bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamic Simulation and Electrical Properties of Ba2In2O5
Authors: Kanzaki Masami , Yamaji Akihiko , Kawakami Kazuya
Published: April 2011

Brownmillerite(Ca2Al2O5-Ca2Fe2O5 solid solution) structure can be regarded as an oxygen-ion deficient perovskite structure. Because of high proportion of the oxygen vacancies in the structure, this material could be a candidate of fast oxide-ion conductor. Goodenough et al. indeed observed a first-order transition to a fast oxide-ion conductor at 930° C for Ba2In2O5 which adapts brownmillerite structure at ambient temperature. Molecular dynamics simulation was employed to study oxygen ion diffusion and phase transition of Ba2In2O5. The structure was well simulated at 300 K. When the system was heated, the original orthogonal cell transformed to a tetragonal cell at 2300 K. Inspection of the structure revealed that oxygen ions started to migrate from their original sites to nearest vacant oxygen sites at this temperature. The diffusion was restricted for the oxygen sites around In-tetrahedron, resulting highly anisotropie diffusion on the ac plane. At 4600 K it further transformed to an oxygen vacancies-disordered cubic perovskite structure. Although predicted transition temperature were apparently overestimated, the transition way to the phases with high oxygen ion diffusivity is consistent with the experimental results from electrical conductivity measurements. The high temperature cubic phase shows large ion conductivity. It is of interest to examine whether or not the cubic phase stabilizes in the low temperature region by making solid solution of another elements. We found that the cubic phase is stabilized below 500° C without any decrease of conductivity in BaIn1.9Ce0.1Oy and Ba2In1.8Nb0.2O5.
Mechanisms Causing Capacity Loss on Long Term Storage in NiMH System
Authors: Singh P. , Wu T. , Wendung M. , Bendale P. , Ware J. , Ritter D. , Zhang L.
Published: April 2011

Capacity recovery after long term storage and loaded storage is a critical issue with the NiMH system since its inception. A measurable loss in capacity is observed when cells are stored for long periods of time or discharged deeply to zero volts. The different mechanisms that are known to cause self discharge and capacity loss after storage and loaded storage will be the focus of this paper. Capacity loss after long term storage involves two main events. One is self discharge which causes the open circuit voltage(OCV) of the cell to drop. Self discharge is caused by decomposition of NiOOH, migration of metal ions and possible degradation of separator. Self discharge can be prevented by using separators which are stable at high temperatures and pH and have good ion trapping capability. Various separator types and treatments can play an important role in inhibiting metal ions from migrating thus reducing self discharge. Self discharge during storage causes a severe suppression in the voltage of the foam positive electrode. This drop in voltage causes a breakdown of the cobalt conductive network in the nickel positive electrode. Reduction of high valence cobalt(III) which forms the electrode's conductive network takes place at these low voltages. A permanent breakdown in the conductive network results in low efficiency of the cell on consecutive charge and discharge cycles. In addition, the cobalt in its lower valence states can migrate away from the electrode into the separator causing shorts. These events effect the charge and discharge efficiency of these cells thereby resulting in capacity loss. Various mechanisms causing self discharge which affect capacity recovery after long term storage and loaded storage are discussed in this paper.
Phase Transition of LiMn2O4Spinel and its Application for Lithium Ion Secondary Battery
Authors: Tabuchi Junji , Numata Tatsuji , Shimakawa Yuichi , Shirakata Masato
Published: April 2011

LiMn2O4has a phase transition at room temperature, which is caused by Jahn-Teller distortion. DC resistivity of LiMn2O4shows an anomaly at the transition temperature, while no such anomaly is observed in samples with excess lithium. X-ray diffraction patterns of LiMn2O4reveal that the crystal structure changes from cubic at higher temperature to orthorombic, as a first approximation, at lower temperature. However, no differences in initial charge-discharge curve are observed, which means that the Jahn-Teller distortion has no effect on electrochemical characteristics. The authors have succeeded in mass-producing lithium ion secondary batteries with a manganese spinel cathode.
Application of potentially biodegradable polyamide and polyester containing disulfide bonds to positive active materials for lithium secondary batteries
Authors: Tsutsumi H. , Okada S. , Toda K. , Onimura K. , Oishi T.
Published: April 2011

Potentially biodegradable polyamide (poly(imino-3, 3'-dithiodipropionylimmo-2, 2'-dithiodiethyl), -(NHCOCH2CH2-S-S-CH2CH2CO-NHCH2CH2-S-S-CH2CH2)n-, PIDI) and polyester (crosslinked poly(oxy-3, 3'-dithiodipropionyloxymethylene-l,4-phenylenemethylene,-(ICOCH2CH2-S-S-CH2CH2COO-CH2-C6H5-CH2)n-c-PODOM)) were prepared by interfacial polymerization between 3,3'-dithiodipropionic acid and cystamine, or 1, 4-benzenedimethanol. PIDI and c-PODOM showed the electrochemical responses based on reduction of the disulfide bonds in the polymer chains and re-oxidation of the produced thiolate anions. Degradation of PIDI and PODOM was investigated in various pH buffer solution. The apparent rate constant of c-PODOM at 25 °C was 1.3 × 103% day−1at pH 7 and that of PIDI at 37 °C was 3.5 × 103% day−1at pH 7. Estimated period for 90 % degradation of the polymers at pH 7 is about 1800 days (c-PODOM, 25 °C) and 630 days (PIDI, 37 °C).
Preparation and Battery Applications of Micron Sized Li4Ti5O2
Authors: Peramunage D. , Abraham K. M.
Published: April 2011

