bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation Between Microstructure and Optoelectronic Properties of a-SiGe:H
Authors: Weller H. C. , Bauer G. H.
Published: March 2011

A dense network structure with low defect and void densities in a-SiGe:H alloys are realized by remote deposition conditions (triode reactor configuration, H2-dilution of SiH4+GeH4 gas mixture). The material properties are characterized by optical transmission, photothermal deflection spectroscopy (PDS), scanning electron microscopy (SEM), and space charge limited currents (SCLC). A high refractive index n∞. (λ->∞) and a fine surface structure in SEM images indicate an optical dense network, moreover the defect density determined by SCLC is reduced in comparison to films deposited in a conventional diode reactor. The substrate temperature TS, one of the key parameters for high quality low gap material, sensitively influences the optical and electronic properties of the samples. The optimum substrate temperature (TS≍=225°C) is found to be lower than for the deposition of a-Si:H (TS≍250°C).
Potential Profiles in Amorphous Alloys Devices
Authors: Vanderhaghen R. , Longeaud C.
Published: March 2011

The standard time of flight technique is modified to analyse the internal field profiles in hydrogenated amorphous silicon or amorphous alloys devices. The spatial resolution of the field can be better than a thousand angstroms.

With this method the internal field profile in a Schottky structure, built in the sandwich geometry Pt/a-SiGe:H/Cr, was studied. The field profile is found to decrease exponentially with the distance to the Pt/a-SiGe. We also underline the non-ohmic behaviour of the a-SiGe/Cr interface. The shape of the internal field along the intrinsic zone in P-I-N devices is also studied by the same method.

The variations of the field profiles in both devices (Schottky and P-IN) with various applied DC biases is presented.
On the Properties of Weakly Absorbing Highly Conductive SiC Thin Films Prepared in a TCDDC System
Authors: Martins R. , Willeke G.
Published: March 2011

p- and n-type weakly absorbing highly conductive (σ>0.1(Ωcm)-1) SiC thin films with similar structural and optoelectronic properties have been prepared in a TCDDC reactor. These films contain Si microcrystals embedded in an amorphous Si:O:C:H matrix. C is preferentially incorporated as stoichiometric SiC, whereas O is present mainly as suboxide. Absorption coefficients smaller than cr-Si are observed for films containing about 20at% C and 25at% O. From diffraction studies there is no evidence for the presence of SiC crystallites. Photoluminescence studies show a peak at about 1.68eV, similar to gd a-SiC:H of comparable optical properties.
A Semi-Transparent Solar Cell Using a-SiC
Authors: Hanaki Ken-Ichi , Hattori Yutaka , Nakabayashi Hideki , Yamaguchi Shunzo , Hamakawa Yoshihiro
Published: March 2011

A review is given of the fabrication technology and applications of a new type of semi-transparent solar cell having the structure p(a-SiC)-i(a- SiC)-n(μ-Si) heterojunction. A series of systematic investigations has been made on the effect of i-layer thickness and the optical energy gap on the photovoltaic performance of p(a-SiC)-i(a-SiC)-n(μ-Si) heterojunction solar cells. The results show that there is an optimum zone in the i-layer properties. For purposes of making cells with sufficient visible light transmission, we adopted an a-SiC active layer whose optical energy gap is in the range from 1.9 to 2.0 eV. In this case, a conversion efficiency of 6.3% with visible light transmittance of more than 25% has been obtained. The rate of light induced degradation has also been checked on this new type of solar cell. This newly developed semi-transparent solar cell, named “SOLAR GLASS,” might open new areas in a wide variety of applications for modern life such as home electronics, automobiles, medical electronics, etc. As an example, an automobile application is demonstrated and discussed.
Advances In High-Efficiency, Multiple-Gap, Multijunction Amorphous Silicon-Based Alloy Thin-Film Solar Cells
Authors: Guha S.
Published: March 2011

It is now well-recognized that multijunction, multi-gap amorphous silicon-based alloy solar cells offer the attractive advantage of obtaining high efficiency with good long-term stability. In this paper we review the progress made in this field. Research directions to further improve the efficiency are discussed.
Direct Measurement of the Mobiuty-Lifetime Product of Holes and Electrons in an Amorphous Silicon P-I-N Cell
Authors: Crandall Richard. S. , Sadlon Kyle , Kalina Jeffrey , Delahoy Alan E.
Published: March 2011

Direct measurements of the electron and hole mobility-lifetime products, μτ, on a 10μm thick hydrogenated amorphous silicon (a-Si:H) pi- n solar cell are presented. The μτ products, determined from charge collection using strongly absorbed light are μτ|h = 2.2 × 10−8cm2V−1 and μτ|e = 3.0 × 10−7cm2V−1, for holes,and electrons, respectively. Measurements of the drift length, ld = μτ|e + μτ|h, using uniformly absorbed light and analyzed using the uniform field model,1 give ld = 2.9 × 10−7 cm2 V−1 s−1. These results are the first experimental evidence that the carrier with the larger, μτ product determines the photovoltaic behavior. Evidence for space charge limited transport of photogenerated holes is also be presented.
Linkage of Efficiency and Stability of a-Si Solar cells
Authors: Redfield David , Bube Richard H.
Published: March 2011

