bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Surface Diffusion Model for Nanotube Growth
Authors: Louchev Oleg A. , Sato Yoichiro 
Published: April 2011

ABSTRACTThe problem of nanotube growth macrokinetics is viewed within the framework of the continuum surface diffusion equation combined with step-flow growth kinetics. The differences in incorporation rates of adatoms approaching the growth steps from “upper” or lower" terraces are taken into account. These differences can lead to the onset of surface island nucleation in front of a propagating step. This effect is able to cause formation of defects in the growing layer and even to inhibit stable step-flow modes of nanotube growth. The segregation effect of a second phase (BN) in front of the propagating of C layer step is considered, suggesting that it may cause increase in BN concentration and nucleation of islands leading to BN inclusions in C layers or the propagation of a BN layer over C layer.
Comparative Study of Solvent Effect on the Electrochemical Deposition of Polythiophene and Polybithiophene
Authors: Wong T. K. S. , Hu X. 
Published: April 2011

AbstractThin films of polythiophene and polybithiophene have been deposited by electrochemical polymerization onto indium tin oxide substrates using two different aprotic organic solvents: acetonitrile and benzonitrile. It was observed that when benzonitrile is used as supporting solvent, the initial deposit is always discontinuous and uniform thin layers could not be obtained. When acetonitrile is the solvent, the deposited layer is continuous. However, both the optical and mechanical properties of the polymer film are inferior. The difference is especially pronounced for thiophene monomers. Characterization results suggest a greater degree of polymerization in benzonitrile solvent.
Electron Irradiated p(VDF-TrFE) Copolymers for Use in Naval Transducer Applications
Authors: Ramotowski T. , Hamilton K. , Kavarnos G. , Zhang Q. , Bharti V. 
Published: April 2011

AbstractRecently, it was discovered that the transduction / strain capability of p(VDF-TrFE) copolymers can be enhanced by more than an order of magnitude by irradiating the copolymer with large doses (40–300 Mrads) of β-particles (1–3 MeV electrons). The goal of this project is to understand how irradiation improves the electromechanical properties of p(VDF-TrFE) copolymers while simultaneously identifying the secondary effects of the irradiation process on the material (not critical to the electromechanical properties) and attempting to separate the two contributions. It has been found that β-irradiation affects the material profoundly in several different manners. Reduction in the melt temperature, degree of crystallinity, and the resulting crystal quality have been observed for increasing doses of β-particles. Similar results have been observed for the Curie transition, especially in the energy associated with, and the breadth otf the transition. In addition, thermogravimetric analysis indicates that irradiation causes both chain scission and network polymer formation. Solid-state NMR results are discussed in reference to postulated dehalogenation, dehydrohalogenation, and olefinic bond formation activities.
A Discussion of Flow Mechanisms in Superplastic Yttria-Stabilized Tetragonal Zirconia
Authors: Berbon Min Z. , Langdon Terence G. 
Published: April 2011

AbstractFlow data are reported for a superplastic yttria-stabilized tetragonal zirconia containing 3 mol % of Y2O3 (termed 3Y-TZP). The data are analyzed using a model for interface-controlled diffusion creep and the results are compared with published data for other samples of 3Y-TZP.
Grain Boundary Engineering of Highly Deformable Ceramics
Authors: Mecartney Martha L. 
Published: April 2011

AbstractHighly deformable ceramics can be created with the addition of intergranular silicate phases. These amorphous intergranular phases can assist in superplastic deformation by relieving stress concentrations and minimizing grain growth if the appropriate intergranular compositions are selected. Examples from 3Y-TZP and 8Y-CSZ ceramics are discussed. The grain boundary chemistry is analyzed by high resolution analytical TEM is found to have a strong influence on the cohesion of the grains both at high temperature and at room temperature. Intergranular phases with a high ionic character and containing large ions with a relatively weak bond strength appear to cause premature failure. In contrast, intergranular phases with a high degree of covalent character and similar or smaller ions than the ceramic and a high ionic bond strength are the best for grain boundary adhesion and prevention of both cavitation at high temperatures and intergranular fracture at room temperature.
Application of Piezoelectric Materials for Use as Actuators and Sensors in Hard Disk Drive Suspension Assemblies
Authors: Heffelfinger J. R. , Boismier D. A. 
Published: April 2011

