bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid-Solidified Metallic Actuator Materials Developed by Electromagnetic Nozzleless Melt Spinning Method
Authors: Furuya Y. 
Published: April 2011

AbstractElectro-magnetic nozzleless melt-spinning method was developed by combining the control of the flow down of the molten metals after electromagnetic float-melting(i.e. levitation) with rapid solidification by rotating roll. The metallurgical grain microstructures can be changed by rotating roll speed. It was confinned that the produced, intermetallic TiNi and NiAl system alloy thin plates showed the strong crystal anisotropy, higher shape memory functional properties than those of the conventionally processed melt-worked samples having its same origin. As new SMAs by using this method, ferromagnetic shape memory, FePd alloy having very large magnetostriction and super high temperature shape memory, RuTa alloy having the transformation over 1000°C were developed. Moreover, our recent study on the advanced rapid-solidification machine to produce many kinds of short fibers as well as ribbons is introduced. Finally, harmonic material design for sensor/actuator stacking composite system, namely “Smart Board” for aircraft structures will be introduced.
Zero Hysteresis in Shape-Memory TI-NI-X Films (X = CU, PD) Under Constraint
Authors: Winzek B. , Quandt E. 
Published: April 2011

AbstractThe hysteresis of thin film shape memory actuators affects the frequency of actuators switching between martensite and austenite. Therefore the hysteresis properties of thin films of TiNi, Ti(Ni,Cu) and Ti(NiPd) deposited onto metallic substrates by DC-Magnetron sputtering have been investigated. The substrates have different expansion coefficients to establish biaxial tensile and compressive film stresses, respectively. The results show, that the hysteresis width is significantly affected by the stress state of the shape memory film and in principal depends on the temperature range of measurement. In contrast, the difference Af-Mf remains unchanged. In some alloys zero hysteresis width could be obtained.
Adaptive Composites with Embedded Shape Memory Alloy Wires
Authors: Balta J.A. , Parlinska M. , Michaud V. , Gotthardt R. , Manson J-A.E. 
Published: April 2011

AbstractPre-strained martensitic Shape Memory Alloy wires embeddedz into a composite material act against the stiffness of the host material if they are heated above their retransformation temperature, biasing their strain recovery. As a result, recovery stresses are generated in the composite, leading to a shift in resonance vibration frequency if the wires are placed along the neutral axis of a composite beam. Guidelines for quantification of the effects produced, as a function of SMA wire composition, volume fraction, level of pre-strain, and of host material stiffness are not available yet. In order to investigate the governing mechanisms of activation, adaptive composite materials based on Kevlar fiber reinforced epoxy matrices have been produced by embedding thin Shape Memory Alloy wires, 150 microns in diameter, during processing in an autoclave. A mold was specially designed to pre-strain the SMA wires and prevent their recovery during the cure cycle. Values of the degree of activation in the composite materials, in terms of maximal recovery force and of the corresponding maximal resonance vibration frequency shift will be presented as a function of the stiffness of the host material and SMA volume fraction. Preliminary guidelines for the optimization of these materials will thus be given.
Radial Bragg Grating Package for Temperature Compensation in Interferometric Hydrophone Arrays
Authors: Carreiro L.G. , Ames G.H. , Ramotowski T.S. , Curry P.D. 
Published: April 2011

AbstractA new method of packaging fiber Bragg gratings to stabilize their wavelength over temperature variations was developed using a grating mount fabricated from zirconium tungstate (ZrW2O8), a ceramic with a negative coefficient of thermal expansion (CTE). The principle of operation is based on the differences in CTE of the Bragg grating and grating mount, with the mount serving as a compensator for the thermo-optic effects of the fiber. As the temperature is elevated, the refractive index of the grating increases, shifting the reflection wavelength to longer wavelength. At the same time the ceramic grating mount contracts relieving some of the tension on the grating, causing a shift to shorter wavelength. Since these two effects offset each other, the thermal wavelength shift of the grating can be minimized or even eliminated. In addition to a description of the temperature-compensating device, the properties of zirconium tungstate are briefly discussed with emphasis on the processing of the ceramic grating mount. Thermal analysis data is given for zirconium tungstate with 5% polymer binder addition.
PbZr0.52Ti0.48O3 Ferroelectric Thin Films on Silicon by KrF Excimer Laser Ablation
Authors: Ebihara K. , Mitsugi F. , Yamazato M. , Ikegami T. , Narayan J. 
Published: April 2011

