bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modification of Spontaneous Emission from Periodic Array of Spherical Polystyrene Particles Containing Fluorescent Molecules
Authors: Yamasaki T. , Tsutsui T. 
Published: April 2011

AbstractEmissive behavior of dye molecules embedded in the systems with the size of visible wavelength were studied. The structures consisted of close-packed arrays of spherical dielectric particles with diameter of submicrometer were fabricated. Photoluminescence from selfassembled arrays of dye-doped polystyrene microspheres were examined. In this systems, partial suppression of spontaneous emission by ordered structures were observed. Electricallypumped emission from organic light emitting diodes with highly ordered arrays of silica microspheres were attempted.
Superconductivity of κ-(BEDT–TTF)2 Cu[N(CN) 2]Br: Isotope Effect Revisited
Authors: Tokumoto M. , Kinoshita N. , Tanaka Y. , Anzai H. 
Published: April 2011

AbstractIn 1991, we reported a normal isotope effect in organic superconductor κ-(BEDT–TTF)2Cu[N(CN)2]Br, when all the hydrogen atoms of BEDT – TTF were replaced with deuterium. In other words, Tc was depressed by as much as 0.9 K, in contrast to the “inverse isotope effect” commonly observed in 10K-class organic superconductors. Recently, it was reported that the deuterated κ-(BEDT–TTF)2Cu[N(CN)2]Br shows an insulating nature when cooled very rapidly. Therefore, it is necessary for us to reexamine the superconducting transition of both deuterated and undeuterated κ- (BEDT – TTF)2Cu[N(CN)2]Br by SQUID measurements with special attention to the cooling speed. We studied the effect of cooling rate ranging from 10 K/min down to as slow as 0.02 K/min, and observed a significant effect not only on the superconducting transition temperature Tc but also on the superconducting volume fraction.
Alternating-Current Light-Emitting Diodes and their Transient Characteristics: Response Time and Carrier Transport
Authors: Pal A. J. , öStergÅrd T. , österbacka R. , KÄllman K-M. , Stubb H. 
Published: April 2011

AbstractWe report the fabrication and characterization of alternating current light-emitting diodes (LEDs) with quinquethiophene as the emitting material. We have obtained equal electroluminescence intensity in both bias sections. From the frequency response of the LEDs, we have estimated the device response times and compared them with the response times obtained from the transient response of dc LEDs. Langmuir-Blodgett film deposition technique has been employed to control the thickness of the emitting layer on the molecular scale. We have shown that the response times originate from the accumulation rather than the transit of charge carriers. We have compared the photo- and electroluminescence spectra of QT LEDs.
Nonvolatile, Reversible Writing of Electronic Nanostructures in Epitaxial Ferroelectric / Metallic Oxide Heterostructures using a Field Effect
Authors: Ahn C. H. , Tybell T. , Antognazza L. , Char K. , Hammond R. H. , Beasley M. R. , Fischer Ø. , Triscone J.-M. 
Published: April 2011

ABSTRACTUsing scanning probe microscopy, we have written nonvolatile electronic nanofeatures in the metallic perovskite oxide SrRuO3. The structures were written in epitaxial thin film Pb(Zr0.52Ti0.48)O3 (PZT) / SrRuO3 heterostructures by locally switching the polarization field of the ferroelectric PZT layer with an atomic force microscope (AFM). The resulting field effect changes the sheet resistance of the SrRuO3 layer by up to 300 ohms per square. Using the AFM as an electric field microscope, it is also possible to visualize the charge distribution of the written areas on the PZT surface. Large areas of up to 100 μm2 have been polarized and imaged with submicrometer resolution, with the smallest features having linewidths of 170 nm. This approach to local electronic doping is reversible and allows one to write nonvolatile submicron electronic features in two dimensions without lithographic steps or permanent electrical contacts required.
Suppression of the Tetragonal Distortion in Thin Pb(Zr,Ti)O3 Films Grown on MgO(001)
Authors: Kang H. C. , Noh D. Y. , Je J. H. , Kim H. K. 
Published: April 2011