The objective of this study was to highlight the usefulness of micron-sized Li4Ti5O12 in three distinctive areas: a) cathode of a low-voltage Li battery, b) insertion type auxiliary electrode to investigate the electrochemistry of oxide cathode materials, and c) anode of a Li-ion cell in conjunction with LiMn2O4 cubic spinel cathode. Li cells with Li4Ti5O12 exhibited an open circuit voltage of ∼1.6V, >90% utilization (in terms of the theoretical capacity) at ∼C/10 rate, ∼40% utilization 5C rate, and extended full-depth charge/discharge cycling at ≥ 1C rates with virtually no capacity fade. LiMn2O4 cathodes, evaluated in Li(4+xTi5O12 (x = ∼1.2)/LiMn2O4 cells, exhibited extended full-depth cycling capability with a small capacity fade rate of <0.1% which appeared to slow down with cycling. At a 1C discharge rate, over 190 cycles were demonstrated corresponding to an end utilization of ∼90 mAh/g or ∼0.6 mole Li per LiMn204. Balanced Li4Ti5O12//solid polymer electrolyte//LiMn2O4 full cells of slightly cathode-limited configuration had an open-circuit voltage of ∼3.0V and a mid-discharge voltage of ∼2.5V showing full-depth extended cycling capability at a utilization of ∼90 mAh/g or ∼0.6 mole Li per LiMn204 at the 1C and ∼0.45 mole Li per LiMn2O4 at the 7.5C discharge rate.
Structural Phase Transformations in V2O5 Thin Film Cathode Material for Li Rechargeable Batteries
Authors: McGraw J. M. , Perkins J. D. , Zhang J.-G. , Parilla P. A. , Ciszek T. F. , Fu M. L. , Trickett D. M. , Turner J. A. , Ginley D. S.
Published: April 2011

We report on investigations of V2O5 thin film cathodes prepared by pulsed laser deposition and the phase transformations which occur during electrochemical cycling. Our experimental results on PLD-grown, textured V2O5 crystalline films concur with reports in the literature that there is a voltage threshold above which, cycling appears to be completely reversible and below which, cycling appears to be irreversible. Crystalline films discharged beyond the threshold to 2.0 V vs. Li exhibited an immediate and continuous fade in capacity as well as a ∼90% decrease in XRD peak intensity and a similar decrease in Raman signal intensity in as few as 10 cycles. We have made co-phase material by both electrochemically discharging virgin, crystalline V2O5 and by further discharging previously cycled films which showed irreversible structural changes.
Effects of Aluminum Doping on The Phase Stability and Electrochemical Properties of LiCoO2 and LiMnO2
Authors: Jang Y.-I. , Huang B. , Wang H. , Chiang Y.-M. , Sadoway D. R.
Published: April 2011

Aluminum is of interest as a constituent for Li battery electrodes due to its low cost and low mass, and because ab initio calculations indicate that solid solution of LiAlO2 with LiMO2 (M = transition metal) in the α-NaFeO2 structure can increase intercalation voltage [1]. In this study, we investigated the effect of Al doping on LiCoO2 and LiMnO2. Single phase LiAlyCo1-yO2 has been synthesized up to y = 0.5 by firing homogenous hydroxide precursors. A systematic increase in the open circuit voltage is observed with Al content. In LiAlyMn1-yO2, the addition of LiAlO2 stabilizes LiMnO2 in the α-NaFeO2 structure under conditions where neither endmember is stable in the structure. High reversible capacity was obtained over both a 4 V and 3 V plateau, indicating that the compound transforms to a spinel-related structure during cycling, but that the cooperative Jahn-Teller distortion is suppressed.
Effect of HF in LiPF6 Based Electrolytes on the Properties of Surface Passivation Films Formed on Graphite Electrodes in Li Secondary Batteries
Authors: Sato T. , Deschamps M. , Suzuki H. , Ota H. , Asahina H. , Mori S.
Published: April 2011

The effect of hydrofluoric acid (HF) concentration in conventional LiPF6/EC+DEC electrolyte on the properties of solid electrolyte interphase (SEI) films formed on synthetic graphite electrode and the electrochemical performance were studied using x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), elemental analysis and electrochemical measurement. The morphology and composition of SEI are affected by a small amount of HF in the electrolyte. Higher F content in the SEI was observed when high HF electrolyte were used, although the irreversible capacities used for formation of SEI were nearly the same value. The cycleability of the synthetic graphite electrode was greatly improved when surface film contains larger amount of LiF.
Growth and Electrochemical Characterization of Single Phase MoxN Films for the Fabrication of Hybrid Double Layer Capacitors
Authors: Roberson S. L. , Evans D. , Finello D. , Davis R. F.
Published: April 2011

