bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface States on a-Si:H,F Grown from SiF4 and H2
Authors: Maruyama A. , Liu J. Z. , Chu V. , Shen D. S. , Wagner S.
Published: March 2011

We describe a detailed study of surface states on a-Si:H, F films deposited by DC-plasma from SiF4 and H2. In the a-Si:H, F growth from these source gases, the density of surface states (Nss) and the Urbach Energy (Eu) show a reciprocal relation, meaning that the film grown with less bond distortion is accompanied by a higher density of surface states. These surface states can be reduced by keeping the films at growth temperature after termination of growth; immediate cooling produces a high density. This suggests that bonds can rearrange on or near the film surface at growth temperature, after growth termination. Nss can be made as high as l×1014 cm−2. The surface states can be measured by optical subgap absorption, but do not give an ESR signal. A high density of these surface states lowers the Pd-Schottky barrier height. Time-of flight electron collection data show that the surface states act as deep electron traps, located at about 0.4eV below the conduction band edge. We present and discuss other experimental results to help understand these nature of the surface state on a-Si:H, F.
Investigation of the Silicon Nitride on Hydrogenated Amorphous Silicon Interface
Authors: Gelatos A. V. , Kanicki J.
Published: March 2011

We report on our investigation of the silicon nitride on hydrogenated amorphous silicon interface by high frequency capacitance-voltage measurements. We show evidence for the existence of a large number of interface states at energies less than or equal to 0.36 eV below the hydrogenated amorphous silicon conduction band. In addition, we demonstrate that the states responsible for the hysteresis in capacitance-voltage characteristics are located in the silicon nitride layer. Finally, we argue that the ability of hydrogenated amorphous silicon to act as hole diffusion barrier is responsible for the observed flat-band voltage shift.
Growth of Surface Layer During the Leaching of The Simulated Waste Glass and its Barrier Effects on the Leaching
Authors: Ishiguro K. , Kawanishi N. , Sasaki N. , Nagaki H. , Yamamoto M.
Published: March 2011

The growth of surface layers on simulated waste glass during two different types of leaching has been studied in conjunction with their corrosion kinetics. Static and Soxhlet leach tests were performed in distilled water at a temperature of 100°C. Auger and ESCA analyses of solid samples after leaching showed that the layers consisted of two or three sublayers which were distinguished by their different components. The transition elements Fe and Ni, the rare-earths Nd and La, and Zn were concentrated in the layers, while Si, B and alkali were depleted in most of the layers. Growth kinetics of the layers followed approximately linear relations for the two types of leaching. Growth rates and elemental profiles of the layers depended upon the leaching conditions. Comparison between the leaching rate and the thickness of the layer showed that layers did not work as effective diffusion barriers until a threshold thickness was reached, which depended on the layer structures.
Leach Models for a Commercial Nuclear Waste Glass
Authors: Kuhn William L. , Peters Richard D.
Published: March 2011

A review of the leaching behavior of 76–68 glass shows that it cannot be explained in terms of diffusion in the glass, which has been the basis for several leach models. Instead, we present two models based on a dissolution rate impeded by surface processes: the accumulation of a protective layer of insoluble reaction products, and adsorption of reaction products on the surface. The resulting predicted time dependences are identical and predict a change from linear to parabolic rate laws for soluble species, which is found to agree with the data over a range of temperatures. Incongruent release is attributed primarily to solubility effects. The relative merits of the models are discussed on the basis of the effect of surface area-to-volume ratio in static leach tests. Their relevance to modeling repository behavior is discussed.
Releasing Behavior of Tritium from Neutron Irradiated Borosilicate Glass
Authors: Yamamoto Yoshimasa , Kitagawa Kazuo , Atsumi Hisao , Yamanaka Shinsuke , Miyake Masanobu
Published: March 2011

Specimens of borosilicate glass were irradiated in a material testing reactor at a neutron fluence of 1019–1020 nvt and a temperature of below 250°c. Tritium released from the specimen was determined by means of a specially designed sampling system and liquid scintillation counter.

Temperature and time dependence of the releasing behavior of tritium from borosilicate glass was obtained in the temperature range of 200 – 700°C. Very small amount of tritium as compared with the amount contained in the specimen was released in several hours at temperatures below 700°C. The greater part of tritium released from the specimen was tritium oxide, which is controlled by the diffusion step of tritium in the specimen. The diffusion coefficient of tritium in borosilicate glass was also obtained, which agreed with that of water in glasses.
Laboratory Investigations of Groundwater Interactions with Buried Radioactive Sodium Wastes and Attendant Release and Migration of Tritium in Adjacent Soil
Authors: Subbaraman G. , Steele III O. P. , Witbeck L. C. , Abrams C. S.
Published: March 2011

Shallow land burial of sodium-bearing low-level wastes requires an assessment of safetyconsequences relating to (1) groundwater interactions with the residual sodium in the event of a breach of containment and (2) release of tritium dissolved in sodium along with hydrogen (both of which will permeate through adjacent soil). This paper describes the tests and evaluations being performed to establish a data base on safety consequences of burying low-level radioactive sodium wastes (RSW). This data base can be used in establishing the amounts of sodium that may be tolerated in burying RSW and in establishing related criteria.
Correlation Between Dynamic Leach Test Results and Geochemical Observations
Authors: Barkatt Aaron , Macedo Pedro B. , Sousanpour William , Barkatt Alisa , Boroomand Morad A. , Szoke Peter , Rogers Victor L.
Published: March 2011

