bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performances of Sexithiophene Based Thin-Film Transistor Using Self-Assembled Monolayers
Authors: Collet J. , Tharaud O. , Legrand C. , Chapoton A. , Vuillaume D. 
Published: April 2011

AbstractHigh performance thin-film transistors (TFT) made of conducting oligomers are obtained when the organic films are well ordered at a molecular level. Highly ordered films are obtained provided that oligomers have a sufficient mobility on the substrate surface during film formation. One possible way to fulfill such a condition is to evaporate oligomers on heated substrates [1,2]. In this work, we suggest that a high surface mobility is obtained by a chemical functionalization of the silicon dioxide surface, and the corresponding improvements of the TFT performances are evidenced. A self-assembled monolayer of octadecyltrichlorosilane (OTS) was deposited on the SiO2 by chemisorption from solution before the evaporation of sexithiophene film. Room temperature current-voltage measurements indicate that the presence of the OTS monolayer improves TFT performances : threshold voltage is decreased, subthreshold slope is decreased, a high current ratio Ion/Ioff is obtained for a reduced gate voltage excursion, the fieldeffect mobility is slightly increased. We have also fabricated and characterized a nanometer scale organic FET (gate length = 50 nm) made of 6T films and only with a self-assembled monolayer as the insulating film between the degenerated silicon substrate (gate) and the conducting channel (no thick SiO2, we call it « oxide-free » organic FET). Performances of this nanometer size organic FETs are the following : subthreshold slope of 0.35V/dec, threshold voltage of −1.3V, effective mobility of 2×10−4 cm2/V.s.
Organic/Inorganic Langmuir-Blodgeti Films Based on Metal Phosphonates
Authors: Talham Daniel R. , Fanucci Gail E. , Petruska Melissa A. , Seip Candace T. 
Published: April 2011

AbstractLangmuir-Blodgett (LB) bilayers of organophosphonic acids can be prepared where the phosphonic acid headgroups bind metal ions to form the same layered extended-solid structures present in solid-state metal phosphonates. The inorganic extended-solid network enhances the stability of the LB films, but can also be designed to introduce physical properties, such as magnetism, that are typical of the inorganic solid-state. By preparing films based on functionalized organophosphonic acids, the metal phosphonate approach can be used to produce “dualnetwork” LB films, where both the organic and inorganic networks add function to the thin film assembly. To begin to understand the design constraints associated with dual-network metal phosphonate films, LB bilayers of a phosphonic acidderivatized azobenzene amphiphile are formed with Cd2+ and La3+ and the structures are compared to octadecylphosphonate LB films prepared with the same metals.
Metal Complex Polymers for Electroluminescent Applications
Authors: Tao X. T. , Suzuki H. , Zhang Y. D. , Watanabe T. , Miyata S. , Wada T. , Sasabe H. 
Published: April 2011

AbstractWe report the synthesis and characterization of a soluble metal complex polymer for electroluminescent (EL) applications. The polymer was prepared by the reaction of a zinc Schiff base with 4,4′-diphenylmethane-diisocyanate. The polymer is amorphous and with glass transition temperature of 156 °C and is soluble in common organic solvents such as chloroform, tetrahydrofuran (THF), and N-methylpyrrolidinone (NMP). High optical quality films were obtained by spin-coating the polymer solution of THF. The zinc Schiff base, and the polyurethane (PU) shows strong photoluminescence under a UV-lamp illumination. Single and double layer EL devices consisting ITO/hole transfer layer (HTL)/PU/Al have been fabricated and characterized. The results indicated that the complex polymer could act as both electron transport and emissive layers for EL devices.
A Study on Langmuir Monolayers of Methacrylate Homo- and Copolymers Derivatized with Disperse Red Dyes
Authors: Dhanabalan Anantharaman , Balogh Débora , Constantino Carlos José Leopoldo , Riul Antonio , Oliveira Osvaldo N. , Giacometti José A. 
Published: April 2011

