bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Transformations Induced by Arsenic Implants into Silicon
Authors: Lavine James P. , Tuschel David D. , Black Donald L. 
Published: April 2011

AbstractMicro-Raman spectroscopic investigations of arsenic-implanted silicon show lines characteristic of silicon crystallites even at implant doses above the amorphization threshold. The intensity and frequency of occurrence of the lines increase with the implanted dose. Polarization/orientation Raman studies indicate the crystallites are silicon in the hexagonal phase (Si-IV) and silicon in the diamond phase (Si-I). The latter are oriented differently than the substrate silicon. Monte Carlo simulations of the arsenic ion energy loss and published molecular dynamics studies suggest that each arsenic ion deposits sufficient energy to locally melt the silicon lattice. This is taken as the basis of the present attempt to explain the origin of the crystallites. A one-dimensional numerical model is developed to determine the time scale for the liquid silicon to solidify. The effect of amorphous silicon on the solidification is also investigated.
Three Dimensional Thermal Effects in MEMS Devices
Authors: Keuren Edward Van , Currie John , Nelson Matthew , Paranjape Makarand , Schneider Thomas , Smith Ryan , Treado Pat , Ward John , White Robert 
Published: April 2011

AbstractA three dimensional thermal imaging system is being developed for measuring temperature profiles in MEMS-biomedical devices. These devices rely on a thermal microablation of the dead-skin layer in order to sample transdermal fluids. This is accomplished using microheaters embedded into a PDMS microchannel device. In order to determine the proper functioning as well as long-term safety of the devices, a temperature profile of the device and the skin in contact with the heaters is needed. The results of simple analytical models are used to optimize a proto- type device. Using a three-dimensional chemical imaging microscope and temperature-depend- ent fluorophores, the temperature profile in a sample can be determined quantitatively as well. We demonstrate the technique on a model sample, and discuss extension to other applications such as thermal imaging in biological systems.
Piezoelectric Shear Mode Inkjet Actuator
Authors: Brünahl Jürgen , Grishin Alex M. , Khartsev Sergey I. , Österberg Carl 
Published: April 2011

AbstractWe report on comprehensive characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O3 (PZT) ceramics. The paper starts with an overview of different inkjet technologies such as continuous jet and drop-on-demand systems, whereat main attention is turned on piezoelectric systems particularly Xaar-type shear mode inkjet color printheads. They are an example of complex microelectromechanical systems (MEMS) and comprise a ferroelectric array of 128 active ink channels (75νm wide and 360νm deep). Detailed information about manufacturing and principles of operation are given. Several techniques to control manufacturing processes and to characterize properties of the piezoelectric material are described: dielectric spectroscopy to measure dielectric permittivity ε and loss tanσ; ferroelectric hysteresis P-E loop tracing to get remnant polarization Pr and coercive field Ec, and a novel pulsed technique to quantify functional properties of the PZT actuator such as acoustic resonant frequencies and electromechanical coupling factor. Stroboscope technique has been employed to find correlation between the degradation of ink-jet performance and heat/high voltage treatment resulting in ferroelectric fatigue.
The Fabrication of Stainless Steel Parts for MEMs
Authors: Garino Terry J. , Morales Alfredo , Buchheit Thomas , Boyce Brad 
Published: April 2011

AbstractA micro-molding process was used to fabricate parts in the 0.1 to 10 mm size range from a stainless steel nano-powder. The two types of molds used were both produced from parts fabricated using the LIGA process so that they had precise dimensional tolerance and straight sidewalls. Rigid PMMA molds were made by injection molding and flexible silicone rubber molds were made by casting. Mold filling was accomplished by mixing the powder with epoxy to form a putty-like material that was then pressed into the mold cavities and allowed to cure. After pyrolysis of the epoxy, the parts were sintered in forming gas. The densification kinetics were measured in situ using a video system. Full densification was achieved after 1 hour at 1350°. The microstructure of the sintered parts was examined using the SEM. The mechanical strength, hardness, dimensional tolerance and surface roughness of the sintered parts were also measured.
Thermal Losses and Temperature Measurement in SOI MEMS Heater
Authors: Moelders Nicholas , Puscasu Irina , McNeal Mark P. , Pralle Martin U. , Last Lisa , Ho William , Greenwald Anton C. , Daly James T. , Johnson Edward A. , George Thomas , Choi Daniel S. 
Published: April 2011

