bluuebunny/crossref_metadata_2025 huggingface dataset:
Endotoxins and the importance of procalcitonin
Authors: Yasnó-Navia Paola Andrea , Zuñiga-Ceron Luisa Fernanda , Saavedra-Torres Jhan Sebastián , Pinzón-Fernández María Virginia
Published: June 2019

Gram-negative bacilli and cocci bacteria produce and release endotoxins, which are lipopolysaccharides found in the outer membrane of the cell wall. These endotoxins are responsible for releasing a series of inflammatory mediators such as IL1, TNFα and proteases, as well as lipid mediators such as prostaglandins, leukotrienes, thromboxanes and platelet-activating factor, ultimately activitating immune response cells like leukocytes, macrophages and platelets. These cells amplify the response to shock, generate a procoagulant state and produce alterations at the cellular level, for example, damage to the endothelium, which in the end benefit and worsen the state of septic shock (Figure 1).
Contra el despojo total. Perspectivas de una experiencia de acción social en Caño Negro, Costa Rica
Authors: Torres Sandí Daniel , Retana Céspedes Juan Manuel , Audibert González Lea , Peña Rivera Lidia , Arias Campos Luis Diego
Published: June 2019

En este manuscrito se plantea, a través de la experiencia en Caño Negro (específicamente El Sitio y Las Flores), perspectivas que construyan formas de convivencia que permitan el buen vivir. La experiencia en esta comunidad refleja la organización comunitaria, aunado a la educación y la agricultura, como bases fundamentales para plantear formas de subsistencia alternativas al modelo agroindustrial impuesto en la región, permeado por la explotación laboral y la destrucción ecológica. Por lo tanto, es necesario resaltar y revitalizar los beneficios ecosociales de la vida en el campo ante las presiones y amenazas de parte de la agroindustria, y hacerla atractiva y sostenible en el tiempo.
Recordar, Repetir, Reelaborar en la película Donde viven los monstruos, a través del niño como Rey
Authors: Picado Porras José Daniel
Published: June 2019

El presente ensayo investigativo pretende poner en discusión el lugar de Rey en el que es instalado el personaje Max, por un otro y por sí mismo, bajo un panorama percibido como incomprensión del mundo real hacia él. Se presentan dos visiones/interpretaciones diferentes sobre acciones llevadas a cabo por este niño: una de repente orientada a la visión adulto-céntrica, la otra más de ponerse en el sitio de Max y por lo tanto de intentar que se le reconozca de alguna manera lo que sabe hacer y hasta lo que no sabe hacer, pero que intenta. Gran importancia del fantaseo como herramienta para refugiarse.
Porewater in Compacted Water-Saturated MX-80 Bentonite
Authors: Carlsson Torbjörn , Muurinen Arto , Matusewicz Michał , Root Andrew
Published: June 2019

Bentonite is planned to be used in many countries as a buffer material in repositories for spent nuclear fuel. The proper understanding and modelling of the functioning of the water-saturated bentonite requires knowledge about the bentonite microstructure and also the way water is distributed between different phases. This paper presents experimental results from our studies of water in compacted, water-saturated MX-80 bentonite at dry densities in the range 0.7-1.6 g/cm3. Three techniques, Cl-porosity, SAXS and proton NMR measurements, were applied to samples kept at room temperature, while TEM imaging was applied to high pressure frozen samples. The combined results of these techniques strongly indicate that the two major water phases in the compacted MX-80 bentonite samples are ‘interlayer’ and ‘non-interlayer’ water. The results of the relative amounts of different water types by SAXS and NMR are very similar. The results by Cl-porosity measurement indicate that only part of the non-interlayer water is available for anions. Those observations are discussed in comparison to TEM micrographs. Our study provides solid experimental evidence for the presence of two major water phases in water-saturated bentonite and estimates their relative proportions and pore sizes.
Flexible Printed Supercapacitors Based on Nanostructured Materials
Authors: Maleksaeedi Saeed , Tay Bee Yen , Lee Pooi See , Lai Foo Khuen , Lu Chee Wai
Published: June 2019

With the advent of printed electronics and flexible devices, flexible energy storage has received so much attention in the past few years. In this work, a scalable process for manufacturing of a flexible supercapacitor device based on nanostructured PANI and MnO2 was demonstrated. In this process, nanostructured materials are transformed into form of a printable ink which is applied on a current collector using a simple screen printing method, which can be used in a roll to roll scheme. The flexible device was assembled using a solid polymer electrolyte and the electrochemical performance of the devices was evaluated. A specific capacitance of 120 F/g and 89 F/g for two symmetrical devices based on PANI and MnO2 were obtained respectively. The devices are showing relatively good cyclability and columbic efficiency.
Using Nanoscience as a Theme for Capstone Projects in an Elementary Education Majors Science Course
Authors: Mancini-Samuelson Gina J.
Published: June 2019

The national interest in science, technology, engineering and mathematics (STEM) has called attention to P-12 education, the STEM pipeline. Education of teachers is a primary influence on the education of children in the classroom. While high school (and often middle school) teachers are versed in the content of a particular aspect of STEM (e.g. Mathematics or Chemistry), elementary teachers, on the other end of the pipeline, are educated as generalists, with a primary goal of setting the foundations for future learning.

