bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real Time Observation of Material Deformation Processes by Synchrotron White Beam X-ray Topography
Authors: Zhao Z. B. , Hershberger J. , Rek Z. U. , Bilello J. C. 
Published: April 2011

ABSTRACTAn experimental apparatus which exploits synchrotron white beam X-ray diffraction topography has been developed to perform real time in situ observation of deformation processes of single crystals. The apparatus consists of a fully automated and remotely controlled mini-tensile device and a CCD based X-ray imaging detector with associated video system. Both tensile data and X-ray topographic images are recorded simultaneously. The materials under study include single crystals of Si, and single crystals or bicrystals of the refractory metals W and Mo. The deformation processes of these crystals have been studied by monitoring a selected transmission Laue spot while the specimen is mechanically cycled by loading and unloading. The X-ray images have been captured by a frame grabber and recorded via a VCR. Several phenomena have been observed, including bending contours, strain concentrations, reversible anelastic effect and microyielding. The observed stress relaxations are correlated to microstructural variations shown by X-ray topography. The stability of low angle grain boundaries in bicrystals; and the effect of high strength and toughness coatings on the deformation of single crystal substrates was investigated.
In Situ and Ex Situ Ellipsometric Characterization of Oxygen Plasma and UV Radiation Effects on Spacecraft Materials
Authors: Bungay C. L. , Tiwald T. E. , DeVries M. J. , Dworak B. J. , Woollam John A. 
Published: April 2011

ABSTRACTAtomic Oxygen (AO) and ultraviolet (UV) radiation contribute (including synergistically) to degradation of spacecraft materials in Low Earth Orbit (LEO). NASA is, therefore, interested in determining what effects the harsh LEO environment has on materials exposed to it, as well as develop materials that are more AO and UV resistant. The present work involves the study of AO and UV effects on polyarylene ether benzimidazole (PAEBI) with in situ and ex situ spectroscopic ellipsometry. PAEBI is a polymer proposed for space applications due to its reported ability to form a protective phosphorous oxide on the surface when exposed to AO. In our experiments PAEBI was exposed to UV radiation from a xenon lamp while in situ ellipsometry data were acquired. The effects of UV radiation were modeled as an exponentially graded layer on the surface of bulk PAEBI. The change in UV absorption spectra, depth profile of the index of refraction, and growth trends of the UV irradiated PAEBI were all studied in these experiments. In addition, PAEBI was exposed to an oxygen plasma to simulate the synergistic effects of AO and UV. Ellipsometry data were acquired in-line with both a UV-Visible ellipsometer and an infrared ellipsometer. The change in UV absorption bands and index of refraction due to synergistic AO/UV, as well as the growth trends of the oxide layer were studied.
Spectral-Component Monitoring of the Plumes Generated during the Deposition of RE(Y, Nd) Ba2Cu3O7−x Films by Pulsed Laser Ablation
Authors: Biggers R. , Varanasi C. , Maartense I. , Dempsey D. , Mastc D. , Liptak D. , Jones J. , Peterson T. L. , Murray T. , Busbee J. 
Published: April 2011

ABSTRACTYba2Cu3OT7−x (Y123) and NdBa2Cu3O7−x (Nd123) thin films were deposited by PLD using a 248 nm wavelength KrF excimer laser. The emission spectra PLD process control techniques developed to grow reproducibly high quality Y123 thin films were also applied to the Nd123 depositions. The time-resolved spectral components of plumes generated from Y123 and Nd123 targets at the same deposition conditions were compared. When the two targets were mounted at the same distance from the substrate heater, the spectral emissions at 327 ± 5 nm (Cu*) were essentially identical for similar laser pulse energies and other deposition conditions (150 mTorr oxygen pressure, 760°C substrate heater temperatures, etc.). High quality Nd 123 films (Tc ˜93 K, Jc > 2x 106 A/cm2) are considerably more difficult to produce than those of Y123. Deposition conditions associated with PLD of high quality Y123 films produce very poor Nd 123 films. This observation is consistent with the belief that the nucleation and growth of Nd 123 are significantly different than that of Y 123.
Atomic-scale Analysis of Laser MBE Growth of Oxide Thin Films by in situ Rheed and Caiciss
Authors: Yoshimoto M. , Ohnishi T. , Lee G-H. , Sasaki K. , Maruta H. , Koinuma H. 
Published: April 2011

