bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Scanning Thermal Microprobe
Authors: Zhang Yongxia , Zhang Yanwei , Blaser Juliana , Sriiram T. S. , Marcus R. B.
Published: June 2019

A thermal microprobe has been designed and built for high resolution temperature sensing. The thermal sensor is a thin-film thermocouple junction at the tip of an Atomic Force Microprobe (AFM) silicon probe needle. Only wafer-stage processing steps are used for the fabrication. The thermal response over the range 25–s 4.5–rovolts per degree C and is linear.
Electronic X-Ray Systems For Field Aircraft Inspection
Authors: Gibbs K. M. , Berger H. , Jones T. S. , Davis M.
Published: June 2019

Selected electronic, digital x-ray imaging systems and techniques were evaluated as possible replacements for the use of x-ray film at Air Force field aircraft maintenance facilities. Incentives for the introduction of digital systems include the elimination of recurring costs of film, processing, and waste disposal, and the advantages of electronic data analysis, digital signal processing, and the ease of storage, retrieval, and transfer of digital data. Initial experimental evaluations included photostimulable storage phosphors, scintillator-camera systems, flat panel imagers and the reverse geometry method. The technical evaluations were conducted with a test object consisting of typical honeycomb structure containing various faults, line pair gages, and image quality indicators on ¼–inch aluminum. Several electronic systems were capable of meeting most of the technical requirements for x-ray inspection, with system prices attractive for field locations with annual film costs in the range of $15,000 or more. All the electronic methods eliminate processing chemicals and offer advantages in certain applications. However, the storage phosphor systems were particularly well suited for field implementation because of their similarity to film, but without most of the recurring costs and the environmental problems associated with the use of film. These evaluations were conducted under a Small Business Innovation Research (SBIR) Phase I program. More extensive system evaluations are planned as the program continues into an SBIR Phase II project.
Characterization of an Extended Reactive Noble-Metal/III-V Semiconductor Interface: Cu/GaAs(110)
Authors: Joyce J. J. , Weaver J. H.
Published: June 2019

We examine the electronic structure of the Cu/GaAs(110) interface using high resolution synchrotron radiation photoelectron spectroscopy. Analysis of valence band and core level spectra indicate that a reactive, extended interface is formed when Cu is deposited on the cleaved GaAs(110) surface at room temperature. Arsenic 3d core level data show a single reacted component shifted 500 meV to lower binding energy while the Ga 3d core shows a reacted component shifted by 800 meV below the substrate position. Core level attenuation curves indicate preferential As outdiffusion with the As signal at 30% of initial intensity for 100 ML of Cu while the Ga intensity for the same coverage has dropped to 2% of initial intensity. Band bending results show two separate regions of interest with a secondary pinning position 775 meV below the CBM for n-type GaAs. Results are discussed in light of thermodynamic and electronegativity parameters as well as other transition and rare-earth metal GaAs interfaces.
Areas of Need for Future Biomaterials Research
Authors: Lemons J. E.
Published: June 2019

Clinical treatment modalities have undergone very significant changes over the past 30 years, in part because of the development of new or improved synthetic substances (biomaterials) for the replacement of tissues. Most all aspects of medical care have been directly influenced. It is now possible to obtain biomaterials made from basic metallic, ceramic, carbonitic, or polymeric materials where the substance has been manufactured for a specific biomedical application. In past years, this was not possible and available industrial grade materials were often adapted or modified to accommodate applications in biological environments. These developments, along with the many other advances in both biomedical sciences and clinical applications, have provided an exciting situation with regard to the improvement of existing prostheses and materials or the development of new biomaterials for surgical implant devices. This presentation will summarize eight areas where defined needs for active biomaterials research continues, following an outline theme of: (1) the current clinical situation; (2) specific area of need; and (3) possible improvements through basic science and clinical research.

This thematic presentation will consider the following general areas: (1) the minimization of interfacial wear and implant biodegradation with examples of total joint replacements and occlusal surfaces of teeth; (2) adhesives for soft and hard tissues with examples of total joint replacements, cements, cardiovascular and plastic surgery reconstructions; (3) percutaneous devices for orthopaedic, dental, cardiovascular, and general surgery; (4) bone and skin replacements for the treatment of major bone lesions and burns; (5) ligaments and tendons for joint and hand reconstructions; (6) spinal instruments for orthopaedic procedures; (7) conduits of various diameters for general and cardiovascular applications; and (8) valves for cardiovascular and urological procedures.
Fatigue Fracture of Al2O3 Ceramic-to Ceramic Total HIP Replacements
Authors: Walter Adam , Lang W.
Published: June 2019

Fatigue phenomena of high-density alumina ceramic hip joint endoprosthesis with ceramic-to-ceramic articulating components were analyzed for retrieved ex-vivo objects and for in-vitro tests in hip-joint simulators. Scanning electron microscope investigations were employed. The cyclical compression between ball and cup causes severe shear stresses to form below the bearing surfaces. Locally changing subsurface maxima of contact stresses can generate fatigue cracks starting at subsurface microstructural defects and grain boundaries. The fatigue fractures are regarded as being identified with the tribological surfaces of the simulator specimens and of the ex-vivo prostheses retrieved because of fracture.
Results of a Stemmed Bone Ingrowth HIP Resurfacing Arthroplasty in the Canine
Authors: Kim W. C. , Rechl H. , Amstutz H. C. , Hermens K. , O'Carroll P. F. , Kabo M.
Published: June 2019

