bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sol-Gel Synthesis of Rare Earth Aluminate Films as Buffer Layers for High Tc Superconducting Films
Authors: Beach David B. , Vallet Catherine E. , Paranthaman Mariappan , Specht Eliot D. , Morrell Jonathan S. , Xue Ziling B. 
Published: April 2011

ABSTRACTCubic rare-earth aluminate perovskites of the general form REAIO3 have been identified as possible buffer layers for high current carrying cuprate superconductors deposited on roll-textured metals. This paper describes on-going research to develop solution routes which would avoid the use of slow and costly vacuum processing. Our research plan includes the development of an appropriate solution chemistry, studies of the crystallization behavior of powders under reducing and oxidizing conditions, deposition of polycrystalline films on silver substrates, deposition of epitaxial films on single-crystal oxide substrates, and deposition on roll textured nickel. The method is illustrated with the example of PrAlO3.
Automotive Applications of Materials Prepared by Ceramic Precursor and Sol-Gel Routes
Authors: Narula C. K. , Varshney A. , Everson M. P. , Schmitz P. , Allard L. F. , Gandopadhyay A. , Suren Lewkbandara T. , Winter C. H. , Czubarow P. , Seyferth D. 
Published: April 2011

ABSTRACTThe promise of new applications continues to drive research on ceramic precursor and sol-gel routes to materials preparation. These routes offer flexibility in the fabrication of materials in forms such as films, coatings, fibers, foams, and powders, etc. Our interest in ceramic precursors stems from their potential in the low cost fabrication of films. Such films can be employed in a variety of new automotive applications. In this article, we summarize our efforts to prepare soluble ceramic precursors and their conversion to group IV metal nitrides. A comparison of some properties of electrically conducting titanium nitride films prepared by dipcoat-fire cycle and low pressure CVD is presented. We also describe the fabrication of indium tin oxide films by a sol-gel process. These films are candidates in the low cost fabrication of electrically heatable catalyst devices.
Properties of TiN and TiN Deposited by CVD on Graphite for Pyrochemical Applications
Authors: Maiya P. S. , Moon B. M. 
Published: April 2011

ABSTRACTHigh-density TiN (>098% of theoretical) has been prepared by hot pressing TiN powder with 2–4 wt.% Li2CO3at temperatures between 1150–1550°C and pressures of ≈40–50 MPa. The Li2CO3served as a fugitive sintering aid, enabling attainment of high density at low temperatures without adversely affecting the inherently good properties. Variation in processing variables and TiN powder characteristics resulted in material with various porosities. Measurement of mechanical properties such as flexural strength and fracture toughness showed that the high-density material has mechanical properties that are superior to those of several oxide ceramics. We have also quantified the effects of porosity on mechanical properties. In addition, adhesion and chemical stability tests were used to investigate graphite coated with TiN by chemical vapor deposition (CVD). Pin-pull tests were used to determine coating adhesion and failure stresses were analyzed by Weibull statistics. All pin-pull tests resulted in fracture of the graphite substrate, rather than separation at the TiN/graphite interface. The data showed a good fit to the two-parameter Weibull expression, with a failure strength of 16.4 MPa and Weibull modulus of 9.3. Both the high-density TiN and the TiN coating on the graphite were exposed to a corrosive molten salt CaCl2-7 wt.% CaO and a liquid metal alloy (Zn-10 wt.% Mg) at 800°C for 168 h to determine chemical interactions. No reaction was detected by scanning electron microscopy (SEM) or energy-dispersive X-ray (EDX) analysis. Thus, graphite coated with TiN by CVD combines the thermodynamic stability of TiN when exposed to reactive molten metals and salts, with the excellent machinability of graphite, and hence is promising for use in container vessels for pyrochemical processing of certain rare-earth and nuclear metals, where chemical inertness and good matching of thermal expansion coefficients are required.
Preparation of YBCO Superconducting Thin Film by Pulsed Thermal Decomposition of Ultrasonic-Misted Nitrate Solution
Authors: Kinugasa Junichi. , Hatta Akimitsu. , Ito Toshimichi. 
Published: April 2011

