bluuebunny/crossref_metadata_2025_split huggingface dataset:
Color Centers in Glass Optical Fiber Waveguides
Authors: Friebele E. J. , Griscom D. L. 
Published: March 2011

ABSTRACTColor centers formed in the core and cladding of optical fiber waveguides by exposure to nuclear radiation can greatly increase the attenuation in the infrared spectral region of interest for optical communications. The radiation-induced paramagnetic defect centers in pure silica, silica doped with Ge, P, or B, and heavy metal fluoride glasses have been identified and thoroughly characterized by electron spin resonance (ESR) techniques. This paper will review the results of recent studies of color centers in optical fiber waveguide materials and their Identification via correlations of the radiation-induced optical absorptions and defect centers elucidated by ESR.
Topological Origin of the Surface Singularities in Glasses
Authors: Kerner Richard 
Published: March 2011

ABSTRACTA model of CRN in two dimensions is presented, composed of equilateral but not equiangular polygons with a constant coordination number = 3; in a simplified version only pentagons, hexagons and heptagons are present in the network. We introduce the mean potential energy per atom averaged over a typical cell containing three adjacent polygons; we assume that although the thermal equilibrium is not attained for single atoms, it is attained on the level of these cells, so that we can apply the virial theorem for the cells. Then we minimize the free energy which contains the configuration entropy contribution. In terms of two variables P and δ (hexagon frequency and mean bond angle deviation) we get the surfaces of constant energy. Under stress the energy configurations cease to be one-connected, and the 0-th homotopy group is no more trivial. This can give rise to surface singularities (cracks).
The Structure of SiO2-Sol-Gel Glasses Produced from Gels with Various Mole-Water per Mole-TEOS Ratios
Authors: Kordas George 
Published: March 2011

ABSTRACTSiO2-gels produced with 4,8, and 16 mol water per mol TEOS were densified up to 1000°C and then exposed to gamma-ray irradiation in order to produce paramagnetic defect centers. Various paramagnetic states were detected during densification of these gels, the formation of which depends on the mol water per mol TEOS ratio. In the gels O−2 ions were detected. The paramagnetic centers detected in the n = 16 gel with TH = 900°C were attributed to a non-bridging oxygen and an E'1-center. Three different O−2 ions, probably in interstitial positions, were detected in the n = 16-gel with TH = 1000°C. The CO−2 center was observed in the n = 8 gel with TH = 900°C. A variety of new components occur at TH = 1000°C in the n = 8 gel, the origin of which remains unresolved at present. The CH3, CO−2, and E1′-centers were detected in the n = 4 gel with TH = 700°C. The CO−2 and E′1 centers were preserved after heat treating the n = 4 gel at TH = 1000°C.
Materials by Design – a Hierarchical Approach to the Design of New Materials
Authors: Eberhardt James J. , Hay P. Jeffrey , Carpenter Joseph A. 
Published: March 2011

ABSTRACTMajor developments in materials characterization instrumentation over the past decade have helped significantly to elucidate complex processes and phenomena connected with the microstructure of materials and interfacial interactions. Equally remarkable advances in theoretical models and computer technology also have been taking place during this period. These latter now permit, for example, in selected cases the computation of material structures and bonding and the prediction of some material properties. Two assessments of the state of the art of instrumental techniques and theoretical methods for the study of material structures and properties have recently been conducted. This paper will discuss aspects from these assessments of computational theoretical methods applied to materials. In addition, an approach will be presented which uses advanced instrumentation and complementary theoretical computational techniques in tandem in an effort to construct and verify hierarchies of models to translate engineering materials performance requirements into microscopic-level and atomic-level materials specifications (composition, structure, and bonding). Areas of practical interest include catalysis, tribology (contacting surfaces in relative motion), protective coatings, and metallurgical grain boundaries. A first attempt involving modeling of grain boundary adhesion in Ni3Al with and without boron additions will be discussed.
Computer Simulation of Sputtering from Two Component Liquid Metal Targets
Authors: Shapiro M. H. , Lo D. Y. , Tombrello T. A. 
Published: March 2011