A stemmed bone ingrowth hip resurfacing arthroplasty designed for use with bone deficient femoral heads raises concerns of stress shielding and is investigated in this study. Ten CoCr bone ingrowth hip resurfacing devices were implanted in five adult canines. Design consisted of a 6mm deep cylindrical cavity with porous beaded surface of 150um pore size and Imm nominal depth. A 3mm diameter smooth CoCr stem was eccentrically fixed to the component for additional fixation with threaded nut at the lateral cortex. Femoral head was reamed for interference fit with hole for the stem placed superiorly. Acrylic fixed polyethylene cups were used for acetabular components. Animals were followed with serial radiographs to sacrifice at 73 to 267 days. After sacrifice microradiographs of ground sections and histologic specimens were evaluated for bone ingrowth, remodeling, and femoral neck attenuation. All specimens showed well ingrown bone at the porous layer. Bone remodeling showed preservation of proximal femoral neck cancellous trabecular pattern and medial cortical support. Resorption of bone at the implant rim and femoral neck thinning were, however, present. Two specimens had neck thinning of 10% or less, four of 10 to 25%, three of 25 to 50%, and one greater than 50%. There was no correlation with time to sacrifice for parameters evaluated. Results indicate preservation of the compressive stresses through the femoral head. Resorption of bone at the rim and femoral neck attenuation, however, indicates load sharing between the implant and bone. Though a lower modulus material such as titanium would decrease load sharing, the geometrical design insures the presence of stress distribution anomalies.
Conductive Polymer Electrodes for Neural Prosthetic Applications
Authors: Foos J. S. , Erker S. M.
Published: June 2019

A variety of materials have been evaluated for use as electrodes for neural stimulation. In an effort to maximize the charge density on the electrode surface, faradaic stimulation electrodes have been investigated. Electrodes consisting of thin films of polypyrrole on Pt have been studied in phosphate buffered saline using cyclic voltammetry at 100 mV/s. The electrode capacity diminishes initially but stabilizes after ˜500 cycles. The electrodes were further evaluated in pulsing experiments using constant current, biphasic pulses. In these experiments, significant charge storage was observed only when using pulse widths greater than 5 ms. A modified polypyrrole was prepared using anthraquinone containing electrolyte. This new material is an apparent improvement over the polypyrrole previously studied.
The Small Diameter Vascular Graft - A Challenging Biomaterials Problem
Authors: Hoffman Allan S. , Ratner Buddy D. , Garfinkle Andy , Horbett Thomas A. , Reynolds Larry O. , Hanson Steven R.
Published: June 2019

The surface composition of a biomaterial can have an important influence on biologic responses. In this paper we report on a surface treatment using a gas discharge which deposits a thin fluorocarbon polymer coating onto tie surface of a synthetic vascular graft. The surface chemistry of the graft is significantly changed, while there is no measurable change in porosity, compliance or surface topography. Treatments with tetrafluoroethylene (TFE) gas yield dramatic improvements in both thrombo and emboli-resistance of the graft, based on in vitro measurements and ex vivo shunt tests in a baboon.
Charged Polymers as Osmotic Agents for Peritoneal Dialysis
Authors: Twardowski Zbylut J. , Nolph Karl D. , Khanna Ramesh , Hain Hannelore , Moore Harold , McGary Terry J.
Published: June 2019

A sustained ultrafiltration during long-dwell peritoneal dialysis exchanges cannot be achieved with rapidly absorbable small molecular weight substances such as commonly used glucose. Uncharged polymeric substances are absorbed slower, but yield insufficient osmotic driving force because osmolality is inversely proportional to the molecular weight.

Charged polymers induce colloid osmotic pressure not only because of the molecules themselves, but also by ions kept in the peritoneal cavity by opposite charges of polymers. In anin vitromodel of peritoneal dialysis, a sustained ultrafiltration has been achieved with several synthetic polymers including polyacrylate, dextran sulfate and polyethylenimine. However, these polymers were locally toxic to the peritoneal membrane when tested in rats and rabbits.

Chemically modified gelatin derivatives, such as polygelin, exypolygelatin, and succinylated gelatin are widely used in Europe as plasma substitutes. They are metabolized and have proven to be systemically non-toxic. These gelatin derivative solutions were tested in rat models of peritoneal dialysis. Up to 10% solutions achieved sustained ultrafiltration at the rate proportional to the concentration and no untoward systemic or local effects on the peritoneum were observed. Absorption of gelatin molecules ranged from 40–60% of the infused amounts. The results of the studies indicate that gelatin derivitives have potential for clinical use as osmotic agents in long-dwell peritoneal dialysis exchanges if the absorption rates in humans are markedly lower than in rats.
Semt-Solid Processing of Titanium Alloys for Biomedical Applications
Authors: Toloui B. , Wood J. V.
Published: June 2019

Among metallic systems, titanium alloys are prime candidate materials for biomedical applications in view of their apparent properties in the body environment. While machined and forged parts of CPTi, or Ti-6Al-4V, are suitable for many applications, they are not economical for one-off objects or artefacts of extreme intricacy. Titanium castings are an obvious solution to the problem but these are extremely difficult to process without contamination. Alloying allows a lowering of the melting point and significantly reduces the risk of contamination but the resultant alloys are normally brittle due to networks of intermetallics forming. This paper describes a process of semi-solid casting using a powder titanium feedstock for making one-off castings of artefacts like those required in dentistry. The process will be described and the mechanical and corrosion properties of several alloys which are compatible with this technique are assessed. The basic process is relatively inexpensive and provides a useful tool for examining a wide range of potential titanium base alloys.
Fractured Steinmann Threaded Fixation Pins Following Vertebral Body Resection and Stabilization: Medical Device Pathological Analysis of Two Cases
Authors: Kossovsky Nir , Dujovny Manuel , McDonnell Dennis , Kossowsky Ram
Published: June 2019