The electrochemical stability and capacitance in H2SO4, KOH, and propylene carbonate of single phase polycrystalline γ-Mo2N and δMoN thin film electrodes deposited at 350 and 700° C, respectively, at a rate of 0.5 μm/min on Ti substrates have been determined. The films were prepared by chemical vapor deposition at 100 torr using Mo(CO)6 and NH3 flowing at 1.5 standard liters per minute (slm). Cyclic voltammetry referenced to a standard Ag/AgCl electrode indicated that both phases possessed a more positive voltage stability limit in H2SO4 than KOH. Films of γ-Mo2N had voltage stability ranges of -0.3 to 0.6 V and -1.3 to - 0.3 V in 4.4 M H2SO4 and 7.6 M KOH, respectively. Films of δ-MoN possessed voltage stability ranges of -0.3 to 0.7 V and -1.3 to -0.3 V in the same respective electrolytes. Both phases had a voltage stability of approximately one volt in the propylene carbonate electrolyte. These results were used to design and fabricate a hybrid capacitor composed of a Ta/Ta2O5 anode and a δ-MoN cathode contained in an electrolyte of 4.4M H2SO4. The hybrid device had an operating voltage range between 0 and 50 V, a temperature range of -55 to + 90°C, a capacitance of ≈ 5.0 mF and an energy density of ≈ 1.32 J/cm3. This device is now in pre-production at Evans Capacitor Corporation.
Anodic Oxidation of Nitrogen-Added Al-Based Alloys for Thin-Film Transistors
Authors: Arai Toshiaki , Iiyori Hideo
Published: April 2011

Novel anodized films of nitrogen-added aluminum-based alloys were proposed for use in the fabrication of gate insulators for thin-film transistors, and the effect of nitrogen addition on the anodized aluminum-based alloys was investigated. Gadolinium and neodymium were employed as alternative alloy components. The film thickness, the dielectric constant, and the roughness average of the anodized films decreased as the nitrogen content increased, and the nitrogen content was required to be lower than 20 at.%. The most improved values of the breakdown electric fields of anodized aluminum-gadolinium and aluminum-neodymium alloy were 10.1 MV/cm with 6.0 at.% nitrogen content and 9.9 MV/cm with 4.0 at.% nitrogen content, respectively. The leakage currents of the anodized films under a negative bias, which could not be suppressed by high-temperature annealing, were adequately suppressed by nitrogen addition, especially in anodized aluminum-gadolinium alloy. The current leakage of the anodized aluminum-gadolinium alloy with 6.0 at.% nitrogen content became -8E-13 A at -10 V and 150°C. This value is nearly equal to that of chemical-vapor-deposited (CVD) films.
Computer Simulation of ZnO Varistors Failures
Authors: Bartkowiak M. , Mahan G. D. , Comber M. G. , Alim M. A.
Published: April 2011

A simple thermo-mechanical model is applied to evaluate the influence of the nonuni-formity of ZnO varistor disks used in surge arresters on their energy handling capability. By solving heat transfer equations for a varistor disk with nonuniform electrical properties, we compute the time dependence of the temperature profile and the distribution of thermal stresses. The model can identify the energy handling limitations of ZnO varistors imposed by three different failure modes: puncture, thermal runaway, and cracking. It conforms to the available failure data, and explains the observation that energy handling improves at high current densities.
A Novel Approach to Semiconductor Electrical Properties - The Advanced Method of Transient Microwave Photoconductivity (AMTMP)
Authors: Grabtchak S. , Cocivera M.
Published: April 2011

The advanced method of transient microwave photoconductivity (AMTMP) represents a new method based on cavity perturbation theory, microwave photoconductivity and harmonic oscillator model analysis. AMTMP provides a direct observation of changes to the complex dielectric constant, and free and trapped electron decays can be studied separately. The results obtained for polycrystalline CdSe thin films clearly indicate that a multiple trapping model developed for amorphous materials does not provide a satisfactory description. For SI GaAs the harmonic oscillator model provides a quantitative interpretation. The limitations are discussed for the application of this method to porous Si.
Evaluation of Gap States in Hydrogen-Terminated Silicon Surfaces and Ultrathin SiO2/Si Interfaces by using Photoelectron Yield Spectroscopy
Authors: Miyazaki S. , Tamura T. , Maruyama T. , Murakami H. , Kohno A. , Hirose M.
Published: April 2011

The energy distributions of gap state densities for H-terminated Si surfaces and thermally-grown SiO2/c-Si interfaces have been evaluated by total photoelectron yield spectroscopy (PYS) with a dynamic range of eight orders of magnitude which is sufficient to detect the density of states as low as 1010cm−2eV−1. It is confirmed from the threshold energies for direct and indirect photo-excitations that, for monohydride-terminated Si(111) surfaces prepared by an NH4F treatment, no significant band-bending is observable. For H-terminated n-type sample, the gap state densities of the order of 1011cm−2eV−1 were estimated in the region within 0.4 eV from the valence band edge, which may be attributable to a very little oxidation in the sample preparation. It is also found that, for as-grown 2.5nm-thick SiO2/n+ Si, there exist interface states around midgap with densities as high as ∼1012cm−2eV−1.
The Influence of Ionic Activity on the Electrical Properties of PECVD (TEOS) Silicon Dioxide
Authors: Romanelli Cardoso A. , Pereira Da Silva M. L. , Santiago-Aviles J. J.
Published: April 2011

A Plasma enhanced CVD system was modified to place a potential screen between a plasma and a silicon wafer. Silicon dioxide from an organometallic precursor (TEOS) was deposited onto silicon wafers. In this way, any alteration of the screen potential resulted in a modified ion speed, or the removal of the ion flux incident on the wafer. The oxides films produced in this manner were analyzed by Raman spectroscopy, and both C-V and I-V techniques. The characterization results suggest an important role for Oxygen ion bombardment on the TEOS oxidation process, such as the removal of carbon compounds from the film as TEOS oxidizes. We have evidence that ion bombardment decreases the dielectric constant and increases the hysteresis of the SiOx films. A qualitative model to explain the experimental results was developed.
Silicon Rapid Thermal Processing with Ripple Pyrometry
Authors: Fiory A. T.
Published: April 2011

