bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combinatorial Fabrication and Study of Luminescent Nanocrystalline Si Particles Embedded in a SiO2 Matrix
Authors: Fonseca Luis F , Resto Oscar , Weisz S. Zvi , Shinar Joseph 
Published: April 2011

AbstractThe combinatorial fabrication of nanocrystalline Si particles embedded in a SiO2 matrix (nc-Si:SiO2) by RF co-sputtering of Si and SiO2 targets is described. The peak of the photoluminescence (PL) spectra of the films varies systematically from 760 to 600 nm, consistent with the presumed systematic variation in the size distribution of the embedded Si particles. The correlation between the optical properties of the samples and the formation parameters is also analyzed.
Model silica pores with controllable surface chemistry for molecular dynamics simulatinos
Authors: Gulmen Tolga S. , Thompson Ward 
Published: April 2011

AbstractModel amorphous silica pores have been developed for use in molecular dynamics simulations. Specifically, roughly cylindrical pores have been constructed with hydrophilic, hydroxyl-terminated surfaces. The approach is designed to allow systematic variation of the pore radius and surface functionality. Thus, these pores are suitable for studying the variability in solvent structure, energy transfer and reaction dynamics occurring inside the pore due to surface modification. The method is described and the properties of the generated pores are discussed.
Surface-Passivant Dependence of Dynamic Charging Effect in Alkanethiolate-Passivated Au Nanoparticles on Graphite Substrates Studied by Photoelectron Spectroscopy
Authors: Tanaka Akinori , Imamura Masaki , Yasuda Hidehiro 
Published: April 2011

AbstractWe have performed a photoemission study of various alkanethiolate- (AT-) passivated Au nanoparticles with diameter of 4 nm on the highly oriented pyrolytic graphite (HOPG) substrates. It is found that the photoemission spectra in the vicinity of Fermi level of all the present AT-passivated Au nanoparticles on the HOPG substrates do not exhibit the usual metallic Fermi edge, with the steep slope being away from the Fermi level. Moreover, it is found that these spectral features depend on the surface-passivant molecules. We attribute the unusual spectral features in the vicinity of Fermi level to the dynamic charging effect in photoemission final-state, indicative of the interaction between the nanoparticle and substrate through the surface-passivants on a femtosecond time scale.
Ballistic and diffusive random walks in confinement
Authors: Levitz Pierre , Grebenkov D. , Petit D. , Vigouroux C. 
Published: April 2011

AbstractPorous materials, concentrated colloidal suspensions are example of confining systems developing large specific surface and presenting a rich variety of shapes. Such an interfacial confinement strongly influences the molecular dynamics of embedded fluids and the diffusive motion of entrapped Brownian particles. An individual trajectory near the interface can be described as an alternate succession of adsorption steps and random flights in the bulk. Statistical properties of these random flights in various interfacial confining systems are determinant to understand the full transport process. Related to first passage processes, these properties play a central role in numerous problems such as the mean first exit time in a bounded domain, heterogeneous catalytic reactivity and nuclear magnetic relaxation in complex and biological fluids. In the present work, we first consider the various possibilities to connect two points of a smooth interface by a random flight in the bulk. Second, we analyze at the theoretical and experimental points of view a way to probe Brownian flights statistics. Implications concerning diffusive transport in disordered porous materials are discussed.
Surface Plasmon Excitation in Three-dimensional, Ordered, Gold Nanocrystal Arrays Using a Prism Coupler
Authors: Yang Kai , Fan Hongyou , O'Brien Michael J. , Malloy Kevin J. , Lopez Gabriel P. , Brinker Jeffrey C. , Sheik-Bahae Mansor , Sigmon Thomas W. 
Published: April 2011

ABSTRACTWe report plasmon excitation in 3-dimensional, ordered, gold nanocrystal(NC) arrays using a prism coupler. The gold NCs are arranged in the silica host matrix in a face-centered cubic lattice with the mono-dispersion gold core size of ∼3 nm. We observed the collective optical behavior of the gold NC array and found a blue shift in the plasmon absorption peak with increasing gold volume fraction (Au loading). Plasmon resonance bands centered at 536, 530 and 520 nm are measured for gold NC arrays with gold loading factors of 0.25, 0.5 and 1.0, respectively. The corresponding angular spectra of the gold NC arrays show resonance angles at 60.3, 63.3 and 66.4 degree.
Simple Estimation of Nanoparticle Diameter Produced in a Flow Tube Reactor
Authors: Kuwana Kazunori , Saito Kozo 
Published: April 2011

