bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsed Laser Annealing of Al, Ni, and MgO Containing Nickel Precipitates
Authors: Narayan J.
Published: March 2011

We have investigated the generation of point defects and dislocations, and the formation of dislocation loops as a function of pulse energy density in laser annealed Al, Ni, and MgO containing nickel precipitates. In the case of Al where vacancies are mobile above 200 K, mostly vacancy loops were observed at room temperature in laser melted layers. Dislocations are formed below the laser-melted layers as well as in specimens treated with pulses below the melting threshold, due to thermal stresses. In the case of Ni (where vacancies are mobile above 373 K) the microstructure in room temperature laser annealed specimens consists of primarily dislocations and their tangles. In MgO:Ni crystals, enough laser energy was absorbed to melt nickel precipitates. The dislocation structure around the precipitates and the transformation of nickel precipitates from coherent into incoherent, provided information on melting and crystal growth of these precipitates.
Defects and AlSb Precipitate Nucleation in Laser Irradiated Aluminum
Authors: Peercy P. S. , Follstaedt D. M. , Picraux S. T. , Wampler W. R.
Published: March 2011

Lattice defects and precipitates induced in unimplanted and Sb-implanted <110> single crystal Al by single pulse irradiation with a Q-switched ruby laser were studied using ion beam analysis and electron microscopy. The absorbed laser energy during irradiation is directly measured in these studies to allow precise numerical modeling of the melt times and temperature profiles. For unimplanted Al, slip deformation gives rise to increased channeled yields throughout the analyzed depth and occurs for energies well below the melt threshold energy of 3.5 J/cm2. Slip deformation is also observed for irradiation energies above the melt threshold energy, and melting is accompanied by a discontinuous increase in the minimum channeling yield, X min- Implanted Sb (to ∼2 at.% peak concentrations) is found to impede epitaxial regrowth and result in polycrystalline Al formation for laser energies such that the melt front is believed not to penetrate through the Sb-containing region. For deeper melt depths, a metastable alloy is formed with up to 35% of the Sb located in substitutional sites. AlSb precipitate formation in the melt was not observed for room temperature irradiations; however, randomly oriented AlSb precipitates are observed for irradiation at substrate temperatures of 100 and 200 °C These measurements yield an estimated time for nucleation of AlSb precipitates in molten Al of 5 nsec < tnuc < 25 nsec.
Pulsed Electron Beam Melting of Fe
Authors: Knapp A. , Follstaedt D. M.
Published: March 2011

Pulsed (50 nsec) electron beams with deposited energies of 1.1 ­ 2.4 J/cm2 have been used to rapidly melt a surface layer of Fe. Calculations show that this range of energies produces melt depths from 0.4–1.2 μm and melt times of 100–500 nsec. Optical microscopy and SEM of pulse treated polycrystalline foils show slip traces, as well as a general smoothing of surface features which shows that melting has occurred. TEM shows that the resolidified material is bcc, and that the material within a grain is epitaxial with the substrate. TEM also shows slip traces of {110} planes, as well as a high density of dislocations, both extended and loop. At the highest energy, subgrain boundaries are observed. Some samples were implanted with 1×1016 Sn/cm2 at 150 keV. After pulse treatment, the Sn depth profile was observed to have broadened, consistent with liquid phase diffusion. The Sn had the unexpected effect of suppressing slip at the sample surface.
Epitaxial Silicide Formation by Scanning Electron Beam Annealing
Authors: Ishiwara Hiroshi , Yamamoto Hiroshi
Published: March 2011

Epitaxial growth of Pd2Si films on Si(lll) substrates by scanning cw electron beam annealing is investigated theoretically and experimentally. First, the nonlinear heat conduction equation is solved in a substrate with finite thickness to estimate the surface temperature during annealing. Then, the optimum growth conditions are experimentally determined, in which annealing parameters such as the beam current intensity, the scan speed, and the overlap width are changed. It has been shown by Rutherford backscattering and channeling techniques that the crystalline quality of the e-beam annealed Pd2Si films is somewhat worse than that of the furnace-annealed films.
Study of Titanium and Nickel Silicide Formation By Q-Switched Laser and Multiscanning E-Beam
Authors: Bentini G.G. , Nipoti R. , Berti M. , Drigo A.V. , Cohen C.
Published: March 2011

The use of Q-switched ruby laser and multiscanning electron beam annealing (MEBA) to produce the reaction of thin Ti and Ni films deposited onto single crystal Si has been studied. Laser annealing produces a reaction at the interface between the metal and the semiconductor; the reacted layers are not uniform in composition and more similar to a mixture than to a well-defined phase. The silicide layers produced by MEBA results from the solid state reaction of whole metal layer and have well-defined compositions and sharp interfaces between phases and the underlying crystal. The observed thicknesses of the silicides produced by MEBA cannot be accounted for by the parabolic volume diffusion mechanism operating in the standard furnace annealing. Post annealing treatments in furnace showed that e-beam produced silicides have the same thermal stability as those produced by conventional heat treatments. The presence of a critical temperature for silicide formation in Ti/Si MEBA annealed samples has been confirmed and studied in detail.
Laser Fabrication of Silicon on Dielectric Substrates
Authors: Leamy H. J.
Published: March 2011