Thermal processing in silicon integrated circuit fabrication steps for dopant activation, metal silicides, annealing, and oxidation commonly uses single-wafer furnaces that rapidly heat wafers with incandescent infrared lamps. Radiation pyrometers and thermocouple probes are the principle methods of measuring wafer temperature for closed-loop control of rapid thermal processes. The challenge with thermocouples is in dealing with heat from the lamps and non-ideal thermally resistive wafer contact. The challenge with pyrometry is in compensating for the variable emissivity of wafer surfaces and suppressing interference from the lamps. Typical deposited or grown layers of silicon nitride, silicon dioxide, and polycrystalline silicon can produce dramatic changes in emissivity. Layer thicknesses and composition are generally not known with sufficient accuracy, so a method for real time in situ emissivity compensation is required. Accufiber introduced a “ripple technique” to address this issue. The idea is to use two probes, separately sensing radiation from the wafer and the lamps, and extracting AC and quasi-DC parts from each. The AC signals provide a measure of the reflectivity of the wafer, and thence emissivity, as well as the fraction of reflected lamp radiation present in the DC signals. Lucent Technologies introduced a method of using AC lamp ripple to measure wafer temperatures with two radiation probes at a wall in the furnace. One probe views radiation emanating from the wafer through a gap in the lamp array. The other probe has a wide field of view to include lamp radiation. The accuracy of Lucent devices, determined from process results on wafers with various emissivities, is typically in the range of 12°C to 18°C at three standard deviations.
Monitoring and Control in Vapor phase Epitaxy
Authors: Pearsall T. P.
Published: April 2011

Monitoring and control in epitaxy based on chemical vapor deposition is a challenge created by growth conditions that often preclude more common sensors like thermocouples and mass spectrometry. We report results of experiments to measure and control temperature and flux by non-invasive optical sensing. We have developed a temperature control system with precision and accuracy better that 5°C. Satisfactory control of flux poses difficulties that will require innovative solutions before a useful control system can be developed.
Polycapillary Optics for in Situ Diagnostics
Authors: Hofmann F. A. , Gao N. , Owens S. M. , Gibson W. M. , Macdonald C. A. , Lee S. M.
Published: April 2011

Polycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, are used to redirect, collimate, or focus x-ray beams from conventional laboratory-based sources. Focused spot sizes as small as 20μm have been measured, with flux densities two orders of magnitude larger than that produced by pinhole or crossed slit collimation. Such flux increases have made possible faster and more sensitive x-ray fluorescence (XRF) and diffraction measurements to the extent that in situ measurements become possible. XRF data taken with a 12 W source were comparable to data taken with a 1.5 kW source. Ex situ diffraction and texture measurements on thin multilayered films and single crystal silicon demonstrate the tremendous experimental and analytical improvements made possible by polycapillary optics.

With 0.5° and 2° focusing polycapillary x-ray optics, diffraction intensity gains of more than two orders of magnitude were measured on small Lysozyme protein crystals with exposure times an order of magnitude less than required by traditional measurement techniques

In addition, the optics greatly reduce the background high energy Bremsstrahlung, permitting more accurate analysis of thin complex multilayer diffraction peaks. Rapid measurement times resulting from the application of these polycapillary optics, indicate tremendous possibilities for in situ process monitoring
In-Situ Fourier Transform Infrared Spectroscopy for Real-Time Diagnostics of Thin Film Processes
Authors: Solomon P. R. , Charpenay S. , Zhang W. , Bonanno A. S. , Rosenthal P. A. , Cosgrove J. E. , Kinsella K. K , Kung P. J.
Published: April 2011

Infrared spectroscopy is a versatile tool that is well adapted to in-situ diagnostics of many thin film properties and processes. In this paper, we will describe the application of infrared instrumentation for real-time in-situ measurements of film temperature, emissivity, thickness, free carriers, and optical constants using model based spectral analysis. We will illustrate the use of Fourier transform infrared (FT-IR) emission and reflection spectroscopy to monitor the fabrication of stacks of ferroelectric and conductive oxides on silicon substrates during pulsed laser deposition. The ability to measure the infrared optical constants of dielectrics such as silicon dioxide, including the detailed spectral dependence of the vibrational absorption bands at high temperatures, will be presented. The suitability of the technique for real-time sensing during rapid thermal processing will be illustrated using the example of carrier activation during a shallow-junction rapid thermal anneal.
Microanalysis of Soot Particulates using Stem
Authors: Bell David C. , Rainey Lenore C. , Palotás ÁrpÁd B. , Vandersande John B.
Published: April 2011

Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) and electron energy-loss spectroscopy (EELS) has been used to characterize the elemental composition and oxidation conditions of various soot samples. The STEM employed in this investigation was the Vacuum Generators HB603, with a microanalytical resolution approaching 1 rnm, that allowed the analysis of individual soot particles and aggregates. The aim of this research is quantification of the EDX spectra which is possible after background and absorption corrections. This information can then be used for comparative studies of different fuels and combustion processes. EELS has been employed to determine the amount of graphitic carbon in a soot particulate, and the detection of trace elements of low atomic number. It has been shown in soot that for Carbon the energy-loss of the p shell electrons increases with the amount of oxidation at high temperatures. Analysis and characterization of gas turbine soot, collected from an engine exhaust duct of a 737-300 aircraft showed an abundance of different elements. Some of these elements originated from the fuel and combustion processes, while other elements were components of the engine itself that combined with the soot particulates during the combustion process. The study showed that soot impurities were found in all discrete sections of aggregates, and that only one or two small soot particulates were necessary to obtain a chemical fingerprint. Other investigations include; coal soot, diesel soot at different engine operating conditions and soot produced from wood burning. The richness of the spectra obtained and the ability to quantify results represents an opportunity to accomplish source identification in a novel, powerful way.
SPA Monitoring of GaN Movpe Surface
Authors: Kobayashi Naoki , Kobayashi Yasuyuki
Published: April 2011

For the purpose of clarifying the growth mechanism of GaN metal-organic vapor phase epitaxy (MOVPE), the GaN surface during the growth on the (0001) sapphire substrate were in-situ monitored by surface photo-absorption (SPA) method. Ga-rich and N-rich surfaces can be distinguished by their reflectivities. It is found that the surface stoichiometry changes with the substrate temperature and with the carrier gas. In the nitrogen carrier gas, a N-rich GaN surface is stably formed at temperatures up to about 1000°C under NH3 flow. In contrast, the surface in H2 carrier gas is N-rich below 720°C, but becomes Ga-rich above 850°C. The desorption kinetics indicates that H2 enhances the N desorption.
Interfacial Free Energies and the Creep of Multilayer Thin Films
Authors: Josell D. , Carter W. C.
Published: April 2011

Experiments utilizing the creep properties of multilayer thin films to determine interfacial free energies are presented with essential theory. A new technique utilizing tubular multilayer foils is then described.
Indentation Creep Analysis of Amorphous Nitrogen-Containing Carbon Films
Authors: Tanaka Daisuke , Ohshio Shigeo , Saitoh Hidetoshi
Published: April 2011

An indentation creep analysis has been performed to investigate micro-mechanical properties of amorphous nitrogen-containing carbon films. Using results of the slope of the time-displacement relation of creep procedure, the strain rate sensitivity exponent m is obtained. The m value of 0.004 was obtained for diamond-like carbon film without nitrogen. In contrast, those were found to be in the range between 0.009 and 0.101 for nitrogen-containing carbon films. These slightly increased with increasing the nitrogen content of the films. We present results that indicate that the nano-indentation creep technique enables clarification of the nano-structure of nitrogen-containing carbon films.
Stress-Strain Curves by Tensile Testing of Thin Metallic Films On Thin Polyimide Foils: Al, AlCu, CuNi(Mn)
Authors: Macionczyk F. , Brückner W. , Reiss G.
Published: April 2011

For better understanding the mechanical properties of thin films it is helpful to use the same experimental methods as for bulk material, like tensile tests, thereby being able to directly compare the results. However, tensile tests of free-standing metallic thin films are often difficult to perform for reasons of preparation, handling, and stresses in the films. By leaving the metallic film on an elastic substrate tensile tests were performed in a rather simple and precise manner, using a commercial tensile testing machine. Stress-strain curves were determined by separating the force working on the substrate from that working on the film-substrate compound. Those measurements were done at room temperature for Al, AlCu(0. 5 wt %) and Cuo0.57Ni0.42Mn0.01 thin (200–2000 nm) films prepared by magnetron sputtering on 8 μm and 13 μm thick polyimide (Kapton) foils. The film microstructure was characterized by scanning and transmission electron microscopy and X-ray diffraction. The tensile strength of the fine grained films was found to be up to one order of magnitude higher than for the corresponding coarse grained bulk material. Al and AlCu films showed little, CuNi(Mn) films showed no plastical behavior. Crack formation started between 0.3 % and 2 % strain depending on the material, the thermal history, and the grain size.
In-Situ TEM Observations of Surface Roughening and Defect Formation in Lattice Mismatched Heteroepitaxial Thin Films
Authors: Ozkan Cengiz S. , Nix William D. , Gao Huajian
Published: April 2011

This paper focuses on in-situ transmission electron microscopy observations of surface roughening and defect formation in heteroepitaxial Sil−xGex thin films. Annealing experiments have been carried out in-situ in the microscope under a high vacuum environment. We comment on the sample preparation procedure for in-situ TEM experiments and explain the importance of having a sufficiently thick sample to have the stress state in the film unaltered. Experimental results of in-situ surface roughening are presented for suberitically and supercritically thick Sil−xGex films. We found that, in a vacuum environment, the kinetics of surface roughening and the resulting surface morphology are much different than in a hydrogen environment.
Polycapillary X-Ray Optics for Thin Film Strain and Texture Analysis
Authors: Hofmann F. A. , Gibson W. M. , Lee S. M. , Macdonald C. A. , Ullrich J. B. , GAO N.
Published: April 2011

Polycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate, or focus x-ray beams from conventional, laboratory-based sources. Multifiber polycapillary collimating optics were placed without system optimization into a number of diffractometer systems. Strain and texture measurements were performed. Measurements on thin films with and without the lens yielded gains of 8–100. Gains are higher in comparison with systems employing pinhole rather than one-dimensional slit collimation. The collimation also resulted in peak symmetrization, which simplified peak shape analysis.