ABSTRACTYBa2Cu3O7-x superconducting thin films have been prepared by a new material preparation method, namely pulsed thermal decomposition of ultrasonic-misted nitrate solution. The prepared films have been studied by using powder X-ray diffraction method, scanning electron microscopy and Rutherford backscattering spectrometry. The results obtained indicate (1) that by local heating of the substrate with an infrared lamp, c-axis oriented YBa2Cu3O7-x films can be deposited without segregation of impurity phases, (2) that a high decomposition temperature is necessary to increase flatness of thin YBa2Cu3O7-x films although a sufficient margin temperature is required to obtain impurity-phase-free films, and (3) that the efficiency of the process increases if the adhesion is large between the deposited film and the substrate.
Low Temperature Remote Plasma Assisted Jet Vapor Deposition of Silicon Nitride
Authors: Veteran J. , Hobbs C. , Hegde R. , Tobin P. , Wang V. , Tseng H. , Kenig G. , Hartig M. , Tamagawa T. , Doran R. , Makowicz P. , Schmitt J. , Halpern B. , Zhang J. Z. 
Published: April 2011

ABSTRACTAs MOSFET dimensions are aggressively scaled, minimizing the thermal budget becomes critical for limiting the diffusion of channel profiles. Unfortunately, high quality dielectrics with low deposition temperatures have not been readily available. Typical room temperature dielectrics are porous and electrically leaky. A promising technique for low temperature dielectric deposition is Jet Vapor Deposition (JVD). [1] Two coaxial quartz nozzles spray the process gases to the substrate surface at super-sonic speeds while a microwave cavity generates a plasma in the nozzle. [2] We have successfully deposited silicon nitride films using SiH4/He and N2/He gas mixtures. These are the first reported JVD results on 200 mm wafers.
Spectroscopic and Structural Studies of Some Precursors for the Deposition of PZT and Related Materials by MOCVD
Authors: Fleeting Kirsty A. , Jones Tony C. , Leedham Tim , Azad Malik M. , O'brien Paul , Otway David J. 
Published: April 2011

ABSTRACTMOCVD is a useful method for the deposition of thin films of lead zirconium titanate, PZT, because of its good step coverage and control of composition. Results are herein presented on a number of novel compounds which are potential MOCVD precursors. The compounds studied include Pb(tmhd)2, Zr(OBu')4 and Ti(OPr')4. Another commonly utilized precursor Zr(tmhd)4, is not ideal, in that it is a high melting point solid, and hence requires high substrate temperatures. We have sought to modify Zr precursors through chemical methods and have synthesized a number of novel, more volatile, and less intrinsically thermally stable MOCVD precursors. Full chemical characterization of the Zr precursors (NMR, IR, MS, CHN, TGA/DSC, Single Crystal X-ray diffraction) has been undertaken. We also present structural results on some related lead precursors.
Chemical Vapor Deposition of Ruthenium Dioxide Thin Films From Bis(2, 4-Dimethylpentadienyl)Ruthenium
Authors: Meda Lamartine , Breitkopf Richard C. , Haas Terry E. , Kirss Rein U. 
Published: April 2011

ABSTRACTThin films of polycrystalline RuO2 were deposited from bis(2,4-dimethylpentadienyl) ruthenium, (η5-2, 4-Me2C5H5)2Ru (1) and ruthenocene (2) on quartz and silicon substrates between 200 and 500°C under Ar/O2 or O2. Films deposited from 1 were more adherent than those grown from 2 under the same conditions, however, none of the films were particularly adherent when O2 was used as a carrier gas. SEM revealed a columnar structure for both precursors with grain size ranging from 0.15 – 1 5μ. Crystallinity increased after annealing the films to 800°C. Resistivity decreased as the annealing temperature increased.
Precursors for Vapor Deposition of Blue Phosphors for Electroluminescent Flat Panel Displays
Authors: Rees William S. , Just Oliver , Luten Henry A. , Otway David J. 
Published: April 2011

ABSTRACTNew strontium (host lattice constituent) and cerium (doping element) precursor sources have been developed and evaluated for deposition of blue color emitting SrS:Ce thin films by ALE (Atomic Layer Epitaxy). In the case of strontium, the monomeric derivative [Sr(hfac)2]*triglyme has been synthesized and structurally characterized, whereas, for cerium, the utilization of its homoleptic tris amide derivative Ce{N[Si(CH3)3]2}3 has led to a blue color emitting SrS:Ce. In a further effort, emission characteristics of SrS:Ce doped with the β-diketonate-related Ce(tmhd)4 derivative have been weighed against data obtained employing the cerium tris amide composition.
The Raft-Like Structure of Supported PtRu5
Authors: Yang J. C. , Bradley S. , Nashner M. N. , Nuzzo R. , Gibson J. M. 
Published: April 2011