ABSTRACTAtomic-scale growth analysis of oxide thin films was performed by in situ reflection high energy electron diffraction (RHEED) and coaxial impact collision ion scattering spectroscopy (CAICISS) combined with Laser MBE. On single crystal substrates with atomically flat terrace and step structures, the two-dimensional nucleation followed by molecular layer-by-layer growth was verified by in situ monitoring of RHEED intensity oscillations, as well as ex situ atomic force microscopy (AFM) observation, for the growth of BaTiO3, Al2O3 and BaO thin films. The epitaxial BaTiO3 films grown on SrTiO3(100) and c-axis oriented Bi2Sr2CaCu2Ox (Bi2212) superconducting films were subjected to in situ CAICISS measurements in order to examine the topmost surface structure. The key factors to develop oxide lattice engineering are discussed with respect to not only in situ monitoring of the growth process using RHEED but also the atomic regulation of the substrate surface by AFM and ion scattering spectroscopy. The present work also demonstrates the advanced oxide thin film processing based on the laser MBE to control the growth and surface of films on an atomic scale.
Rheed Monitoring of Rotating Samples During Largearea Homogeneous Deposition of Oxides
Authors: Matijasevic V. C. , Lu Z. , Dessonneck K. Von , Taylor C. , Barlett D. 
Published: April 2011

ABSTRACTWe have successfully implemented RHEED monitoring of growth of complex oxides in a reactive evaporation process with substrate rotation and an oxygen environment. A rotating substrate heater is used with a partial enclosure kept at a 10 mTorr oxygen pressure. This heater allows for simultaneous and uniform deposition of multiple 2-inch wafers. The RHEED beam diffracts from samples as they pass through the high-vacuum zone of the heater. A CCD camera is used for RHEED data acquisition and image capture is synchronized to sample position. In order to achieve good quality diffracted images, rotation of the sample is required to be less than 1 degree for the duration of data capture. With our relatively inexpensive setup images can be acquired for sample rotation speeds up to 1500 RPM. We use this RHEED diagnostic system for study of in-situ growth of high-temperature superconducting thin films.
In Situ Monitoring of Anodic Oxide Growth on SI (001) by Interface Second-Harmonic Generation
Authors: Janz S. , Bardwell J. A. 
Published: April 2011

ABSTRACTOptical second-harmonic (SH) generation is used to monitor the anodic growth of oxide on a (001) Si surface. The measured SH intensity is dominated by the nonlinear optical response of the space charge region in the Si just below the Si/oxide interface. The interface SH technique can detect the onset of H desorption, identify the flat band potential, and probe the evolution of space charge within the growing oxide layer.
Infrared Emission Spectra of Indium Phosphide at Elevated Temperatures
Authors: Rogne H. , Timans P. J. , Ahmed H. 
Published: April 2011

ABSTRACTProcess monitoring and control during semiconductor device fabrication frequently relies on good knowledge of the optical properties of the substrate wafer and the surface coatings. However, these optical data are often unavailable, and as a consequence errors arise in pyrometric temperature measurements, as well as in thermal modelling of heating cycles. In this study, isothermal electron beam heating has been combined with in situ optical measurements to record thermal emission spectra of undoped InP specimens from 347 to 478°C, at wavelengths between I and 9 μm. The absorption coefficient was deduced from the emission spectra and reveals information about the temperature dependence of the infrared absorption mechanisms in InP.
Fem Simulation of Micro-Rotating-Structures and Their Applications in Measurement of Residual Stresses in Thin Films
Authors: Zhang Xin , Zhang Tong-Yi , Zohar Yitshak 
Published: April 2011

ABSTRACTFEM simulation of micro-rotating-structures was performed for local measurement of residual stresses in thin films. A sensitivity factor is introduced, studied and tabulated from the simulation results. The residual stress can be evaluated from the rotating deflection, the lengths of rotating and fixed beams, and the sensitivity factor. The micro-structure technique was applied to measure residual stresses in both silicon nitride and polysilicon thin films, before and after rapid thermal annealing (RTA), and further confirmed by wafer curvature method. Residual stresses in polysilicon films at different RTA stages were also characterized by micro-Raman spectroscopy (MRS). The experimental results indicate that micro-rotating-structures indeed have the ability to measure spatially and locally residual stresses in MEMS thin films with appropriate sensitivities.
Nanoindentation and Nanowear Studies of Thin Carbon Coatings
Authors: Kulkarni Ashok V. , Wyrobek Jerzy T. , Qiant Zhenghong , Siverstent John M. , Judyt Jack 
Published: April 2011

