bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Thin Film Growth using Glancing-Angle Ions
Authors: Barnett Scott A. , Ruthe Kurt C. , Deluca Paul M. 
Published: April 2011

AbstractThis paper reviews the use of glancing-angle ions for modifying surfaces and thin film growth processes. Ions impinging on a flat surface at oblique incidence angles are mostly reflected without penetrating, providing very low sputtering rates along with minimal damage and implantation. They also provide a unique selectivity, where ion energy is coupled to defects or rough portions of the surface, while flat portions are essentially unaffected. This allows one to clean contaminated surfaces and smoothen rough surfaces, with little or no ion damage. In addition, recent results indicate that the ion energy couples directly to adatoms during epitaxial growth of GaAs(001). This was observed by a decrease in the time required for diffusion across terraces on a vicinal GaAs surface, as the glancing-angle Ar ion current was increased. It was also found that ion-enhanced diffusion shifted the growth mode from two-dimensional island nucleation to step-flow growth, and resulted in flatter growth surfaces. Finally, glancing-angleions can be used to introduce biaxial texture into polycrystalline GaAs films.
Characterization of the Interface Between Lanthanum Hexa-Aluminate and Sapphire by Exit Wave Reconstruction
Authors: Wessler B. , Steinecker A. , Mader W. 
Published: April 2011

AbstractEpitaxial thin films of rare-earth hexaaluminates on basal plane sapphire have been produced by chemical solution deposition. LaAl11O18 films with magnetoplumbite structure grow with (0001)HA||(0001)S and [1100]HA||[2110]s orientation relationshipTo investigate the stucture of the interface exit wave reconstruction of focus series was carried out using a field emission TEM. Due to the inversion of the imaging process major artefacts at the interface can be eliminated. Exit waves were simulated based on different interface models and were compared with the reconstructed waves to localize the positions of the atoms at the interface. Two different types of interfaces were observed in the samples. One of the types, in which the spinel block of hexaaluminate faces the sapphire with the mixed cation layer with occupied octahedra and tetrahedra, is characterized in detail. Face-sharing of coordination polyhedra is avoided to large extent
Structural Study of a [100] 45° Twist Plus 7.5° Tilt Grain Boundary in Aluminium by HREM
Authors: Shamsuzzoha M. , Deymier P. A. , Smith David J. 
Published: April 2011

AbstractA [100] 45° twist plus 7.5° tilt grain boundary in aluminium prepared by cold rolling and annealing has been studied by high-resolution electron microscopy. The direct interpretability of the image features in terms of atomic column positions allows structural models of the grain boundary to be developed. The boundary exibits a high concentration of steps due to the 7.5° tilt from a perfect [100] 45° quasiperiodic misorientation. Occurrence of co-incidence and pseudo co-incidence of atomic planes across the interface appears to play an important role in the formation of steps along this boundary. Local relaxation of atoms resulting from the perturbation of the [100] 45° twist bi-crystal determines the boundary structure
Atomic Structure of Gold and Copper Boundaries
Authors: Hetherington C.J.D. 
Published: April 2011

AbstractA very thin bicrystal film, prepared by depositing gold onto a {111} germanium substrate, then annealing and removing it, has been studied by HREM. The crystals grow predominantly in the orientations {111} and (111) which are related by a 60° rotation (Σ3 CSL) and bounded by {121} facets. In contrast to the boundaries studied in thicker films, these {112} facets extend through the depth of the film. Another crystal within the film also had a {111} orientation, but rotated by around 20° from the other crystals. A short length of boundary was found that was edge-on, symmetrical, facetted on (213) planes, and corresponding to Σ;7 (or Σ;21). A copper 1111 film did not show edge-on boundariesThe rigid body translation across the facets were measured and found to vary depending on the proximity to facet junctions. An expansion at the boundary was the general case
Bonding in Ion-Implanted Carbon Films Characterized by TEM Spectrum Lines and Energy-Filtered Imaging
Authors: Bentley J. , Walter K.C. , Evans N.D. 
Published: April 2011

