bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rf Magnetron Sputtering Epitaxially Grown (Pb,La)TiO3 Thin Films on (0001) A12O3 and (001) SrTiO3 for Nonlinear Optical Applications
Authors: Rabibisoa U. , Agius B. 
Published: April 2011

AbstractFerroelectrics are known to be excellent materials for nonlinear optics. Miniaturization of circuits using these materials requires an optimization of structural and morphological properties of thin films, to minimize optical losses. The first condition is the use of epitaxially grown thin films. The second one is the optimization of the morphological properties, in particular the roughness at the air/film and film/substrate interfaces must be the lowest possible.The aim of this work is to study the effect of the deposition atmosphere on these properties for PLT thin films grown on (0001) A12O3 and (001) SrTiO3.
Crystallinity and Surface Morphology of Epitaxial (Sr,Ba)Nb2O6 Thin Film Prepared by Pulsed Laser Deposition with Two-Step Growth Sequence
Authors: Nakagawara Osamu , Shimuta Toni , Tanaka Katsuhiko , Katayama Yuzo 
Published: April 2011

AbstractWe have prepared epitaxially grown SBN thin film with c-axis orientation by an ArF pulsed laser deposition on SrTiO3(100). Pole figures show that the SBN film has a twin structure aligned at ±18.4: with the a-axis of SrTiO3. The epitaxial relationship of SBN<310> //SrTiO3 < 100 > is determined. The lattice mismatch between SBN and SrTiO3 is approximately 0.9%, which contributes to the desirable crystallinity of the SBN thin film. Furthermore, we have tried to form the SBN film with a two-step growth sequence in order to improve surface morphology. The amorphous initial growth region of 5 monolayers (2 nm thickness) is prepared with no substrate heating followed by post-annealing treatment at 720°C and additional growth on the initially crystallized layer. RHEED patterns of the SBN film with the two-step growth sequence have remained streaky throughout the film formation, compared with spotty patterns observed from films prepared by a conventional sequence. Atomic force microscope (AFM) images show that both the initial stage and final stage have extremely flat surfaces of rms≦ lnm which is a remarkably improved figure compared with the roughness rms ≧3nm for the film deposited at 720°C from the initial stage. These results suggest that the two-step growth sequence makes it possible to improve surface morphology to a nanometer level.
Structural Characterization of Pulsed Laser Deposited Ktn Thin Films
Authors: Savvinov A. A. , Siny I. G. , Katiyar R. S. , Pumarol M. , Mourad H. A. , Fernandez F. E. 
Published: April 2011

AbstractThe renewed interest in KTa1−xNbxO (KTN) mixed perovskite materials, especially in thin films of a high quality, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO3 lattice provide a drastic increase in the dielectric peak up to 20 times in comparison with pure KTaO3 and KNbO3. We prepared KTN thin films with several Nb concentrations in the range of 0 ≤ x ≤ 1 by pulsed laser deposition from semented KTaO3, KNbO3 and KNO3 targets. The effect of the substrate and symmetry-breaking defects was studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk Tc value. On the whole, the KTN film behavior shows the existence of specific defects enlarging the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above Tc.
Anomalous Diffusion in Membranes
Authors: Granek R. , Pierrat S. , Zilman A. G. 
Published: April 2011

AbstractWe study the undulations and the transverse diffusion of a tagged membrane point in both physical (passive) membranes and active biomembranes. In physical membranes thermal undulations generate a transverse subdiffusive motion, 〈r2〉 ∼ t2/3. Active biomembranes include active sites that use chemical energy to pump ions or molecules from one side to the other. In this case we find a few regimes which show a strongly enhanced diffusion, 〈r2〉 ∼ tα with 1 < α > 2.
Dielectric and Mechanical Relaxation of Glass-Forming Liquids in Nanopores
Authors: Wendt H. , Richert R. 
Published: April 2011

AbstractWe have measured the time resolved phosphorescence of different probe molecules in glassforming solvents under the condition of geometrical confinement in porous glasses. This solvation dynamics technique probes the local dielectric relaxation in the case of a dipolar chromophore in polar liquids. In the absence of dipolar interactions, the observed Stokes shifts reflect the local density or mechanical responses. Therefore, both orientational and translational modes of molecular motions can be measured for liquids imbibed in porous silica glasses. The effect of confinement on the relaxations of supercooled liquids is strongly dependent on the surface chemistry and can be rationalized on the basis of the cooperativity concept. As in the bulk case, we find that the relaxations in nano-confined liquids display heterogeneous dynamics. The density relaxation turns out to be more sensitive to the thermal history relative to the orientational features of molecular motion. By selectively positioning the chromophores at the liquid/solid interface, we observe also that the structural relaxation of the liquid in the immediate vicinity of the glass surface is slowed down but not entirely blocked.
Rotational Diffusion of Microconfined Liquids
Authors: Loughnane Brian J. , Farrer Richard A. , Fourkas John T. 
Published: April 2011

