bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Structure-Activity Relationships for New Aerospace Fuels
Authors: Trohalaki Steven , Pachter Ruth
Published: June 2019

The design of new materials can be made more efficient if toxicity screening is performed in early rather than in late stages of development, especially for volatile materials such as lubricants, fire retardants, fuels, and fuel additives. In our continuing efforts to develop methods for the prediction of the toxicological response to materials of interest to the U.S. Air Force, we have constructed Quantitative Structure-Activity Relationships (QSARs) for thirteen newly proposed propellant compounds. We employed two previously published in vitro toxicity endpoints in primary cultures of isolated rat hepatocytes, which measured decrease in mitochondrial function and glutathione depletion [1]. Molecular descriptors were obtained using ab initio molecular orbital theory. QSAR models were then derived for each endpoint. Correlation coefficients for 2- and 3-parameter QSARs exceed 0.9, possibly enabling toxicity predictions for similar compounds. Insight into the biophysical mechanism of toxic response can be gained from interpretation of the descriptors comprising the QSARs.
Porous Silicon Electrical Biosensors
Authors: Archer Marie , Christophersen Marc , Fauchet Philippe M.
Published: June 2019

The highly sensitive surface of porous silicon (PSi) and the possibility to measure changes in its electrical properties can be used for electrical biosensor applications. The sensing scenario can be extended from the well-characterized organic solvents and pH sensors to detection of biological processes involving the presence of charged molecules. We have investigated the change in electrical properties (capacitance and conductance) of macroporous silicon layers upon exposure to organic solvents and water. Evaluation of our sensor to detect a biological event was done by addressing DNA hybridization. As opposed to the previous work published in this field, in our devices the electrical contact is made on the crystalline silicon (c-Si) substrate. This allows a complete exposure of the surface to the sensing species and reduces the generation of ionic currents through the porous silicon matrix. We will report results of a complete characterization of our device including response speed, selectivity and sensitivity.
Laser Direct-Metallization of Silicon Carbide without Metal Deposition
Authors: Salama I.A. , Kar A. , Quick N.R.
Published: June 2019

Laser direct-write (LDW) is used forin-situmetallization in single crystal 4H- and 6H-SiC wafers without metal deposition. Nanosecond-pulsed Nd:YAG (λ= 1064 and 532 nm) and excimer (λ = 193, 248 and 351 nm) lasers are utilized to create metal-like conductive phases in both n-type and p-type SiC wafers. Frequency-doubled Nd:YAG irradiation(Ephoton< Eg) induces a carbon rich conductive phase due to thermal decomposition of SiC. However, pulsed excimer laser irradiation (Ephoton> Eg) produces a Si- rich conductive phases due to carbon photo ablation. The Schottky barrier heights (SBH) between the laser-metallized layer and the original n-type SiC (ND= 1018cm-3) is determined to be 0.8 eV and 1.0 eV by the current-voltage and capacitance-voltage measurements at room temperature, respectively. Linear transmission line method pattern is directly fabricated in n-type doped (ND=1018cm-3) SiC substrate by pulsed laser irradiation allowing to extract the specific contact resistance (rc)of the laser fabricated metal-like tracks (rc= 0.04-0.12 Ωcm2).The specific contact resistance is unchanged after annealing up to 3 hrs at 950°C.
High Reflectivity AlGaN/GaN Bragg Mirrors Grown by MOCVD for Microcavities Applications.
Authors: Moret M. , Ruffenach S. , Briot O. , Gil B. , Aulombard R.L.
Published: June 2019

Bragg mirrors are highly interesting structures for a large set of applications including vertical cavity lasers and the upcoming range of devices based on microcavities. Although the nitride semiconductors are performing fairly well in optoelectronic applications, it is not straightforward to realize Bragg mirrors based on this material system, due to the low optical index differences between GaN and AlN. Moreover, the lattice parameter difference between these materials will generate crystal defects, which prevent the stacking of a large number of periods, adding to the difficulty. In this work, we have grown high reflectivity Bragg mirrors, with a band centered in the visible blue range. The structures were first modelled, then grown by low pressure MOCVD, and were optimised using an in-situ reflectivity system.

This in-situ reflectivity measurement was compared to a calculated profile, to enable real-time control of the structures. The samples were characterized by transmission electron microscopy and reflectivity. It was possible to realize samples with 90% reflectivity near 400 nm.
Optical and Electrical Characterization of Annealed Silicon-implanted GaN
Authors: Wang H. T. , Tan L.S. , Chor E. F.
Published: June 2019

In this paper, we investigate the effect of post-implant annealing on the optical and electrical properties of Si-implanted GaN films. Results from several measurement techniques including room temperature photoluminescence (PL), micro-Raman scattering, high resolution X-ray diffraction (HRXRD) and Hall measurement are correlated to study the behavior of damage removal, dopant activation, crystalline quality and residual stress, etc. The Hall measurement demonstrates that reasonable activation percentage is achieved though there is only partial recovery of the PL intensity. Raman scattering shows the decrease of stress within the implanted films after thermal annealing. The carrier concentration increases monotonically with increasing annealing temperature up to 1100°C, which is in agreement with linewidth broadening of near band edge in PL spectrum. Moreover, systematic measurements implies that the implantation induced defects, especially point defects, which could play significant role in either the optical or electrical properties of films, cannot be completely annealed out at 1100°C.
Low-Temperature Operation of Green, Blue and UV InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes
Authors: Cao X. A. , LeBoeuf S. F. , Garrett J. L. , Ebong A. , Rowland L. B. , Arthur S. D.
Published: June 2019