ABSTRACTThin film magnetic disks and head-sliders require protective overcoats, usually some form of carbon, to guard the magnetic elements against corrosion and wear and to provide long interface durability. The mechanical properties of these coatings are important for assessing their tribological performance. In this paper we present the results of nanomechanical properties of amorphous carbon (a-C) and nitrogenated carbon (CN) films deposited on Si(100). a-C and CN films were deposited on silicon by Facing Target Sputtering (FTS) technique. The elemental composition and bond characterization of a-C and CN films have been determined by X-ray Photoelectron spectroscopy (XPS). Nanoindentation experiments were performed using Hysitron Triboscope® in the load range of 10–200 μN, using a sharp 90° 3-sided pyramidal diamond tip ( 50 ± 10 nm radius). Hardness and Young's modulus of elasticity were determined from the load-displacement data. Nanowear studies were performed on the 10 and 20 nm a-C and CN films to determine the critical load. Below the critical load no significant wear is observed. Above the critical load however, the wear increases sharply. Abrasive wear seems to be the cause of the sharp increase in wear depth in case of a-C film. From the above observation, CN films exhibit excellent mechanical properties owing to its superior hardness property.
Advanced Bulge Test System
Authors: Keiner H. , Preissig F. J. von , Zeng H. , Nejhad M. N. G. , Kim E. S. 
Published: April 2011

ABSTRACTThe bulge test is an established method of measuring the residual stress and elastic stiffness of thin-film materials. We present an advanced experimental bulge-testing system that provides advantages in speed, accuracy, and flexibility. Key innovations include the use of a Laser Doppler Displacement Meter to measure deflection, an actuated air-cylinder mechanism to vary pressure, and sophisticated computer handling of data acquisition and analysis. A test case demonstrates that repeatability of results is extremely good.
Optimization of Blend Toughness by Simultaneous Measurement of Heat and Work of Deformation
Authors: Agarwal N. , Farris R. J. 
Published: April 2011

ABSTRACTThe technique of differential gas pressure calorimtery is used to simultaneously measure heat and work of isothermal deformation of acrylic based latex blend coatings. These coatings comprise of phase separated hard and soft components resulting in a combination of stiffness and toughness. An overall energy balance approach is adopted to study the partition of energy between the two phases in their respective energy-dissipating and energy-absorbing mechanisms. The toughness is maximized by a simultaneous maximization of heat dissipation and energy absorption; a fact often overlooked in the design of commercial rubber toughened systems that focus almost entirely on increasing the energy absorbing capacity of the glassy matrix. It is observed that maximizing both the energy absorption as well as dissipation can result in much higher toughness without a large sacrifice in stiffness.
Mechanical Properties Of Ferro-Electric Composite Thin Films
Authors: Fountzoulas C. G. , Sengupta S. 
Published: April 2011

ABSTRACTFerro-electric (BSTO) films of 1 μm nominal thickness were deposited on single crystals of sapphire at substrate temperatures varying from 30 °C to 700 °C. Optical analysis showed that the thin films were amorphous up to 500 °C, while at 700 °C they were polycrystalline. The microstructure of the thin films was columnar at all substrate temperatures. The film microhardness increased with increasing substrate temperature. While the cohesion failure load of the films remained fairly constant, the adhesion failure load increased with increasing substrate temperature.
Picosecond Ultrasonics Studies of the Effect of Ion Implantation on InterfAcial Bonding Between a thin Film and a Substrate
Authors: Tas G. , Loomis J. J. , Maris H. J. , Bailes A. A. , Seiberling L. E. 
Published: April 2011

ABSTRACTWe have used picosecond ultrasonics to study the effects of ion irradiation on the interfacial bonding between gold films and a silicon substrate. Acoustic vibrations are excited in the metal film when a picosecond light pulse is absorbed. The rate at which these vibrations damp out via sound transmission across the interface into the substrate gives a measure of the adhesion of the film to the substrate. The films were irradiated with 2.5 MeV helium ions with doses between 7×1014 and 8×1016 ions cm-2. The adhesion, as measured by the rate of acoustic damping, was found to be significantly improved by the ion irradiation.
Two-Dimensional Distribution of the Residual Stress in MBE-Grown InGaAs/GaAs Strained Layer Superlattices
Authors: lizuka K. , Watanabe H. , Komatsu M. , Suzuki T. 
Published: April 2011