ABSTRACTThe paraelectric cubic to ferroelectric tetragonal phase transformation of thin Pb(Zr,Ti)O3/MgO(001) films was studied in synchrotron x-ray scattering experiments. As the thickness of the film decreases, the transition temperature and the amount of the tetragonal distortion were decreased continuously. The thinnest 250 Å thick film was purely composed of the c-type domains in the ferroelectric tetragonal phase. Based on this, we propose a model for the domain structure of the tetragonal PZT/MgO(001) film that is different from the ones suggested in literature. We attribute the suppression of the transition to the substrate effect that prefers the c-type domains near the interface, and reduces the tetragonal distortion to minimize the film-substrate lattice mismatch.
Correlation Between In Situ Optical Emission Spectroscopy in a Reactive O2 / AR RF Magnetron Sputtering Discharge and PZT Thin Film Composition
Authors: Ayguavives F. , Aubert P. , Ea-Kim B. , Agius B. 
Published: April 2011

ABSTRACTLead zirconate titanate (PZT) thin films have been grown by rf magnetron sputtering on Si substrates from a metallic target of nominal composition Pb1.1(Zr0.4 Ti0.6 in a reactive argon / oxygen gas mixture. During plasma deposition, in situ Optical Emission Spectroscopy (OES) measurements show clearly a correlation between the evolution of characteristic atomic emission line intensities (Zr - 386.4 nm, Ti - 399.9 nm, Pb - 405.8 nm and O - 777.2 nm) and the thin-film composition determined by a simultaneous use of Rutherford Backscattering Spectroscopy (RBS) and Nuclear Reaction Analysis (NRA).
The Effects of High Temperature Annealing and Composition on the Dielectric Properties of Thin Films of BaxSrzTiO3
Authors: Carter Adriaan C. , Horwitz James S. , Chrisey Douglas B. , Pond Jeffrey M. , Kirchoefer Steven W. , Chang Wontae. , Loferski Patricia 
Published: April 2011

ABSTRACTSingle phase, (100) oriented Ba0.5Sr0.5TiO3 films have been deposited by pulsed laser deposition onto (100) LaAIO3, SrTiO3, MgO substrates. The dielectric properties of these films were measured using interdigitated capacitors as a function of DC bias and temperature at 1 MHz and as a function of DC bias at 1 to 20 GHz at room temperature. Deposited films were annealed over a temperature range of 900 to 1350 C for 1 to 8 hours to observe its effect on dielectric properties. Chemical analysis on films deposited from stoichiometric targets showed the films to be up to 6% deficient in Ba and Sr under typical PLD deposition conditions. Optimal annealing conditions and target stoichiometries for minimizing dielectric loss and maximizing tuning are discussed.
Compositional Control of Ferroelectric Domain Structures in Eteroepitaxial PLZT Thin Films
Authors: Lee K. S. , Kang Y. M. , Baik S. 
Published: April 2011

ABSTRACTThe mechanism and control of ferroelectric domain formation in heteroepitaxial (Pb1−xLax)(ZryTi1-y)O3 (PLZT) thin films grown on MgO(001) substrates have been investigated as a function of composition and temperature. Pulsed laser deposition and RF magnetron sputtering techniques were used and optimized to fabricate epitaxial thin films with varying La and/or Zr concentrations. Periodic 9° domain structures were developed when the film transformed from the cubic phase to the tetragonal phase during cooling after deposition. As a result of the tetragonality of the films, the domain formation induced slightly tilted twin structures. All films were grown highly c axis oriented and the degree of c axis orientation was improved with increasing La or Zr concentration. Experimental observations of the 90° domain evolution in films have been carried out in-situ and ex-situ using conventional and synchrotron X-ray diffraction and demonstrated that the most important parameter affecting the domain structure and its abundance is the transformation strain at the Curie temperature, which can be varied systematically by changing the concentration of La and/or Zr in the PLZT system.
(Mn, Sb) Doped-PZT/YBa2Cu3O7-y Heterostructure for IR Detector Array
Authors: Xu Y. Q. , Wu N. J. , Liu D. , Ignatiev A. 
Published: April 2011