Absract:

Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission energies ranging from 2.3 eV (green) to 3.3 eV (UV) has been studied over a wide temperature range (5-300 K). As the temperature is decreased from 300 K to 150 K, the EL intensity increases in all devices due to reduced nonradiative recombination and improved carrier confinement. However, LED operation at lower temperatures (150-5 K) is a strong function of In ratio in the active layer. For the green LEDs, emission intensity increases monotonically in the whole temperature range, while for the blue and UV LEDs, a remarkable decrease of the light output was observed, accompanied by a large redshift of the peak energy. The discrepancy can be attributed to various amounts of localization states caused by In composition fluctuation in the QW active regions. Based on a rate equation analysis, we find that the densities of the localized states in the green LEDs are more than two orders of magnitude higher than that in the UV LED. The large number of localized states in the green LEDs are crucial to maintain high-efficiency carrier capture at low temperatures.
Stimulated Emission at 258 nm in AlN/AlGaN Quantum Wells Grown on Bulk AlN Substrates
Authors: Gaska R. , Fareed Q. , Tamulaitis G. , Yilmaz I. , Shur M.S. , Chen C. , Yang J. , Kuokstis E. , Khan A. , Rojo J.C. , Schowalter L. J.
Published: June 2019

We report on observation of stimulated emission at 258 nm in AlN/AlGaN multiple quantum wells. The structures were grown over Al-face single crystal bulk AlN substrates. AlN/AlGaN structures with 50% of Al in the well material were grown using low-pressure metalorganic chemical vapour deposition. Characterization by using X-ray, AFM, SEM, and photoluminescence techniques indicated high structural quality of the structures. The stimulated emission was measured using the variable stripe length method under excitation by 4-ns-long pulses of the fifth harmonic of Nd:YAG laser radiation at 213 nm (5.82 eV). The stimulated emission exhibited a characteristic superlinear dependence of emission intensity on the pump intensity as well as an exponential increase of the sample-edge emission intensity with increasing stripe length up to ∼430 μm and the intensity saturation beyond this range. The observation of stimulated emission at 258 nm is very promising for the future development of III-nitride-based deep-UV laser diodes on bulk AlN substrates.
Investigation of Epitaxial GaN Films by Conductive Atomic Force Microscopy
Authors: Dogan S. , Spradlin J. , Xie J. , Pomarico A. A. , Cingolani R. , Huang D. , Dickinson J. , Baski A. A. , Morkoç H. , Molnar R.
Published: June 2019

The current conduction in GaN is very topical and is the topic of a vast amount of research. By simultaneously mapping the topography and the current distribution, conductive atomic force microscopy (C-AFM) has the potential to establish a correlation between topological features and localized current paths. In this study, this technique was applied to image the conduction properties of as-grown and post-growth chemically etched samples GaN epitaxial layers on a microscopic scale. Our results show that prismatic planes have a significantly higher conductivity than the surrounding areas of the sample surface. A large and stable local current was mainly observed from the walls of the etched pits, under forward and reverse bias of the metallized AFM tip/semiconductor junction.
High Remanent Polarization in Laser Ablated SrBi2Nb2O9Thin Films
Authors: Das Rasmi R. , Bhattacharya P. , Pérez W. , Katiyarxya Ram S.
Published: June 2019

Pulsed-laser-deposition technique was used to grow SrBi2Nb2O9(SBN) thin films on platinized silicon substrates. The effect of annealing temperature and film thicknesses on the structural and electrical properties has been studied. The average grain size and rms surface roughness was found to increase with increasing annealing temperature. The degree of orientation along the (200) direction was increased with the film thicknesses. The remanent polarization was found to be increased with the film thicknesses and was attributed to the selftexturing characteristics of SBN films. Thin films with higher thickness (∼570 nm) exhibited high value of remanent polarization (∼38 ν/cm2) with coercive field of 185 kV/cm. There was a reduction of coercive field with the film thickness. The dielectric constant was observed to be independent of the film thickness. The increase in loss tangent with increasing film thicknesses was attributed to the reduction of dielectric breakdown strength of the films. The SBN thin films showed minimal fatigue characteristics and suitable material for memory devices.
Generation and Formation of Gold Nanoparticles with Spatial Control by Two-Photon Femtosecond Laser Interference
Authors: Duan Xuan-Ming , Sun Hong-Bo , Kaneko Koshiro , Kawata Satoshi
Published: June 2019

A simple strategy for generating and distributing metallic nanoparticles in polymer matrix with a spatial control in micrometer/nanometer scale has been proposed and successfully demonstrated by combination of two-photon photoreduction and femtosecond laser interference technique. The simultaneous spatially controlling generation and organization of metallic nanopartciles were controllable by designing interference patterns and varying laser intensity and exposure time. This strategy provides a simple and rapid approach for creating templates with designed spatial distribution of the nanoparticles, which is favorable for current microelectronics technology. This method also can be utilized in developing mass production processes for future nanodevices.
ZrC Thin Films Grown by Pulsed Laser Deposition
Authors: Craciun V. , Craciun D. , Howard J. M. , Singh R. K.
Published: June 2019