The growth of device-worthy silicon crystals on insulating substrates would have a revolutionary impact upon microelectronics, and is consequently the object of intense effort. This article reviews recent progress in the application of laser and electron beams and incoherent light to this end. In every case, radiant energy is employed to melt a precursor material, from which device-worthy layers are produced during resolidification. Techniques include seeded and unseeded growth, partial and complete encapsulation of the liquid layer, and oscillation of the solid-liquid interface. Considerations of liquid zone stability, temperature gradient control, and interface morphological stability are central to each technique. Progress in this field has been rapid and several techniques have been successfully demonstrated.
Optical Characterization of Chemically Vapor Deposited and Laser-Annealed Polysilicon
Authors: Bagley B. G. , Aspnes D. E. , Celler G. K. , Adams A. C.
Published: March 2011

The optical properties of polysilicon on insulating SiO2 were measured by spectroscopic ellipsometry over the energy range 3.0 to 6.0 eV. Spectra were obtained for films as-deposited and after irradiation with an Ar ion laser (focused to a 50μm spot diameter) at 6.0, 7.0 or 7.5 watts. We observed monotonic changes in both ε1 and ε2 with increasing incident power even though the power density was high enough to completely melt the silicon surface in all cases. The changes observed are caused by changes in microstructure; with increasing power the amorphous component decreases and the density increases. Approximate values of the microstructural components are estimated by comparing measured spectra to those synthesized from constituent spectra in the Bruggeman effective medium approximation.
A Model for Laser Beam Induced Solid-State Crystal Growth in Silicon On Sapphire
Authors: Burgener M. L. , Reedy R. E. , Csanadi O.
Published: March 2011

An analytic model is presented for laser beam induced solid-state crystal growth in silicon on sapphire. The model, which assumes a single activation energy, utilizes temperature profiles calculated from a Green's function solution to the heat equation. Calculated crystal growth in silicon on sapphire is compared to experimentally measured values.
Fast Scan Laser Annealing
Authors: Schott John T.
Published: March 2011

Laser-annealing phenomena have typically been divided into two distinct realms. Pulsed lasers involved very short anneal times and small deposited energy densities. Slowly scanned cw lasers involved intermediate times (ms range) and larger energy densities. Repetitively scanned electron beams have extended the range of anneal time and energy density toward conventional thermal processing. This paper examines the regime between pulsed laser annealing and conventional cw laser annealing. By greatly increasing the scan speed of the laser, annealing times and deposited energy densities are reduced and approach those of pulsed laser annealing. Applications are discussed in the areas of silicon-on-insulator recrystallization, low resistivity poly, vertical integration, local lateral seeding, explosive crystallization, and line-source simulation.
Optical, Structural and Electrical Characteristics of Explosively Crystallized Si Thin Films on Glass Substrates
Authors: Auvert G. , Bensahel D. , Perio A. , Morin F. , Rozgonyi G.A. , Nguyen V.T.
Published: March 2011

Explosive Crystallization occurs in cw laser annealing on a-Si films deposited on glass substrates at laser scan speeds higher than 30 cm/sec. Optical, structural and electrical properties of the crystallized films at various laser scan speeds confirm the existence of two kinds of explosive growth depending on the state of crystallinity of the starting material.
Shaping of Dopant Concentration Profiles in Silicon by Multiple–Pulse Laser Processing
Authors: Hill C , Butler A L , Daly J A
Published: March 2011

Over the past ten years, the performance of bipolar transistors in high speed integrated circuits has been steadily improved by fully exploiting the complex solid state diffusion behaviour of dopants in silicon to make successively closer approaches to the ideal dopant profiles in the emitter and base regions of the transistor. Further optimisation requires a new approach, and in this paper an entirely new method of shaping the dopant profiles by exploiting the large ratio (about 108) of diffusion coefficients in liquid and solid silicon near the melting point is described Melting is effected by irradiation with a homogenised pulse from a Q-switched ruby laser. Completely new features of the technique are the controllable fabrication of both quasi–Gaussian and quasi-rectangular dopant profiles independent of dopant (arsenic or boron), dopant concentration (1013−1016atom cm−2) or presence of other dopants. This allows for the first time independent optimisation of emitter profile shape, emitter doping level, and base profile in bipolar transistor structures.
Characteristics of Interpoly Oxides Optimized by Conventional Processing and Laser Annealing
Authors: Eggermont G.E.J. , Rodeen H.D. , Brors D.L.
Published: March 2011

To improve the dielectric properties of thin oxides grown on polysilicon, a matrix of conventional process variables such as phosphorus doping level and oxide growth temperature, and the inclusion of laser recrystallization of the polysilicon have been investigated. For conventionally processed wafers, highest dielectric strengths were obtained at the highest oxidation temperature (1150°C) and a simultaneous low doping level in the polysilicon. Similarly high dielectric strengths were obtained after cw-Ar laser recrystallization of the polysilicon at much lower temperatures (900°C), independent of the doping level in the polysilicon.
Pulsed–Raman Measurements of Temperature When Large Temperature Variations and Gradients are Present
Authors: Wood R. F. , Rasolt M. , Jellison G. E.
Published: March 2011