AbstractSuspension assemblies, the mechanical arm that supports the read/write head in a Hard Disk Drive (HDD), are incorporating piezoelectric motors for dual-stage actuation. With high displacements and high Curie Temperatures, lead zirconium titanate (PZT) is the preferred piezoelectric material for this application. In this study, commercially available PZT is studied for critical material properties that include strength, aging and particulate generation. An average PZT strength of 111.7 MPa and a Weibull parameter (m) of 12.18 was measured for the material. Aging rates of the dielectric constant vary between 1.9 to 3.2 % per time decade depending on the test condition. The attachment of PZT motors to the suspension assembly provides a method of sensing suspension resonance, shock and temperature fluctuations. Fast Fourier Transform (FFT) analysis of voltage generation of the PZT during drive operation identified a frequency of 6509 Hz that is within 0.2% of the measured resonance frequency of the suspension. The PZT generated several volts for shock events between 500 to 2000 G's of the suspension. Implications of the material parameters and potential sensing capabilities of the PZT are discussed.
Doping Effects in Pb(Mg1/3Nb2/3)O3-PbTiO3 Ceramics for High Power Transduction Applications
Authors: Chen Yun-Han , Hirose Senji , Viehland Dwight , Uchinol Kenji 
Published: April 2011

AbstractPiezoelectric ceramics are potential high-power electro-acoustic sources, and have been studied for many years. However, when these devices are driven under high level vibration, the electromechanical characteristics depart significantly due to the loss and nonlinear behavior in terms of elastic and dielectric properties. In this paper, we present results concerning the development of modified Pb(Mgl/3Nb2/3)O3-PbTiO3 (PMN-PT) ceramics for high-power application. We have focused efforts on base PMN-PT compositions close to the morphotropic phase boundary. Different mono-doping have been studied to understand the doping effects on the properties of PMN-PT ceramics and, moreover, to improve the properties for the high-power application. Of all the substitutents investigated in this study, Mn-doping was found the only one to improve the properties of PMN-PT significantly for high-power application by reducing the total loss (including mechanical loss as well as the dielectric loss), yet keeping the coupling factor constant. This work is supported by Office of Naval Research.
De-Icing Layers of Interdigitated Microelectrodes
Authors: Courville Zoe , Petrenko V.F. 
Published: April 2011

AbstractWe report development of special active coatings that are capable of de-icing various solid surfaces vulnerable to icing such as airplane wings, helicopter blades, road signs, superstructures, hulls of ships, etc. The coating consists of a thin web of metal interdigitated microelectrodes formed using photolithography. The electrodes are made of very thin copper on a thin and flexible Kapton substrate. After etching, the electrodes were electroplated with Au to increase their resistance to electro-corrosion. The de-icing action of the coating is based on the phenomenon of ice electrolysis. Namely, when ice forms over the electrodes, a small DC bias of 5 V to 30V is applied to the electrodes to generate a DC current through the ice. The ice adjacent to the electrodes is then decomposed into gaseous hydrogen (on the cathode) and gaseous oxygen (on the anode) thus eliminating bonding between the ice and the metal. Moreover, gas bubbles rapidly growing on the interface spread as interfacial cracks thus breaking the ice. We present a theory of such active grids and describe their preparation procedure. Results of mechanical and electrical tests will be shown
Dynamics of MEMS Microengines Using Optoelectronic Laser Interferometry
Authors: Brown G. C. , Pryputniewicz R. J. , De Boer M. P. , Smith Norman 
Published: April 2011

AbstractWe have developed an optoelectronic laser interferometry microscope (OLIM) methodology for rapid characterization of MEMS' motion dynamics. In this study, electrostatic comb drive actuated microengines comprised of a 64 μm diameter drive gear and a 300 μm output gear (load gear) were characterized dynamically. Two different input signals were used: 1) a four-step square wave input and 2) an optimized input signal calculated from an analytical model. Out-ofplane motion on rotating microgears was measured as a function of the input signals. The outof-plane motions for the drive during the four-step input ranged from zero to ±462 nm and from zero to ±514 nm for the drive and output gears, respectively. For the optimum input, the out-ofplane motions ranged from zero to ±1030 nm for the drive gear. However, for the output gear the tilt magnitudes were nearly constant at ±514 rum, and were independent of angular position. The more constant out-of-plane motions of the load gear for the optimized signal are due to improved kinematics and kinetics leading to more continuous rather than impulsive forces (e. g., frictional, inertial) acting on the output gear.
Torsional Micromirror Array Design for Optical Binary Switching and Amplitude Modulation Applications
Authors: Kolesar E.S. , Allen P.B. , Boydston N.C. , Howard J.T. , Ko S.Y. , Wilken J.W. 
Published: April 2011