Vertebral body resection in the treatmenL of metastatic neoplasms of the spine is increasingly common for radioresistant tumors. It is also favored for treating progressive neurological disease due to tumor-associated spinal cord compression. Spine stabilization following resection is accomplished by several techniques. Increasing in popularity is the combination of threaded fixation pins and methylmethacrylate filler.

In the two cases reported in this communication, failure of threaded AISI 316 stainless steel pins occured through corrosion fatigue. Corrosion begins at the base of the threads and is exacerbated by galvanic cell formation at the methyl methacrylate-bone interface. Fatigue is experienced because the cervical and vertebral bodies are each a part of a joint that normally experiences 10 – 20 degrees of both antero-posterior and lateral flexion.

We conclude that in active patients, non-threaded cobalt chrome pins are the preferred material for stabilization of the lumbar and cervical spine following vertebral body resections.
Thermoplastic Polyurethanes Softening in 37°C N-Saline
Authors: Zdrahala Richard J. , Mcgary Charles W.
Published: June 2019

The softening of thermoplastic polyurethane (TPU) in the body environment represents one of the major advantages of these biomaterials. Although the literature contains an abundance of hydrolytic stability data, almost no information exists describing the softening of these materials in the body. A series of polyether-based TPUs, consequently, was synthesized based on 4,4′-diphenylmethane diisocyanate/1,4-butanediol hard segment and polytetramethylene ether glycol soft segment and the effect of simulated body environment (37°C n-saline) was studied as a function of the hard segment content and the soft segment glycol molecular weight. A mechanism and phenomenological analysis of this softening are offered and discussed in terms of TPU morphology. Both water and heat, for example, plasticize the TPU to increase the chain mobility; in the body environment this results in a reversible reduction in elastic modulus.
α-BSM™: A Calcium Phosphate Delivery Vehicle
Authors: Knaack D. , Lee D.D.
Published: June 2019

α-BSM™ is an injectable endothermically setting calcium phosphate bone substitute. α-BSM™ has been shown to be effective in promoting the healing of surgically created critical size defects and restoring bone biomechanical strength in several animal models. It has received regulatory clearance for orthopedic indications in both Canada and Europe and for dental and craniofacial indications in the United States.

α-BSM™ is distinguished as a bone substitute by its prolonged working time at room temperature, and rapid hardening at body temperature. These properties, as well as its compatibility with a variety of aqueous hydrating agents, make α-BSM™ an attractive vehicle for thein situdelivery of therapeutic agents.In vitrostudies have shown that antibiotics, such as gentamicin, can be stably incorporated into α-BSM™ prior to and during hardening, and that delivery kinetics can be controlled with the appropriate formulation and preparative procedures. The setting reaction is also compatible with biologically active proteins. rhBMP-2 has been incorporated into α-BSM™ and was demonstrated to be effective in stimulating ectopic bone formation in soft tissue and accelerating the restoration of a differentiated phenotype in a rabbit osteotomy model.
Evaluation of the Strain Field Inside and Around Growth Islands by Means of X-Ray Diffuse Scattering
Authors: Schmidbauer Martin , Wiebach Thomas , Raidt Helmut , Schäfer Peter , hanke Michael , Köhler Rolf , Neumann Wolfgang , Kirmse Holm , Rabe Michael , Henneberger Fritz , Wawra Herbert
Published: June 2019

The strain distribution inside and in the vicinity of coherently strained self-organized islands has been investigated by high-resolution x-ray diffraction (HRXRD). Finite element method (FEM) calculations were carried out in order to calculate the strain field, which was then used to simulate x-ray reciprocal space maps on the basis of kinematical scattering theory. For Si0 75Ge0.25 islands an abrupt increase in the Ge-concentration at about one third of the island height has been found. This behavior can be attributed to different nucleation stages during growth. Highly strained buried CdSe quantum dots (QDs) strongly influence the surrounding ZnSe matrix. From reciprocal space maps and FEM simulations we were able to estimate the shape and size of the islands. The results are in agreement with transmission electron microscopy (TEM) and UHV atomic force microscopy (AFM) data.
Identification of Possible High Integrity Containers for Low-Level Nuclear Waste Disposal
Authors: Williams Jeffrey D.
Published: June 2019

Increased concern by the State of South Carolina over the condition and capacity of the low-level radioactive waste burial site at Barnwell has prompted them to promulgate new regulations on waste burial containers. As of September 30, 1981, ion exchange resin and filter media waste with an activity of 1 μCi/cc or greater and with isotopes with halflives greater than five years disposed at Barnwell shall be solidified or confined in a “high integrity container”. The materials and designs of these containers are required to provide waste isolation from the environment for a period of 300 years and provide the structural integrity specified in 49 CFR 173.398(b). HITTMAN has been active in the design and development of containers suitable for this purpose with this paper detailing the analyses involved. Material selections were limited to stainless steel, fiberglass, and polyethylenes. Structural concerns focused on overpressure requirements, drop-testing requirements, and lifting capabilities. With a lifetime dose of up to 108 rads, the possibilities of radiation damage were considered. Preliminary selection of polyethylene was based on satisfactory resolution of these issues and economic factors.
A New Poly-Si CMP Process with Small Erosion for Advanced Trench Isolation Process
Authors: Miyashita Naoto , Uekusa Shin-ichiro , Nishioka Takeshi , Iwami Satoko
Published: June 2019