Pulsed Raman temperature measurements by Lo and Compaan on Si samples have been interpreted as proving that the surface region does not melt during intense pulsed laser irradiation. In this paper, it is shown by detailed calculations with the melting model that the choice of experimental parameters in the Raman measurements can severely compromise a straightforward interpretation of the data. Moreover, it is demonstrated that temperatures extracted from Raman measurements are highly sensitive to the temperature-dependent optical properties of the material. Finally, it is pointed out that the very large temperature gradients present during pulsed laser annealing may entirely invalidate the Stokes/anti-Stokes ratio as an accurate temperature probe.
Characterization of Laser Induced Backside Damage for Gettering Purposes
Authors: Eggermont G.E.J. , Allison D.F. , Gee S.A. , Ritz K.N. , Falster R.J. , Gibbons J.F.
Published: March 2011

A characterization of Q-switched Nd-YAG laser induced backside damage in various stages of a bipolar process is presented. TEM-analysis shows the occurence of microcracks, low angle boundaries and dislocations in as-irradiated wafers, of which the microcracks anneal out during an initial oxidation at 1050°C. The other damage is very stable and remains even after a heat treatment at 1200°C. This is quite in contrast with mechanically or Ar implantation induced backside damage, which anneal out completely at such high temperatures. Side effects of laser induced backside damage such as surface roughness and influence on wafer strength are found to be of no consequence within a limited range of laser pulse energy densities where the gettering efficiency is found to be very promising.
Pulsed Electron Beam Processing of Silicon
Authors: Greenwald Anton C. , Little Roger G. , Spitzer Mark B. , Wolfson Robert G.
Published: March 2011

Continued study [1] of pulsed electron beam annealing (PEBA) of thin silicon films deposited by LPCVD on silicon substrates has shown that a thin SiO2 interface remains intact during melt. PEBA of ion-implant damage in silicon has been shown to correlate dopant activation with melt depth. Also, PEBA was superior to thermal annealing of ion-implant damage in processing solar cells in some types of polycrystalline silicon material.
Calculations Pertaining to Raman Scattering During Laser Annealing of Ion-Implanted Silicon
Authors: Wood R. F. , Lowndes D. H. , Giles G. E.
Published: March 2011

Compaan and co-workers have reported the results of time-resolved optical experiments on ion-implanted silicon which they claim prove the melting model of pulsed laser annealing cannot be correct. These results concern the rapid onset of a Raman signal after a heating laser pulse, the simultaneous occurrence of a Raman signal and the high reflectivity phase characteristic of molten silicon, and the lattice temperature measured by the Raman Stokes/anti-Stokes intensity ratio. In this paper, we show by detailed numerical calculations with the melting model that there is, in fact, excellent agreement between the results of the calculations and the experimental results reported by Compaan and co-workers.
Studies of Laser Annealed GaAs (100), (110) and (111) Surfaces
Authors: Zehner D. M. , White C. W. , Appleton B. R. , Ownby G. W.
Published: March 2011

The surface regions of (100), (110) and (111) oriented single crystals of GaAs have been investigated by the combine techniques of LEED, AES and RBS subsequent to their irradiation in UHV with the output of a Q–switched, ruby laser (0.15−0.8 J/cm2, 15 × 10−9 sec). Clean surfaces, as determined by AES, were obtained after Ar+ sputtering followed by laser irradiation. LEED observations indicate that the degree of disorder in the outermost surface layers remaining after irradiation depends on the crystal orientation. Although the relative intensities of Ga and As Auger transitions in spectra obtained from sputtered and laser annealed surfaces are similar, the differences in lineshape in these spectra of the M2,3M4,5M4,5 Ga Auger transition indicate that in the laser annealed case there are local regions which are nonstoichiometric. These observations are confirmed by RBS results, and this technique has been used to determine the stoichiometry and to characterize the damage in the subsurface region for all orientations.
Stability of Laser Annealed Contacts on Barium Titanate
Authors: Shukla V.N. , Narayan J.
Published: March 2011

Low resistance Ohmic contacts were produced by evaporating nickel and aluminum films on barium titanate substrates, and subsequently irradiating them with Q-switched ruby laser pulses (λ = 0.694 μm, τ = 15×10−9 s, pulse energy density 1.0 − 1.2 J cm−2). Stability and aging behavior of these contacts were comparable to those of conventional contacts, i.e. flame sprayed aluminum, In-Sn solder, fritted silver and electroless nickel under test conditions (ambient temperatures in air, in boiling water and organic liquids at 150°C, 100 psi).
Rapid Large Area Annealing of Ion-Implanted Si With Incoherent Light
Authors: Lischner D. J. , Celler G. K.
Published: March 2011