AbstractA torsional micromirror was designed and fabricated using a three-level, polysilicon, surface micromachined, microelectromechanical systems (MEMS) process. The torsional micromirrors have highly-reflective, gold-coated polysilicon optical surfaces. Electrostatically induced in-plane and outof-plane vertical deflections on the order of 2.75 νm were achieved. The modeling phase focused on the microdynamical behavior of the torsional micromirror. The IntelliCAD® finite element analysis program was used to generate a plot of the micromirror's deflection (d) versus applied direct current voltage (V). The data was least-squares fitted to the well-established V μ d3/2 relationship. A resonant frequency analysis predicted an approximate switching speed of 6 νsec. The relative reliability (number of operational cycles) of the torsional micromirror design was measured to exceed 2 million flexure events. The potential for using torsional micromirrors as binary optical switches and amplitude modulators is addressed.
X-ray Microprobe Studies of Materials Problems Related to Microelectromechanical Systems (MEMS) Structures
Authors: Mölders N. , Schilling P.J. , Göttert J. , Moser H.O. , Saile V. 
Published: April 2011

AbstractThe understanding of the physical, chemical and mechanical properties of materials used in micro-electromechanical systems (MEMS) is essential for the successful application. For the characterization of such materials, it is often necessary to utilize a probe which can gather information on the same scale as the devices themselves. Based on these needs, x-ray microprobe analysis has been employed to perform spatially resolved measurements on several problems related to the fabrication of MEMS devices. These include spatially resolved transmission measurements of the homogeneity of transmitted flux through a graphite mask, micro-fluorescence measurements to assess elemental distributions, and micro-XANES measurements to follow the breakdown of new sulfone-based x-ray resists. These studies demonstrate the value of such an instrument in the characterization of micro-systems.
Defining Conditions for the Etching of Silicon in an Inductive Coupled Plasma Reactor
Authors: Ashraf H. , Bhardwaj J. K. , Guibarra E. , Hall S. , Hopkins J. , Hynes A. M. , Johnston I. , Lea L. , Mcauley S. , Nicholls G. , O'Brien P. 
Published: April 2011

AbstractIn high-density fluorinated plasma processes, the mechanisms that fundamentally limit the etching of silicon are poorly understood. In an effort to improve our understanding of limits to the performance of such systems, the etching of silicon wafers in an inductive coupled plasma reactor, using SF6, has been studied. A systematic empirical investigation has allowed us to define many of the experimental parameters that control the etching rate.There is little temperature dependence of etching which suggests a diffusion limited process. Systematic variation of parameters controlling the rate of etching: total pressure in the reactor, flow rate, partial pressure of reactive species and the rf power supplied to the discharge enable us to accurately define the performance of the system. Experiments, which segregate the physical and chemical components of the etching process, support the conclusion that etching is dominated by electrically neutral species. These various results are interpreted in terms of accepted models for the reactive chemistry in plasmas containing SF6.The MEMS industry is placing ever greater demands on etching processes, and there is a need to achieve the high degrees of anisotropy, and critical dimension control, at high etch-rates. The approach outlined allows us to develop effective strategies for evolving improved systems for the high rate plasma etching of silicon.
MOCVD of High-K Dielectrics and Conductive Metal Nitride Thin Films
Authors: Senzaki Yoshihide , Hamilton Richard F. , Reid Kimberly G. , Hobbs Christopher C. , Hegdec Rama I. , Tinerc Mike J. 
Published: April 2011

AbstractA known liquid mixture of [(CH3CH2)2N]3 Ta=NCH2CH3 and [(CH3CH2)2N]3Ta[ð2-CH3CH2N=CH(CH3)] was studied to deposit Ta2O5 and TaN thin films by CVD. Films were deposited at temperatures below 400°C using oxygen for oxide and ammonia for nitride, respectively. XRD analysis revealed that as-deposited amorphous tantalum oxide films were converted to hexagonal Ta2O5 after annealing under oxygen, while tantalum nitride thin films contained cubic TaN as deposited. The low viscosity, thermal stability, and sufficient volatility of the precursor allows direct liquid injection to deliver the precursor, which results in high deposition rate and uniformity of the deposited films.
Epitaxial Growth of Sr0.3Ba0.7Nb2O6 Thin Films Prepared by Sol-Gel Process
Authors: Nishio Keishi , Thongrueng Jirawat , Watanabe Yuichi , Tsuchiya Toshio 
Published: April 2011