ABSTRACTIn many carbon nanotube synthesis methods, catalyst nanoparticles are formed via pyrolysis of a precursor such as ferrocene. Since the diameter of a carbon nanotube is usually determined by the diameter of the catalyst nanoparticle, it is of great importance to control the size of nanoparticles. To do so, it is necessary to identify the key reaction parameters that influence nanoparticle size. For engineering purposes, a simple analytical model offers a convenient first estimation of particle diameter. It also clarifies the dependence of nanoparticle diameter on each reaction parameter and enhances our understanding of the formation mechanism of nanoparticles. This paper presents a simplified model that can calculate the diameter of particles and the model's analytical solutions.
Structural evolution of La0.9Sr0.1Cr0.9Co0.1O3 thin films for SOFCs and catalysis
Authors: Coratolo Anthony Mario , Orlovskaya Nina , Johnson Christopher , Gemmen Randal 
Published: April 2011

ABSTRACTThe deposition of La0.9Sr0.1Cr0.9Co0.1O3 thin films by RF magnetron sputtering and annealing leads to the formation of a conducting perovskite film for the protection of metallic interconnects in SOFCs. The nanoporous structure, formed by a two-step phase transition, may also be a promising candidate for catalytic applications.
Optical Gas Sensor Using Cobalt Oxide Thin Film Prepared by Pulsed Laser Ablation
Authors: Nam Hyun-Jeong , Sasaki Takeshi , Koshizaki Naoto 
Published: April 2011

ABSTRACTGas sensors based on optical absorption changes in thin films are of interest for detection of various gases such as CO, NO, H2. Optical gas sensors have several advantages over conventional electronic gas sensors, including the potential for higher sensitivity, reduced signal noise, and compatibility with combustible gases. Pulsed laser deposition (PLD) is an excellent method to prepare thin films with controllable thickness, composition and microstructures. Recently, our group reported that films of cobalt oxide prepared by PLD exhibit remarkably high sensitivity), showing an absorbance change in CO gas 70 times greater than those prepared by sputtering methods). Here we examine the effect of film microstructure and composition on CO gas sensing properties in order to identify the origin of the high sensitivity. Cobalt oxide films were prepared by PLD from a CoO target in an inert argon gas at various pressures. Films prepared near vacuum were smooth and continuous while the porosity and grain size increased linearly with pressure. In addition the pressure affected the composition and the thickness of the films. Data on the detection of CO gas suggests a direct relationship between sensitivity to CO gas and the effective surface area of films. We will discuss how the ablation plume can be used to tune the surface area for optimal sensitivity, and will demonstrate origin of the high detection sensitivity based on the structural changes with detecting gas.
First-Principles Study of Helical Silver Single-Wall Nanotubes and Nanowires
Authors: Elizondo Shelly L. , Mintmire John W. 
Published: April 2011

ABSTRACTWe investigate the electronic structures of extended helical silver single-wall nanotubes (AgSWNTs). Because these helical nanotubes are essentially comprised of n-atom strands winding about the nanotube's axis, we systematically examine, strand by strand, the electronic properties and the number of conduction channels associated with these structures. Herein, we study a special case of high-symmetry nanotubes. Nanotubes with sufficiently large radii were also calculated with a silver atomic chain inserted along the nanotube's axis. The analysis is carried out within a first-principles, all-electron self-consistent local density functional approach (LDF) adapted for helical symmetry. Modeling helical silver (or gold) single-wall nanotubes entails rolling up a sheet of atoms and mapping the atoms onto the surface of a cylinder, comparable to rolling up a graphite sheet for a carbon nanotube. It is well known that controlling the size and shape of silver and gold nanostructures results in the ability to tailor the optical and catalytic properties of these materials. In this preliminary study, we consider changes in the electronic structures of these materials as each nanotube is built strand by strand.
Synthesis and Properties of Barium Titanate Thin Films Deposited on Copper Foil Substrates
Authors: Ihlefeld Jon , Borland William , Maria Jon-Paul 
Published: April 2011