AbstractWe report on the organization of different disperse red dye derivatized methacrylate homo- and copolymers as Langmuir monolayers at the air-water interface. The monolayers were investigated using surface pressure and surface potential isotherms. Methacrylic homopolymers containing disperse red-1 (HPDR1) and disperse red-13 (HPDR13) and methacrylic copolymers with different mole percentages of the dye and hydroxyethyl spacer groups were synthesized and characterized. A comparison of the monolayer characteristics of HPDR1 and HPDR13 revealed the influence of the chlorine substitution in the aromatic ring of the dye. Studies with copolymers indicated a clear transition in the monolayer behavior with the change of mole percentage of the dye incorporated in the polymer. While copolymers with low dye content (up to about 5 mole%) presented an expanded monolayer, the copolymers containing higher dye content (12% and above) formed a condensed monolayer similar to that of the homopolymer. These results indicated the critical role of the dye component in the polymer chain in forming the monolayer at the air-water interface.
Crystallization Mechanism of Ferroelectric SBT Thin Films
Authors: Ikeda Yuji , Hironaka Katsuyuki , Isobe Chiharu 
Published: April 2011

ABSTRCTWe characterize, via selected area electron diffraction and high resolution TEM, the multistage crystallization process by which strontium bismuth tantalate(SBT) thin films are transformed from initial amorphous phase to the fully formed layer-structured perovskite. During the annealing process at 800°C, we found that an intermediate fluorite-like stage is formed after 3min as the SBT precursor crystallizing into the final SBT structure. This new information will be very important for formation and crystallization of ferroelectric SBT films.
Effects of Buffer Layer on the Fabrication and Characteristics of Ferroelectric Thin Films
Authors: Song Han Wook , Lee Joon Sung , Kim Dae-Weon , Kim Kwang Ho , Sung Tae-Hyun , No Kwangsoo 
Published: April 2011

ABSTRACTMgO thin films were deposited on Si(100) substrate with different temperatures from 500 °C to 800 °C and different e-beam powers from 25W to 100W using e-beam evaporation method. Pb(Zr0.53Ti0.47)O3(PZT) thin films were deposited on MgO/Si(100) substrates with different drying temperatures from 190 °C to 310 °C using sol-gel technique. If there were no buffer layer between the PZT thin film and Si substrate, the peaks corresponding to perovskite PZT phase were not observed. However the buffer layer were inserted between the PZT thin film and Si substrate, it was possible to fabricate perovskite PZT phase. The barrier effects of MgO thin film to the interdiffusion of Pb were investigated by AES study. Optimum thickness of MgO at which PZT/MgO/Si structure shows P-E hysteresis was calculated, and the hysteresis was tested for PZT/MgO/Si structures with different MgO thicknesses.
The Effects of Film Thickness and Texture on the high and Low-Field stress Response of Lead Zirconate Titanate Thin Films
Authors: Shepard J. F. , Chu F. , Xu B. , Trolier-McKinstry S. 
Published: April 2011

ABSTRACTLead zirconate titanate (PZT) thin films are currently employed in non-volatile ferroelectric memories (FRAM's) and are intended to be used as the active material in a number of microelectromechanical systems (MEMS). Several groups have reported that both the piezoelectric and dielectric characteristics of ferroelectric thin films improve with an increase of film thickness, though the reasons for those improvements are unclear. Previous investigations on the effects of biaxial mechanical stress indicate that non-180° domain wall motion is limited in PZT 52/48 films less than 0.5 μm thick. It is possible that some of the improvements of the dielectric and piezoelectric characteristics reported for thicker films (i.e. films thicker than 0.5 μm) are associated with an increase of extrinsic contributions to the properties. To evaluate domain wall mobility in thicker films, the high and low-field stress response of sol-gel PZT fabricated with either rapid thermal processing or conventional furnace annealing were investigated. Films with thicknesses ranging from 0.6 to 5.0 μm thick were measured as a function of applied biaxial stress (±110 MPa). It was found that for all films tested the changes of capacitance were on the order of 2–3%. High-field measurements showed: (1) the coercive field to be insensitive to applied stress, (2) remanent polarizations to decrease about 20% at the maximum applied tension, (3) remanent polarizations to increase less than 10% with applied compression, and (4) all changes to be reversible over the stress range investigated. These results suggest that extrinsic contributions are limited for the films tested.
Surface and size effects on the Ferroelectric Phase Transition and Surface Polarization of Thin Films: Monte Carlo Simulations
Authors: Romero J. , Fonseca L. F. 
Published: April 2011

