bluuebunny/crossref_metadata_2025 huggingface dataset:
X-Ray Fluorescence Analysis Capability of HGI2 Detector Systems
Authors: Wang Y.J. , IWANCZYK J.S.
Published: March 2011

A laboratory XRF analysis system employing an HgI2 spectrometer detector has been built. The system consists of an x-ray generator tube, a rotating carousel holding multiple XRF targets, and a probe head containing the HgI2 detector. Tests have been performed on several samples, under vacuum, helium and nitrogen ambient atmospheric conditions. This is of particular interest, since the applications for such an XRF system include operation under different ambient conditions. For applications in terrestrial and space planetary exploration, the expected temperatures and gas ambient will vary widely. Comparative analyses using the various gases were made on spectra obtained from standard geological samples.
Electrical and Physical Characterization of Tin Diffusion Barrier for Sub-Micron Contact Structure
Authors: Yao G.D. , Lu Y.C. , Prasad S. , Hata W. , Chen F.S. , Zhang H.
Published: March 2011

TiN diffusion barriers have been widely used in submicron contact structures, due to its good adhesion (to SiO2, W, Al and Si) properties, low diffusivity (for Si, W and Al) and compatibility with TiSi2 processing. The purpose of this paper is to present the results of physical and electrical characterization of contact structures with a TiN barrier and W plugs. Two different barrier metal processes were compared, Viz: sputtered Ti followed by post RTN and Ti/TiN films followed by post RTA in the range of 600° to 800°C. The devices were thermal stressed at 450°C for 7 hrs after W plug formation and Al metallization. Ti/TiN films with post RTA are generally superior barrier layers than Ti films with post RTA as shown by electrical characterization of contact resistance and barrier integrity. The relationship between electrical properties and microstructure for the two different barrier structures is discussed. W/TiN and TiN/TiSi2 interface structures were characterized using high resolution TEM. TiSi2 was found to be epitaxially grown during RTA, under certain process conditions. The crystal structure of TiSi2 was determined from electron diffraction patterns.
Temperature Measurement for Rtp
Authors: Brueck S. R. J. , Zaidi Saleem H. , Lang M. K.
Published: March 2011

A non-contact temperature measurement technique based on diffraction-analysis monitoring of the thermal expansion of materials is discussed. Due to the need for noncontact temperature measurements during semiconductor processing, silicon was chosen for this demonstration. The diffraction method requires a grating of suitable spatial frequency etched on the surface of the silicon wafer. The diffraction angle from the grating depends on the grating period which varies with temperature. Two symmetrically disposed incident beams are used to provide a differential measurement which is relatively independent of sample tilt. A computer system is used to monitor the diffraction order movement, from the order separation a relative temperature change can be calculated in near real-time. Temperature sensitivity for the diffraction technique is inversely dependent on the grating length (number of lines) and independent of the grating width. A sensitivity of 0.75°C is demonstrated for a 3-mm wide grating over a 20-700°C temperature range.
Application of Constant Absorptivity Ring (Car) to Improve Polysilicon Thickness Uniformity In A Rapid Thermal Chemical Vapor Deposition Reactor
Authors: Sanganeria Mahesh K. , ÖztÖrk Mehmet C.
Published: March 2011

Rapid Thermal Chemical Vapor Deposition (RTCVD) is a promising technology for thin film deposition in advanced cluster tool systems. It is well known that, if left uncompensated, excessive heat losses that occur around the wafer edge can lead to temperature and deposition non-uniformities. Using polysilicon deposition on SiO2 as an example we have shown that deposition non-uniformity can be aggravated by absorptivity variations across the wafer. In this paper, we propose a novel approach to alleviate this problem. In this technique, the edge cooling effect is compensated by increasing the absorptivity of the substrate around its perimeter. This is achieved by etching a thin (width≈200μm) ring from the isolation oxide around the wafer perimeter prior to polysilicon deposition. During polysilicon deposition, the absorptivity of the silicon-oxide-polysilicon structure continually changes resulting in positive and negative feedback mechanisms in certain polysilicon thickness ranges determined by both modeling and experiments. However, this absorptivity always remains less than the constant absorptivity of the silicon-polysilicon ring along the perimeter which is referred to here as the Constant Absorptivity Ring (CAR). The higher absorptivity of CAR shields edge cooling effects from the rest of the wafer. In this paper, we present the results of our experiments conducted to demonstrate the effectiveness of CAR in improving uniformity of polysilicon. We show that by using CAR uniform films can be obtained in a reactor which otherwise delivers a polysilicon non-uniformity of 30-40%.
Microscale Radiation Effects in Multilayer Thin-Film Structures During Rapid Thermal Processing
Authors: Wong Peter Y. , Hess Christopher K. , Miaoulis Ioannis N.
Published: March 2011

The individual film thicknesses of multilayered structures processed by rapid thermal processing are of the same order as the wavelengths of the incident radiation. This induces optical interference effects which are responsible for the strong dependency of surface reflectivity, emissivity, and temperature distributions on the geometry of the layering structures, presence of patterns, and thickness of the films. A two-dimensional, finitedifference numerical model has been developed to investigate this microscale radiation phenomena and identify the critical processing parameters which affect rapid thermal processing of multilayer thin films. The uniformity of temperature distributions throughout the wafer during rapid thermal processing is directly affected by incident heater configurations, ramping conditions, wafer-edge effects, and thin-film layering structure. Results from the numerical model for various film structures are presented for chemical vapor deposition of polycrystalline silicon over oxide films on substrate. A novel technique using an edge-enhanced wafer which has a different film structure near its edge is presented as a control over the transient temperature distribution.
High Quality Silicon Epitaxy In An Ultra High Vacuum Rapid Thermal Cvd Reactor: An Application to Single Wafer Processing
Authors: Sanganeria Mahesh K. , Violetite Katherine E. , ÖztÜrk Mehmet C.
Published: March 2011