AbstractA sensor chip has been designed and tested that uses a MEMS strip heater as both source and detector of infrared radiation. An optical cavity reflects infrared radiation back onto the source filament. Changes in reflected light intensity modify heater temperature, and the measured signal is a change in resistance. The effects of processing on electrical and thermal isolation were characterized and used to evaluate device performance. Thermally isolated, uniformly heated emitters are achieved using a backside release etch process. The fully released devices demonstrated superior electric to thermal-optical conversion, with the requisite narrow band emission for CO2 detection. Using these sensor-chips, CO2 detection was demonstrated, with projected sensitivities ≤0.1%.
Potential Electric Power Applications for Magnesium Diboride
Authors: Grant Paul M. 
Published: April 2011

ABSTRACTThe newly discovered superconductor, MgB2, has significant potential for a number of electric power applications, even though its critical temperature, TC, is “only” 39 K. In recent months, there has been rapid improvement in its critical state parameters, JC and H*, properties crucial to deployment in power devices, which now rival NbTi at 4.2 K, and equal or surpass many of the high temperature superconducting copper oxide perovskites in the 20 – 25 K range. Moreover, substantial progress has been achieved in realizing wire embodiments that appear economically scalable to commercial production. In this paper, we will review several opportunities to exploit these developments for transformer and electric cable applications, and hint at the possibility of a novel and visionary power delivery system centered on an MgB2-based dc cable cooled by gaseous or liquid hydrogen supplying both electrical and chemical energy to the end user.
Crystal Growth and Superconducting Properties of Bi2Sr2Ca2Cu3Oy (Bi2223) Single Crystals
Authors: Shimizu K. , Okabe T. , Horii S. , Otzschi K. , Shimoyama J. , Kishio K. 
Published: April 2011

ABSTRACTBi2223 single crystals were grown by the floating zone method with an extremely slow growth rate of 0.05 mm / h. The largest size of the plate-like single crystal was approximately 3 × 2 × 0.1 mm3. The X-ray diffraction analysis and DC susceptibility measurements revealed that the grown crystals were almost single phase of Bi2223 with a very small percentage of Bi2212 intergrowth. Then carrier doping was systematically controlled in a wide range from underdoping to overdoping by post annealing under various conditions. Tc of the crystals was found to vary from 98 K (underdoped) to 108 K (overdoped) with Tc = 110 K for optimally-doped. In the optimally-doped phase the electromagnetic anisotropy factor, γ2 of Bi2223 was smaller than that of Bi2212. Abrupt resistivity drop was observed under fields below the second peak field of the magnetization hysteresis loops, suggesting a first order phase transition of the flux line lattice. Magnetic phase diagram of Bi2223 single crystals for H // c was found to be similar to that of Bi2212.
Observation of Vortices and Columnar Defects by 1-MV Lorentz Microscopy I
Authors: Kasai H. , Kamimura O. , Matsuda T. , Harada K. , Tonomura A. , Okayasu S. , Sasase M. , Nakayama Y. , Shimoyama J. , Kishio K. , Hanaguri T. , Kitazawa K. 
Published: April 2011

ABSTRACTA single crystalline Bi2Sr2CaCu2O8+8 which has columnar defects in its inside are observed by Lorentz microscopy using the newly developed 1-MV field emission electron microscope at the first time. The superconducting vortices are observed with higher contrast than ever. Simultaneous observation of vortices and columnar defect is succeeded in real time.
Thermoelectric Properties of Bi1-xSbx Nanowire Arrays
Authors: Lin Yu-Ming , Cronin Stephen B. , Rabin Oded , Ying Jackie Y. , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTWe present here a thermoelectric transport property study of Bi1−xSbx alloy nanowires embedded in a dielectric matrix. Temperature-dependent resistance measurements exhibit nonmonotonic trends as the antimony mole fraction (x) increases, and a theoretical model is presented to explain the features that are related to the unusual band structure of Bi1−xSbx systems. Seebeck coefficient measurements are performed on nanowires with different diameters and compositions, showing enhanced thermopower over bulk Bi. The magneto-Seebeck coefficient of these nanowires also exhibits an unusual field dependence that is absent in bulk samples.
Thin Film Dispenser Cathodes for Thermionic Micro-Devices
Authors: Zavadil Kevin R. , King Donald B. 
Published: April 2011