ABSTRACTWe have examined supported PtRus specimens by a variety of electron microscopy techniques, including high resolution, analytical and a novel mass-spectroscopic electron microscopy techniques. Analytical electron microscopy results showed that the relative atomic concentration of Pt to Ru for each PtRu5 cluster is 1 to 5. The average diameter of the clusters was a 15.6Å, and the average number of atoms was measured to be 24 atoms per cluster. The combination of these techniques demonstrate that the PtRu5 clusters are raft-like on the carbon black support.
Stability and Surface Acidity of Aluminum Oxide Grafted on Silica Gel Surface
Authors: Prado L. L. L. , Nascente P. A. P. , de Castro S. C. , Gushikem Y. 
Published: April 2011

ABSTRACTThe synthesis of aluminum oxide grafted on silica gel surface was carried out by the reaction of a suitable aluminum precursor with the surface hydrolysis of the oxide support. The chemical and physical properties of the attached oxide, SiO2/ Al2O3, can be quite different than those found for bulk Al2O3. The advantage of this preparation method, compared to the conventional ones (impregnation, precipitation and calcination), is that the oxide is highly dispersed on the surface (monolayer or submonolayer). We characterized the surface oxides treated at the temperature range of 423 to 1573 K employing X-ray photoelectron spectroscopy (XPS), solid state nuclear magnetic resonance spectroscopy (NMR), and diffuse reflectance spectroscopy (DRS). XPS was used to identify the oxidation states and atomic ratios. Al27 NMR detected two species for samples heated up to 1023 K, and another one above this temperature. DRS, using pyridine as a molecular probe, showed that both Lewis and Brönsted acid sites are stable up to 1023 K. We concluded that the aluminum oxide is highly dispersed on the silica gel surface and it remains stable up to 1023 K.
Surface Characterization of W/Ni/Al2O3 Catalysts
Authors: Jordão M. H. , Assaf J. M. , Nascente P. A. P. 
Published: April 2011

ABSTRACTCatalysts containing tungsten and nickel oxides are important in hydrodesulfurization (HDS), hydrogénation (HY), and steam reforming of hydrocarbons. A series of W/Ni/Al2O3 catalysts was prepared by two different methods: (1) coprecipitation of nickel and aluminium hydroxicarbonate from their nitrates, followed by calcination and impregnation of tungsten; (2) precipitation of boehmite from aluminium nitrate, followed by impregnations of nickel, firstly, and tungsten. The nickel content was kept constant, while the amount of tungsten varied from 2.5 to 15.5 wt-%. The resulting oxides were characterized by inductively coupled plasma spectroscopy (ICP), atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). ICP and AAS were used to determine the W, Ni, and Al concentrations. XRD detected two phases: NiO and NiAl2O4 (no phase containing metallic tungsten was detected). Increasing the amount of W, the quantity of NiAl2O4 rose, the quantity of NiO decreased, and the particle size of NiO enlarged. The TPR profiles presented three peaks: one at about 1000 °C, associated to a very stable phase; for the samples prepared by coprecipitation, the other two peaks corresponded to “free NiO” and a nonstoichiometric aluminate. For the samples prepared by impregnation, those peaks corresponded to NiO and NiAl2O4. XPS identified Al2O3, NiAl2O4, and Al2(WO4)3 for both preparation methods. Increasing the amount of tungsten in the impregnated samples, NiWO4 was also observed.
Properties of Pure and Sulfided NiMoO4 and CoMoO4 Catalysts: Tpr, Xanes and Time-Resolved XRD Studdzs
Authors: Chaturvedi S. , Rodriguez J. A. , Hanson J. C. , Albornoz A. , Brito J. L. 
Published: April 2011

ABSTRACTX-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO4.nH20, α-AMoO4, β-AMoO4; A= Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the a-phases to tetrahedral in the β-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the β-AMoO4 compounds (following a kinetics of first order) at temperatures between 200 and 350 °C. This is facilitated by the similarities that the AMoO4.nH20 and β-AMoO4 compounds have in their structural and electronic properties. The molybdates react with H 2 at temperatures between 400 and 600 °C, forming gaseous water and oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing α-NiMoO4 and P-NiMoO4 to H2S, both metals get sulfided and a NiMoSx phase is formed. For the β phase of NiMoO4 the sulfidation of Mo is more extensive than for the a phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.
Electron Field Emission from Multilayered Tetrahedral Amorphous Carbon Films
Authors: Shi X. , Cheah L. K. , Silva S. R. P. , Tay B. K. , Yang H. S. , Sun Z. 
Published: April 2011