We report an extremely rapid and efficient method for annealing ion-implanted wafers by transient irradiation with tungsten halogen lamps. Several 3-inch wafers are held in an inert atmosphere, thermally isolated from the water cooled base and separated by a quartz plate from the air cooled lamps, which can deliver in excess of 100 kW of power. Heating of the wafers up to 1200°C, or even to the melting point of Si, occurs within seconds. The cooling process can be equally rapid. The temperature is continuously monitored with a pyrometer. The radiative flux in the chamber is uniform within 5% over at least 500 cm 2; however, at temperatures 1200 °C radiative losses at the wafer perimeter may cause crystalline slip if proper countermeasures are not taken.
Optimised Multi-Scan H-Beam Annealing Of Mos Devices
Authors: Pollard C J , Glaccum A E , Speight J D
Published: March 2011

The optimum e-beam anneal conditions for damage free wafer annealing, implant activation uniformity across 3 inch wafers and low dose boron activation have been investigated with reference to the needs of MOS device processing. Some effects of e-beam annealing on MOS gate dielectrics are reported.
Glancing Angle X-Ray Analysis of Titanium Copper Compound Formations
Authors: Psaras P. A. , Gupta D.
Published: March 2011

Titanium copper compound formations have been studied via Seeman Bohlin x-ray diffractometry and Rutherford backscattering spectrometry. The heat treatment temperature range was 350°C to 475°C and th heat treatment times ranged from 0 to 240 minutes. Tetragonal gamma TiCu formed first at ˜350°C and was sequentially followed by orthorhombic TiCu3 at ˜400°C. From Rutherford backscattering spectrometry analysis it was concluded that the second TiCu3 compound deviated from ideal stoichiometry to a nonstoichiometric Ti0.88Cu3.12 composition
Polymer-Polymer Interdiffusion
Authors: Kramer Edward J.
Published: March 2011

Interdiffusion of polymer chains plays an important role in establishing good adhesion at polymer interfaces as well as in the kinetics of phase separation and mixing in polymer blends. Reptation, a process in which a given linear chain crawls along a primitive path defined by the topological constraints due to the surrounding chains, is thought to be the most important diffusion mechanism. A reptating chain of Volecular weight M should have a tracer diffusion coefficient given by D =DR =Do M−2, where D depends on the Rouse mobility of the chain and an entang ement molecular weight, Me. Because the topological constraints are assumed to be fixed, DR is independent of the molecular weight P of the polymer into which the M-chains are diffusing. In principle however if M is large enough and P is small enough the M-chain can diffuse by rearrangement of the P-chains surrounding it, a process called constraint release. The D for this process, DCR= αCRDoMe2/(MP3), where αCR is a constant approximately equal to 13, increases strongly with decreasing P. Recent experimental results, which give evidence for both reptation and constraint release, will be reviewed. These results have important implications for the diffusion of nonlinear polymer chains, e.g. stars and rings.
Surface Chemical Studies of Oxides and Nitrides
Authors: Pantano Carlo G.
Published: March 2011

The application of surface analysis techniques for the study of fundamental surface and thin film phenomena is described. The topics covered relate to the processing and fabrication of electronic packages and include: evaporation/condensation during the thermal processing of glasses, hydration of glass surfaces and thin films, nitridation of silica films, diffusion behavior in oxides at low temperature, and impurity segregation in thin films. A wide variety of surface analytical methods are exemplified including Auger electron spectroscopy (AES), ion-scattering spectroscopy (ISS), nuclear reaction analysis (NRA), secondary-ion mass spectroscopy (SIMS) and x-ray photoelectron spectroscopy (XPS).
Ceramic-Metal Interactions
Authors: Klomp J. T.
Published: March 2011

Ceramic-metal interactions are on the basis of a variety of technologies covering the fields of materials production as in ceramic-metal composites and the techniques of joining ceramic to metal. The physics and chemistry of interactions at ceramic-metal interfaces are still the subject of intensive studies not only from a scientific point of view but also for technological reasons because the emergence of new ceramic materials calls for insight into the interactions of these materials with metals. In this paper the mechanisms of ceramic-metal interactions are reviewed against the background of the technology and some extensions of existing interaction models are given.
Eutectic Bonding of Copper to Ceramics
Authors: Wittmer Marc
Published: March 2011

Eutectic bonding of copper to ceramics makes use of a liquid eutectic between copper and oxygen at 1065°C which wets oxide ceramics very well. Upon solidification of the eutectic melt a very strong bond is established which has a strength of about 5×107N/m2. The excellent bond strength gives this technique important applications in electronic packaging and mechanical engineering.
Directly Bonded Copper Metallization of AℓN Substrates for Power Hybrids
Authors: Kluge-Weiss Petra , Gobrecht Jens
Published: March 2011

Aluminum nitride (AℓN) ceramic is emerging as an attractive substrate material for high performance heat sinking in hybrid circuits be -cause of its high thermal conductivity. We report on the application of the direct bonding technique for Cu on AℓN substrates. For successful bonds, the surface of the AℓN has to be oxidized. Oxidation rates are reported and the oxide morphology is analyzed. The peel strength of the Cu sheet depends on oxide thickness, growth method and Cu-type used. Under optimum conditions the peel strength exceeds 50 N/cm. A detailed analysis using optical microscopy as well as SEM, STEM, EDX, and electron diffraction techniques of the AℓN/Aℓ2O3/Cu interface is carried out.
Casting Ceramic-Polymer Sheets
Authors: Shanefield Daniel J.
Published: March 2011