ZrC thin films were grown on Si substrates by the pulsed laser deposition (PLD) technique. X- ray photoelectron spectroscopy, x-ray diffraction and reflectivity, variable angle spectroscopic ellipsometry, and four point probe measurements were used to investigate the composition, density, thickness, surface morphology, optical and electrical properties of the grown structures. It has been found that crystalline films could be grown only by using fluences above 6 J/cm2 and substrate temperatures in excess of 500 °C. For a fluence of 10 J/cm2 and a substrate temperature of 700 °C, highly (100)-textured ZrC films exhibiting a cubic structure (a=0.469 nm) and a density of 6.7 g/cm3 were deposited. The use of a low-pressure atmosphere of C2H2 had a beneficial effect on crystallinity and stoichiometry of the films. All films contained high levels of oxygen contamination, especially in the surface region, because of the rather reactive nature of Zr atoms.
Effect of Oxygen Pressure During Zno:Al Coating of Zns:Ag Phosphor on Cathodoluminescent Degradation Lifetime
Authors: Ollinger M. , Craciun V. , Nagore S. , Singh R.K.
Published: June 2019

The reduction in cathodoluminescent (CL) degradation of ZnS:Ag phosphor particles coated with aluminum doped zinc oxide (ZAO) films has been investigated. The films were deposited under various oxygen pressures using the atomic flux coating process. The characteristics of the coated phosphor particles with respect to as-received ones were investigated by x-ray photoelectron spectroscopy, CL degradation and scanning electron microscopy. All coated phosphor particles exhibited less CL degradation than the uncoated particles. The coatings deposited under 1.6×10-4 Torr of oxygen, a pressure much lower than the optimum one required to obtain highly transparent and conductive ZnO:Al films, provided the longest brightness lifetime. This increased phosphors lifetime was attributed to the high reactivity of the oxygen deficient ZAO coatings which acted as a sacrificial layer and trapped reactive species before they can reach the phosphor particles and alter their chemical composition.
Comparison of Uranium Release from Spent Fuel and Unirradiated U02in Salt Brine
Authors: Gray W. J.
Published: June 2019

Spent fuel and unirradiated U02were previously reported [1] to have exhibited a 100-fold difference in the total amount of uranium released during static leach tests in salt brine. Two additional studies designed to investigate that difference have now been completed. The first study involved leach tests with U02pellets that had been doped with plutonium to simulate the alpha activity in spent fuel. The second study consisted of leach tests on spent fuel specimens that originated in the same reactor assembly as those used in previous tests but handled differently following discharge from the reactor. Results from the recently completed tests show that at least 90% of the reported difference between the dissolution behavior of spent fuel and U02can be attributed to an apparent surface oxidation of the spent fuel specimens after their discharge from the reactor. The effect of alpha radiolysis on the leaching of spent fuel and U02in salt brine in the presence of an air atmosphere was found to be relatively small in these tests.
High-Level Waste Package Licensing Considerations for Extrapolating test Data
Authors: Johnson T.C. , Chang K.C. , Jungling T.L. , Person L.S. , Peterson C.H. , Voglewede J.C. , Wick E.A.
Published: June 2019

Programs intended to provide supporting information for the high-level radioactive waste (HLW) repository program must consider the licensing requirements and the technical issues involved with extrapolation of short-term test data to periods of up to 10,000 years. The licensing requirements of the Nuclear Regulatory Commission (NRC), and the issues the NRC staff considers important for the development of predictive methods, are described. Because performance predictions of the geologic repository and particular components of the waste package must largely be based upon inference, a reasonable assurance, on the basis of the record before the Commission, is the general standard that will be required.
Effect of Pore Solution Composition on Cesium Leachability of Cement-Based Waste Forms
Authors: Hoyle Susan Q. , Grutzeck Michael W.
Published: June 2019

The relationship of pore solution composition to observed leach behavior for cesium-doped, cement-based waste form has been demonstrated.

A leaching model is proposed, based on early diffusion and homogenization of the pore solution and leachant followed by re-equilibration of the waste form with the greater pore solution (pore solution plus leachant) over the long term.
Calculation of Near-Field Radioactivity Release Rates from Neutron-Activated Reactor Parts in a Shallow-Land Burial site at Oak Ridge National Laboratory
Authors: Hightower J. R. , Kelmers A. D.
Published: June 2019

The purpose of this work was to estimate the near-field radioactivity release rates associated with the high-activity, low-level radioactive wastes currently emplaced in Solid Waste Storage Area 6 (SWSA-6) at Oak Ridge National Laboratory (ORNL). Examination of the existing records [1] showed that about 84% of the radioactivity emplaced in SWSA-6 could apparently be accounted for by neutron-activated metal parts discharged from the High Flux Isotope Reactor (HFIR); therefore, this analysis was limited to consideration of those HFIR wastes. The radio- nuclide inventory contained in the HFIR wastes was first calculated, and then realistic or conservative assumptions as well as existing data were employed to calculate near-field radionuclide release rates. The dominant uncertainties in the calculations were summarized, and the research which would be needed to reduce these uncertainties was described. A more complete description of this work can be found in reference [2].
Multicomponent Systems Tests on Used Fuel and Fuel Recycle Waste Glass at 200 °C
Authors: Heimann Robert B.
Published: June 2019