Chemical-Mechanical Polishing has been revealed as an attractive technique for poly-Si of trench planalization. Major issue of the process integration is pattern erosion after over polishing. A new process with silica slurry containing organic surfactant is reported in this paper. A patterned wafer after conventional CMP process is eroded by over polishing, however, the new process conducts small erosion for wide trenches. The organic surfactant is well known as a inhibitor for the protection of poly-Si from alkaline, and the new slurry shows a large pH dependency of the viscosity. The experimental work has been focused on the viscosity, and the mechanism of the small erosion is discussed. This new process should be useful for recessing poly-Si by CMP, because it keeps the erosion level very low.
Pattern Formation in Thin Polymer Films: A New Morphology
Authors: Masson Jean-Loup , Green Peter F.
Published: June 2019

Researchers have shown that thin, nonwetting, liquid homopolymer films dewet substrates, forming patterns that reflect fluctuations in the local film thickness. These patterns have been shown to be either discrete cylindrical holes or bicontinuous “spinodal-like” patterns. In this paper we show the existence of a new morphology. During the early stage of dewetting, discrete highly asymmetric holes appear spontaneously throughout the film. The nucleation rate of these holes is faster than their growth rate. The morphology of the late stage of evolution, after 18 days, is characterized by a bicontinuous pattern, distinct form conventional spinodal dewetting patterns. This morphology has been observed for a range of film thicknesses between 7.5 and 21nm. The structural evolution of this intermediate morphology is discussed.
Amine-Quinone Polyimides as Coatings that Protect Iron Against Corrosion.
Authors: Han Mijeong , Bie Huimin , Warren Garry W. , Nikles David E.
Published: June 2019

A new diamine monomer was synthesized by condensing 4,4'-methylene dianiline with 1,4-benzoquinone. The monomer was condensed with 3,3',4,4'-benzophenone tetracarboxylic dianhydride to give a polyamic acid that was soluble in N-methyl-2-pyrrolidinone. The polyamic acid was cast onto iron and thermally imidized to give the amine-quinone polyimide (AQPI-2). AQPI-2 had a thermal decomposition temperature (10% weight loss) of 540°C and a glass transition near 290°C, values typical of polyimides. The degradation of the coating on iron after exposure to NaCl electrolyte was followed by electrochemical impedance spectroscopy. Under these conditions a conventional polyimide failed after 3 days exposure, while AQPI-2 showed no change after 34 days exposure. The adhesive bond between the amine-quinone polyimide and the iron surface was so strong that it could not be broken by the electrolyte.
Solid-State Blending of Polymers by Cryogenic Mechanical Alloying
Authors: Smith Archie P. , Ade Harald , Koch Carl C. , Spontak Richard J.
Published: June 2019

Cryogenic mechanical alloying has been employed to blend poly(methyl methacrylate) (PMMA) with up to 25 wt% polyisoprene (PI) and poly(ethylene-alt-propylene) (PEP). Mechanical milling of the individual polymers reveals that their molecular and bulk properties depend sensitively on milling time, post-annealing and, for PMMA, temperature. Characterization of the as-milled blends by scanning transmission x-ray microscopy and transmission electron microscopy has demonstrated intimate (nanoscale) dispersions within the blends, with the degree of mixing increasing with increasing milling time. Phase domains as small as 10 nm are observed after alloying for 10 h. Post-annealing of the blends above the Tgof PMMA (which depends on milling time) induces morphological changes, which differ for blends containing PI and PEP. In blends composed of PEP, the fine dispersions gained as a result of milling are largely compromised. Conversely, PI crosslinking hinders molecular mobility so that the milling-induced nanoscale dispersions of PI in PMMA are, for the most part, retained even after long-term annealing at elevated temperatures.
Measuring Interface Strength in Single Fiber Composites: The Effect of Stress Concentrations
Authors: Holmes G. A. , Peterson R. C.
Published: June 2019

Fiber-matrix interface strength is known to be a critical factor in controlling the long-term performance of structural composites. This parameter is often obtained by using the average fragment length data generated from the single-fiber fragmentation test (SFFT). The interfacial shear strength is then determined by using this data in a micro-mechanics model that describes the shear-stress transfer process between the matrix and the fiber. Recently, a non-linear viscoelastic micro-mechanics model was developed to more accurately account for the matrix material properties. This new model indicates that the interface strength is dependent on the testing rate. Experimentally, it has been shown that the final fragment length distribution in some systems is dependent on the testing rate. However, data analysis using the new model indicates that the distribution change with testing rate is promoted by the presence of high stress concentrations at the end of the fiber fragments. From the model, these stress concentrations were found to exist at very low strain values. Experimentally, the fragment distributions obtained from specimens tested by different testing rates were found to be significantly different at strain values well below the strain values required to complete the test. These results are consistent with the research of Jahankhani and Galiotis and finite element calculations performed by Carrara and McGarry. These authors concluded that stress concentrations can promote failure of the fiber-matrix interface on the molecular level. Our results support this conclusion. In addition, our research results suggest that altering the SFFT testing rate can lower the magnitude of these stress concentrations and minimize failure of the fiber-matrix interface.
Surface Modification of Poly (alkyl/Arylphosphazene) Thin Films
Authors: John John V. St. , Wisian-Neilson Patty
Published: June 2019

