bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon Film Deposition On Silicon Using Low Energy Ion Beams
Authors: Fuguang Qin , Zhenyu Yao , Zhizhang Ren , Lee S.-T. , Bello I. , Feng X , Huang L. J. , Lau W. M.
Published: June 2019

Direct ion beam deposition of carbon films on silicon in the ion energy range of 15–500eV and temperature range of 25–800°C has been studied using mass selected C+ ions under ultrahigh vacuum. The films were characterized with X-ray photoelectron spectroscopy, Raman spectroscopy, and transmission electron microscopy and diffraction analysis. Films deposited at room temperature consist mainly of amorphous carbon. Deposition at a higher temperature, or post-implantation annealing leads to formation of microcrystalline graphite. A deposition temperature above 800°C favors the formation of microcrystalline graphite with a preferred orientation in the (0001) direction. No evidence of diamond formation was observed in these films.
Optical Spectroscopic Profiling of Ion Beam Sputtering
Authors: Klein J. D. , Yen A.
Published: June 2019

The optical emission spectra resulting from ion beam sputtering a BaTiO3 target were observed as a function of position. A collimated optical fiber bundle parallel to the plane of the sputter target was translated vertically and horizontally to spectroscopically profile the sputter process. The Ar contours provide an image of the incident beam and its distortion by the presence of the target. Comparison of the Ar and O contours indicate that the oxygen atmosphere in the vicinity of the target is determined by sputtering events as well as the incident beam. The shapes of the Ba and Ti contours are elliptical with some differences in intensity gradients. Comparison is made with species contours observed during rf sputtering of an Y-Ba-Cu-O target.
Ion/Neutral Beam Assisted Etching of Semiconductors: Chemical Modifications of the Adsorbed Phase
Authors: Tyrrell Glenn. C. , Marshall Duncan , Jackman Richard B.
Published: June 2019

This paper addresses the fundamental aspects of etching semiconductors with inert gas beams in the presence of a suitable precursor gas. In particular, the changes that an energetic bombarding ion/neutral species cause to the surface and sub-surface region of a solid are considered, both in terms of the introduction of damage to the semiconductor and chemical processes that are provoked in the adsorbed states present. The implications for practical etching reactions are then discussed.
Stoichiometric Determination of Graphite Intercalation Compounds Using Rutherford Backscatiering Spectrometry
Authors: Salamanca-Riba L. , Elman B.S. , Dresselhaus M.S. , Venkatesan T.
Published: June 2019

Rutherford backscattering spectrometry (RBS) is used to characterize the stoichiometry of graphite intercalation compounds (GIC). Specific application is made to several stages of different donor and acceptor compounds and to commensurate and incommensurate intercalants. A deviation from the theoretical stoichiometry is measured for most of the compounds using this non-destructive method. Within experimental error, the RBS results agree with those obtained from analysis of the (00ℓ) x-ray diffractograms and weight uptake measurements on the same samples.
Patterned Sol-Gel Structures by Micro Molding in Capillaries
Authors: Lochhead M. J. , Yager P.
Published: June 2019

The development of a variety of micro-optical chemical sensor and biosensor devices will rely on an ability to fabricate and effectively pattern physically and chemically sensitive materials. Toward this end, organically modified sol-gel materials are patterned onto a substrate using a benign technique called micro molding in capillaries (MIMIC). Closely spaced, organically modified silica ridges containing organic dyes are demonstrated. The mold consists of a micro channel-filled elastomeric master in contact with a glass substrate. Liquid sols fill the mold as a result of capillary action. A reservoir-channel system in the mold allows simultaneous casting of sols with different chemical compositions. After gelation, the elastomeric master is removed and sol-gel structures are left on the substrate. Cross-sectional dimensions of the ridges range from one to tens of micrometers, and can be centimeters in length. Because of the mild processing conditions, the method is especially attractive for solgel materials containing sensitive molecules such as indicator dyes and biomolecules. The technique holds promise for microfabricated sensor and integrated optics applications.
Optical Waveguiding (Pb, La)(Zr,Ti)O3 Thin Films Prepared by Pulsed Laser Deposition
Authors: Xiong S. B. , Liu Z. G. , Chen X. Y. , Guo X. L. , Yu T. , Zhu S. N. , Liu X. , Luo W. G.
Published: June 2019

The ferroelectric (Pb, La) (Zr,Ti)03 (PLZT(9.4/65/35)) optical waveguiding thin films have been prepared on SiO2 coated Si and on silica glass substrates by pulsed laser deposition. X-ray θ–2θ scans revealed that the films are single-phase pseudo-cubic perovskite. The surface chemical composition of the as grown films were determined by XPS. The ferroelectric properties of the films as grown on Pt/Ti coated silicon were demonstrated by using a modified Sawyer-Tower circuit, and the optical waveguiding properties of the films were characterized by using a rutile prism coupling method. The as grown films have an average transmittance of 80% in the wavelength range of 400˜2000nm and a refractive index of 2.2 at 632.8mn close to the bulk PLZT. The distinct m-lines of the guided TM and TE modes of the films as grown on SiO2 coated Si substrates have been observed.
A Low Temperature Direct Bonding Method Using an Electron-Beam Evaporated Silicon-Oxide Interlayer
Authors: Park H. W. , Ju B. K. , Lee Y. H. , Park J. H. , Lee N. Y. , Koh K. H. , Shin D. K. , Kang I. B. , Samaan N. , Haskard M. R. , Oh M. H.
Published: June 2019

