bluuebunny/crossref_metadata_2025 huggingface dataset:
Room Temperature Nitridation and Oxidation of Si, Ge and Mbegrown Sige Using Low Energy Ion Beams (0.1-1 Kev).
Authors: Vancauwenberghe O. , Hellman O. C. , Herbots N. , Olson J. L. , Tan W. J. , Croft W. J.
Published: June 2019

Direct Ion Beam Nitridation (IBN) and Oxidation (IBO) of Si, Ge, and Si0.8Ge0.2 were investigated at room temperature as a function of ion energy. The ion energies were selected between 100 eV and 1 keV to establish the role of energy on phase formation and film properties. Si0.8Ge0.2 films were grown by MBE on Si (100) and transferred in UHV to the ion beam processing chamber. The modification of composition and chemical binding was measured as a function of ion beam exposure by in situ XPS analysis. The samples were nitridized or oxidized using until the N or O 1s signal reached saturation for ion doses between 5×1016 to 1×1017 ions/cm2. Combined characterization by XPS, SEM, ellipsometry and cross-section TEM showed that insulating films of stoichiometric SiO2 and Si-rich Si3N4 were formed during IBO and IBN of Si at all energies used. The formation of Ge dielectric thin films by IBO and IBN was found to be strongly energy dependent and insulating layers could be grown only at the lower energies (E ≤ 200 eV). In contrast to pure Ge, insulating SiGe-oxide and SiGe-nitride were successfully formed on Si0.8Ge0.20.2 at all energies studied.
Atomic Hydrogen Passivation of High Energy Hydrogen Implants
Authors: Srikanth K. , Shenal J. , Ashok S.
Published: June 2019

High-energy hydrogen ion (proton) implantation is used in Si for creating defects, while low-energy H is known for passivation of a variety of defects and impurities. We have carried out a study of low-energy (<0.4 keV) H passivation of defects produced by 100 keV H implantation. Both Schottky barrier transport and deep level transient spectroscopy measurements give evidence for self-passivation of defects produced by H.
Synthesis of Boron Nitride Film by Ion Beam Deposition
Authors: Xia Z. , Zhang G. L. , Lin W. L.
Published: June 2019

Thin films of cubic boron nitride (c-BN) together with hexagonal one (h-BN) have been prepared by using the ion beam deposition method (IBD). Boron was deposited onto silicon wafers by a sputtering beam of 600 eV argon ions, and the growing films were simultaneously irradiated by nitrogen ions at 200 eV. The films were subsequently characterized by infrared absorption (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and microhardness measurements. The IR spectra show the evidence of BN layer formation by the absorption peaks at about 1350, 1120 and 810 cm−1, which are in good agreement with those of bulk BN.
The Role of Dilution Gas in Plasma Deposition of Amorphous Hydrogenated Carbon
Authors: Lu Hsueh Yi , Petrich Mark A.
Published: June 2019

We have studied the effect of hydrogen dilution on the structural and optical properties of plasma-deposited amorphous hydrogenated carbon. Electron spin resonance reveals that the dangling bond density does not change with hydrogen dilution, presumably because there is an excess of hydrogen present during these depositions. Information from 13C NMR, however, shows that hydrogen dilution induces changes in composition, hydrogenation, sp2/sp3 carbon bonding ratio, and the size of sp2 bonded clusters. These changes modify the electronic band structure, as observed by shifts in optical measurements.
Ion Bean Deposition of Multilayer Magnetic Films
Authors: Senda Masakatsu
Published: June 2019

This work investigates the modification of Fe based ion beam sputtered magnetic multilayer films in order to realize good soft-magnetic properties. Fe is used as the main magnetic material because it is the single element with the highest saturation magnetization. Then, I attempt to obtain Fe with zero magnetostriction and soft-magnetic properties artificially using a multilayering technique, while maintaining the highest possible saturation magnetization. Magnetostriction is changed by one of two following causes: by a change in the balance between positive and negative magnetostriction layers, as seen in for example Fe/Co film, or by a change in crystal orientation, as seen in for example Fe/Si02 film. Multilayer film with positive and negative magnetostriction layers is confirmed to show the same inverse magnetostrictive effect as that in uniform film. Also, the small crystal grains and the magnetostatic coupling cause a decrease in anisotropy dispersion, and lead to soft-magnetic properties, in the multilayer films. Additionally, the minimum coercivity in Fe/ SiO2 film corresponds well to the maximum in-plane uniaxial anisotropy and the minimum perpendicular anisotropy where magnetization is restricted almost completely in the plane.
Island Evolution During Early Stages of Ion-Assisted Film Growth: Ge ON SiO2
Authors: Nikzad Shouleh , Atwater Harry A. , Watson Thomas J.
Published: June 2019

Microstructure evolution has been studied in the early stages of growth of polycrystalline Ge on SiO2 in ultrahigh vacuum by ion beam-assisted deposition, and has been systematically compared to conventional thermal film growth. Experimental results indicate that, at equivalent substrate coverages, films grown by ion beam-assisted deposition exhibit increased island density and decreased island size with respect to thermally-deposited films. The increased island density is not a result of an increased island nucleation rate associated with defects produced in the SiO2 substrate during ion beam-assisted deposition. Instead, a new model for ion beam-induced adatom desorption from islands is proposed to account for the increased island density and decreased island size.
Properties of SiO2 Films Fabricated by Microwave Ecr Plasma Processing with and Without Energetic Particle Bombardment During Film Deposition Part I. Fabrication Processes and Physical Properties
Authors: Chau T. T. , Mejia S. R. , Kao K. C.
Published: June 2019