A test method based on partial leachant exchange at constant intervals until leachate concentrations become stabilized has been used to obtain a data-base in evaluating long-term leaching patterns. Applied to basalt and granite specimens and compared with ground-water analyses, correlations which can be used in long-term leachability extrapolations have been established. They are based on the following principles: (i) Control of solubilities of major components by combined aluminosilicate species; (ii) Continued increase in levels of soluble species, e.g. Na+ and Cl−, with time; (iii) Initial rapid leaching of SO42−, along with Ca2+ and K+, followed by slowing down, probably due to the presence of selectively leachable phases; (iv) Initial retardation of Mg and Fe leaching followed by regrowth as sorption sites become saturated.
Leaching Chemistry of Defense Borosilicate Glass
Authors: Wallace Richard M. , Wicks George G.
Published: March 2011

Studies of the leachability of waste glass have been in progress at Savannah River Laboratory (SRL) for several years. The principal objective of these studies has been to predict the long-term behavior of Savannah River Plant waste glass when stored in a repository. Such predictions can be made from the results of short-term tests only if the mechanisms of waste glass corrosion are understood. Determining the mechanisms of corrosion and developing a predictive model have therefore been a major thrust of our work.
Comparison of 200 Liter and 40 Milliliter Leach Tests
Authors: Westsik J. H. , Harvey C. O. , Roberts F. P. , Ross W. A. , Thornhill R. E.
Published: March 2011

During the past year we have conducted a modified MCC-1 leach test on a 145 kg block of a cast cement waste form. The leach vessel was a 200 liter Teflon®-lined drum and contained 97.5 liters of deionized water. The results of this large-scale leach test were compared with the results of standard MCC-1 tests (40 ml) on smaller samples of the same waste form. The ratio of leachate volumes between the large and small scale tests was 2500 and the ratio of sample masses was 150,000. The cast cement samples for both tests contained plutonium-doped incinerator ash.

The leachates from these tests were analyzed for both plutonium and the matrix elements. Evaluation of plutonium plateout in the large-scale test indicated that the majority of the plutonium leached from the samples deposits onto vessel walls and little (<3 × 10−12M) remains in solution. Comparison of elemental concentrations in the leachates indicates some differences up to 5X in the concentration in the large- and small-scale tests. The differences are attributed to differences in the solubilities of Ca, Si, and Fe at pH ˜11.5 and at pH ˜12.5. The higher pH observed for the large-scale test is a result of the larger quantities of sodium in the large block of cement.
Correlation of 137Cs Release From Small-Scale to Large-Scale Cement Waste Forms
Authors: Morcos Nabil , Dayal Ramesh , Milian Laurence , Hayde Philip , Weiss Allen J.
Published: March 2011

A study correlating the leachability of 137 Cs from small-scale to large-scale cement forms was performed. The waste forms consisted of (a) organic ion exchange resins incorporated in Portland I cement, with a waste-to-cement ratio of 0.6 and a water-to-cement ratio of 0.4 (as free water) and (b) boric acid waste (12% solution) incorporated in Portland III cement, with a waste-to-cement ratio of 0.7. 137Cs was added to both waste types prior to solidification. The sample dimensions varied from 1 in. ×1 in. to 22 in. × 22 in. (diameter × height). Leach data extending over a period of 260 days were obtained using a modified IAEA leach test. A method based on semi-infinite plane source diffusion model was applied to interpret the leach data, which allows prediction of the amount of 137Cs leached from the forms as a function of leaching time and waste form dimensions. A reasonably good agreement between the experimental and calculated data was obtained for both types of cement waste forms.
Microcracks and Radioactive Waste Disposal
Authors: Simmons Gene , Caruso Louis
Published: March 2011

Examination of microcracks in crystalline rocks has shown that the open microcracks form a spatially continuous network that communicates with larger openings. The open cracks become filled with new minerals that often contain U and LREEs. The crystalline rocks most desirable as a host for a repository have low crack porosity, moderate alteration, and occur in an environment that promotes rapid sealing.
Effect of Channelling in a Porous Medium on Radionuclide Migration
Authors: Ray Asit K. , Nair Shyam
Published: March 2011

A mathematical model has been developed to study the effect of channelling in a porous medium surrounding a repository on the migration of radionuclides. The porous medium is treated as an infinite medium containing parallel, unconnected channels; each channel is surrounded by a rock matrix. The migration in the channel is controlled by convection and diffusion processes in the direction of the flow, whereas in the rock matrix it is dominated by anisotropic diffusion in the longitudinal and transverse directions. Unsteady state convective-diffusion equations for this system have been solved. At the channel-rock matrix interface the concentration and flux were watched to obtain concentration profiles and discharge rates at downstream locations. By means of a parametric study the effects of channel thickness, diffusion coefficients, and flow velocity on the migration rate are elucidated.
Differential Scanning Calorimetry of Metamict Pu-Substituted Zirconolite
Authors: Peterson Dean E. , Clinard Frank W.
Published: March 2011