ABSTRACTThe sputtering of In and Ga atoms from a “liquid” target composedof gallium coveredby a surface monolayer of indium by incident 5 keV Ar+ ions was simulated using the multiple interaction molecular dynamics technique. Yields, energy distributions, and angular distributions of sputtered atoms were obtained at a temperature above the melting point for the eutectic alloy. Similar information was obtained for a pure gallium and a pure indium target. Our results for layer yield ratios and angular distributions are in good qualitative agreement with Dumke's experimental data for the Ar+, In-Ga system. Absolute yields, however, were found to be sensitive to the detailed nature of the two-body potentials used to describe the atom-atom interactions.
Dynamics of Compressed and Stretched Liquid SiO2, and the Glass Transition
Authors: Angell C. A. , Cheeseman P. A. , Phifer C. C. 
Published: March 2011

ABSTRACTIon dynamics simulations are presented to model the system SiO2over wide ranges of temperature and density as it passes from liquid into glassy states. Essential features of the diffusive mechanism by means of which the system configuration space is explored are examined in relation to density and structure. The presence of a water-like density maximum in the liquid state of this system is established by using the negative pressure regime to stretch the system and thereby sharpen the phenomenon.
Crystal. Liquid and Glass in 2 Dimensions. Analysis of the glass Transition
Authors: Lançon Frédéric , Chaudhari Praveen 
Published: March 2011

ABSTRACTA molecular dynamics technique has been used to simulate the melting of a 2-dimensional diatomic crystal and to quench the liquid phase to a solid phase. We demonstrate that a 2-dimensional dense amorphous structure can be obtained and that a 2-dimensional glass transition does exist. Furthermore, atomic vibrations in the liquid can be separated from motion produced by diffusion. The relaxation time during which atoms have a vibratory motion but do not diffuse, diverges to infinity near the observed glass transition. Because of the 2-dimensionality. we are able to display the microscopic processes associated with the glass transition.
Three Dimensional Characterization of Interfaces in Semiconductors by Scanning Electron Microscopy
Authors: Joy David C. , Maher D. M. , Farrow R C 
Published: March 2011

AbstractIn many semiconductor materials problems, structural characterizations must be achieved in both the lateral and vertical dimensions. Although a combination of cross-sectional and planar transmission electron microscopy can provide this information, the sample preparation time is demanding and only relatively small volumes of material are examined. We describe here an alternative approach in which the charge collection (‘CCM’) imaging mode of the scanning electron microscope (SEM) is used. It is shown that, by varying the incident electron beam energy, electricallly active defects at different positions beneath the entrance surface of the material can be imaged and their depth estimated.
Raman Scattering Study of Mixing of GaAs/AlAs Superlattices by Ion Implantation and Rapid Thermal Annealing
Authors: Kirillov D. , Ho P. , Davis G. A. 
Published: March 2011

AbstractRaman scattering was applied to study mixing of GaAs/AlAs superlattices. Different implantation ions and doses were used. The evolution from partially amorphous to completely amorphous and from partially mixed to completely mixed structures was observed. Rapid thermal annealing caused recrystallization of the damaged material. Different types of structures were obtained, depending on the implantation doses and species of ions. Completely mixed crystalline alloys could be obtained only for high implantation doses.
Micro-Tomography Using Synchrotron Radiation
Authors: Johnson Quintin C. , Kinney John H. , Bonse Ulrich , Nichols Monte C. , Nusshardt Rudolf , Brase James M. 
Published: March 2011

AbstractThis paper discusses the results of recent experiments at Stanford Synchrotron Radiation Laboratory (SSRL) and Hamburger Synchrotronstrahlungslabor (HASYLAB) which were designed to explore the feasibility of using synchrotron radiation in high-resolution, computerized, critical-absorption tomography. The results demonstrate that it is possible, using absorption-edge differencing, to identify adjacent elements in the periodic table with high sensitivity. Furthermore, by using the fine structure in the absorption spectra, it is possible to distinguish between regions of different chemical states. Methods of using synchrotron radiation for high-resolution, three-dimensional chemical-state mapping in small samples are discussed.
Analysis and Comparison of EL2 Concentration and Stress Distribution in Undoped LEC-Grown Semi-Insulating GaAs Ingots
Authors: Dobrilla P. , Blakemore J. S. 
Published: March 2011