Focused beam optics provide even larger gains. Gains of 100 have been demonstrated using polycapillary optics with spot sizes as small 20 μm. This is of particular significance for providing spatial resolution for low signal applications such as thin films. The inverse dependence of the critical angle for total external reflection on photon energy also results in suppression of high energy photons. This suppression of Bremsstrahlung can allow use of higher tube potentials to increase characteristic line emission. Background suppression from a polycapillary optic ″soller slit″ is also enhanced due to the two dimensional collimation and much smaller acceptance angle of the polycapillary optics. Polycapillary optic alignment is also faster and more convenient than the usual parafocusing geometry. The combination of background suppression, intensity gain and increased tube emission by employing polycapillary optics greatly increases the signal to noise ratio for thin film stress analysis.
Effects of Interface Nonplanarity on the Interface Fracture Energy of the TiN/SiO2System
Authors: Lane Michael , Ni Winnie , Dauskardt Reiner , Ma Qing , Fujimoto Harry , Krishna Nety
Published: April 2011

Fracture mechanics models indicate that nonplanarity of the interface should have a significant effect on the measured fracture energy [1–5]. Previous work on a typical interconnect structure (Fig 1) has demonstrated that two thin film systems with nominally the same composition, but processed under different conditions exhibited different SiO2/TiN interface fracture energies [6,7]. pon investigation via crosssectional TEM, it was found that the stronger interface was significantly rougher than the weaker interface. These results indicate that small changes in processing conditions can significantly effect both interface morphology and adhesion. Accordingly, in this study, samples differing in the flow rate of Ar to a plasma arc during deposition of a TIN layer were chosen in order to investigate the effects on the interface morphology and the resulting interface fracture energy.
Tem Study of Yielding in Polycrystalline Gold Thin Films
Authors: Owusu-Boahen Kwame , King Alexander H.
Published: April 2011

We have used transmission electron microscopy (TEM) to study the microstructure of thin gold films which were grown on 〈100〉 rock salt. The samples were annealed on the rock salt substrate or on a gold TEM specimen grid. Films annealed on rock salt had a larger mean grain size than those annealed on TEM grids. All of the annealed films have a 〈111〉 preferred orientation. Several cracks are observed in the film annealed on rock salt. Plastic yielding of the film was identified by the presence of dislocations, and is caused by tensile stress derived from grain growth. In spite of the uniform texture of the films, the observed dislocations were concentrated only in some individual grains, while their surrounding grains remained dislocation-free. Yielded grains showed no difference of orientation that would lead to higher Schmid factors, so other predictors of yielding must be considered.
Surface Stress Effects On The Critical Thickness Of Thin Film Superlattices
Authors: Cammarata R. C. , Sieradzki K.
Published: April 2011

Surface stress represents the reversible work per unit area to elastically stretch a solid surface, and can be associated with interfaces between two solid phases as well as free solid surfaces. The effects of surface stresses on the critical thickness for epitaxy in thin film superlattices is given.
Determination of the Mechanical Properties of Polysilicon Thin Films Using Bulge Testing
Authors: Jayaraman S. , Edwards R. L. , Hemker K. J.
Published: April 2011

Using standard deposition and micromachining techniques, silicon substrates with square and rectangular windows covered with membranes of polycrystalline silicon (polysilicon) have been fabricated. Pressure-displacement curves obtained during the bulge testing of membranes with the above geometries have been used to determine the elastic constants E and v of the polysilicon. The results obtained (E = 162± 4 GPa and v = 0.19±0.03) are in good agreement with literature values for bulk polycrystalline silicon.
The Effects of Residual Stress on Modulus Measurements by Indentation
Authors: Bahr D. F. , Crowson D. A. , Robach J. S. , Gerberich W. W.
Published: April 2011

Continuous indentation has been used to evaluate the mechanical response of chromium and platinum films deposited on silicon and glass substrates. The traditional method of analysis of indentation data to determine modulus and hardness is sensitive to residual stress in the film, thereby suggesting that modulus measurements may be used to gauge residual stresses. Evaporated metal films, which are under residual tension, tend to show a lower modulus (using standard calculation methods) than the bulk materials. However, a sputtered platinum film exhibits an apparently higher modulus than the bulk material. These data suggest that differences between the calculated and expected modulus using indentation tests cannot be used to unequivocally determine the stress state in a thin film.
Probabilistic Modeling of Gas Transport in a Plugged Repository in Salt Rock
Authors: Höglund L O , Wiborgh M , Arens G.
Published: April 2011

Since 1981 the former rock salt mine Bartensleben near Morsleben (former GDR) ERAM has been in operation as a repository for low and intermediate level radioactive waste. As a result of the reunification and the changed licensing situation a new closure concept for the repository has to be developed. In the course of this work, the optimal design of the plug is currently being evaluated considering also gas escape and exchange of potentially contaminated brine through the plug.
Uraninites of the Oklo Reactors: O Isotopes and Mineralogical Data
Authors: Pourcelot L. , Gauthier-Lafaye F.
Published: April 2011