Samples of CaPuTi2O7 were prepared by cold pressing and sintering. Plutonium was substituted for zirconium in order to characterize radiation damage effects. The energy stored in a sample which had reached saturation in swelling after storage at ambient temperature was measured with a differential scanning calorimeter. The total energy of 6.6±0.1 cal/g is released over the range 485–715° C. The activation energy of annealing of the damage is 1.22±0.05 eV. The temperature dependence of the rate constant is described by kT= 5.96E4 exp(−1.22/kBT) s−1 where kB and T are the Boltzmann's constant and temperature(K) respectively. A sample stored at 600°C was similarly evaluated and showed no release of stored energy to the precision of the apparatus (±0.1 cal/g). These results are applied to analysis of waste incorporation in Synroc and are correlated with analogous parameters for other materials.
Glass Surface area to Solution Volume Ratio and its Implications to Accelerated Leach Testing
Authors: Pederson Larry R. , Buckwalter Charles Q. , Mcvay Gary L. , Lynn Riddle B.
Published: March 2011

Leaching tests of PNL 76–68 glass in deionized water have been performed using the standard MCC-l static leaching procedure but with varied glass surface area to solution volume ratios (SA/V). It was found that leaching could be strongly influenced by the SA/V ratio, due largely to an effect of silicon solubility limitations. The conclusion that solubility and not solid state diffusion is most important in regulating leaching rates is supported by (1) the similarities in depth profiles of all soluble glass components with none depleted to depths greater than that of silicon despite vastly different solid state diffusivities, and (2) the lack of dependence of leaching rates on reaction layer thicknesses. To more directly examine the influence of dissolved silicon on glass leaching rates, leaching tests were performed in silicic acid solutions and in two actual groundwaters. As expected, leaching rates of all soluble glass components were reduced by amounts roughly proportional to the silicon saturation fraction.
Since solubility modifies leaching rates in all but very dilute solutions, short-term tests at high SA/V values can be used to predict solution concentrations for long-term tests at low SA/V values, although reaction layers formed are not of the same thickness. Glass leaching data for a range of leaching times and SA/V values can be represented by a single curve when plotted versus the product of SA/V and time. However, the use of SA/V variations may have limited usefulness in accelerated leach testing for multicomponent systems. Events such as silica colloid and certain alteration phase formations modify the above relationship.
Approximations for Adapting Porous Media Radionuclide Transport Models to Analysis of Transport in Jointed, Porous Rock
Authors: Erickson K. L.
Published: March 2011

Initial criteria are defined which determine when radionuclide transport in jointed, porous rock can be approximated as occurring in an equivalent porous medium. For systems satisfying those criteria, the retardation factor to be used in the equivalent porous media model also is defined.
The Scepter Waste Package Subsystem Computer Model for Performance Assessment
Authors: Brecher Aviva , Pearson F. J.
Published: March 2011

The Waste Package Performance Assessment (WAPPA) code has recently been completed, verified, and documented within the SCEPTER program for ONWI. This is a systems model of the gradual degradation of physical and retardation barriers comprising a nuclear waste package, under repository isolation conditions, in various geologic media. The model describes and predicts the temporal and spatial extent of the loss of containment capability for each barrier and for the entire waste package, on timescales of hundreds of thousands of years. The output quantifies the residual state of integrity of waste package components as a function of time and calculates heat, and radionuclide fluxes to the repository.

The model includes five distinct degradation process models (Radiation, Thermal, Mechanical, Corrosion, and Leaching), which are driven both internally by waste decay and externally by repository stress and fluids. The process models are coupled at system level via state and coupling variables. The approach to degradation modeling adopted is barrier-integrated and process-sequential, allowing modification of the entire waste package sequentially by the five process models within each time step.

The code is intended to serve as a tool for evaluating both the relative and the absolute performance of waste package design concepts, for guiding or selecting a preliminary design among conceptual designs, and for support of licensing activities.
The Formulation of an Integrated Physicochemical-Hydrologic Model for Predicting Waste Nuclide Retardation in Geologic Media
Authors: Muller A. B. , Langmuir D. , Duda L. E.
Published: March 2011

The inability of empirical single value elemental Rd values to model radionuclide retardation in natural groundwater systems has demonstrated the need for developing a comprehensive integrated phenomenological model of the physicochemical and hydrologic mechanisms involved in retardation. The model must account for: (1) radioactive decay, (2) chemical precipitation/dissolution of bulk phases, (3) chemical substitution reactions, (4) isotopic exchange reactions, (5) cation and anion exchange, (6) specific adsorption, (7) diffusion into adjacent flow paths, (8) diffusion into fluid not involved in flow, (9) diffusion into the solid matrix and (10) ultrafiltration. The formulation of such a model is proposed, based on a reaction-path-simulation code with modifications for adsorption processes (by a surface-complexation site-binding model) and diffusional processes. The coupling of the physicochemical portion of this model to a ground-water transport code can be achieved by alternately iterating through the chemical and physical portions of the code during each time step. Sensitivity analysis used to determine dominant species, dominant retardation mechanisms and temporal and spatial homogeneities in the flow system will allow the integrated model to be reduced to a manageable form.
The Oak Ridge National Laboratory Hydrofracture Process for the Disposal of Radioactive Waste
Authors: Weeren Herman , Mcdaniel Earl
Published: March 2011

The hydrofracture process is currently being used at Oak Ridge National Laboratory (ORNL) for the permanent disposal of locally generated radioactive waste solutions. In this process, the waste solution is mixed with a blend of cement and other solid additives; the resulting grout is then injected into an impermeable shale formation at a depth of 200 to 300 m (700 to 1000 ft). The grout sets a few hours after completion of the injection, fixing the radioactive waste in the shale formation.