Thin ceramic structures can be efficiently formed by the tape casting process, using a doctor blade for thickness control. A concentrated suspension of the ceramic precursor powder is made in a solvent system, with a polymeric binder, a dispersing agent, and other additives. For high performance ceramic applications, a non-aqueous solvent is generally preferred. The physical chemistry background leading to this choice is discussed, particularly in regard to the competing adsorptions of solvent, dispersant, and binder. Glyceryl trioleate is shown to be a useful dispersant for such systems, allowing dense compacts to be achieved, even with submicron particle sizes. Thus a refractory powder can be fired to nearly theoretical density at practical temperatures.
A Raman Scattering Study of the Temperature Dependence of Boroxol Ring Clusters in B2 O3-GeO2 and B2 O3-GeO2-SiO2 Glasses.
Authors: Chakraborty I. N. , Condrate R. A.
Published: March 2011

This Raman study indicates that the boroxol ring concentrations for glasses in the B2 O3-GeO2 and B2 O3-GeO2-SiO2 systems are dependent upon temperature and composition. Ring breakage and formation occur well below Tg. An Arrhenius plot of intensity data for borogermanate g glass indicates that the heat of ring rupture is ca. 7.7 Kcal/mole. The boroxol ring concentrations in various glasses were also investigated at room temperature after various heat treatments. The structural interpretation from Raman scattering data was compared with that from IR data.
Recent Advances in Huang Diffuse Scattering
Authors: Ehrhart P.
Published: March 2011

Measurements of the diffuse X-ray (or neutron) scattering allow the detailed investigation of point defects in crystalline solids. The method can be applied for defect sizes ranging from isolated point defects up to large dislocation loops. The diffuse scattering intensity close to the Bragg reflections, Huang Diffuse Scattering and Asymptotic Diffuse Scattering, is of special interest as the intensities from lattice distorting defects are high and the scattering theory is most straightforward for this region of the reciprocal lattice. After a short introduction to the theoretical background and to the experimental techniques the capabilities and limitations of the method will be demonstrated with examples of experimental results. i) The structure of interstitial atoms has been investigated for low temperature irradiated crystals and for metals with interstitially dissolved solute atoms. ii) The mobility and growth of interstitial agglomerates during annealing stage II of irradiated metals is discussed. The influence of impurities on the cluster growth is demonstrated for the example of Nibase alloys. iii) Defect clusters and defect distributions within cascades as observed after different types of irradiations are discussed.
The Effect of Adsorbeb Oxygen Ions on the Inelastic Scattering of Photo-Electrons at the Metal-Vacuum Interface
Authors: Pong W. , Brandt D. , He Z. X. , Imaino W.
Published: March 2011

Measurements of uv photoemission from evaporated aluminum films were made at photon energies 7.7–11 eV as a function of time after film deposition. Evidence of the initial stage of chemisorption of oxygen can be seen in the uv photoelectron spectra. The spectra taken immediately after film deposition showed a smooth energy distribution characteristic of clean aluminum. Structure in the spectra was found to appear at approximately 60 minutes after deposition at 10−9 Torr. Three noticeable features were observed at 1.0, 1.3, and 2.5 eV above the vacuum level. They appeared stationary with increasing photon energy. The structure can be attributed to inelastic scattering of photoelectrons into resonant states associated with oxygen ions on the metal surface. The energy levels of the calculated resonant states of a helium-like system are compared with the energy of the observed structure. The agreement suggests that there are adsorbed 0− ions to which photoelectrons can be scattered at the metal-vacuum interface.
X-Ray Diffraction Applied to the Study of Defects in Surfaces
Authors: Robinson I. K. , D'amico K. L.
Published: March 2011

The role of x-ray diffraction in characterising defects in crystals is reviewed briefly. It is most sensitive to the presence of plane defects which destroy the long-range order. The same argument is shown to apply to line defects in surface structures. Two recent glancing incidence x-ray diffraction experiments provide contrasting examples: randomly distributed steps are found in the Au(110) reconstructed surface, while regular arrays of domain walls modify certain phases of krypton monolayers physisorbed on graphite substrates.
Characterization of Surface Defect Structure by Low Energy Electron Diffraction
Authors: Wendelken J. F. , Wang G. -C. , Pimbley J. M. , Lu T. -M.
Published: March 2011

Low energy electron diffraction is a surface sensitive tool which is most widely used for the determination of surface symmetries and equilibrium atomic positions. Experimental and theoretical advances made in the past five years make it possible now to use LEED also for the characterization of a wide variety of surface defect structures. In this paper a variety of experimental results involving analysis of diffracted electron beam shapes as a function of primary electron beam energy, adsorbate coverage, crystal tem-perature and ordering time are presented. These experimental results coupled with kinematic theory, allow the determination of step density, size and shape of reconstruction domains and overlayer islands, island size distribution in an overlayer during growth, and the mode of growth.
An HVEM Investigation of In-Situ, Self-Ion Damage in Iron at 40 and 300 K
Authors: Kirk M. A. , Robertson I. M. , King Wayne E. , Ryan E. A. , Philippides A.
Published: March 2011

