bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Microstructure and Properties of Framework Zirconium Phosphates Based Nanocomposites -Catalysts of Alkane Isomerization
Authors: Sadykov Vladislav A. , Pavlova S. N. , Zabolotnaya G. V. , Maximovskaya R. I. , Kochubei D. I. , Kriventsov V. V. , Odegova G. V. , Ostrovskii N. M. , Bel'skaya O. B. , Duplyakin V. K. , Zaikovskii V. I. , Paukshtis E. A. , Burgina E. B. , Tsybulya S. V. , Chaikina M. V. , Kuznetsova N. N. , Lunin V. V. , Roy R. , Agrawal D. K. 
Published: April 2011

ABSTRACTThe structure and surface properties of composites based upon high-surface-area framework zirconium phosphates with supported WO3, MoO3 and Pt nanoparticles were studied by using combination of structural and spectral methods. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered.
XPS Study of Pt/CexZr1−xO2/Si Composite Systems
Authors: Norman A. , Sporken R. , Galtayries A. , Mirabella F. , Keveney K. , Pijolat M. , Baker R. , Bernal S. 
Published: April 2011

ABSTRACTThis work describes the study of the surface reduction of ceria zirconia mixed oxides (CeZrO) as either thin films or powders, both with and without Pt present. XPS was used to measure the composition of the surface and the oxidation states of all metals contained within the material. The thin films of CeZrO showed little reactivity towards the reducing conditions used. Grazing incidence angle XRD showed the presence of Ce0.75Zr0.25O2. The thin films prepared with Pt showed that surface reduction of Ce4+ occurred under reducing conditions. The size of the Pt clusters was also determined from the data. The Pt was found to always exist in the metallic state. The Zr4+ was not seen to change during all treatments. For the powder samples the Ce4+ was readily reduced to approximately 60%. Pt was found to be initially oxidised with the % of metallic Pt increasing with reduction temperature. Again no change in the Zr was observed.
Atomic Scale Characterisation of Electrodeposited Nanocrystalline Ni-P Alloys
Authors: Abraham Matthias , Thuvandert Mattias , Lane Helen M. , Cerezo Alfred , Smith George D.W. 
Published: April 2011

ABSTRACTNanocrystalline Ni-P alloys produced by electrodeposition have been characterised by three-dimensional atom probe (3DAP) analysis. In the as-deposited materials, there are indications of some variation in P concentration between grains and segregation to grain boundaries. After heat treatment however, strong grain boundary segregation and the formation of Ni3P precipitates have been observed.
Insulator-Metal Transition in Nanostructured Ni-Al Thin Films
Authors: Ng H.P. , Ngan A.H.W. 
Published: April 2011

ABSTRACTThe electrical resistance of Ni-Al alloy thin films prepared by dc magnetron sputtering process was found to be abnormally high at room temperature. However, when heated at elevated temperatures, the resistance dropped significantly, exhibiting a remarkable negative temperature coefficient of resistance (TCR). The phenomenon was found to be substrate-independent. Cross-sectional transmission electron microscopy revealed that the films were essentially nanocrystalline and porous in nature. Analysis of the current density-electric field characteristics yielded a satisfactory agreement with either the space charge limited or the Poole-Frenkel models for electrical conduction. The negative TCR effect diminishes and the usual metallic resistance is restored in thicker films, probably due to reduction in particle separation and further coalescence of neighbouring crystallites.
Raman Shift and Broadening in Stress-Minimized Ge Nanocrystals in Silicon Oxide Matrix
Authors: Jie YX , Huan CHA , Wee ATS , Shen ZX 
Published: April 2011