In 2004, a team of STEM and education faculty at St. Catherine University (SCU) was called together, united by their interest in improving STEM education for all students at SCU, particularly women. Combining the content expertise of the biology, chemistry, physics/engineering, and mathematics departments with the methods expertise of the education department, the team designed courses that made STEM concepts more engaging and relevant to students. In 2010, the STEM Certificate was solidified and required of all elementary education students. It is comprised of three interdisciplinary, team-taught, lab based courses that are open to all undergraduate majors at the institution. Each course is centered on one discipline (i.e. biology, chemistry, or engineering/physics). Chemistry of Life is the chemistry-focused course. The course was designed to include a capstone project. As an introduction to materials science, nanoscience was selected as the theme for the projects. The topic allowed for socially relevant and also highly interdisciplinary projects. Students working in teams of three or four, designed projects, determined how to measure and obtain data, and analyzed and interpreted results. A content and confidence assessment given to students before and after the projects showed an increase in both their understanding of nanomaterials and their confidence in conducting a nanoscience project.
Integrating the NAE Grand Challenges and Holographically-formed Polymer Dispersed Liquid Crystal Thin Films (H-PDLC) into the Kenyan High School Curriculum.
Authors: Coyle Jared P. , Fontecchio Adam K.
Published: June 2019

Access to cutting-edge technologies in materials science and engineering within K-12 education is a great struggle in developing countries. In this work, a problem-based, hands on set of seven modules for integrating Holographically-formed Polymer Dispersed Liquid Crystal (H-PDLC) Bragg Grating thin films into the Kenyan secondary physics, chemistry and mathematics curriculum is proposed. Through funding provided by the National Science Foundation, a pilot study of the integration of these modules, using the National Academy of Engineering’s (NAE) Grand Challenges for Engineering as a contextual vessel, is carried out. The efficacy of these curriculum-integrated modules in communicating real world materials science and engineering challenges is examined using qualitative and quantitative means. A method for expanding the use of this experience with other graduate students is proposed.
Interfacial Reactions between In/Pd and GaAs
Authors: Ma Z. , Allen L. H. , Blanpain B. , Hong Q. Z. , Mayer J. W. , Palmstrom C. J.
Published: June 2019

Interfacial microstructure of In/Pd ohmic contacts to n-GaAs was studied by various X-ray diffraction techniques and secondary ion mass spectroscopy (SIMS). Analysis of this interface after various annealing showed that In1-xGaxAs compounds are formed at the interface and the composition of these compounds depends upon the annealing temperature. As the temperature increases, the stoichiometry of the Inrich compounds tends toward higher concentrations of Ga. The low contact resistance is achieved by dividing the Schottky barrier between metal and GaAs into two barriers due to metal/Inl-xGaxAs and In1-xGaxAs/GaAs. The barrier due to In1-xGaxAs/GaAs is believed to be the main limiting factor in lowering of contact resistance. The observed ohmic behavior for sample annealed at 500°C for 20 s is attributed to the further reduction of this barrier.
Preparation and Study of Conductive Polymer / High-TC Superconductor Assemblies
Authors: McDevitt J. T. , Ritchie J. E. , Jones C. T. , Wells A. D. , Mirkin C. A. , Xu F.
Published: June 2019

In this report, a monolayer of N-(3-aminopropyl) pyrrole is used as a template layer for the controlled growth of polypyrrole on polycrystalline and oriented films of the high temperature superconductor, YBa2Cu3O7. Large increases in the growth rate and smoothness of the polymer layer are obtained with the use of the monolayer template as compared with the bare superconductor electrodes. Observation of the electrochemical growth characteristics as well as polymer morphological properties allows for an evaluation of the local surface conductive properties of superconductor-based ceramic and thin film samples. The use of the amine substituted pyrrole self-assembled monolayer serves to drastically alter the polymer growth characteristics and the surface adhesion properties.
Electrodeposited Magnetic Multilayers
Authors: Schwarzacher W. , Alper M. , Hart R. , Nabiyouni G. , Bakonyi I. , Toth-Kadar E.
Published: June 2019

Electrodeposited magnetic multilayer films consisting of alternating layers of a ferromagnetic and a non-magnetic metal may exhibit giant magnetoresistance (GMR), but the effect is very sensitive to whether deposition is carried out under potentiostatic or galvanostatic control, and the choice of substrate. The texture of Co-Ni-Cu/Cu superlattices grown on polycrystalline (100)-textured Cu plates and (HO)-textured Cu foil under potentiostatic control depended on that of the substrate, while comparable superlattices grown under galvanostatic control had a predominantly (111) texture. The films grown under galvanostatic control generally exhibit AMR or smaller GMR. The magnetic and magnetotransport properties of Co-Ni-Cu/Cu superlattices and a single-layer Co-Ni-Cu film electrodeposited directly onto n-GaAs (100) are also described, and evidence is presented for an in-plane magnetic anisotropy in these samples.
In-Situ Stm Studies on the Electrodeposition of Ultrathin Nickel Films
Authors: Magnussen O. M. , Möller F. A. , Lachenwitzer A. , Behm R. J.
Published: June 2019

An in-situ STM study of the initial stages of Ni electrodeposition on Au and Cu single-crystals is presented. On reconstructed Au(111) a complex, potential-dependent nucleation and growth process is found, involving selective Ni island formation at specific surface sites and growth of two types (compact and needle-like) of Ni monolayer islands. At higher coverages (1 ML ≤ θ ≤ 5 ML) an almost perfect layer-by-layer growth of a metallic Ni(111)-film was observed. Considerably rougher films were found on Au(100) and Cu(100).
Development of a Continuous Surface Modification System of Fluorocarbon Resin for Strong Adhesion
Authors: Hatao K. , Toyoda K. , Murahara M.
Published: June 2019