In this paper, we report epitaxial growth of silicon in an ultra high vacuum rapid thermal chemical vapor deposition (UHV/RTCVD) equipment. In this study, our objectives were low temperature/low thermal budget processing and a high throughput compatible with single wafer manufacturing. The reactor consists of a load lock, a main process chamber and an intermediate cryopumped vacuum buffer chamber between the two chambers. An ultra-clean process environment was achieved using oil free pumps and point of use gas purifiers. The wafer is heated by a Peak Systems LXU-35 arc lamp through a quartz window. In this system, we achieved good quality silicon epitaxy at low temperature (T≤800°C) in the very low, 100 mTorr, pressure regime with high throughput (Growth rate>0.25 μm/min.). High growth rate was achieved using Si2H6 as the reactant gas instead of SiH4 or SiH2C12 which are more commonly used gases for epitaxial growth. High temperature in-situ cleaning was completely eliminated by initiating film growth on a hydrogen passivated surface obtained via dilute HF etching. Generation lifetimes in the 200-400μs range were measured for deposition temperatures of 700°C, 750°C and 800°C with no strong dependence on the deposition temperature.
Modeling of Boron Diffusion and Activation for Nonequilibrium Rapid Thermal Annealing Application
Authors: Kinoshita H. , Huang T. H. , Kwong D. L.
Published: March 2011

The diffusion and activation of ion implanted boron and BF2 during rapid thermal annealing (RTA) was modeled by considering the reaction kinetics between point defects and boron. The diffusion model uses the Monte Carlo generated point defect profiles, an extended defect model and a surface amorphization model for high dose BF2 implantation. Excellent simulation results have been achieved by using a single set of diffusion and kinetic parameters to model the enhanced diffusion of boron during RTA for a wide range of B and BF2 implant doses.
In-Situ Processing of Si Film Structures in a Rapid Thermal Chemical Vapor Deposition Reactor
Authors: Green M. L. , Brasen D. , Luftman H. , Boone T. , Krisch K.
Published: March 2011

Although the benefits of in-situ processing seem intuitively obvious as higher yield due to particle and contamination control, there is presently little data to support these claims. However, materials characterization data on in-situ grown films suggest that it will be advantageous. In this paper we explore the advantages of in-situ processing in a load-locked rapid thermal chemical vapor deposition (RTCVD) chamber for such processes as cleaning, epitaxial growth, oxidation and polysilicon growth. The cold wall nature and low thermal mass of the RTCVD chamber make it an ideal candidate for a cluster module for thermal processing in an integrated process tool.
A Dual-Function Uhv-Compatible Chamber for i) Low-Temperature Plasma-Assisted Oxidation, and ii) High-Temperature Rapid Thermal Processing of Si-Based Dielectric Gate Heterostructures
Authors: Hattangady S. , Xu X-L , Watkins M.J. , Hornung B. , Misra V. , Lucovsky G. , Wortman J.J.
Published: March 2011

A combination of i) low-temperature, 300-400°C, plasma-assisted oxidation to form the SiO2/Si interfaces, and ii) 800°C rapid thermal chemical vapor deposition, RTCVD, to deposit SiO2 thin films have been used to fabricate gate-oxide heterostructures. This sequence separates SiO2/Si interface formation by the oxidation process from the deposition of the bulk oxide layer by RTCVD. These two processes were performed in situ and sequentially in a single-chamber, ultraclean quartz reactor system. We have studied the chemistry of the interface formation process by Auger electron spectroscopy, AES, and the electrical properties of MOS devices with Al electrodes by C-V techniques.
Simultaneous Formation of Front and Back Contacts on Solar Cells Using Optical Processing
Authors: Sopori Bhushan L.
Published: March 2011

A new approach for semiconductor processing is described in which a melt is created at a semiconductor-metal (S-M) interface by shining light of a suitable spectrum from the semiconductor side. The melt can be controlled and confined to a thin region in the vicinity of the interface by controlling the energy delivered to the interface. The interface region regrows epitaxially on silicon as a Si-metal alloy. This phenomenon appears to be an optically induced effect. The interface reaction is greatly diminished if the light is incident from the metal side. This effect is applied to form low resistivity contacts to N+/ P type solar cells in a one-step process.
A Novel Implantation Free Raised Source/Drain Mosfet Process Using Selective Rapid Thermal Chemical Vapor Deposition Of In-Situ Boron Doped SixGe1-x
Authors: Ren Xiaowei , Öztürk Mehmet C. , Grider Douglas T. , Sanganeria Mahesh , Ashburn Stanton
Published: March 2011