Poly (methylphenylphosphazene) (PMPP) is an example of a unique class of inorganic polymers with alternating – (P=N)– backbones. Chemical modification of bulk PMPP can result in changes of physical properties such as chemical resistance, onset temperature of thermal degradation, elasticity, and flexibility. Surface modification of PMPP allows tailoring of the chemical properties at the polymer interface while maintaining the integrity of the bulk polymer. In this research, PMPP thin films were treated to form carboxylate or carboxylic acid groups at the surface. Surface modification was monitored by following changes in contact angle. The hydrophobic/hydrophilic interactions of carboxylated PMPP surfaces allow for mesoscale interactions of thin polymer films.
Radiation Enhanced Porosity and Roughness of Biomaterials
Authors: Evelyn A. L. , Rodrigues M. G. , Ila D. , Zimmerman R. L. , Poker D. B. , Hensley D. K.
Published: June 2019

Glassy Polymeric Carbon (GPC), made from cured phenolic resins, is sufficiently chemically inert and biocompatible that it is suitable for medical applications, such as heart valves and other prosthetic devices. We have used energetic ion bombardment of the partially and fully cured precursor phenolic resins to enhance biological cell/tissue growth on, and to increase tissue adhesion to, prosthetic devices made from GPC. GPC samples were bombarded with energetic ions to 10 MeV. The surface topography and increased surface roughness was observed using optical microscopy and atomic force microscopy (AFM). The increased porosity was measured by introducing lithium from a molten LiCl salt into the GPC and using (p, α) nuclear reaction analysis (NRA) to measure the concentration of Li retention in the modified GPC. The NRA measurements of increased pore availability were correlated with the observations of increased surface roughness.
Microcellular Polymeric Foams (MPFs) Generated Continuously in Supercritical Carbon Dioxide
Authors: Siripurapu Srinivas , Gay Yvon J. , Royer Joseph R. , DeSimone Joseph M. , Khan Saad A. , Spontak Richard J.
Published: June 2019

Microcellular polymeric foams (MPFs) hold tremendous promise for engineering applications as substitutes to their solid analogs in light of reduced manufacturing/materials costs and improved properties. We present a two-part study addressing the generation of such materials in the presence of supercritical carbon dioxide (scCO2). The first part describes the production of polystyrene MPFs in a continuous extrusion process, as well as the effect of operating conditions such as temperature and CO2 concentration on foam morphology. The second part discusses microcellular foaming of poly (vinylidene fluoride) (PVDF), a semicrystalline polymer, via blending with the amorphous polymer poly (methyl methacrylate) PMMA. Foams of pure PVDF possess ill-defined morphologies, whereas those of PVDF-PMMA blends show an improvement with cell sizes on the order of 10 mm or less and cell densities in excess of 109 cells/cm3.
Avalanches As Failure Percursors
Authors: ROUX Stéphane
Published: June 2019

There exists basically two types of failure scenario: Either "brittle" where failure takes place suddenly without any sign which could help to anticipate over the failure, or "controlled" where the development of failure is progressive.
An Improved Magnetic Technique For The Non-Destructive Detection Of Faults In Embedded Steel Reinforcement
Authors: Haycock Peter W. , Brown Simon D. , Tomlinson Nicholas , Hocking Matthew J.
Published: June 2019

There are many situations in which steel reinforcement within structural materials is vulnerable to corrosion. In some cases the result of such deterioration of the structural integrity can have significant safety implications. However, there is currently little by way of reliable non-destructive means of obtaining direct evaluation of the state of the embedded steel, which yields anything more than rudimentary information. This paper considers the possibilities of making use of the vectorial nature of the magnetization of steel to improve the qualitative and quantitative evaluation of the integrity of embedded steel reinforcement in vehicle tyres. Results are presented which show that enhanced non-destructive mapping of faults within tyres can be achieved by this means.
Study of Natural Minerals of U-Ryrochlore-Type Structure as Analogues of Plutonium Ceramic Waste-form
Authors: Bogdanov Roman V. , Batrakov Yuri F. , Puchkova Elena V. , Sergeev Andrey S. , Burakov Boris E.
Published: June 2019

At present, crystalline ceramic based on titanate pyrochlore, (Ca,Gd,Hf,Pu,U)2Ti2O7, is considered as the US candidate waste form for the immobilization of weapons grade plutonium. Naturally occuring U-bearing minerals with pyrochlore-type structure: hatchettolite, betafite, and ellsworthite, were studied in orders to understand long-term radiation damage effects in Pu ceramic waste forms. Chemical shifts (δ) of U(Lδ1)– and U(Lβ1) – X-ray emission lines were measured by X-ray spectrometry. Calculations were performed on the basis of a two-dimensional δLá1- and δLδ1- correlation diagram. It was shown that 100% of uranium in hatchettolite and, probably, 95-100% of uranium in betafite are in the form of (UO2)2+. formal calculation shows that in ellsworthite only 20% of uranium is in the form of U4+ and 80% of the rest is in the forms of U5+ and U6+. The conversion of the initial U4+ ion originally occurring in the pyrochlore structure of natural minerals to (UO2)2+ due to metamict decay causes a significant increase in uranium mobility.
Dry Patterning of Cu(Mg) Alloy Films Using a Self-Aligned MgO Mask In an Oxygen Plasma Plus H(hfac) Chemistry
Authors: Yang Heejung , Ko Yeonkyu , Lee Jaegab
Published: June 2019