ABSTRACTThe macroscopic polarization of ferroelectric thin films was studied by Monte Carlo simulations using a Transverse Ising Model Hamiltonian with four-spins interactions. The dependence of the ferroelectric phase transition temperature, Tc, on the thickness of the film was obtained resulting in a shifting of Tc towards lower temperatures and a change from first-order to second-order phase transition as the thickness of the film is reduced. Comparison between the surface and internal order was carried out by the calculation of layer-averaged polarizations as a function of the sample temperature and the surface interaction parameters. These comparisons show that increasing disorder at the surface can be reverted by increasing the four-spins surface interactions.
Control of Growth Dynamics by Molecular Design in the MOCVD of Electronic Ceramics
Authors: Jones A. C. , Leedham T. J. , Wright P. J. , Crosbie M. J. , Williams D. J. , Lane P. A. , O'brien P. 
Published: April 2011

ABSTRACTThe MOCVD technique is being used increasingly for the deposition of electronic ceramics such as Pb(Zr,Ti)O3, Ta2O5and TiO2. For the mil potential of MOCVD to be realised, it is sometimes necessary to modify existing precursors so that process parameters in the MOCVD process are optimised. In this paper we describe our approach to “molecular design” and discuss how the substitution of simple alkoxide groups by β-diketonates or donor-functionalised ligands can result in precursors with improved physical properties and optimum MOCVD characteristics.
A Surface Raman and Scanning Tunneling Microscopy Study of The Spatial Distribution of Corner-Sharing and Edge-Sharing Octahedra on thermally Oxidized Tungsten
Authors: Côté Matthew J. , Radloff Corey , Osman Joseph M. , Bussjager Rebecca , Martin Villarica R. , Nash Fazio , Chaiken J. 
Published: April 2011

ABSTRACTWe have measured the dependence of the strength of Raman activity of polycrystalline m-WO3 on spot size at constant laser power density. These data are compared to surface area scaling measurements obtained using scanning tunneling microscopy. We argue that the spatial distribution of scattering centers is the complement of the spatial distribution of crystallographic shear (CS) structures on or near the oxide surface. Our results are consistent with there being an essentially uniform spatial distribution of scattering sites which implies the spatial distribution of defect sites is also uniform. At the laser power density involved and at the defect densities studied, we found no evidence suggesting a large amount of cooperativity in the formation of CS structures. These results suggest a qualitative description of the structure of common oxide surfaces in agreement with a basic assumption of the JMAK theory of first order phase transformations.
Thick Films of Pb(Mg,Nb)TiO by Aerosol Combustion
Authors: Greenwald A. C. , Kussmaul A. , Morse T. F. , Wei C. H. 
Published: April 2011

ABSTRACTThick films of solid solutions of lead-magnesium-niobium-oxide (PMN) and lead-titanate (PTO) were deposited by aerosol combustion. Films consisted of submicron ceramic particles synthesized by combustion of a metalorganic solution in a methane-oxygen flame. The particulate material was deposited on heated substrates (200°C) and subsequently sintered at elevated temperatures. Results varied with starting chemistry and sintering conditions. As-deposited materials were mixed perovskite-pyrochlore phase. Sintering at low temperatures produced pure perovskite material that was not completely dense. Sintering at high temperatures produced dense ceramics of pyrochlore material. This technique requires further optimization for direct deposition of continuous films, but is immediately suitable for producing fine powders for tape casting of capacitors, etc.
Catalytic Properties of Fullerene Materials
Authors: Malhotra R. , Hirschon A. S. , McMillen D. F. , Bell W. L. 
Published: April 2011

ABSTRACTFullerenes were found to catalyze coupling and transalkylation reactions of mesitylene, engage in transfer hydrogenations with dihydroaromatics, and cleave strong bonds such as those in diarylmethanes. In all of these reactions, fullerenes show a marked ability to accept and to transfer hydrogen atoms. The key structural feature that endows fullerenes with many of its characteristics is the presence of a pentagon surrounded by hexagons. We suspected that fullerene soot, unlike graphitic carbon, contained pentagons in a hexagonal lattice, and that these sites imparted the soot with the desired chemical attributes of strong electrophilic nature and an ability to stabilize radicals. In subsequent studies, we have shown fullerene soot to be very effective in catalyzing various H-transfer reactions, including the conversion of methane into higher hydrocarbons. When compared with other carbons, such as activated carbons and acetylene black, the fullerene soot is much more reactive for oligomerization and hydrodealkylation of alkylbenzenes. Because this activity remains, even in chemically extracted and partially oxidized soot, the observed catalysis is not a result of residual soluble fullerenes.
Esr of Purified Carbon Nanotubes Produced Under Different Helium Pressures
Authors: Wong S. P. , Zhang Haiyan , Ke Ning , Peng Shaoqi 
Published: April 2011

