bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatially Resolved Local Atomic Structure from Exelfs
Authors: Stern E. A. , Qian M. , Sarikaya M.
Published: April 2011

EXELFS, extended energy loss fine structure, is one of the spectroscopic techniques provided by electron energy loss spectrometer in the transmission electron microscope. Here, EXELFS is described for its potential use for determining nanoscale physical properties of complex materials. It is demonstrated that EXELFS analysis, like EXAFS, extended X-ray absorption fine structure in bulk materials, provides short-range structural information such as atomic nearest-neighbors and their distances in amorphous an crystalline samples. Some of the problems that hindered the development and wide use of EXELFS were discussed and their solutions are presented. Further solutions and future prospects are discussed.
Tem Study of the Pt-Ru BI-Metallic Catalyst Formation
Authors: Ma Chaoying , Kowalak A. D. , Sung Changmo
Published: April 2011

Pt colloidal particles with large surface areas are effective electrocatalysts which can be applied in methanol fuel cells. The efficiency of the Pt catalyst can be greatly increased if it is incorporated with a second component such as Ru. By applying TEM, EDXS and XRD, the chemical composition, particle size and crystallinity of Pt and Pt/Ru colloidal particles during synthesis procedure are investigated in this research.
Raman Spectroscopy of Size Selected, Matrix Isolated Si Clusters
Authors: Ogura A. , Honea E. C. , Murray C. A. , Raghavachari K. , Sprenger W. O. , Jarrold M. F. , Brown W. L.
Published: April 2011

We report results of Raman spectroscopy of size selected, matrix isolated Si clusters. Cluster ions produced by laser vaporization are size selected by a quadruple mass spectrometer and co-deposited with cryogenic matrices onto a substrate at ∼15K. A surface-plasmon-polariton-enhanced Raman geometry is used to gain adequate signal.

The observed vibrational frequencies from Si4, Si6 and Si7 are compared with theoretically calculated Raman active modes based on the structures of planar rhombus, distorted octahedron and pentagonal bipyramid, respectively. The agreement is excellent. Cluster agglomeration is observed when cluster concentrations exceed ∼0.3% by volume in the matrix and/or with annealing at ∼28K, below the temperature of matrix evaporation.
Annular Dark Field Imaging in Stem
Authors: Hillyard Sean , Silcox John
Published: April 2011

Annular dark field scanning transmission electron microscopy (ADF STEM) is chemically sensitive at high spatial resolution (e.g., 1.8ë at 100keV). Images can be digitally acquired and recorded, permitting quantitative analysis. It is particularly powerful when used in combination with complementary analysis modes such as x-ray microanalysis and transmission electron energy loss spectroscopy. Critical to the interpretation of these data is an understanding and determination of the electron probe intensity, shape and propagation characteristics inside the specimen. Quantitative measurements of diffraction patterns and images in comparison with computer-based simulations (including phonon scattering) provide a basis for developing that information. Results of a series of studies are reviewed that address questions such as defocus and other instrumental factors, and also the formation of channeling peaks that appear on the atomic columns along zone axes. For example, along Si(100) a peak forms and penetrates over 500ë whereas along Ge(100) it developes rapidly but disappears in less than 200ë. In higher atomic number elements, the penetration is even less (e.g. 1 O0ë for In).
Investigation of the Vicinal Ge(001) Surface with Stm
Authors: Kersten Bart A.G. , Sjerps-Koomen Lianda , Zandvliet Harold J.W. , Blank Dave H.A.
Published: April 2011

The morphology of Ge(001) has been investigated with a UHV - Scanning Tunneling Microscope. The Ge(001) surface was misoriented towards the [011] direction with a miscut angle varying from 0.4° to 5°. The surface stress was found to have considerable influence on the step edge configuration as well as the position of the steps with respect to each other.
Reliability Implications of Defects in High Temperature Annealed Si/SiO2/Si Structures
Authors: Warren W. L. , Fleetwood D. M. , Shaneyfelt M. R. , Winokur P. S. , Devine R. A. B. , Mathiot D. , Wilson I. H. , Xu J. B.
Published: April 2011

High-temperature post-oxidation annealing of poly-Si/SiO2/Si structures such as metal-oxidesemiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. We have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO2 interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases the origin of the defects may be attributed to out-diffusion of O from the SiO2 network into the Si substrate with associated reduction of the oxide. We present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO2 and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO2/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.
Precipitate Drifting and Coarsening Caused by Interface Electromigration
Authors: Ma Qing , Suo Z.
Published: April 2011

A mechanism is proposed to explain electromigration-enhanced precipitate coarsening in Al-Cu alloy interconnects. The interface between the α-phase matrix and a θ-phase Al2Cu precipitate is incoherent, along which both Al and Cu atoms diffuse under an applied electric field. Depending on the relative mobility of Al and Cu, the diffusion causes the precipitate to migrate towards either the positive or the negative electrode. The velocity of a spherical precipitate is proportional to the electric field and the mobilities and inversely proportional to its radius. A critical electric field or precipitate radius exists, above which the precipitate can penetrate a grain boundary. Consequently, the precipitates agglomerate by the synergism between the surface tension-induced ripening and the current-induced migration. The resulting particles are distantly separated, depleting Cu atoms from the rest of the interconnect. The mechanism appears to limit the lifetime of interconnects having bamboo-like grains, tested below 300°C, less than half of the melting temperature of Al.
CeO2/YSZ and SrTiO3/YSZ Double Buffer Layers Deposited on Si(100) by Laser Ablation
Authors: Sanchez F. , Aguiar R. , Ferrater C. , Peiro D. , Queralt X. , Varela M.
Published: April 2011