A self-aligned surface MgO layer was used as a mask for dry etching the Cu(Mg) alloy films using an O2 plasma and H(hfac) chemistry. The surface MgO layer was formed by diffusion of Mg from Cu film to the free surface. Cu(4.5at%Mg) film having thickness of 300nm was annealed in O2 ambient at 10 mTorr, 500°C for 30min, followed by the patterning of the MgO layer using photolithography and HF wet etch process. The patterned MgO layer successfully served as a hard mask for dry etching the Cu(Mg) alloy films with a taper slope. In addition, the high quality self-aligned MgO layer was formed upon annealing the Cu(4.5 at.% Mg) alloy films at the low temperature of 300°C. Furthermore, the surface MgO layer grown on Cu(2.3at.% Mg) alloy films at 500°C withstood as a hard mask for dry etching, and thus achieving the patterned copper alloy lines with the low resistivity of 2.2 μΩ-cm. Consequently, this novel etch process using a self-aligned MgO mask can be used for patterning the low resistivity copper alloy lines with a low thermal budget, which is suitable for large-size TFT-LCDs.
Laser Thermal Processing of Alternate Dopants in Silicon
Authors: Clark Mark H. , Jones Kevin S. , Rendon Michael , Gable Kevin A.
Published: June 2019

Traditionally, the choice of dopant has been limited to those species with the highest solid-solubility, however, Laser Thermal Processing (LTP) is not fundamentally limited by solid-solubility. Therefore, it is of interest to evaluate alternate dopants that have previously been excluded due to low solid-solubility. To this end, alternate dopants of 14N, 121Sb (n-type), 27Al, 70Ga, and 115In (p-type) are compared to conventional dopants of As and B respectively, after LTP and post-LTP thermal processing. Dopants were implanted into <100> silicon wafers of opposite background doping type that had previously been amorphized to a depth of approximately 300 angstroms by a 15 keV 28Si+ implant of 1x1015/cm2 dose. An implant energy of 5 keV was sufficiently low to confine the implanted ions to the amorphous layer, with the exception of B, which required an energy of 2 keV. All species were implanted at doses of 1x1014, 5x1014 and 1.5x1015/cm2. Samples were LTP utilizing a 308 nm, 18 ns laser pulse with a fluence of 0.680 J/cm2. Post-LTP thermal processing of the samples consisted of a 900 °C rapid thermal anneal (RTA) in a nitrogen ambient for a duration ranging from spike to 300 seconds. Measurements of the sheet resistance, mobility and carrier concentration were taken after both LTP, and the post-LTP thermal processing. Experimental results show that LTP of alternate dopants increases the electrically active carrier concentration of Ga, Al and Sb above solid-solubility. Additionally, the amount of deactivation upon post- LTP thermal processing depends on the alternate dopant species.
Electromagnetic Induction Heating for the 70 nm Node
Authors: Thompson Keith , Booske John H. , Cooper R.F. , Gianchandani Y.B.
Published: June 2019

Electromagnetic heating provides a novel alternative to “illumination-based” rapid thermal processing techniques. Exposure to radiation, in the RF and microwave frequency regimes, rapidly heats silicon (∼125°C/sec) to temperatures in excess of 1000°C without the use of a susceptor. These ramp rates make this technology suitable for the activation of shallow implanted dopants, and satisfaction of the 100 nm technology node has been achieved. Furthermore, the presence of high frequency electric fields creates ponderomotive forces that may alter the kinetics of dopant activation and diffusion. These additional driving forces could, once fully understood, lead to an enhanced activation mechanism that activates sufficient dopants to satisfy the 70 nm technology node at temperatures less than 1000°C.
Thermal Stability and Substitutional Carbon Incorporation far above Solid-Solubility in Si1-xCx and Si1-x-yGexCy Layers Grown by Chemical Vapor Deposition using Disilane
Authors: Carroll M. S. , Sturm J. C.
Published: June 2019

Growth conditions for epitaxy of Si1-x-yGexCx and Si1-xCx alloy layers on (100) silicon substrates by rapid thermal chemical vapor deposition (RTCVD) with disilane as the silicon source gas are described and the Si1-xCx conditions are compared to previously reported RTCVD growth conditions for epitaxy of Si1-xCx using silane as the source gas. The thermal stability of the layers at 850°C in nitrogen is examined using x-ray diffraction as a measure of the average substitutional carbon concentration in the layers after annealing. A characteristic time constant to describe the reduction of average substitutional carbon concentration in the layer is extracted from the XRD measurements. The characteristic time constants are found to agree within a factor of 3 with that observed in previous reports. However, the time constants are found to depend more strongly on the as-grown substitutional carbon concentration than what is predicted by simple precipitation kinetics, assuming carbon diffusion to a constant number of nucleation centers.
Non-routine Dopant, Impurity and Stoichiometry Characterization of SiGe, SiON and Ultra-low Energy B-implanted Si Using Secondary Ion Mass Spectrometry
Authors: Magee Charles W. , Buyuklimanli Temel H. , Marino John W. , Novak Steven W. , Sahiner M. Alper
Published: June 2019

