of the lithium or sodium. The activation energies at high temperatures tend to be lower than those found from the low temperature data. The exponential prefactors are considerably larger than the values predicted for a given aluminum content and reasonable estimates of the attack frequency and jump distance. It seems likely that an additional source of mobile ions is present. The peak or plateau observed during the warm-up period for air or hydrogen sweeping appears to be caused by the transition from conduction primari1y by a1ka1i s to conduction by protons.
Inhomogeneous Sintering: Stresses, Distortion and Damage
Authors: Evans A.G. 
Published: March 2011

AbstractHeterogeneities in a sintering compact constitute a source of stress and distortion. Procedures for calculating the stresses and the distortion are described. Specific trends in the stress with initial differentials in density or particle size and with temperature are then discussed. Some effects of non-sinterable heterogeneites (hard agglomerates or whiskers) on sintering retardation are also analyzed. Finally, some remarks concerning sintering damage are presented.
Strain Rate Effects on the Tensile Strength of Concrete as Predicted by Thermodynamic and Fracture Mechanics Models
Authors: Reinhardt Hans W. 
Published: March 2011

ABSTRACTModels are presented and discussed which predict the influence of stress rate or strain rate on the tensile strength of concrete. Three of them are based on linear fracture mechanics and two on thermodynamics. It is shown that four models are appropriate and useful in the low to medium stress rate whereas two can predict realistic values at high stress rates. Finally a proposal is made how to apply the knowledge to engineering practice.
Compressive Strain Rate Effects of Concrete
Authors: Bischoff P. H. , Perry S. H. 
Published: March 2011

ABSTRACTSince good constitutive laws are required to model correctly the behaviour of concrete under impact loading, it is necessary to determine the complete stress-strain response of concrete at varying strain rates. Conflicting evidence emerges about whether the critical compressive strain (defined as the strain observed at maximum stress) increases or decreases with an increasing strain rate. In this paper, a comprehensive description is given of the brittle fracture process for plain concrete under static and impact loading. The strain rate dependance of tensile microcrack growth is used to explain both the increase in strength and the increase in critical compressive strain that can occur at high strain rates. More extensive experimental results are required to determine the fundamental changes in behaviour that occur as the loading rate is increased and, thus, facilitate the development of a more precise failure model for concrete.
Concrete and Fiber Reinforced Concrete Subjected to Impact Loading
Authors: Shah Surendra P. 
Published: March 2011

ABSTRACTDespite its extensive use, low tensile strength has been recognized as one of the major drawbacks of concrete. Although one has learned to avoid exposing concrete structures to adverse static tensile load, these cannot be shielded from short duration dynamic tensile stresses. Such loads originate from sources such as impact from missiles and projectiles, wind gusts, earthquakes and machine vibrations. The need to accurately predict the structural response and reserve capacity under such loading has led to an interest in the mechanical properties of the component materials at high rates of straining.One method to improve the resistance of concrete when subjected to impact and/or impulsive loading is by the incorporation of randomly distributed short fibers. Concrete (or Mortar) so reinforced is termed fiber reinforced concrete (FRC). Moderate increase in tensile strength and significant increases in energy absorption (toughness or impact-resistance) have been reported by several investigators in static tests on concrete reinforced with randomly distributed short steel fibers. A theoretical model to predict fracture toughness of FRC is proposed. This model is based on the concept of nonlinear elastic fracture mechanics.As yet no standard test methods are available to quantify the impact resistance of such composites, although several investigators have employed a variety of tests including drop weight, swinging pendulums and the detonation of explosives. These tests though useful in ascertaining the relative merits of different composites do not yield basic material characteristics which can be used for design.The author has recently developed an instrumented Charpy type of impact test to obtain basic information such as load-deflection relationship, fracture toughness, crack velocity and load-strain history during an impact event. From this information, a damage based constitutive model was proposed. Relative improvements in performance due to the addition of fibers as observed in the instrumented tests are also compared with other conventional methods.
The Fracture of Reinforced Concrete under Impact Loading
Authors: Bentur Arnon , Mindess Sidney , Banthia N. 
Published: March 2011

ABSTRACTThe behaviour under impact loading of concrete beams, reinforced with both smooth and deformed steel reinforcing bars, was studied. Tests were carried out using an instrumented drop-weight impact apparatus, with a 345 kg mass hammer, and drop heights of up to 2.36 m. It was found that, under certain circumstances, the steel reinforcement itself fractured. This behaviour is discussed with reference to the drop height, the type of reinforcement, and the strength of the concrete matrix.