Bombardments of iron (commercially pure) with self-ions having energies of 50 and 100 keV were performed in–situ in a High–Voltage Electron Microscope at temperatures of 40 and 300 K. The resulting damage microstructures were examined at the irradiation temperature in the HVEM using 200, 300, 500 and 1000 keV electrons (damage threshold in Fe is ˜330 keV). Dislocation loop densities were measured as functions of ion dose, ion energy, irradiation temperature, electron dose (500 keV), and step annealing to room temperature. Loop geometries, size distributions, and nature (interstitial or vacancy) were also determined.
Factors Affecting Spatial Resolution for Compositional Analysis in Stem
Authors: Sande John B. Vander , Garratt-Reed Anthony J.
Published: March 2011

This paper discusses the application of the scanning transmission electron microscope (STEM) to the detection of segregation at interfaces via the monitoring of X-rays generated when the incident electrons interact with the segregant. Issues of spatial resolution and minimum detectable concentration are discussed. Specific examples, emphasizing the importance of probe size, sample thickness, and sample orientation, are presented.
VUV Synchrotron Light as a Technique for Studying the Interface Quality and Properties of Thin Overlayers
Authors: Ruckman M. W. , Murgai V. , Strongin Myron
Published: March 2011

The measurements presented here show the value of synchrotron light for determining both the electronic structure of overlayers, and the physical nature of the overlayer-substrate interface. A comparison is given between deposited layers and thermally stabilized layers. Estimates are also made of the bonding energy between the overlayer and substrate.
Comparison of Performance of an Analytical Electron Microscope at 300 and 100 kV
Authors: Bentley J. , Kenik E. A. , Angelini P. , Fisher A. T. , Sklad P. S. , Lehman G. L. , Horton J. A.
Published: March 2011

Preliminary results on the performance of an analytical electron microscope (AEM) operating at 300 kV have been obtained and compared with the performance at 100 kV. Some features of the anticipated improvements for transmission electron microscopy (TEM) imaging, convergent beam electron diffraction (CBED), energy dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) have been studied from the aspect of materials science applications. The electron microscope used was a Philips EM430T operated with a LaB6 cathode and equipped with EDAX 9100/70 EDS and Gatan 607 EELS systems.
The Effect of Temperature on Defect Production in Copper Doped with Beryllium
Authors: Baily A. C. , King Wayne E. , Mrkle K. L. , Meshii M.
Published: March 2011

The effect of temperature on radiation-induced defect production was investigated in Cu single crystal films doped with ∼ 100 ppm Be. Frenkel pair production was determined at 55K and 190K as a function of electron energy and incident beam direction using in situ electrical resistivity measurements in the high voltage electron microscope. The crystallographic anisotropy of defect production was found to be considerably greater for irradiations at 55K than for irradiations below 10K. This difference is related largely to an observed anisotropy in the stage I defect recovery. It was found in isochronal annealing experiments after irradiation nearthreshold that the resistivity remaining after stage I was nearly twice as large for recoils along <110> as compared to <100>.
Characterization of Atomic Defects and Their Aggregates Using Positron Annihilation Spectroscopy
Authors: Siegel R. W. , Fluss M. J. , Smedskjaer L. C.
Published: March 2011

Positrons localize in trapped states at a variety of defect sites in solids, from which they subsequently annihilate with unique observable characteristics. As such, the positron is a valuable probe for the study of these defects. Positron annihilation spectroscopy (PAS) has made significant contributions in recent years to the determination of atomic defect properties in metals and alloys, and in molecular solids as well. It has also been used extensively in the monitoring and characterization of vacancy-like microstructure development, as occurs during post-irradiation annealing. The characterization of defects using PAS is selectively reviewed and some possibilities for using the positron as a localized probe of the atomic and electronic structure of atomic defects and their aggregates are discussed.
On the Properties of Ultra High Strength Concrete With Particular Reference to Heat of Hydration
Authors: Aarsleff Leif , Bredal-Jorgensen Jorn , Poulsen Ervin
Published: March 2011

It has been observed that the heat of hydration for concrete under practical conditions not only depends on the type of cement and the content of cement and silica fume in the concrete but also depends on the w/c-ratio of the concrete. On.microscopic examination of concrete having low w/c-ratio it has been observed that the cement compounds are left partly unhydrated. However, the unhydrated cement compounds exist for all values of the w/c-ratio, but appear to increase with decreasing value of the w/c-ratio, particularly when w/c < 0.35.

This fact wIll influence the present way of estimating the heat of hydration when a thermal stress analysis is to be carried out for an ultra high strength concrete in order to prevent the concrete from crackling due to temperature differences across a massive cross-section.

The tests are carried out with concrete having a compression strength greater than 100 MPa (∼ 14,000 psi). In order to obtain samples drilled from the same casting for compression tests, microscopic investigatlon, penetration tests and freezing/thawing-investigation rather large specimens are used. A very effective insulation of the concrete is provided, and the temperature of the concrete is recorded by thermo-couples.