AbstractIon-implanted diamond-like carbon (DLC) films have been characterized by techniques based on electron energy-loss spectrometry using an imaging energy filter on a 300kV TEM. Nitrogen implantation results in increased sp2 bonding and a 1.3 eV shift to higher binding energies for carbon-K. Argon implantation results in a smaller increase in sp2bonding with no detectable binding energy shift. The fraction of implanted species retained is much smaller for Ar than for N. Differences in behavior between N- and Ar-implanted DLC are consistent with expected chemical reactions. Preliminary results demonstrate the feasibility of mapping the Φ*/σ* intensity (sp2/sp3) ratio by energy-filtered TEM as an alternative to spectrum imaging in STEM mode
Surface Sensitivity Effects With Local Probe Scanning Auger-Scanning Electron Microscopy
Authors: Agterveld D. T. L. Van , Palasantzas G. , Hosson J.Th.M. De 
Published: April 2011

AbstractUltra-high-vacuum segregation studies on in-situ fractured Cu-Sb alloys were performed in terms of nanometer scale scanning Auger/Electron microscopy. S contamination leads to the formation of Cu2S precipitates which, upon removal due to fracture, expose pits with morphology that depends on the precipitate size and shape. Local variations of S and Sb distributions inside the pits were correlated to local surface orientations as Atomic Force Microscopy analysis revealed.
Hydrogen Storage in Single-Walled and Multi-Walled Carbon Nanotubes
Authors: Lee Seung Mi , Frauenheim Thomas , Elstner Marcus , Hwang Yong Gyoo , Lee Young Hee 
Published: April 2011

ABSTRACTWe performed density-functional calculations to search for adsorption sites and predict maximum hydrogen storage capacity in carbon nanotubes. Our calculations show that the storage capacity of hydrogen, limited by the repulsive forces between H2 molecules inside nanotubes, increases linearly with tube diameters in single-walled nanotubes, whereas this value is independent of tube diameters in multi-walled nanotubes. We predict that H storage capacity in (10,10) nanotubes can exceed 14 wt % (161 kg H2/m3).
Hydrogenated Amorphous Carbon Deposition by Saddle-Field Glow Discharge
Authors: Zukotynski S. , Gaspari F. , Manage D. , Pletnev V. , Sagnes E. 
Published: April 2011

ABSTRACTThe saddle-field glow discharge is modeled and electron multiplication and energy spectra are presented. The roles of the ion substrate current and ion energy at the substrate on the growth rate, hydrogen content, sp2 content and energy gap are discussed and the effects of atmospheric aging and high temperature annealing are described.
Nanocrystalline and Hard, Boron-Alloyed Be Coatings
Authors: Jankowski A. , Ramsey P. , McKernan M. , Morse J. 
Published: April 2011

ABSTRACTBoron-alloy coatings can be formed by sputtering compound targets, through co-deposition with other elemental targets, by utilizing reactive gas mixtures, and/or by post-deposition implantation. Specific to this study, boron-alloy coatings are assessed with respect to composition as deposited by co-sputtering boron and beryllium. Transmission electron microscope (TEM), bright-field images with selected area diffraction are used to reveal the microstructure and phase. Refinement in grain size to the nanoscale occurs through boron addition as well as transition metal impurities. An increase in coating hardness with boron addition is measured using nanoindentation. Scanning electron microscope (SEM), secondary electron images reveal the surface morphology variations for thick coatings that occur with boron addition as measured using energy dispersive spectrometry (EDS). The phase formed in boron-alloyed beryllium coating is found to be dependent on both coating composition and the sputter deposition conditions. It is concluded that the geometry of the deposition sources with the configuration of the substrate effect the coating composition, microstructure, and properties
Effects of CF4 Addition on the Growth of Amorphous CNx Films by Plasma Decomposition of CH4-N2 Gas Mixtures
Authors: Inokuma T. , Matsumoto H. , Kurata Y. , Hasegawa S. 
Published: April 2011