Between 1966 and 1979, ORNL has used hydrofracture to dispose of more than 8 million L (2 million gal) of waste grout containing more than 600,000 Ci of radionuclide activity. Calculations show that operational costs are on the order of $0.16/L ($0.60/gal). Construction of a new hydrofracture disposal facility has been completed, and operational injections were initiated in June 1982.
Use of Poisoned Land/Inland Seas for Low Level Radioactive Waste Disposal
Authors: Brookins Douglas G. , Vogler Herbert A. , Cohen J. J.
Published: March 2011

It is widely known that certain areas of the earth are characterized by such high concentrations of toxic elements that their use by plants or animals is precluded. A water hole whose water contains potentially toxic quantities of As is a common example of such a naturally poisoned area. The dry salt basins of the Basin and Range Province in Nevada and western Utah are largely relict inland salt seas and, because many of the salt basins have total interior drainage of both surface and ground water, these basins represent unique geochemical environments for the entrapment and concentration of mobile elements. Through leaching, transport, and ultimate deposition from throughout the water shed, the closed salt basins are hydrologic sinks in which toxic materials such as As, Sb, Hg, and other heavy metals become concentrated in a relatively confined area.
RA-226 Radioassay of Soil and Tailings
Authors: Sabau Cabmen S. , Rayno Donald R. , Kretz Norbert D. , Zelle Phillip W.
Published: March 2011

Studies of inactive uranium tailings piles have shown that tailings sands containing Ra-226 and other radionuclides may be dispersed by wind and water erosion, causing contamination of adjacent areas. To conduct an effective cleanup operation, it is necessary that boundaries of contamination be well defined. To accomplish this, data from surface gamma-ray surveys made under the Measurement Monitoring Program of the U.S. DOE's Uranium Mill Tailings Remedial Action Project (UMTRAP) are first used to delineate a general outline of the contaminated area. Then, data fram portable scintillometer surveys and fran sealed-can gammaray analyses of soil samples are used to more precisely define the perimeter of Ra-226 contamination. These field measurements are supported by radiochemical analyses of randomly selected samples. Because of its adaptability to the widely varying chemical composition of the material in these samples, the camplexing agent EDTA is used in a complexometric leaching procedure to analyze Ra-226. By this procedure, natural concentrations of Ra-226 in soil (∼1 pCi/g) can be measured routinely. The potential limit of detection is in the 0.1–0.5 pCi/g range. Details of the method, which includes leaching of radium followed by radon de-eranation, are described. Comparative data for various soil and tailings samples are presented.
Analyses of Soils from the Commercial Radioactive Waste Disposal Sites at Barnwell, Sc, and Hanford, Wa
Authors: Piciulo Paul L. , Shea Colleen E. , Barletta Robert E.
Published: March 2011

Brookhaven National Laboratory, in order to provide technical assistance to the NRC, has measured a number of physical and chemical characteristics of soils from two commercial radioactive waste disposal sites: one at Barnwell, SC, and the other near Richland, WA. Materials commonly used for the containment and the solidification of radioactive waste are subject to underground corrosion. The data reported can be used to assess the corrosivity of each burial environment on a waste form or high integrity container. Samples of trench backfill soil, believed to be representative of the soil that will contact the buried waste forms were collected and analyzed. Earth resistivities were measured at each site. Laboratory measurement of the resistivities of water saturated backfill soils from both sites show values greater than 104ohm-cm. This is indicative of soils having relatively small amounts of soluble ions and of soils likely to be very mildly corrosive to steel. The backfill soil from the Barnwell site is acidic having a pH ∼5. Measurements on Hanford backfill soil indicate a neutral environment; pH ∼7. The exchange acidity of the backfill soils from both sites was <2 meq per 100 g of soil and in most cases an alkaline reaction was observed. The pHs and exchange acidities of these soils are consistent with those of mildly corrosive soils. Aqueous extracts of saturated pastes were used to determine the concentrations of the following ions: Ca2+, Mg2+, K+, Na+, HCO3−, SO4=, and Cl−. The sulfide content of each of the soils was measured in a mixture of soil and an antioxidant buffer solution.
Some Effects of Microstructure and Chemistry on Corrosion and Hydrogen Embrittlement of Ticode–12
Authors: Ruppen J. A. , Diegle R. B. , Glass R. S. , Headley T. J.
Published: March 2011

Effects of microstructure and chemistry on corrosion and hydrogen embrittlement of TiCode-12 have been investigated. Heat treating mill-annealed TiCode-12 in the temperature range 500–750°C results in a sensitization effect, i.e., an increase in the uniform corrosion rate when tested in either boiling 1N HCl or a MgCl2brine. This effect is caused by microstructural changes involving the precipitation of Ti2Ni. Electrochemical studies indicate that sensitization results from galvanic coupling between Ti2Ni, acting as cathode, and the α-Ti matrix with resultant shifts in corrosion potential. Increasing the Fe content of the alloy promotes the sensitization effect.