By combining the steady-state and transient behaviors of a recently generalized analysis of the kinetics of metastable defects in good amorphous Si:H, it is shown that no treatment can remove all metastable defects. There is always a significant remnant that is proposed to be the observed built-in defects, which are then not a separate species, distinct from the metastable defects. This remnant is due to vibrational breaking of weak bonds in latent defect centers, and cannot be due to recombination of thermally excited carriers. If the stability can be improved by reducing the number of these latent defect centers, this will also reduce the density of built-in defects that control the initial efficiency. Furthermore, there are good reasons to believe that the source of these defects is extrinsic to a-Si:H, so that improvement in both properties may be achievable.
Growth Kinetics for Propagation of Si-Network
Authors: Azuma M , Shirai H , Hanna J. , Shimizu I
Published: March 2011

Chemical reactions were systematically investigated with regard to the propagation of Si-network in the vicinity of the growing surface by using various precursors, SiHn, SiHnFm, and SiHnCim (n+m≤3) generated by plasma-induced decomposition of SiH4, SiF4, SiH2Cl2 and SiHCl3. Atomic hydrogen was an effective agent to promote the propagation reaction due to its strong chemical affinity for silicon and its ability to diffuse through the Si-network. A preliminary analysis was made of the kinetics of the propagation reactions.
Comparison of Prolonged Light Soaking of Single and Stacked Junction A-SI:H Solar Cells
Authors: Lechner P. , Scheppat B. , Geyer R. , Rübel H. , Gorn M. , Kniffler N.
Published: March 2011

Light-induced degradation of a-Si solar cells is dependent on their design. The degradation rate for single cells increases with i-layer thickness. Very thin i-layer devices (d < 100 nm) exhibit a delayed onset of degradation which is accompanied by a severe loss of open circuit voltage at prolonged exposure times. By extrapolating i-layer thickness to zero and therefore separating bulk and interface effects, the latter may account for a substantial loss of stability. The introduction of a SiC buffer layer at the p/i interface results in a considerable higher degradation mainly caused by a loss in fill factor.

Double stacked cells, as compared to single cells having similar initial efficiences, show higher stability. The instability at extended exposure times of very thin single cells as used in a tandem configuration did not influence the stacked device.
Optical Degradation and Morphology in a-Si:H
Authors: Nakata Jun-ichi , Miyanishi Atsushi , Shirafuji Junji , Imao Shozo , Fujibayashi Keiji , Inuishi Yoshio
Published: March 2011

The relationship between the optical degradation and the morphology of hydrogenated amorphous silicon (a-Si:H) films was studied through the analysis of the annealing processes. The annealing of optically induced metastable dangling bonds can be explained in terms of the first and the second order reactions with dispersive hydrogen diffusion for the films deposited at lower and higher temperature, respectively. The activation energy of the annealing was estimated to be 0.8 eV with a small distribution in both cases. Optically enhanced annealing was first observed. It was found by DLTS and CT measurements that the density of hole trap located at Ev+0.6 eV was remarkably decreased by the light soaking, accompanied by the simultaneous increase of electron trap at Ec-0.7 ∼ Ec-0.9 eV due to the dangling bonds. These experimental facts support the view that the hole trap corresponds to the weak bonds, which convert to the metastable dangling bonds by light soaking.
SiC Multilayered Photoreceptor for Electrophotography
Authors: Nakayama Y. , Akita S. , Itoh H. , Yajima T. , Nakano M. , Kawamura T.
Published: March 2011

New multilayered photoreceptor consisting of all layers of a-Si1−xCx:H (x=0.1−0.8) has been developed on the basis of a high rate deposition process established using a glow discharge in a mixture of SiH4 and C2H2. This SiC photoreceptor is for negative charging and shows the excellent spectral sensitivity that is high in a short wavelength region and is reduced at the wavelengths longer than 600nm, suitable for the plain paper copier. The charge acceptance more than 40V/μn is achieved for the thickness less than 20μm. The charging characteristics are discussed in terms of deep emission states in the a-SiC:H.
Material Parameters in a Thick Hydrogenated Amorphous Silicon Detector and their Effect on Signal Collection
Authors: Qureshi S. , Perez-Mendez V. , Kaplan S. N. , Fujieda I. , Cho G.
Published: March 2011

Transient photoconductivity and ESR measurements were done to relate the ionized dangling bond density and the spin density of thick hydrogenated amorphous silicon (a-Si:H) detectors. We found that only a fraction (∼30–35%) of the total defect density as measured by ESR is ionized when the detector is biased into deep depletion. The measurements on annealed samples also show that this fraction is about 0.3. An explanation based on the shift of the Fermi energy is given. The measurements show that the time dependence of relaxation is a stretched exponential.
Observation of Random Telegraphic Noise in Large Area a-Si:H/a- Si1−x, Nx:H Double Barrier Structures
Authors: Arce R. , Ley L.
Published: March 2011

Random Telegraphic Noise (RTN) with an amplitude of about 1% has been observed in the current through a-Si:H/a-Si1−xNx.:H double barrier structures. The area of the devices, 0.25 mm2, is five orders of magnitude larger than the area of the devices where RTN has previously been observed. The power spectra of the noise can be fitted by a superposition of Lorentzians from which average switching times are deduced. The switching times are thermally activated with activation energies between 0.2 and 0.6 eV and depend on bias voltage. Assuming that the current through these structures is confined to microchannels of cross section area < lμm2 the RTN and its characteristics are explained by the random charging and discharging of individual traps placed in the vicinity of the current channel.
The Effect of Hydrogen Dilution of the Gas Plasma on Glow Discharge a-Ge:H
Authors: Turner W. A. , Jones S. J. , Lee Choochon , Lee S. M. , Li Yuan-min , Paul W.
Published: March 2011