ABSTRACTHydrogenated amorphous carbon nitride (α-CNx:H) films are deposited at 50–300°C by radio-frequency plasma decomposition of CH4-CF4-N2 gas mixtures. Effects of fluorine radicals on the deposition rate, composition, and on chemical bonding are investigated. When CF4 gas is added as partial replacement of CH4 gas, the deposition rate at 200°C steeply increases with increasing flow rate ratio RCF = [CF4]/([CH4]+[CF4]) up to ∼0.3, and then it decreases gradually. It is found that the nitrogen content, x, increases from 0.22 to 0.46 when RCF increases from 0 to 0.75. The inclusion of fluorine atoms into the films is less than 5 at%. The infrared absorption spectra shows strong enhancement of the absorption bands related to various forms of C—N bonding by the CF4 addition. It is found that the addition of CF4enhances the formation of C–N bonds in PECVD α-CNx:H films.
Structural and Electronic Characterization of Epitaxially-Grown Ferroelectric Vinylidene Fluoride Oligomer Thin Films
Authors: Ishida K. , Noda K. , Kubono A. , Horiuchi T. , Yamada H. , Matsushige K. 
Published: April 2011

AbstractThe structural and electric properties of newly synthesized vinylidene fluoride (VDF) oligomer thin films evaporated on various substrate were investigated. The structural behavior of the VDF oligomer thin films strongly depended on the kinds of substrate and substrate temperature during film preparation. In particular, the VDF oligomers epitaxially grew on KBr(001), aligned their molecular chain along the <110> direction of substrate surface, and were similar to polar Form Itype crystals of poly(VDF). While, the thin films evaporated on NaCl(001), SiO2/Si were non-polar Form II-type or mixture of both Form I- and Form II-type crystals with their molecular chain normal to the surface. These facts indicated that crystal field of substrate, based on van der Waals and electrostatic interactions, strongly influenced to ferroelectric phase transition of the VDF oligomer. In addition, we demonstrate the formation of the local polarized domains in the epitaxial crystals by applying electric pulses from a conducting AFM probe used as a positionable topelectrode, and confirm their piezoelectricity of the VDF oligomers for the first time.
Electrostrictive Grafr Elastomers and Applications
Authors: Su J. , Harrison J. S. , Clair T. L. St. , Bar-Cohen Y. , Leary S. 
Published: April 2011

AbstractEfficient actuators that are lightweight, high performance and compact are needed to support telerobotic requirements for future NASA missions. In this work, we present a new class of electromechanically active polymers that can potentially be used as actuators to meet many NASA needs. The materials are graft elastomers that offer high strain under an applied electric field. Due to its higher mechanical modulus, this elastomer also has a higher strain energy density as compared to previously reported electrostrictive polyurethane elastomers. The dielectric, mechanical and electromechanical properties of this new electrostrictive elastomer have been studied as a function of temperature and frequency. Combined with structural analysis using x-ray diffraction and differential scanning calorimetry on the new elastomer, structure-property interrelationship and mechanisms of the electric field induced strain in the graft elastomer have also been investigated. This electroactive polymer (EAP) has demonstrated high actuation strain and high mechanical energy density. The combination of these properties with its tailorable molecular composition and excellent processability makes it attractive for a variety of actuation tasks. The experimental results and applications will be presented.
A Study of Liquid Crystalline Elastomers as Piezoelectric Devices
Authors: Biggs A. G. , Blackwood K. M. , Bowles A. , Dailey S. , May Alison 
Published: April 2011

AbstractFerroelectric liquid crystalline polymer films exhibit a number of unique physical properties and have been extensively studied during the last few years. Ferroelectric polymer films exhibiting a high level of piezoelectric activity would provide a new route to piezo- and pyro-electric sensors.We report the fabrication of free-standing ferroelectric liquid crystal films which exhibit piezoelectric coefficients up to 4.4pC/N. We also report the investigation of the physical properties of these films by dynamic mechanical analysis.
A conductive composite film by permeation method
Authors: Wang Jin Wei , Srinivasan M. P. 
Published: April 2011