In this work, we proposed a direct bonding method using interlayers for single crystalline silicon wafers and glass wafers. Various materials were used for interlayers of thermal oxide, sputtered nitride, electron-beam(E-beam) evaporated silicon oxide and molybdenum. After hydrophilization, samples were spin dried and mated together without external forces. Three types of solutions were used for hydrophilizing the samples. Changes of average surface roughness after hydrophilization of the single crystalline silicon wafer, thermal oxide and E-beam silicon-oxide were inspected using atomic force microscope(AFM). Bonding interfaces of the bonded pairs were observed by scanning electron microscope(SEM). Voids and non-contact areas of the bonding pairs were also inspected using infrared(IR) transmission microscope. Surface energy, tensile strength measurements and breaking tests were also done.
Micro-Raman Study of Stress Distribution and Thermal Relaxation of Oxidized Silicon Membranes
Authors: Malhaire C. , Guyot Y. , Berre M. Le , Champagnonn B. , Sibai A. , Barbier D.
Published: June 2019

Composite SiO2/Si membranes are used in various type of sensors among them, resonant and pressure sensors. However due to a large thermal mismatch, residual induced stresses may affect the devices long term reliability especially for thin membranes (˜5 μm). In this study, we have characterized test structures consisting of SiO2/Si membranes with respective thickness ratio between 2 and 10. Micro-Raman Spectroscopy, well known to be an accurate, non destructive method to determine residual stresses in microelectronic devices, has shown to be a powerful testing technique to measure local stresses on micromachined structures such as membranes, with a high spatial (10 μm2 ) and stress resolution (8 MPa). At room temperature, Raman line (520 cm−1) shifts between 0.05 and 1 cm−1 are observed. Highest frequency shifts of 1cm−1 corresponds to a 230 MPa biaxial stress. Finite Element analysis (ANSYS) was used to model the thermal stress distribution over the micromachined bilayer membrane, yielding a satisfactorily agreement with the experimental results over a large membrane area. The Finite Element analysis was correlated with optical profilometer deflection measurements. Membrane deflections up to 48 μm (more than 10 times the membrane thickness) have been measured. Furthermore, Micro-Raman Spectroscopy results up to 300°C are shown and related to temperature dependent deflection measurements.
Mechanical Behavior of a Mems Acoustic Emission Sensor
Authors: Bahr D. F. , Wright J. S. , Francis L. F. , Moody N. R. , Gerberich W. W.
Published: June 2019

The elastic modulus and hardness of materials used in a MEMS acoustic emission sensor were determined using nanoindentation techniques. In addition to testing each individual material, the behavior of four candidate bottom electrode structures, two based on nitride layers and two based on oxide layers, have been evaluated. The multilayer nitride bottom electrode is relatively unaffected by a 950 °C annealing step; however, some evidence of second phase formation in the polycrystalline silicon layer has been observed. Increasing the thickness of the thermally grown silicon dioxide in the oxide based electrodes lowers the measured hardness of the top layer of platinum while increasing the measured modulus of the entire electrode at depths corresponding to the oxide film. Errors of up to 25% in the calculated area of indentation based on the indenter shape function occur for indentations which penetrate both the platinum and oxide films.
Development of a Micromirror Using Piezoelectric Excited and Actuated Structures
Authors: Maeda R. , Lee C. , Schroth A.
Published: June 2019

The design and fabrication process of a micro-mirror device is presented. The device is driven by sol-gel deposited PZT-layer actuators. The mirror is designed to be able to carry out scanning in two lateral directions, and additionally movement in vertical direction using a FEMsimulation tool. The established fabrication process is described.
Piezoelectric Force Sensing Pb(Zr,Ti)O3 Microcantilever Array for Multiprobe Scanning Force Microscopy
Authors: Itoh T. , Lee C. , Chu J. , Suga T.
Published: June 2019

This paper reports on a multiprobe scanning force microscope (SFM) utilizing an array of individually controlled piezoelectric Pb(Zr,Ti)O3 (PZT) microcantilevers. Each cantilever is unimorph beam including a sol-gel derived PZT thin film that has high piezoelectric constants in comparison with sputtered ZnO films. The cantilever is excited and actuated in z direction by applying ac and feedback dc voltages to the PZT layer. The variation of vibration amplitude is detected by measuring the change of current through the PZT layer. The 200-μm-long PZT microcantilever with the natural resonance frequency of 63.8 kHz has the high actuation sensitivity of 150 nmN and the maximum range of more than 1.5 μm. By actuating the self-excited cantilever to keep the current constant, we have succeeded in independent dynamic operation without z feedback actuation of the sample-side scanner. We have obtained independent parallel 2 × 1 images using two cantilevers of the array.
Elastic Properties of Diamond Like Carbon Thin Films: a Brillouin Scattering Study
Authors: Monteiro O. R. , Brown I. G. , Sooryakumar R. , Chirita M.
Published: June 2019

Diamondlike carbon (DLC) thin films have been widely used as hard coatings in a variety of applications where increased wear resistance and hardness are required. Vacuum arc DLC films are among the hardest, with measured hardness values of up to 68 GPa. In our deposition process a repetitively pulsed bias voltage is applied to the substrate, which controls the energy of the incoming C ions. DLC chemical and mechanical properties are strongly affected by the energy of the depositing ions. In this paper, we relate the mechanical properties of these films to the deposition parameters, and describe our initial Brillouin scattering measurements of the elastic constants of monolithic DLC films. Evidence for bulk longitudinal and surface Rayleigh excitation in films with thickness of 50 and 500 nm has been observed. Since the DLC films are amorphous, they are modeled as isotropic solids and the elastic constants CII and C44 are derived.
Surface Treatment with UV-Excited Radicals for Highly-Reliable Gate Dielectrics
Authors: Ito Takashi , Sugino Rinji , Nakanishi Toshiro , Ohkubo Satoshi , Tamura Yasuyuki , Takasaki Kanetake
Published: June 2019