ABSTRACTThe electron emission switching property of the multilayer structures, which constitute of nitrogen doped tetrahedral amorphous carbon (n+-ta-C) film and intrinsic ta-C layer fabricated by the filtered cathodic vacuum arc (FCVA) technique has been investigated. Low voltage DC bias (9V) was applied between the top and bottom layers in conjunction with the conventional electric field applied between the cathode and anode. It has been demonstrated that by varying the low DC bias polarity, the on-set electric field for the electron emission can be varied by ∼ ±6 V/μm compared to the unbiased situation. A possible mechanism for the multilayer field emission and the switching property is proposed.
Electron Emission Properties of Si Field Emitter Arrays Coated With Nanocrystalline Diamond From Fullerene Precursors
Authors: McCauley T. G. , Corrigan T. D. , Krauss A. R. , Auciello O. , Zhou D. , Gruen D. M. , Temple D. , Chang R.P.H. , English S. , Nemanich R. J. 
Published: April 2011

ABSTRACTIn this paper, we report on a substantial lowering of the threshold field for electron field emission from Si field emitter arrays (FEA), which have been coated with a thin layer of nanocrystalline diamond by microwave plasma-assisted chemical vapor deposition (MPCVD) from fullerene (C60) and methane (CH4) precursors. The field emission characteristics were investigated and the emission sites imaged using photoelectron emission microscopy (PEEM). Electron emission from these Si FEAs coated with nanocrystalline diamond was observed at threshold fields as low as 3 V/μm, with effective work functions as low as 0.59 eV.
Synthesis of C-N films by hot carbon filament CVD
Authors: Watanabe Yoshihisa , Kasai Hiroshi , Kawasumi Emi , Amamoto Yoshiki , Nakamura Yoshikazu 
Published: April 2011

ABSTRACTThin films composed of carbon and nitrogen were synthesized by hot-filament chemical vapor deposition method. Deposition method was developed by replacing a filament material from metals to graphite to ascertain two effects; (1) prevention of contamination from the filament material and (2) feasibility of synthesis of hydrogen free films without using hydrocarbon gas such as methane. Films were synthesized from pure nitrogen gas and hot graphite filament. Synthesized films were characterized by Auger electron spectroscopy, Raman spectroscopy, X ray diffraction, atomic force microscopy and nano indentations. It is found that the synthesized films are amorphous with the smooth and uniform surface and show the elastic behavior.
Doping Induced Internal Stress Reduction in Diamondlike Carbon Films Deposited by Pulsed Laser Ablation
Authors: Wei Q. , Narayan R. J. , Sharma A. K. , Sankar J. , Narayan J. 
Published: April 2011

ABSTRACTWe have investigated the effect of dopants on the reduction of internal compressive stress in diamond-like carbon (DLC) films prepared by pulsed laser deposition on Si(100) substrates. A novel target configuration was used to incorporate dopants into DLC films by sequential pulsed laser ablation of two targets. These dopants include copper, titanium and silicon. The thickness of the DLC films deposited was measured in the range 400nm - 600nm using a profilometer. Raman spectroscopy was employed to analyze the chemistry of the films. The shifts of the G-peak position in the Raman spectrum, due to different concentrations of dopant, were used to estimate the internal stress changes. All of the films showed a Raman spectrum typical of DLC films containing a high fraction of sp3 species, with the G-peak centered at around 1510–1560cm−1. The shift of the G-peak due to the presence of dopants was observed for all the DLC films as compared to the undoped one. It was found that Ti has the strongest tendency to reduce the compressive stress of DLC films. This effect increases with increasing concentration of dopants. Silicon was also observed to have this effect, but the G-peak position did not appear to shift with different Si concentrations. Buckling occurred in the as-deposited, undoped DLC film because of the relief of the large compressive stress accumulated in the film, while all the doped DLC films showed good adhesion to the substrate. The results are discussed combining the atomic structure of DLC and the structure and properties of the dopants.
Equation of State of Warm Condensed Matter
Authors: Barbee T. W. , Young D. A. , Rogers F. J. 
Published: April 2011