A series of films of amorphous hydrogenated germanium has been produced using the r.f. glow discharge technique by varying the H2/GeH4 ratio in the gas plasma from 0 to 50 while keeping all other deposition parameters constant. Electronic, optical, and structural characterization has been performed. No significant changes in optical and electronic properties were observed for this range of dilution, in contrast to repeated reports on the hydrogenated silicon-germanium alloy system. However, small systematic changes in structure are observed using TEM techniques. We conclude that the observed differences are unimportant in determining the optical and electronic properties of this material.
High-Resolution X-Ray Characterization of Amorphous Semiconductor Multilayers
Authors: Persans P. D. , Ruppert A. F. , Abeles B. , Hughes G. , Liang K. S.
Published: March 2011

We discuss high-resolution x-ray diffraction measurements on a-Si:H/a-Ge:H periodic amorphous multilayers. Analysis of the data using the dynamical theory yields information on layer thicknesses and densities, interface and surface roughness, and structural defects such as layer thickness fluctuations.
Low Temperature Optically Induced Esr in a-Si:H and the Presence of Interface States
Authors: Ristein J. , Hautala J. , Taylor P. C.
Published: March 2011

Comparative studies of low-temperature (T ∼ 30 K) optically induced ESR using above gap red (633 nm) and below gap i.r. (1060 nm) light have been performed on several samples of a-Si:H. Experiments were performed on both films on quartz substrates and on powdered samples which were removed from the substrates. Excitation with red light always yields the well-known light induced ESR (LESR) spectrum which is ascribed to a superposition of two resonances: electrons trapped in conduction band-tail states and holes trapped in valence band tail states in a 1:1 ratio. On the other hand, excitation with i.r. light results in a different LESR spectrum with an enhanced feature overlapping with the signal attributed to trapped band-tail electrons. Although observed on all films studied on quartz substrates, this asymmetry is not observed in a powdered sample where only the band tail electron and hole resonances are observed in the ratio 1:1. This result suggests that interface states are responsible for the excess LESR spin density in the films on quartz substrates. Experiments performed as a function of film thickness confirm this interpretation.
Amorphous Silicon/Silicon Germanium Alloy Superlattices with Periods from 1 to 100 NM
Authors: Conde J. P. , Chu V. , Wagner S.
Published: March 2011

The electron and hole transport perpendicular to the plane of the layers in a-Si:H, F/a-Si, Ge:H, F multilayers is analyzed. We measure the electron dark conductivity σd and its activation energy Ea, d, the photo conductivity σph and its exponent γ, the electron and hole mobility-deep trapping lifetime (μτd)e, h and the hole mobility-recombination lifetime (μτr)h. We identify three regions of barrier thickness ds with very different transport properties: (a) ds≲50Å, dominated by tunnelling between quantum confined states in the bottom of the wells; (b) 50Å ≲ds≲200Å, in which the well acts as the provider of an extra, controllable tail state density; and (c) ds≳200Å, where the individual layers are essentially decoupled.
VHF-GD a-Si:H Films Prepared at Very Low Temperature
Authors: Ziegler Y. , Curtins H. , Baumann J. , Shah A.
Published: March 2011

Structural, optical and electrical properties of a-Si:H films prepared with the VHF Glow Discharge system were studied as function of deposition temperature, particularly in the range below 100°C. Usually, this material has poor optoelectronic properties. The a-Si:H material discussed in this work shows a surprisingly low hydrogen content, a low dihydride to monohydride ratio, good optical and electrical properties.
a-Si and μc-Si Grown from SiF4 with High H2 Dilution in a DC Glow Discharge
Authors: Okada Y. , Chen J. , Campbell I. H. , Fauchet P. M. , Wagner S.
Published: March 2011

a-Si and μc-Si were grown from SiF4 with H2 dilution in a DC glow discharge. The crystallinity of films deposited over a range of substrate temperatures and SiF4/H2 flow ratios was studied by Raman spectroscopy and the boundary between microcrystalline and amorphous Si was determined. We find that μc-Si can be grown from SiF4 with less H2 dilution than from SiH4. In the SiF4/H2 system, the etching by of F atoms appears responsible for μc-growth; H atoms play an important role in balancing growth and etching reactions.
Microcrystallinity in a-Si & a-SiC Films Made by Hg-Sensitized Photo-CVD
Authors: Saxena N. , Fortmann C. M. , Russell T. W. F.
Published: March 2011

A model for the role of H atoms as an etchant specie during deposition of microcrystalline (μc) films of Si:H and SiC:H is explored. Growth rates and etch rates of films made by Hg-sensitized photo-CVD have been measured as a function of reactor pressure (between 5 and 0.5 torr) and H2 dilution (up to 30:1). Gas phase reactions and diffusion to the substrate of depositing and etching species, have been modelled. It is found that high H radical flux (not necessarily high H2 dilution) promotes μc film growth. There are two surface etching reactions by H radicals: (i) selective etching of uncoordinated Si surface atoms (amorphous phase) from the film, leaving behind the more etch-resistant μc phase; (ii) in SiC:H alloy systems, a selective etching of C species, causing a decrease in C incorporation into the growing microcrystalline film. Films with increasing carbon content do not contain a μc-SiC phase because hydrogen is not eliminated from the carbon containing film precursors, thus inhibiting the development of crystalline Si-C network.
The Scientific Basis for Long-Term Prediction of Waste-Form Performance Under Repository Conditions
Authors: Mendel John E.
Published: March 2011