The UV-excited chlorine radical treatment effectively removed trace metal contaminants from Si ans SiO2 surfaces. We have found that this is predomonantly attributed to reactions between metal and chlorine, and metal oxides and silicon chloride, respectively. The former process was subjected to identify a breakdown spot on a thin gate dielectric film. After dielectric breakdown, a silicon crystallized filament as small as a few nanometers in diameter was formed and was selectively etched with chlorine radicals revealing a successively-etched region of the Si substrate. Nonuniformi t i es of native oxides on silicon were also detected using the same method. Gettering and etching with a poly Si layer showed a possibility to make a gate dielectric film damage free and contamination free. Densi fication of native oxides formed after conventional wet cleaning of silicon was made with UV-excited oxygen radicals. Electrical characteristics of gate dielectrics treated with UV-excited chlorine and oxygen radicals showed high reliability.
Progressive Debonding of Multilayer Interconnect Structures
Authors: Lane Michael , Ware Robert , Voss Steven , Ma Qing , Fujimoto Harry , Dauskardt Reinhold H.
Published: June 2019

Progressive (or time dependent) debonding of interfaces poses serious problems in interconnect structures involving multilayer thin films stacks. The existence of such subcriticai debonding associated with environmentally assisted crack-growth processes is examined for a TiN/SiO2 interface commonly encountered in interconnect structures. The rate of debond extension is found to be sensitive to the mechanical driving force as well as the interface morphology, chemistry, and yielding of adjacent ductile layers. In order to investigate the effect of interconnect structure, particularly the effect of an adjacent ductile Al-Cu layer, on subcriticai debonding along the TiN/SiO2 interface, a set of samples was prepared with Al-Cu layer thicknesses varying from 0.2–4.0 μm. All other processing conditions remained the same over the entire sample run. Results showed that for a given crack growth velocity, the debond driving force scaled with Al-Cu layer thickness. Normalizing the data by the critical adhesion energy allowed a universal subcriticai debond rate curve to be derived.
Thermal and Electromigration Strain Distributions in 10 μm-Wide Aluminum Conductor Lines Measured by X-Ray Microdiffraction
Authors: Wang P.-C. , Cargill G. S. , Noyan I. C. , Liniger E. G. , Hu C.-K. , Lee K. Y.
Published: June 2019

X-ray microdiffraction was applied to study the thermal and electromigration strains in 10 μm-wide Al conductor lines with 10 μm spatial resolution. X-rays were collimated either by pinholes or by tapered glass capillaries to form x-ray microbeams. Measurements were made in a symmetric-reflection geometry so that the strains normal to the sample surface could be examined at different positions along the conductor lines. Results of thermal strain measurements show that the SiO2 passivation plays an important role in limiting relaxation of in-plane compressive thermal stresses in the Al lines, but that the passivation is not effective in confining the overall thermal expansion of the Al line along the film normal. Electromigration strain measurements show that a linear stress gradient developed within the first hour of electromigration. The magnitude of the stress gradient changed little until fast stress relaxations occurred near the anode end of the line. Possible mechanisms are discussed in light of these observations.
White Light Emitting Electroluminescence Devices with Organic Oligomers
Authors: Meghdadi F. , Tasch S. , Graupner W. , Döttinger S.E. , Hanack M. , Graupner M. , Hermetter A. , Leising G.
Published: June 2019

We report on the properties of white light emitting electroluminescence (EL) devices fabricated by combining blue and orange light emitting organic materials, parahexaphenyl (PHP) and a new isothianaphthen-S-oxide (ITSO) oligomer. The EL spectrum of this oligomer blend covers the range from 400 to 650 nm. When the concentration ratios of these materials are suitably adjusted a pure white light emission (CIE coordinates of x=0.333 and y= 0.338) and a high external EL quantum efficiency of 1.2% photons/electron can be obtained. The mechanism of the white light generation is ascribed to an internal self-absorption of part of the blue PHP light emission by ITSO and a subsequent photoluminescence emission process of ITSO. The results of photoinduced absorption, which is sensitive to charged species and triplet states of these guest-host systems, are discussed.
The Leaching Of The Reactive Powder Concretes: Results On Transfer Properties
Authors: Matite V. , Moranville M.
Published: June 2019

The properties of concrete can be altered in aggressive media such as pure water. A leaching test was performed for Reactive Powder Concretes (RPC) in order to evaluate their durability when used as storage of nuclear wastes. Emphasis is placed on the changes of their microstructure, on the tritium diffusion coefficient and on the porosity after leaching. Using mainly non destructive techniques such as SEM, BET and diffusion cell, we found that the leaching affects the RPC microstructure, particularly the anhydrous cement grains. The tritium diffusion coefficient, even lower than that of granite, is however ten times higher after a three month-leaching.
Ultrasonic And Magnetic Techniques For Materials Characterization And Embrittlement Detection
Authors: Thompson R. B. , Igarishi B. , Alers G. A.
Published: June 2019