Yttria stabilized zirconia (YSZ), SrTiO3 and CeO2 thin films have been widely used as buffer layers in YBa2Cu3O7-x (YBCO) deposition on silicon substrates. YBCO superconducting properties are limited by lattice mismatches between YSZ and YBCO, and chemical interaction of CeO2 and SrTiO3 with silicon. In order to avoid these problems we have deposited CeO2/YSZ/Si(100) and SrTiO3/YSZ/Si(100) bilayers by laser ablation. Wide temperature and pressure ranges have been studied. The influence of the intermediate layer on the CeO2 and SrTiO3 films properties has been studied. Previous studies were performed on films of each material on Si(100) and YSZ(100) single crystals. The surface of the films and bilayers is smooth without microcracks and only few droplets are found. Only small interdiffusion is observed in all the cases. Texture of the films changes with deposition conditions. Epitaxial growth of CeO2 has been found both on YSZ(100) single crystals and YSZ buffers on Si(100).
Candidate HTSC Film Substrates of Complex Oxide Perovsk1te Compositions
Authors: Guo Ruyan , Bhalla A. S. , Roy Rustum , Cross L. E.
Published: April 2011

The research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al1/2Ta1/2)O3 and Sr(Al1/2Nb1/2)O3, Ba(Mg1/3Ta2/3)O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.
Anisotropy in Epitaxial Fe3O4 and NiFe2O4 Thin Films
Authors: Margulies D. T. , Parker F. T. , Spada F. E. , Berkowitz A. E.
Published: April 2011

Fe3O4 and NiFe2O4 films were deposited on <100> and <110> MgO substrates by dc magnetron reactive sputtering. X-ray diffraction studies indicate epitaxial films under an inplane tensile stress. Magnetization studies show that the moments of the films are unsaturated in 70 kOe applied fields and they approach bulk values only in extrapolation. Conversion electron Mössbauer spectroscopy (CEMS) studies indicate bulk parameters for the Fe3O4 films, but show deviations from bulk properties for NiFe2O4 films. CEMS studies further indicate a random moment distribution for all films which is an unexpected property. In-plane torque curves are discussed in terms of single crystal behavior. The effect of the inplane tensile stress is also indicated in the torque curves.
Properties of Laser-Deposited Yttria Films on CdTe and Silicon Substrates
Authors: Greer James A. , Tabat Martin
Published: April 2011

Yttria (Y2O3) films have been used for a variety of applications including MIS diodes, capacitors, insulators in transistor gates and electro-luminescent devices, and as optical AR coatings. Several conventional Physical Vapor Deposition (PVD) techniques have been used to deposit Y2O3 films such as evaporationl,2,3,4, ion beam, RF and DC magnetron sputtering5,6,7,8. Here we report on the growth of Y2O3 films using excimer-based Pulsed-Laser Deposition (PLD). This study was motivated by the need to deposit high-quality yttria films onto the backsides of CdTe and CdZnTe substrates to act as an Infra-Red (IR) Anti-Reflective (AR) coating. AR coatings can theoretically increase the efficiency of back-side illuminated HgCdTe photo-voltaic IR detectors from about 65% to 80% over the 3 to 5 μm and 8 to 12 μm bands. For detector fabrication Y2O3 is deposited onto the substrate backside, after HgCdTe diodes have been formed. Low deposition temperatures (T< 75°C) are thus essential in order to reduce Hg diffusion and minimize the creation of vacancies in the HgCdTe lattice. Unfortunately, conventional PVD techniques inadvertently heat uncooled substrates to temperatures above 100°C, even at modest deposition rates (1 Å /sec). Effective cooling of the CdTe or CdZnTe is not practical since these substrates are very fragile and cannot be clamped with significant pressure to cooled backing plates. Furthermore, the fact that the HgCdTe diode array has already been formed on the front-side of the substrate precludes the use of thermal grease or epoxy to improve contact with a water cooled stage. PLD on the other hand, has the ability to deposit Y2O3 fims at relatively high deposition rates when compared to sputtering, with only a small rise in substrate temperature.
Heating Rate Effects in Rapid Thermal Annealing of Arsenic Implanted Silicon
Authors: Souza J.P. de , Fichtner P.F.P. , Sadana D.K.
Published: April 2011

Cross section TEM and channeling analysis show that the heating rate (HR) of a rapid thermal annealing (RTA) cycle affects the residual defect distribution in Si implanted with As+ to a heavy dose (≈ 1016 cm−2). Two defect bands are observed after solid phase epitaxial growth (SPEG): the first one centered at a depth corresponding to the projected range of the As (band I), and the second one located at depth corresponding to the original amorphous crystalline (a-c) interface (band II). The density of defects in band I is found to increase with the As dose, and with the annealing temperature (550 - 650°C, furnace annealing). However, for RTA (800 - 1000°C) both the density and depth distribution of these defects are dependent on HR. We propose that Si self-interstitials (SiI) are created at the a-c interface when As becomes substitutional during SPEG. The SPEG velocity determines whether the SiI are accommodated in the amorphous Si layer (low velocities) or are captured by the regrowing c-Si (high velocities)
Thermal-Radiation Absorption Characteristics of Patterned Wafers During Rapid Thermal Processing
Authors: Wong Peter Y. , Miaoulis Ioannis N.
Published: April 2011