Natural fission reactors located in the uranium ore deposits of Oklo-Okélobondo and Bangombé (Gabon) are a unique case of natural nuclear waste disposal. The Reactor Zones (RZ) (up to fifteen) cores are made of 60% uranium (UO2) embedded in a clay matrix [1]. The uraninites are depleted in 235U and contain fission products. Therefore, they are considered to be good analogues for spent nuclear fuel matrix [2]. The aim of this work is to study the conditions of preservation over a long periode of time of the uraninites which have been sumitted to interraction with fluid having different oxidizing potential. For this purposes mineralogical (X-ray powder diffraction), chemical (electron microprobe) and oxygen isotopic analyses were performed on uraninites from various RZs.
A Regulatory Authority's Needs for R&D to Develop Competence in Assessing Nuclear Waste Management Safety
Authors: Norrby Sören
Published: April 2011

A regulatory authority in the field of nuclear waste management will not be responsible for the waste management itself. The regulator will however be responsible for reviewing the safety of the waste management activities proposed and performed by nuclear power plant owners or special organisations set up to manage and dispose of nuclear waste. In this paper the regulator's need for R&D to develop competence in the assessment of nuclear waste management safety is discussed.
Source Trends for Performance Assessment of HLW Glass and Spent Fuel as Waste Forms
Authors: Grambow B.
Published: April 2011

with respect to the state of validation for source term development. Consequences of the various mechanism on mass half lives of the waste forms are calculated with analytical equations. For glass the largest uncertainty stems from the yet unclear dissolution mechanism under silica saturated conditions. Source terms based on silica solubility coupled to Si-mass transfer are probably neither conservative nor realistic. For spent fuel the largest uncertainty is in the extrapolation of radiolytic fuel oxidation for long periods of time. Considering the uncertainties involved, reaction rates cannot yet be extrapolated reliably to values much lower than the lowest reliable experimental measurements.
Chemical Durability of Aluminosilicate Glasses Containing Low Solubility Chemical Elements
Authors: Leturcq G. , Berger G. , Advocat T. , Fillet C. , Halgand C. , Vernaz E.
Published: April 2011

The chemical durability of aluminosilicate glasses was investigated experimentally between 90 and 200°C. In order to evaluate their potential for containment of minor actinides, these glasses were doped with Nd (to simulate the presence of trivalent actinides) or U. The proportions of the glass network formers, Si and Al, were near those found in basaltic glasses (tholeitic end members). The differences between the chemical compositions allow the clarification of the influence of glass network modifier elements on the chemical durability of silica glasses. More precisely, we tested the ability of Ti, Zr, Nd and N to potentially improve the chemical durability.

Two types of leach tests were conducted:

Dynamic leach tests to determine the initial dissolution rates at 90, 150 and 200°C and the activation energy (Ea) of the glass dissolution reaction;

Static leach tests at high SA/V (200 cm−1) and 90°C to determine the long-term alteration rates and the apparent silica solubility.

For all the glass compositions tested, the initial dissolution rates at nearly neutral or weakly basic pH are similar at the same temperature. Consequently all aluminosilicate glasses have the same activation energy, 60 kJ/mol. This suggests that the initial hydrolysis mechanism is controlled by the breakdown of Si-O and/or Al—O bonds, whatever the nature of glass network modifier elements.

On the other hand, modifier elements have major effects on the formation of protective films at the glass surface. The nature of this protective film depends on the chemical composition of the glass. A phenomenon similar to metal passivation, has been observed on a glass highly enriched with Nd (53.8 oxide wt%) which may lead to alteration rates in undersaturated media up to two orders of magnitude lower than those observed for basaltic glasses. This “passivation” effect disappears when a sodium sulfate solution (a Nd complexing agent) is used as a leachant. Nitrogen does not improve the chemical durability of aluminosilicate glasses. Finally, all these glasses have the same low dissolution rate (10−4 g/m2/day) under saturated conditions.
Chemical Composition, Geochemical Alteration, and Radiation Damage Effects in Natural Perovskite
Authors: Lumpkin Gregory R. , Colella Michael , Smith Katherine L. , Mitchell Roger H. , Larsen Alf Olav
Published: April 2011

Preliminary analytical and transmission electron microscopy (AEM and TEM) results for a small suite of natural perovskites are reported in this paper and discussed in relation to previous work. We show that perovskite compositions in Synroc and tailored ceramics plot within the known fields of natural perovskite compositions. AEM analyses and electron diffraction work on selected samples indicate that they are predominantly stoichiometric variants of the cubic perovskite structure. Geochemical alteration was observed in one sample of loparite from Bratthagen, Norway. The primary result of this alteration was leaching of Na from the A-site. Although sufficient alpha-decay dose levels for complete amorphization are not realized in this suite of samples, the available data bracket the beginning of the crystalline-amorphous transformation at doses that are ∼ 2-4 times greater than those of zirconolite of similar age. These results may be due to fundamental differences in the damage annealing rates of perovskite and zirconolite.
Apatitic Waste Forms: Process Overview
Authors: Carpena J. , Audubert F. , Bernache D. , Boyer L. , Donazzon B. , Lacout J.L. , Senamaud N.
Published: April 2011

Our study is concerned with the different apatitic waste forms which can be produced with processes ranging from high-temperatures to ambient temperature synthesis. The different processes developped allow to take into account the nature of the waste and the application targeted, from specific conditioning of separated wastes, encapsulating of mixed wastes, solid or liquid wastes, to filling materials for direct storage of spent fuel, interim storage, surface storage or deep repository.
Nd-Doped Zirconolite Ceramic and Glass Ceramic Synthesized by Melting and Controlled Cooling
Authors: Advocat T. , Fillet C. , Marillet J. , Leturco G. , Boubals J.M. , Bonnetier A.
Published: April 2011