This paper contains a brief description of recent research advances aimed at the nondestructive characterization of embrittlement, followed by a more detailed discussion of some recent results. The former includes recommendations in the areas of nondestructive evaluation and broader strategies for assessing embrittlement of irradiated reactor pressure vessel steels. The latter describes some very recent results in using measurements of dynamic magnetostriction to monitor the ultra fine scale microstructural changes associated with embrittlement.
Non-Destructive Evaluation of Deformation and Fracture Properties of Materials using Stress-strain Microprobe
Authors: Murty K. L. , Mathew M. D. , Miraglia P. Q. , Shah V. N. , Haggag F. M.
Published: June 2019

Tensile deformation and fracture properties of several metallic materials, welds, and their heataffected-zones were determined non-destructively using the Stress-Strain Microprobe (SSM) system. The system is based on automated ball indentation (ABI) technique and involves straincontrolled multiple indentations at the same location on the material surface by a small spherical indenter. The technique permits evaluation of tensile deformation parameters such as yield strength, ultimate tensile strength, strength coefficient, and strain-hardening exponent, and a fracture energy parameter called indentation energy to fracture. ABI tests were conducted on carbon steels, stainless steels, nickel alloys, aluminum alloys, Zircaloys, electronic soldering materials and several nuclear pressure vessel steels (in the unirradiated, neutron irradiated, and irradiated and thermally annealed conditions). For all these test materials and conditions, the ABI-derived results were found to agree with the data from conventional standard test methods. In addition to the laboratory applications of SSM, it can be used as an in-situ testing instrument for non-destructive assessment of deformation and fracture properties of operating structural components.
Gan Nucleation Mechanism on A Surface Template of Oxidized AIAs
Authors: Kobayashia Nobuhiko P. , Kobayashia Junko T. , Choib Won-Jin , Dapkusa P. Daniel
Published: June 2019

The surfaces of oxidized AlAs (AlOx) layers on Si(111) substrates are studied to understand the mechanism by which single crystal α-GaN can be grown by metalorganic chemical vapor deposition (MOCVD) on AlOx that appears to be an amorphous/fine-grain phase. Contact mode atomic force microscopy (C-AFM) and reflection high energy electron diffraction (RHEED) are used to study the AIOx surface on which a GaN nucleation layer (GaN-NL) is grown. The results indicate that an oriented α-Ga2O3 layer is formed on AlOx which is covered by a GaAs cap layer during oxidation. We infer that the α-Ga2O3 acts as a surface template that provides the order necessary for the subsequent growth of single crystal α-GaN. Characterization using RHEED and selective area electron diffraction (SAD) in cross sectional transmission microscopy (XTEM) reveals that the in-plane crystallographic orientation has a unique alignment between the various layers – GaN, α-Ga2O3 and the Si substrate. This in-plane alignment is understood by considering the atomic arrangement of each material on the plane perpendicular to [111]si at each interface. Moreover a comparison is made between α-GaN grown on α-Ga2O3 and on α-A12O3(0001) to characterize structural defects in α-GaN. The formation of specific structural defects, a large number of planar defects run perpendicular to [111]si in α-GaN/α-Ga2O3 is discussed in conjunction with GaN-NL on α-Ga2O3.
Analysis Of Sige Fet Device Structures On Silicon-on-sapphire Substrates by X-Ray Diffraction
Authors: Mooney P. M. , Chu J. O. , Ott J. A. , Jordan-Sweet J. L. , Meyerson B. S. , Dubbelday W. B. , Lagnado I. , Kavanagh K. L.
Published: June 2019

Si/Si1-xGex, heterostructures on improved silicon-on-sapphire substrates were grown epitaxially by ultra-high vacuum chemical vapor deposition for application as p-channel field effect transistors. High-resolution triple-axis x-ray diffraction was used to analyze these structures quantitatively and to evaluate the effects of device fabrication processes on them. Out-;diffusion of Ge from the Si1-xGex, quantum well was observed after fabrication as was the change in thickness of the Si cap layer due to wafer cleaning and gate oxidation at 875 °C
What can we Predict Before it's Implanted?
Authors: Gibbons Donald F.
Published: June 2019

The material factors which relate to the degradation and/or leaching of ions or molecules are described and the possible biological pathways which they may activate are described, i.e. cytotoxic, immune, tumor and nonspecific inflammatory response. Cytotoxicity is the only biological response which may be measured with high sensitivity by an in vitro assay prior to implantation. All other biological pathways require some degree of in vivo involvement. Three examples of biological response to material factors associated with devices which require evaluation by in vivo assays are discussed, namely: surface topology (texture), mechanically induced factors at the device/tissue interface caused by differences in compliance, and dystrophic calcification in connective tissue and vascular devices.
Ultrahigh Molecular Weight Polyethylene in Total Joint Components
Authors: Wright Timothy M. , Rimnac Clare M. , Bartel Donald L.
Published: June 2019

This article reviews the problem of ultrahigh molecular weight polyethylene component surface degradation in total hip and total knee prostheses, including its clinical implications. Several factors affecting surface damage have been identified from a combination of the observations of in-vivo degradation made on retrieved components, experimental measurement of contact stresses on polyethylene components as a result of contact with their metallic counterpart, and analytical studies of both contact stress and the stresses beneath the polyethylene surface. Both the observations of in-vivo surface degradation and the analytical studies demonstrate that surface degradation is a more severe problem in total knee replacements than in total hip replacements. The performance of polyethylene components, as affected by design factors such as material thickness and material modification, is also considered.
Comparison of Wear resistance of Ion Implanted Surgical Ti-6Al-4V with Other Alloys
Authors: Jianqiang Zhang , Xiaozhong Zhang , Zintang Guo , Hengde Li
Published: June 2019