AbstractThe orientational behavior of liquids confined in nanoporous glasses has been studied using ultrafast Optical Kerr Effect spectroscopy. We discuss the detailed microscopic behavior of a weakly wetting liquid (methyl iodide) and a strongly wetting liquid (acetonitrile) confined in these glasses. We demonstrate that the behavior of methyl iodide is dominated by geometrical effects while the behavior of acetonitrile is dominated by surface interactions. We provide evidence that molecular exchange into the bulk is an important channel for the reorientation of strongly wetting liquids at interfaces.
Comparative Thermodynamic Behavior of Physically Restricted Cyclohexane and Cyclohexanone in Porous Silica
Authors: Amanuel S. , Malhotra V. M. 
Published: April 2011

AbstractWe undertook comparative differential scanning calorimeter (DSC) measurements on cyclohexane (C6H12) and cyclohexanone (C6H10O), physically confined in porous silica of pore radius 4, 7.5, 15, 30, and 62.5 nim, with a view to ascertain how guest fluid-surface host interactions affected the thermodynamic properties of the confined fluids. Our results can be summarized as follows: (a) No distinct signature of freezing or melting transition was observed for the physically confined cyclohexanone, irrespective of whether the bulk was present outside the pores. However, this was not the case for cyclohexane. (b) The solid-to-solid transition temperature of cyclohexane and cyclohexanone inversely scaled with the pore radius of the host porous silica. (c) The cubic-to-orthorhombic transition of cyclohexanone was strongly influenced by whether the bulk fluid was present outside the pores. In the absence of the bulk, the transition temperature was considerably suppressed relative to the bulk transition temperature. However, in the presence of the bulk, the confined and the bulk transitions occurred at the same temperature.
Nano-Scale Mechanical Characterization of Plasma Treated Polymer Surfaces
Authors: Dahl S. , Klemberg-Sapieha J. E 
Published: April 2011

AbstractRecent advances in atomic force microscopy (AFM) allow one to perform complex analysis of materials surfaces and near-surface regions with a nanometer scale resolution; this includes the imaging of surface topography and the measurements of stiffness, elasticity, hardness and nano-tribological characteristics. Understanding of the complex AFM response is still in its early stage, and it frequently requires the use of multiple complementary techniques. In the present work we have applied AFM for the study of the surface and nearsurface mechanical properties of plasma-treated polycarbonate. The results from AFM analysis, such as the stiffness and the relative Young modulus, were compared with the hardness values obtained by depth-sensing indentation and by the micro-scratch technique. The characteristics of the observed hardened surface layer are discussed with respect to the role of the “interphase” in adhesion en1hancement of plasma-deposited films on polymers.
H-Atom Assisted jet Vapor Deposition of Parylene-n polymer
Authors: Halpern B. L. , Komarenko P. , Graves R. F. , Fuqua P. D. , Mcdonald J. F. , Yang G.-R. , Wang L. , Lu T. M. , Tomozawa M. , Maitthew I. 
Published: April 2011

AbstractWe describe a new approach to deposition of Parylene N thin films. It utilizes a small scale, sonic speed, Jet Vapor DepositionTM (JVDTM) process technology in place of the conventional larger scale, slow flow, Gorham apparatus. It employs a simple but powerful strategy to promote radical polymerization: exposure of the growing film, during deposition, to a high flux of atomic hydrogen. We believe that H atoms have two effects: they clean oxygen from the substrate, and they promote crosslinking in the Parylene film by abstraction of H atoms from the Parylene ring or side groups. With “H atom assisted JVD” Parylene N deposits and adheres even on warm substrates; it has reduced index of refraction and dielectric constant.
Characterization of Plasma-Deposited Au/Fluoropolymer Nanocomposite Films for Nonlinear Optical Application
Authors: Dalacu D. , Brown A. P. , Klemberg-Sapieha J. E. , Martinu L. , Wertheimer M. R. , Najafi S. I. , Andrews M. A. 
Published: April 2011