ABSTRACTMn and Sb doped-PZT (PMSZT)/YBa2Cu3O7−y (YBCO) heterostructures have been integrated with YSZ/Si substrates for fabrication of infrared (IR) detector arrays. PMSZT films with good epitaxy on c-oriented YBCO conducting oxide electrodes have been successfully grown by a pulsed laser ablation deposition. The ferroelectric properties of the PMSZT films show good hystersis loops with a coercive field Ec, of 70 kV/cm and a remnant polarization Pr, of 15μC/cm2. I-V curves show that the PMSZT films have high electrical field breakdown strength with values exceeding 400kV/cm. Doping Mn and Sb into PZT has been shown to not only decrease the Curie temperature Tc from 350°C for PZT to 175°C for PMSZT, but also to enhance the IR responsivity of the pyroelectric thin films. PMSZT detectors have a pyroelectric coefficient of 45nC/cm2K at 25°C and 148nC/cm2K at 88°C, and pyroelectric figures of merit, Fv of 15.5 × 10−11 C. cm/J and Fd of 9.5 × 10−9 C. cm/J at 25°C. The measured normalized detectivity D* in the 2.5μm--19.5μm wavelength range varies from 2.5×108cm. Hz1/2/W to 6.0×108cm. Hz1/2/W.
MOCVD of Alkaline Earth Titanates for Integrated RF Capacitors
Authors: Stauf G. T. , Seegel C. , Watts R. K. , O'Bryan H. M. 
Published: April 2011

ABSTRACTThe high permittivity of BaSrTiO3 (BST) gives it the potential to replace discrete “passive” capacitors used in portable and wireless applications with integrated capacitors. Bringing thin film devices directly onto Si and GaAs chips shortens lead length and improves overall circuit Q values by reducing inductance, important at RF frequencies. A metalorganic chemical vapor deposition (MOCVD) process has been developed for this purpose. By modifying the basic BST stoichiometry, we have demonstrated charge storage densities up to 3,000 nF/cm2 with leakages below 10−8 A/cm2 at 3 V, and second order dielectric nonlinearities below 100 ppm/V2. For stoichiometric BST, Q factors are as high as 500 at kHz frequencies, and evidence suggests that low losses can be retained up through the L and S microwave bands (1 -4 GHz) in the modified titanates. These properties make alkaline earth titanate films suitable for use in decoupling and bypass capacitors, as well as switched capacitor filters.
Orientation Effects on Pyroelectric Properties of Solution - Derived Bismuth Titanate Films
Authors: Khang Tran D. , Buchanan Relva C. 
Published: April 2011

AbstractFerroelectric bismuth titanate (Bi4Ti3O12) thin films with controlled degree of c-orientation were fabricated on Pt/Si substrate by solution spin-casting technique. The degree of c-orientation of the films was characterized by XRD analysis and Raman spectroscopy. Film properties such as dielectric constant, dielectric loss factor, spontaneous polarization, and coercive field varied over the range of (119–87), (0.04–0.015), (8–4 μC/cm2), and (30-20 kV/cm), respectively as the degree of c- orientation of the films increased from 0.3 to 0.85. Values for the pyroelectric coefficient, voltage responsivity, and voltage figure of merit were also evaluated. These properties exhibited strong dependence on the degree of c-orientation of the films and, for highly oriented films, reached values of 9.5 nC/°C. cm2, 62 V/W, and 0.4×10−10 C. cm/J, respectively. The inter-correlation between degree of c-orientation, grain morphology, and pyroelectric properties of the films were explored in this study.
Epitaxial Ferroelectric Oxides for Electro-Optic and Non-Linear Optical Applications
Authors: Wessels B. W. 
Published: April 2011

ABSTRACTFerroelectric oxide epitaxial thin films are potentially important for a variety of guided-wave electro-optic and non-linear optical applications. Metalorganic chemical vapor deposition has been used to synthesize epitaxial thin films of a number of ferroelectric oxides. The films now have sufficient optical quality to enable the fabrication of waveguide devices including electro-optic modulators and optical amplifiers for 1.54 microns.
Structure-Property Relationships of BaCeO Perovskites for the Oxidative Dehydrogenation of Alkanes
Authors: Nenoff T. M. , Jackson N. B. , Miller J. E. , Sault A. G. , Trudeil D. 
Published: April 2011