AbstructWe succeeded in the preparation of strontium-barium niobate (Sr0.3Ba0.7Nb2O6 : SBN30)that have a tetragonal tungsten bronze type structure thin films on SrTiO3 (100), STO, or La doped SrTiO3 (100), LSTO, single crystal substrates by a spin coating process. LSTO substrate can be used for electrode. A homogeneous coating solution was prepared with Sr and Ba acetates and Nb(OEt)5 as raw materials, and acetic acid and diethylene glycol monomethyl ether as solvents. The coating thin films were sintered at temperature from 700 to 1000°C for 10 min in air. It was confirmed that the thin films on STO substrate sintered above 700°C were in the epitaxial growth because the 16 diffraction spots were observed on the pole figure using (121) reflection. The <130> and <310> direction of the thin film on STO were oriented with the c-axis in parallel to the substrate surface. However, the diffraction spots of thin film on LSTO substrate sintered at 700°C were corresponds to the expected pattern for (110).
Near-Stoichiometric Barium Titanate Synthesis by Low Temperature Hydrothermal Reaction
Authors: Woo Kyoungja , Choi Guang J. , Cho Young S. 
Published: April 2011

AbstractBarium-deficiency of barium titanate particles prepared by low temperature hydrothermal reaction has been notorious. It has been believed that barium-deficiency is caused by the high solubility of barium source compared with titanium. Here is reported the synthesis of nearstoichiometric barium titanate powders with ultrafine particle size and high crystallinity by low temperature hydrothermal reaction from barium acetate and titanium tetra(methoxyethoxide). Barium titanate particles were synthesized in the spherical, metastable cubic crystalline grains with size distribution between 60 ∼ 90 nm in diameter. Ultrafine particle size was resulted from the control of the hydration rate and the decrease of Ti-O-Ti cross-linking extent of titanium precursor. Increasing barium to titanium molar ratio in reactant could not overcome the notorious barium-deficiency but, improved stoichiometry and produced finer and less agglomerated particles. Interestingly, adding a slight pressure to autogeneous one to make total 4 ∼ 10 atm has yielded near-stoichiometric, highly crystalline, and less agglomerated barium titanate particles. It seems like that the total pressure around 4 ∼ 10 atm provides strong force enough to push barium ions into the interstitial points of perovskite structure and stabilize it. These particles, which were in metastable cubic form as synthesized, initiated phasetransition to tetragonal form by calcination at 400 °C.
Study on ZrO2 Deposited Directly on Si as an Alternative Gate Dielectric Material
Authors: Qi Wen-Jie , Nieh Renee , Lee Byoung Hun , Jeon Youngjoo , Kang Laegu , Onishi Katsunori , Lee Jack C. 
Published: April 2011

AbstractReactive-magnetron-sputtered ZrO2 thin film has been deposited on Si directly for gate dielectric application. Both structural and electrical properties of the ZrO2 film have been investigated. An amorphous structure for 30Å ZrO2 and a semi-amorphous structure for 200Å ZrO2 have been revealed. The sputtered film shows a good stoichiometry and a good structural stability of ZrO2 based on the X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy data. Thin equivalent oxide thickness of about 11.5Å was obtained without the consideration of quantum mechanical effects. A low leakage of less than 10−2 A/cm2 at ±1V relative to the flat band voltage was obtained for this 11.5Å equivalent oxide thickness Pt/ZrO2/Si structure. High effective dielectric breakdown and superior reliability properties have been demonstrated for ZrO2 gate dielectric.
A Study on Hysteresis Effect of Barium Strontium Titanate Thin Films for Alternative Gate Dielectric Application
Authors: Qi Wen-Jie , Zawadzki Keith , Nieh Renee , Jeon Yongjoo , Lee Byoung Hun , Lucas Aaron , Kang Laegu , Lee Jian-Hung , Lee Jack C. 
Published: April 2011

AbstractHysteresis effect of barium strontium titanate (BST) thin films for gate dielectric application has been studied. It is found that the “counterclockwise” hysteresis has strong sweep voltage and operating temperature dependence. It can be reduced or eliminated by proper thermal annealing or by using a barrier layer. A charge trapping and detrapping mechanism has been proposed.
Growth of MgO by Metal-Organic Molecular Beam Epitaxy
Authors: Niu Feng , Hoerman Brent.H. , Wessels Bruce.W. 
Published: April 2011