AbstractThe Au / PbZrxTi1-xO3 (PZT) ferroelectrics / YBa2Cu3O7-x (YBCO) superconductor / yttria-stabilized zirconia (YSZ) heterostructures were prepared on Si (100) substrate by KrF excimer laser ablation technique. The x-ray diffraction patterns showed that the PZT films prepared on YBCO / YSZ /Si at 550°C, O2 100 mTorr and a laser energy density of 2 J/cm2(5Hz) are pure perovskite and highly oriented with the (00l) orientation. The polarization (P)-electric field (E) characteristics showed the remanent polarization Pr of 23 µC/cm2 and coercive field Ec, of 35 kV/cm. Pr of the PZT capacitor degraded to one half of initial value after about 1010 switching cycles (50 kHz).
Electrical Conductivity of Piezoelectric Strontium Bismuth Titanate Under Controlled Oxygen Partial Pressure
Authors: Voisard C. , Martin P. Duran , Damjanovic D. , Settier N. 
Published: April 2011

AbstractHysteresis free and linear piezoelectric behavior of SrBi4Ti4O15 (SrBIT) is very promising for precise sensors/actuators devices. Despite a quite low longitudinal piezoelectric coefficient (around 15 pC/N), its elevated ferroelectric phase transition temperature (540°C) allows its use above 300°C. Electrical conductivity at such temperatures should be kept as low as possible in order to avoid loss of piezoelectric properties or charge drifts. Under reducing conditions, however, the electrical conductivity may change considerably. The electrical conductivity of SrBi4Ti4O15 (SrBIT) has been measured under controlled oxygen partial pressure at elevated temperatures (700-900°C) from 1 atm down to 10−15atm. From 1 atm down to 10−15 atm pO2, above 700°C, the conductivity of SrBIT exhibits a -1/4 slope in log-log scale indicating n-type conductivity and an impurity controlled oxygen vacancy concentration. A conductivity minimum is observed around 0.2 atm for undoped SrBIT at 800°C. Acceptor doping (Mn) raises the minimum and flattens the conductivity curve with slope around -1/10 at 700°C, and -1/6 at 900°C. Ionic conductivity and defect ionization are discussed to account for this. Preliminary results indicate the possibility of a large, pO2 independent, region, down to 10−15atm pO2. The ionic transport number was found to be 0.42 at 800°C for undoped SrBIT and 0.75 for Mn doped SrBIT. The activation energies of undoped (1.35 eV) and Mn doped (1.44 eV) samples are close to each other as expected for a common mechanism
Triboluminescence of Rare-Earth-Doped Aluminosilicates and Its Application to Sensing of Structural Damage
Authors: Tanaka Katsuhisa , Ishihara Tsuguo , Fujita Koji , Hirao Kazuyuki 
Published: April 2011

AbstractIntense triboluminescence has been observed in rare-earth-doped aluminosilicates such as BaAl2Si2O8and SrAl2Si2O8doped with Eu2+, Tb3+, or Dy3+. The triboluminescence is caused by the excitation of and emission from rare-earth ions doped in the crystals. A discrepancy in the wavelength of maximum emission intensity between triboluminescence and photoluminescence spectra is observed for the 4f65d-4f7 transition of Eu2+, whereas the peak positions and the relative intensities of emission lines in triboluminescence and photoluminescence spectra are almost the same as each other for the 4f-4f transitions of Th3+ and Dy3+. This is because the 5d levels, which are more significantly affected by ligand fields than the 4f levels, contribute to the transition of Eu2+. It is thought that the difference in local environment around the Eu2+ between on the fractured surface and within the bulk brings about the discrepancy between triboluminescence and photoluminescence spectra
Composite Piezoelectric Materials for Health Monitoring of Composite Structures
Authors: Blanas P. , Das-Gupta K. 
Published: April 2011

AbstractComposites of ferroelectric ceramic in polymer matrix have been developed and characterized for their ability to be employed as embedded sensors for the health monitoring of olymer composite structures. In this paper results illustrating the response of embedded composite sensors to dynamic loads are presented and discussed. Furthermore, the ability of the composite sensors to act as actuators, generating diagnostic waves in composite structures, has been investigated.
Fatigue Testing Machine of Micro-Sized Specimens for MEMS Applications
Authors: Higo Y. , Takashima K. , Shimojo M. , Sugiura S. , Pfister B. , Swain M. V. 
Published: April 2011

AbstractA new type of fatigue testing machine for micro-sized specimens for MEMS applications has been developed. This fatigue testing machine consists of a magnetostrictive actuator which is able to impart small displacements to a specimen upto 20 νm with resolution of 5 nm. The actuator is connected to a metal shaft and a diamond tip of 5 νm in radius is attached to the end of the shaft. Small displacements are applied to the specimen through the diamond tip. This makes it possible to construct a high stiffness loading fixture. The magnitude of load applied to the specimen is measured by a strain gauge type load cell with a load resolution of 10 νN. The specimen stage and load cell can be moved to adjust the loading position precisely by a stepping motor at a translation resolution of 0.1 νm. Cantilever beam type specimens with dimensions of 10 × 12 × 50 νm3 were prepared from a Ni-P amorphous thin film by focused ion beam machining. Very small cyclic load (ΔP = 0.1 - 40 mN) was able to be applied to the specimen successfully. This machine appears to be promising for evaluation of fatigue properties for micro-sized specimens for MEMS applications.
Built-In Strain in Polysilicon: Measurement and Application to Sensor Fabrication
Authors: Guckel H. 
Published: April 2011