The reason for making long-term predictions of waste-form performance under repository conditions is to assess the impact of nuclear waste disposal upon the safety of future generations. Assessment of repository safety can be approached in two ways. One method is to define an acceptable release of radioactivity to the accessible environment, and to work back from that point to determine what kind of performance requirements are placed on the waste form. When this is done, it is found that the performance requirements for the waste form are not very restrictive. The waste form can dissolve completely in 100 to 10,000 years without affecting safety [1,2], because the repositories will be 300 meters or more underground. Radionuclide retardation on repository rocks and overburden and dilution during the long flow paths to the accessible environment become the controlling parameters.
The Functional Dependence of Leaching on The Surface Area-To-Solution Volume Ratio
Authors: Machiels Albert J. , Pescatore Claudio
Published: March 2011

The effects of the surface area-to-solution volume ratio on waste glass leach rates are investigated from a theoretical point of view. Simple leach models are discussed first. Correlation variables to interpret the results of similar leaching experiments performed at different values of the surface area-to-solution volume ratio are obtained for static leach testing. For dynamic leaching conditions, the source term required for risk assessment is derived and its dependence on the leachant flow rate and leach specimen surface area is discussed. The findings are upheld by a more complex leach model, the mathematical formulation of which has been implemented in a computer code named LIX. When tested against actual PNL 76–68 glass leaching data, LIX shows excellent capabilities in reproducing the experimental evidence, in particular the effects of the surface area-to-solution volume ratio.
Trench Water Chemistry at Commercially Operated Low-Level Radioactive Waste Disposal Sites
Authors: Pietrzak R. F. , Dayal R. , Kinsley M. T. , Clinton J. , Czyscinski K. S. , Weiss A. J.
Published: March 2011

Water samples from the disposal trenches of two low-level radioactive waste burial sites were analyzed for their inorganic, organic, and radionuclide contents. Since oxidation of the trench waters can occur during their movement along the groundwater flow path,experiments were performed to measure the chemical and physical changes that occur in these waters upon oxidation. In addition to the highly acidic conditions of the oxidized Maxey Flats trench water, low concentrations of chelating agents, shown to exist in trench waters, may be responsible for keeping radionuclides in solution following oxidation of anoxic trench leachates from Maxey Flats and West Valley burial sites.
Strontium Leachability of Hydrofracture Grouts for Sludge-Slurries
Authors: Morgan M. T. , Mcdaniel E. W. , Moore J. G. , Devaney H. E. , Dole L. R.
Published: March 2011

This paper summarizes a series of experiments to determine the strontium leachability of cement-based sludge-slurry hydrofracture grouts.

The hydrofracture process has been used at ORNL since 1966 for the routine disposal of intermediate-level waste (ILW) solutions. In this process, cement and other additives are mixed with a waste stream to form grout, which is then injected into a shale bed at a pressure sufficient to cause fracturing along the horizontal bedding planes. This injected grout soon hardens, fixing the radionuclides between layers of the massive Conasauga shale formation.

Modified IAEA dynamic leach tests on hydrofracture grout specimens showed improved leach resistance (by a factor of 3 to 5) as the curing time increased from 28 d to 91 d. A weak trend toward lower leachability with increased amounts of dry solids was observed.

The moving boundary-plus-diffusion leach model fits the dynamic leach data successfully in most cases. An apparent diffusion coefficient of 5 × 10−12 cm2/s and a moving boundary coefficent of 1 × 10−7 s−1 were obtained when one of the best grout compositions was leached in distilled water.
Electrical Conductivity Measurements of Leachates For The Rapid Assessment of Waste Form Corrosion Resistance
Authors: Sales B. C. , Petek M. , Boatner L. A.
Published: March 2011

Measurements of the electrical conductivity of leachate solutions as a function of time can be used as an efficient, informative means of evaluation and comparison in the development of nuclear waste forms and in the preliminary analysis of their corrosion resistance in distilled water. Three separate applications of this technique are described in this work. These are: (1) its use in the optimization of the corrosion resistance of a crystalline wasteform (monazite); (2) a study of the protective ability of the surface layer (“gel layer”) which forms on the nuclear waste glass Frit 21 + 20 wt. % SRW in distilled water, and (3) making comparisons of the overall corrosion resistance of three different nuclear wasteforms (i.e., monazite, SYNROC, and borosilicate glass). A complete solution analysis of the borosilicate glass leachate and a straightforward analysis of the conductivity results agree to within ±20%. In the absence of a complete, time consuming solution analysis, conductivity measurements can be used to estimate reliably the total ionic concentration in the leachate to within a factor of 2.
Suitability of Natural Geomedia for Radwaste Storage
Authors: Fyfe W. S.
Published: March 2011

Selection of the best rock types for radwaste disposal will depend on their having minimal permeability, maximal
flow dispersion, minimal chance of forming new wide aperture fractures, maximal ion retention, and minimal thermal and mining disturbance. While no rock is perfect, thinly bedded complex sedimentary sequences may have good properties, either as repository rocks, or as cover to a repository.