ABSTRACTRecent advances in computational condensed matter theory have yielded accurate calculations of properties of materials. These calculations have, for the most part, focused on the low temperature (T=0) limit. An accurate determination of the equation of state (EOS) at finite temperature also requires knowledge of the behavior of the electron and ion thermal pressure as a function of T. Current approaches often interpolate between calculated T=0 results and approximations valid in the high T limit. Plasma physics-based approaches are accurate in the high temperature limit, but lose accuracy below T∼Tfermi. We seek to “connect up” these two regimes by using ab initio finite temperature methods (including linear-response[l] based phonon calculations) to derive an equation of state of condensed matter for T<Tfermi.We will present theoretical results for the principal Hugoniot of shocked materials, including carbon and aluminum, up to pressures P>100 GPa and temperatures T> 104K, and compare our results with available experimental data.
Sintering of Compacts from Nanocrystalline Diamonds Without Sintering Agent
Authors: Witek A. , Palosz B. , Stel'Makh S. , Gierlotka S. , Pielaszek R. , Ekimov E. , Filonenko V. , Gavriliuk A. , Gryaznov V. 
Published: April 2011

ABSTRACTCompacts of polycrystalline diamond were made in toroid-type high-pressure camera under the pressure of 8 GPa using temperatures between 800 to 2150°C without the use of additive components. Nanocrystalline commercial DALAN, and microcrystalline ASM diamond powders were used. The compacts were characterized by helium pycnometry, Vickers hardness measurements, X-ray diffraction and SEM methods.The starting and sintered nanocrystalline grain compacts were found to have strongly one-dimensionally disordered cubic modification. The nanocrystalline powder had a bimodal grain size distribution function as determined from X-ray diffraction data and ab initio intensity calculations performed with the use of Debye functions. It was found that neither the grain size nor one-dimensional disordering change under high-pressure high-temperature conditions. There is a general tendency in a decrease of density of compacts with increase in the sintering temperature what resulting partly from graphitization above 1000–1200°C. The main factor which determines the density of the diamond compacts is closed porosity. Typically, the nanocrystalline diamond compacts sintered from 30 sec. to 6 min. have densities around 90% of the theoretical value. Their Vickers microhardness is 24 GPa and less.
High Pressure - High Temperature Synthesis of Low-Compressibility Cubic C3N4
Authors: Nguyen Jeffrey H. , Caldwell Wendel A. , Benedetti Laura Robin , Kruger Michael B. , Jeanloz Raymond 
Published: April 2011

ABSTRACTWe report the synthesis of a crystalline carbon-nitrogen compound having a zero-pressure bulk modulus of ∼ 249 GPa. Its crystal-structural and compressional properties are in good accord with those predicted theoretically by Teter and Hemley for a cubic C3N4 phase. Experimentally, this phase is synthesized at pressures and temperatures above 18 GPa and 2000 K. It decomposes upon pressure release below 14 GPa, and may offer a route to synthesizing other incompressible carbon nitride phases.
Infrared Optical Studies of Semiconductors at Large Hydrostatic Pressures
Authors: Haller E. E. , McCluskey M. D. 
Published: April 2011

ABSTRACTAmong the various external disturbances used in the study of semiconductors, including electric and magnetic fields as well as uniaxial pressure, large hydrostatic pressures can be employed to induce dramatic changes in host lattice, dopant and defect properties. Diamond anvil cells with an appropriate pressure medium (e.g. liquid N2 or alcohol mixtures) allow the application of pressures up to hundreds of kbar. In this pressure range the global conduction band minimum of a semiconductor can become a local minimum. GaAs for example changes near 45 kbar from a direct (Γ-band) to an indirect (X-band) semiconductor. Donors in GaAs and InP transform from their shallow, hydrogenic state to the DX configuration at hydrostatic pressures near 23 and 82 kbar, respectively. This donor configuration change has been studied using local vibrational mode (LVM) spectroscopy in the far infrared region of the electromagnetic spectrum. Recently we have investigated several LVM's of H-containing complexes in GaAs as a function of hydrostatic pressure at liquid He temperatures. Depending on the specific complex we find the LVM frequencies to vary either linearly, sub- or superlinearly with hydrostatic pressure. In the case of O in Si the vibrational mode changes its character from that of a harmonic oscillator to a rotor as pressure is applied. The implications of the pressure dependences of LVM's are discussed.