Microscale radiation effects are responsible for the dependence of absorption and temperature distributions on the geometry of the layering structures and the spectral characteristics of the heat source. The effect of patterned wafers, which may contain several different structures and materials, on the wafer absorption characteristics are investigated for rapid thermal processing. A numerical model to determine the thermal radiative absorptivity of the wafer for different structures and materials is presented for different heating conditions. The resulting transient effects are determined numerically for different rapid thermal processes. The changes in radiative properties for rapid thermal annealing and chemical vapor deposition are investigated for patterned wafers.
Monte Carlo Simulation of Radiative Heat Transfer in Rapid Thermal Processing (RTP) Systems
Authors: Cole J. Vernon , Knutson Karson L. , Jensen Klavs F.
Published: April 2011

We present a general purpose Monte Carlo method for the simulation of radiation heat transfer in rapid thermal processing (RTP) chambers. Three-dimensional mesh generation software is used to discretize the surfaces within the system, allowing the simulation of realistic chamber and reflector designs. An adaptive subdivision of the chamber geometry reduces the number of raysurface intersections which must be computed. The method models internal reflection, absorption, and transmission within participating media, and includes wavelength, temperature, and material dependent optical properties. Radiation heat transfer simulations are used to examine a reflector assembly, and to test the assumptions of optical wafer temperature measurement techniques.
Importance of the Photoeffects in Rapid Isothermal Processing (RIP)
Authors: Singh R. , Mavoori J. , Thakur R. P. S. , Narayanan S.
Published: April 2011

There are fundamental differences between conventional furnace processing (CFP) and rapid isothermal processing (RIP). The radiation spectrum of a conventional furnace consists of photons in the infrared and longer wavelength regions, whereas the spectrum of the incoherent light sources used in RIP consist of some ultraviolet, visible, and infrared photons. As compared to CFP, the photophysical and photochemical effects associated with RIP provide the capability of lower temperature processing. Due to photoeffects in RIP, differences are observed in junction movement and defect evolution with different lamp configurations and different kinds of lamps having differing spectra. This implies that diffusion models, in addition to considering processing time and temperature, should also account for the lamp configurations and spectra of the heating sources. The fundamental understanding of photoeffects in RIP can be further exploited to reduce the overall thermal budget used in the manufacturing of semiconductor devices. In this paper we present our study of photoeffects in RIP, which can be of help in the design of the next generation of RIP equipment.
Silicide Formation by Rapid Thermal Processing
Authors: Chen L.J. , Lur W. , Chen J.F. , Lee T.L. , Liang J.M.
Published: April 2011

An overview of silicide formation by rapid thermal processing is presented. Recent progresses on device applications, phase formation, growth kinetics, thermal stability, epitaxial growth, formation of metastable phase, vacancy ordering in rare-earth silicides and Ti-based shallow junctions involving rapid thermal processing are used as examples to highlight the applications of rapid thermal processing in connection with silicide formation.
Hydrodesulphurization of Thiophene by Transition Metal Sulphides: The Electronic Basis for Catalytic Activity
Authors: Smit Timo S. , Johnson K. H.
Published: April 2011

Transition metal sulphides (TMS) have the ability to catalyze the hydrodesulphurization (IDS) of thiophenes occurring in oil. The catalytic activity varies strongly across the TM series, and can in some cases be significantly enhanced by the addition of promotor elements (e.g. Co/Ni in MoS2).

From a series of density functional (DF) scattered-wave electronic structure calculations on first, second and third row TMS, electronic parameters related to the catalytic activity have been identified. The occupation and topology of metal-sulphur antibonding orbitals near the Fermi level are particularly important. An activity parameter, I, which is a measure of the strength of the interaction between metal d and sulphur 3p electrons, correlates well with the experimental HDS activities.
A New Route to Generation of co With a Redox System of Mixture of Metal Oxide and Carbon
Authors: Mimori K. , Hasegawa N. , Tsuji M. , Tamaura Y.
Published: April 2011

An endothermic chemical system composed of pulverized iron-based oxide and carbon powder has been investigated by using the temperature swing method (TSM) at 700 to 800 °C. Ferrite of Mn and Zn, and magnetite were studied. The last material showed the most promising result. In the TSM, magnetite as the working material was reduced to wustite and carbon was concurrently oxidized to CO in a flow of N2 gas at 800 °C (the activation step of the metal oxide). In the reverse process, in a flow of CO2, the wustite was oxidized to magnetite and injected CO2 was reduced to CO at 700 °C (the reduction step of CO2 to CO). Following the reduction step, the chemical composition of the magnetite phase was restored to that existing prior to the activation step. The total amount of oxygen donated to carbon during the activation step was the same as that taken from the magnetite during the reduction step. In this system, the following net reaction can be realized at temperatures of 700 to 800 °C: C + CO2 → 2CO. The process will therefore serve for the utilization of coal and other carbonaceous compounds in much lower temperatures than are employed in the traditional water gas and producer gas reactions.
Highly CO2-Soluble Chelating Agents for Supercritical Extraction and Recovery of Heavy Metals
Authors: Yazdi A. , Beckman E. J.
Published: April 2011