ABSTRACTDistribution of the residual stress in InGaAs/GaAs strained layer superlattices (SLSs) has been investigated by the micro-focus photoluminescence (PL) method and PL topography. Dark lines parallel or perpendicular to [011] direction were observed in the samples by PL topography. The density of dark lines was decreased as the thickness of In0.1Ga0.9As layers increased. Such dark lines were observed even in a sample whose thickness was thinner than critical value. These dark areas corresponded to the regions where the peak wavelength of PL spectrum was shifted to longer side because of tensile stress. These results were explained well by our proposed model. That is, tensile stress acts the top of mountainous regions of wrinkles which were formed by compressive stress caused by the difference of the lattice constant between InGaAs and GaAs.
Stress Controlled Magneto-Mechanical Instability In Terfenol-D Thin Films
Authors: Su Quanmin , Wen Y. , Wuttig Manfred 
Published: April 2011

ABSTRACTThe magneto-mechanical properties of Terfenol-D thin films deposited on Si substrates were studied by magnetic and mechanical measurements of film/substrate composite cantilevers. The AE effect and mechanical damping of the film were measured simultaneously. The stress in the film was controlled by annealing and deposition at different temperatures as well by the selection of the substrate material below the recrystallization temperature and determined to vary from -500 MPa, compression, in as deposited films to +480MPa, tension, in annealed films. This paper highlights the magneto-mechanical response of tensioned 1 m nanocrystalline Terfenol-D films on 50 Pim Si substrates display a pronounced damping maximum at a magnetic field of about 1.5kOe oriented perpendicular to the plane of the film. The phenomenon is critically dependent on the orientation of the magnetic field and is the result of a magneto-mechanical instability in the Terfenol film.
Energy Storage And Recovery In Thin Metal Films On Substrates
Authors: Baker Shefford P , Keller Rose-Marie , Arzt Eduard 
Published: April 2011

ABSTRACTDislocation segments which extend through the thickness of a film can move through the film only if dislocation line length is deposited or removed at the film/substrate and film/passivation (if any) interfaces. The dislocation density and, therefore, the energy stored in the film increase during plastic deformation. The reverse process, that is, the reduction of strain energy in the film by the reduction of dislocation line length, is here suggested to be the origin of a number of unexplained features of experimentally obtained stress-temperature curves, including very low (or even “negative”) yield stresses in compression, tensile-compressive flow stress asymmetries, increasing strength with increasing temperature upon heating, and a very strong Bauschinger-like effect which has been seen in thin Cu films. The results of stress-temperature measurements of passivated Cu thin films on silicon substrates are presented.
Microstructural Effects on the Hardness, Elastic Modulus and Fracture Toughness of CVD Diamond
Authors: Kant A. , Drory M. D. , Moody N. R. , MoberlyChan W. J. , Ager J. W. , Ritchie R. O. 
Published: April 2011

ABSTRACTThe hardness, elastic modulus, and fracture toughness of chemical vapor deposited (CVD) polycrystalline diamond have been investigated on several thick (∼100 μm) free-standing films with regard to the grain size, impurity content and failure mechanisms. Micro-hardness measurements using Vickers indentation, in conjunction with Young's modulus measurement techniques such as nano-indentation, were employed to estimate the indentation fracture toughness. The toughness of CVD diamond was increased through the addition of non-diamond carbon, which promoted intergranular fracture and enhanced the toughness by grain bridging.
Nanoindentation of Atomically Modified Surfaces
Authors: Corcoran Sean G. , Brankovic Stanko R. , Dimitrov Nikolay , Sieradzki Karl 
Published: April 2011