The wear resistance of N-ion implanted titanium, N-ion implanted Ti-6Al-4V alloy, ion plated Ti-6A1-4V, ion nitrided Ti-6Al-4V and surgical Co-Cr-Mo alloy were studied. All were studied under similar conditions, including dry wear and wear with lubricants of distilled water, saline solution, and human plasma. The results favor use of ion implanted Ti-6Al-4V alloy.
Stimulation Electrodes Based on MnO2 Thin Films: Electrical Properties in Carbonate Buffered Saline
Authors: Kelliher Ellen M. , Rose Timothy L.
Published: June 2019

Hydrous manganese dioxide films are being investigated as a new redox material for the active surface of intracortical stimulation electrodes. The films are electrodeposited at room temperature on Pt substrates from a neutral solution of manganese acetate. The electrochemical properties of the films have been evaluated by cyclic voltammetry in neutral saline solutions buffered with bicarbonate. The films undergo a reversible charge injection reaction represented as

The results obtained in electrolytes of different buffer concentrations indicate the film is able to store the most charge in solutions having the lowest buffer capacity. The kinetics of the redox reaction thus favor operation in an acidic or basic environment in agreement with earlier published results. Two different mechanisms are proposed to explain the rate enhancement at the different pH's. In acidic electrolytes the reaction proceeds by dissolution of the film, while in alkaline solutions the rate determining step of proton diffusion in the solid film is increased. For neural stimulation, therefore, electrodes with manganese dioxide films should be pulsed cathodically to insure a neutral or alkaline environment around the electrode and minimize dissolution of the film.
Biomaterials-Associated Pathology of Cardiac Valve Prostheses: Clinical Explant Analysis and Studies of Tissue Valve Calcification
Authors: Schoen Frederick J. , Levy Robert J.
Published: June 2019

Studies of the pathology of explanted clinical and experimental valve specimens were done to determine the role of biomaterials in the failure of heart valve prostheses. From 7/80 through 12/84, 129 patients had valve prostheses removed at our hospital. Thrombosis/thromboembolism was the most frequent cause of the 39 mechanical valve failures (23%). Structural failure (poor durability) caused 12%. In contrast, with tissue-derived bioprostheses (90 patients), primary tissue degenerative failure was frequent (70%), and was usually associated with calcification (CALC). Infection caused 19% of all valve failures with a frequency not differing among valve types. Other causes of failure were not biomaterials-related. Thus, although frank materials degradation necessitates only a minority of mechanical valve removals, the suboptimal biologic properties of contemporary heart valve biomaterials contribute to some frequent complications (such as thrombosis/thromboembolism). Furthermore, degeneration due to mineralization is the overwhelming mode of failure of bioprosthetic valves.

To understand and potentially eliminate bioprosthetic valve CALC, the kinetics, morphology and host and implant determinants of this process were studied using subcutaneous implants in rats. In this model, in which the pathologic features were similar to those of actual experimental and clinical valve replacements, CALC of glutaraldehyde-treated porcine aortic valve and bovine pericardium began within 48 hours following implantation; mineral levels were comparable to those in failed clinical valves after 84–126 days. Calcific deposits were initially associated with connective tissue cells, but later involved collagen. Systemically-administered ethane-hydroxy-diphosphonate (EHDP), a drug used to treat some forms of metabolic bone disease, inhibited CALC by 97%, but caused significant bone growth retardation. However, EHDP given by site-specific controlled-release largely mitigated CALC at only 1% of the total effective systemic dose, but without adverse effects.
Spectroscopic Ellipsometry Studies of Giaever Immunology Slide
Authors: Yang B. , Kim S. Y. , Vedam K.
Published: June 2019

Spectroscopic ellipsometry has been used to study the dielectric response of indium film evaporated on a glass substrate, as well as that of indium film adsorbed with monolayers of Bovine Serum Albumin (BSA) and Rabbit Antiserum on BSA (RABSA). It is found that the position of the ε2peak (or the peak of the imaginary part of the complex dielectric function) shifts to longer wavelengths and also increases in height as monolayers of BSA and RABSA are successively adsorbed onto it. The observed peak changes are due to the adsorption of BSA and RABSA on the surface of prolate indium clusters, which in effect increases the effective refractive index of voids between indium islands from 1.0 to 1.075 (BSA) and 1.15 (BSA + RABSA).
Light and Scanning Electron Microscopy of Human Spinal Ligaments
Authors: Yahia L.-H. , Drouin G. , Rivard C.-H.
Published: June 2019

Spinal ligaments were obtained from normal and scoliotic individuals. Detailed morphological studies were carried out on the yellow, interspinous and supraspinous ligaments by light and scanning electron microscopy. Normal yellow ligaments are mostly constituted of dense elastin fibers with only a few collagen fibers and sparse blood vessels, while in normal interspinous and supraspinous ligaments, the presence of collagen is highly dominant. In the latter structures, the collagen fascicles are characterized by a regular waviness morphology. The fibrils constituting the fascicles appear either parallel or helical with respect to the fascicle axis. Structural changes are observed in the spinal ligaments of patients with congenital as well as idiopathic scoliosis. For yellow ligaments, only slight differences are found between normal and scoliotic specimens. However, alterations in collagen waviness and architecture are observed mainly in the supraspinous ligaments and to a lesser extent in the interspinous ligaments. In addition, increases in the cellularity, loose connective tissue and vessels are found in both forgoing ligaments. These results indicate that the more pronounced scoliosis-related changes occur in ligaments having the farthest distance from the axis of flexion-rotation.
Technique of surface control with the Electrolyzed D.I.water for post CMP cleaning
Authors: Shirakashi Mitsuhiko , Itoh Kenya , Katakabe Ichiro , Kamezawa Masayuki , Kihara Sachiko , Tsujimura Manabu , Saitoh Takayuki , Yamada Kaoru , Miyashita Naoto , Kodera Masako , Matsui Yoshitaka
Published: June 2019