AbstractNanocomposite films consisting of gold nanoclusters embedded in a fluorocarbon matrix were prepared by simultaneous plasma polymerization of a fluorocarbon gas and magnetron sputtering of a gold target. The optical constants of the films were determined using variable angle spectroscopic ellipsometry (VASE). The Maxwell-Garnett (M-G) effective medium theory (EMT) was used to extract the microstructural characteristics (gold volume fraction, cluster size). The predictions of the M-G EMT were compared with the results from x-ray photoelectron spectroscopy. Angle-resolved measurements suggest the presence of a carbonaceous layer at the cluster surface. The presence of such a layer is discussed in the context of its influence on the validity of the optical model
Low k Film Etch in Applied Materials eMxP+ Chamber
Authors: Yu Melissa , Shan Hongching , Taylor Ashley 
Published: April 2011

ABSTRACTThe materials with lower dielectric constant ( low k ) have been attracting attention recently because the low k material has the potential to be used in place of SiO2 in ULSI. In this work, we focused on evaluating organic low k material performance with plasma etch in the Applied Material's eMxP+ anisotropic etch chamber. The films studied were Dow Chemical BCB and Silk, Allied Signal Flare 2.0, and Du Pont FPI. The feature sizes of the wafer s were 0.25 to 1 micron trenches.
Du Pont FPI resulted in the highest achieved etch rate of more than lum/min, followed by BCB, and Flare. The microloading study indicated that the etch rate microloading is less than 10% between lum and 0.25 urn feature sizes, which suggests that the chance of etch stop for a high aspect ratio features will be small. The profile could vary from bowing to vertical, to tapering by using different process conditions, mainly by temperature. The FP1 profile was more tapered than those of BCB and Flare when the same process was used to etch the same type of patterned wafer having these three different low k films. The detailed study showed that the trend of etch rate and profile for BCB and Flare film etch were similar, but that the absolute value for profile, as well as the trend of etch rate uniformity and profile were somewhat different. In conclusion, low k materials can be etched in AMAT traditional dielectric chamber (eMxP+) with a good etch rate and profile control.
The Effects of Strain Rate and Minor Baron Addition on Brittle-to-Ductile Transition Temperature in Gamma TiAl Alloy
Authors: Lin(T. L. Lin) Dongliang , Wang Yu , Liu Junliang , Law Chi C. 
Published: April 2011

ABSTRACTBrittle-to-ductile transition (BDT) temperature (TBD) was evaluated according to temperature dependence of tensile properties under different strain rates from 10−5to 10−1s−1in two-phase Ti-47Al-2Mn-2Nb and Ti-47A1–2Mn-2Nb-0.8 TiB2alloys with nearly lamellar microstructure. Based on the strain rate dependence of the determined TBD values, apparent BDT activation energies were determined using Zener-Hollomon factor. Tensile fracture surfaces were observed using a scanning electron microscope while deformation substructures were investigated by transmission electron microscopy. It was found that the BDTT of both alloys increased sharply with the strain rate and that the minor addition of 0.8 vol% TiB2reduced TBD by about 100K at the same strain rate. The TiB2addition also decreases the apparent BDT activation energy from 324 to 256 kJ/mol. Both of these values approximate to self- or inter-diffusion of Ti and Al atoms in TiAl phase. Transgranular fracture and dimple fracture were found dominant in fracture surfaces below and above TBD, respectively. The most common 1/2<110] ordinary dislocations were found to begin climb at mound TBD. All this evidence, as well as a theoretical calculation using the Nabarro Model, add up to a conclusion that the BDT is controlled by dislocation climb in both alloys.
Microstructure of Rolled Ti-46.5Al-4(CrNb,Ta,B)
Authors: Inkson B. J. , Clemens H. 
Published: April 2011

ABSTRACTAn industrial Ti-46.5A1–4(CrNb,Ta) alloy, with and without boron additions, has been successfully rolled to sheet 1.5mm thick. The microstructure of the sheet material has been characterised as a function of boron content and subsequent heat treatments. It is observed that rod-like (Ti-Ta)B precipitates are effective in refining the grain structure in both as-rolled and subsequently heat treated material. As-rolled microstructures rapidly cooled from the α + γ phase field contain unstable α2, which transforms to B2 phase on annealing below the α + γ tranus. Annealing in the α-phase field can result in a designed fully lamellar microstructure.
Infrared Joining of Titanium Aluminides by Using Ti-15Ni-15Cu Foil
Authors: Lee S. J. , Wu S. K. 
Published: April 2011