Large area surface modification of fluorocarbon resin was performed by ArF laser beam irradiation, and water or B(OH)3 solution for its practical application. To complete treatment in a short time and keep its cost lower, the total amount of photons that induce reactions was reduced by decreasing the laser fluence as well as shot number. Water or B(OH)3 was sandwiched between a fused silica glass and a fluorocarbon resin film to form a thin layer using a capillary phenomenon. The substrate was perpendicularly irradiated with ArF excimer laser through a cylindrical lens. By moving horizontally, the surface was continuously modified. The extensively modified sample was mounted to stainless steel with epoxy resin, and the tensile strength was measured. As a result, the adhesive strengths of the sample modified with water and the one with B(OH)3 solution improved 275 and 490 times that of the untreated sample respectively.
Corrosion Protection of Particulate Aluminum-Matrix Composites by Anodization
Authors: Hou Jiangyuan , Chung D. D. L.
Published: June 2019

Anodization is effective for improving the corrosion resistance of aluminum-matrix composites. For SiC particle filled aluminum, anodization was performed successfully in sulfuric acid electrolyte, as usual. However, for AlN particle filled aluminum, anodization needed to be performed in an alkaline (0.7 N NaOH) electrolyte, because NaOH reduced the reaction between AlN and water, whereas an acid enhanced this reaction. The concentration of NaOH in the electrolyte was critical; too high a concentration caused the dissolution of the anodizing product (Al2O3) by the NaOH, whereas too low a concentration did not provide enough ions for the electrochemical process. The corrosion properties and anodization characteristic of pure aluminum, Al/AlN and Al/SiC were compared. Without anodization, pure Al had better corrosion resistance than the composites and Al/SiC had better corrosion resistance than Al/AlN. After anodization, the corrosion resistance of Al/AlN was better than Al/SiC and both composites were better than pure Al without anodization, but still not as good as the anodized pure Al.
In-Situ Characterization of Oxide Films on Liquid Alkali Metals Using Second Harmonic Generation (SHG)
Authors: Tostmann H. , Nattland D. , Freyland W.
Published: June 2019

The experiments described in this paper clearly show that Second Harmonic Generation (SHG) may be used as a sensitive tool for detecting oxide impurities at interfaces not accessible for usual surface characterization methods. As a striking feature, one peak in the temperature dependent SH intensity is observed for liquid potassium and five peaks for liquid cesium. The occurrence of these peaks cannot be understood in terms of the nonlinear optical properties of the pure metal. By varying the oxygen content present in the melt it can be shown that these peaks must be attributed to the presence of oxide impurities segregating at the interface. In addition it is shown that the presence of oxides at the interface inert sapphire - molten alkali metal significantly alters the structure of the sapphire surface finally leading to corrosion visible even by the eye.
Growth, Structure and Characterization of Electrodeposited Co/Cu Ultrathin Films and Multilayers
Authors: Jyoko Y. , Kashiwabara S. , Hayashi Y.
Published: June 2019

Preparation of giant magnctorcsistancc Co/Cu multilayers by electrodeposition has been discussed on the basis of a nucleation- growth mechanism and experimental observations. Reflection electron microscopy (REM- RHEED) studies of clectrodcpositcd Co, Cu/Pt(111) ultrathin layers and bilayers have revealed a simultaneous multinuclcar multilayer growth (pseudo layer- by- layer growth). REM- RHEED observations have also suggested the formation of an additional (2×2) superstructure on an epitaxially grown Cu/Co/Pt(111) bilayer surface. “Giant” magnctorcsistancc and oscillatory antifcrramagnetic intcrlaycr coupling have been observed in a (111) textured Co/Cu multilayered nanostructurc, prepared by electrodeposition under potential control in the presence of a very slight amount of CrO3. Such a multilayered structure containing a nominal nonmagnetic Cu spacer layer thickness of 3.2 nm exhibits a large saturation magnctorcsistancc of more than 18% at room temperature.
Effective Interactions Approach to Phase Stability in Alloys Under Irradiation
Authors: Enrique Raúl A. , Bellon Pascal
Published: June 2019

Phase stability in alloys under irradiation is studied considering effective thermodynamic potentials. A simple kinetic model of a binary alloy with phase separation is investigated. Time evolution in the alloy results from two competing dynamics: thermal diffusion, and irradiation induced ballistic exchanges. The dynamical (steady state) phase diagram is evaluated exactly performing Kinetic Monte Carlo simulations. The solution is then compared to two theoretical frameworks: the effective quasi-interactions model as proposed by Vaks and Kamishenko, and the effective free energy model as proposed by Martin. New developments of these models are proposed to allow for quantitative comparisons. Both theoretical frameworks yield fairly good approximations to the dynamical phase diagram.
Evolution of the electronic structure of metallic multilayers from two to threedimensionality. A Full Potential Linearized Augmented Plane Wave calculation.
Authors: Mazzone A. M.
Published: June 2019