AbstractNear-IR absorption mapping has been used for polished GaAs wafers (0.5 mm thick) cut at intervals along the seed-to-tail length of (100)-oriented LEC-grown semi-insulating (SI) ingots. Some 2000 points are measured, point by point, over a wafer's area, usually near 1.0 μm for EL2 mapping, and near 1.4 μm for observation of stress interferograms. For the results presented here (high pressure LEC crystals from a major commercial supplier), stress maps display the fourfold symmetry predicted in thermoelastic models. The EL2 maps do not necessarily display the same symmetry, especially for wafers from near the tail end of an ingot.
Raman Spectroscopy for Semiconductor Thin Film Analysis
Authors: Nemanich R. J. 
Published: March 2011

AbstractThe application of Raman spectroscopy to various semiconductor thin film, interface and surface problems will be presented. Specific focus will be on the vibrational excitations of the materials systems which are probed by the Raman measurements. Experimental configurations are described which are optimized for general thin film analysis, microprobe analysis, and in situ UHV surface/interface analysis. The vibrational properties can be used for phase and composition identification, crystal/amorphous structure, strain, impurity configurations, and superlattice properties. Specific examples will include thermal processing of CVD Si films, microprobe of laser annealed films, MOCVD AlxGa1−xAs films, silicide formation and identification, amorphous superlattices, and hydrogen impurities in crystalline Si.
Optimizing the Depth Resolution of Rutherford Backscattering Through Modeling of Noise Sources
Authors: Abelson John R. , Sigmon T. W. 
Published: March 2011

AbstractGrazing angle configurations improve the depth resolution of Rutherford Backscattering Spectrometry (RBS) because the path length of scattered particles is geometrically increased. But in the limit of very grazing angles the resolution degrades due to the finite detector acceptance angle and low angle forward scattering of the beam, considerations which are not present in near-normal incidence geometries. The forward scattering, for example, worsens the depth resolution approximately as the square of the depth, rather than the familiar square root dependence of energy straggling. We present a simple computational scheme which predicts the depth resolution in any target as a function of scattering depth, beam energy, and the grazing angle. The calculations are simpler than previous studies because we use analytic expressions in place of numerical inputs without loss of accuracy. The results lead directly to an optimum depth resolution. We find good agreement between the predicted resolution and measurements on thin silicon dioxide and amorphous silicon films. Finally, we calculate the resolution expected with the use of ion beams heavier than He+, and find improved near surface depth resolution if a low noise detector is used.
Investigation of Metal/GaAs Reactions by Heavy Ion Rutherford Backscattering Spectrometry(HIRBS)
Authors: Yu Kin Man , Jaklevic J. M. , Haller E. E. 
Published: March 2011

AbstractThermally activated metallurgical reactions between GaAs and various metals of potential importance in contact structures were studied using Heavy Ion Rutherford Backscattering Spectrometry (HIRBS). The improved mass resolution obtained with heavy ions (160) as projectiles for backscattering measurements facilitated the identification of the various intermetallic compounds formed on GaAs. The metal/GaAs systems investigated in this study included Pt/GaAs, Pd/GaAs, and Ni/GaAs. Three different binary compounds were formed in the Pt/GaAs system during annealing. Complete reaction between 1200Å of Pt and GaAs was observed after annealing at 500°C for 20 min. Reactions in Pd/GaAs and Ni/GaAs systems were, however, very different from that of Pt/GaAs. Both Pd and Ni formed ternary compounds with GaAs. Detailed information on the various compound compositions of the three systems as measured by HIRBS is presented. Comparisons of results on similar systems obtained by using other analytical techniques are discussed.
Deviations from Bragg's Rule for the Stopping Cross Sections of Deuterium in Titanium and Zirconium Deuteride Films
Authors: Borders J. A. 
Published: March 2011