AbstractBarium titanate thin films have been deposited on copper foils in the absence of interfacial layers via a chemical solution process. The dielectric – base metal stacks have been processed in reductive atmospheres such that substrate oxidation is avoided while allowing the perovskite film phase to crystallize. This accomplishment has facilitated the pursuit of a new embedded capacitor technology offering compatibility with polymer printed wiring boards and capacitance densities in excess of 2.5 µF/cm2. This represents a distinct improvement beyond conventional foil-based capacitor strategies. Finally, two critical phenomena will be discussed: (1) the effect of grain size on the dielectric properties of barium titanate thin films and (2) the effect of the B-site substituent Zr on the lattice, microstructure, and dielectric properties. Most importantly, high processing temperatures have allowed for microstructural and dielectric properties similar to well-prepared bulk ceramics, including average grain diameters greater than 0.1 µm, relative permittivities in excess of 2000, and coercive fields below 10 kV/cm. These properties will be discussed in the context of bulk ceramic and thin film reference data and with regard to integration into printed wiring boards.
The Properties of Ferroelectric Domain of PLT Thin Films Prepared by RF Magnetron Sputtering
Authors: Liu Hong , Pu Zhaohui , Wang Zhihong , Huang Huidong , Li Yanrong , Xiao Dingquan , Zhu Jianguo 
Published: April 2011

AbstractLanthanum-modified lead titanate (PLT) ferroelectric thin films were fabricated by the RF magnetron sputtering system on Pt/Ti/SiO2/Si(100) substrates. The x-ray diffraction (XRD) patterns of the PLT films showed that the pure perovskite structure was formed in the PLT thin films. The Piezoresponse Force Microscopy (PFM) was used for determining the domain structure of these films. It was found that the 90 degree domain was the main domain structure of PLT thin films. It was found that the PLT films prepared by RF sputtering have relatively large pyroelectric coefficient γ=2.20×10-8C·(cm2·K)-1 and relatively high figures of merit for current responsivity, voltage responsivity and specific detectivity.
Initial Growth Behavior of Ultra-Thin c-Axis-Oriented Epitaxial SrBi2Ta2O9 films on SrTuO3
Authors: Takahashi Kenji , Suzuki Muneyasu , Yoshimoto Mamoru , Funakubo Hiroshi 
Published: April 2011

Abstractc-axis-oriented epitaxial SrBi2Ta2O9 ultra-thin films were grown by pulse-gas-introduced metalorganic chemical vapor deposition (pulsed-MOCVD) on (100)SrTiO3 single crystal substrates with atomic scale step structure and their growth behavior was investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Minimum growth unit was found to be “ghalf-unit-cell” of SrBi2Ta2O9. Height of steps and width of terraces observed at SrBi2Ta2O9 film surface were in good agreement with those at SrTiO3 substrate surface. This shape transfer was induced by lattice displacement of SrBi2Ta2O9 along c-direction formed at atomic step on SrTiO3 substrate. In-plane growth of half-unit-cell SrBi2Ta2O9 2D-islands striding across the step walls was observed. It was considered to be a special phenomenon for c-axis-oriented films of layer-structured compounds due to their large crystal anisotropy and/or several times larger half-unit-cell height than single step one of SrTiO3.
Microwave Phase Shifters: Epitaxial Growth by Pulsed Laser Deposition of Dielectric Ba0.5Sr0.5TiO3 Thin Films on MgO
Authors: Tse YauYau , Suherman P. S. , Jackson T. J. , Jones I. P. 
Published: April 2011

AbstractBa0.5Sr0.5TiO3 (BSTO) thin films were grown on (001) MgO using pulsed-laser deposition (PLD). The microstructures of in-situ and ex-situ annealed BSTO films were studied by X-ray diffraction and transmission electron microscopy (TEM). The films showed a cube on cube epitaxial relationship with <100> BSTO // <100> MgO. They were essentially single crystals with a columnar structure and possessed smooth surfaces. The interfaces of the BSTO films and substrates were atomically sharp, with misfit dislocations. Better crystallinity and full strain relaxation was obtained in films grown in 10-1 mbar oxygen and annealed ex-situ. A 30% increase in dielectric tuneability was achieved compared with in-situ annealing and deposition at 10-4 mbar. Threading dislocations are the dominant defects in the films grown in 10-1 mbar oxygen and annealed ex-situ, while the films with in-situ annealing show columnar structures with low angle boundaries.
Trap Charge Density at Interfaces of MOCVD Pt(Ir)/PZT/Ir(Ti/SiO2/Si) Structures
Authors: Delimova Lyuba A. , Grekhov I. V. , Mashovets D. V. , Shin Sangmin , Koo June-Mo , Kim Suk-Pil , Park Youngsoo , Afanasjev V. P. , Afanasjev P. V. , Petrov A. A. 
Published: April 2011