In this paper, we report electrical characterization of raised source/drain MOS transistors fabricated using selectively deposited, in-situ boron doped SixGe1-x as a solid diffusion source to form the source/drain junctions. The alloy can be deposited with an enhanced selectivity at temperatures as low as 600°C resulting in an abrupt doping profile at the SixGe1-x/Si interface. After deposition, junctions are formed by diffusion of boron from the deposited layer into the silicon substrate. The selectively deposited alloy can serve as a sacrificial layer for self-aligned silicide formation elimintaing the problem of silicon consumption in the substrate. In this work, selective depositions were performed in a typical cold-walled, lamp heated rapid thermal chemical vapor deposition (RTCVD) system at ∼ 610 °C using SiH2C12, GeH4 and B2H6 as the reactive gases. Using this process, MOS transistors with effective channel lengths down to 0.45 gtm were successfully fabricated.
A Robust LPCVD Nitride Integrated Process for High Density Non-Volatile Eprom Memories
Authors: Sethi R. B. , Ciari R. P. , Anderson L. , Kim U. S. , Bergemont A.
Published: March 2011

A robust 6" hotwall flatzone nitride system is developed for scaled ONO interpoly. dielectric application in a high density EPROM memory cell. This system is designed to operate at low temperature (660° C) and gas ratio (4:1 NH3: DCS) with integrated silicon carbide components. The obtained key features are low defects (0.25 #/cm2 particles), smooth topography (measured by atomic force microscopy) and superior electrical interface as measured by electrical and optical methods.
A Large Area Rapid Thermal Processor for Flat Panel Displays
Authors: Lee Chunghsin , Bramhall Robert B.
Published: March 2011

The advantages of rapid thermal processing over slow, batch type processing have been demonstrated clearly in flat panel display manufacturing for a number of years. In the case of electroluminescence FPD, the brightness of the blue phosphor is increased by as much as 100%.

However, rapid thermal processors that use a lamp-based heat source - either a tungsten lamp array or a single arc lamp - have great difficulty in achieving heating uniformity over large areas.

By using a resistance-heated continuous heat source developed initially for RTP processing of large silicon wafers, temperature uniformity of less than +/− 2.5°C has been achieved over a panel with diagonal of 530mm.

A description of the system and its characteristics are presented.
Thin Oxynitride Films Prepared by Low Pressure Rapid Thermal Chemical Vapor Deposition
Authors: Mclarty P.K. , Hill W.L. , Xu X.L , Wortman J.J. , Harris G.S.
Published: March 2011

Thin silicon oxynitride (Si-O-N) films have been deposited using low pressure rapid thermal chemical vapor deposition (RTCVD) with silane (SiH4), nitrous oxide (N2O), and ammonia (NH3) as the reactive gases. Structural analysis coupled with a study of deposition conditions indicate that an increase in NH3/N2O flow rate ratios leads to an increased N/O atomic ratio and a decreased Si-O-N deposition rate. Thin film (55-75A) polySi/Si-N-O/Si capacitors and transistors were fabricated for NH3/N2O flow rate ratios from 20% to 100%. Some of the films were subjected to a post deposition anneal at 950°C for 15 seconds in both argon and oxygen. Capacitance voltage measurements indicate a mid-gap interface trap density of ≤ 6 × 1010 eV−1cm−2 for all the films independent of both nitrogen content and post deposition annealing conditions. The transconductance was studied as a function of NH3/N2O flow rate ratio and decreasing peak gm values but improved high field degradation was observed for increased nitrogen content. This is consistent with previous work on nitrided oxides and suggests that the films are under tensile stress. Hot carrier stress at maximum substrate current was performed with the Si-O-N films displaying larger threshold voltage shifts when compared to furnace SiO2 indicating the possible existence of hydrogen related traps.
Characterization of Oxygen-Doped and Non-Oxygen-Doped Polysilicon Films Prepared by Rapid Thermal Chemical Vapor Deposition
Authors: Xu Xiaoli , Misra Veena , Harris Gari S. , Spanos Lycourgos , Öztiirk Mehmet C. , Wortman Jimmie J. , Maher Dennis M. , Irene Eugene A.
Published: March 2011

PolySi films deposited with and without oxygen doping using rapid thermal chemical vapor deposition (RTCVD) have been investigated. Experimental results show that RTCVD systems can be used to provide high deposition rates ( 900-1000 Å/min at 700 °C) for both oxygen-doped and non-oxygen-doped polySi films. The surface roughness of the RTCVD polySi film is about half that of conventional LPCVD polySi films. The surface roughness and grain size of the RTCVD polySi film can be further reduced using oxygen doping. The catastrophic breakdown strength for capacitors using oxygen-doped polySi electrodes are improved compared with the breakdown strength for capacitors using non-oxygen-doped polySi electrodes. Electrical resistivities of B, P and As doped samples of polySi films with oxygen doping are found to be larger than those of polySi films without oxygen doping. Resistivities of silicides formed on the oxygen-doped polySi samples are approximately the same for those of silicides formed on non-oxygen-doped polySi samples.
Thermal Stability of TiSi2 on High Dose Ion Implanted Silicon
Authors: Chen J.F. , Chen L.J. , Lur W.
Published: March 2011

Thermal stability of TiSi2 on blank, high–dose BF2+–, B+–, F+–, As+–, and P+–implanted silicon has been studied by both cross–sectional and plan–view transmission electron microscopy as well as by sheet resistance measurements. The surface morphology of TiSi2 was found to be significantly influenced by the implantation in silicon substrate.