ABSTRACTThe oxidative dehydrogenation (ODH) reactions for the formation of two important organic feedstocks ethylene and propylene are of great interest because of the potential in capital and energy savings associated with these reactions. Theoretically, ODH can achieve high conversions of the starting materials (ethane and propane) at lower temperatures than conventional dehydrogenation reactions. The important focus in our study of ODH catalysts is the development of a structure-property relationship for catalyst with respect to selectivity, so as to avoid the more thermodynamically favorable combustion reaction. Catalysts for the ODH reaction generally consist of mixed metal oxides. Since for the most selective catalyst lattice oxygen is known to participate in the reaction, catalysts are sought with surface oxygen atoms that are labile enough to perform dehydrogenation, but not so plentiful or weakly bound as to promote complete combustion. Also, catalysts must be able to replenish surface oxygen by transport from the bulk.Perovskite materials are candidates to fulfill these requirements. We are studying BaCeO3 perovskites doped with elements such as Ca, Mg, and Sr. During the ODH of the alkanes at high temperatures, the perovskite structure is not retained and a mixture of carbonates and oxides is formed, as revealed by XRD. While the Ca doped materials showed enhanced total combustion activity below 600°C, they only showed enhanced alkene production at 700°C. Bulk structural and surface changes, as monitored by powder X-ray diffraction, and X-ray photoelectron spectroscopy are being correlated with activity in order to understand the factors affecting catalyst performance, and to modify catalyst formulations to improve conversion and selectivity.
Modeling of the Ion-Beam Growth of Covalently-Bonded Diamondlike Materials
Authors: Hofsäss H. C. , Sebastian M. , Feldermann H. , Merk R. , Ronning C. 
Published: April 2011

ABSTRACTA characteristic ion energy and substrate temperature dependence for the formation of tetra-hedral amorphous carbon (ta-C), cubic boron nitride (c-BN) and related diamondlike materials by ion deposition has been experimentally observed. We present an analytical model for diamondlike film growth that describes the transient modification of the film structure by successive individual ion impact events. Each ion impact is treated as a cylindrical thermal spike with a finite initial width, taking into account energy loss and energy dissipation processes. We show that rearrangement of atoms during a cylindrical spike is the dominant mechanism leading to the formation of the diamondlike phase. The model explains quantitatively the observed ion energy dependence of the sp3 bond fraction in ta-C, as well as the broad range of ion energies for which c-BN growth is observed.
High Rate Deposition of Ta-C:H Using an Electron Cyclotron Wave Resonance Plasma Source
Authors: Morrison N. A. , Muhl S. , Rodil S. E. , Milne W. I. , Robertson J. , Weiler M. , Wang P. Z. , Hutchings I. , Stolojan V. , Brown L. M. 
Published: April 2011

ABSTRACTA compact electron cyclotron wave resonance (ECWR) source has been developed for the high rate deposition of hydrogenated tetrahedral amorphous carbon (ta-C:H). The ECWR provides growth rates of up to 900 A/mm and an independent control of the deposition rate and ion energy. The ta-C:H was deposited using acetylene as the source gas and was characterized in terms of its bonding, stress and friction coefficient. The results indicated that the ta-C:H produced using this source fulfills the necessary requirements for applications requiring enhanced tribological performance.
Tribochemical Reactions of Si Incorporated Diamond-Like Carbon Films During the Initial Transient Period
Authors: Kim Myoung-Geun , Lee Kwang-Ryeol , Eun Kwang Yong 
Published: April 2011

ABSTRACTTribochemical reactions between Si incorporated diamond-like carbon (Si–DLC) films and steel ball were investigated during initial stage of tribo-test. The films were deposited by r.f.–PACVD using mixtures of diluted silane (SiH4:H2=10:90) and benzene gases. Si concentration in the film was varied from 0 to 10 at.% by adjusting the diluted silane fraction in the reaction gases. A rotating type ball-on-disk wear rig was employed for the tribo-test in ambient atmosphere. When the Si concentration was less than 5 at.%, initial transient period of high friction coefficient was commonly observed. After the transient period, the friction coefficient becomes lower with increasing contact cycles. The initial transient period becomes shorter and the starting and maximum friction coefficients in transient period decreased with increasing Si concentration. Composition of the debris on the wear scar surface was analyzed by Auger spectroscopy at various stages in the initial transient period. We observed that when the friction coefficient increased in earlier stage of the transient period, iron and oxygen was observed in the debris. However, decrease in the friction coefficient in the later stage of the transient period was associated with the formation of silicon rich oxide debris. This result supports the friction mechanism of Si-DLC films that the formation of Si rich oxide debris results in low friction coefficient in ambient atmosphere.
Boron Nitride Coatings and Materials for use in Aggressive Environments
Authors: Besmann T. M. , Lee W. Y. , Young J. P. , Xiao H. 
Published: April 2011

ABSTRACTBoron nitride coatings and structures have demonstrated significant resistance to many corrosive environments. These coatings may have application in the protection of sensors needed for measuring a variety of properties such as temperature and chemistry. In addition, boron nitride materials may offer advantages as structural materials in high temperature materials processing. In this study, BN is assessed for use in aluminum smelting.
Structural Characterization of Crystalline Si-C-N Films
Authors: Wang E. G. , Wang Cheng-Zhang , Chen Changfeng , Chen Yan 
Published: April 2011