Experiments were performed at 200 °C and 8.5 MPa on used fuel and a borosilicate waste glass in contact with clay, container metals, groundwater and granite selected as reference materials in the Canadian Nuclear Fuel Waste Management Program. The experimental design considered five parameters that determine a fractional factorial design 25-1. The parameters varied were: waste form (used fuel or Moly 99“W” glass), cation exchange capacity of the clay (calcium bentonite, 1360 meq/kg or illite, 160 meq/kg), ionic strength of the groundwater (Standard Canadian Shield Saline Solution, SCSSS, 1.4 mol/L or granitic groundwater GGW, 1 × 10−3 mol/L), surface area to volume ratio (SA/V) (120 or 12 m−1), and container material 3Inconel 625 or Ticode 12). The results show that (i) maximum release of 137Cs from used fuel and waste glass occurs in the presence of illite and GGW, (ii) maximum releases of 90Sr and the actinides from used fuel occur in the presence of bentonite and SCSSS, and (iii) maximum release of 90Sr from the waste glass occurs in the presence of illite and GGW.
Development and Evaluation of a Tracer-Injection Hydrothermal Technique for Studies of Waste Package Interactions
Authors: Jones Thomas E. , Coles D.G. , Britton R.C. , Burnell J.R.
Published: June 2019

A tracer-injection system has been developed for use in characterizing reactions of waste package materials under hydrothermal conditions. High-pressure liquid chromatographic instrumentation has been coupled with Dickson-type rocking autoclaves to allow injection of selected components into the hydrothermal fluid while maintaining run temperature and pressure. Hydrothermal experiments conducted using this system included the interactions of depleted uranium oxide and Zircaloy-4 metal alloy discs with trace levels of 99Tc and non-radioactive Cs and I in a simulated groundwater matrix. After waste-package components and simulated waste forms were pre-conditioned in the autoclave systems (usually 4 to 6 weeks), known quantities of tracer-doped fluids were injected into the autoclaves' gold reaction bag at run conditions. Time-sequenced sampling of the hydrothermal fluid provided kinetic data on the reactions of tracers with waste package materials. The injection system facilitates the design of experiments that will better define “steady-state” fluid compositions in hydrothermal reactions. The injection system will also allow for the formation of tracer-bearing solid phases in detectable quantities.
Effects of Aoueous Phase Composition on the Leach Behavior of Nuclear Waste Glasses
Authors: Feng Xiangdong , Barkatt Aaron
Published: June 2019

A systematic matrix of leach tests on a Rest Valley waste glass composition is described. These tests are intended to provide quantitative systematic information on leachant composition effects. and accordingly elucidate the controlling orocesses in hiuh-solute media. e.g. silicate ground water. brine. etc. In order to separate the effects of the nature and concentration of solutes from pH effects. leach tests were first carried out on the glass in de-ionized water under highly interactive conditions (high surface to volume ratio) in a configuration which pre- vented lowering the pH due to the intrusion of CO:. After determination of the resulting pH. the leach behavior of the glass was characterized in a series of high-dilution tests in various leachants buffered at this pH value in order to quantify the effects of leachant composition and concen- trations on the leaching orocess. The high-dilution conditions were used at this stage to ensure that the leachant composition mould not be signifi- cantly affected by accumulation of leached glass components. It was concluded that increased ionic strength appears to depress the leach rates in near-neutral media but enhances the leach rates under moderately basic conditions.
Padiolytically Induced Oxidation Reactions of Actinide Ions in Concentrated Salt Solutions
Authors: Kim J.I. , Lierse Ch. , Büppelmann K. , Magirius S.
Published: June 2019

The autoradiolytic oxidation of Pu(IV) and Am(III) has been investigated in saline solution of different NaCl concentrations, pH and specific α-activities. The high linear energy transfer (LET) property of α-radiation in solution enhances the oxidation of the Cl ion and thus increases the redox potential (Eh) of the NaCI solution system to a value of more than +1000 mV vs. NHE. Radiolytic reaction products are found as being comparable with those from the Cl2 saturated NaCl solution 'and create a metastable system consisting of C12/HCl0/Cl0−/Cl−. The oxidation of Pu(IV) and Am(III) in such solutions is dependent on the NaCl concentration, pH and specific a-activity involved. The quantitative oxidation to Pu(VI) and Am(V) is ob- served in the concentrated NaCl solution at pH > 7 with a moderately high specific activity (> 1 Ci/L).
The Effects Of Gamma Radiation on Groundwater Chemistry and Glass Reaction In a Saturated Tuff Environment
Authors: Ebert William L. , Bates John K. , Gerding Thomas J. , Konynenburg Richard A. Van
Published: June 2019