ABSTRACTCarbon nanotubes were prepared by the dc arc-discharge method under a controlled helium pressure ranging from 10 to 80 kPa and subsequently purified by oxidation in air. The purified carbon nanotubes were observed by transmission electron microscopy. The room temperature electron spin resonance (ESR) spectra of the purified nanotubes were measured. The variations in the ESR line shape, g-value, linewidth and relative spin density of the purified nanotubes on helium pressure were studied and discussed.
Dense Oxide Membranes for Oxygen Separation and Methane Conversion
Authors: Jacobson A. J. , Kim S. , Medina A. , Yang Y. L. , Abeles B. 
Published: April 2011

ABSTRACTMethane conversion to synthesis gas in membrane reactors that use dense mixed electronic-ionic conducting membranes for oxygen separation has received much recent attention. The oxygen flux achievable in these reactors depends on a combination of the bulk diffusion rate for oxygen transport and the surface reaction rate for oxygen activation and either recombination or reaction with methane. Here we compare recent oxygen permeation data for tubular membranes of La0.5Sr0.5Fe0.8Ga0.2O3-δ with our previous results for SrCO0.8Fe0.2O3-δ, SrFeCO0.5O3.25-δ. The pressure dependence of the oxygen permeation flux has been measured at different temperatures and used to determine the relative importance of bulk and surface kinetics for these oxides.
Comparison of Nanocrystalline and Polycrystalline Oxide Supports for Catalytic Oxidation of Methane
Authors: Hahn Horst H. , Hesemann Heiko , Epling William S. , Hoflund Gar B. 
Published: April 2011

ABSTRACTNanocrystalline and polycrystalline ZrO2, CeO2 and Mn3O4 without and with 5 wt% Pd have been tested for methane oxidation. The nanocrystalline catalysts perform better than the polycrystalline catalysts on a weight basis. Nanocrystalline (n)-CeO2 performs much better than n-ZrO2, and both perform much better than polycrystalline (P)-CeO2 and P-ZrO2. 5 wt% Pd/n-ZrO2 is the best catalyst tested, but 5 wt% Pd/n-CeO2 performs nearly as well. A 20 wt% Ag/p-ZrO2 and a 20 wt% Ag/n-ZrO2 catalyst were also tested. The Ag yields a significant improvement over the bare supports, but not as much so as Pd.
Cathodic Arc Deposition of Tetrahedral Amorphous Carbon: Influence of Process Parameters on Microstructure and Hardness
Authors: Camphausen S. M. , Myers A. F. , Bozeman S. P. , Baldwin D. A. , Cuomo J. J. 
Published: April 2011

ABSTRACTThe cathodic arc provides a method for depositing extremely hard thin carbon films. These films are potentially useful in a variety of tribological applications including protection of magnetic media and recording heads. Effective application of this technology requires an improved understanding of the influence of process parameters on the microstructure and hardness of the deposited films. In this work, we use a commercially available filtered cathodic arc to deposit tetrahedral amorphous carbon at several deposition angles.
Deposition of Diamondlike Carbon Films and Structural, Optical, and Electron Emission Characteristics
Authors: Choi S. W. , Paek M. C. , Lee J. H. , Hong S. U. , Nam K. S. 
Published: April 2011

ABSTRACTWe have deposited thin films of diamond-like-carbon by plasma enhanced chemical vapor deposition, and examined the electron emission characteristics of the optimized DLC-coated field emitters. The bonding spectra and microstractures are controlled by energetic ions depending on deposition parameters which affect the structural, optical, and electrical characteristics. Raman spectra and IR analysis identify that as-deposited DLC contains mixtures of sp2- and sp3-bonding with a wide range of hydrogen, but annealing causes its conversion to graphite structure due to a depletion of hydrogen. From the measurement of field emission characteristics, turn-on gate voltage is lowered to 50 V and anode current is increased for DLC-coated Si field emitter tip arrays.
Supercritical Fluid Phase Separations Induced by Chemical Reactions
Authors: Ree Francis H. , Viecelli James A. 
Published: April 2011