Simultaneous presence of B and F was found to be most effective in stabilizing the TiSi2 thin films. Sheet resistance data were found to correlate well with the morphological and microstructural observation. The mechanisms for the stabilization of silicide films are discussed.
Pulsed Excimer Laser Photoablation by Backside Irradiation of Thin Metal Coated Polymer Films
Authors: Lätsch Stefan , Hiraoka Hiroyuki
Published: March 2011

Backside laser irradiation of metal coated quartz wafers can be used for transferring material imagewise to a target cleanly in absence of chemical vapors. However, the transfer of metal from a quartz surface requires a high energy, resulting in poor quality images in some cases.

Use of a fluorinated polymer layer between the polycarbonate substrate and a Te-Se metal alloy is known for clean fabrication of metal holes in write-once-read-only memory media. Polymer thin films can be used similarly in backside laser irradiation for metal ejection from substrate surfaces.

With an ArF excimer laser at 193 nm, gold and aluminum were ejected imagewise from Teflon AF, poly(methacrylonitrile) and quartz surfaces. The threshold fluences of 230 Å thick gold films from polymer surfaces were 7.9 to 9.7 mJ/cm2, whereas the threshold fluence from a quartz surface was determined to be 17.8 mJ/cm2. For aluminum on top of quartz and aluminum coated polymers, higher threshold fluences were found compared to gold ranging from 12.96 to 22.7 mJ/cm2.Also, interfacial reactions between the polymer films and the metal layer occured and have been studied by SEM and XPS.
Molecular Dynamics Study of the Influence of Specific Interactions on the Structure and Properties of the Interphase
Authors: Maguire John F. , Lupkowski Mark
Published: March 2011

Since the interphase plays an important role in the strength and durability of a bondline, it is essential to develop a fundamental understanding of the interphasal region in order to predict and control its structure and properties. Therefore, a key aspect to consider it's the influence of specific chemical interactions on the evolution of the structure of the interphase. Surface analysis techniques have been very effective in studying this problem. However, such experimental approaches do not yet have the specificity and resolution to obtain the atomic densities as a function of distance from the surface. In this work we employ molecular dynamics calculations to study adsorption of both monomers and polymer networks. The density profiles, molecular structure, and mobility of epoxy, amine, and polymer networks on the surfaces of graphite and alumina have been examined. We have considered the influence of changes in surface chemistry on the interfacial structure of the adsorbed species. For all systems investigated the presence of a surface resulted in pronounced ordering of atomic species in the near surface region. Specific chemical interactions such as hydrogen bonding further enhance this tendency and leads to near-surface structure which is markedly different from the bulk.
Metal Overlayers on Self-Organized Molecular Assemblies: X-ray Photoelectron Spectroscopy of CR/CM and NI/CM on 12-Nercaptododecanenitrile
Authors: Jung D. R. , Czanderna A. W.
Published: March 2011

Overlayers of Cr and Ni deposited at 22 °C and at -100 °C onto self-organized molecular assemblies of HS(CH2 )11 CN on Au have been studied by X-ray photoelectron spectroscopy (XPS). For the lowest overlayer coverages, the C ls and N is core levels show evidence for a chemical interaction between the deposited metal and the CN end-group. At 22 °C and for coverages of 0.6 nm or more, Cr/CN shows a C ls low binding energy, carbide-like shoulder. The degree of metal penetration is assessed based on the attenuation of the C ls and Au 4f intensities, and on the positions of the Cr and Ni 2p levels. In general, the least penetration and the largest binding energy shifts of the C, N, and the Cr or Ni core levels are observed for Cr/CN, while and Ni/CN shows smaller shifts and greater penetration.
Chemical grafting of silane end-functionalized polymer on silicon surfaces
Authors: Karim A , Satija S. K. , Orts W. , Ankner J. F. , Majkrzak C. F. , Fetters L. J.
Published: March 2011

X-ray and neutron reflectivity was used to determine the kinetics of adsorption and characterize the concentration profile of a low molecular weight trichlorosilane endfunctionalized polystyrene adsorbed onto polished silicon wafers. Higher adsorbed amounts were obtained from a cyclohexane solution of the polymer rather than toluene, with kinetics that followed a stretched exponential behavior. For moderately high grafting densities the polymer concentration profile in deuterated toluene (a good solvent) was best modelled using a small tailed parabola. In deuterated cyclohexane (a poor solvent) the brush profile steepened but was substantially smoother than a step, while in D20 (a non-solvent) it became step-like.
Modification of the Interface between Paints and Stainless Steels by Means of an Interphase of Crosslinked Organofunctional Silanes
Authors: Ooij Wim J. Van , Sabata Ashok
Published: March 2011

The adhesion of paint systems to stainless steel substrates can be markedly improved by a pretreatment using organofunctional silanes. The paint-metal interface thus obtained can be made more resistant to corrosive attack by adding a silane crosslinker to the hydrolyzed silane solution. The films formed on the metal surface were characterized by Time-of-Flight Secondary Ion Mass Spectrometry (TOFSIMS).
Plasma Polymerization of Fluorocarbon Thin Films on Glass and Metal Substrates
Authors: O'Keefe M. J. , Rigsbee J. M.
Published: March 2011