New, non-routine metrology issues are addressed for three kinds of materials and processes that are necessary for the fabrication of ultra-high speed devices. We look at the problems and solutions for measuring both stoichiometry and dopant content of SiGe material when using Cs primary ion bombardment. We examine the challenges of determining the N content of ultra-thin SiON gate dielectrics with emphasis on what will be necessary for the measurement of 1nm thick oxides. And finally we show some promising early results of using a new protocol for measuring ULE B ion implant profiles in the top 3nm with emphasis on obtaining a more realist profile shape in this region for TCAD modeling purposes.
Calibration of Phosphorus Implantation Dose in Silicon by Radiochemical Neutron Activation Analysis
Authors: Paul Rick L. , Simons David S.
Published: June 2019

A radiochemical neutron activation analysis (RNAA) procedure has been developed, critically evaluated, and shown to have the necessary sensitivity, chemical specificity, and matrix independence to certify phosphorus at ion implantation levels. 32P, produced by neutron capture of 31P, is chemically separated from the sample matrix, and measured using a beta proportional counter. Analysis of 12 pieces of a silicon wafer, implanted at a nominal dose of 8.5 x 1014 atoms·cm-2, yielded a phosphorus concentration of (8.30 ± 0.16) x 1014 atoms·cm-2 (expanded uncertainty), in agreement with a consensus value of (8.23 ± 0.33) x 1014 atoms·cm-2 (1s uncertainty) determined from a round robin SIMS investigation. The relative standard deviation of < 2 % is suitable for certification of a Standard Reference Material.
Microstructural and Electrical Characterization of Barium Strontium Titanatebased Solid Solution Thin Films Deposited on Ceramic Substrates by Pulsed Laser Deposition
Authors: Fountzoulas Costas G. , Potrepka Daniel M. , Tidrow Steven C.
Published: June 2019

Ferroelectrics are multicomponent materials with a wealth of interesting and useful properties, such as piezoelectricity. The dielectric constant of the BSTO ferroelectrics can be changed by applying an electric field. Variable dielectric constant results in a change in phase velocity in the device allowing it to be tuned in real time for a particular application. The microstructure of the film influences the electronic properties which in turn influences the performance of the film. Ba0.6Sr0.4Ti1-y(A 3+, B5+)yO3 thin films, of nominal thickness of 0.65 μm, were synthesized initially at substrate temperatures of 400°C, and subsequently annealed to 750°C, on LaAlO3 (100) substrates, previously coated with LaSrCoO conductive buffer layer, using the pulsed laser deposition technique. The microstructural and physical characteristics of the postannealed thin films have been studied using x-ray diffraction, scanning electron microscopy, and nano indentation and are reported. Results of capacitance measurements are used to obtain dielectric constant and tunability in the paraelectric (T>Tc) regime.
Electrically Tunable Phase Shifters With Air-Dielectric Sandwich Structure
Authors: Jeong Minki , Kazmirenko Victor , Poplavko Yuriy , Kim Beomjin , Baik Sunggi
Published: June 2019

Electrically tunable microwave phase shifter was developed by inserting dielectric slab and piezoelectric actuator inside a waveguide. Air-dielectric sandwich structure of dielectric material and thin air gap was placed inside a waveguide, where the thickness of air gap is controlled by the actuator. Small changes in the ratio between the thickness of dielectric material and air gap induce significant changes in the effective dielectric constant of the air-dielectric sandwich structure. Phase shifts of 20∼200 degrees were realized with the dielectric materials such as (Mg, Ca)TiO3 while the thickness of air gap is changed between 0 to 30 μm by piezoelectric control. Since the dielectric ceramics has very small loss (tand ∼ 10-4) and the air gap has practically no loss, the total structure shows low insertion loss.
Deposition of Polycrystalline ZnO Films by Two-Step Method and Characterization of Thermal Annealing Effects
Authors: Lee Jin-Bock , Lee Myung-Ho , Lee Hye-Jung , Park Jin-Seok
Published: June 2019

Polycrystalline ZnO thin films were deposited on SiO2/Si(100) substrate using RF magnetron sputtering. The film deposition performed in this work was composed of following two procedures; the 1st-deposition for 30 min without oxygen at 100 W and the 2nd-deposition with oxygen in the range O2/(Ar+O2) = 10∼50 %. Deposited ZnO films revealed a strongly c-axis preferred-orientation (the corresponding texture coefficient ∼ 100 %) as well as a high resistivity (> 107 Ωcm). It was also observed that the crystallite size of ZnO was noticeably increased by thermal-annealing.
On the GHz Frequency Response in Nanocrystalline FeXN Ultra-Soft Magnetic Films
Authors: Chechenin N.G. , Craus C.B. , Chezan A.R. , Vystavel T. , Boerma D.O. , Hosson J.Th. M. De , Niesen L.
Published: June 2019

The periodicity and angular spread of the in-plane magnetization for ultrasoft nanocrystalline FeZrN films were estimated from an analysis of the ripple structure, observed in Lorentz transmission electron microscopy (LTEM) images. The influence of the micromagnetic ripple on the ferromagnetic resonance (FMR) width is analyzed using an approach based on the Landau-Lifshitz equation. A strong dependence of the resonance width on the magnetic moment dispersion is predicted. To a large extent this particular aspect explains the high frequency response in some of our films.
Microwave Dielectric Spectroscopy of Ferroelectric Thin Films
Authors: Kim Beomjin , Kazmirenko Victor , Jeong Minki , Poplavko Yuri , Baik Sunggi
Published: June 2019