Silicon dioxide (SiO2) films were fabricated by microwave ECR plasma processing. Two groups of films were fabricated; group A with the substrates placed in a position directly facing the plasma so that the substrates as well as the on-growing films were subjected to bombardment of energetic particles produced in the plasma, and group B with the substrates placed in a processing chamber physically separated from the plasma chamber in order to prevent or suppress the damaging effects resulting from these energetic particle bombardment. The systems used for fabricating these two different groups of samples are described. The films were deposited at various deposition temperatures. On the basis of the deposition rate as a function of deposition temperature the film growth for group A samples is due mainly to mass-limited reaction, and that for group B samples is due to surface rate limited reaction. The stoichiometric level for group A does not change with deposition temperature though the films density increases with increasing deposition temperature. However, group B samples exhibit an off-stoichiometric property but they become highly stoichiometric as the deposition temperature is increased beyond 200 °C
Cubic Boron Nitride Prepared by an ECR Plasma
Authors: Osaka Y. , Okamoto M. , Utsumi Y.
Published: June 2019

A number of deposition techniques for cubic BN films from the vapor phase at low pressures have been proposed. We show that the essential factor for creating cubic BN films is a negative self-bias applied to the substrate. The optical and mechanical properties of the deposited films are characterized by reflectance and stress measurements, respectively.
The ECR-Plasma Deposition of Silicon Nitride on a Tunnel Oxide
Authors: Barbour J. C. , Stein H. J , Outten C. A.
Published: June 2019

Gate dielectric-quality silicon nitride films were deposited on a tunnel oxide from an SiH4/N2 gas mixture using an electron cyclotron resonance (ECR) plasma. Electrical characteristics depend not only upon the quality of the nitride film but also upon the state of the interfacial oxide. Quasi-static and 1 MHz capacitance-voltage measurements show that a nitride film deposited at 200°C on 2 nm thick thermally-grown oxide (tunnel oxide) on an unbiased Si substrate have an interface state density of l.5×1011/cm2-eV. Time-of-flight elastic recoil detection (TOF-ERD) was used to examine the level of mixing between the tunnel oxide and the deposited silicon nitride as a function of bias voltage. TOF-ERD showed that for an applied bias of −350 V (ion energy ≈ 380 eV), the deposition of a 10 nm thick film was completely mixed to form an oxynitride whereas the tunnel oxide remained intact for an unbiased sample. (Interdiffusion resulting from energetic-beam heating was ruled-out as a possibility for the mixing.)
Laser and Thermal Annealing of Co-Implanted Si Studied by Mossbauer Spectroscopy
Authors: Langouche G. , de Potter M. , Van Rossum M. , de Bruyn J. , Dezsi I. , Coussement R.
Published: June 2019

Mössbauer spectroscopy was used to study the lattice location of Fe in Si. Strikingly different spectra were recorded depending on the implantation dose and implantation temperature. Drastic changes were also observed in the spectra upon thermal treatment or laser irradiation of the samples. Implantation profiles of several of these sources were also measured. Laser irradiation and thermal annealing above 400° C results in surface segregation of the implanted 57 Co activity.
A Study on Hermetic Glass Sealing Using a Modified Direct Bonding Method
Authors: Ju B. K. , Ko C. G. , Lee Y. H. , Kang I. B. , White P. , Samaan N. , Haskard M. , Oh M. H.
Published: June 2019

This paper presents the process and experimental results about the improved initial bonding between #7740 glass and silicon wafers. We employed a modified initial bonding procedure, called by water-enhanced direct bonding(WDB) technique, and could obtain large initially-bonded area(≥ 95% of the whole wafer area) at room temperature and high interface energy (≥ 2,000 erg/cm2) through 250 °C post-annealing even though the glass wafer had high surface roughness. The main factors contributing to the wider bonded area and higher interface energy in the developed WDB process could be inferred the increase of chemical species (oxygen and hydroxyl groups) responsible for initial hydrogen bonding and conversion from hydroxyl bonds to siloxane bonds in the temperature range between room temperature and 250 °C.
Fabrication Processes and Characteristics of Microelectromechanical System Using PZT Films
Authors: Yoon Y. S. , Kim J. H. , Lim T. H. , Bonne U. A. , Schmidt A. M. , Polla D. L.
Published: June 2019