Long time prediction of such favorable properties of a rock at a given site may be best modelled from studies of in situ rock properties. Fracture flow, dispersion history, and geological stability can be derived from direct observations of rocks themselves, and can provide the parameters needed for convincing demonstration of repository security for appropriate times.
Technetium Behavior in Sulfide and Ferrous Iron Solutions
Authors: Lee Suk Y. , Bondietti Ernest A.
Published: March 2011

Pertechnetate oxyanion (99TcO4−), a potentially mobile species in leachate from a breached radioactive waste repository, was removed from a brine solution by precipitation with sulfide, iron, and ferrous sulfide at environmental pH's. Maghemite (γ-Fe23 ) and goethite (α-FeOOH) were the dominant minerals in the precipitate obtained from the TcO4−)-ferrous iron reaction. The observation of small particle size and poor crystallinity of the minerals formed in the presence of Tc suggested that the Tc was incorporated into the mineral structure after reduction to a lower valence state. Amorphous ferrous sulfide, an initial phase precipitating in the TcOÝ-ferrous iron-sulfide reaction, was transformed to goethite and hematite (α-Fe2O3 ) on aging. The black precipitate obtained from the TcOÝ-sulfide reaction was poorly crystallized technetium sulfide (Tc2S7 ) which was insoluble in both acid and alkaline solution in the absence of strong oxidants. The results suggested that ferrous- and/or sulfide-bearing groundwaters and minerals in host rocks or backfill barriers could reduce the mobility of Tc through the formation of less-soluble Tc-bearing iron and/or sulfide minerals.
Ion Implantation Damage in Silicate Glasses
Authors: Arnold George W.
Published: March 2011

Ion implantation is a rapid technique for simulating damage induced by α-recoil nuclei in nuclear waste forms. The simulation has been found to be quite good in TEM comparisons with natural α-decay damage in minerals, but leach rate differences have been observed in glass studies and were attributed to dose-rate differences. The similarities between ion implantation and recoil nuclei as a means of producing damage suggest that insights into the long-term behavior of glass waste forms can be obtained by examination of what is known about ion-implantation damage in silicate glasses. This paper briefly reviews these effects and shows that leaching results in certain nuclear waste glasses can be understood as resulting from plastic flow and track overlap. Phase separation is also seen to be a possible consequence of damage-induced compositional changes.
Radiolytic Gas Generation and Oxygen Depletion in Ion Exchange Materials
Authors: Capolupo Wayne P. , James M.S. , Sheff R.
Published: March 2011

The process of ion exchange is used extensively throughout numerous industries where water of extremely high purity is required. Government and commercial nuclear power facilities are typical of this, and have applied ion exchange processes for the removal of radioactive ions from aqueous solutions. When water is decontaminated in this fashion the ion exchange medium becomes saturated with the radioactive ions from solutions, and is then stored as radioactive waste in standard burial facilities. During this indefinite storage period, the chemical changes which occur in the ion exchange medium may result in oxygen depletion and gas generation within the storage vessel, and subsequent loss of integrity. It is the object of this work to investigate the early phases of radiolytic oxygen depletion and gas evolution through experimental procedure and observation. The results of this work will then be analyzed with respect to applications for the storage of radioactive ion exchange waste.
A Study of Coupled Thermomechanical, Thermohydrological and Hydromechanical Processes Associated with a Nuclear Waste Repository in a Fractured Rock Medium
Authors: Tsang C. F. , Noorishad J. , Wang J. S. Y.
Published: March 2011

It has been recognized that coupled thermomechanical, thermohydrologic, and hydromechanical processes may play an important role in the behavior of the geologic formation around a nuclear waste repository. A numerical code, ROCMAS, was recently developed at Lawrence Berkeley Laboratory to calculate coupled heat transfer, fluid flow, and mechanical deformation in a fractured porous medium. Three scoping studies using this model are described in this paper, with the following preliminary conclusions. The thermomechanical simulations of a fractured rock mass show that the fractures can absorb the thermally induced rock deformations, thus possibly explaining the observed behavior of the granite rocks in the experiment at Stripa, Sweden. The variations in fracture aperture profiles in the hydromechanical simulations indicate that the rigid fracture assumptions used in most uncoupled studies may not be a good representation of fracture behavior. The thermohydromechanical model study reveals that perturbations induced by a heater may close a fracture near the heater borehole and stop the water inflow to the borehole.
An Analysis of Waste Package Behavior for High-Level Waste
Authors: Chu Margaret S. , Campbell James E. , Stuckwisch Stephen E. , Wahi Krishan K. , Siegel Malcolm D.
Published: March 2011

The Environmental Protection Agency (EPA) has issued a draft standard (40CFR191) [1] which specifies permissible limits for radionuclide releases from a high-level waste repository to the accessible environment. The U. S. Nuclear Regulatory Commission (NRC) has published a proposed rule (10CFR60) [2] which contains technical criteria for geologic disposal of high-level waste to facilitate compliance with the EPA Draft Standard. The three main numerical criteria specified in 10CFR60 are:
Removal of Actinides From Waste Solutions by Ferrite Treatment
Authors: Boyd Thomas E. , Kochen Robert L.
Published: March 2011

Ferrite treatment was found to be effective in removing actinides from Rocky Flats process waste solutions. With one ferrite treatment, plutonium concentrations were consistently reduced from around 10−4 g/l to between 10−7 and 10−8 g/l. Three to four grams of solids were produced per liter of solution treated as compared to 15.7 g/l observed for the flocculant precipitation technique now in use at Rocky Flats. Less cement was required for the immobilization of ferrite solids resulting in further reductions in waste generation. The success of ferrite treatment in laboratory studies has prompted serious consideration of this technique for implementation in plant operations.
Theoretical Predictions For Continuous Slurry Feeding of a Glass Melter
Authors: Routt Kenneth R.
Published: March 2011