ABSTRACTGe nanocrystals (nc-Ge) embedded in silicon oxide films were synthesized using RF magnetron sputtering and post-annealing procedure. To minimize the stress effect and inhomogeneity, we intentionally lower the cooling rates and reduce the temperature gradient during annealing. Significant Raman shifts ranging from 2.0 to 5.8 cm−1have been observed from samples annealed at different temperatures. The size-dependent shift and broadening is found to be in good agreement with the phonon confinement mode together with the Gaussian weighting function, and the isotropic T02 phonon dispersion relation introduced by Sasaki et al. The Raman spectra can also be well-fitted using peaks calculated from the phonon confinement model. The inhomogeneous Raman peak broadening from our samples annealed at lower temperatures are attributed to the non-Gaussian size distribution of Ge nanocrystals.
Protein Supported Metallic Nanostructures as Catalysts
Authors: Behrens S. , Habicht W. , Boukis N. , Dinjus E. , Baum M. , Unger E. 
Published: April 2011

ABSTRACTHighly oriented proteins with characteristic nanometer dimensions are used as a template for the synthesis and support of metallic nanoparticles. Following a bottom-up approach, noble metal particles in the nanometer size range were obtained by the reduction of the corresponding metal salts in the presence of the protein assemblies. The catalytic activity of the protein-supported particles was determined by hydrogenation reactions.
Carboxylate-Alumoxanes: Precursors for Heterogeneous Catalysts
Authors: Jones Christopher D. , Brown David S. , Marshall Larry L , Barrona Andrew R. 
Published: April 2011

ABSTRACTCarboxylate-alumoxanes are organic substituted alumina nano-particles synthesized from boehmite in aqueous solution which are an inexpensive and environmentally benign precursor for the fabrication of nano-, meso-, and macro-scale aluminum based ceramics. The use of carboxylate-alumoxanes as a novel high surface area alumina support for heterogeneous catalysis will be discussed. The ability to perform further chemistry on the organic ligands of the carboxylate-alumoxanes allows for attachment of catalysts. During calcination, the organic ligands are burned out, leaving behind the catalyst in a well-dispersed manner. To demonstrate this concept, the metathesis of C16 olefins using a molybdenum oxide catalyst supported on alumina will be discussed using the carboxylate-alumoxane method.
The Formation of High-Coercivity, Oriented, Nanophase Cobalt Precipitates in Al2O3 Single Crystals by Ion Implantation
Authors: Honda S. , Modine F. A. , Haynes T. E. , Meldrum A. , Budai J. D. , Song K. J. , Thompson J. R. , Boatner L. A. 
Published: April 2011

ABSTRACTIon-implantation and thermal-processing methods have been used to form nanophase magnetic precipitates of metallic cobalt that are embedded in the near-surface region of single crystals of Al2O3. The Co precipitates are isolated, single-crystal particles that are crystallographically oriented with respect to the host Al2O3 lattice. Embedded nanophase Co precipitates were formed by the implantation of Co+ at an energy of 140 keV and a dose of 8 × 1016 ions/cm2 followed by annealing in a reducing atmosphere. The implanted/annealed Co depth profile, particle size distributions and shapes, and the orientational relationship between the nanophase precipitates and the host crystal lattice were determined using RBS/channeling, transmission electron microscopy, and x-ray diffraction. Magneto-optical effects arising from Co precipitates formed in the near-surface region of Al2O3 were observed and characterized using magnetic circular dichroism. Magnetic properties of the Co-particle/host nanocomposites were investigated in the temperature range of 77 to 295 K in applied fields of up to 10 kG using a superconducting quantum interference device (SQUID) magnetometer. Implantation of the Co particles by Pt or Xe ions produced a large anisotropic increase in their coercivity. Accordingly, these magnetic nanoparticle systems may be of interest for magnetic data storage applications. Details of the magnetic properties of the Co/Al2O3 nanocomposites including their retentivity, coercivity, saturation field, and magnetic anisotropy are presented.
Triple-Period (TP)-A and CuPt-A Type Ordering in Al0.5In0.5As Grown by Metalorganic-Vapor-Phase-Epitaxy
Authors: Suzuki Tohru , Ichihasfh Toshinari , Tsuji Masayoshi 
Published: April 2011

AbstractThe triple-period (TP)-A and CuPt-A type ordering, which have been so far reported only for MBE grown alloys, were observed, in addition to CuPt-B type ordering, in Al0.5In0.5As alloys grown by MOVPE at 500°C. This indicates that (2×3) and (1×2) surface reconstructions occur on the surface even during MOVPE growth, although the (2×1) surface reconstruction and CuPt-B type ordering are dominant for the growth conditions examined.
Kinetic Instability of Semiconductor Alloy Growth
Authors: Ipatova I. P. , Malyshkin V. G. , Shchukin V. A. , Maradudin A. A. , Wallis R. F. 
Published: April 2011