ABSTRACTNanoindentation studies on metal and semiconducting surfaces often display excursions in the load-displacement curves. These displacement excursions have been attributed to phase transitions, oxide breakthrough, surface contamination effects, and dislocation nucleation under the indenter tip. We have shown recently that displacement excursions were present for nanoindentation on single crystal Au (111), (110) and (100), and were attributed to dislocation nucleation since all other phenomena were ruled out. We present our recent results that have been aimed at understanding the effects of surface modification at the nanoscale on dislocation nucleation. The effects of modifying the Au surface with electrochemically deposited metal monolayers (Pb and Ag), with an electrochemically deposited oxide monolayer and an electrochemically reconstructed surface will be presented. Hardness differences as great as a factor of 3 have been observed for these surfaces. These experiments are unique in that they were carried out under electrochemical control where strict control of the surface cleanliness can be maintained.
Further Developments of the Reductive Capacity Model for Spent Fuel Stability: Application to Minor Radionuclides
Authors: Bruno J. , Cera E. , Duro L. , Spahiu K. , Eriksen T. , Eklund U-B. , Werme L.O. 
Published: April 2011

ABSTRACTA reductive capacity (RDC) kinetic model previously developed for the radiolitically induced oxidative dissolution of the spent fuel matrix has been applied to critical minor radionuclides present in spent fuel [1]. The model has been tested in front of experimental results from spent fuel corrosion obtained within the SKB programme. The experimental procedure is detailed in a previous publication [2]. The RDC model considers
Predicting the Performance of a Site Closure System Through Engineering Risk Assessment
Authors: Garrard G. F. G. , Lany P. Von , Powrie W. , Humphreys P. N. , Pinner A. V. 
Published: April 2011

ABSTRACTSince 1959 British Nuclear Fuels pie (BNFL) have operated a disposal site for solid low level radioactive wastes (LLW) at Drigg, approximately 6 kilometres south of Sellafield in West Cumbria. Prior to 1988 the disposal method involved the excavation of a series of parallel trenches across the site which were back filled with LLW and covered with an interim, water resistant cap. Since 1988 the disposal method has changed and waste is now compacted and placed into steel isofreight containers into which a highly fluid cement based grout is added prior to the containers being disposed of in a series of open concrete lined vaults. It is proposed that, when full, each vault will also be capped. The change in disposal method has extended the life of the site and final closure is therefore not anticipated until about the middle of the next century.
Crystal Chemistry of Natural Zirconolite: Implications for High-Level Waste Incorporation in Synroc
Authors: Gierpé Reto , Williams C. Terry , Lumpkin Gregory R. 
Published: April 2011

ABSTRACTZirconolite, ideally CaZrTi2O7, is a relatively rare mineral crystallizing at different geological conditions and in a wide range of generally SiO2-poor rock types. Synthetic zirconolite is one of two major actinide (ACT) host phases in SYNROC, a very promising option for the disposal of high-level nuclear waste (HLW). The available samples of naturally occurring zirconolite cover an extensive range in ACT content, age and host rock type, and thus offer an ideal opportunity to study the relationships between alpha-decay doses, radiation damage, and geochemical alteration processes [1]. In this paper, we present results obtained from a statistical study of nearly 300 chemical analyses of natural zirconolite [2].
Volkonskoite From a Natural Analogue of a Cementitious Repository
Authors: Khoury H.N. 
Published: April 2011

ABSTRACTMany repository designs-particularly those for low- and intermediate-level waste-involve use of very large quantities of cementitious materials. The interaction of such materials with groundwater results in a hyperalkaline leachate which will contain any radionuclides dissolved from the waste. The interaction of such leachate with surrounding rocks and the mobility of radionuclides in this complex system has to be considered in repository safety assessment. The very slow kinetics of many of the reactions involved, however, greatly limit the applicability of conventional laboratory studies.The marbles travertines of Maqarin-Daba-Siwaqa sites of North and Central Jordan can serve as natural analogues of a cementitious repository. A similar hyperalkaline environment is still found in some of these areas, controlled by dissolution of natural portlandite and calcium silica hydroxide (CSH) mineral phases. The high pH groundwaters interact with the surrounding limestones and marls offering a close analogy of the situation likely to occur if a repository were constructed in a sedimentary site. The high pH seepages precipitate travertines as a result of the uptake of atmospheric CO2.The sites offer a good chance to investigate the interactions of the high pH water with rocks containing diagenetic enrichments in safety-relevant trace elements (Zn, Cr, U, Se, Ni, Sn, etc.). For example, the unusual smectite (volkonskoite) and other phases (similar to hydrated cement products) precipitated from the mobile alkaline water may act as sinks for such trace elements. Such studies can be used to qualitatively confirm the expected low mobility of important elements in this system. Coupled with hydrochemical studies, the geochemical models used to support performance assessment can be tested (validated).