ABSTRACTThe infrared joining of titanium-aluminides Ti50A150, Ti60Al40and Ti70A130at Tw= 1100∼1200°C for 30–60sec using Ti-15Cu-15Ni foil as brazing filler-metal was investigated. Multilayered structures are formed by isothermal solidification following solid-state interdiffusion. The diffusion of Al atoms is the main controlling factor pertaining to the microstructural evolution of the joint interface. Seven characteristic zones at Twcan be distinguished in the Ti50Al50joint: γ-TiAl (I and II), α + β two-phase mixed, high Al% α-phase, α2-Ti3Al, β-Ti and residual liquid filler-metal. Five characteristic zones at Tw, are obtained in the Ti70A130joint: α2-Ti3Al, α2+ β two-phase mixed, α + β two-phase mixed, β-Ti and residual liquid filler-metal. The observed joint microsturctures at room temperature are obtained from the phase transformation of these well-established high-temperature phases during cooling. A step-by-step microstructural evolution mechanism at Tw= 1150°C is proposed individually for Ti50A150and Ti70A130alloys. These steps are in good agreement with the observed microstructures and are consistent with the multiphase diffusion theories in solid-state systems. The microstructural evolution of Ti60A140joint interfaces can also be explained by the proposed step mechanisms for Ti50A150and Ti70A130alloys.
Electron Diffraction Study on the Crystal Structure of a Ternary Intermetallic Compound Co3AICx
Authors: Mishima Yoshinao , Hwang Keurn-Yeon , Wei Fu-Gao 
Published: April 2011

ABSTRACTIntermetallic compound Co3A1Cx, or called ic-phase, has been reported to assume the E21, or Perovskite structure. In the present work its crystal structure is critically reinvestigated in the two-phase alloys containing κ-phase in the Co primary solid solution matrix, α(Co), using conventional electron diffraction. It is shown that the crystal structure of κ-phase is a derivative of E21 being a cubic structure composed of eight E21 sub-unit cells in a half of which the body center sites are not occupied by carbon atoms. As a result, its space group is Fm3m and the chemical formula should be Co3AIC0.5. It is also found that the lattice parameter of the phase is about twice as large as that of α(Co). Orientation relationship of the κ-phase with the matrix α(Co) is found to be similar to the case for the γ' phase with the fcc γmatrix in a Ni-base superalloy since three orthogonal axes of κ-phase are parallel to those of α(Co). Lattice misfit under this orientation relationship between the two phases is found to be about 2.5%.
A T.E.M. Study of the Microstructure of a Ti48Al48Cr2Nb2 Alloy
Authors: Zghal S. , Thomas M. , Naka S. , Couret A. 
Published: April 2011

ABSTRACTThe microstructures of as cast and air quenched Ti48Al48Cr2Nb2 alloys are analysed by transmission electron microscopy. Statistical analyses on the orientation variants and on the orientation relationships at the interfaces are presented. The results are used to have a better understanding on the formation mechanism of the lamellar microstructure.
Strength and Fracture Behavior of Aluminide Matrix Composites with Ceramic Fibers
Authors: Inoue M. , Suganuma K. , Niihara K. 
Published: April 2011

ABSTRACTThis paper investigates the fracture behavior of FeAl and Ni3AI matrix composites with ceramic continuous fibers 8.5–10 μm in diameter. When stress is applied to these composites, multiple-fracture of fibers predominately occurs before matrix cracking, because the load carried by the fibers reaches their fracture strength. Fragments which remain longer than the critical length can provide significant strengthening through load bearing even though fiber breaking has occurred. The ultimate fracture strength of the composites also depends on stress relaxation by plastic deformation of the matrix at a crack tip in the multiple-fractured fibers. Ductilizing of the matrix by B doping improves the ultimate strength at ambient temperatures in both composites. However, their mechanical properties at elevated temperatures are quite different. In the case of Ni3AI matrix composites, embrittlement of the matrix is undesirable for high strength and reliability at 873–973 K.
Microstructure and Mechanical Properties of Nb-Al-N and Nb-Si-B Powder Compacts Produced by Spark Plasma Sintering
Authors: Murakamia T. , Kitaharab A. , Kawahara M. , Takahashid Y. , Inui H. , Yamaguchie M. 
Published: April 2011