Full Potential Linearized Augmented Plane Wave calculations have been performed for epitaxial multilayers formed by the noble metals Ag and Cu with a thickness n up to 10 layers. The multilayers have a fcc lattice and are pure or compositionally modulated with a structure of the type Agn Cun or (AgCu)n. For n in the range 2,3 the density of states, evaluated at paramagnetic level, exhibits a sharp reduction of the bandwidth which is consistent with the reduced coordination of these structures. For n ≤ 5 the density of states in the central layers converges to the bulk value while the outer layers retain the narrow bandwidth found at n=2. Due to the absence of charge intermixing and hybridization, these features are shared by multilayers of all composition.
Two-Dimensional Molecular Grids on Mercury
Authors: Varaksa Natalia , Pospíŝil Lubomír , Janouêk Zbynìk , Grüner Bohumír , Wang Bing , Pecka Jaroslav , Magnera Thomas , Michl Josef
Published: June 2019

We describe an electrochemical Langmuir-Blodgett (LB) trough for the synthesis and characterization of regular two-dimensional networks on a mercury surface. Two strategies were applied to the preparation of molecular grids on mercury. One was based on the mounting of lanthanum(III) bis(meso-tetrapyridylporphyrinate) sandwich anions (TPyP)2La on mercury subphase and coupling it with hydroquinone derivatives as temporary, or “phantom”, couplers. These couplers provide a weak and reversible bridging of (TPyP)2La- connectors on mercury. As a result a highly ordered square grid is created prior to the introduction of the real sturdy couplers for the replacement of the “phantom” ones. In the other strategy advantage has been taken of the high affinity of divalent sulfur compounds for mercury ions. The trigonal connectors, 1,3,5-triscarboranylbenzenes with attached alkylthioether chains, are firmly adsorbed on mercury at positive potentials and presumably form a hexagonal grid due to their mutual coupling through mercury ions.
Modeling and Mapping of Nanotopography Interactions with CMP
Authors: Lee Brian , Boning Duane S. , Baylies Winthrop , Poduje Noel , Valley John
Published: June 2019

As the demand for planarity increases with advanced IC technologies, nanotopography has arisen as an important concern in shallow trench isolation (STI) chemical mechanical polishing (CMP) processes. Previous work has shown that nanotopography, or small surface height variations on raw wafers 20 to 50 nm in amplitude extending across millimeter scale lateral distances, can result in substantial CMP-induced localized thinning of surface films such as oxides or nitrides used in STI [1]. This interaction with CMP depends both on characteristics of the wafer such as heights and spatial wavelengths of the nanotopography, and characteristics of the CMP process including the planarization length or pad stiffness.

In this paper we review and extend the previous work on modeling of nanotopography. Three approaches to predicting the post-CMP oxide thinning due to nanotopography are compared. The first approach is the simplest, where a statistical aggregate effect is computed. Following the work of Schmolke [2], a transfer coefficient α is found which captures the portion of the nanotopography that is correlated with the final oxide thinning. The second approach is the most detailed, depending on explicit numerical simulation of pad elastic properties. In this case, a contact wear simulation is used to produce a detailed map of oxide thickness corresponding to any given pre-measured nanotopography wafer surface. The third approach is a signal processing method, sitting somewhere between the previous two extremes in terms of approximation and complexity. In this last case, a two-dimensional transfer function is extracted which captures the spatial smoothing accomplished by CMP. This filter can then be applied efficiently to premeasured nanotopography maps for other wafers to predict the final oxide thicknesses.

We also propose a predictive mapping of post-CMP oxide or nitride thicknesses to provide insight into the relative goodness of a wafer measured for nanotopography which is to be subjected to a CMP process. Specifically, we suggest that for post-CMP impact, maps and computation of areas having insufficient oxide clearing, or having final nitride thickness outside of required ranges, are useful and practical. Such device failure potential maps complement the fundamental nanotopography height map data and metrics based directly on that data, and enable evaluation, comparison, and development of improved wafers and STI CMP processes.
Evaluation of Monodispersed Silica Particles and Ceria Coated Silica Particles for Chemical Mechanical Polishing
Authors: Lu Zhenyu , Lee Seung-Ho , Matijević Egon , Babu S. V.
Published: June 2019

The properties of abrasive particles play a key role in chemical mechanical polishing (CMP). This study used well-defined dispersions of uniform particles, including spherical silica of varying diameters to polish Cu films and silica cores coated with nanosized ceria particles to polish oxide films. It was shown that the total surface area of the silica abrasives in the slurry controlled Cu material removal rate. However, pH, solid content, and particle size of ceria coated silica abrasives did not have a strong correlation to the removal rate of oxide films.
Optimization of Deposition Thickness and Over Polishing Time to Minimize Wafer Level Topography in Copper CMP
Authors: Kang J.M. , Wu Shaoyu , Selvaraj T. , Lin Benfu , Foo P.D.
Published: June 2019

Topography after Cu CMP is one of the main issues in constructing reliable Cu interconnects. The wafer level topography is greatly influenced by many polishing properties such as removal non-uniformity and planarization efficiency, and also by many polishing variables. Among the variables, Cu deposition thickness and over polishing time are easily controllable, and closely related to the topography. For a given polishing condition, the topography can be minimized through the optimization of Cu deposition thickness and over polishing time. A model is proposed to account for the correlation between these variables and the wafer level topography. Numerical result of this model shows a strong dependency of optimized Cu deposition thickness and over polishing time on the removal non-uniformity, dishing susceptibility and over plated bump size.
Reaction Control in Amorphous Silicon Film Deposition by Hydrogen Chloride
Authors: Takano Akihiro , Wada Takehito , Fujikake Shinji , Yoshida Takashi , Ohto Tokio , Aydil Eray S.
Published: June 2019