Radioactive defense waste currently stored at the Savannah River Plant in liquid form is to be immobilized by incorporation into a borosilicate glass. The glass melter for this process will consist of a refractory lined tank enclosed in a water-cooled, steel vessel and fed by an aqueous slurry of glass frit plus radioactive waste. As an aid to understanding the melting process and scaling data from small melters, conservation principles were used to develop equations for predicting the melt rate for a feedpile of arbitrary radius plus additional information regarding feedpile behavior and energy consumption.
Efficient Particulate Scrubber for Glass Melter Off-Gas
Authors: Wright G. T.
Published: March 2011

Operation of joule-heated, continuous slurry-fed melters has demonstrated that off-gas aerosols are generated by entrainment of feed slurry and vaporization of volatile species from the melt. Effective off-gas stream decontamination for these aerosols can be obtained by utilizing a suitably designed and operated wet scrubber system. Results are presented for performance tests conducted with an air aspirating - type venturi scrubber processing a simulated melter off-gas aerosol. Mass overall removal efficiencies ranged from 99.5 to 99.8%. Details of the testing program and applications for melter off-gas system design are discussed.
The Canadian Container Development Program For Fuel Isolation
Authors: Nuttall K. , Crosthwaite J.L. , Mckay P. , Mathew P.M. , Teper B. , Maak P.Y.Y. , Moles M.D.C.
Published: March 2011

Progress in the Canadian program to develop durable containment systems for the direct disposal of irradiated fuel in a deep geologic vault is described. Possible containment lifetimes, and the factors that influence container design and materials selection, are discussed. Most effort is currently directed toward developing containers with a design lifetime of about 500 years, using a corrosion-resistant metal shell to provide the primary barrier to radionuclide release. The design details for various containers are described, together with the fabrication and testing programs that are in progress or planned. The container materials programs consist of both generic research, to enable predictions of container performance to be made, and engineering development, to evaluate methods of container fabrication and inspection.
Diffusion of Radionuclides in Brine-Saturated Backfill Barrier Materials
Authors: Nowak E. J.
Published: March 2011

The diffusion of cesium(I), strontium(II), pertechnetate and europium in brine-saturated backfill materials was measured. Plastic diffusion cells containing cylindrical diffusion columns were used for low density backfill materials. The diffusion of gamma-emitters was followed by a gamma scanning technique. Metal diffusion cells constructed entirely from Hastelloy C-276 were used for the diffusion of pertechnetate in highly compacted bentonite. Apparent distribution coefficients calculated from diffusion data are (a) 0.02 m3 /kg for cesium(I) in 40 wt.% mordenite and 60 wt.% bentonite; (b) 0.04 m3/kg for strontium(II) in 10 wt.% sodium titanate and 90 wt.% bentonite; (c) 0.5 m3/kg for pertechnetate in 70 wt.% charcoal and 30 wt.% bentonite; and (d) 3 m3/kg for europium in 100% bentonite. Backfill effectiveness estimates based on batch sorption measurements were supported by these results;however, the diffusion results for europium did not agree well with a model for diffusion retarded by linear sorption. First measurements of pertechnetate diffusion in highly compacted bentonite suggest that anion exclusion may play a role in reducing mass transport rates of anions in this material. Needs for diffusion measurements that take into account site-specific materials interactions are described.
Internal Hydrogen Effects in Ti Code 12 Overpack/Cannister Material
Authors: Moody Neville , Robinson Steve
Published: March 2011

The effects of internal hydrogen on the mechanical properties of Ti Code 12 were studied by gas phase charging smooth bar tensile samples. Tensile tests showed no change in yield strength with increasing hydrogen concentration. A slight decrease in ductility and fracture stress at hydrogen concentrations above 200 wppm accompanied by secondary cracking along grain boundaries indicated embrittlement. At hydrogen concentrations near and above 400 wppm, cleavage fracture associated with strain-induced hydrides was also observed.
The Microstructural Response of a Multilayer Thin Film to Local Laser Heating
Authors: Libera Matthew R. , Chen Martin , Rubin Kurt A.
Published: March 2011

The microstructures associated with pulsed-laser heating of multilayer thin films used for phase-change optical data storage are studied in three related films. Two employ the multilayer structure SiOx/TeGeSn/SiOx where the chalcogenide layer is either amorphous or crystalline. The third uses the same trilayer structure with a crystalline chalcogenide layer but with an additional layer of aluminum. Pulsed-laser melting of micron-sized spots leads to solidification in the non-aluminized specimens with a morphology dependent on the preexisting structure of the chalcogenide layer and to amorphization in the aluminized film. Heat-flow modelling shows that the maximum temperature reached is lower and the cooling rate through the glass-forming temperature range higher in the aluminized structure. Discussion centers on the thermal and optical properties of the different films and the impact of the pre-existing chalcogenide structure on the subsequent phase transformations.
Chemical Effects Induced by Low-Energy Particle Beams in Fluorozirconate Glasses
Authors: Marletta Giovanni , Ferraris Monica
Published: March 2011