Hydrogen embrittlement of TiCode-12 was studied using the slow strain rate technique. Hydrogen concentrations to 130 wppm did not cause embrittlement. However, above 220 wppm hydrogen, degradation was observed as a decrease in mechanical behavior and the appearance of cleavage-like secondary cracks. The embrittlement was dependent on temperature and alloy chemistry but not environment (air or brine).
Laboratory Studies of Fluid Flow Through Borehole Seals
Authors: South David L. , Daemen Jaak J. K.
Published: March 2011

Three experiments performed on cement borehole seals in granite indicate flow through the seal is slightly lower than flow through the intact rock. The experiments were performed at stress states simulating depths of approximately 350, 700, and 1000 meters.
Fixation of high Level Solid Waste (HLSW) in a TiO2 Base Ceramic Matrix Provided with an Integrated Overpack
Authors: Bauer Christof , Ondracek Gerhard
Published: March 2011

In the past years a lot of research work has been done in several countries to find a waste form capable of accommodating the wide variety of elements present in commercial high level waste (HLW) and which at the same time, has a higher leaching resistance than the currently favoured high level waste glass. The main problems arising from a product made up of different phases, each of them taking up a certain fraction of the HLW-elements into solid solution, are

1) the necessity of very intimate mixing of the HLW-elements and the inert additives because otherwise undesired highly leachable phases might be formed;

2) the detrimental effect transmutation of the radioactive elements will most probably have on the crystal structure in which they are present. Fracturing and loss of the low solubility of the products are likely to occur.
Experimental Investigation of Sodium Bentonite Stability in Hanford Basalt
Authors: Wood M. I.
Published: March 2011

Sodium bentonite is a candidate material for the waste package backfill component in a repository in basalt at the Hanford Site. Preliminary hydrothernmal experiments have been conducted under near-field geochemical conditions expected to occur in the reference repository location in the Grande Ronde Basalt. Experiments have been conducted in the basalt/groundwater, bentonite/groundwater, and basalt/bentonite/groundwater systems. The experiments have been conducted at 300°C using a simulated Grande Ronde groundwater, reference Umtanum basalt, and sodium bentonite. Key data generated by the experiments include experimental solution analyses as a function of time and preliminary solids analysis by scanning transmission electron microscopy and X-ray diffraction. Solution trends of the major aqueous species were similar in the three systems and are characterized by: (1) the gradual reduction of the pH value from ∼9.75 to a steady-state value of ∼6, (2) an initial rapid increase followed by a gradual decrease in silica concentration, and (3) a slight or negligible increase in sodium, sulfate, and chloride concentrations. In the bentonite/groundwater experiment, small amounts (<1%) of an albite reaction product were observed. Conversely, the formation of illite, a common bentonite alteration product, was not observed. These results indicate that sodium bentonite will remain sufficiently stable at 300°C under hydrothermal conditions in basalt to permit its use as a backfill material.
Ion Beam Processing of Optical Thin Films
Authors: Gibson U. J.
Published: March 2011

The microstructure and optical properties of vacuum evaporated coatings are a sensitive function of the deposition conditions. In recent years, ion bombardment has been used increasingly for the production of denser, more stable coatings of oxides and other materials. In addition to modifying the microstructure, ion bombardment is emerging as a valuable tool for altering the composition (and hence the optical properties) of thin films. A discussion of the effects of ion beam processing and the methods used to analyze the changes in these films is presented.
Correlation Between Optical Absorption and Refractive Index of Silica and Silicate Glasses Implanted with Copper
Authors: Weeks R. A. , Hosono H. , Zuhr R. , Magruder R. , Mogul H.
Published: March 2011

The refractive indices and optical absorptions of Cu implanted glasses have been measured. Silica and two silicate glasses have been implanted with Cu+ to nominal doses ranging from 3×1015 cm−2 to 6×1016 cm−2 at an energy of 160KeV and currents of ∼4μAcm−2. Substrate temperatures, during implantation, ranged from ∼100K to 700K. Both refractive index and optical absorption of the silica are functions of dose and substrate temperature. Neither of these properties are significantly altered in the silicate glasses for any dose or substrate temperature. The observed increases in the index of the implanted silica are attributed to an optical band due to Cu0 colloids.
Ion Irradiation Damage In MgAl2O4 and Al23O27N5 Ceramics
Authors: Knight P. A. , Jenkins M. L. , Pells G. P.
Published: March 2011

Polycrystalline magnesium aluminate spinel (MgAl2O4) and Al23O27 N5 (ALON) were irradiated with 4 MeV Ar+ ions to doses from 0.5 to 6 displacements per atom (dpa) at a temperature of 1070K and subsequently examined using transmission electron microscopy. Faulted dislocation loops were found in both materials, although their habit planes ({110} and {111} respectively) and Burgers vectors (a/4 <110> and a/6 <111>) differ. Cavities were found in spinel but not in ALON. Both materials exhibited a similar, low, degree of radiation damage and we conclude that polycrystalline ALON is a good potential reactor window material.
Ion-assisted Laser Deposition of CaF2thin Films onto Ccold Substrates
Authors: Gluck N. S. , Sankur H. , Gunning W. J.
Published: March 2011

Thin CaF2films were grown at low temperatures (20°C) using an ion-beamassisted laser evaporation method. Smooth, dense, environmentally stable coatings with bulk refractive indices were produced. This technique was applied to deposit mid-wave IR dichroic filters using CaF2and Ge layers onto cold substrates.
Photoinduced Nonlinear Effects in Optical Glass Fibers
Authors: Österberg U.
Published: March 2011