AbstractThe ratios of the stopping cross sections of deuterium ions in titanium and zirconium deuteride films to those in the pure metals have been determined at incident deuteron energies from 300 keV to 2.0 MeV. These ratios are evaluated from measurements of the yields of deuteron elastic scattering in the deuteride films and in films of the pure metals. Although the absolute stopping cross sections cannot be evaluated from the measurements, use of the Brice yield equation allows the ratios of the cross sections in the deuterides to those in the pure metals to be determined. Significant deviations from Bragg's rule are found and these results are in general agreement with recent measurements at lower deuteron energies (40–200 keV). These measurements represent some of the largest deviations from strict additivity of stopping powers yet observed.
Numerical Analysis of Transient Capacitance Data Obtained from Titanium Induced Levels in Silicon
Authors: Courcelle E. , Mesli A. , Siffert P. 
Published: March 2011

AbstractUsing electrical and optical DLTS analysis based on the capacitance transient measurements and taking into account the spatially dependent capture and the competition between emission and capture, parameters of Titanium levels in silicon are derived. By curve fitting the calculation to trap-filling data, the electron capture cross section of the first donor level (Ec - .284 eV) is found to be 5.8 10-15 exp (.013/kT)cm2 at ξ= 5 104 V/cm. The hole trap capture cross section of the second donor level (Ev + .260 eV) is found to be 1.97 10-17exp (-.017/kT)cm2 at zero electric field.
Material Characterization by Contactless Photoconductivity Measurements
Authors: Kunst M. , Werner A. 
Published: March 2011

AbstractTransient photoconductivity measurements with the time-resolved microwave conductivity (TRMC) method have been applied to three different types of semiconductors: hydrogenated amorphous silicon, single crystalline silicon and GaAs/GaAlAs multiple quantum well structures. Analysis of the signals in terms of charge carrier-lattice interaction points to an intimate relation between TRMC signals and intrinsic material properties. It is shown that the TRMC-technique is an excellent tool to characterize photosensitive materials.
Determination of the Dislocation Network Density in GaAs Using Thermal Wave Microscopy
Authors: Brandes Anita G. , Tang Chwan , Fillmore Charles 
Published: March 2011

AbstractThe pattern and density of dislocations in GaAs is thought to affect the ultimate performance of finished devices. Previous studies of dislocation networks have usually involved molten KOK etching of GaAs wafers or X-ray topography. A relatively new technique, Thermal Wave Microscopy (TWM), offers an alternative method of analysis. High frequency blanking of the scanning electron beam in an SEM produces thermal waves that propagate approximately 1–2 wavelength through a sample, are then carried by thermoacoustic waves and detected by a piezoelectric transducer. Dislocations, microcracks, and voids will disturb this wave and the resulting image will show a change in contrast (bright or dark) at the defect site. Resolution is dependent on the thermal properties of the material being analyzed as well as on the accelerating voltage, beam current, beam blanking frequency and phase of the electron beam. TWMim ages of dislocation networks in as-received GaAs are very similar in appearance to the results of molten KOH etching. TWM is a relatively new technique for microanalysis. Its full range of applications are still being explored. For determination of dislocation networks it is a faster, less cumbersome method of analysis. TWM is a basically nondestructive technique involving none of the uncertainties of molten KOH etching (etch time, etch uniformity). For this reason TWM is recommended as an alternative analytical technique.
Neutron-Induced Particle Track Mapping of Elemental Distributions
Authors: Bild R. W. 
Published: March 2011

AbstractThermal neutrons are captured by several elements which emit charged particles as reaction products. These particles leave etchable damage tracks in detector materials placed against a sample, creating a map of the distribution and concentration of the target element. The most common applications are for trace U using fission fragment tracks and B using alpha tracks. Li, N and possibly S and O can also be determined. We have applied the technique to B in metals and coatings, Li in Al, N in glass and U in O-ring seals. Dectection limits are better than 10−11g/g for U, 10−9g/g for B, 10−6g/g for Li and 0.1 wt % for N. Spatial resolution for mapping is about 25 μm.
Spatially-Resolved Non-Contact Methods for the Investigation of Transport and Defects in Semiconductors
Authors: Amer Nabil M. 
Published: March 2011

AbstractPhotothermal spectroscopy employs the small rise in temperature associated with the absorption of electromagnetic radiation to probe optical and transport properties of materials. A review of the various photothermal detection schemes is given, and examples which illustrate the power of this technique are reviewed.
Nanomechanics of Thin Films
Authors: Hoffman R. V. 
Published: March 2011