The modification of the chemical structure of fluorozirconate glasses (ZBLAN) with Ar ion and atom beams of low energy (2–10 key) has been studied in comparison with the damage produced in the starting polycrystalline ZrF4 and BaF2. A variety of reduced chemical states of Zr is produced in ZrF4 as well as in ZBLAN glasses, including metallic Zr0 state. A strong enhancement of the amount of the metallic Zr formed under irradiation is observed in ZBLAN, while it is present only as trace in the irradiated pure ZrF4 samples. The reported effect is tentatively attributed to the presence of Ba ions in the glass network which could prompt the self-trapping of radiation-induced defects at the Zr sites, involving their progressive reduction
Ferroelectric Thin Films by sol-gel Processing
Authors: Swartz S. L. , Melling P. J. , Grant C. S.
Published: March 2011

The sol-gel processing of ferroelectric thin films is being investigated at Battelle. The ferroelectric materials included in this study are PbTiO3, Pb(Zr, Ti)O3 (PZT), and KNbO3. The sol-gel processing and crystallization of these films on fused silica, silicon, alumina, and single crystal SrTiO3 substrates is described.

Sol-gel derived PbTiO3 thin films crystallized into the expected tetragonal perovskite structure when heated to 500 C and above. However, the crystallization of sol-gel PZT (20/80) thin films was found to be substratedependent. The heat-treated PZT films were amorphous when deposited on silica and silicon substrates. Crystalline perovskite PZT films were produced on alumina substrates, and epitaxial PZT films were produced on single-crystal SrTiO3. Heat treatment of sol-gel KNbO3 films on silicon and alumina substrates resulted in the crystallization of a variety of non-perovskite phases, but epitaxial growth of KNbO3 was observed on single crystal SrTiO3.
Ion implanted electrooptical waveguides
Authors: Bremer T.
Published: March 2011

The influence of ion beam induced lattice damage on the refractive indices is evaluated for He+ implanted planar waveguides in lithium niobate (LiNbO3) and potassium niobate (KNbO3 ). KNbO3 exhibits a higher sensitivity for ion beam induced refractive index alterations. In order to suppress leaky modes, varying angle implantation has been applied. The annealing of electronic damage in both crystals is compared. While it requires heating up to 200°C for LiNbO3, the electronic damage in KNbO3 has been found to anneal at much lower temperatures. Annealing takes place even at room temparature, the electronic damage vanishes almost completely within 100 days.
The Chemistry and Physics of Nonlinear Optical Materials: A new look at an Old Field
Authors: Velsko Stephan P. , Eimerl David
Published: March 2011

Recent efforts to “engineer” new nonlinear optical materials with specific desired characteristics has engendered a need for a theoretical description of optical properties which is readily accessible to chemists, yet correctly treats the essential physics of dielectric response. This paper describes a simple empirical molecular orbital model which gives useful insights into the relationship between chemical composition, crystalline structure, and optical susceptibilities. We compare the probabilities of finding new harmonic generators in various chemical classes. Rigorous bounds on the magnitudes of linear and nonlinear optical coefficients and their anisotropies are also discussed.
The use of the Piezoelectric Composite Oscillator Technique for Measuring the Viscoelasticity of Liquid Crystals
Authors: Giacomin A. J. , Wolfenden A. , Fairbrother D. A. , Seet T. B. , Karis T. , Twieg R. J.
Published: March 2011

The development of liquid crystalline mixtures with short electro-optic switching times has made possible an array of new products, including hand-held televisions and lap-top computers with flat panel displays. Whereas the switching times for materials with long switching times has been correlated with their steady shear viscosities, this is not true for materials with short switching times. Since such materials exhibit viscoelasticity in dynamic tests conducted at ultrasonic frequencies, we expect the dynamic moduli to correlate with their switching times. The viscoelastic properties of pure MBBA were measured using a piezoelectric ultrasonic composite oscillator technique. The measurement technique and the relation between the linear viscoelastic behavior and the electro-optic switching behavior will be discussed.
Ion Implantation of Ti INTO LiNbO3: Fabrication of Waveguides and Simple Modulators
Authors: White C. W. , Thomas D. K. , Ashley P. R. , Chang W. S. C. , Buchal C.
Published: March 2011

Ion implantation has been used to introduce Ti at very high doses (>3 × 1017 /cm2) into the near-surface region of LiNbO3 to change the index of refraction.’ In the as-implanted state, the near surface is amorphous. Thermal annealing in water-saturated oxygen 1000°C crystallizes the amorphous region and incorporates the Ti into substitutional sites in the lattice at concentrations that exceed 10 at.%. Recrystallization takes place by solid-phase epitaxy. Both planar and channel waveguides have been fabricated with optical attenuations of <1 dB/cm. Both Mach-Zehnder and Bragg modulators have been fabricated using Ti implantation of LiNbO3. The characteristics of these devices have been determined and will be reported. The higher Ti concentrations which can be achieved by implantation allows tighter mode confinement and smaller mode profiles than with Ti-diffused guides.
Growth and Structural Characterization of Znse Single Crystals
Authors: Anderson Elmer E. , Cheng Hai- Yuin , Edgell Michael J.
Published: March 2011

Single crystals of ZnSe have been grown by the physical vapor transport method in sealed quartz ampoules. The largest crystal grown measures 1 cm x 4 mm x 2 mm and required a total growing time of 11 days. Polished wafers cut from the crystals have been etched and examined by optical microscopy, x-ray diffraction, scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and scanning Auger microscopy (SAM). No impurities or unwanted phases were detected, but frequent twinning occurs. Zn-rich {111} faces were identified by SAM. Triangular etch pits are observed on Zn {lll} faces but not on Se faces. Etch pit densities are about 104 per cm2 on slow-cooled samples but are about 100 times greater when cooling is more rapid.
Crystal Chemistry, Synthesis, and Characterization of Infrared Optical Materials
Authors: Kipp D. O. , Lowe-Ma C. K. , Vanderah T. A.
Published: March 2011