Carbon dioxide is an attractive organic solvent in today's chemical process environment in that it is non-flammable, inexpensive, and exhibits low toxicity. Further, materials solubilized in carbon dioxide are easily and completely recovered/concentrated from solution via a simple pressure quench. Despite these favorable properties, CO2 is non-polar, and as such is a very poor solvent for materials such as conventional metal chelating agents, thus blocking application of carbon dioxide in metal extraction/recovery. Consequently, we are exploring the molecular design of materials which are highly CO2-philic, that is, they exhibit solubilities in carbon dioxide which are significantly greater than alkanes with the same number of main-chain atoms. By functionalizing chelating moieties with CO2-philic oligomers, we have generated materials which both effectively extract metals from solid matrices and which dissolve in carbon dioxide in significant quantities.
A Synergistic Approach to Environmental Concerns in Large Scale MOCVD Processes
Authors: Thompson A. G. , Tompa G. S. , Zawadzki P. A. , Mckee M. , Beckham C. , Powers A. , Gurary A. , Moy K. , Schumaker N. E.
Published: April 2011

Processes used in the production of epitaxial III-V semiconducting materials employ a wide variety of materials that are environmentally hazardous. As production volumes increase, the need to manage these materials becomes a serious concern. As the leading supplier of production scale single and multi-wafer MOCVD systems, we have taken the approach of minimizing the generation of waste by designing our reactor for high reactant utilization efficiency, and then trapping the remainder so that the exhaust stream is clean. We have paid particular attention to both operational efficiency and operator safety. The traps may be simply removed and replaced, with cleaning being performed off line. The trapped materials are reduced to an inert state for subsequent commercial disposal; this is particularly important for phosphorus, which can be highly flammable if improperly handled. The reactor chamber deposits occur below the wafer level and typically are cleaned only after several hundred deposition cycles. These factors contribute to a quick cycle time and high uptime, both of which increase throughput. These issues become more important as the reactor size is increased and when multiple shifts are utilized. These points are exemplified by our operational experience with our new Enterprise series, which holds four 100mm wafers (or seventeen 50mm wafers) per run. We will discuss the progressive trapping of solid As and P compounds and those hydride gases which are not completely decomposed in the reaction chamber. The use of computer modeling to scale the process to larger dimensions and to optimize the deposition conditions will also be discussed.
Reprocessing of Sintered and Melt High Temperature Superconducting Materials
Authors: Vipulanandan C. , Martinz B.
Published: April 2011

Increasing use of High Temperature Superconducting Ceramics (HTSC) in various applications and the cost of the new superconducting powder dictated the need for evaluating the potential of reusing the old HTSC material (yittrium-barium-copper oxide (YBCO); YBa2Cu3O7-x) with minimum reprocessing. This study examined various methods to reprocess two years old sintered and melt bulk YBCO ceramics. YBCO components were ground and processed with and without adding various amount of silver powder, organic binders and new YBCO powder. The reprocessed YBCO powder was also characterized at every step of processing using X-ray diffraction (XRD) and Differential Thermal Analysis (DTA) to identify impurities.

The old YBCO components were first crushed and then ground using automatic grinder and a jet-mill. The ground powder was then mixed with additives and/or binders and compacted uniaxially to 45 ksi. The range of sintereing temperatures from 905 °C to 980 °C were selected based on the past history of sintering/melting temperatures. The reground powder was found to have impurity phases due to its exposure to carbon dioxide and humidity in the atmosphere. Addition of Ag powder resulted in higher relative densities at lower sintering temperatures. The need for re-calcination of used powders was also considered to improve the performance of reprocessed powders. The sintering temperature was selected based on achieving 85% relative density. The results show that the reprocessed powders have to be sintered at higher temperatures than their previous history. The sintered and melt-textured YBCO made from reprocessed powder had similar or better superconducting properties compared to the new powder.
Effects of the Physical Structure of Alumina/Copper Oxide Solids On Their Reactivity for SO2 Removal From Flue Gases
Authors: Dall'aglio Laurent A. , Sotirchos Stratis V.
Published: April 2011

CuO/Al2O3 sorbents based on three aluminas of different pore structure and surface area around 125 m2/g were prepared. Two of the aluminas exhibited bimodal pore size distribution, while the third had narrow unimodal distribution. The effect of copper loading on the physical characteristics of the aluminas (pore size distribution and surface area) was examined using mercury porosimetry and gas adsorption. The reactivity of the sorbents towards SO2 was investigated by carrying out thermogravimetric experiments using simulated flue gas.
Preparation of Powders and thin Films of Complex Oxides From
Metal Alkoxides
Authors: Yanovskaya M.I. , Kotova N.M. , Obvintseva I.E. , Turevskaya E.P. , Turova N.Ya. , Vorottlov K.A. , Lsolov'yova L. , Kovsman E.P.
Published: April 2011