The Nevada Nuclear Waste Storage Investigations project has completed a series of experiments that provide insight into groundwater chemistry and glass waste form performance in the presence of a gamma radiation field at 90°C. Results from experiments done at 1 × 103 and 0 R/hr are presented and compared to similar experiments done at 2 × 105 and 1 × 104R/hr. The major effect of radiation is to lower the groundwater pH to a value near 6.4. The addition of glass to the system results in slightly more basic final pH, both in the presence and absence of radiation. However, there is essentially no difference in the extent of glass reaction, as measured by elemental release, as a function of dose rate or total dose, for reaction periods up to 278 days.
A Generalized Model for the Radiolysis of Groundwaters: Bicarbonate Chemistry and Influences
Authors: Nicolosi Stephen L.
Published: June 2019

A groundwater radiolysis model has been developed at Battelle-Columbus which is applicable to groundwaters containing bicarbonate species. The model consists of a chemical mechanism which describes interactions between groundwater species and radiolytic species. Due to the chemical kinetics nature of the model, elementary reactions can be added to extend its range of applicability to other groundwaters. This paper describes the chemical kinetics and influences of bicarbonate species in the model.
The Coupling of Chemical and Transport Processes in Near-Field Modelling
Authors: Sharland S.M. , Tasker P.W. , Tweed C.J.
Published: June 2019

Near-field modelling is concerned with the description of the migration, chemical and degradation processes that may occur within an engineered radioactive waste repository and its immediate environs. The object is to gain understanding of such processes in order to predict the long-time evolution of the repository and to assess the degree of containment provided by the proposed engineered construction. The conditions of primary interest to our programme concern the waste contained within a steel canister and buried in a concrete environment within a clay geology. The chemistry of the near-field is controlled in that it is the consequence of the choice of near-field components, but it may be extremely complex. Intrusion of external groundwater and degradation of the chosen materials will lead to variations in the chemistry in both space and time. It is vitally important to understand these changing chemical conditions since they determine the solubility and sorption of any released radionuclides. In this paper, we describe the computer program CHEQMATE (CHemical EQuilibrium with Migration And Transport Equations), which has many applications in modelling various changes in chemistry in the near-field. The program combines an ionic migration code with the geochemical program PHREEQE [1]. The program maintains local chemical equilibrium in the system as the transport processes evolve. The program includes automatic mineral accounting; solid phases are added or removed from the equilibrium as precipitation or dissolution occurs. We illustrate the use of the CHEQMATE program with an example of a coupled chemical and transport problem, particularly relevant to the near-field of a waste repository.
Effects of Ru vacancies and oxygen synthesis pressures on the formation of nanodomain structures in SrRuO3 thin films
Authors: Yoo Y. Z. , Chmaissem O. , Kolesnik S. , Dabrowski B. , Kimball C. W. , McAnelly L. , Haji-Sheikh M. , Genis A. P.
Published: June 2019

SrRuO3 (SRO) thin films were grown on SrTiO3 (100) substrates using the pulsed laser deposition method. The films' growth properties widely changed in response to different working oxygen partial pressures. An island growth mode was dominant for low pressures up to 10 mTorr followed by a step flow growth mode at 60 mTorr and step flow plus 2 D growth at 200 mTorr then reverting back to island growth at 300 mTorr. Significant out-of-plane strains of SRO films were observed for low growth pressures (up to 10 mTorr) but became notably reduced at 60 mTorr and continued to decrease gradually with further pressure increases. Formation of Ru vacancies occurs regardless of the working pressure values and appears to be minimized at 60 mTorr. Highest TC's were obtained in films exhibiting the step flow growth mode. The role of Ru deficiencies in relation to strain, growth mode, and magnetic properties is discussed.
The Effect of Porogen on Physical Properties in MTMS-BTMSE Spin-on Organosilicates
Authors: Kim B.R. , Son J. M. , Kang J.W. , Lee K.Y. , Kang K.K. , Ko M.J. , Gidley D.W.
Published: June 2019

Decreasing the circuit dimensions is driving the need for low-k materials with a lower dielectric constant to reduce RC delay, crosstalk, and power consumption. In case of spin-on organosilicate low-k films, the incorporation of a porogen is regarded as the only foreseeable route to decrease dielectric constant of 2.2 or below by changing a packing density. In this study, MTMS-BTMSE copolymers that had superior mechanical properties than MSSQ were blended with decomposable polymers as pore generators. While adding up to 40 wt % porogen into MTMS:BTMSE=100:50 matrix, optical, electrical, and mechanical properties were measured and the pore structure was also characterized by PALS. The result confirmed that there existed a tradeoff in attaining the low dielectric constant and desirable mechanical strength, and no more pores than necessary to achieve the dielectric objective should be incorporated. When the dielectric constant was fixed to approximately 2.3 by controlling BTMSE and porogen contents simultaneously, the thermo-mechanical properties of the porous films were also investigated for the comparison purpose. Under the same dielectric constant, the increase in BTMSE and porogen contents led to improvement in modulus measured by the nanoindentation technique but deterioration of adhesion strength obtained by the modified edge lift-off test.
O12.6 Fracture and Deformation of Thermal Oxide Films on Si (100) Using a Femtosecond Pulsed Laser
Authors: McDonald Joel P. , Mistry Vanita R. , Ray Katherine E. , Yalisove Steven M.
Published: June 2019