AbstractA method providing estimation of the trap density at metal/ferroelectric interfaces of a depleted ferroelectric film located between back-to-back Schottky barriers has been developed. The method is based on the recharge of interface traps induced by external bias pulse applied to the metal/ferroelectric/metal structure. It is shown that the transient current under bias pulse can be controlled by the traps recharge on the reverse-biased interface. Using the method, the trap charge density on interfaces of MOCVD Pt/PZT/Ir(Ti/SiO2/Si) and Ir/PZT/Ir(Ti/SiO2/Si) capacitors were found from transient current measurements.
Intrinsic defects in high purity semi-insulating 6H SiC
Authors: Savchenko D. V. , Kalabukhova E. N. , Lukin S. N. , Sudarshan Tangali S. , Khlebnikov Yuri I. , Mitchel William C. , Greulich-Weber S. 
Published: April 2011

AbstractElectron paramagnetic resonance (EPR) and photo EPR measurements were performed on undoped semi-insulating (SI) 6H SiC material grown by the physical vapor transport (PVT) method. EPR lines from a carbon-related surface defect, two photosensitive high temperature stable intrinsic defects with S=1/2 and shallow nitrogen and boron were observed. The EPR spectrum of the intrinsic defect labeled XX was observed in the dark and consists of three single lines XX1, XX2, XX3 due to three inequivalent sites in the 6H SiC. The second defect labeled PP appeared in EPR spectrum during photo-excitation of the SI 6H SiC and consisted of a single EPR line. The photo EPR data placed the energy level of the defects in the region EV + 1.24 ÷ 1.29 eV. The EPR parameters and symmetry behavior of XX agree well with those of the carbon vacancy-related Ky center observed in p-type electron irradiated 6H SiC and we tentatively identify the XX defect with VC+. The electronic processes occurring in undoped SI 6H SiC under photo-excitation are also described.
High Quality Uniform Thick Epitaxy of 4H-SiC for High Power Device Applications
Authors: Zhang Jie , Mazzola Janice , Romano Esteban , Hoff Carl , Mazzola Mike , Casady Janna , Casady Jeff 
Published: April 2011

AbstractGrowth of thick SiC epilayers has been investigated in a horizontal hot-wall CVD reactor capable of growing 3x2-in wafers or single wafer with a diameter up to 100mm. Good uniformity of lower than 3% for thickness and lower than 20% for doping has been obtained on 2-in or 3-in epi wafers with thickness of 60 - 120 μm. Low intentional nitrogen doping of 5.8x1014 cm-3 was achieved on a 3-in epi wafer with a thickness of 120 μm. A higher growth rate of 10 μm/h was achieved while good uniformity was maintained. Surface morphology of the thick epilayers was carefully examined and smooth surface was observed for epilayers thicker than 100 μm. The defect density of the thick epilayers was also discussed and the high purity of the thick epi was verified by low temperature PL measurement.
High Power SiC MESFETs
Authors: Harris Christopher , Konstantinov Andrei O , Svedberg Jan-Olov , Ray Ian , Hallin Christer 
Published: April 2011

AbstractThe development of high power, high efficiency silicon carbide RF MESFETs is reported. High power densities of over 3W/mm have been measured for devices with total power output in excess of 25W. The devices have been fabricated using a novel lateral epitaxy technique. The MESFET employs a buried p-type depletion stopper in order to suppress short channel effects and increase the operation voltage. The use of the depletion stopper also allows high RF signal gain, while maintaining high voltage operation capability. Single-cell components measured on-wafer demonstrate an Ft of 10 GHz and a high unilateral gain.Packaged 6-mm RF transistors have been evaluated using amplifier circuits designed for operation in classes A, AB or C. Operation in class AB demonstrated a saturated power of 20 W and a P1dB of 15W with a linear gain of over 16 dB at Vdd of 60 V for 2.25 GHz operation. Maximum drain efficiency is 56% for class AB operation, 48% at 1 dB compression point and 72% for class C at 2.25 GHz.
950V, 8.7mohm-cm2 High Speed 4H-SiC Power DMOSFETs
Authors: Ryu Sei-Hyung , Jonas Charlotte , Heath Bradley , Richmond James , Agarwal Anant , Palmour John 
Published: April 2011