This paper gives a brief overview of fabrication problems and solutions for microelectromechnical system (MEMS) using PZT films based on surface micromachining techniques. In addition we report characteristics of PZT films on diagnostic test structures designed to test the new bottom electrode for MEMS. PZT(53/47) films were deposited by metalorganic decomposition on a 3″ silicon wafer with Pt/Ti/TiO2/Poly-Si/Si3N4 structure in order to fabricate piezoelectric cantilever beam microaccelerometers and uncooled infrared (IR) detectors. In order to investigate the feasibility of RuO2/Ru and Pt/RuO2 conducting layers as a new bottom electrode for piezoelectric MEMS, the piezoelectric constant (d33) of the PZT films on each bottom electrode was measured. Furthermore, we show the fraction of working top electrodes among 20 total electrodes according to electrode size to investigate the stability of PZT with different bottom electrodes. These results suggest that RuO2/Ru and Pt/RuO2 are possible for bottom electrodes of MEMS.
Pulsed Laser Deposition and Acoustic Property of Piezoelectric / Nonpiezoelectric Multilayer Films
Authors: Hu W. S. , Liu Z. G. , Chen Y-F. , Yu T. , Zhao H. W. , Hu X. B. , Liu X. , Wu R. X.
Published: June 2019

Piezoelectric/nonpiezoelectric multilayer films were prepared by using pulsed laser deposition technique. The piezoelectric ZnO layers were completely (0001) textured and had the piezoelectric coefficient d33. The nonpiezoelectric (inactive) Al2O3 layers were amorphous and acted as good media for microwave and supersonic wave propagation. The periods were controlled by the deposition time in the range of 2.0 to 400 nm with the total period number of 4 to 30. In the multilayer films with ultrashort period of 2.1 nm, (0002) X-ray diffraction peak of ZnO layers was considerably broadened by the noncrystalline Al2O3 layers. In the multilayer films with short period of 6.4 nm, the diffraction peaks presented in small angle implies that the interfaces between layers were much flat and sharp, And in the multilayer films with long period, (0002) peak was very sharp, similar to the normal ZnO thin films. High frequency resonance was measured in the long-period multilayer films in the range of 1 - 20 GHz and higher frequency resonance is expected in the multilayer films with shorter period.
A New Technique for Measuring Poisson's Ratio of Mems Materials
Authors: Sharpe W. N. , Vaidyanathan K. R. , Yuan Bin , Edwards R. L.
Published: June 2019

New techniques and procedures for measuring Poisson's ratio of MEMS materials are presented. Tensile specimens of polysilicon that are 3.5 μm thick are pulled in a small test machine that has a linear air bearing to eliminate friction. Biaxial strain is measured directly by laser-based interferometry from four gold lines deposited on the specimen surface. The value of Poisson's ratio for vapor-deposited polysilicon is 0.22 +/- 0.01 as determined from 19 tests..
Photoconductivity in Vacuum Deposited Films of Silicon-Based Polymers
Authors: Okumoto H. , Shimomura M. , Minami N. , Tanabe Y.
Published: June 2019

Silicon-based polymers with σconjugated electrons have specific properties; photoreactivity for microlithography and photoconductivity for hole transport materials. To explore the possibility of combining these two properties to develop photoresists with electronic transport capability, photoconductivity of polysilanes is investigated in connection with their photoinduced chemical modification. Increase in photocurrent is observed accompanying photoreaction of poly(dimethylsilane) vacuum deposited films. This increase is found to be greatly enhanced in oxygen atmosphere. Such changes of photocurrent can be explained by charge transfer to electron acceptors from Si dangling bonds postulated to be formed during photoreaction.
Hardening of Nickel Alloys by Ion Implantation of Titanium and Carbon
Authors: Myers S. M. , Follstaedt D. M. , Knapp J. A. , Christenson T. R.
Published: June 2019

Dual ion implantation of titanium and carbon was shown to produce an amorphous surface layer in annealed bulk nickel, in electroformed Ni, and in electroformed Ni7 5Fe 2 5. Diamond-tip nanoindentation coupled with finite-element modeling quantified the elastic and plastic mechanical properties of the implanted region. The amorphized matrix, with a thickness of about 100 nm, has a yield stress of approximately 6 GP and an intrinsic hardness near 16 GPa, exceeding by an order of magnitude the corresponding values for annealed bulk Ni. Implications for micro-electromechanical systems are discussed.
Impact of Electrodes on Gate Oxide Reliability: Examples from Isolation and Gate-Stack Processing
Authors: Chapek D. L. , Schuegraf K. F. , Thakur R. P. S.
Published: June 2019

This paper discusses the challenges involved in improving gate oxide reliability for advanced integrated circuits through review of literature and other relevant data. We believe that gate oxide reliability improvements can be engineered by paying special attention to the process conditioning of the top and bottom electrode components of the thin oxide dielectric system in advanced ULSI technologies. We present examples that demonstrate the impact of process and materials on the performance of thin oxide. The data encompasses the effects of substrate, isolation, and top electrodes on gate oxide quality using a variety of methodologies to assess reliability.
Chemical Bonding and Si-SiO2Interface Reliability: (A) Minimization of Suboxide Transition Regions, and (B) Monolayer Incorporation of Nitrogen
Authors: Lucovsky G.
Published: June 2019

This paper addresses two aspects of the chemical bonding arrangements at Si-SiO2interfaces that impact significantly on electrical performance and reliability of devices with ultrathin gate dielectrics with oxide equivalent thicknesses, toxeq, in the regime of direct tunneling; i.e., toxeq< 3 nm. These are i) minimization of suboxide bonding arrangements that contribute to roughness in an interfacial transition region, and ii) monolayer nitrogen atom incorporation.
The Energy Release Rate for Decohesion in Thin Multilayered Films on Substrates
Authors: He Ming. Y. , Xu Guanghai , Clarke David R. , Ma Qing , Fujimoto H.
Published: June 2019