HCl was added to SiH4 containing plasmas to grow a-Si:H(Cl) films with dangling bonds terminated with Cl instead of H. Bulk and surface infrared spectra, film thickness and optical band gap were examined by in situ multiple total internal reflection Fourier transform infrared spectroscopy and in situ spectroscopic ellipsometry. SiH2Cl2 was also used as a conventional Cl source for reference a-Si:H(Cl) film deposition experiments. The introduction of HCl does not affect the deposition rate significantly, and the deposited a-Si:H(Cl) films contain over 1021cm-3 Cl atoms. HCl addition to the gas phase changes the surface compositions of the growing films drastically from higher silicon hydride to chlorinated lower hydride. The surface reaction control eliminates unfavorable hydride bonding structures such as SiH2 and/or SiH in voids in the deposited films. The a-Si:H(Cl) films deposited from mixtures of SiH4 and HCl do not show significant optical band gap widening in spite of containing over 1021cm-3 Cl atoms, a concentration that is comparable to that of hydrogen. In contrast, a conventional chlorine source of SiH2Cl2 increases the deposition rate significantly compared to HCl. The increase in the deposition rate results in monotonic decrease of the refractive index and the optical band gap widening.
Advanced Lateral Crystal Growth of a-Si Thin Films by Double-Pulsed Irradiation of All Solid-State Lasers
Authors: Kudo Toshio , Seike Koji , Yamazaki Kazunori , Komori Hirohito , Yawaka Sachi , Hamada Shiro , Jin Cheng-Guo
Published: June 2019

A compact annealing machine with all solid-state green lasers has been developed, which has the advantage of widely adjustable solidification rate through the delay time control of two long pulses (pulse width ~100ns). Advanced lateral crystal growth (ALCG) process has been proved by the double-pulsed all solid-state laser annealing. The laser beam has a line shape 0.1mm wide and 17mm long, and the beam profile on the short axis is quasi-Gaussian (FWHM 0.1mm). Scanning the line beam along the short axis at the 86% overlapping ratio, the lateral crystal growth area of width 14μm, parallel to the long axis, is sequentially formed at the pitch of 14μm towards the scanning direction. The advanced lateral growth mechanism is easily explained as follows: (1) At the first irradiation, twin seed lines of width 4μm, parallel to the long axis, generates at a boundary between a near-complete melting region and a complete melting region. (2) At the second irradiation of scanning step 14μm, the front seed line in the scanning direction grows symmetrically toward both sides. (3) At the third irradiation of scanning step 2x14μm, the seeds laterally grow until stopped by the growing of seeds on both sides. Finally the ALCG process by the scanning line-beam technique like the current ELA enables us to produce the laterally grown Si thin-films sequentially arranging the belt-shaped texture at the pitch of 14μm. The quality of the laterally grown Si films is quite well except for the projections generated by the bump of lateral growing seeds.
Improved Electrical Properties in Nanocrystalline Si Formed by Metal Induced Growth
Authors: Ji Chunhai , Anderson Wayne A.
Published: June 2019

In recent work, the electrical properties of metal-induced-grown (MIG) Si thin films were studied by using current-voltage (I-V) data from a metal/Si Schottky contact. It was found that controlling the doping level of the films and annealing in forming gas (15% H2 and 85% N2) can improve the quality of the nc-Si films. From SIMS analysis on the nc-Si film deposited from a highly doped target, the nc-Si can duplicate the doping level of the sputtering target. Study of p-type doped nc-Si films showed that the fabrication of Schottky diodes on nc-Si films made from an extremely high-doped target (∼1020 cm-3) or low-doped target (∼1015cm-3) was not successful. For highly doped p-type films, tunneling causes Ohmic conduction instead of rectifying conduction. For the nc-Si film deposited from a low-doped p-type target, the film shows conversion to n-type characteristics when measured by a hot probe. This might be due to defects or oxygen in the film. N-type films at the middle doping level (∼1017cm-3) gave good Schottky diodes after annealing the film in forming gas at 700°C. The Schottky diodes fabricated by high work-function metal (Au) gave the rectifying ratio of ~∼103. Several techniques, e.g. slow/fast two-step sputtering at low working pressure and surface polishing, were used to improve the photo response of Schottky photodiodes. The open-circuit voltage (Voc) of 0.164V and short-circuit current density (Jsc) of 2.5 mA/cm2 were achieved under 100mW/cm2 illumination.
A Study of Electronic Defects in Hydrogenated Amorphous Silicon Prepared by the Expanding Thermal Plasma Technique
Authors: Reynolds Steve , Main Charlie , Zrinscak Ivica , Aneva Zdravka , Nesheva Diana
Published: June 2019

The electronic properties of amorphous silicon films prepared by the expanding thermal plasma technique have been studied using steady-state and transient photoconductivity measurements. It is found that films deposited at a substrate temperature of 400°C have a conduction band tail slope of 29 meV, deep defect density of order 3×1016 cm-3, an Urbach tail slope of 65 meV, defect absorption of 5-10 cm-1, and a mobility-lifetime product of 1.3×10-7 cm2 V-1. Aslight increase in defect density and reduction in mobility-lifetime product is observed on moderate light-soaking. The overall optoelectronic quality is somewhat poorer than commercial PECVD material, but there is scope for improvement as deposition conditions are further optimised.
Electron-Spin-Resonance Investigation of Laser Crystallized Polycrystalline Silicon
Authors: Brendel K. , Nickel N. H. , Lips K. , Fuhs W.
Published: June 2019