Preparation of complex oxides in the form of powders and thin films from
metal alkoxides is discussed. Most attention is paid to ferroelectric and
related materials ‐ complex titanates and zirconates. Techniques for
preparation of high‐purity morphologically homogeneous powders
Ti2, ZrO2 barium titanate and
BaTiO3‐based solid solutions, MgTiO3,
Bi2WO6, Bi2MoO6 are proposed
and discussed wilh respect to their application in ceramics technology. The
solutions prepared electrochemically in methoxyethanol were widely used for
formation of thin films, e.g. Y2O3‐stabilized
ZrO2 and ρζγ solid solutions on Pt‐coated silicon
substrates.
Inorganic-Organic Hybrid Aerogels
Authors: Schubert Ulrich , Schwertfeger Fritz , Hüsing Nicola , Seyfried Elisabeth
Published: April 2011

Organically modified silica aerogels were prepared by
NH4OH-catalyzed hydrolysis and condensation of
RSi(OMe)3 / Si(OMe)4 mixtures, followed by
supercritical drying of the alcogels with methanol or CO2.
Terminal alkyl or aryl groups, bridging groups or functional organic
(methacryloxypropyl or glycidoxypropyl) groups were employed for R. By the
proper choice of the organic groups, the RSi(OMe)3 /
Si(OMe)4 ratio and the drying conditions, hydrophobic
aerogels, being insensitive towards moisture, were obtained with no residual
Si-OH or Si-OMe groups left. The transparency and porosity of the
organically modified aerogels was only slightly diminished relative to
unmodified silica aerogels. The elastic constant of the aerogels was
significantly influenced by the kind of organic groups. By pyrolysis of the
phenyl-substituted aerogels, nanometer-sized carbon structures were
generated. They partly coat the primary aerogel particles and provide a very
high mass specific extinction in the wavelengths interval critical for
thermal radiative transport.
Synthesis of Hybrid Inorganic-Organic Sol-Gel Coatings for
Optics
Authors: Lebeau B. , Guermeur C. , Sanchez C.
Published: April 2011

The synthesis of transparent hybrid organic-inorganic coatings obtained from
condensation between alkoxysilane containing grafted dyes (azo dyes or
phthalocyanines) and metal alkoxides precursors has been performed. The Red
17 azo dye, known for its high second order polarisability, was bonded to
the silicon oxide network following two procedures: a silylation reaction
between Red 17 and triethoxysilane; a coupling reaction between Red 17 and
3-isocyanatopropyltriethoxysilane. Silicon phthalocyanines (known for their
third order polarisability and inverse saturable absorption properties) were
incorporated into the silicon oxide network by a silylation reaction.
Phthalocyanine doped transparent hybrid organic-inorganic coatings were
obtained from condensation between diethoxymethylsilane and zirconium
propoxide precursors.
29Si NMR and XPS Investigation of the Structure of Silicon
Oxycarbide Glasses Derived from Polysiloxane Precursors
Authors: Corriu R.J.P. , Leclercq D. , Mutin P.H. , Vioux A.
Published: April 2011

Two silicon oxycarbide glasses with different compositions (O/Si ratio 1.2
and 1.8) were prepared by pyrolysis at moderate temperature (900 °C) of
polysiloxane precursors. Their structure was investigated using quantitative
29Si solid-state NMR and X-ray photoelectron spectroscopy
(XPS). The environment of the silicon atoms in the oxycarbide phase
corresponded to a purely random distribution of Si-O and Si-C bonds
depending on the O/Si ratio of the glass only and not on the structure of
the precursors. At the light of the NMR results, the Si2p XPS spectra of the
glasses may be interpreted using the contribution of the five possible
SiOxC4-x tetrahedra. The Cls
spectra of these glasses indicated the presence of oxycarbide carbon in
CSi4 tetrahedra, similar to carbide
carbon, and graphitic-like excess carbon.
Influence of the nature of the R Group on the Hydrolysis and
Condensation Process of Trifunctional Silicon Alkoxides,
R-Si(OR')3
Authors: Delattre Laurent , Babonneau Florence
Published: April 2011

The hydrolysis and condensation reactions of three trifunctional silicon
alkoxides, R-Si(OEt)3, with various R alkyl chains (R =
CH3, C2H5, C8H17),
was followed by 29Si and 1H Nuclear Magnetic
Resonance. The condensation reactions are faster for methyltriethoxysilane
and the degree of condensation of the system is higher. The other two
systems have similar behaviors during the first hours, with lowest degree of
condensation. The condensation reactions slow down for the
octyltriethoxysilane, due to the presence of the long alkyl chains which
prevent condensation reactions between oligomeric species. The influence of
the addition of tetraethoxysilane (TEOS) was studied: for all three systems,
the degree of condensation of the network is higher, indicating the role of
cross-linking played by TEOS.
Interactions Between Crystalline Si3N4 and
Preceramic Polymers at High Temperature
Authors: McGinn Joseph T. , Blum Yigal , Johnson Sylvia M. , Gusman Michael I. , McDermott Gregory A.
Published: April 2011