AbstractA kinetic theory of the instability of homogeneous alloy growth with respect to fluctuations of alloy composition is developed. The growth mechanism studied is the step-flow growth of an alloy from the vapor on a surface vicinal to the (001) surface of a cubic substrate. The epitaxial growth implies that the adsorbed atoms migrate on the surface during growth of each monolayer, and that their motion is “frozen” after the completion of the monolayer. Frozen fluctuations in all completed monolayers create, via the composition-dependent lattice parameter, an effective potential which influences the surface migration of adatoms. The migration consists of diffusion and strain-induced drift in the effective potential. For temperatures lower than a certain critical temperature Tc, strain-induced drift dominates diffusion and results in the kinetic instability of the homogeneous alloy growth. In the linear approximation in the fluctuation amplitude, the instability means the exponential increase of the fluctuation amplitude with the thickness of the epitaxial film. It is shown that the critical temperature of kinetic instability Tc, increases with the increase of elastic effects. The wave vector kc of the most unstable mode of composition fluctuations is determined by the interplay of anisotropic elastic interaction and anisotropic diffusion on a stepped vicinal surface. The direction of the wave vector kc differs from the lowest-stiffness direction of the crystal, and any direction of kc is possible.
Steady-State Structures in Composition-Modulated Alloys: Kinetic Phase Transition Between 1D and 2D Patterns
Authors: Shchukin V. A. , Starodubtsev A. N. 
Published: April 2011

AbstractA non-linear continuum theory of self-organized growth of composition-modulated structures in alloys is developed. It is shown that, for a lattice-matched alloy, where compositional and morphological instabilities are uncoupled in the linear regime, the two instabilities are coupled due to non-linear effects. Due to non-linear coupling, composition-induced stresses may lead to an instability of the advancing surface against undulations. A non-planar surface profile favors kinetic phase transition from the growth of a 1D modulated structure to the growth of a 2D one. A steady-state phase diagram in variables “temperature — growth velocity” is constructed which contains regions of homogeneous alloy growth, of 1D steady-state structures, of 2D steady-state structures, and the region where both 1D and 2D structures are possible. For zinc-blend semiconductors, the interplay between the anisotropic elasticity and anisotropic surface diffusion may lead to the kinetic phase transition between the growth of a 2D structure modulated in the elastically soft directions [100] and [010] to the growth of a 1D structure modulated in the direction of the fast diffusion [110]. Our theory explains this type of transition observed in the growth of InAlAs/InP.
Fullerene-Incorporated Nanocomposite Resist System for Nanolithograpy
Authors: Ishii T. , Nozawa H. , Kuramochi E. , Tamamura T. 
Published: April 2011

AbstractA nanocomposite resist system that incorporates sub-nm fullerene molecules ( C60 and/or C70) into a conventional resist material is proposed for nanolithograpy. Fullerene has physically and chemically resistant characteristics, and its incorporation reinforces the original resist film, leading to substantial improvements in resist performance: etching resistance, pattern contrast, mechanical strength and thermal resistance. We have prepared a system composed of a positive-type electron beam resist, ZEP520, and C60 or a C60/C70 mixture and through the fabrication of high electron mobility transistors (HEMTs), X-ray masks, and groove-grating mirrors for lasers with nanometer dimensions confirmed improved resist performance, particularly resolution improvements due to enhanced etching resistance. By making use of a characteristic unique to the nanocomposite, which is that sensitivity readily changes with the fullerene content due to a dissolution inhibiting effect of fullerene, we have constructed a fullerene-incorporated bilayer resist system for a lift-off process and have successfully fabricated a highly-ordered array of self-organized boxlike nanostructures and a mold for nanoprinting. Further, solubility enhancement by fullerene derivatives has been examined for a higher degree of fullerene incorporation and better sensitivity characteristics in future nanocomposite resist systems.
New High Resolution Liquid Crystal Electron Beam Resists
Authors: Robinson A. P. G. , Palmer R. E. , Tada T. , Kanayamat T. , Allen M. T. , Preecel J. A. , Harris K. D. M. 
Published: April 2011