The strain energy release rates for the converging decohesion crack in a multilayered film on a substrate have been calculated using the finite element method. The results for the energy release rate as a function of the intrinsic stress, the thickness of the superlayer and the modulus ratio will be presented. A simple functional form for the results will be shown. The effects of plasticity of the thin metal layer on the energy release rate have been examined. The results show that the effect of plastic deformation is not significant for the converging decohesion crack. The effects of the line width have also been addressed. The results show that for two-layer films the energy release rate for steady-state decohesion cracks decreases dramatically as B/h decreases, in the range B/h<40, where B is the line width and h is the thickness of the superlayer. For narrow lines the plane strain solutions overestimate the energy release rate. The numerical results are consistent with the experimental observations on lines with different width.
Characterization of Hole Traps Generated by Electron Injection in Thin SiO2 Films
Authors: Brożek Tomasz , Lum Eric B. , Viswanathan Chand R.
Published: June 2019

MOS device stability can be significantly affected by charge trapping in the gate oxide, which changes device parameters and causes serious reliability problems in transistors and memory cells. Hole traps, generated by high-field electron injection, are studied in this work in devices with thermal oxides less than 10 nm thick. PMOS transistors, after various doses of positive and negative Fowler-Nordheim injection and post-stress annealing, are subjected to substrate hot hole injection to investigate hole trapping kinetics. Parameters of hole traps, generated under the stress, are studied as a function of gate oxide thickness and electron injection dose.
Micromechanics Measurements Applied to Integrated Circuit Microelectronics
Authors: Clarke David R.
Published: June 2019

As in other engineered structures, fracture occasionally occurs in integrated microelectronic circuits. Fracture can take a number of forms including voiding of metallic interconnect lines, decohesion of interfaces, and stress-induced microcracking of thin films. The characteristic feature that distinguishes such fracture phenomena from similar behaviors in other engineered structures is the length scales involved, typically micron and sub-micron. This length scale necessitates new techniques for measuring mechanical and fracture properties. In this work, we describe non-contact optical techniques for probing strains and a microscopic “decohesion” test for measuring interface fracture resistance in integrated circuits.
Scanning Stiffness Microscopy - A Novel Technique for Detecting Sub-Surface Cracks
Authors: Saha Ranjana , Tsui Ting Y. , Ross C. A. , Nix William D.
Published: June 2019

Thin film delamination and sub-surface cracking represent important reliability issues for the semiconductor and thin film magnetic hard disk industries. Detecting such defects is often difficult and requires complicated specimen cross-sectioning and imaging. Because the sample preparation process itself may cause crack growth, such a method may be used only as a qualitative tool for defect characterization. In the present work, we introduce an in-situ non-destructive technique for detecting sub-surface cracks by continuously monitoring the contact stiffness while dragging a probe across a smooth surface at an ultra light load. As the probe encounters a sub-surface crack, the local contact stiffness decreases dramatically. The amount of reduction in contact stiffness depends on the crack size and geometry and the position of the crack relative to the surface. Results of the scanning stiffness microscopy experiments conducted on hard carbon and chromium thin films are described and discussed.
Adhesion Measurement of Interfaces in Multilayer Interconnect Structures
Authors: Ma Qing , Bumgarner John , Fujimoto Harry , Lane Michael , Dauskardt Reinhold H.
Published: June 2019

Interface decohesion is increasingly becoming a reliability concern in multilayer interconnect structures. It is therefore necessary to provide adhesion tests as a part of materials characterization procedures and to study the fundamental material properties that affect interface toughness. A sandwich structure 4-point bend test was developed for measuring the adhesion between interlayer dielectric and metal interfaces. This technique offers well defined and easily controllable fracture processes and simple analyses based rigorously on fracture mechanics. Using this technique, a number of interfaces were studied. For conventional interconnect systems consisting of Al lines and SiO2 as the interlayer dielectric, the focus was to improve the interface fracture toughness through structure design and process engineering. Potential low dielectric constant materials, such as polymers and porous SiO2, were also studied as candidates for interlayer dielectric materials in the future. Interface strengthening effects of both mechanical and chemical origin, including interface roughness and thin film plasticity, as well as alteration of chemical bonding were explored.
Simulation of the Effect of Dielectric Air Gaps on Interconnect Reliability
Authors: Bassman L. C. , Vinci R. P. , Shieh B. P. , Kim D.-K. , McVittie J. P. , Saraswat K. C. , Deal M. D.
Published: June 2019

We present a modeling strategy for assessing the reliability cost for improved performance from modified interconnect structures. We have studied air gaps which have been deliberately introduced in the passivation between aluminum interconnect lines as a means for increasing transmission speed by decreasing dielectric capacitance. The models allow examination of tradeoffs between improved circuit performance and decreased reliability due to dielectric cracking. Stresses in the dielectric due to electromigration in the metal were modeled using finite element analysis. These stresses were used to compute an estimate of the mean time to failure relative to the case with no air gap using an electromigration failure model from MIT.
Adhesion Assessment of Copper Thin Films
Authors: Kriese M. D. , Moody N. R. , Gerberich W. W.
Published: June 2019