Polymeric precursors to Si3N4 were mixed with
Si3N4 powder, in various combinations, to form
coatings in Si3N4 and to control microstructure of
Si3N4. The microstructure of polymer-derived
ceramic and preceramic materials was examined by transmission electron
microscopy (TEM) after heat treatment at 900°C and 1200°C and sintering at
1650°C. The observed micro-structure suggests that the
polymer-derived-material properties will approach those of conventionally
formed Si3N4. With proper viscosity control, gaps
between α-Si3N4 powder particles as narrow as 5 to 10
nm are filled by the polymer-derived-material, ensuring full wetting of the
α-Si3N4. Voids as large as 0.3 μm between
(α-Si3N4 particles are filled by the ceramic
precursor, reducing the size of pores formed during subsequent sintering
processes. Intimate bonding between the amorphous, polymer-derived-material
and the crystalline Si3N4 grains is observed after
heat treatments or sintering, a necessary condition for achieving
high-quality properties similar to conventional material. Acicular grains of
α-Si3N4 formed from the equiaxed
β-Si3N4 powder/PCMS mixture upon sintering are also
observed.
The Influence of Morphological Aspects in the Reaction Pathway
and Superconductive Properties of Bi2223-Ca2CuO3
Ceramic Composites
Authors: Miao H. , Primo V. , Ibañez R. , Sapiña F. , Beltran A. , Beltran D.
Published: April 2011

A variation of the solid-state matrix technique has been developed as a
procedure for the preparation of 2223 bismuth superconducting phases
[(Bi,Pb)2Sr2Ca1-nCunO4+2n,
n=3]. The adequate processing of samples of nominal compositions 2223+x
0021, obtained both by this procedure and by the polymer matrix method, has
allowed the modification of the microstructure of the calcium copper excess,
with no noticeable change in that of the 2223 grains. The study of the phase
evolution in the processing of the samples has shown that the formation rate
of the 2223 phase is faster when the particle size of the calcium cuprate is
smaller. A dependence of the intergranular superconducting properties on the
secondary phase is observed, appearing as a maximum in
Jc0/μcer at x=0.2 and x=0.5 for samples prepared by
solid state matrix and polymer matrix methods, respectively.
Interphase Study By Xps of Sol-Gel ZrO2 Coatings On
Stainless Steel
Authors: Quinson Jean-Francois , Chino Chantal , De Becdelievre Anne-Marie , Guizard Christian
Published: April 2011

ZrO2 coatings were obtained by the the alkoxide route and
deposited onto stainless steel using the dip coating technique. The starting
solutions were prepared by mixing zirconium tetrabutoxide, isopropanol,
acetylacetone. The water content for the hydrolitic reaction arose from the
atmosphere moisture.

Useful information for the structural organization of the zirconia/steel
interphase is given by XPS analysis.

It is found that during firing treatment, the main components (Fe, Cr, Ni)
of the stainless steel diffuse into the ceramic coating. XPS data allow to
describe the chemical composition variation from the bulk substrate to the
outer coating surface.
Thermal Stability Enhancement Of Rubbery
Ormosils
Authors: Kramer S. J. , Mackenzie J. D.
Published: April 2011

Thermal stability of a novel rubbery ORMOSIL of condensed tetraethoxysilane
(TEOS) and polydimethylsiloxane (PDMS) was investigated along with methods
by which to improve this stability. Based upon literature review of siloxane
systems, modifications of the base ORMOSIL system was made which included
substitution of polydimethyldiphenylsiloxane (PDMDPS) for PDMS, adding
antioxidant, and adding iron compounds. Relative enhancement was
investigated in terms of resilience measurements, and was also analyzed with
thermo-gravimetric analysis (TGA) and differential thermal anaysis
(DTA).
Synthesis of (Alumino) Silicate Materials Using Organic
Molecules and Self-Assembled Organic Aggregates as Structure-Directing
Agents
Authors: Davis Mark E. , Chen Cong-Yan , Burkett Sandra L. , Lobo Raul F.
Published: April 2011

Microporous zeolites can be synthesized using organic structure-directing
molecules whose function is to organize inorganic species into particular
topologies that then spontaneously self-assemble into the final crystalline
materials. Extension of the zeolite assembly process to the use of organic
molecular aggregates as structure-directing agents yields ordered mesoporous
materials like MCM–41 and MCM–48. A unifying picture of the assembly
processes ocurring in the syntheses of micro- and mesoporous materials is
presented.
29Si, 17O Liquid NMR and 29Si CP-MAS NMR
Characterization of Siloxane-Oxide Materials,
[(CH3)2SiO/TiO2,
(CH3)2SiO/ZrO2]
Authors: Babonneau Florence
Published: April 2011

Sol-gel derived siloxane oxide materials are an entirely new family of
hybrid systems at the frontier between silicones and glasses or ceramics,
with a large variety of potential applications. Better control of the
chemistry involved in their preparation should lead to an improvement in
their properties, and this requires an investigation of the whole process,
from the solution to the final materials. Nuclear Magnetic Resonance is a
very suitable technique for this purpose, and this paper will give some
illustrations on model systems
(CH3)2SiO/TiO2,
(CH3)2SiO/ZrO2, prepared from
dimethyldiethoxysilane and titanium or zirconium alkoxides. It will be
focused mainly on the use of 170 solution NMR which clearly shows
the formation of Si-O-Ti or Si-O-Zr bonds, but also their disappearance
during the aging process. 29Si MAS-NMR spectra of dried gels
confirm that the difunctional units are mainly in polydimethylsiloxane
chains, and that the system is phase separated. However, the use of
cross-polarization techniques involving lK and 29Si
nuclei will allow the detection of small number of units in a more
constrained environment, certainly close to oxide-based particles.
Biochemical Processing of Materials: A Review
Authors: Hench Larry L.
Published: April 2011