Plasma polymerization of thin, fluorocarbon films onto glass, low carbon steel, and aluminium foil substrates using a hexafluoroethane (C2F6) glow discharge in a parallel plate, rf-sputter system was studied. Continuous, 100 nm thick fluoropolymer films were obtained when a graphite sputter target was used as the cathode material. Depositions conducted without the use of a consumable cathode produce continuous but thin (<10 nm) films of fluorocarbon material. Analysis of the plasma by optical emission spectroscopy determined that the dominant species in the discharge was CF2 for both target configurations. An increase in the intensity of specific CF2 transitions was observed when the graphite target was used. Characterization of the deposited films by X-ray photoelectron spectroscopy of the C 1s and F 1s photoelectrons was used to determine the atomic F/C ratio and distribution of CF3, CF2, CF, C-CF, and C binding states. Films fabricated with the graphite target had a lower F/C ratio than depositions made without a consumable target. However, the distribution of binding states and the F/C ratio in the fluoropolymer was dependent on the substrate material. The results of the study indicate that the fluoropolymer film composition was significantly influenced by the underlying substrate material.
Hydrogen Peroxide-Sensitive Electrode Based on Supported Bilayer Lipid Membrane
Authors: Liu W. , Ottova-Leitmannova A. , Tien H. T.
Published: March 2011

Supported bilayer lipid membrane (s-BLM) is a new type of self-assembled membranes. In this paper, the s-BiMs were formed on the tips of the freshly cut Teflon-coated stainless steel wires. The sensitivity of s-Bills to Haca was studied by current and potential measurements. We also investigated the effects of TCNQ and DP-TrF modifiers on the H2O2 response of the s-BLM systems. It was found that DP-TTF molecules can improve the stability of the s-BLM and its sensitivity range to H2O2. Further, the cyclic voltammetric behaviors of the s-Bill systems were studied as a function of H2O2 concentration.
Characterization of Polymers and Their Surfaces Using Ultra-Soft X-Ray Absorption Spectroscopy
Authors: Mitchell Gary E. , Dekoven Benjamin M. , Speth David R. , Jones Mark E. , Curphy James J. , Schmidt Donald L. , Yeh Alvin T. , Gland John L. , Fischer Daniel A.
Published: March 2011

In this paper we illustrate the use of Ultra Soft X-ray Absorption Spectroscopy (USXAS) for the characterization of polymeric materials by highlighting three novel applications of the technique. The surface sensitivity of electron yield (3 nm) and the bulk information available from fluorescence yield USXAS (200 nm) provide unique information on the chemistry of polymer surfaces and interfaces. USXAS is sensitive to both concentration and orientation of functional groups in polymers. The systems highlighted here include the characterization of flame treated model acrylic automotive coatings, ultra-low surface energy crosslinked fluorocarbon films, and spin cast polystyrene films. The chemical and surface sensitivity of the technique are emphasized by the ability of USXAS to detect an increase in the trigonally coordinated carbon at the surface after treatment with a reducing flame. The sensitivity to functional group orientation at the surface is demonstrated by the characterization of the crosslinked flurocarbon polymer films. The results show that the pendant fluoroalkyl moieties of these polymers are strongly oriented perpendicular to the film surface. Spin coated polystyrene films were characterized as a functionv of molecular weight, film thickness and casting solvent. The pendant phenyl groups were found to be preferentially oriented towards the normal to the surface plane, independent of casting solvent, molecular weight, and film thickness
Metal-Polymer Interphases in Structural Adhesive Joints
Authors: Davis G. D.
Published: March 2011

High-performance structural adhesive joints, such as those found in aerospace components, must exhibit both high initial strength and excellent durability in severe environments. These properties are largely governed by the bonding across and the stability of the metal (oxide) - polymer interphase. Modern adherend surface treatments commonly provide the required adequate strength and durability. Factors that can degrade or limit joint strength and durability are discussed along with means to improve or, at least, to prevent reduction of these properties. Finally, areas in which advances are needed: increased understanding of bonding phenomena, improved reliability of bonded joints, and minimized environmental burdens are suggested.
Influence of Polymer Coatings and Adhesion on the Mechanical Strength, Fatigue and Aging of Optical Fibers
Authors: Inniss D. , Shepherd L. , Brownlow D. L. , Zhong Q.
Published: March 2011

The influence of polymer coatings on the mechanical properties of optical fibers is reviewed. Current research is directed at the chemical mechanisms that contribute to mechanical strength degradation. In this review, a chemical kinetics model is applied to describe the influence of polymer adhesion on chemical corrosion of the glass fiber (i.e., its zero stress and stress assisted corrosion).
Conductive Polymer / High-Tc Superconductor Assemblies
Authors: McDevitt John T. , Haupt Steven G. , Riley David R. , Zhao Jianai , Jones Christopher T.
Published: March 2011

The preparation of a hybrid conducting polymer/high-temperature superconductor device consisting of a polypyrrole coated YBa2Cu3O7-δ microbridge is reported. Electrochemical techniques are exploited to alter the oxidation state of the polymer and, in doing so, it is found for the first time that superconductivity can be modulated in a controllable and reproducible fashion by a polymer layer. Whereas the neutral (insulating) polypyrrole only slightly influences the electrical properties of the underlying YBa2Cu3O7-δ film, the oxidized (conductive) polymer depresses Tc by up to 15K. Thus, a new type of molecular switch for controlling superconductivity is demonstrated.
The Effect of Crosslink Density and Complex Fields of Stresses on the Network Chain Mobility of Model Epoxy Resins
Authors: Bron Samuel , Katz Dov
Published: March 2011