AbstractMgO thin films were deposited on (100) Si substrates by metal-organic molecular beam epitaxy (MOMBE). Magnesium acetylacetonate was used as the precursor and an oxygen RF plasma was used as the oxidant. The films were characterized by a combination of transmission electron microscopy, Auger spectrometry and atomic force microscopy. Analyses indicate that the films directly deposited on Si substrates are stoichiometric, phase-pure, polycrystalline MgO with a [100] texture. Carbon contamination of the films resulting from precursor decomposition was not observed within detection limits. Furthermore, the growth rate of MgO has been systematically investigated as a function of growth temperature.
Thermal Annealing Recovery of Intersubband Transition in Proton-Irradiated GaAs/Al0.3Ga0.7As Multiple Quantum Wells
Authors: Gingrich H.S. , Morath C. , Manasreh M.O. , Ballet P. , Smathers J.B. , Salamo G. J. , Jagadish C. 
Published: April 2011

AbstractOptical absorption spectra of intersubband transitions in heavily proton irradiated n-type GaAs/AlGaAs multiple quantum wells were studied as a function of isochronal and isothermal annealing. The absorption spectra of intersubband transitions were depleted in samples irradiated with 1MeV proton doses higher than 1.0 × 1014 cm−2. Thermal annealing of the irradiated samples show that the intersubband transitions are recovered. The relatively lower annealing temperatures at which the recovery is observed indicate that the irradiation-induced defects that trapped the two-dimensional electron gas in the quantum wells are vacancy and interstitial related defects. Once these traps are thermally annealed the electrons are released back to the quantum wells, resulting in the recovery of the intersubband transitions.
2.3–2.7µm InGaAsSb/AlGaAsSb Broad-Contact and Single-Mode Ridge-Waveguide SCH-QW Diode Lasers Operating in CW Regime at Room Temperature
Authors: Garbuzov D. , Lee H. 
Published: April 2011

AbstractA new approach in the design of (Al)InGaAsSb/GaSb quantum well separate confinement heterostructure (QW-SCH) diode lasers has led to CW room-temperature lasing up to 2.7 gm. To avoid QW material degradation associated with the miscibility gap in the 2.3–2.7 tim wavelength range, we used highly strained, “quasi-ternary” InxGa1−xSbl−yAsy compounds with 0.25<x<0.38 and y<0.07 as the material for QWs. Very low threshold current density (∼300 A/cm2) and high CW output powers (>100 mW) were obtained from broad contact devices operating in the 2.3–2.6 μm wavelength range. From the spontaneous emission measurements we have identified that the Auger process determines the rate of recombination in quantum well active region over the entire temperature range studied (15– 110 'C) for 2.6 gim lasers and only at temperatures higher than 65 'C for 2.3 pim lasers. If Auger recombination dominates, strong temperature dependence of Auger coefficient leads to the rapid increase of threshold current density with temperature (To ∼40 °C). In the range of 15 – 65 °C for 2.3 gim devicesa monomolecular, non-radiative mechanism dominates and To is about 110 °C. In addition, single-mode CW room temperature ridge-waveguide lasers with wavelength of 2.3-2.55 gim have been fabricated for the first time. The lasers display threshold currents around 50 mA with CW output powers of several milliwatts. Since for a certain range of temperatures and currents one of the longitudinal modes dominates in the spectra of the ridge lasers they have been successfully applied forgas spectroscopy.
Refractive Index Measurements and New Sellmeir Coefficients of Zinc Germanium Phosphide From 2-9 Microns With Implications for Phase Matching in Optical Parametric Oscillators
Authors: Zelmon David E. , Hanning Elizabeth A. , Schunemann Peter 
Published: April 2011

AbstractRecent experiments in mid IR frequency conversion have revealed that older Sellmeir models for zinc germanium phosphide are inadequate. Erroneous predictions in phase matching angles based on older refractive index data have resulted in compromised device performance. We have conducted a complete study of the refractive indices of zinc germanium phosphide from 2 to 9 microns and calculated new Sellmeir coefficients. We have used these to explain the results of recent experiments with mid IR optical parametric oscillators. The phase matching calculations based on our new refractive index data predict much more closely the results of several different mid IR frequency conversion experiments.