ABSTRACTHigh quality crystalline Si-C-N films on silicon substrate have been synthesized by bias-assisted hot filament chemical vapor deposition (CVD) using a gas mixture of nitrogen and methane. Scanning electron microscopy images show that the Si-C-N clusters are composed of many columnar crystals with hexagonal facets. X-ray diffraction and transmission electron microscopy analyses confirm the formation of Si-C-N crystals with lattice parameters a=7.06Å and c=2.72Å. First principles calculations are performed for β-Si3–nCnN4 (n=0,1,2,3). The calculated results support the experimental structural characterization and provide further insight into the property of the system. With increasing amount of C substitution, the bulk modulus progressively increases to 4.44 Mbar, comparable to that of diamond (4.43 Mbar), and both a and c are reduced but the ratio c/a shows little variation.
Electrical Conductivity of Shock-Compressed Sulphur, Iodine, Bromine and Water
Authors: Yakushev V. V. 
Published: April 2011

ABSTRACTExperimental investigations of the electrical conductivities of sulphur, iodine, bromine, and water under shock compression are reviewed. The value of sulphur conductivity is approximately 105 Ω−1 m−1 at 30 GPa and increases slowly with pressure up to 110 GPa. The conductivity of iodine is 105 Ω−1 m−1 at approximately 15 GPa and decreases moderately up to 110 GPa. The conductivity of liquid bromine is 12.5 Ω−1 m−1 at 9 GPa and approximately 104 Ω−1 m−1 at 30 GPa. In electrochemical experiments galvanic cells with copper and aluminium electrodes and bromine as an electrolyte were subjected to shock loading and their electrical response was measured. We discovered that the cells produce open circuit voltages of about 0.5 V under shock pressures of 7.4 to 30 GPa. This voltage level clearly shows that the observed electrical signals are electrochemical in nature and connected with an ionic character of bromine conductivity. Analogous experiments were made with water, whose conductivity is ionic at 75 GPa with a value of 2000 Ω−1 m−1.
High-Pressure Synthesis and the Magnetic Properties of Chromium Diantimonide
Authors: Takizawa H. , Uheda K. , Endo T. , Shimada M. 
Published: April 2011

ABSTRACTA new high-pressure polymorph of CrSb2 was synthesized under high-pressure/ temperature conditions of 7–7.7 GPa and 600–650°C. The crystal structure is body-centered tetragonal with the space group 14/mcm, which is assigned to CuAl2-type structure. The experiments under various pressure conditions revealed that the high-pressure polymorph was formed above 5.5 GPa, and the compound crystallized into the low-pressure marcasite-type structure below 5 GPa. The characteristic of the high-pressure phase is the metallic bond nature including the formation of Cr-Cr-Cr linear chain along the c-axis. The compound shows metallic conductivity and itinerant-electron ferromagnetic behavior with the Curie temperature of ca. 160 K.
The Ruby Scale at Megabar Pressures
Authors: Silvera Isaac F. 
Published: April 2011

ABSTRACTDiamond anvil cells revolutionized high pressure research because they provided easy to generate extremely high pressures with an optical window on the sample and an easy-to-use pressure gauge based on the shift with pressure of the ruby fluorescence spectrum. The ruby scale provides an accurate method of determining pressure distributions within samples. However, at pressures above 100 GPa measurement of the ruby fluorescence begins to become difficult due to weakening signals, interference from intense diamond fluorescence, and ultimately, strong absorption of the exciting laser by diamond itself. We shall discuss a number of methods which have been devised to extend the ruby pressure optical gauge to 500 GPa, including quasi-direct pumping of the ruby R-lines.
A Multi-Anvil High Pressure System with Synchrotron X-Ray Probe: New Opportunities for In-Situ Materials Research at Simultaneously High Pressure and Temperature
Authors: Wang Y. , Shen G. , Rivers M. , Sutton S. 
Published: April 2011

ABSTRACTWe describe the multi-anvil, large-volume, high-pressure facility that is being constructed at the GeoSoilEnviroCARS (Sector 13) at the Advanced Photon Source, Argonne National Laboratory. Various multi-anvil, high-pressure apparatus will be used to cover pressure and temperature conditions up to 40 GPa and 3000 °C, respectively, with milimeter to centimeter sized samples. This national facility is open to all users, providing excellent opportunities for high pressure, high temperature experiments.