Neodymium-doped zirconolite materials may be synthesized by two melting processes. One involves devitrification of an aluminosilicate parent glass containing titanium, zirconium and neodymium oxides, yielding a glass ceramic comprised of submicron zirconolite needles embedded in a silica-rich glass matrix. The second method consists of melting an oxide mixture with the stoichiometry of a highly Nd-enriched zirconolite, then quickly cooling the melt to produce a ceramic rich in zirconolite crystals several hundred microns long containing a large fraction of the initial neodymium.
An Integrated Testing Program for a Near-Field Radionuclide Migration Code
Authors: Binks P. , Fairhurst A. , Howarth D. , Humphreys P. N. , Johnstone T. , Jones M. , Kelly E. , Lee A. , Mcgarry R. , Randall M. , Smalley D. , Thomson G. , Trivedi D. P.
Published: April 2011

The DRINK code is a 2D, biogeochemical transport code developed as a research tool to simulate the long term evolution of near surface LLW disposal sites and to generate gaseous and liquid source terms for far field studies. The code was recently upgraded to provide a more generic modelling tool with wider application to radionuclide migration scenarios. During the development of this code, the Generalised Repository Model (GRM), an integrated strategy has been employed to ensure the production of a fully tested, verified and quality assured product. This strategy is based around a code development protocol with three main components: quality assurance and documentation, verification and realism testing. Realism testing includes both peer review and model testing, with the latter including: experimental test cases; natural and anthropogenic analogues; field observations and finally uncertainty and sensitivity analysis. This paper describes the successful application of the protocol to the development and testing of the GRM code with specific emphasis upon verification and realism testing.
Simulation of the Evolution of a Clay Engineered Barrier by Interaction With Granitic Groundwater: Dynamics and Characteristic Time Scales
Authors: Cranga M. , Trotignon L. , Martial C. , Castelier E.
Published: April 2011

The chemical evolution of a clay engineered barrier in a deep repository interacting with various groundwaters is predicted using the TRIO-EF code supported by additional models tested against experimental data. Main results of this work are related to the long term evolution of the porewater and the buffering effect of the clay barrier in the presence of ion exchange sites and calcite, when exposed to representative granitic groundwaters or more acidic or alkaline waters.
Application of a 3D-Geoscience Information System Within the Performance Assessment of the Geological Barrier Above the Morsleben Nuclear Waste Repository
Authors: Ehrminger B. , Schindler M. , Hugi M. , Wollrath J. , Kibel H. , Langkutsch U.
Published: April 2011

The application of a 3-dimensional geoscience information system (GSIS) in the performance assessment of the geological barrier of the nuclear waste disposal site Morsleben is presented. A primary objective is the development of a geometrically consistent three-dimensional model, representing all relevant hydrostratigraphic units in the model area. Following the completion of the structural model, Finite-Element mesh generation techniques are applied to derive a threedimensional spatial discretisation for numerical modelling of the regional groundwater movement.
Conditioning of Ash Residue in the Reaction Wave of Glass-Forming Heterogeneous Composition
Authors: Karlina O.K. , Petrov G.A. , Ojovan M.I. , Varlackova G.A. , Dmitriev S.A.
Published: April 2011

The possibility of furnace free vitrification of ash residue was considered by using heat generation by means of exothermal chemical reactions which occur in the mixture of heat generating materials (heating batch), glass forming batch and ash residue.
Model Calculations of Porosity Reduction Resulting From Cement-Tuff Diffusive Interaction
Authors: Lichtner Peter C. , Pabalan Roberto T. , Steefel Carl I.
Published: April 2011

To determine the potential effects of alkaline plume migration on the near-field environment of the proposed high-level radioactive waste geologic repository at Yucca Mountain, Nevada, calculations are conducted simulating interactions between cement and tuff with pure diffusive transport of solute species. The calculations used the reactive transport submodule GEM of the computer code MULTIFLO [6]. The results suggest that strong alteration of the tuff host rock and of cement in contact with the tuff could result from these interactions. Porosity reduction within the tuff could isolate the matrix from fracture pore water. The model calculations predict calcification of the cement as would be expected. In simulations involving counter-diffusive transport across the cement-tuff contact, calcification is more pronounced in a partially-saturated environment compared to a fully-saturated one.
Criticality in a Repository for Spent Fuel: Lessons From Oklo
Authors: Oversby V. M.
Published: April 2011

The conditions that are needed to achieve criticality in a high level waste repository for spent nuclear reactor fuel are reviewed. The effect of initial enrichment of the fuel, burnup, and of mixed oxide fuels on the conditions for criticality are discussed. The situations that produced criticality at Oklo, Gabon, 2000 million years ago are summarized. A model based on the Oklo conditions is presented for estimating the amount of fissile material that must be assembled to create a critical mass in typical granitic rocks. Mechanisms for movement of uranium and plutonium to achieve a critical configuration are discussed and compared to the conditions that are likely to occur in a repository in granite. The sequences of events needed to produce a critical assemblage are shown to be in conflict with the conditions expected in the repository and, in some cases, to require internally inconsistent assumptions to produce the postulated sequence of events. No credible scenario for achieving criticality in a high level waste repository has been found.