Nano-indentation testing has been used to quantitatively assess the adhesion of thin copper films, sputtered to thicknesses of 150 nm to 1500 nm. Copper films of low residual stress were deposited via RF diode cathode sputtering onto SiO2/Si substrates. Overlayers of DC magnetron sputtered high residual stress tungsten, 850 nm thick, were additionally used to provide a driving force for delamination. All films tested exhibited buckle-driven delamination, from which the interfacial toughness was estimated to be 0.2 – 2 J/m2, which is comparable to the thermodynamic work of adhesion. The use of an overlayer requires extensions of existing models, but otherwise does not change the interfacial adhesion, allowing measurements of films that would not otherwise delaminate.
Nanoindentation Hardness of Soft Films on Hard Substrates: Effects of the Substrate
Authors: Tsui T. Y. , Ross C. A. , Pharr G. M.
Published: June 2019

The ability to accurately measure the mechanical properties of thin metallic films is important in the semiconductor industry as it relates to device reliability issues. One popular technique for measuring thin film mechanical properties is nanoindentation. This technique has the advantage of being able to measure properties such as hardness and elastic modulus without removing a film from its substrate. However, according to a widely-held rule of thumb, intrinsic film properties can be measured in a manner which is not influenced by the substrate only if the indentation depth is kept to less than 10% of the film thickness, which is often not practical. In this work, a method for making substrate independent hardness measurements of soft metallic films on hard substrates is proposed. The primary issue to be addressed is the substrate-induced enhancement of indentation pile-up and the ways in which this pile-up influences the contact area determined from analyses of nanoindentation load-displacement data. Based on experimental observations of soft aluminum films on silicon, glass, and sapphire substrates, a simple empirical relationship is derived which relates the amount of pile-up to the contact depth. From this relationship, a simple method is developed which allows the intrinsic hardness of the film to be measured by nanoindentation methods even when the indenter penetrates through the film into the substrate.
Electrostatic Adhesion Testing for the Evaluation of Metallization Adhesion
Authors: Yang H. S. , Brotzen F. R. , Callahan D. L. , Dunn C. F.
Published: June 2019

Quantitative measurement of the adhesion strength of thin film metallizations has been achieved by a novel technique employing electrostatic forces to generate delaminating stresses. This technique has been used in testing the adhesion of Al-Cu, Cu, and Al multilayer films deposited on Si. Micro-blister-type failure is revealed by scanning electron microscopy. The delamination process and the geometry of the blister are discussed. The measured adhesion data fit a Weibull distribution function.
Failure Lifetime Prediction Of Cracked Concrete Structures
Authors: Barpi F. , Chille' F. , Imperato L. , Valente S.
Published: June 2019

This paper presents the results of creep tests on three notched dam models made with three type of concrete. In order to characterise the time-dependent behaviour of the process zone, a series of tensile tests was performed for each kind of concrete. On the basis of the law obtained in this way, crack propagation was simulated numerically through the Cohesive Crack model.
The Future Of Nde Applications To RPV Embrittlement Measurements
Authors: Vassilaros M. G.
Published: June 2019

Assuring the integrity of nuclear power plant reactor pressure vessels (RPV) is of upmost importance to the U.S. Nuclear Regulatory Commission since there is no backup or redundancy to this component. These vessels must maintain high toughness in order to assure integrity despite the fact the vessel toughness decreases with neutron irradiation from the running of the plant. Currently the toughness loss of the RPV is inferred from generic equations or the change in measured toughness of samples irradiated in the RPV. A nondestructive evaluation technique
to monitor the toughness of the RPV would enhance integrity assessments of the vessel. Such an NDE technique must have the ability to measure the microstructural changes resulting from irradiation that effect the toughness of the RPV steel. Additionally the technique must be able to investigate the RPV through the thickness without removing the stainless steel weld cladding on the surface. Although the development of such an NDE technique may be difficult the U. S. NRC is supporting such research in hopes of developing more information concerning the toughness of U. S. RPVs.
The Riddle Of Nde For Embrittlemient Detection
Authors: Blaszkiewicz M.
Published: June 2019

The ability to nondestructively determine the level of irradiation induced degradation in nuclear reactor pressure vessels (RPVs) would enhance the integrity assessment currently used by the nuclear industry. Presently, destructive testing of Charpy specimens from surveillance capsules is used to approximate the RPV upper shelf energy and the ductile-to-brittle transition temperature, and approved models and guidelines are used to determine the state of embrittlement. However, these models and surveillance programs do not always provide enough accurate information to support decisions for premature RPV life termination, life continuation to license expiration, or life renewal and extension by means of annealing. Effective nondestructive techniques would extend the usefulness of the surveillance material by reducing the amount of material used for destructive studies, and ultimately by allowing tests to be performed directly on the RPV. Nondestructive techniques, ranging from electrical resistivity to hyperfine interactions, have been, and continue to be, explored for use in embrittlement assessment. The current states of these various techniques are discussed, and future directions for research are suggested.
Preliminary Results On Ultrasonic Attenuation Detection Of Neutron Irradiation Embrittlement Of Nuclear Reactor Steel
Authors: Hiser A. L. , Green R. E.
Published: June 2019