The viscoelastic properties of model epoxy resins were investigated using a tensile stress relaxation technique. Simultaneously with the applied tensile strain, the specimens were subjected to torsional oscillations in a specially designed instrument. The crosslinking density of the resins was controlled by the length of the aliphatic chain of the diamine hardener. Smooth master curves were obtained by Computed Aided Superposition (CAS) using a software written especially for this work. The shape of the master curves changed significantly as a function of the frequency of torsional oscillations. Based on previously published data, as well as on pertinent information from literature, it was concluded that the variations in the shape of the master curves reflect corresponding changes in the spectrum of relaxation times of the investigated resins. It is suggested that the observed phenomena are caused by physical processes, such as short-range orientation and physical aging, which lead to densification of the network and a corresponding increase in its stiffness.
Titanium Deposition on Polymer Surfaces: An Xps Study
Authors: Konstadinidis K. , Opila R. L. , Taylor J. A. , Miller A. C.
Published: March 2011

We have used X-ray Photoelectron Spectroscopy to study the chemical interactions at the interface formed during in situ deposition of Ti atoms on triazine, polyimide (PMDAODA), and polystyrene surfaces. For deposition on thin triazine films (∼ 100Å) we observe that titanium carbide is the dominant product, while oxides and nitrides are formed as well. Aging in air causes the carbide and nitride to convert to the more thermodynamically stable oxide. Titanium carbide is also the primary species at the Ti/polyimide and Ti/polystyrene interface. In all cases the reaction of Ti atoms with different sites in the polymer is nonselective.
Thermal Conductivity of Single Carbon Fibers Using Photothermal Deflection Techniques
Authors: Barkyoumb J. H. , Land D. J. , Kidder J. N.
Published: March 2011

A modification of the transverse photothermal deflection technique is used to determine the thermal diffusivity of high-conductivity carbon fibers. A chopped, cw Ar-ion laser beam is focused to a point on the fiber to cause localized heating of the fiber and the surrounding transparent fluid medium. The fluid medium immediately adjacent to the fiber sample is probed with a weak He-Ne laser that grazes the fiber surface and is deflected by the synchronous thermal lens produced near the fiber surface. The pump laser is stepped along the length of the fiber to produce a photothermal signal that is proportional to the temperature gradient along the length of the fiber. The theory necessary to predict the magnitude and phase of the probe beam deflection as a function of distance along the fiber is derived. This signal can then be analyzed by a simple method to determine the thermal diffusivity of the carbon fiber.
Synthetic Fibres for Fibre Concrete Composites
Authors: Feldman Dorel , Zheng Zhihong
Published: March 2011

The use of fibrous reinforcement to improve the strength and deformation properties of concrete is now well established. The concept of fibre reinforcement is to use the deformation of the matrix under stress to transfer load to the fibre. Substantial improvements in static and dynamic strength properties could then be achieved if the fibres are strong and stiff, and loaded to fracture, provided there is, of course, a minimum fibre-volume fraction.

Besides fibres like asbestos, glass and steel, different kind of synthetic fibres such as polyethylene, polypropylene, polyamide and others are recently used for cementitious composites.

Together with general aspects of synthetic fibre concrete composites, original results concerning the study done on a hybrid composite based on steel and polypropylene fibres will be presented and discussed.
The Relationship Between Morphology and Esc in Thermoplastic Toughened Phenolics
Authors: Eccott A. R. , Arnold J. C. , Isaac D. H.
Published: March 2011

A detailed investigation has been performed to relate the environmental stress cracking (ESC) behaviour of thermoplastic toughened phenolic materials to their morphology. Within the range of added thermoplastic studied (0 to 35%), two scales of morphology were seen to occur. In addition to a small scale interpenetrating network, there exists a larger scale morphology formed from “seas” of excess and immiscible thermoplastic. The large scale morphology was studied by performing interference contrast optical microscopy on samples etched with permanganate. A good correlation was obtained between the amount of thermoplastic in the immiscible regions and the overall fraction of thermoplastic in the sample.

Etched samples were subject to ESC via bend tests in methanol and the effects of the morphology on the crack behaviour were observed microscopically while samples were still in the bent condition. It was evident that the large scale morphology was responsible for deflecting microcracks so that they preferentially grew along the interface between the immiscible thermoplastic and well mixed regions.
Chemistry and Properties of Poly(Arylene Ether Benzimidazole)S
Authors: Hergenrother Paul M. , Connell John W. , Smith Joseph G.
Published: March 2011

As part of a program to develop high performance structural resins for aerospace applications, a variety of poly(arylene ether benzimidazole)s were prepared by the nucleophilic displacement reaction of activated aromatic difluorides with bis(hydroxyphenylbenzimidazole) monomers. Glass transition temperatures as high as 364°C and room temperature unoriented thin film tensile strength and modulus as high as 22.8 ksi and 652 ksi, respectively, were observed. The polymer prepared from the reaction of 1,3-bis(4-fluorobenzoyl)benzene and 5,5′-bis[2-(4-hydroxyphenyl)benzimidazole] was selected for more extensive evaluation. To improve the processability, the molecular weight was reduced by upsetting the stoichiometry. Polymers were endcapped with benzimidazole, ethynyl and phenylethynyl groups. The chemistry, physical, and mechanical properties of these materials are presented.
Intelligent Automated Cure Processing of Polyimides
Authors: Kranbuehl David E. , Hart Sean M. , Loos Al
Published: March 2011