AbstractFabrication and characteristics of high voltage, high speed DMOSFETs in 4H-SiC are presented. The devices were built on 1.2×1016 cm-3 doped, 6 mm thick n-type epilayer grown on a n+ 4H-SiC substrate. A specific on-resistance of 8.7 mW-cm2 and a blocking voltage of 950 V were measured. Device characteristics were measured for temperatures up to 300oC. An increase of specific on-resistance by 35% observed at 300oC, when compared to the value at room temperature. This is due to a negative shift in MOS threshold voltage, which decreases the MOS channel resistance at elevated temperatures. This effect cancels out the increase in drift layer resistance due to a decrease in bulk electron mobility at elevated temperature, resulting in a temperature stable on-resistance. The device operation at temperatures up to 300 oC and high speed switching results are also reported in this paper.
Electron-beam Directed Layer-by-Layer Assembly of Dendrimer Scaffold for Biomolecule Patterning
Authors: Bhatnagar Parijat , Mark Sonny S , Kim Il , Chen Hongyu , Schmidt Brad , Lipson Michal , Batt Carl A 
Published: April 2011

AbstractA method for patterning biomolecules using electron beam (e-beam) lithography has been developed. First, a non-biofouling poly (ethylene glycol) terminated self-assembled monolayer (SAM) was deposited on a silicon oxide substrate. This SAM was then ablated by e-beam to create patterns aligned with the pre-existing features on the wafer. Aldehyde-terminated polyamidoamine (PAMAM) dendrimers were assembled in a layer-by-layer fashion in the ablated patterns to allow the covalent immobilization of oligonucleotide probes. The aminated oligonucleotides were attached using Schiff base chemistry followed by reductive amination. The functionality of the attached oligonucleotides was demonstrated by the hybridization of fluorescently labeled complementary target oligonucleotides. The hybridized target oligonucleotides could be stripped and the regenerated surface bound probe oligonucleotides could be rehybridized with complementary target oligonucleotide.
A Novel Mechanical Method to Measure Shear Strength in Specimens Under Pressure
Authors: Escobedo Juan Pablo , Field David , Lassila David , Leblanc Mary 
Published: April 2011

ABSTRACTA new experimental apparatus has been developed for performing shear tests on specimens held under moderately high hydrostatic pressures (on the order of 4 GPa). This testing procedure experimentally determines the pressure-dependent shear strength of thin foil specimens. The experiments provide calibration data for models of materials subjected to extreme pressures such as the Steinberg-Guinan hardening model and can assist in model validation for discrete dislocation dynamics simulations, among others. This paper reports the development of the experimental procedures and the results of initial experiments on thin foils of polycrystalline Ta performed under hydrostatic pressures ranging from 1 to 4 GPa. Both yielding and hardening behavior of Ta are observed to be sensitive to the imposed pressure.
Chemical, Mechanical and Electrical Properties of Glassy Polymeric Carbon
Authors: Muntele Iulia , Muntele Claudiu I. , Minamisawa Renato , Chhay Bopha , Ila Daryush 
Published: April 2011

ABSTRACTGlassy Polymeric Carbon (GPC) is obtained by a molding technique, in various shapes, from a phenolic resin precursor. The heat treatment of the precursor is achieved in three stages up to 1000 °C. Similar GPC materials produced in our laboratory displayed large strain to failure ratio, small thermal expansion coefficient and low density. Like all carbon forms, is attacked by oxygen, especially atomic oxygen. Nevertheless the kinetics for reaction with atmospheric oxygen is very slow. We investigated the composition and structural changes of the phenolic precursor as a function of temperature and evaluated materials stability when exposed to high temperatures in presence of hydrogen or oxygen.
Improvement on Thermoelectric Characteristics of Layered Nanostructure by Ion Beam Bombardment
Authors: Zheng Bangke , Budak S. , Muntele C. , Xiao Z. , Celaschi S. , Mutele I. , Chhay B. , Zimmerman R. L. , Holland L. R. , Ila D. 
Published: April 2011

ABSTRACTWe made p-type nanoscale super lattice thermoelectric cooling devices which consist of multiple periodic layers of Si1−x Gex / Si, The thickness of each layer ranges between 10 and 50 nm. The super lattice was bombarded by 5 MeV Si ion with different fluencies aiming to form nano-cluster quantum dot structures. We estimated the thermo-electric efficiency of the so fabricated devices, measuring the thin film cross plane thermal conductivity by the 3rd harmonic method, measuring the cross plane Seebeck coefficient, and finally measuring the cross plane electric conductivity before and after ion bombardment. As predicted, the thermo-electric Figure of Merit of the films increases with increasing Si ion fluencies. In addition to the effect of quantum well confinement of the phonon transmission, the nano-scale crystal quantum dots produced by the incident Si beam further adversely affects the thermal conductivity by absorbing and dissipating phonon along the lattice, and therefore further reduces the cross plane thermal conductivity, This process increases the electron density of state therefore increasing Seebeck coefficient, and the electric conductivity.