Doped and undoped laser crystallized polycrystalline silicon was investigated by electron-spin-resonance experiments. In P-doped samples two resonance are detected at g = 2.0053 and g = 1.998 which are due to silicon dangling bonds and conducting electrons, respectively. After crystallization a large amount of hydrogen remains in the samples. This residual hydrogen can be activated to reduce the spin density by passivating dangling-bonds. The temperature dependent investigation of the conducting electron resonance reveals that the susceptibility can be described by the sum of Pauli and Curie paramagnetism. The data are discussed in terms of models developed for single crystal and microcrystalline silicon.
Optoelectronic Detection of DNA Molecules Using an Amorphous Silicon Photodetector
Authors: Fixe F. , Prazeres D.M.F. , Chu V. , Conde J.P.
Published: June 2019

This work demonstrates the use of an amorphous silicon (a-Si:H) photodetector to measure the density of covalently-bound DNA molecules tagged with a fluorescent molecule. This device is based on the photoconductivity of a-Si:H in a coplanar electrode configuration. Excitation of a fluorescently-tagged biomolecule with near UV/blue light results in the emission of visible light. The emitted light is then converted into an electrical signal in the photodetector, thus allowing the detection of the presence of the tagged DNA molecules. The design, fabrication and characterization of this integrated a-Si:H-based bio-detector is described. The detection limit of the present device is of the order of 20 pmol/cm2. A surface density of ≤ 30 pmol/cm2 for DNA covalently-bound to an active silica layer was measured with the a-Si:H-based bio-detector.
Process Parameters for Poly-Silicon Deposition at a High Growth Rate (1-7 nm/s) by Hot-Wire Chemical Vapour Deposition
Authors: Rath J.K. , Hardeman A.J. , Werf C.H.M. van der , Veenendaal P.A.T.T. van , Rusche M.Y.S. , Schropp R.E.I.
Published: June 2019

High silane to hydrogen flow ratios and optimum wire temperatures are the key process parameters to achieve high growth rate poly-silicon films by hot wire chemical vapour deposition (HWCVD) using a four-wire hot-wire assembly. Four tungsten wires, 4 cm apart from each other, were used as catalytic filaments. Growth rates higher than 7 nm/s have been achieved at a substrate temperature of ∼510°C. The increase in deposition rate was accompanied by deterioration of two physical properties i.e., decrease in photoresponse and increase in oxygen incorporation in the film, which is attributed to high porosity in the material that is commonly observed in these high growth rate materials. The process conditions to incorporate a high hydrogen content into the material for passivation of defects and donor states have been identified as high hydrogen dilution and lower wire temperature. With these procedures, poly-Si films deposited at 1.3 nm/s showed a high ambipolar diffusion length of 132 nm. Incorporating such poly-Si films as the i-layer in an n-i-p solar cell on a stainless steel substrate, without back reflector, showed an efficiency of 4.4 % and a high open circuit voltage of 0.58 V, which is attributed to effective passivation of defects and dopants by incorporated hydrogen.
Simulations of Buffer Layers in a-Si:H Thin Film Solar Cells Deposited with an Expanding Thermal Plasma
Authors: Petit A.M.H.N. , Zeman M. , Swaaij R.A.C.M.M. van , Sanden M.C.M. van de
Published: June 2019

With an Expanding Thermal Plasma Chemical Vapor Deposition system (ETP-CVD), solar grade amorphous silicon (a-Si:H) can be deposited at high deposition rate (> 2 nm/s). We think that during the first stage of deposition, a material is grown with a higher defect density than the rest of the bulk creating a defect-rich layer (DRL). Therefore we analyzed, by the means of simulations, the influence of the position of the DRL on the performance of a p-i-n a-Si:H solar cell when moved from the p-i towards the i-n interface and as a function of its thickness. We investigate the effect of a buffer layer in between the p- and the i-layer on the external parameters of the solar cell. The presence of a buffer layer increases the electric field near the p-i interface, which leads to a higher collection of free charge carriers at the interface, although the electric field is then diminished deeper in the bulk. It appears that 10 nm thick buffer layer is sufficient to improve the performance. In case no buffer layer is applied, recombination losses at the p-i interface diminish the performance of the solar cell. We also observe that an increase of the DRL thickness results in a reduction of the solar-cell performance, which is more pronounced when the DRL is located in the region close to the p-i interface rather than close to the i-n interface.
Evaluation of Copper Ion Drift in Low-Dielectric-Constant Interlayer Films by Transient Capacitance Spectroscopy
Authors: Yoshino Takenobu , Hata Nobuhiro , Kikkawa Takamaro
Published: June 2019

The evidence of copper (Cu) ion drift in low-dielectric-constant (low-k) interlayer films is clearly shown by transient capacitance measurements for the first time. The bias-temperaturestress (BTS) was applied to the copper electrode of Cu/low-k/p-Si metal-insulator-semiconductor capacitors. After injecting photoelectrons into the low-k film from the substrate, time-dependence of the capacitance was measured. When BTS-applied samples were measured, a decrement of the capacitance was observed, whereas not observed without BTS. The decrement of the capacitance was attributed to thermal emission of electrons from copper-related electronic states. By assuming an attempt-to-escape frequency of the charge from the electronic states, the energy level of Cu was estimated to be 0.8–0.9 eV below the conduction band edge.
Mim Capacitors with HfO2 and HfAlOx for Si RF and Analog Applications
Authors: Yu Xiongfei , Zhu Chunxiang , Hu Hang , Chin Albert , Li M.F. , Cho B.J. , Kwong Dim-Lee , Foo P.D. , Yu M.B.
Published: June 2019