Non-oxide inorganic compounds such as sulfides, phosphides, and mixed-anion sulfidephosphides are of interest as possible infrared window materials. Our research on the solid state chemistry and structure-property relationships of these materials includes the directed synthesis of new compounds as well as the study of compounds that have been reported in the literature but which have been incompletely characterized for this application. The present work includes investigations of three ternary sulfide systems: ZnGa2S4, AIn2S4, (A = Ca,Sr,Ba), and CaY2S4. Samples were prepared in polycrystalline form and/or as crystals. New compounds were obtained in our studies of the CaIn2S4, SrIn2S4, and CaY2S4 systems. Compounds were characterized by X-ray diffraction, elemental analysis, FMR, and thermogravimetric analysis.
Point Defects in LiNbO3: Where do we Stand Today?
Authors: Agulló-López Fernando
Published: March 2011

Ternary electrooptic oxides, with structures related to that of the perovskite, are used or being considered for potential utilization in optoelectronics technology [1,2]. Typical applications include electrooptic and acoustooptic modulators and switches, SAW and optical waveguide devices, non-linear optical components and pyroelectric and luminescent radiation and particle detectors. The use of these oxides as laser hosts has also often been contemplated.
Structure and Nonlinear Optical Properties of Glasses for Photonic Switching
Authors: Vogel E. M. , Krol D. M. , Jackel J. L. , Aitchison J. S.
Published: March 2011

The possible use of glasses as the nonlinear optical material in all-optical switching calls for glasses with nonlinear refractive indices much higher than those of vitreous silica. Relatively high values of the nonlinear index coefficient, n2, have been found in Na2O-TiO2-Nb2O5-SiO2 glasses, in which n2 is completely dominated by the Ti-O and Nb-O bonds. We have investigated the nonlinear optical properties of R2O-TiO2-Nb2O5-SiO2 glasses as a function of the monovalent ion R (Na, K, Rb, Cs, TI). The results show that the dependence of n2 on R is larger than predicted from the empirical relation between n2 and n. An especially large enhancement of n2 is seen for T1. This can be explained by the difference in electronic configuration between TI (unfilled shell) and the alkali ions (filled shell).
”Automatized” Peel Testing: Calculated Stresses and Deflections in the Film
Authors: Suhir Ephraim
Published: March 2011

Film adhesion, which is an important reliability factor in many microelectronic structures, is usually evaluated by peel testing. The loading and the peel angle in peel tests can be controlled best if these tests are “automatized”, which could be done, for instance, by applying air pressure to a film through an opening in the substrate. We consider a rectangular opening and determine, how this pressure is related to the peel (membrane) loading and peel angle for the given film material and thickness. Our study is based on von-Kármán's equations for large deflections of plates. The obtained results provide mechanical fundamentals for a rational physical design of a peel test vehicle.
Low Temperature Route to Cordierite Ceramics Using a Reactive Liquid Phase Sintering Aid. Dense Body Preparation and Green Tape Fabrication
Authors: Dupon Ryan W. , Mcconville Richard L. , Thompson Mark S.
Published: March 2011

Bismuth oxide has been found to be a useful flux for the preparation of dense body cordierite (Mg2Al4Si5O18). The use of as little as 2 atom% bismuth ion with the appropriate mixture of commercially available oxide starting materials serves to produce fully dense crystalline cordierite after firing at 1000 °C. The microstructure of the sintered body (92 w/o% cordierite, 8 w/o% bismuth oxide) has the residual bismuth oxide flux distributed in discontinuous domains at the grain boundaries and at the triple points. Physical properties such as thermal coefficient of expansion and dielectric constant are largely unperturbed by the presence of the flux.

Green tapes having high volume fraction solids loading have been fabricated from bismuth oxide-cordierite precursor powders. The subsequent firing at 1000 °C of laminated green tapes yields fully dense ceramic bodies of crystalline cordierite.
Mullite Ceramics for the Application to Advanced Packaging Technology
Authors: Tanaka Jun , Kajita Satoshi , Terasawa Masami
Published: March 2011

Mullite ceramics were developed for multilayered packages, which have a lower dielectric constant and a nearer thermal expansion to that of silicon than those of alumina. The multilayered mullite packages are manufactured by using a similar cofired technology with tungsten or molybdenum to the conventionally used alumina system. A new brazing material and a new lead material were developed to be combined with the mullite ceramics Multilayered mullite packages with a brazed aluminum nitride heat sink, which has a high thermal conductivity, were developed to compensate a low thermal conductivity of the mullite itself. The packages are one of the highest performance packages.
Ceramics in Microelectronics Packaging: Past, Present and Future
Authors: Tummala Rao R.
Published: March 2011

A broad review of ceramics in microelectronics for processing, storing, transferring, printing, and displaying information is highlighted. Ceramic packaging is presented with a review of the history, evolution, and state of the art. The recent developments in ceramics resulting in potentially improved thermal and electrical properties by the use of SiC, AIN, and glass±ceramics are discussed. The scientific understanding necessary to support these developments is mentioned.