ABSTRACTElectron emissive thin films that possess the thermionic properties of macroscale dispenser cathodes have been fabricated using standard RF sputter deposition techniques. These films are based on a compositionally modulated structure using W and a Ba-containing ternary oxide. These films exhibit uniform work function values of 1.9 to 2.2 eV with high emission coefficients of 2 to 26 A·cm−2K−2. Electron microscopy shows that W layer coalescence and continued particle growth occurs with prolonged annealing, eventually disrupting the original surface layer. Chemical modification of the oxide during deposition may provide a route to limit the extent of W coalescence and preserve surface metallization layers on these films. These films are designed to be integrated into thermionic micro-devices.
Electronic Structure of K2Bi8Se13
Authors: Bilc Daniel I , Larson Paul , Mahanti S.D. , Kanatzidis M.G. 
Published: April 2011

ABSTRACTK2Bi8 Se13 belongs to a class of complex Bi-Te-Se systems which show great potential for thermoelectric performance. This compound forms in two distinct phases α-K2Bi8 Se13 (triclinic with space group P-1) and β-K2Bi8 Se13 (monoclinic with space group P 21/m). In the β-phase, there is substantial disorder at four sites in the unit cell, occupied by two K and two Bi atoms. To understand the electronic properties of these two different phases we have carried out band structure calculations within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spin-orbit interaction (SOI) was incorporated using a second variational procedure. The α. phase is found to be a semiconductor with an indirect band gap of 0.47eV. For the β-phase we have chosen two different ordered structures. The system is a semi-metal for one of the structures whereas for the other, it is a narrow gap semiconductor with a gap of 0.38eV in the absence of SOI, but the gap collapses and the system becomes a semimetal with low density of states at the Fermi energy when SOI is included.
Conservation of Lateral Momentum in Heterostructure Integrated Thermionic Coolers
Authors: Vashaee Daryoosh , Shakouri Ali 
Published: April 2011

ABSTRACTThin film thermionic coolers use selective emission of hot electrons over a heterostructure barrier layer from emitter to collector resulting in evaporative cooling. In this paper a detailed theory of electron transport perpendicular to the multilayer superlattice structures is presented. Using Fermi-Dirac statistics, density-of-states for a finite quantum well and the quantum mechanical reflection coefficient, the currentvoltage characteristics and the cooling power density are calculated. The resulting equations are valid in a wide range of temperatures and electric fields. It is shown that conservation of lateral momentum plays an important role in the device characteristics. If the lateral momentum of the hot electrons is conserved in the thermionic emission process, only carriers with sufficiently large kinetic energy perpendicular to the barrier can pass over it and cool the emitter junction. However, if there is no conservation of lateral momentum, the number of electrons participating in thermionic emission will dramatically increase. The theoretical calculations are compared with the experimental dark current characteristics of quantum well infrared photodetectors and good agreement over a wide temperature range is obtained. Calculations for InGaAs/InGaAsP superlattice structures show that the effective thermoelectric power factor (electrical conductivity times the square of the effective Seebeck coefficient) can be improved comparing to that of bulk material. We will also discuss methods by which the conservation of lateral momentum in thermionic emission process can be altered such as by creating a controlled roughness at the interface of the superlattice barriers. The improvement in the effective power factor through thermionic emission can be combined with the other methods to reduce the phonon thermal conductivity in superlattices and thus obtain higher thermoelectric figure-of-merit ZT.
High Temperature Electrical Transport Properties of Eu and Yb-doped Skutterudites
Authors: Tedstrom R. H. , Lamberton G. A. , Tritt Terry M. , Nolas G. S. 
Published: April 2011