We devised a measurement method of microwave dielectric constants of dielectric thin films without applying electrodes. The method uses a rectangular waveguide in which the dielectric thin films prepared on a substrate are filled vertically at the center. The frequency dependence of S-parameter measured by network analyzer enables us to calculate the dielectric constant and loss factor of the films at the microwave region through simulation. We prepared Ba0.6Sr0.4TiO3 thin films on (001) MgO single crystal substrate by pulsed laser deposition (PLD), and determined their dielectric constant and loss factor at ∼10GHz using this method.
Synthesis of Nanostructured Magnetic Mixed-Oxide Ferrite Powders by Using A Novel Chemical Method
Authors: Ghosh N N
Published: June 2019

In the present investigation, an attempt has been made to establish a new chemical route for synthesis of the nanostructured mixed oxide ferrite powders. By using this chemical method a variety of ferrite powders having spinel structure and doped with Co, Ni, Mn, Zn etc has been prepared. In this method nitrate salts of the different metals were used as starting materials. The aqueous solutions of the metal nitrates were mixed according to the molar ration of the compositions. Then the mixtures were mixed with an aqueous solution of water soluble polymer (polyvinyl alcohol). This mixture after drying yield fluffy brown powders. These powders were then calcined at different temperatures ranging from 400 °C to 700 °C. Nanostructured powders were obtained from the thermal decomposition of the brown powders. The powders, prepared by calcinations at different temperatures, were characterized by using X-Ray diffraction analysis, IR spectroscopy, TGA/DTA, and TEM. It was observed that the average particle size of the powders are in nanometer scale with a narrow size distribution. The average particle size of the powders was increased with the increase of calcinations temperature.

This chemical method has proved to provide a convenient process for the preparation of nanostructured ceramic powders at comparatively low temperatures and offers the potential of being a simple and cost-effective route.
The Effects of Plasma Induced Damage on The Channel Layers of Ion Implanted GaAs MESFETs during Reactive Ion Etching(RIE) and Plasma Ashing Processes
Authors: Ahn Hokyun , Ji Honggu , Mun Jaekyoung , Park Min , Kim Haecheon
Published: June 2019

The gate length of GaAs MESFETs is required to be shorter for higher microwave frequency applications. The side-wall process using silicon nitride is one of the effective processes to fabricate short gate length GaAs MESFETs. The side-wall process consists of deposition and anisotropic etching of silicon nitride and delivers plasma induced damages on the channel layers of the devices. In this study, the effects of plasma induced damage on the channel layers of ion implanted GaAs MESFETs during reactive ion etching and plasma ashing processes have been investigated. The plasma induced damage was characterized by sheet resistance measurement, Xray photoelectron spectroscopy(XPS) and auger electron spectroscopy(AES) of different etched surfaces, compared with a chemically wet-etched reference surface. Also the effect of the plasma induced damage on the device performance was investigated. As a result, plasma ashing can deteriorate the plasma-induced damage by RIE.
RF Sputtered BZN Pyrochlore Thin Films for Voltage Tunable Dielectric Device Applications
Authors: Hong Young Pyo , Ha Seok , Lee Ha Yong , Lee Young Cheol , Ko Kyung Hyun , Kim Dong Wan , Hong Hee Bum , Hong Kug Sun
Published: June 2019

The BZN pyrochlore thin films were prepared on platinized Si substrates using a reactive RF magnetron sputtering. The structures, surface morphologies, dielectric properties and voltage tunable properties of films with deposition parameters were investigated. The BZN thin films have a cubic pyrochlore phase and secondary phases of zinc niobate, bismuth niobate when crystallized at 600° 800°. The dielectric constant and tunability of thin films are O2/Ar ratio and post-annealing temperature dependent. The BZN thin films sputtered in 15% O2 and annealed at 700° had a dielectric constant of 153, tan δof~0.003 and maximum tunability of 14% at 1,000kV/cm.
Correlation of Microwave Dielectric Properties and Microstructure of Unpatterned Ferroelectric Thin Films
Authors: Geyer R. G. , Cole M.W. , Joshi P.C. , Ngo E. , Hubbard C. , Nothwang W. , Bratcher M. , Ervin M. , Wood M.
Published: June 2019

The influence of low concentration (1 mol%) Mg doping on the structural, microstructural, surface morphological and dielectric properties of Ba1-xSrxTiO3 thin films has been measured and analyzed. The films were fabricated on MgO and Pt-Si substrates via the metalorganic solution deposition technique using carboxylate-alkoxide precursors and post deposition annealed at 800 °C (film/MgO substrates) and 750 °C (film/Pt-Si substrates). The structure, microstructure, surface morphology and film/substrate compositional quality were analyzed and correlated to the films dielectric and insulating properties. Dielectric properties of unpatterned films were measured at 10 GHz with a coupled/split dielectric resonator system and at 100 kHz using metal-insulator-metal capacitors. The Mg-doped BST films exhibited improved dielectric loss and insulating characteristics compared to the undoped Ba0.6Sr0.4TiO3 thin films. The improved dielectric properties, low leakage current, and good tunability of the low level Mgdoped BST thin films merit strong potential for utilization in microwave tunable devices.