The MIM capacitors with HfO2 and HfAlOx are investigated for Si RF and analog applications. The results show that both the capacitance density and voltage coefficients of capacitance (VCCs) increase with decreasing the HfO2 thickness. A high capacitance density of 13 fF/μm2with a low leakage current and a VCC of 607 ppm/V is obtained for 10 nm HfO2 MIM capacitor, which can meet the requirement of the ITRS roadmap by 2007 for silicon RF application. On the other hand, it was found that both the capacitance density and voltage coefficients of capacitance (VCC) values of the HfAlOx MIM capacitors decrease with increasing Al2O3 concentration. The results show that HfAlOx MIM capacitor with an Al2O3 mole fraction of 0.14 is optimized. It provides a high capacitance density of 3.5 fF/μm2 and a low VCC of μ140 ppm/V2. Also, small frequency dependence, low leakage current, and low loss tangent are obtained. Thus, the HfAlOx MIM capacitor with an Al2O3 mole ratio of 0.14 is very suitable for use in silicon analog applications.
Stress Stability of PECVD Silicon Nitride Films During Device Fabrication
Authors: Hughey Michael P. , Cook Robert F.
Published: June 2019

Conventional, dense dielectrics serve as structural elements in Cu/low-k interconnect structures, and a full understanding of their thermo-mechanical properties is desired to help optimize device fabrication and avoid mechanical failure. Wafer curvature measurements were made on plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films during thermal cycling to explore the large, irreversible, tensile stress developed. Spectroscopic techniques were used to probe the composition and structure of the films after annealing steps and indicate that reaction of hydrogen-containing defects provides the mechanism for stress change. A simple kinetic model, modified by the inclusion of an equilibrium function of hydrogen defects, is proposed and is found to adequately describe stress development.
Interfacial Relationships in Microelectronic Devices
Authors: Lane Michael , Rosenberg Robert
Published: June 2019

The continued shrink of interconnect structures is requiring new materials to be introduced into back-end of the line (BEOL) devices at an increasing rate. These new materials must provide a performance benefit from the previous generation with the recent focus on reducing the effective dielectric constant of the integrated structures. This reduction may occur not only by changing the intralevel dielectric but also by changing the capping layer/diffusion barrier on the chemicalmechanically polished (CMP'd) Cu surface. However, changing this material may alter the reliability of the device structure due to a change in the Cu/cap interface bonding. Another consequence of the decrease in minimum feature size in interconnects is that commonly practiced techniques, such as sputtered liner and Cu seed, may not be extendable to future generations. Accordingly, the focus of this paper is on identifying basic relationships between interfacial chemistry and interfacial adhesion and illustrating how those relationships can be used to address some of the issues that may pose problems in future technologies.
Advanced characterization of ultra-low-k periodic porous silica films – pore size distribution, pore-diameter anisotropy, and size and macroscopic isotropy of domain structure
Authors: Hata N. , Negoro C. , Takada S. , Yamada K. , Oku Y. , Kikkawa T.
Published: June 2019

We have shown previously the results from out-of-plane and in-plane X-ray scattering /diffraction measurements together with transmission electron microscope and X-ray reflectance measurements and shown that they are effective in characterization of a periodic porous silica low-k film [1]. In the present work, we report the results on pore-size distribution, pore-diameter anisotropy, and size and macroscopic isotropy of domain structure.
Synthesis of C and CNx Nanotubes, Using the Aerosol Method
Authors: Glerup M. , Castignolles M. , Holzinger M. , Kanzow H. , Loiseau A. , Bernier P.
Published: June 2019

Here we will present the state-of-the-art of the aerosol synthesis method. We demonstrate the reliability of this method by showing that the method can be successfully used for the synthesis of C and CNx multi walled nanotubes. For characterization, scanning- (SEM) and high resolution transmission electron microscopy (HRTEM) imaging have been carried out. The N/C ratio is determined using Electron Energy Loss Spectroscopy (EELS) combined with TEM.
Modification of Electrical and Mechanical Properties of Single Wall Carbon Nanotubes by Reaction with SOCl2
Authors: Dettlaff-Weglikowska Urszula , Skakalova Viera , Graupner Ralf , Ley Lothar , Roth Siegmar
Published: June 2019

Attaching chemical functional groups to single wall carbon nanotubes (SWNTs) has been achieved by chemical methods. Oxidized purified nanotubes have been treated by thionyl chloride in order to convert carboxyl groups into acylchloride groups. We observe by XPS and EDX that not only chlorine atoms but sulphur containing functional groups are covalently bound to the nanotubes. This chemical functionalization also causes significant changes in the electrical and mechanical properties of the nanotubes. The electrical conductivity measured on mats (bucky paper) increases from 500 S/cm in pristine tubes to 2500 S/cm in modified tubes. Similarly, the Young's modulus of bucky paper increases by about 100 %.
Measurements of Size Scale Effects in Layered Structures
Authors: Bastawros Ashraf , Antoniou Antonia
Published: June 2019