Photoinduced periodic structures in silica glass fibers doped with germanium and phosphorous will be discussed.
Effect of Stress on field Confinement in Channel Waveguides formed by Defining Si3N4 Ridges on GaALAS Multilayer Structures
Authors: Radens Carl J. , Roughani Bahram , Jackson Howard E. , Boyd Joseph T. , Burnham Robert D.
Published: March 2011

Optical channel waveguiding has been observed in a structure consisting of a silicon nitride ridge on a multilayer GaAlAs heterostructure. The silicon nitride layer was deposited and then patterned to form 3.5 micron wide ridges. The optical field intensity radiating from the endface of the channel waveguide is found to have two peaks symmetric about the center of the silicon nitride ridge. Raman microprobe spectroscopy indicates a significant stress-induced shift in the GaAs longitudinal phonon frequency. Rapid thermal annealing reduces the stress and changes the optical field intensity distribution to a single symmetric peak.
The Effect of Hydrogen on the Charge States of Oxygen Vacancies in Thermochemically Reduced Alkaline-Earth Oxides
Authors: Chen Y. , Orera V. M. , Gonzalezv R. , Williams R. T. , Williams G. P. , Rosenblatt G. H.
Published: March 2011

To a greater or lesser extent, all alkaline-earth oxide crystals contain hydrogen. Thermochemical reduction (TCR) of MgO and CaO crystals at high temperatures (˜2000K) and high pressures (4 to 7 atmospheres) of the metallic cation vapor (Mg and Ca respectively) results in a stoichiometric deficiency of oxygen ions, creating F centers (oxygen vacancies each with two electrons) and H− ions (protons in the anion sublattice, each occupied by two electrons). The positively-charged H− ions serve as traps for electrons excited from the F centers. Steady-state photo-excitation of the F absorption band results in F luminescence which typically extends to several minutes. This photoluminescence is detrimental for certain applications, such as tunable lasers. We have been able to reduce the hydrogen concentration prior to TCR of MgO and during TCR of CaO. The result is that the oxygen vacancies are predominantly in the one-electron F+ charge state. In contrast to the F luminescence, the decay of the F+ luminescence does not exhibit long phosphorescence. The prevalence of the F+ over the F state is found to be a function not only of the hydrogen concentration but also the severity of the thermochemical reduction.
Calculation of Ion Channeling Directions in Low Symmetry Optical Materials
Authors: Poker D. B.
Published: March 2011

Rutherford backscattering spectroscopy along ion channeling directions is useful for numerous applications in the characterization of all types of materials, due to its sensitivity to interstitial location, lattice quality, and composition. The determination of channeling directions and sample orientation in materials with high symmetry lattices is usually straightforward. However, many optical materials have relatively low crystal symmetry, which complicates the determination of likely directions for ion channeling. This is especially true of electrooptic materials, such as LiNbO3, which lack inversion symmetry. Therefore, an algorithm for the calculation of likely channeling directions in low symmetry lattices has been developed.
New Non-Oxide Glasses for Optical Waveguiding
Authors: Lucas Jacques
Published: March 2011

The first generation of infrared optical waveguides operating in the mid I.R. region 0.3 to 4 μm is made from fluoride glasses based on zirconium tetrafluoride. A new family of vitreous materials based on indium fluoride appears to be also promising candidate. The state of art in the field including performances and limitations of these optical fibers will be described. A new class of heavy halide glasses based on tellurium chloride, bromide or iodide is presented in relation with their large optical transmission range covering the 8–12 μm region. First attempts in fiber preparation and planar waveguides deposition will be discussed and compared with the traditional chalcogenide glasses.
The Growth of Organic Single Crystals in Glass Capillaries for Second Harmonic Generation
Authors: Holdcroft Geoffrey E. , Dunn P. L. , Rush J. D.
Published: March 2011

The growth and characterisation of a number of organic single crystals, e.g. benzil, 2–methyl–4– nitroaniline and 2–N,N–dimethylamino–5–nitroacetanilide, in silica capillary has become fairly well established over recent years. [1–6 ] However the growth of these same compounds in glass capillary with a much higher refractive index than silica has received little interest. Crystal cored fibres, ccf's, in which there is a close match of the refractive index of the cladding to that of the core allows the possibility of fabricating single mode waveguides with useful dimensions for crystal growth. There is a better overlap integral between phase matched fundamental and second harmonic modes in a low moded structure than in a structure with more allowable modes and thus a rise in the conversion efficiency can be expected if the correct dimensions of waveguide are chosen. If a ccf of high conversion efficiency, 10% at 0.1 mW average power, could be made then the promise of fabricating an organic optical nonlinear device, e.g. parametric amplifier, might be realised. In this paper we will describe how the growth method adopted for silica clad organic crystals has been adapted for their growth in a range of Schott glasses which are better matched in refractive index, RI, than silica to the organic material. The linear and nonlinear optical properties of these crystal cored fibres will be given in terms of; the orientation of the crystal axes with respect to the fibre direction; the sideways scattering characteristics from defects; the throughput of the fundamental beam; the polarisation states of both the fundamental and the second harmonic outputs; and the overall efficiency of second harmonic generation.
On the Structure of Carbon Films Deposited on Si(111) by Mass-Selected Low Energy C+ Beams
Authors: Robertson J. L. , Jiang X. G. , Chow P. C. , Moss S. C. , Lifshitz Y. , Kasi S. R. , Rabalais J. W. , Adar F.
Published: March 2011