Chemical mechanical planarization (CMP) has been widely used for planarization of ILD, STI, plug and wiring processes. In post metal CMP cleaning processes, there are still many problems to be solved. There are several surfaces of materials, such as wiring materials, barrier materials, dielectric materials etc., on the wafer that must be cleaned at the same time,. It is also important to clean these different surfaces without any chemical or mechanical damage. We have confirmed that the Electrolyzed D.I.water is effective in post CMP cleaning for controlling the surface condition during cleaning and leaving a robust surface after CMP. We describe the Electrolyzed D.I.water system and present some results on the cleaning capability and control of the metal surface for application to cleaning after a metal CMP process.
Scaling Theory for End-Functionalized Polymers Confined Between Two Surfaces
Authors: Kuznetsov Dmitri V. , Balazs Anna C.
Published: June 2019

Using scaling theory, we determine the equilibrium behavior of a melt of functionalized and non-functionalized polymers confined between two infinite, planar surfaces, which model clay sheets. The functionalized chains contain two end-groups (one at each chain-end) that are highly attracted to the surfaces. Through these calculations, we delineate the conditions for the formation of thermodynamically stable polymer/clay mixtures in terms of the end-group adsorption energy, volume fraction of the end-functionalized chains, and polymer chain lengths.
Interfacial Adhesion of Biopolymer Gels Measured using the Peel Test.
Authors: Pomfret S.J. , Plucknett K.P. , Normand V. , Frith W.J. , Norton I.T.
Published: June 2019

The adhesion between layers of biopolymer gels has been measured using the 90-degree peel test. Gel bilayers, including gelatin, agarose, maltodextrin and κ-carrageenan, were prepared in two ways – simple contact between two pre-gelled layers and layers being cast on top of one another. The force required to separate these layers was measured and the results allow the interfacial properties to be compared as a function of gel type, preparation method used, and layer contact time. A value of approximately 0.2 J/m2 for the interfacial fracture energy is found for a maltodextrin/gelatin interface formed by casting gelatin on maltodextrin. This is in good agreement with values indirectly observed from particle/matrix debonding experiments performed on composite systems.
Adhesion of Triblock Copolymer-Based Thermoreversible Gels and Pressure Sensitive Adhesives
Authors: Shull Kenneth R. , Crosby Alfred J. , Flanigan Cynthia M.
Published: June 2019

Triblock copolymers with poly (methyl methacrylate) (PMMA) end blocks and a poly (n-butyl acrylate) (PnBA) midblock have been synthesized as model pressure sensitive adhesives and thermoreversible gels. These materials dissolve in a variety of alcohols at temperatures above 60 °C to form freely flowing liquids. At lower temperatures the PMMA end-blocks associate so that the solutions form ideally elastic solids. In our case the solvent is 2-ethylhexanol, polymer volume fractions vary from 0.05 to 0.3, and the elastic moduli are close to 10,000 Pa. We have conducted three types of experiments to elucidate the origins of adhesion and bulk mechanical properties of these materials: 1) Weakly adhering gels: The adhesive properties of the gels are dominated by the solvent. Very little adhesion hysteresis is observed in this case, although we do observe hysteresis associated with the frictional response of the layers. 2) Strongly adhering gels. By heating the gels in contact with a PMMA surface, it is possible to bond the gels to the surface. Development of adhesion as the PMMA blocks penetrate into the PMMA substrate can be probed in this case. The cohesive strengths of the gels are found to be substantially greater than their elastic moduli, so that these materials can be reversibly extended to very high strains. These properties have enabled us to probe the origins of elastic shape instabilities that play a very important role in the behavior of thin adhesive layers. 3) Dried gels – model pressure sensitive adhesives. By removing the solvent at low temperatures, the underlying structure of the gel is preserved, giving a thin elastic layer with excellent performance as a pressure sensitive adhesive. Resistance to adhesive failure, expressed as a velocity-dependent fracture energy, greatly exceeds the thermodynamic work of adhesion. This energy is further magnified by ‘bulk’ energy dissipation when the stress applied to the adhesive layer exceeds its yield stress.
Formation Mechanism of Molybdenum and Molybdenum Oxide Nanoparticles by Electron Irradiation
Authors: Jia Husheng , Xu Bingshe , Fan Yadi , Guo Ruiping , Tanaka Shun-ichiro
Published: June 2019

The mechanism of molybdenum and molybdenum oxide nanoparticles formation from molybdenum oxide microparticles by electron beam irradiation using a high-resolution transmission electron microscope on a room-temperature stage have been investigated. It is found that, the microsized molybdenum oxide particles disintegrated to form nanosized molybdenum oxide particles by electron beam irradiation with an intensity of approximately 1021e/cm2 · sec. The molybdenum nanoparticles were formed from molybdenum oxide nanoparticles upon further electron irradiation. During the electron irradiation process, the surfaces and interfaces of molybdenum oxide nanoparticles suffered damage and defects, such as vacancy arrays showing hole like spots and a moire-like fringes in the lattice image due to oxygen loss, followed by a gradual change from molybdenum oxide to molybdenum nanoparticles. The phenomenon of molybdenum metal nanoparticle formation from nanosized molybdenum oxide is considered to be due to desorption of oxygen as a result of electron stimulation and atomic displacement via the knock-on effect. It is suggested that electron irradiation is a powerful technique to create nanostructured metal, ceramic and semiconductor materials by atomic-scale control.
Structure-Property Relationships in W Doped (Ba,Sr)TiO3 Thin Films Deposited by Pulsed Laser Deposition on (001) MgO
Authors: Navi N. , Horwitz J.S. , Wu H.-D. , Qadri S.B.
Published: June 2019