A novel experimental configuration is devised to measure the evolution of the deformation field and the corresponding hardening evolution within soft metallic films constrained by hard layers. The experimental configuration provides pure shear state within the constrained film. The material system utilized comprised ductile layer of tin based solder, encapsulated within relatively hard copper shoulders. Different tin-lead compositions are tested with grain size approaching the film thickness. The in-plane strain distribution within the film layer is measured by a microscopic digital image correlation system. The hardening evolution within such highly gradient deformation field is monitored qualitatively through a 2D surface scan with a nanoindentor. The measurements showed a highly inhomogeneous deformation field within the film with discreet shear bands of concentrated strain. The localized shear bands showed long-range correlations of the order of 3-4 the grain size. A size-dependent macroscopic response on the layer thickness is observed. However, the corresponding film thickness is approximately 100-1000 times larger than those predicted by non-local continuum theories and discrete dislocation.
Amorphization of Nanolaminates during Severe Plastic Deformation: Molecular Simulations in the Cu-Zr System
Authors: Lund Alan C. , Schuh Christopher A.
Published: June 2019

Mechanical alloying techniques, which use plastic deformation to effect structural changes, are commonly used to prepare nanostructured metals with exemplary mechanical properties. When these nanostructured metals are subjected to further straining fully amorphous alloys can result, but there is little understanding of the atomic-scale mechanisms behind this amorphization. In the present work, we explore the final stages of such a mechanical alloying process via molecular simulations. Initial Cu-Zr nanolaminates are sequentially strained and consolidated, and the amorphization process is followed explicitly. The results are in qualitative agreement with existing experimental data, and provide insight into experimentally inaccessible features of the structural evolution.
Sulfonated Polystyrene Ionomers Neutralized with Mixtures of Various Cations Studied by Dynamic Mechanical and Small-Angle X-Ray Scattering Techniques
Authors: Jeon Ho Seung , Song Ju-Myung , Kim Joon-Seop
Published: June 2019

The effects of the addition of mixed cations, i.e. Na+/Cs+, Ba2+/Cs+, and Ba2+/Zn2+, to the acid form sulfonated styrene copolymers on their dynamic mechanical properties and morphology were investigated. It was found that the matrix glass transition temperatures did not change with the ratio of the one cation to the other. As expected, however, the ratio of one cation to the other in the mixed cations affected cluster glass transition temperatures significantly. It was also found that the activation energies for the glass transitions for the matrix phase remained constant, while those for the cluster phase changed with the ratio of the two cations. In addition, the position of the SAXS peak was found to be affected by the type of cations. From the results obtained above, the decrease in the cluster Tg with increasing the amount of cesium and zinc cations in Na/Cs, Ba/ Cs, and Ba/Zn mixtures, were explained on the basis of the considerations of the size, charge, and type of cations, which alter the degree of clustering as well as ion-hopping mechanism.
Grain Size Effects on the Adhesion of Thin Ductile Films
Authors: Cordill M.J. , Muppidi T. , Bahr D.F.
Published: June 2019

Grain size can be controlled by varying the process conditions used to deposit the film and post growth processing. This study examines how the grain size will impact the mechanical properties, hardness and adhesion, of thin ductile films on brittle substrates. The grain structures of copper and tin films were examined using OIM and AFM. The interfacial fracture toughness of each film was calculated using a tungsten overlayer and mechanics based models. The hardnesses of the films were correlated to the measured interfacial fracture toughness, and demonstrate that increased hardness correlates to an increased sensitivity to the Mode II component of loading.
Anisotropy of Nanoindentation – a tool for the determination of nanocrystal orientation ?
Authors: Christopher David , Kenny Steven , Smith Roger , Richter Asta , Wolf Bodo , King Bruce
Published: June 2019

The pile up patterns arising in nanoindentation are shown to be indicative of the sample crystal symmetry. To explain and interpret these patterns, complementary molecular dynamics simulations and experiments have been performed to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe{110}. The simulations show that dislocation loops start from the tip and end on the crystal surface propagating outwards along the four in-plane <111> directions. These loops carry material away from the indenter and form bumps on the surface along these directions separated from the piled-up material around the indenter hole. Atoms also move in the two out-of-plane <111> directions causing propagation of subsurface defects and pile-up around the hole. This finding is confirmed by scanning force microscopy mapping of the imprint, the piling-up pattern proving a suitable indicator of the surface crystallography. Experimental force-depth curves over the depth range of a few nanometers do not appear smooth and show distinct pop-ins. On the sub-nanometer scale these pop-ins are also visible in the simulation curves and occur as a result of the initiation of the dislocation loops from the tip.
Mechanisms of misfit strain relaxation in epitaxially grown BLT (Bi4-xLaxTi3O12, x = 0.75) thin films
Authors: Kim Hyung Seok , Oh Sang Ho , Suh Ju Hyung , Park Chan Gyung
Published: June 2019

Mechanisms of misfit strain relaxation in epitaxially grown Bi4-xLaxTi3O12 (BLT) thin films deposited on SrTiO3 (STO) and LaAlO3 (LAO) substrates have been investigated by means of transmission electron microscopy (TEM). The misfit strain of 20 nm thick BLT films grown on STO substrate was relaxed by forming misfit dislocations at the interface. However, cracks were observed in 100 nm thick BLT films grown on the same STO. It was confirmed that cracks were formed because of high misfit strain accumulated with increasing the thickness of BLT, that was not sufficiently relaxed by misfit dislocations. In the case of the BLT film grown on LAO substrate, the magnitude of lattice misfit between BLT and LAO was very small (~1/10) in comparison with the case of the BLT grown on STO. The relatively small misfit strain formed in layered structure of the BLT films on LAO, therefore, was easily relaxed by distorting the film, rather than forming misfit dislocations or cracks, resulting in misorientation regions in the BLT film.