Our recent report of epitaxial single crystal growth of C+ ion-beam-deposited diamond films on (111) single crystals of silicon is shown to be incorrect. We briefly describe the circumstances leading to this revision (and to our earlier finding) and discuss the possible structure of these films based on preliminary synchrotron X-ray data and on the Raman spectrum.
Defects in KTiOPO4
Authors: Morris P. A. , Crawford M. K. , Ferretti A. , French R. H. , Roelofs M. G. , Bierlein J. D. , Brown J. B. , Loiacono G. M. , Gashurov G.
Published: March 2011

KTiOPO4(KTP) is a nonlinear optical crystal presently used for second harmonic generation and electro-optic applications. The properties (ionic conductivity and damage susceptibility) of KTP crystals can vary depending on the specific technique and conditions used for growth. Consistent defect mechanisms have been determined to explain the observed AC conductivity and damage results of KTP grown by the flux and high and low temperature hydrothermal techniques. The presence of nonstoichiometry on the K and O sublattices in KTP, increasing in magnitude with temperature, is proposed. Using these defect mechanisms, the predominant defects compensating for the formation of vacant potassium sites (VK's) in flux and hydrothermal materials are vacant oxygen sites (VO's) and OH−'s, respectively. The presence of a more varied distribution of OH−sites at room temperature in high temperature hydrothermal material with higher AC conductivity indicates the importance of specific OH−sites in the lattice that may enhance the mobility of ionic carriers. The correlation of higher AC conductivity to increased average current and damage in electric field treated KTP is explained on the basis of the proposed compensating defects (VO's and OH−'s) which set the [VK] and [Ti3+]. The similarity of the linear optical properties of KTP grown by the various techniques is confirmed by the insensitivity of the absorption edge to the nonstoichiometry or defects present.
Laser-Induced Formation of Thin Silicone Layers with High Purity
Authors: Roth W. , Henkel H.-J. , Hoffmann K.W. , Markert H.
Published: March 2011

Unsaturated and saturated oligomeric siloxanes were polymerized by laser irradiation in the UV range without the use of photoinitiators. The obtained silicon layers possess high purity and non-corrosive effects.
Spin-On Dielectrics: Good News and Bad News!
Authors: Smolinsky G. , Lifshitz N. , Ryan V.
Published: March 2011

Five classes of spin-on dielectrics are discussed: polysilicates, polysiloxanes, polysilsesquioxanes, polyhydrocarbons, and polyimides. The emphasis is on the first three materials because very few polyhydrocarbon spin-on materials are available for study while spin-on polyimides sorb significant amounts of water. The polymer chemistry of the silicates, siloxanes, and silsesquioxanes is linkage through Si-O-Si-O bonds. Polyhydrocarbons are primarily linked through C-C bonds. As the name implies, polyimides are linked through (usually aromatic) imide groups. Because of their polar nature, polyimides, polysilicates, and polysiloxanes have dielectric constants >3, while the large hydrocarbon content of the remaining materials results in a dielectric constant of <3. Films of polysilicates are relatively brittle and thus are limited to a thickness <1 μm. On the other hand, films of polysilsesquioxanes, polyimides, and polyhydrocarbons can be readily deposited to a thickness >1 μm. Polysilicates have high temperature (>900°C) stability and do not react with O2; most polyhydrocarbons decompose above ˜350°C and oxidize readily; some polyimides are stable to 500°C; polysiloxanes and polysilsesquioxanes readily survive 425°C in N2. (Films of the latter two materials are converted to silicates upon heating at high temperatures in O2 or steam.) The infrared spectrum of a 425°C-cured silicate film shows the presense of Si-OH bonds and water, but after a 900°C anneal, the spectrum is almost identical to that of thermal oxide. The spectra of films of polysiloxanes or polysilsesquioxanes do not exhibit Si-OH absorption. Water retention in films is deleterious to the electrical and mechanical (swelling) properties of the dielectric and to making good aluminum-to-aluminum electrical contact through submicron vias. The water leads to a mobile charge (H+) phenomenon that is readily detected by a Triangular Voltage Sweep technique. Except for polysilicates, solutions of the other spin-on materials have reasonably long (weeks-to-months) shelf-lives. Polysilicate solutions are sols and tend to gel; the time to gelling is a function of solids content and solvent. Even though they exhibit shortcomings, polysiloxanes appear to be best suited as interlevel dielectrics in multilevel metalization schemes.
Development of New Ion Beam Modification Techniques to Enhance Copper and Polyimide (PI) Adhesion in Multilevel Electronic Packaging.
Authors: Paik Kyung W. , Ruoff Arthur L.
Published: March 2011

Two kinds of ion beam etching techniques, Ar gas ion beam etching (IBE) and oxygen gas reactive ion beam etching (RIBE), were used for adhesion enhancement of the PI/Cu and Cu/PI interface, respectively.