Femtosecond pulsed laser damage of Silicon (100) with thermal oxide thin films was studied in order to further understand the optical and electrical properties of thin films and to evaluate their influence on the damage of the substrate. The damage threshold as a function of film thickness (2 – 1200 nm) was measured. The damage morphology produced by single laser pulses was also investigated. Two primary morphologies were observed, one in which the oxide film is completely removed, and the other in which the film is delaminated and expanded above the surface producing a bubble feature.
Mechanical Characterization of Multilayer Thin Film Stacks Containing Porous Silica Using Nanoindentation and the Finite Element Method
Authors: Li Ke , Mudhivarthi Subrahmanya , Saigal Sunil , Kumar Ashok
Published: June 2019

Novel metal/dielectric material combinations are becoming increasingly important for reducing the resistance-capacitance (RC) interconnection delay within integrated circuits (ICs) as the device dimensions shrink to the sub-micron scale. Copper (Cu) is the material of choice for metal interconnects and SiO2 (with a dielectric constant k = ∼ 3.9) has been used as an interlevel dielectric material in the industry. To meet the demands of the international road map for semiconductors, materials with a significantly lower dielectric constant are needed. In this study, the effects of porosity and layer thicknesses on the mechanical properties of a multilayer thin film (Cu, Ta and SiO2)-substrate (Si) system are examined using nanoindentation and finite element (FE) simulations. A micromechanics model is first developed to predict the stress-strain relation of the porous silica based on the homogenization method for composite materials. An FE model is then generated and validated to perform a parametric study on nanoindentation of the Cu/Ta/SiO2/Si system aiming to predict the mechanical properties of the multilayer film stack.
Observation of Micro-Tensile Behavior of Thin Film TiN and Au using ESPI Technique
Authors: Huh Yong-Hak , Kim Dong-Iel , Hahn Jun-Hee , Kim Gwang-Seok , Kee Chang-Doo , Yeon Soon-Chang , Kim Yong Hyub
Published: June 2019

Micro-tensile properties of hard and soft thin films, TiN and Au, were evaluated by directly measuring tensile strain in film tension using the micro-ESPI(electronic Speckle Pattern Interferometry) technique. Micro-tensile stress-strain curves for these films were obtained and the properties were determined. TiN thin film 1 μm thick and Au films with two different thicknesses (t=0.5 μm and 1 μm) were deposited onto the silicon wafers, respectively, and micro-tensile specimens wide 50, 100 and 200 μm were fabricated using micromachining. In-situ measurement of the micro-tensile strain during tensile loading was carried out using the subsequent strain measurement algorithm and the ESPI system developed in this study. The micro-tensile curves showed that TiN thin film was a linear-elastic material showing no plastic deformation and Au thin film was an elastic-plastic material showing significant plastic flow. Effect of the specimen dimensions on mechanical properties was examined. It was revealed that tensile strengths for both films were slightly increased with increasing specimen width. Furthermore, variations of yielding strengths for the thin film Au with change of the dimension were investigated.
How Stretchable Can We Make Thin Metal Films?
Authors: Tsay Candice , Lacour Stephanie P. , Wagner Sigurd , Li Teng , Suo Zhigang
Published: June 2019

Thin metal films deposited on elastomeric substrates can remain electrically conducting at tensile strains up to ~∼00%. We recently used finite-element simulation to explore the rupture process of a metal film on an elastomer. The simulation predicted the highest stretchability on stiff elastomeric substrates [1]. We now report experiments designed to verify this prediction. A ∼15-μm thick silicone elastomer layer with Young's modulus E ∼ 160 MPa is deposited on a 1mm thick membrane of polydimethylsiloxane (PDMS), a silicone elastomer with E ∼3 MPa. Metal stripes consisting of 25-nm thick gold (Au) film sandwiched between two 5-nm thick chromium (Cr) adhesion layers are fabricated either on top of the stiff layer spun onto the soft membrane substrate, or are encapsulated at the interface between the two elastomers. Encapsulated gold films remain electrically conducting beyond 40% strain. But conductors deposited on top of stiff elastomer lose conduction at strains of 3-8%. These results suggest that, in addition to the stiffness of the elastomeric substrate, the initial microstructure of the metal film plays a role in determining its stretchability.
Development of Mid-IR Lasers for Laser Remote Sensing
Authors: Soibel Alexander , Mansour Kamjou , Spiers Gary , Forouhar Siamak
Published: June 2019

There is a need in NASA for development of mid-infrared (mid-IR) lasers, such as Quantum Cascade (QC) lasers, for in-situ and remote laser spectrometers. Mid-IR, compact, low power consumption laser spectrometers have a great potential for detection and measurements of planetary gases and biological important biomarker molecules such as H2O, H2O2, CH4, and many additional chemical species on Mars and other planets of Solar systems. Other applications of mid-IR QC lasers are in high power remote Laser Reflectance Spectrometer (LRS) instruments for future NASA outer solar system explorations. In LSR instruments, QC lasers will act as the illumination source for conducting active mid-IR reflectance spectroscopy of solidsurfaced objects in the outer Solar System. LRS instruments have the potential to provide an incredible amount of information about the compositions of surfaces in the outer Solar System. In this work, we will discuss our current effort at JPL to develop and improve the mid-IR QC lasers to a level that the laser performance, operational requirements and reliability will be compatible with the instruments demands for space exploration applications.
Reliability of Long Pulsewidth High Power Laser Diode Arrays
Authors: Meadows Byron L. , Amzajerdian Farzin , Barnes Bruce W. , Baker Nathaniel R. , Baggott Rene P. , Singh Upendra N. , Kavaya Michael J.
Published: June 2019