AbstractA new method of making conductive composite films by permeation of the conducting guest species into the host is reported. A layer of poly(3-n-dodecyl thiophene) (P3ddt) is embedded at the surface of polyimide by permeation of the monomer or polymer (in solution in tetrahydrofuran or chloroform) into a solution of polyamic acid in n-methyl pyrrolidinone or dimethyl acetamide. The resulting composites were imidised and polymerized (if necessary). Chemical imidisation yielded composite -films that retained the conducting polymer even when the composite was subjected to solvent extraction. The films were conductive upon doping with iodine and recovered conductivity when they were exposed to iodine vapor subsequent to thermal de-doping. Thermogravimetry showed that the amount of thiophene incorporated into the polyimide was higher for permeation of the polymer than that of the monomer; however, the amount of p3ddt incorporated by the latter method was still higher than the amount that could be incorporated by blending polyamic acid with p3ddt. The levels of conductivity and speed of recovery for doped films were also higher for the permeated films. Results of scanning electron microscopy suggested that the higher mobility afforded by contact in the liquid state have contributed greater entanglement between the constituents leading to higher thermal and solvent resistance of the conducting constituent. The permeation method could be adopted to form composite films in solvent systems that are not completely miscible.
Dielectric Relaxation Spectroscopic Measurements on a Novel Electroactive Polyimide
Authors: Jawad Saadi Abdul , Alnajjar Abdalla , Bader Mamoun M. 
Published: April 2011

AbstractAC electrical behavior of a novel aromatic electro-optic polyimide was investigated in the temperature range 25 °C to 300 °C and a frequency range from 1 Hz to 106 Hz. Three electrical quantities: impedance, permittivity and electric modulus are reported. The dependence of imaginary and real components of these quantities on temperature and frequency are discussed. The experimental results show that the polymer has high thermal stability below 200 °C, where the resistivity, dielectric constant and permittivity are nearly temperature-independent indicating highly rigid structure. Above this temperature, however, a well-defined broad peak corresponding to a relaxation process was observed for which the activation energy was calculated to be 8.5 Kcal/mole. This relaxation is associated with a restricted local rotational motion of the side chain chromophore.
Ferroelectric and Piezoelectric Properties of Blends of Poly(Vinylidene Fluoride Trifluoroethylene) and a Graft Elastomer
Authors: Su J. , Ounaies Z. , Harrison J. S. 
Published: April 2011

AbstractA piezoelectric polymeric blend system has been developed. The system contains two components: ferroelectric poly(vinylidene fluoride-trifluoroethylene) and graft elastomer. The remanent polarization, Pr, and the piezoelectric strain coefficient, d31, of the blends have been studied as a function of relative composition of the two components, temperature and frequency. Both blended copolymer and graft unit in the elastomer contribute to the total crystallinity of the blend-system, and hence to the remanent polarization and piezoelectricity. The piezoelectric strain coefficient, d31, of the blend systems shows dependence on both the remanent polarization and the mechanical stiffness, which in turn are determined by the fraction of the two components in the blends. This mechanism makes it possible for the piezoelectric strain response of the blend to be tailored by adjusting the relative composition. Although Pr of the copolymer is higher than that of the blends, the blend films containing 75 wt.% copolymer exhibit a higher d31 at room temperature, possibly due to their lower modulus. The blend films containing 50 wt.% copolymer exhibit a constant value of d31, from room temperature to 70°C.
Superplasticity of Liquid-Phase Sintered β-SiC
Authors: Nagano T. , Kaneko K. , Zhan G.D. , Mitomo M. 
Published: April 2011

AbstrtactThe compression and the tension tests of liquid-phase sintered β-SiC fabricated by hot-pressing using ultra fine powders were performed at 1973 K ∼ 2048 K in N2 atmosphere. Amorphous phases were observed at the grain boundaries and at multi-grain junctions in the assintered material. Strain hardening was observed under all experimental conditions. Stress exponents in the compression test were from 1.7 to 2.1 in the temperature ranging from 1973 K to 2023 K. A maximum tensile elongation of 170 % was achieved at the initial strain rate of 2 Χ 10−5 s−1 at 2048 K.
Effects of Crystallographic Texture on Internal Stress Superplasticity Induced by Anisotropic Thermal Expansion
Authors: Kitazono K. , Hirasaka R. , Sato E. , Kuribayashi K. , Motegi T. 
Published: April 2011

AbstractPolycrystalline materials having crystallographic anisotropy show internal stress superplasticity under thermal cycling conditions. The deformation mechanism is analyzed using a theoretical model based on continuum micromechanics including the effects of crystallographic texture. The model is experimentally verified through the thermal cycling creep tests using polycrystalline zinc having two kinds of fiber-texture, and agrees well with the experimental results.
The Microstructure and Superplastic Behavior of Clean Mechanically Alloyed Titanium–Titanium Boride Alloys
Authors: Brown A.P. , Brydson R , Hammond C. , Wisbey A. , Godfrey T.M.T. 
Published: April 2011