Ar gas IBE on Cu followed by deposition of PI film on the modified Cu surface can double the adhesion strength of spin-coated PI on Cu compared with unmodified Cu. The adhesion enhancement is due to increasing the surface contact area of the rough Cu surface to PI. However, a corrosion reaction happens at the polyamic acid (PAA) and Cu interface, resulting in the dissolution of Cu into the PI film and Cu oxide layer growth during curing of PI film. A Cr layer between Cu and spin-coated polyamic acid(PAA) is necessary to keep the Cu from dissolving in PAA and diffusing into PI. Ar IBE modification on Cu followed by deposition of a thin Cr layer on the modified Cu surface is recommended to enhance the adhesion strength of spin-coated PI on Cr.

O2 RIBE on PI followed by evaporation of Cu on a modified PI increases the peel strength of Cu/PI by more than 25 times. The maximum peel strength of Cu on the PI modified by O2 RIBE is almost 70 grams/mm. The increase of adhesion is due to the mechanical interlocking of a unique structure of modified PI - a grass-like structure. This structure occurs because of the inhomogeniety of PI film - the presence of ordered and disordered phases in a PI film. In addition, the Cu/PI interface exhibits stability with thermal cycling and humidity, because the adhesion enhancement is mostly due to a mechanical effect and not a chemical effect. The diffusion of Cu into PI at various temperatures is not significant. Typically, Cu atoms can diffuse up to 300 at 400 °C in 1 hour. Another advantage of O2 RIBE on PI is the capability of enhancing the adhesion of the second PI layer on a first PI layer.

These technologies allow the precise control of the adhesion strength of the PI/Cr/Cu and Cu/PI interfaces by independent variation of the beam energies, ion doses and angle of beam incidence. Also the ion source is easily installed in the same vacuum chamber for Cr and Cu evaporation. This provides low cost and simple operation.
In SituFTIR Investigations Of Polymer Surface Modification In Downstream Microwave Plasma Etching
Authors: Leu Jihperng , Jensen K.F.
Published: March 2011

In situFourier transform infrared (FTIR) reflection-absorption spectroscopy investigations of etching of thin polyimide and poly(methyl methacrylate) films (200–1500Å) in downstream microwave NF3/O2/Ar plasmas are reported. Etch rates and surface chemistry are monitored as a function of gas phase composition, plasma treatment conditions and time. NF3/Ar plasma treatment leads to significant surface fluorination characterized by the formation of aliphatic fluorine compounds (CFx), acyl fluorides, benzoyl fluoride, and polyfluorinated benzene. Addition of oxygen to the etching gas reduces the degree of surface fluorination and modifies the chemical structure. The absorption bands due to CFxstructures decrease gradually while polyfluorinated benzene rings and benzoyl fluoride are absent for NF3/O2mixtures with more than 20% oxygen. The effect of humidity on the plasma-modified polymers is studied by comparing infrared spectra collectedin situwith those after air exposure. For NF3/O2plasma-treated polyimides significant changes are observed while samples fluorinated in NF3show no changes after exposure to air overnight. The FTIR data are supplemented by XPS analysis.
Morphology of Lignin-Polyurethane Blends
Authors: FeldMan D. , Lacasse N. A.
Published: March 2011

The morphology of blended polyurethane (PU) sealants was studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The PU was modifided by mechanical mixing with various amounts of Lignin (L) to achieve a homogeneous blend. Specimens were subjected to control (C), accelerated weathering (AW), and natural weathering (NW) conditions. Results obtained from SEM analysis reveal an even distribution of L particles in the PU matrix. Furthermore, the SEM photomicrographs clearly emphasize the differing morphologies of the constituent phases. They also depict the differences in surface texture between control and aged specimens. The DSC analysis shows that the two phases are immiscible which is in agreement with observations by microscopy.
Film Stress in High Density Thin Film Interconnect
Authors: Pan J. Tony , Poon Steve
Published: March 2011

High density thin film interconnects are expected to be widely used for multi-chip module application to accommodate next generation high I/O and high speed integrated circuits. These interconnects typically use polyimide as the dielectric, and aluminum or copper (with protective overcoat) as the conductor. The interconnects are typically built on silicon or alumina substrates. Large film stress occurs due to the high processing temperature required to cure polyimide and due to the mismatch in thermal coefficients of expansion (TCE) between the film materials and substrate materials. This work studies film stress for these materials.

An instrument which measures thin film stress in-situ at temperatures between 25 and 450°C was used to characterize the stress in polyimide, nickel, and copper films. Two substrate materials, silicon and sapphire, were used in order to extract the TCE and elastic modulus for each film material. Three polyimide materials were evaluated. One of the polyimides studied showed complete stress relaxation at temperatures above 300°C and was almost completely elastic upon heating and cooling between 25 and 300°C. The TCE was calculated to be 41×10−6/°C and the biaxial elastic modulus was 4.0×109 Pascal. The nickel had very low stress asplated, however, high tensile stress was observed after 350°C annealing as a result of TCE mismatch. After first annealing, the nickel was almost completely elastic upon cooling and repeated heating and cooling between 25 and 350°C. Copper, on the other hand, was not completely elastic under similar thermal treatments. High thermal stress caused plastic deformation to occur in copper films. The room temperature stress in copper film after 350°C annealing depended on yield strength instead of TCE mismatch. The stress in these materials and its effects on processing and reliability for high density interconnect will be reported.