ABSTRACTSkutterudites are a class of materials that show promise for thermoelectric applications due to their high power factor and the ability to “tune” the thermal conductivity due to the addition of “rattling” atoms into the novel structure of these materials. Thermopower and resistivity is measured and reported for a series of Eu and Yb-doped skutterudites over a temperature range of approximately 100 K – 700 K using the High Temperature Thermoelectric Probe. Sample measurement techniques are briefly discussed. Data from various dopings is presented and compared in hope of showing trends that point towards improvements in these skutterudites.
Spectroscopic Ellipsometry as a Potential In-Line Optical Metrology Tool For Relative Porosity Measurements of Low- K Dielectric Films
Authors: Edwards N.V. , Vella J. , Xie Q. , Zollner S. , Werho D. , Adhihetty I. , Liu R. , Tiwald T.E. , Russell C. , Vires J. , Junker K.H. 
Published: April 2011

AbstractThe optical properties of organosilicate glass (OSG) samples were investigated with spectroscopic ellipsometry. We found that samples with dramatically higher hardness had higher indices of refraction (RI) and thus higher electron densities and lower relative porosities than films with lower hardnesses. The reverse was true for films with low hardnesses. As well, these films did not have the same optical properties as porous SiO2 across the spectral range measured, which we show has significant implications for the in-line optical metrology of these materials.
In-situ monitoring of nucleation stage during aluminum-CVD for nano-structure control
Authors: Iino T. , Sugiyama M. , Shimogaki Y. 
Published: April 2011

AbstractInitial nucleation of Al in chemical vapor deposition (CVD) using dimethyl-aluminum- hydride was observed in order to obtain a principle for enhancing the nucleation density. The analysis employed in situ surface reflectivity measurement combined with X-ray photoelectron spectroscopy and scanning electron microscopy at the typical stage of reflectivity behavior. During the incubation period between the injection of DMAH and the nucleation of Al, a constant amount of Al existed on the surface while no nuclei was observed. The precursor of the nuclei seemed not DMAH itself but the reaction product of the adsorbed DMAH. The activation energy for reciprocal of the incubation period, which may be an index of the reaction rate of the adsorbed layer, is slightly larger than for the continuous growth of Al.
Sputter-Deposited Bcc Tantalum on Steel with the Interfacial Tantalum Nitride Layer
Authors: Patel Anamika , Gladczuk Leszek , Paur Charanjeet Singh , Sosnowski Marek 
Published: April 2011

AbstractTantalum has mainly two phases: alpha phase (bcc structure) and beta phase (tetragonal structure). The meta-stable beta phase is usually obtained in sputtered films. Alpha phase is preferred over the beta for some applications as beta phase is very brittle. One of such application is to protect steel from the erosive and the corrosive wear. It was found that with the intermediate layer of tantalum nitride the preferred alpha phase was grown on steel by DC magnetron sputtering technique. Electrical and structural properties of these films were studied by four-point probe measurement and x-ray diffraction (XRD). Stoichiometry of the interfacial tantalum nitride layer was investigated by nuclear reaction analysis (NRA). Influence of the interfacial film thickness and the ratio of argon and nitrogen gas during reactive deposition of tantalum nitride on the tantalum phase were investigated. This work also reports on the dependence of tantalum phase on the substrate temperature (100-400°C) during sputtering in Ar and Kr gases.
Thermal-Mechanical Effects of Ceramic Thermal Barrier Coatings on Diesel Engine Piston
Authors: Muchai Jesse G. , Kelkar Ajit D. , Klett David E. , Sankar Jagannathan 
Published: April 2011

AbstractThe purpose of this paper is to investigate the piston temperature and stress distribution resulting from varying coating thicknesses of Partially Stabilized Zirconia (PSZ) thermal barrier coatings for the performance in diesel engine applications. This analysis is based on the premise that coating thickness affects the heat transfer and temperature distribution in the piston. A gas dynamic engine cycle simulation code was used to obtain thermal boundary conditions on the piston then, a 2-D axisymmetric Finite Element Analysis (FEA) using ANSYS was performed to evaluate the temperature and stress distributions in the piston as a function of coating thickness. Coating thicknesses studied include 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, and 2.0mm. The results indicate increased piston surface temperature with increasing coating thickness. The maximum stress on the coated piston surface was high while the substrate stress was less than the coating yield stress for all coating thicknesses. Further, the analysis showed that the interface stress at all coated conditions is low enough such that no separation of the coating is expected. The FEA results suggest an optimum coating thickness of 0.1 to 1.5 mm for diesel engine application to avoid unduly high stress in the ceramic.
Thermoelectric Properties of B12+xC3-x Thin Films Prepared by Pulsed Ion-Beam Evaporation
Authors: Suematsu Hisayuki , Kitajima Kazuo , Ruiz Ichiro , Suzuki Tetsuo , Jiang Weihua , Yatsui Kiyoshi , Kobayashi Katsuaki , Takeda Masatoshi 
Published: April 2011