BaxSr(1-x)TiO3 films (BST) with x=0.5, 0.6, 0.7, containing 1% W, were grown by pulsed laser deposition on MgO (001) substrates in an oxygen pressure from 3 to 500 mTorr, at a substrate temperature of 720 C. The crystal structure of the film, as determined from x-ray diffraction, was fit to a tetragonal distortion of a cubic lattice having two in-plane lattice parameters. The in and out-of-plane lattice parameters c, a, á, and lattice distortion (a/c and á/c) were calculated from the positions of the measured BST reflections ((004), (024) and (224)). The dielectric properties of the film at 2 GHz were measured using gap capacitors deposited on top of the dielectric film, at room temperature. For all compositions, as a function of the oxygen deposition pressure, a peak in the change in the dielectric constant, as a function of an applied electric field (0 – 80 kV/cm), was observed for films deposited in 50 mTorr of oxygen. Unlike the pure BST, the dielectric Q was insensitive to the oxygen deposition pressure. The largest Kfactor (K=(ε(0)-ε(V)/ε(0) x Q(0)) for films deposited from Ba0.6Sr0.4TiO3 target were observed in a film that had a minimum in-plane strain, where a~á.
Comparison of Microwave Dielectric Properties of between (001) and (011) Ferroelectric Ba1-xSrxTiO3 Thin Films grown by Pulsed Laser Deposition
Authors: Moon Seung Eon , Kim Eun-Kyoung , Lee Su-Jae , Han Seok-Kil , Kang Kwang-Yong , Kim Won-Jeong
Published: June 2019

The effects of anisotropic dielectric properties of ferroelectric Ba1-xSrxTiO3 (BST) films on the characteristics of phase shifter have been studied in microwave regions at room temperature. Ferroelectric BST films with (001) and (011) orientation were epitaxially grown on (001) and (011) MgO substrates, respectively, by pulsed laser deposition method. The structures of BST films were investigated using x-ray diffraction measurement. The microwave properties of orientation engineered BST films were investigated using coplanar waveguide transmission lines that were fabricated on BST films using a thick metal layer by photolithography and etching process. The measured differential phase shift and insertion loss (S21) for (011) BST films are larger than those for (001) BST films. Dielectric constants of the ferroelectric BST films are calculated from the measured S21 using a modified conformal-mapping model.
A Statistical Analysis of Laser Ablated Ba0.50Sr0.50TiO3/LaAlO3 Films for Microwave Applications
Authors: Romanofsky R.R. , Varaljay N.C. , Alterovitz S.A. , Miranda F.A. , Mueller C.M. , VanKeuls F.W. , Kim J. , Harshavardhan K.S.
Published: June 2019

The NASA Glenn Research Center is constructing a 616 element scanning phased array antenna using thin film BaxSr1-xTiO3 based phase shifters. A critical milestone is the production of 616 identical phase shifters at 19 GHz with ≈4 dB insertion loss and at least 337.5° phase shift with 3 percent bandwidth. It is well known that there is a direct relationship between dielectric tuning and loss due to the Kramers-Kronig relationship and that film crystallinity and strain, affected by the substrate template, play an important role. Ba0.50Sr0.50TiO3 films, nominally 400 nm thick, were deposited on 48 0.25 mm thick, 5 cm diameter LaAlO3 wafers. Although previous results suggested that Mn-doped films on MgO were intrinsically superior in terms of phase shift per unit loss, for this application phase shift per unit length was more important. The composition was selected as a compromise between tuning and loss for room temperature operation (e.g. crystallinity progressively degrades for Ba concentrations in excess of 30 percent). As a prelude to fabricating the array, it was necessary to process, screen, and inventory a large number of samples. Variable angle ellipsometry was used to characterize refractive index and film thickness across each wafer. Microstructural properties of the thin films were characterized using high resolution X-ray diffractometry. Finally, prototype phase shifters and resonators were patterned on each wafer and RF probed to measure tuning as a function of dc bias voltage as well as peak (0 field) permittivity and unloaded Q. The relationship among film quality and uniformity and performance is analyzed. This work presents the first statistically relevant study of film quality and microwave performance and represents a milestone towards commercialization of thin ferroelectric films for microwave applications.
The Effects of Charge Separation in Quaternary Ammonium, DABCO-Containing Polymers on In Vitro Toxicity and Gene Delivery
Authors: Reineke Theresa M. , Davis Mark E.
Published: June 2019