Many biological systems have evolved means of controlling the architecture of inorganic-organic composites at a nanometer scale. The principles of biochemistry and materials science underlying the potential use of biochemical processing to develop new molecularly tailored materials are discussed, with emphasis on:

methods of stereochemical control of the organic-inorganic interface,

genetic and enzymic control of biosynthesis and biomineralization,

molecular orbital modelling of bio organic-inorganic interfaces,

barriers and limitations of biomimetic and hierarchical processing,

examples of unique materials made with biochemical processing.

needs and potential applications in human prostheses.
Theoretical and Experimental Investigations of Fullerene Derivatives: C60H2, C60H4, C70H2, AND C60(CH2)2
Authors: Jacobs S. Joshua , Gillen Kenneth T. , Cahill Paul A. , Henderson Craig C. , Rohlfing Celeste M.
Published: April 2011

Hydroboration of C70 in toluene yields a 2:1 mixture of 1,9-C70H2 and 7,8-C70H2. Equilibration of these two isomers in the presence of a Pt catalyst reveals a free energy difference of 1.4 ± 0.2 kcal/mol. Whereas semiempirical calculations have been found to predict the energy ordering of many fullerene derivatives incorrectly, ab initio Hartree-Fock (HF) calculations have been found to yield quantitative predictions of experiment. The HF/6-31G* level energy separation of l,9-C70H2 and 7,8-C70H2 of 1.3 kcal/mol is in excellent agreement with experiment. Relative stabilities of isomers of bis(methano)fullerenes were found to parallel those of analogous C60H4 isomers. Density functional theory (DFT) methods have been tested and are equivalent in accuracy to HF methods if similar basis sets are used. C60H2 and C60H4 can be efficiently produced on larger (≥ 50 mg) scales with diimide generated from potassium azodicarboxylate and acetic acid in o-dichlorobenzene.
Structural and Electrical Characterization of Highly Tetrahedral-Coordinated Diamond-Like Carbon Films Grown by Pulsed-Laser Deposition
Authors: Siegal M. P. , Friedmann T. A. , Kurtz S. R. , Tallant D. R. , Simpson R. L. , Dominguez F. , McCarty K. F.
Published: April 2011

Highly tetrahedral-coordinated-amorphous-carbon (a-tC) films deposited by pulsed-laser deposition (PLD) on silicon substrates are studied. These films are grown at room-temperatures in a high-vacuum ambient. a-tC films grown in this manner have demonstrated stability to temperatures in excess of T = 1000°C, more than sufficient for any post-processing treatment or application. Film surfaces are optically smooth as determined both visually and by atomic-force microscopy. PLD growth parameters can be controlled to produce films with a range of sp2 - sp3 carbon-carbon bond ratios. Films with the highest yield of sp3 C-C bonds have high resistivity, with a dielectric permittivity constant s σ 4, measured capacitively at low frequencies (1 – 100 kHz). These a-tC films are p-type semiconductors as grown. Schottky barrier diode structures have been fabricated.
In-Situ Ellipsometric Monitoring of the Electron Cyclotron Resonance Etching of Diamond-Like Carbon
Authors: Ianno N.J. , Ahmer S. , Pittal S. , Woollam John A.
Published: April 2011

The electron cyclotron resonance (ECR) etching of diamond-like carbon films in an oxygen plasma has been studied. The input variables were flow rate, pressure, power, and bias, while the output parameters were etch rate, and uniformity. In-situ ellipsometry, performed at 44 wavelengths simultaneously, was employed to monitor the etch process in real time. We will show that DLC films can be etched without an applied bias, but the application of an rf induced dc bias greatly enhances etch uniformity. Further, the etch rate is a strong function of the bandgap of the DLC film.
An Analysis of Densification Process of Carbon/Carbon Composites
Authors: Oh Seh-Min , Park Yang-Duk
Published: April 2011

An analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composite with pitch for each cycle. Three factors were defined in the densificationprocess: an impregnation efficiency, w, a retention efficiency, x, and an overall densification efficiency, E. The relationships developed were applied to the results for three cycles of densification of C/C composite to evaluate the factors which depend on the route of impregnation and carbonization. The impregnation efficiency increases as the process is repeated due to a decrease of porosity, and the retention efficiency shows a tendency to be in a reverse proportion to the impregnation efficiency. The overall densification efficiency depends on the carbonization yield of pitch impregnant. The carbonization route P+A+G is the most effective method in densifying C/C composites, in which pressure carbonization(P) increases the carbonization yield and the retention efficiency of pitch, and graphitization(G) increases the impregnation efficiency.
Properties of Ti1-xAlxN Deposited Using Dual Rotatable Magnetrons for Automotive Glass Privacy Coatings
Authors: Morley T. S. , Vyletel B. N. , Crawley R. L. , Nietering K. E.
Published: April 2011

Optically thin films of Ti1-xAlxN were sputter deposited using dual rotatable cathodes in nitrogen and argon-nitrogen environments. The sputtering parameters and film properties were analyzed to develop predictive techniques for possible feedback control during deposition. Also, it was found that feedback control during deposition was suitable for controlling film composition in some magnet configurations.
Measurement of the Effect of Temperature on Stress Distribution and Deformation in Multilayer Optical Thin Film Structures
Authors: Madras Cynthia G. , Wong P. Y. , Miaoulis I. N. , Goldman L. M.
Published: April 2011