AbstractWe report the development of a new family of electron beam resists based on liquid crystalline polysubstituted derivatives of triphenylene. These new resists show excellent performance in terms of both high resolution and high durability to plasma etching. Films of the derivatives have been produced in a controlled manner via room temperature spin coating on hydrogen terminated silicon substrates. The dissolution behaviour of the derivatives in various organic solvents was altered by exposure to a 20 keV electron beam. The solubility of the derivative hexapentyloxytriphenylene, in polar solvents, was substantially increased by electron doses greater than ∼ 3 × 10-4 C/cm2 (positive tone behaviour). Doses greater than ∼ 2.5 × 10-3 C/cm2 led to negative tone behaviour in both polar and non-polar solvents. Other derivatives also demonstrated a reduction in their dissolution rate for doses between ∼ 1 × 10-3 and ∼ 7 × 10-3 C/cm2. The derivative sensitivity was found to be roughly proportional to the molecular mass. Negative tone patterns were found to have an etch durability ∼ 70 % greater than that of a conventional novolac based negative tone resist (SAL601). The performance of these new resists has been demonstrated by the definition of line and space patterns with a resolution of ∼ 14 nm, whilst structures with an aspect ratio of.∼ 50 to 1 were etched into the silicon substrate.
Carbon Dioxide – Dilated Block Copolymer Templates for Nanostructured Materials
Authors: Brown Garth D. , Watkins James J. 
Published: April 2011

AbstractPeriodic polymer/metal (Pt or Ag) and polymer/semiconductor (PbS) nanocomposites are prepared using block copolymers dilated with carbon dioxide (CO2) as templates. Specifically, organometallic compounds (metal precursors) are dissolved into supercritical CO2 and infused into polystyrene-block-poly(acrylic acid) or polystyrene-block-poly(vinylpyridine) copolymers. Upon infusion, the acid or pyridine block selectively binds the metal precursor. The excess is removed from the polystyrene phase by subsequent CO2 extraction. Reduction of the bound organometallic with hydrogen or hydrogen sulfide yields the desired metal or semiconductor clusters, which are confined to the precursor-binding domain and remain positioned on the copolymer lattice. The composites are characterized by transmission electron microscopy, x-ray scattering and electron diffraction.
A New Purged UV Spectroscopic Ellipsometer to characterize 157nm nanolithographic materials
Authors: Boher Pierre , Piel Jean Philippe , Evrard Patrick , Stehle Jean Louis 
Published: April 2011

AbstractSpectroscopic ellipsometry has long been recognized as the technique of choice to characterize thin films and multilayers. It is now intensively used in microelectronics and especially for the microlithographic applications. Instrumentation for the next generation of UV lithography at 157nm requires special optical setup since oxygen and water are extremely absorbing below 190nm. The ellipsometer discussed in this paper works into a purged glove box to reduce the oxygen and water contamination in the part per million ranges. The optical setup has been especially studied for microlithographic applications. It includes for example a premonochromator in the polariser arm to avoid resist photobleaching. Technical details of the system and some first measurement results on substrates and thin films are reported hereafter.
Localized Charge Storage in CeO2/Si(111) By Electrostatic Force Microscopy
Authors: Jones J. T. , Bridger P. M. , Marsh O. J. , McGill T. C. 
Published: April 2011