Neutron bombardment of reactor pressure vessel (RPV) steels causes reductions in fracture toughness in these steels, termed neutron irradiation embrittlement. Currently there are no accepted methods for nondestructive determination of the extent of the irradiation embrittlement nor the actual fracture toughness of the reactor pressure vessel. This paper provides preliminary results of an effort addressing the use of ultrasonic attenuation as a suitable parameter for nondestructive determination of irradiation embrittlement in RPV steels.
Ultrasonic Nde Of Radiation Damage
Authors: Tittmann B. R.
Published: June 2019

Irradiation degrades the fracture toughness of reactor pressure vessel steels. To date no satisfactory method has been developed to nondestructively measure the loss of fracture toughness. Metal embrittlement is often associated with impurity pinning of dislocations. A review is presented of the interaction of dislocations with ultrasonic waves to give rise to attenuation or internal friction. The emphasis is on amplitude dependent attenuation due to dislocation breakaway from pinning points. Recommendations for future work are provided.
Service Life Prediction And Choice Of Repair Strategy For Rc Structures
Authors: Henriksen Carsten
Published: June 2019

The accumulating damage to concrete structures during the last years has led to an increasing need for repair work.

The need for concrete repairs is not likely to change in the future, not until all old concrete structures have been repaired or rehabilitated through preventive maintenance.

Both repair and preventive maintenance of a concrete structure require economic investment, not only at present, but also in the future. A repair does not last forever and preventive measures (e.g. surface treatment) require regular maintenance. Society does not have unlimited resources for the repair and maintenance of concrete structures. Consequently, there is a need for optimization of the resources, i.e. using few resources in the best way at the right time.

It is therefore necessary to base the repair/maintenance on technical and (in particular) economic evaluations.

The following describes a model for evaluation of the technical and economic need for repair/maintenance of concrete structures.
Fiber Optic Sensing the Behavior of Prestressed-Prism-Reinforced Composite Concrete Beams for Bridge Deck Application
Authors: Nawy Edward G. , P. E.
Published: June 2019

This investigation involves the identification and use of a novel type of fiber optic sensors in monitoring the deformation behavior of critical sections of the structural concrete elements and transforming them into smart systems. Basic operating principles of the Bragg-grating sensors identified in this work are proved to be feasible. Deformational behavior was studied of high performance concrete composite beams reinforced with prestressed prisms and instrumented with Bragg Grating fiber optic sensors. The experimental techniques using those sensors for evaluating their behavior at service load stages, and the potential of this technique for on-line, real-time monitoring of existing constructed concrete structures are presented.
Non-Invasive Monitoring of Acute Intracranial Mass Lesions Using Ultrasonic Fingerprinting
Authors: Nagy P. B. , Rosenberg W. S. , Stankovits L. M.
Published: June 2019

Potentially dangerous neurological changes in shock-trauma patients are currently monitored by computer-aided X-ray tomography which is prohibitively expensive and even dangerous for long-term, e.g., comatose, patients. By ultrasound, only low-frequency “diffuse” ultrasonic inspection is feasible through the skull so that the details are irreversible lost in the essentially random scattering process. In order to overcome this inherent limitation, we adapted a continuous computer-controlled ultrasonic monitoring system based on the ultrasonic fingerprinting method originally developed for materials characterization purposes in the nuclear, civil engineering, and aerospace industries. An ultrasonic detector directed at the general area of interest can be used to record and repeatedly update the personal signature of the patient, which is then used as an “ultrasonic fingerprint.” Any abrupt change in this signature indicates the immediate need for further investigation by CT or other sophisticated diagnostic tools. Experimental studies were conducted on both a human skull/gelatin phantom and 5 intact human cadavers. Ultrasonic fingerprinting could detect the secondary effects of volumetric changes occurring at multiple locations and the average detectable volumes of mass lesions were found to be lower than indications for surgical intervention.
A Digital Mems-based Strain Gage for Structural Health Monitoring
Authors: Maclean B. J. , Mladejovsky M. G. , Whitaker M. R. , Olivier M. , Jacobsen S. C.
Published: June 2019

One approach for structural health monitoring of aging aircraft is to take discrete airframe strain measurements and record the flight loads history. A complementary method consists of measuring changes in dynamic response due to fatigue crack growth. The challenge in implementing such methods is the need for inexpensive networks of distributed strain sensors which possess high resolution with no drift over time. The Uni-Axial Strain Transducer (UAST) has been developed as a digital, absolute encoding device to address these very issues. The UAST is a micro-electromechanical system (MEMS) which exploits the capacitive coupling between an array of electrostatic field emitters and an array of 64 field detectors on a CMOS IC chip. The slightly different array element spacings form a vernier scale and digital signal processing of the detector outputs is used to calculate the absolute translational displacement of the emitter array relative to the CMOS detector chip. The UAST provides a dynamic range of 11,500 μ-strain and displacements of 2.5 nm are easily resolved. The sensor sampling rate is dynamically configurable for 150, 290, 540, 1000, 1600 or 2500 Hz, providing 15, 14, 13, 12, 11, or 10 bits of resolution (equal to 0.35, 0.7, 1.4, 2.8, 5.6, or 11.4 μ-strain), respectively. The sensor network can communicate with up to 128 UASTs on a common 5-wire digital bus, eliminating the need for shielding and considerably reducing the number of wires which will have to be routed through the airframe. A network technology demonstration is being conducted on a 1/2 scale F-I 8 vertical tail where dynamic loads are applied to evaluate network performance related to monitoring of fatigue crack growth or rivet-line failures. Application of the UAST in a helicopter rotor health usage and monitoring system, and the design of a bi-axial transducer under development, are also mentioned.
Application Of Dielectric Analysis To The Study Of Ageing In Adhesive Bonded Structures
Authors: Pethrick Richard A. , Joshi Sadanand B. , Hayward David , Li Zhi-Cheng , Halliday Steven , Banks William M. , Gilmore Ray , Yates Lawrence W.
Published: June 2019