The structure of the cement paste is studied using petrographical examination of thin-sections and polished samples. The tests on penetration and freezing/thawing are not dealt with in this paper.
Microstructure as A Tool for Proportioning High-Strength Concrete Mixes
Authors: Hester Weston T.
Published: March 2011

Until relatively recently, concrete mix materials were selected and proportioned on the basis of certain general principles established through empirical tests, past experience with similar materials, and published tables. Increasingly, however, wc. need to produce high-strength concretes with what has been considered sub-optimal or even marginal quality materials. And, whereas in the past we could afford to achieve high strengths at age 28 or 56 days, there is much greater emphasis now on achieving strengths in excess of 8,000 psi in 24 hours or less.

In response to these new demands for high-strength concretes, the concrete industry is setting aside many of the traditional methods for selecting and proportioning materials. Now, mix materials are selected deliberately for the characterisitics of their microstructure (e.g., the mineralogy and particularly crystal structure of the aggregates), and are proportioned to optimize the microstructure of the concrete.

In this paper the author illustrates how the characteristics of a material's microstructure are used as tools in selecting and proportioning mix materials. The significance of the microstructure of the aggregate particles, mortar-aggregate interface, and mortar are discussed in detail.
The Development of a High Strength Cementitious Tooling/Molding Material
Authors: Wise S. , Satkowski J. A. , Scheetz B. , Rizer J. M. , Mackenzie M. L. , Double D. D.
Published: March 2011

The composition and fabrication of a high strength cementbased composite containing graded stainless steel aggregate and fine silica are described. The microstructure, physical properties and temperature cycling durability of this material are examined and some examples are given of technological applications as a molding/tooling material.
Polymer Impregnation of an Impervious Cementitious Composite Material
Authors: Bright Randall P. , Wise Sean , Mackenzie Mark I.
Published: March 2011

Well compacted, silica fume-modified ordinary Portland cement pastes are well known for their low permeability. This quality can be maintained to temperatures slightly in excess of 200°C. Above this temperature, however, a continuous pore structure develops, making the material permeable and therefore unsuitable for high temperature applications (250–400°C) where vacuum integrity is necessary. To overcome this obstacle the permeability can be exploited for impregnating the concrete with an organic polymer. Organic polymers traditionally employed for impregnated concretes are not thermally stable enough to be used at high temperatures. Therefore, a high temperature-resistant organic resin has been studied for this application. The optimum conditions for impregnating this viscous resin into a high strength mortar have been investigated.
The Microstructure of High Strength Cement Pastes
Authors: Sinclair W. , Groves G. W.
Published: March 2011

The microstructures of high strength pastes of OPC and high alumina cements prepared by the high shear mixing of a low water/cement ratio paste with water soluble polymers have been studied by transmission electron microscopy. In the case of high strength OPC, the usual hydration products are present, however, the CSH gel lacks the fibrillar morphology often observed in conventional cements. Pastes based on high alumina cement do not contain the normal crystalline calcium aluminate hydrates but a small quantity of gel containing the organic polymer forms a continuous network structure bonding clinker grains. Microanalysis of the polymer phase in high alumina cement revealed the presence of Ca and Al while Ca-rich interstitial gel material was found in OPC pastes.
Relationships between Strength and Microstructure for Cement-Based Materials: an Overview
Authors: Mindess Sidney
Published: March 2011

The mechanical properties of cement-based materials must be controlled by the microstructure, pore geometry and chemical composition of the cement, by the properties of the aggregate, and by the nature of the cement-aggregate bond. While the precise form of the strength vs. microstructure relationship is as yet only imperfectly understood, enough is known to permit us to predict what alterations in the microstructure are required for the production of materials with very high strengths. There are also techniques available for reducing the brittleness that is often a characteristic of high-strength materials. The present paper presents an overview of the strength vs. microstructure relationships that can be used to predict the properties of high strength cement-based materials, and a brief review of some of the methods for achieving high strengths.
The Effect of Various Lead Species on the Leaching Behavior of Borosilicate Waste Glass
Authors: lehman Richard L. , Kuchinski Frank A.
Published: March 2011

A borosilicate nuclear waste glass was static leached in pure water, silicate water, and brine solution. Three different forms of lead were included in specified corrosion cells to assess the extent to which various lead species alter the leaching behavior of the glass. Weight loss data indicated that Pbm and Pb0 greatly reduce the weight loss of glass when leached in pure water, and similar effects were noted in silicate and brine. Si concentrations, which were substantial in the glass-alone leachate, were reduced to below detection limits in all pure water cells containing a lead form. Lead concentration levels in the leachate were controlled by lead form solubility and appeared to be a significant factor in influencing apparent leaching behavior. Surface analysis revealed surface crystals, which probably formed when soluble lead in the leachate reacted with dissolved or activated silica at the glass surface. The net effect was to reduce the release of some glass constituents to the leachate, although it was not clear whether the actual corrosion of the glass surface was reduced. Significantly different corrosion inhibiting effects were noted among lead metal and two forms of lead oxide.
Early Stages of Film Formation During the Leaching of Radioactive Waste Glasses
Authors: Houser C. A. , Pantano C. G.
Published: March 2011