Space-borne laser remote sensing systems typically rely on conductively cooled, diodepumped solid-state lasers as their transmitter source. Since space-borne instruments incur high developmental and launch costs and are inaccessible for maintenance, their reliability is of great importance. Therefore, it is crucial to address the reliability of high power laser pump arrays, which essentially dictate the reliability and lifetime of the laser systems. The most common solid-state lasers used for remote sensing applications are Neodymium-based, 1-micron lasers and Thulium/Holmium based 2-micron lasers. 2-micron lasers require a pump wavelength of around 10 to 20 nm shorter compared with 1-micron lasers, and require pump pulse durations 5 to 10 times longer. This work focuses on the long pulsewidth laser diode arrays (LDAs) operating at a central wavelength of 792 nm used for optically pumping 2-micron solid-state laser materials. Such LDAs are required to operate at relatively high pulse energies with pulse durations on the order of one millisecond. However, such relatively long pulse durations cause the laser diode active region to experience high peak temperatures and drastic thermal cycling. This extreme localized heating and thermal cycling of the active regions are considered the primary contributing factors for both gradual and catastrophic degradation of LDAs, thus limiting their reliability and lifetime. One method for mitigating this damage is to incorporate materials that can improve thermo-mechanical properties by increasing the rate of heat dissipation and reducing internal stresses due to differences in thermal expansion and thus increasing lifetime. This paper explains the need for long pulsewidth operation, how this affects reliability and lifetime and presents some results from characterization and life testing of these devices.
Advanced Composites for LIDAR Applications
Authors: Kowbel Witold , Withers Jim , Woida Rigel
Published: June 2019

The current generation of laser diodes suffers from poor thermal management. Typically, Cu-W is used as a submount material. Although it offers a good CTE match with GaAs, thermal conductivity is very limited (160 W/mK). A new approach to improving the thermal management of laser diodes was developed involving the use of hybrid CC/graphite foam composites.

We also have a novel technology developed for LIDAR optical structures consisting of SiC-SiC composite material which exhibits excellent fracture toughness and homogeneous CTE.
Analysing scenarios for energy emissions reduction in South Africa
Authors: Moodley S , Mabugu RM , Hassan R
Published: June 2019

Global environmental pressure dictates that South Africa reduces its greenhouse gas (GHG) emissions, while national objectives focus on economic development. South Africa is faced with the dilemma of simultaneously alleviating poverty, reducing unemployment, growing the economy and responding to international pressure to reduce GHG emissions. As a result, policies that promote energy emissions reduction without being harmful to economic growth and national developmental priorities are needed. Environmental fiscal reform presents one such option. The impact of this is still unclear for South Africa, and this paper explores this issue. Energy balance data on energy consumption, energy emissions and input-output data for South Africa are used to assess the economic and environmental effects of environmental reform in the energy sector. Despite the high reduction in energy emissions, a tax on coal is not selected as the best alternative given the high negative impact on the economy. A tax on oil results in a low reduction in energy emissions, which limits its use as an environmental policy. The scenario using a petroleum products tax results in small decreases in economic growth but it has low energy emissions reduction, hence, this alternative is not selected as an option. Energy subsidy reform offers the second highest reduction in real energy emissions and a low decrease in economic growth, and this scenario is therefore recognised as the best option for carbon dioxide reduction in South Africa. The electricity tax offers moderate reductions in real energy emissions and a moderate decrease in economic growth, and therefore, it is deduced that the electricity tax option could be another option for carbon dioxide emissions reduction in South Africa.
Reducing the electricity cost of a Three-Pipe Water Pumping System – a case study using software
Authors: Rautenbach W , Krueger D L W , Mathews E H
Published: June 2019

Efficient control is often the most cost-effective option to improve on the running cost of a ThreePipe Water Pumping System. However, the effect of changing the control strategy (i.e. on energy consumption) is usually difficult to predict. A new simulation tool, QUICKcontrol, was used to investigate the energy cost savings potential in a Three-Pipe Water Pumping System. The influence of pump scheduling, dam level set points, control parameters and different combinations thereof were investigated. The simulation models were firstly verified with measurements obtained from the existing system to confirm their accuracy for realistic control retrofit simulations. With the aid of the integrated simulation tool, it was possible to predict savings of R195 000 per year with an average 3.8 MW of load shifted out of peak times. These control strategies can be implemented in the pumping system with a direct payback period of less than 6 months.
Small hydropower in Southern Africa – an overview of five countries in the region
Authors: Klunne Qim Jonker
Published: June 2019