Dielectric techniques have the potential of allowing observation of changes in the dipole mobility within an adhesive joint structure as a result of its exposure to a warm humid environment. Water molecules absorbed by an adhesive resin will exhibit a series of distinct relaxation features, which are characteristic of the environment in which the molecules are located. Hydration of the surface oxide of an aluminium-epoxy joint will produce a distinctive dielectric relaxation at approximately 1 MHz which is quantitatively related to the amount of hydroxide formed. Data on aged adhesive joints indicates that the dielectric technique has potential for the study of the changes occurring within the joints and the technique may be also used for studies of carbon fibre - epoxy - carbon fibre structures.
Fiber Breakage In Polymer-Matrix Composites During Static And Fatigue Loading, Observed By Electrical Resistance Measurement
Authors: Wang Xiaojun , Chung D. D. L.
Published: June 2019

By measuring the electrical resistance of a continuous unidirectional carbon fiber epoxy-matrix composite along the fiber direction during loading in this direction, fiber breakage was progressively monitored in real time. Fiber breakage occurred in spurts involving 1000 fibers or more. It started at about half of the failure strain during static tensile loading and at about half of the fatigue life during tensiontension fatigue testing. Immediately before static failure, 35% of the fibers were broken. Immediately before fatigue failure, 18% of the fibers were broken. The fiber breakage was accompanied by decrease in modulus.
Strategies For Nde Of Fiber Reinforced Polymer Structural Components
Authors: Duke John C.
Published: June 2019

A strategy for selecting and developing nondestructive evaluation (NDE) methodologies for fiber reinforced polymer composite structural components to be used in civil infrastructure applications is described. Conventional and innovative evaluation approaches are discussed.

Actual experience with NDE of hybrid carbon and glass fiber reinforced vinyl ester pultruded
beams that are installed in a bridge carrying automotive traffic is described.
Epoxy Cure Monitoring With An Interdigitated Gate Electrode Field Effect Transistor (IGEFET)
Authors: Kolesar E. S. , Wiseman J. M.
Published: June 2019

An interdigitated gate electrode field-effect transistor (IGEFET) was designed, fabricated and used to monitor the cure of a common epoxy. The IGEFET sensor consists of an interdigitated gate electrode structure which is coupled to the gate contact of a conventional metal-oxide-semiconductor field-effect transistor (MOSFET). The epoxy was deposited on the interdigitated gate electrode, and the IGEFET's electrical performance was observed as the epoxy cured. The cross-linking chemical reaction during epoxy cure caused electrical impedance changes that were quantified when the IGEFET was operated with a periodic voltage pulse signal. Charge transferred through the chemically-active epoxy is manifested as a temporally-dependent potential applied to the MOSFET's gate contact. By operating the MOSFET as a linear amplifier, a potential corresponding to the temporally-dependent gate voltage was directly measured at the amplifier's output. The Fourier transform of the IGEFET's time-domain response at specific time increments was computed. The resulting epoxy cure spectra were compared to a reproducible baseline spectrum, and an ensemble of difference spectra were computed to reveal the epoxy's chemical state at specific instances of time. The difference spectra features yield valuable information concerning the state of the epoxy's cure.
Investigation of the V4+-Centre in 6H- and 4H-SIC by the Method of Spectral-Hole Burning
Authors: Hecht C. , Kummer R. , Winnacker A.
Published: June 2019

In the context of spectral-hole burning experiments in 4H- and 6H-SiC doped with vanadium the energy positions of the V4+/5+ level in both polytypes were determined in order to resolve discrepancies in literature. From these numbers the band offset of 6H/4H-SiC is calculated by using the Langer-Heinrich rule, and found to be of staggered type II. Furthermore the experiments show that thermally stable electronic traps exist in both polytypes at room temperature and considerably above, which may result in longtime transient shifts of electronic properties.
Reduced Modulus Acrylic Bone Cement
Authors: Litsky Alan S. , Rose Robert M. , Rubin Clinton T.
Published: June 2019

Loosening is the dominant long-term problem facing joint replacement surgeons and patients. A probable cause of endoprosthesis loosening is the strain singularity at the material interfaces. The concentration of shear at the bone-cement interface leads to micromotion which precipitates a soft-tissue membrane and resorption of the cancellous bone.