Polycation materials have recently emerged as promising systems for the delivery of genetic material. In this study, several DABCO (1, 4-diazabicyclo[2.2.2]octane) polymers are investigated for their ability to bind and deliver plasmid DNA (pDNA) into mammalian cells. The DABCO polymers are synthesized by copolymerization of DABCO with 1, 3-dibromopropane (D3), 1, 4-dibromobutane (D4), 1, 6-dibromohexane (D6), 1, 8-dibromooctane (D8), and 1, 10-dibromodecane (D10) to form a series of quaternary ammonium polymers with increasing charge separation. Gel retardation experiments reveal that each polymer (D3-D10) binds pDNA above a charge ratio of 1.0 (polymer + / pDNA -). The polycations are examined for in vitro transfection efficiency and toxicity in BHK-21 cells. Results of the transfection experiments indicate that the D6 polymer had the highest transfection efficiency. Although all of the polymers are shown to have some toxicity, the D8 and D10 polymers are more toxic to BHK-21 cells; approximately 30% of the cells survive at a charge ratio of 5 +/- as compared to the D3, D4, and D6 polymers where survival rates are about 80%.
Oral Administration of Chemotherapeutic Agents Using Complexation Hydrogels
Authors: Blanchette James , Park Kinam , Peppas Nicholas A
Published: June 2019

Carriers were synthesized to target delivery of a chemotherapeutic agent, bleomycin, to the upper small intestine in response to the pH shift when entering the upper small intestine from the stomach. Complexation hydrogels capable of pH-responsive swelling were used to form these carriers. Hydrogel nanospheres composed of methacrylic acid (MAA) and poly(ethylene glycol) (PEG) were loaded with bleomycin. Loading of bleomycin was performed by in situ polymerization and release of bleomycin from the nanospheres was measured by UV spectrophotometry. Results showed that bleomycin release from the nanospheres was responsive to the pH of the environment surrounding the nanospheres. In addition to pH-responsive release of bleomycin, the hydrogel nanospheres are also able to enhance the permeability of an in vitro model of the intestinal epithelium. Increasing the permeability of the intestinal epithelium could aid in transport of bleomycin from the lumen of the small intestine out into the bloodstream.
Nanocomposite Polyurethane Foams Via POSS Blends
Authors: McCabe Brock , Nutt Steven , Viers Brent , Haddad Tim
Published: June 2019

Polyhedral Oligomeric Silsequioxane molecules have been incorporated into a commercial polyurethane formulation to produce nanocomposite polyurethane foam. This tiny POSS silica molecule has been used successfully to enhance the performance of polymer systems using co-polymerization and blend strategies. In our investigation, we chose a high-temperature MDI Polyurethane resin foam currently used in military development projects. For the nanofiller, or “blend”, Cp7T7(OH)3 POSS was chosen. Structural characterization was accomplished by TEM and SEM to determine POSS dispersion and cell morphology, respectively. Thermal behavior was investigated by TGA. Two methods of TEM sample preparation were employed, Focused Ion Beam and Ultramicrotomy (room temperature).
TEM Observations of Surface Graphitization and Interior Microstructural Changes in a Furan-Resin-Derived Carbon
Authors: Yamanaka Junji , Yasuda Eiichi , Weatherly George C. , Tanabe Yasuhiro
Published: June 2019

Furan-resin-derived carbon structures have attracted interest as a component in carbon based composite materials. We have investigated the microstructures of furan-resin-derived carbon by transmission electron microscopy after high-temperature heat treatments. We observed that graphitization occurred at the surface even although furan-resin-derived carbon is believed to be a non-graphitizable carbon. On the other hand the interior of the specimens exhibited a cage-like structure. Specimens heat-treated at higher temperatures exhibited a well-developed cage structure, as evidenced by the number of stacked layers and their periodicity. Post-column type EELS was utilized to study the chemical state of the interior of the specimens. All of the EELS spectra had a characteristic edge structure showing the existence of π bonding. There were not significant differences between the spectra of early-stage and well-developed cage structures.
Nanocomposite Barrier Coatings for Elastomeric Applications
Authors: Goldberg H.A. , Feeney C.A. , Karim D.P. , Farrell M.
Published: June 2019

InMat LLC has developed aqueous, non-hazardous nanocomposite dispersions with a unique combination of barrier properties and flexibility. Using butyl rubber as the matrix, and very high aspect ratio vermiculite filler, flexible coatings with gas permeability 30-300 times lower than butyl rubber have been produced.[1,2] These coatings have been shown to be undamaged by strains up to 20%. The first commercial application of this technology (sold under InMat's trademark Air D-FenseTM) is in Wilson's new, longer life, Double CoreTM tennis ball.
Filler Size Effect on the Structure of Polymer-Filler Interface in Polymer-Based Nanocomposites: Entropic and Energetic Effects
Authors: Picu R.C. , Ozmusul M.S.
Published: June 2019

A study of the polymer structure in the vicinity of an interface with a rigid, curved wall is presented. The study is performed by means of lattice Monte Carlo simulations in melts of low and high density. Both purely entropic and energetic systems are considered. The configurational entropy of the chains as well as the cohesive interactions in the bulk polymer lead to the formation of a low-density layer in the close neighborhood of the wall. This layer is about one monomer thick in the purely entropic case, and has a thickness of about three radii of gyration in presence of energetic interactions. Increasing the wall curvature leads to an increase in density in the depleted layer, the effect being more pronounced in the energetic system. Chain end segregation at the wall is observed in all cases. This effect increases with increasing chain length and decreases with increasing wall curvature. The bonds are preferentially oriented in the direction tangential to the wall. The degree of orientation decreases with increasing wall curvature and is independent of chain length. Finally, the evolution of the density, of the segregation effect and of the bond preferential orientation with temperature is investigated. The density at the wall decreases with decreasing temperature in the melt state, while the segregation becomes more pronounced. The volume of polymer in which the structure is affected by the presence of the wall increases with decreasing temperature.