AbstractIn this report, the local patterning of charge into CeO2/Si structures by scanning probe microscopy is examined. An electrostatic force microscope (EFM) has been used to write and image localized dots of charge on to double barrier CeO2/Si/CeO2/Si(lll) structures. By applying a large tip bias Vtip = 6 – 10 V and reducing the tip to sample separation to z = 3 – 5 nm for write times of t = 30 – 60 s, arrays of charge dots 60 – 250 nm FWHM have been written. The dependence of dot size and total stored charge on various writing parameters such as tip writing bias, tip to sample separation, and write time is examined. The total stored charge is found to be Q = 5 – 200 e per charge dot. These dots of charge are shown to be stable over periods of time greater than 24 hrs, with an initial charge decay time constant of τ ∼ 9.5 hrs followed by a period of much slower decay with τ > 24 hrs. Charge decay time constants are found to be dependent on the thickness of the lower CeO2 tunneling barrier.
Tailoring Grain-Boundary Segregation to Control Mechanical Properties
Authors: Williams D. B. , Keast V. J. 
Published: April 2011

ABSTRACTRecent advances in our understanding of the role of the chemistry of grain boundaries in controlling the mechanical properties of materials (in particular intergranular brittle fracture) are reviewed. It is now possible in a modem field-emission gun (FEG) analytical transmission electron microscope (AEM) to measure the chemistry of sub-nanometer films of GB segregants while at the same time observing the effect (if any) on the bonding of the atoms within a nanometer of the boundary plane. This has been accomplished by the development of X-ray mapping (XRM) a powerful new tool for the study of segregation. For the first time, in the same instrument, on the same grain boundary, any changes in the boundary chemistry can be correlated with the occurrence or absence of brittle failure, which is often associated with boundary segregation. There is strong evidence that boundary segregation is extremely nonuniform, even in some strongly embrittling systems (e.g. Cu-Bi) and in these same systems, embrittling segregants introduce subtle but consistent changes in the bonding. Non-embrittling segregants (e.g. Ag in Cu) do not introduce detectable bonding changes.
Impact of Grain Boundary Character on Electrical Property in Polycrystalline Silicon
Authors: Hamada Shu , Kawahara Koichi , Tsurekawa Sadahiro , Watanabe Tadao , Sekiguchi Takashi 
Published: April 2011

ABSTRACTGrain boundaries in polycrystalline silicon are most likely to generate localized states in band gap. The localized states play a dominant role in determining the performance of solar cells by acting as traps or recombination center of carriers. In the present investigation, the scanning electron microscope - electron channeling pattern(SEM/ECP) method and SEM - electron back scattered diffraction pattern(SEM/EBSD) technique were applied to characterize the grain boundaries in p-type polycrystalline silicon with 99.999%(5N) in purity. Thereafter, temperature dependence of electrical activity of individual grain boundaries was measured by an electron beam induced current(EBIC) technique.It has been found that temperature dependence of EBIC contrast at grain boundaries can change, depending on the misorientation angle the orientation of the boundary plane. The results can be explained by the difference in the position of the localized state within the band gap on the basis of the Shockley-Read-Hall statistics. The {111} ∑3 symmetrical tilt boundary has shallow states, while high ∑ boundaries have deep states. Low angle boundaries reveal high electrical activities. The EBIC contrast at low angle boundaries was found to increase with increasing misorientation angle up to 2° followed by an almost constant value. High electrical activity at low angle boundaries is probably attributed to a stress field of primary dislocations forming low angle boundaries.
Structure and Properties of Polycrystalline Materials From Simulation: An Interfacial Perspective
Authors: Phillpot S. R. , Keblinski P. , Wolf D. , Cleri F. 
Published: April 2011

ABSTRACTWe have recently developed a novel molecular-dynamics simulation method to grow polycrystals from a melt containing randomly oriented crystalline seeds. The resulting microstructures contain only randomly oriented (i.e., high-energy) grain boundaries. We find that these grain boundaries, which are highly constrained by their close proximity to grain junctions, are highly disordered in fcc metals and amorphous in silicon. From simulations of infinitely extended high-energy grain boundaries in bicrystals, we find that such highly disordered and amorphous grain boundaries are actually the thermodynamic ground state; by contrast, low-energy grain boundaries are crystalline. High-energy grain boundaries in diamond, however, are structurally ordered at the expense of a significant amount of graphite-like bonding. We show that these complex grain boundary structures have important effects on properties including grain boundary diffusion (fcc metals and silicon), grain boundary diffusion creep (silicon) and grain boundary electrical activity and strength (diamond). The implications for engineering materials with prescribed properties are discussed.