This paper looks at the status of small hydropower in Lesotho, Mozambique, South Africa, Swaziland and Zimbabwe. For each country, an overview will be given of the electricity sector and the role of hydropower, the potential for small hydropower and the expected future of this technology. Small hydropower has played an important role in the history of providing electricity in the region. After a period with limited interest in applications of small hydropower, in all five countries, a range of stakeholders from policy makers to developers are showing a renewed interest in small hydropower. Although different models were followed, all five countries covered in the paper do currently see activities around grid connected small scale hydropower. Particular frameworks that facilitate IPPs and Power Purchase Agreements with the national utility do provide a basis for (local) commercial banks to provide finance. Off-grid hydropower for rural electrification purposes sees activities in the countries with an active (support) role of government in this respect only. Small hydropower, renewable energy technology has large potential across the southern Africa region, both for grid connected and off-grid applications. Historically, small hydropower played an important role in the development of the region. Since the mid-1960s, however, the main emphasis has been on centralised fossil fuel-based electricity generation. Developers and policy makers have only recently begun looking at small hydropower again.
Performance analysis of an air humidifier integrated gas turbine with film air cooling of turbine blade
Authors: Mahapatra Alok K. , Sanjay Sanjay
Published: June 2019

A computational analysis to investigate the effects of compressor pressure ratio, turbine inlet temperature, ambient relative humidity and ambient temperature on the performance parameters of an air cooled gas turbine cycle with evaporative cooling of inlet air has been presented. The blade cooling method selected is film cooling. The analysis indicates that the mass of coolant required for blade cooling is reduced with increase in temperature drop across the humidifier. Both decrease in ambient temperature and ambient relative humidity results in an increase in plant efficiency and plant specific work. The highest efficiency is obtained at a turbine inlet temperature of 1500 K for all range of ambient relative humidity and ambient temperature, beyond which it decreases. The compressor pressure ratio corresponding to the maximum plant specific work, however, varies with both ambient relative humidity and ambient temperature. The increase in specific work due to drop in ambient relative humidity is more pronounced at higher pressure ratios. Similarly, the increase in efficiency due to ambient temperature drop is prominent at higher turbine inlet temperatures. Finally, a design nomograph is presented to select the design parameters corresponding to best efficiency and specific work.
Maternal Knowledge, Attitudes, and Practices Concerning Interpregnancy Interval
Authors: Ahlers-Schmidt Carolyn R. , Woods Nikki Keene , Bradshaw Danielle , Rempel Anna , Engel Matt , Benton Mary
Published: June 2019

Introduction. Few studies have examined maternal intentions andpractices related to interpregnancy interval (IPI). IPI less than 18months has been linked to increased preterm birth and infant mortality.This manuscript reports on a cross-sectional survey of mothersconducted to understand maternal knowledge, attitudes, and practiceof IPI in Sedgwick County, Kansas.

Methods. New and expectant mothers and mothers of neonatalinfant care unit (NICU) graduates (n = 125) were surveyed regardingthe issues surrounding IPI. Front desk staff handed out self-administeredsurveys, which were returned to a nurse upon completion.NICU participants were emailed a link to the survey hosted on SurveyMonkey®.

Results. Fewer than 30% of mothers reported previously receivinginformation about IPI from any source. When asked about risks associatedwith IPI, women frequently (n = 58, 45%) identified increasedrisk for birth outcomes with no known association with short IPI.Findings regarding maternal attitudes surrounding optimal IPI weremixed with many mothers defining ideal IPI as less than 18 months(n = 52, 42%), while broadly reporting they believed that a woman’sbody needs time to heal between pregnancies. Respondents from theNICU sample generally reported shorter optimal IPI values than theother participants. When IPI was estimated from participants’ pastpregnancies, half of IPIs were less than 18 months. Mothers reportedthey favored healthcare providers as a source for IPI education. Faceto-face discussions or printed materials were the preferred modes ofeducation.

Conclusions. Women were aware of the need for spacing betweenpregnancies, however, that knowledge was unassociated with pastbehavior. These findings should be taken into consideration whenformulating future interventions. Kans J Med 2018;11(4):86-90.
Evaluation of Online Consumer Health Information for Idiopathic Scoliosis Identified by a Google Search
Authors: Heady Sarah C. , Weaver Marissa A. , Berg Gina M. , Manlove Emily M. , Thuener Jennifer E. , Burton Douglas C.
Published: June 2019

Introduction. This study sought to assess the quality of online consumerhealth information about idiopathic scoliosis. Previous studiesshowed that quality of online health information varies and oftenlacks adherence to expert recommendations and guidelines. Nevertheless,72% of internet users seek health information online. A 2005analysis of online scoliosis information found that the informationwas limited and of poor quality.

Methods. Two reviewers vetted the top 10 websites resulting from aGoogleTM search for “scoliosis.” Content was organized into categoriesand rated by three physician evaluators using a 1 - 5 scale basedon quality, accuracy, completeness of information, readability, andwillingness to recommend. Additional information, such as numberof ads and Flesch-Kinkaid reading level, also was collected.

Results. The average overall physician score was 47.6 (75 possible).All websites included content that was mostly accurate but varied incompleteness. Physicians unanimously recommended Mayo Clinic,MedicineNet, and Kids Health; none recommended the GoogleTMKnowledge Graph. The Scoliosis Research Society website reachedthe highest overall physician score. Readability ranged from 7th gradeto college level; only that of Kids Health was below 10th grade level.

Conclusions. Most essential information provided by the websiteswas accurate and generally well rated by physicians. Website rankingby physicians was inconsistent with the ranking order by GoogleTM,indicating that health seekers reviewing the top GoogleTM-rankedwebsites may not be viewing the websites rated highest by physicians.Physicians should consider patient literacy in website recommendations,as many have an above average literacy level.Kans J Med 2018;11(4):95-101.