This study investigates methods of predicting the deformation and stress distribution in multilayer optical thin film structures. The thin film layers include materials of various thermal expansion coefficients, elastic moduli, and melting temperatures. Each layer is deposited at a different temperature, causing complex thermal and deposition stresses throughout the structure. In addition, since the deposition temperatures of some of the layers are high (>600°C), stress relaxation and plastic flow may occur in materials with low melting temperatures. A combination of theoretical predictions and experimental measurements is used to measure and quantify the deformation caused by residual and thermal stresses in the films as well as any plastic deformation that may have occurred. Results from a model using multilayer plate bending theory to determine the elastic deformation of the device due to thermal stresses are reported. These predictions, as well as a more common method of predicting film stress and curvature, are compared to experimentally measured curvature changes as a function of temperature in the samples. However, when plastic deformation begins to occur at high temperatures, the residual stress and degree of deformation are no longer predictable based on elastic theory alone, and have to be measured experimentally. Plastic deformation in the substrate is discussed as a cause of a high observed curvature following sample heating.
Electroplasticity and Electromigration
Authors: Baker Shefford P. , Knauss Michael P. , Möckl Ulrich E. , Arzt Eduard
Published: April 2011

It is known that an electric current can interact with dislocations in metals. Recent studies suggest that these interactions include current-induced dislocation motion and multiplication (electroplasticity) through both glide and climb mechanisms. Such interactions might be expected to effect both the mechanical properties and the electromigration behavior of the thin metal conductor lines used in integrated circuits. The mechanical properties would be directly modified through changes in dislocation density and mobility. Changes in microstructure and strength could affect electromigration lifetime and failure morphology. In order to investigate the effects of current-dislocation interactions, we conducted three sets of experiments in unpassivated aluminum conductor lines: First, a nanoindentation device was used to measure the mechanical properties of the lines during application of current densities up to 6 MA/cm2. Second, the mechanical properties of the lines were measured ex situ as a function of time in accelerated electromigration testing conditions. Third, the nanoindentation device was used to damage the lines at specific sites and damage morphology was examined during subsequent electromigration experiments by means of in situ scanning electron microscopy. To date we observe no direct effect of electric current on the mechanical properties of conductor lines and no clear correlation between mechanical damage and electromigration failure characteristics. Based on theoretical calculations and previous experiments on bulk samples, these results were not expected.
Strained Layer Epitaxy: A Microscopic Description of Stress Driven Surface Diffusion
Authors: Lefebvre I. , Priester C. , Allan G. , Lannoo M.
Published: April 2011

The origin of the crosshatched morphology very often observed, for instance in the case of InGaAs on GaAs, is studied theoretically. The calculations are performed on the basis of a microscopic valence force field model.The force on an adatom induced by a periodic array of widely spaced dislocations is first determined. This is found to be attractive, in agreement with a previous classical elasticity description. Total energies of ridges are then calculated showing increased stability due to the misfit dislocations. The importance of the surface tension for the shape of the ridges is discussed. The results are finally compared to experimental evidence.
Relationship Between Stress and Surface Roughness in Krypton Implanted MgO
Authors: Gea Laurence , Loubet Jean-Luc , Brenier Roger , Thevenard Paul
Published: April 2011

(001) MgO single crystals were implanted with 150 keV krypton ions (Kr+) at a fluence of 5.1016 ions.cm-2 . The implanted surface, observed with an Atomic Force Microscope (AFM) exhibits striking features that can be described as undulations with a wavelength of 0.5 [μm. We correlate these features to the decrease in density and the stresses induced by the implantation damage. As a matter of fact, a model of surface instabilities provides a relationship between the wavelength of the ondulations and internal stresses. Using this model, implantation stresses are calculated to 2.2 GPa. This is in good agreement with the value of 2 GPa obtained with the help of the microindentation technique and the literature data. Some effects of an ionizing post-irradiation on stress and surface roughness are described.
Cracking During Nanoindentation and its Use in the Measurement of Fracture Toughness
Authors: Harding D. S. , Oliver W. C. , Pharr G. M.
Published: April 2011

Results of an investigation aimed at developing a technique by which the fracture toughness of a thin film or small volume can be determined in nanoindentation experiments are reported. The method is based on the radial cracking which occurs when brittle materials are deformed by a sharp indenter such as a Vickers or Berkovich diamond. In microindentation experiments, the lengths of radial cracks have been found to correlate reasonably well with fracture toughness, and a simple semi-empirical method has been developed to compute the toughness from the crack lengths. However, a problem is encountered in extending this method into the nanoindentation regime with the standard Berkovich indenter in that there are well defined loads, called cracking thresholds, below which indentation cracking does not occur in most brittle materials. We have recently found that the problems imposed by the cracking threshold can be largely overcome by using an indenter with the geometry of the corner of a cube. For the cube-corner indenter, cracking thresholds in most brittle materials are as small as 1 mN (∼ 0.1 grams). In addition, the simple, well-developed relationship between toughness and crack length used for the Vickers indenter in the microindentation regime can be used for the cube-corner indenter in the nanoindentation regime provided a different empirical constant is used.