AbstractThin films of boron carbide (B12+xC3-x) were prepared on glass substrates by a pulsed ion-beam evaporation method. A pulsed proton beam with an energy of 1 MV (peak) and a current of 60 kA was focused on sintered B12+xC3-x targets. Ablation plasma was formed from the irradiated targets and thin films were prepared on Pyrex and SiO2 glass substrates at room temperature. From results of X-ray diffraction, the thin films consisted of a B12+xC3-x phase. Using a known relationship between the composition and the lattice parameters, the composition of B12+x1C3-x thin films was estimated to be x = 0.3 and 1.0, which were close to the nominal composition of the targets. These results indicate that B12+x1C3-x with different carbon contents has been successfully prepared by IBE without substrate heating or sample annealing. Thermoelectric properties of the thin films were measured. A B12+x1C3-x thin film with estimated composition of x =0.9 exhibited the highest power factor at room temperature among the B12+x1C3-x samples reported.
A Versatile Approach for Biomaterial Patterning: Masked Ion Beam Lithography
Authors: Gonsalves Kenneth E. , He Wei , Poker David B. , Batina Nikola , Merhari Lhadi 
Published: April 2011

AbstractWe describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (methyl methacrylate) (PMMA) film was used as a model system and subjected to Ca+ and P+ ion implantations through masks. Ca+ ion implantation was performed at an energy of 85 keV with a fluence of 1×1014 ions/cm2. P+ ion implantation was done at an energy of 85 keV with fluences of 1×1015 and 1×1016 ions/cm2. Arrays of holes were generated during these processes. AFM showed that the depth of the holes is in the nanoscale region. The surface hydrophobicity of the exposed PMMA films was investigated by contact angle measurement. The results indicated that ion implantation changed the surface hydrophobicity.
Stable Adsorption of Lipid Vesicles on Modified Gold Surfaces
Authors: Sofou Stavroula , Thomas James L. 
Published: April 2011

AbstractThe use of vesicles as amplifiers in biosensors is receiving increasing attention. Because vesicles may entrap thousands of reporter molecules, strong signal amplification can be obtained if a small number of analytes can simply release the entrapped reporters. Surface immobilization of vesicles with sensitivities for different analytes could then provide for simultaneous amplified detection of a number of analytes on a single chip. To achieve this goal, vesicles must first be stably adsorbed to a surface, without rupture. We have varied vesicle composition and charge (phosphatidylcholine, phosphatidylcholine-phosphatidic acid at 4.6 molar ratio) and solution ionic strength, to study the adsorption of fluorescent vesicles to glass, gold, and gold modified with chemisorbed acetylcysteine. Surfaces were characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS), and vesicle integrity and behavior was studied using entrapped and lipophilic fluorescent markers either together or in separate experiments. Diffusion coefficients (by photobleaching recovery) and vesicle fusion (by energy transfer) were monitored using confocal fluorescence microscopy. Finally, as a “proof of principle”, release of a self-quenching entrapped reporter dye (calcein) by the detergent Triton X-100 was followed in real time.
Effect of Al Concentration on Growth of Antiphase Domains in Ti3Al
Authors: Koizumi Y. , Katsumura H. , Minamino Y. , Tsuji N. 
Published: April 2011

AbstractEffects of Al-concentration on growth of antiphase domains (APDs) in Ti3Al crystals have been investigated using crystals with stoichiometric (Ti-25at.%Al) and Al-rich (Ti-33at.%Al) compositions in the temperature range from 973K to 1173K. The growth rate of APDs in the Al-rich crystal is several times higher than that in the stoichiometric crystals at all the temperatures investigated. While the time dependence of APD size obeys the parabolic-growth-law in the stoichiometric crystal, negative deviations from the law takes place at the late stage of the APD growth in the Al-rich crystal owing to the pinning effect of low-energy APB boundaries. APD boundaries lying on prism planes are formed in the Al-rich crystal annealed at 973K.