ABSTRACTStatistical mechanical studies predict that a chemically reactive system containing species composed of C, H, N, O atoms can exhibit a phase separation into a N2-rich and a N2-poor phase. The present work is concerned with the effect of the fluid phase separation upon addition of F atoms to the system. Our study shows that F atoms mainly appear as a constituent of HF in a N2-poor fluid phase up to a certain pressure beyond which they occur as CF4 in a N2-rich phase and that the phase separation may be abrupt in a thermodynamic sense. The pressure at the phase boundary can occur at about 30 GPa at 3000 K and about 10 GPa to 20 GPa at 1000 K. Some of these ranges may be accessible by present-day experimental high-pressure techniques. We discuss implications of this study to detonation physics.
Electronic Structure Under Extreme Uniaxial Strains: Conductance in Metallic Nanocontacts.
Authors: Sánchez-Portal Daniel , Untiedt Carlos , Soler José M. , Sáenz Juan J. , Agraït Nicolas 
Published: April 2011

ABSTRACTIn this work we address the behaviour of electronic structure under uniaxial stress, by first-principles calculations and experiments of conductance in nanometer-sized metallic contactes of Au and Al. These contacts are shown to be specially suitable for this purpose. The conductance behaviour is related to the change with strain of Fermi surface. Both experimental and theoretically Au behaves like the free electron gas but Al has the opposite behaviour.
High-Pressure, High-Temperature Syntheses of Super-Hard α-Rhombohedral Boron-rich Solids in the B-C-N-O
Authors: Hubert Hervé , Garvie Laurence A.J. , Devouard Bertrand , McMillan Paul F. 
Published: April 2011

ABSTRACTWe prepared α-rhombohedral (α-rh.) B-rich materials in the B-C-N-O system at high-pressures and temperatures. Samples were synthesized using a multianvil device and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and parallel electron energy-loss spectroscopy (PEELS). The B-C-O compounds were obtained by reducing B2O3 with B, or mixtures of B and C between 1 to 10 GPa and 1200° and 1800° C In the B-O system we synthesized boron suboxide (nominally B6O) of high purity, crystallinity, and close to stoichiometric. Quantitative analyses give B6O0.95 and B6O0.77 for high-pressure and room-pressure samples, respectively. Between 4 to 5.5 GPa, B6O formed as macroscopic near-perfect regular icosahedra (to 30 μm in diameter). In the B-C-O system, intermediate phases were prepared showing evidence of solid solution between B4C and B6O. Boron carbide crystals, to 20 μm, containing a significant amount of O, typically B6C1.1O0.33 and B6C1.28O0.31, were grown for mixtures in which B and C were reacted with excess B2O3 at 7.5 GPa and 1700 °C. We also report the first conclusive bulk synthesis of a new boron nitride, B6N1-x. This subnitride was synthesized from B and hexagonal BN at 7.5 GPa and 1700 °C. XRD and PEELS shows that the boron subnitride has the α-rh. B structure and average composition B6N0.92
Progress in the Search for Metallic Hydrogen: 342 GPa
Authors: Narayna Chandrabhas , Orloff Jon , Ruoff Arthur L. 
Published: April 2011

ABSTRACTThe experimental search for metallic hydrogen has been active for over two decades with the first claims being published in 1975, followed by several others all of which failed to pass the test of time. The present paper describes experiments in which several important changes were made in the experiment, compared to those performed previously, which enabled us to reach a pressure of 342 GPa. The path was strewn with 15 pairs of carefully chosen diamonds. At 342 GPa visible light was readily transmitted through the sample proving that it was not yet an alkali metal. The reasons why it has been so difficult to achieve the required pressure for metallization will be discussed.
Controlling the surface cleanliness of nanostructured alpha-iron and M50 type steel (Fe-Cr-Mo-V-C) powders
Authors: Schady S. F. , Law C. C. , Gell M. , Gonsalves K. E. , Morral J. E. , Rangarajan S. P. 
Published: April 2011

ABSTRACTThe cleaning effectiveness of flowing hydrogen to remove oxygen (adsorbed and metal oxide) and carbon (elemental, carbides and carbon-hydrogen complex) from the surface of nanostructured alpha-iron and M50 type steel (Fe-Cr-Mo-V-C) alloy powders was investigated. The hydrogen treated powders and consolidated material were examined by bulk chemical analysis and metallographic examination. The trends in the cleaning effectiveness compared favorably with predictions from Richardson and Jeffies plots of metal-metal oxide equilibria.