A more compliant cement would substantially reduce the interfacial stresses and serve as a “pillow” between the prosthetic stem and the cancellous bone. We have developed a surgically-workable formulation of a reduced modulus acrylic bone cement — polybutylmethylmethacrylate (PBMMA) — to test this hypothesis. Materials property testing and in vivo implantation are discussed.
Use of Bone Morphogenetic Protein (BMP) and Cancellous Graft for Porous-Surfaced Interface Voids
Authors: Kim W. C. , Rechl H. , Amstutz H. C. , Hermens K. , O'carroll P. F. , Kabo M. , Urist M.
Published: June 2019

It is known that bony ingrowth implants without intimate apposition results in diminished ingrowth. In this study the use of bone morphogenetic protein (BMP) and cancellous bone graft to augment ingrowth in interface voids is investigated in the canine. Eight CoCr surface replacement hip implants of chamfered cylinder design with beaded CoCr porous layer were implanted in four adult canines and followed from 23 to 56 days. Prior to implantation, cylindrical defects 4mm diameter by 3mm deep were created in the femoral head and acetabular surfaces and filled with 10mg of BMP in one hip and cancellous bone graft in the contralateral hip. Animals were followed with serial radiographs to sacrifice after which microradiographs of ground sections and histologic specimens were analyzed. All defects were 100% filled with viable new bone without differences in density, organization, or ingrowth in the BMP and cancellous specimens. Femoral specimens uniformly showed unexpected seating gaps which were bridged to varying degrees with viable new organized bone. In five femoral cases seating defects of 2mm or more were completely bridged with ingrowth at the porous layer. In one acetabular case a 6mm gap was 90% bridged. No correlation of results was noted with time to sacrifice. It was concluded that new bone present in the seating gaps was most likely due to spillage of material from the cylindrical defects. Although the amount of ingrowth required for durable fixation is unknown, incongruencies of implant fit are common. As BMP showed no discernible advantage over cancellous graft in results of this study we advocate liberal use of readily available cancellous graft (from reamings or femoral head) to fill interface voids.
Ion Implantation as a Tool for Improving the Properties of Orthopardic Alloys
Authors: Higham P. A.
Published: June 2019

Ion Implantation is emerging as a specialized surface treatment method by which orthopaedic alloys can be doped in order to modify for corrision, fatigue and wear properties.

In this paper alterations in the corrosion and fatigue resistance of 316LVM stainless steel and Ti 6A1-4V ELI titanium alloy are considered. The effect of various variables was investigated; ion species, flux, accelerating voltage.

Changes in corrosion resistance were monitored by performing anodic polarization studies in deaerated 0.1M NaCi solution at 22°C. The most effective species were found to be tantalum and boron for improvements to stainless steel.

Fatigue properties were investigated using a Wohler type rotating bend test. Preliminary results show that nitrogen ion implantation improved the fatigue life for the steel but not the titanium alloy. Indications were found to suggest that time since implantation affect the fatigue properties.
Bioelectrodes for Neural Prostheses
Authors: Hambrecht F. Terry
Published: June 2019

Neural prostheses which are commercially available include cochlear implants for treating certain forms of deafness and urinary bladder evacuation prostheses for individuals with spinal cord disorders. In the future we can anticipate improvements in bioelectrodes and biomaterials which should permit more sophisticated devices such as visual prostheses for the blind and auditory prostheses for the deaf based on microstimulation of the central nervous system.
Electronic Materials in Biological Applications
Authors: Regnault William F. , Picciolo Grace Lee
Published: June 2019

Decisions concerning patient care, which are routinely made by the attending physician, based on experience and clinical laboratory analyses, will eventually be supplemented or even replaced by real-time, quantified, health assessments from cutaneous and indwelling multisensor probes. These probes will employ a multitude of technologies including optical and solid state techniques for the precise measurement of body analytes such as blood gases, electrolytes, pH, glucose, etc. In addition to clinical monitoring, these sensors will also be used to provide feed-back for closed-loop therapeutic systems.

Currently, there are rapid advances being made in sensor technology and its application for the determination of various analytes. However, a major problem still remains at the device/body interface, especially when chronic implantation is required.
Effects of Relaxin on the Mechanical Properties of Collagen Rich Tissues
Authors: Dylewski John R. , Larkin L. H. , Beatty C. L.
Published: June 2019

A collagenous scar capsule forms around biomaterial implants and for deformable implants such as a breast prosthesis, this phenomenon of capsular scar contracture may lead to deformation and hardening of the implant. Relaxin, a peptide hormone of pregnancy which is known to affect collagen rich tissues, was given to mice in an attempt to eliminate or lessen this contracture. A short (8 day) study was performed to observe the effects of relaxin and estrogen on the mechanical properties of Skin and the interpubic ligament. A longer (27 day) study observed the effects of relaxin in estrogen primed mice containing implants. Changes in skin, interpubic ligament, scar capsule and contracture phenomenon were noted. Stress-strain characterization, dynamic mechanical spectroscopy and light microscopy were used to characterize the effects of relaxin and estradiol on the contracture phenomenon. Qualitatively, relaxin given to estrogen primed mice was shown to lessen implant contracture and deformability. Administration of relaxin produced the documented changes in the interpubic ligament, but differences were noted between the 8 and 27 day studies. Differences in the failure stress and strain and modulus for the long implant and short non-implant study were noted for the relaxin treated mice.