The early stages of surface alteration-layer formation were examined during the leaching of some candidate radioactive waste glasses. The composition-depth profiles of the leached surfaces were obtained with sputter-induced photon spectroscopy (SIPS) and secondary-ion mass spectroscopy (SIMS). It was observed that the formation of multiple surface layers is a general feature of the glass dissolution process. The sequence of the layer compositions depends upon the order in which solubility limits are attained in solution, the adsorption or precipitation of insoluble hydrates at the glass/water interface, and subsequent incorporation of these insoluble hydrates behind the advancing reaction front. The boundary between the surface layer and bulk glass is sharp.
NNWSI Waste Form Performance Test Development
Authors: Bates John K. , Gerding Thomas J.
Published: March 2011

A test method has been developed to measure the release of radionuclides from the waste package under simulated NNWSI repository conditions, and to provide information concerning materials interactions that may occur in the repository. Data from 13 weeks of unsaturated testing are discussed and compared to that from a 13 week analog test. The data indicate that the waste form test is capable of producing consistent, reproducible results that will be useful in evaluating the role of the waste package in the long-term performance of the repository.
Parametric Testing of A DWPF Borosilicate Glass
Authors: Bazan F. , Rego J.
Published: March 2011

A series of tests have been performed to characterize the chemical stability of a DWPF borosilicate glass sample as part of the Waste Package Task of the NNWSI Project. This material was prepared at the Savannah River Laboratory for the purpose of testing the 165-frit matrix doped with a simulated non-radioactive waste. All tests were conducted at 90°C using deionized water and J-13 water (a tuffaceous formation groundwater). In the deionized water tests, both monoliths and crushed glass were tested at various ratios of surface area of the sample to volume of water in order to compare leach rates for different sample geometries or leaching times. Effects on the leach rates due to the presence of crushed tuff and stainless steel material were also investigated in the tests with J-13 water.
Mass Transfer in a Geologic Environment
Authors: Zavoshy S. J. , Chambre' P. L. , Pigford T. H.
Published: March 2011

A new analytical solution is presented that predicts the rate of dissolution of species from a waste package surrounded by a wet porous medium. By equating the rate of diffusive mass transfer into the porous rock to the rate of liquid-surface chemical reaction, an analytical solution for the timedependent dissolution rate and the time-dependent concentration of dissolved species at the waste surface is obtained. From these results it is shown that for most of the important species in a package of radioactive waste the surface liquid quickly reaches near-saturation concentrations and the dissolution rate can be predicted by the simpler theory that assumes saturation concentrations in the surface liquid.
Leaching Studies of Non-Metallic Materials for Nuclear Fuel Immobilization Containers
Authors: Onofrei M. , Raine D. K. , Brown L. , Stanchell F.
Published: March 2011

The leaching behaviour of various ceramics was studied as part of a program to evaluate their potential use as container material for very long term containment of nuclear fuel waste under conditions of deep geologic disposal.

Samples of four grades of Al2O3, stabilized ZrO2, TiO2, a cermet (70% A12O3- 30% TiC) and porcelain have been leached in deionized distilled water, Standard Canadian Shield Saline Solution (SCSSS), and SCSSS plus 20% Na-bentonite under static conditions at 100°C for periods up to 120 d.

The results of these ongoing leaching experiments suggest that the controlling features of the ceramic leaching process were leachant composition, and the presence and concentration of ions in the solution capable of preferentially precipitating on the ceramic surface, i.e., silicon, Mg2+, Ca2+, etc. Weight losses were determined after leaching. The initial leach rates showed a dependence upon ceramic purity and the processing used to prepare the ceramics, as well as the leachant composition. Also, it was apparent that the decrease of leach rates with time occurred as a result of the ceramic components in the leachant approaching their saturation limits.
Effects of Flow Parameters on the Leaching of Nuclear Waste Glass
Authors: Adiga R. B. , Akomer E. P. , Clark D. E.
Published: March 2011

Environmental conditions in a repository are expected to be significantly different from those encountered by a glass tested under MCC-1 specifications. In addition to variations in flow rate and glass surface area to water volume ratio (SA/V), the water chemistry and presence of waste package components in the repository will most certainly affect the leaching behavior of the glass. The independent effects of each of these variables have been studied by numerous investigators. For example, it is well known that the leaching rate increases as the flow rate increases (1). Also, the rate of approach to saturation is increased as SA/V is increased under MCC-1 type testing (2). The use of silicate water generally decreases the rate of leaching while waste package components such as iron enhances the leaching rate of glass under MCC-1 type testing (3–4).
Behavior of Natural Uranium, Thorium and Radium Isotopes in The Wolfcamp Brine Aquifers, Palo Duro Basin, Texas
Authors: Laul J. C. , Smith M. R. , Hubbard N.
Published: March 2011

Previously reported results for Palo Duro deep brines show that Ra is highly soluble and not retarded. Relative to Ra, U and Th are highly sorbed. Uranium, like thorium, is in the +4 valence state, indicating a reducing environment. Additional data reported here support these results. However, one Wolfcamp brine sample gives somewhat different results. Radium appears to be somewhat sorbed. Uranium is largely in the +6 valence state, indicating a less reducing condition. In all brines, kinetics for sorption (228Th) and desorption (224Ra) are rapid. This Wolfcamp brine was tested for the effects of colloids for Ra, U, and Th concentrations. No effects were found.