An intelligent, closed-loop expert system has been developed for the widely used high performance polyimide PMR-15. This expert system has been used for intelligent, automated sensor/model control of the fabrication of flat panels in both the autoclave and the thermal press. Panels have been made, ranging in thickness from less than 1/8 inch to 1/4 inch, using PMR-15 prepreg. Various prepreg samples have been used, ranging in age from fresh to one year old under freezer storage conditions. These materials exhibit significantly different processing properties as a result of the aging process. This expert system uses in-situ Frequency Dependent Electromagnetic Sensing (FDEMS), the Loos processing model for PMR-15, and the Qualitative Processing Automation Language (QPAL) software shell developed by Frances Abrams in conjunction with the Universal Technology Corporation for the United States Air Force.
High Performance Polymer Films
Authors: Sroog Cyrus E.
Published: March 2011

This paper represents a review of the literature on high performance films. Topics discussed include properties of major polyimide films, the preparation of polyimide films via vapor deposition techniques, special extrusion methods for liquid crystalline polymerlpolyimide blends, factors affecting color in polyimide films, and barrierf ilms.
Diamond Membranes For X-Ray Lithography Masks
Authors: Phillips William , Moreno Miguel A.
Published: March 2011

Process techniques have been developed to produce diamond membranes for application as x-ray lithography masks. Residual stress and grain size of the films are influenced by substrate temperature, chamber pressure, and methane concentration, and optimization of these parameters narrows the range of acceptable process conditions. A reactor geometry was chosen which has the capability to produce membranes with thickness uniformity of ± 7 percent across a 50 mm diameter. A cyclic renucleation technique was developed to maintain the grain size at low levels independent of film thickness. Membranes with RMS roughness of about 25 nm, as determined by atomic force microscopy, are fabricated reproducibly. The elastic modulus of small grained membranes deviates from that of larger grained membranes. This deviation must be taken into account in membrane distortion modeling calculations.
Development Of Robust Multilayer Optics For Use In High-Peak Power Radiation Environments
Authors: Macgowan Brian J. , Mrowka S. , Barbee T. W. , SILVA L. B. DA , EDER D.C. , Koch J.A. , Turner J.A. , Underwood J. H.
Published: March 2011

In many applications, x-ray mulhilayer mirrors are exposed to high peak fluxes of x-rays with subsequent damage to the mirror. Mirror damage is a particularly severe problem with the use of multilayers as cavity optics for short wavelength x-ray lasers. Intense optical and x-ray radiation, from the x-ray laser plasma amplifier, often damages the multilayer mirror on time scales of hundreds of picoseconds. The phenomenon of multilayer mirror damage by pulsed xray emission has been studied using short duration (500 psec) bursts of soft x-rays from a laser produced gold plasma. The results of the experiments will be compared with some simple models and the possibility of increasing the damage thresholds of short wavelength multilayer mirrors will be discussed.
Intra-Granular Microstructure And Stress In Sputtered Tungsten Thin Films
Authors: Ravet M.F. , Badawi K.F. , Durand N. , Lafontaine H. , Barnole V. , Haghiri-Gosnet A.M.
Published: March 2011

Intra-granular microstructure and stress of tungsten rf magnetron sputtered thin films have been correlated for deposits with stresses ranging from 1000 MPa to −1000 MPa and belonging to the zone T of the Thornton's microstructural diagram. For pure α-W films, the stress values determined from the substrate deflection method were shown to be comparable with those determined by the x-ray diffraction sin2ψ method using the α-W (321) reflection. The lattice parameter a0of the unstressed material as deduced and was found to depend on the deposition conditions. In addition, a significant broadening of the (321) diffraction peak was observed foi compressive films, which suggests that the intra-granular microstructure has been changed. These original results are interpreted in terms of structural defects: in particular, compressive stress can be related to an interstitial feature.
In-Situ Stress Control During Sputter Deposition
Authors: Kola R. R. , Miller G. L. , Celler G. K.
Published: March 2011

Sputter-deposited tungsten thin films exhibit high intrinsic stress. This stress can result in both in-plane and out-of-plane distortion when the films are deposited on thin membrane structures such as x-ray masks. To minimize these distortions, intrinsic stresses in these absorber films have to be low and reproducible. Several groups have recently reported that by precisely controlling the sputter deposition conditions, W films with low stresses can be produced. However, the reproducibility is limited. We have built a novel acoustic resonance system, in which one electrode, mounted behind the mask membrane, monitors its position and simultaneously provides an electrostatic drive to keep it vibrating at its resonant frequency. For typical membranes and deposition conditions, vibrational modes in the 1–10 kHz range are observed. During tungsten deposition, sputtering pressure is varied in response to changes in the membrane resonant frequency, so that the film stress is minimized. We have made a systematic study of the microstructure and stress of W thin films using a variety of characterization techniques. We have shown the feasibility of depositing low-stress (<10 MPa) W films by in-situ stress monitoring and control of sputtering pressure. By using a proper combination of substrate heating and sputter power density (thermal engineering), the reproducibility of in-situ stress control is greatly improved. The present experimental results of in-situ stress control during W sputter deposition are very promising for the successful utilization of low stress (<10 MPa) W films as absorbers for x-ray masks.
Ultra-Soft X-Ray Absorption Spectroscopy: A Bulk and Surface Probe of Materials
Authors: Fischer Daniel A. , Mitchell Gary E. , Dekoven Benjamin M. , Yeh Alvin T. , Gland John L. , Moodenbaugh Arnie R.
Published: March 2011