AbstractRecognition of the importance of the mechanical properties of thin deposited films has received increasing attention over the past decade. The film or near surface region must be treated as a material to understand its particular mechanical properties in terms of the unique microstructure present. A vapor condensed film often has an extremely small grain size and gives brittle behavior. It is not uncommon to form an impurity stabilized amorphous film during growth.In this paper emphasis is placed on concepts and recent instrumentation for measurements of the stress during film deposition. This growth stress and its distribution results from the microstructure plus the mechanical constraints of the underlying material, and may be modified by the processing. Both elastic and plastic components are present and local deformation maps allow a reasonable level of modelling. Lacking in this approach are experimental material parameters for the film, near surface, or interfacial material. New data for the tensile properties of cast polystyrene and SiO films is presented.
On The Melting of Amorphous Ge and Si
Authors: Turnbull David 
Published: March 2011

ABSTRACTThe amorphous semiconducting phase (a-sc) of Si or Ge is so resistant to crystallization that rapid heating may bring it into a temperature regime in which it melts. Such melting might occur in one or the other of two ways, either homogeneously, by the reverse of the glass transition, to a viscous semi-conducting melt (ℓ-sc) or by transition, probably by nucleation and growth, to the molten metallic state (ℓm). Using the self-diffusion constant of the crystalline elements in conjunction with the Stokes-Einstein equation, upper limiting values of the glass transition (a-sc→ℓ-sc) temperatures of Si and Ge were calculated. These were of the order 0.6 to 0.65 Tcℓ for slow and 1.1 Tcℓ for ultra rapid heating, where Tcℓ is the equilibrium melting temperature of the crystal. Arguments are given that superheating to a temperature 1.15 to 1.25 Taℓ (a-sc↔ℓm in equilibrium at temperature T = Taℓ< Tcℓ) may be required for copious internal nucleation of im in a-sc. At lesser superheating the transition must be initiated at internal flaws (e.g. voids) or at the external surface of the a-sc film. Therefore the superheating at perceptible onset of the transition during rapid heating can vary widely from specimen to specimen, depending on the flaw concentration and how the external surface of a-sc was treated.
Metastable Solid Solutions of Impurities in Silicon
Authors: Williams J. S. , Short K. T. 
Published: March 2011

ABSTRACTHigh resolution Rutherford backscattering and channeling techniques have been used to investigate the formation and stability of supersaturated solid solutions of As, Sb, In, Pb, Tℓ and Bi implants in (100) silicon. In all cases nearsubstitutional solid solubilities far exceeding maximum equilibrium solubility limits can be achieved by furnace annealing at temperatures ≤ 600°C. Details of the recrystallisation process indicate that the maximum impurity concentration which can be incorporated onto silicon lattice sites may be controlled by impurity size and associated strain effects at the amorphous-crystal boundary during epitaxial regrowth.
Precipitation Phenomena in Implanted Ionic Oxide MgO
Authors: Perez A. , Treilleux M. , Thevenard P. , Abouchacra G. , Marest G. , Fritsch L. , Serughetti J. 
Published: March 2011

ABSTRACTMgO single crystals implanted with alkali ions (Li+, Na+, K+ and Rb+),Fe+, In+ and Au+ ions have been studied after implantation with doses up to 1017 ions.cm−2 and after annealing at temperatures up to 1100°C.In order to characterize defects and precipitated phases, several techniques have been associated depending on the implanted ions : optical absorption, transmission electron microscopy, Rutherford backscattering spectrometry, conversion electron Mössbauer spectroscopy and X-ray diffraction at oblique incidence. Directly after implantation the intrinsic defects in the anionic sublattice (F, F+, F2-centers) and in the cationic sublattice (V−-centers) are observed. As to the implanted species, two precipitation processes are observed : (i) the implanted ions precipitate independently of the matrix elements. This is the case of alkali ions which form alkali metal precipitates. (ii) the implanted species precipitate with those of the matrix to form compounds. This is observed with iron which forms oxide precipitates and spinel ferrite. In the case of indium and gold, the precipitation process occurs with the cations of the matrix to form binary alloys : Mg3In and Au3Mg.