AbstractThe superplastic forming (SPF) of titanium alloys is an established technology. A reduction in grain size from that of the typical sheet materials would lead to enhanced SPF properties and hence a reduction in production cycle times. This study describes the microstructural development and superplastic behaviour of fine-grained Ti-6%Al-4%V alloys. Ball-milling Ti-6%Al-4%V powder produces a nanocrystalline material; however on consolidation by hot isostatic pressing rapid grain growth occurs. Addition of boron powder during milling leads to boride precipitates in the matrix of the consolidated alloy. The precipitates are dispersed inhomogeneously, resulting in localized grain refinement. Superplastic testing revealed cavitation formation but in comparison to conventional sheet material, large elongations were achieved at relatively high strain rates.
Grain Refinement of Aluminum using Equal-Channel Angular Pressing
Authors: Horita Z. , Furukawa M. , Nemoto M. , Langdon T.G. 
Published: April 2011

AbstractUsing the technique of equal-channel angular (ECA) pressing, it is possible to reduce the grain size of polycrystalline materials to the submicrometer level. Thus, this processing technique has the potential for producing materials which may exhibit superplasticity. This paper describes various factors affecting the development and evolution of the microstructure produced by ECA pressing. Optimization of such factors is then presented for the advent of superplasticity.
Texture Evolution During Low-Temperature Superplasticity in 5083 and 5052 Al-Mg Alloys
Authors: Su S.W. , Hsiao I.C. , Huang J.C. 
Published: April 2011

Absyract:Low temperature superplasticity (LTSP) at 250°C and 1×10−3 s−1 was observed in the 5083 Al-Mg base alloy after thermomechanical treatments (TMT). With increasing TMT rolling strain, the high angle grain boundary fraction increased, more favorable for the further operation of grain boundary sliding and LTSP. The strong texture components and bimodal misorientation distributions present after TMT were not affected by static annealing at 250 °C but evolved gradually into a random orientation distribution during LTSP straining from 30% to 100%. When the LTSP elongation was greater than 150%, the macro-deformation anisotropy R ratio would finally reach a stable level. It seems that the LTSP performance was controlled by a large fraction of high angle boundaries, but not by the special coincidence site lattice boundaries.
High Hf Content NITIHF Shape Memory Films
Authors: Zhang Chen , Thoma Paul E. , Zee Ralph 
Published: April 2011

AbstractPolycrystalline NiTiHf films with around 9at% Hf have been successfully deposited from a single NiTiHf target using a DC magnetron sputtering system. Free standing films were obtained by depositing the films on single crystal silicon substrates. Thickness of the films was controlled between 10-12µm. In this investigation, the effects of deposition temperature on the crystallinity and transformation temperatures of the films were studied. Substrate temperature during deposition was varied between 300°C and 700°C at 100°C intervals. The influence of heat treatment temperature on the properties of the films was also investigated. The heat treatment temperature was between 300°C and 800°C at 100° C intervals. Transformation temperatures of these films were determined by differential scanning calorimetry (DSC). The crystallinity was determined using x-ray diffractometry. It was found that all the as-deposited films were crystalline even when the substrate temperature was as low as 300°C. Both martensite and austenite transformation temperatures increase with increasing substrate temperature and increasing heat treatment temperature.
Investigation of Wear of Microelectromechanical Contacts
Authors: Gally Brian J. , Abnet C. Cameron , Brown Stuart 
Published: April 2011

AbstractA test system has been assembled to examine factors controlling the reliability of microdevice switching. The system consists of a spherically tipped sputter-coated post driven by a piezoresistive actuator into a sputter-coated micromechanical membrane. Contact forces are calculated based upon the measured deflection of the micromechanical membrane, which is induced by post actuation. Membrane deflection is measured using white light interferometry. The known geometry of the membrane and probe tip permits the estimation of contact area and, hence, contact pressure. Preliminary testing of sputtered gold contacts resulted in localized melting, material transport to the membrane and failure of contact surfaces at relatively low contact pressures and current densities. Further testing will examine the factors governing the reliability of microdevice contacts, such as material properties, contact pressure and current density.