Direct comparisons between the surface and bulk of diverse materials can be made by simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) ultra soft x-ray absorption spectroscopy measurements utilizing a rapid sample interchange apparatus. For example the orientations of functional groups have been characterized at and near the surface of a series of model polymeric materials highlighting the chemical and molecular sensitivity of ultra soft x-ray absorption spectroscopy. In addition we discuss a bulk sensitive use of fluorescence yield to non destructively study a buried metal polymer interface. A second bulk sensitive example is the use of fluorescence yield oxygen K near edge x-ray spectroscopy as a method to determine the hole state density of high Tc materials.
Molecular Level Characterization of Thin Paraffinic Films Using NEXAFS Spectroscopy
Authors: Stevens Paul A. , Martella David J.
Published: March 2011

Because near edge X-ray absorption fine structures (NEXAFS) are due to dipole transitions from core levels to unoccupied molecular orbitals, it is an ideal technique for obtaining molecular level information about the orientations of ordered species. Such information is important in assessing the relative importance of various intermolecular forces. For example in long chain molecules with bulky functional groups it is not clear a priori whether the attractive van der Waals forces will overcome the repulsive steric interactions to allow for ordering in thin films. To investigate this we have performed C-K edge NEXAFS spectroscopy studies of thin films of the paraffinic molecules C36H74 and (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2. The films were grown on a Si(111) surface covered with a native oxide. For the normal alkane, the spectra are dominated by three resolvable (Δhυ≈0.5 eV) features: one (C-H)* peak and two σ*(C-C) peaks. The polarization dependence of these peaks indicates that sub-250 Å C36H74 films have the chains of the molecules aligned along the surface normal. For ≈ 2000 Å films the molecular axes are inclined at angle of 32° with respect to the surface normal, in agreement with the crystalline structure determined by X-ray diffraction. In addition to the major structures of the alkane chains, the C-K NEXAFS of (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2 has a distinct π* peak due to the phenyl ring. Analysis of these resonances indicates that the C-C chains are also aligned along the surface normal, while the phenyl ring is inclined at an angle of 42° with respect to the normal. In conclusion NEXAFS spectroscopy has been used to show that, for the molecules studied, the attractive van der Waals interactions dominate the repulsive forces thus allowing the molecules to orient with their chains aligned along the surface normal in thin films formed on native oxide covered Si(111).
EXAFS Study of Co/Ag Multilayers
Authors: Foiles C. L. , Loloee R. , Morrison T. I.
Published: March 2011

Co EXAFS data for these Co/Ag multilayers exhibit no changes in basic form and obey a simple scaling with Co thickness down to 6Å. Over this same thickness range the giant magnetoresistance and the manner in which magnetization approaches saturation change substantially. These results indicate that local structural changes do not play a significant role in altering the magnetic properties of this multilayer system.
XAFS Characterization of Cu-Doped ZnO Films
Authors: Mikkelsen J. C. , Boyce J. B. , Bridges F.
Published: March 2011

This paper describes x-ray absorption measurements made on 10 to 16-μm-thick films of ZnO, which contained 5 mol% CuO, and were grown by reactive sputtering. We compare our experimental near-edge and XAFS results to models for Cu-O phases and Cu incorporation into the ZnO lattice, and we conclude that roughly half of the Cu atoms are substitutional for Zn on the wurtzite lattice and the other half is in a highly disordered phase, which has an XAFS signature which is similar to disordered CuO. Our results are compared to other structural studies of Cu-doped ZnO materials.
Photoelectron Holography Of Platinum (111)
Authors: Petersen Barry L. , Terminello L. J. , Shirley D. A.
Published: March 2011

Platinum atoms near a (111) single-crystal face have been imaged using photoelectron holography. Electron angular intensity patterns were collected at equally spaced wavenumbers from 6Å−1 to 12Å−1. Images of atoms near expected atomic positions are obtained from single-wavenumber analyses over the range of the data set. Positions are detected further from the emitter than we have seen previously, and we have also adopted a three dimensional means of representing the data in order to help understand the results. Twin image suppression and artifact reduction in the holographically reconstructed data set are obtained when images at different wavenumbers are correctly phase-summed. We are assessing the capability of the technique for rendering true three-dimensional structural information for unknown systems.
Phase Identification in Rapidly Solidified Al-In Alloys Using High Resolution Synchrotron Radiation Diffraction and Transmission Electron Microscopy
Authors: Tao J. , Aken D. C. Van , Bilello J. C.
Published: March 2011

A metastable (face centered) cubic form of indium has been identified in melt-spun Al-4.3at% indium using high resolution synchrotron radiation diffraction. The microstructure of the melt-spun ribbons consisted of particles of nominally pure indium dispersed in an aluminum matrix. These particles ranged in size from 10 nm to 1000 nm through the thickness of the ribbons. Only the smallest indium particles were identified as being cubic and these were observed in electron transparent regions of the as-spun ribbons. The cubic indium phase had the following orientation relationship with the matrix: [001]In′ // [001]Al and (100)In′ // (001)Al. The size distribution and average diameter of the cubic particles were obtained by quantitative analysis of the diffraction line profiles. These measurements were corroborated with transmission electron microscopy observations. The volume percent of the cubic indium phase was determined by matching simulations of the x-ray diffraction patterns with the diffracted intensities found experimentally. Approximately 10–20% of the indium is present in the cubic form and the remainder is the stable tetragonal phase.