ABSTRACTNb-Al-N and Nb-Si-B powder compacts were prepared by spark plasma sintering, and their microstructure, mechanical properties and oxidation behavior were investigated. Adding nitrogen was easily done by blending or mechanically alloying Nb and AIN powders and then sintering them. The addition of nitrogen caused the formation of Nb2N in all the Nb-Al-N compacts and Nb2N and Nb3Al2N in compacts with high aluminum and nitrogen contents. The highest room-temperature hardness and the highest yield stress at 1473K were observed for compacts consisting of Nb2N and Nb3Al2N and those consisting of Nb2N and Nb2Al, respectively. Nb-Si-B compacts were prepared from elemental powders. Two or three of NbB2, Nb5Si3, Nb5Si3B2 and NbSi2 phases were identified as constituent phases of Nb-Si-B compacts depending on composition unless a large amount of silicon is consumed by forming SiO2. Contributions of NbB2, NbSi3 and Nb5Si3B2 phases to room-temperaturehardness and yield stress at 1973K were much larger than those of NbSi2. However, the oxidation resistance of Nb-Si-B compacts increased with increasing the volume fraction of NbSi2.The oxidation resistance of NbSi3B2 was better than that of NbSi3, but was not as good as that of NbSi2.
Hydrogen Sites In The α(TiCrSiO) 1/1 Approximant Phase
Authors: Kim J. Y. , Kim W. J. , Yelon W. B. , Gibbons P. C. , Kelton K. F. 
Published: April 2011

AbstractCrystal approximant phases are important because they are believed to have a similar local atomic structure to corresponding quasicrystals. Interstitial hydrogen is used as a probe of the local structures of the Ti-based quasicrystals and crystal approximants. Phase pure samples of ct(TiCrSiO), a Mackay type 1/1 crystal approximant, which were plasma etched and coated with a thin layer of Pd, were loaded with deuterium from the gas phase to a maximum deuterium atom to metal atom ratio (D/M) of 0.26. After deuteration, the sample becomes a fine powder and remains single-phase. A Rietveld structural refinement of powder x-ray and neutron diffraction data was made to determine the location of the interstitial sites. For the fully deuterated sample the deuterium atoms sit at both octahedral and tetrahedral sites. The octahedral sites are formed by six Ti atoms in the first and second shells of the icosahedra. Deuterium atoms are also located at the tetrahedral interstitial sites formed between the clusters along <100> directions. In the partially loaded samples with DiM = 0.11, the deuterium atoms occupy only octahedral sites, demonstrating a preference for these sites.
Chemical Disorder And Columnar Vacancies In Ideal Decagonal AL-NI-CO Quasicrystals
Authors: Yan Yanfa , Pennycook S. J. , Tsai A.-P. 
Published: April 2011

AbstructAtomic-resolution Z-contrast images provide conclusive evidence for chemical disorder in an ideal Al-Ni-Co quasicrystal. The so-called basic Ni-rich, high-temperature, quasiperiodic structure exhibits chemical disorder at the center of the 2 nm diameter clusters that involves both the Al and Ni(Co) atoms. The atomic structure of the 2 nm clusters is derived directly from the images and differs from previous models. The presence of closely-spaced, half-occupied atomic columns (or columnar vacancies) in specific rings within the clusters is directly observed. We propose that these columnar vacancies mediate the phason flips necessary for transformation to random tiling.
Nano-Quasicrystalline Particles In Mn-Ion Implanted GaAs
Authors: Sun K. , Zhu S. , Kuo K. H. 
Published: April 2011

AbstractBoth icosahedral and decagonal quasicrystalline particles of a few tens of nanometers in size have been found in Mn-ion implanted GaAs single crystals with a dose of 8×1016 Mn+/cm2 by high resolution electron microscopy (HREM). The identity of these quasicrystals was confirmed by the Fourier transforms made from these HREM images and their composition measured by micro-probe X-ray analysis and electron energy loss spectroscopy was 38–45 at.%Mn, the rest being Ga. The orientation relations among the icosahedral quasicrystal (i), the decagonal quasicrystal (d), and the GaAs matrix found by both HREM images and their Fourier transforms are: i- 5 // d-10 // GaAs[110] or [114]. In addition, nano-particles of a cubic, a hexagonal, and an orthorhombic Ga-Mn crystalline approximant have also been found in the GaAs matrix.