AbstractThe built-in strain in deposited polysilicon films depends on film morphology. The strain may be compressive or tensile. Its magnitude and uniformity may be measured by using surface micro machining with test structures which require a single photomask level and use Euler buckling. Anneal cycles may be used to convert compressive strain to tensile or zero strain. Deposition and anneal cycles may be optimized to produce fine grained polysilicon with isotropic mechanical behavior.Strain field control can improve yield by reducing surface sticking. This mechanical stiffening is used in, for instance, pressure transducer construction. Built-in and applied axial strain are used to change the resonant frequencies of clamped-clamped beams in a vacuum envelope where quality factors up to 300,000 have been measured.
Properties of Low Residual Stress Silicon Oxynitrides Used as a Sacrificial Layer
Authors: Habermehl S. , Glenzinski A. K. , Halliburton W. M. , Sniegowski J. J. 
Published: April 2011

AbstractLow residual stress silicon oxynitride thin films are investigated for use as a replacement for silicon dioxide (SiO2) as sacrificial layer in surface micromachined microelectrical-mechanical systems (MEMS). It is observed that the level of residual stress in oxynitrides is a function of the nitrogen content in the film. MEMS film stacks are prepared using both SiO2 and oxynitride sacrificial layers. Wafer bow measurements indicate that wafers processed with oxynitride release layers are significantly flatter. Polycrystalline Si (poly-Si) cantilevers fabricated under the same conditions are observed to be flatter when processed with oxynitride rather than SiO2 sacrificial layers. These results are attributed to the lower post-processing residual stress of oxynitride compared to SiO2.
Characterization of Metallized Plastic MEMS
Authors: Chu Charles , Bachman Mark , Chiang Yuh-Min , Gonzales Fernando , Li G. P. 
Published: April 2011

AbstractMetallization of plastic devices is of interest to newer non-silicon based MEMS which are being developed for biomedical and other applications. The electrical properties of the metallization will depend, in part, on the material on which they are patterned, and the method of deposition. Of interest are the electrical characterizations during usage which must be studied to allow plastic MEMS designs to proceed wisely. Flexible microdevices may develop open circuits or shorts after excessive bending; joule heating may adversely affect the plastic substrates, leading to failure. We present some experimental studies on electrical characterization of metallized plastics as it relates to various processing conditons and usage scenarios.
Iron Sulfide (FeS2) Thin Films From Single-Source Precursors by Aerosol-Assisted Chemical Vapor Deposition (AACVD)
Authors: O'Brien Paul , Otway David J. , Park Jin-Ho 
Published: April 2011

AbstractDialkyl (or mixed alkyl)-dithiocarbamato iron(III) complexes have been used for the deposition of iron sulfide thin films using chemical vapor deposition techniques. The single-source precursors used in this work have been prepared by the reaction of FeCl3with dialkyldithiocarbamate sodium salts and characterized by a number of analytical techniques. Good quality thin films of FeS2 have been prepared from the single-source metal organic precursor, [Fe(S2CNMeiPr)3], by AACVD. XRD patterns of the films indicated crystalline iron sulfide (FeS2) grown at between 375 – 450 °C. SEM images show the films to have reasonable morphology and to be crystalline.
MOCVD of CuInE2 (Where E = S or Se) and Related Materials for Solar Cell Devices
Authors: Kemmler Michael , Lazell Michael , O'brien Paul , Otwaya David J. 
Published: April 2011

AbstractThin film(s) of chalcopyrite CuInE2(where E = S or Se) have been grown by low-pressure metal-organic chemical vapour deposition (LP-MOCVD) using the precursors [In(E2CNMenHexyl)3] and [Cu(E2CNMenHexyl)2]. Similarly, thin films of ME (where M = Zn, Cd; E = S, Se) have been deposited from precursors of general formula [M(E2CNMenHex)2]x. Films were grown on glass between 400 - 500 °C, and characterized by X-ray diffraction, optical spectroscopy (UV/Vis), EDAX and scanning electron microscopy.
Wet-Chemical Synthesis of Thin-Film Solar Cells
Authors: Raffaelle R.P , Junek W. , Gorse J. , Thompson T. , Harris J.D , Cowen J. , Hehemann D. , Rybicki G. , Hepp A.F. 
Published: April 2011

AbstractWe have been working on the development of wet-chemical processing methods that can be used to create thin film photovoltaic solar cells. Electrochemically deposition methods have been used to produce copper indium diselenide (CIS) thin films on molybdenum coated polymer substrates. CIS has an extremely high optical absorption coefficient, excellent radiation resistance, and good electrical conductivity and thus has proved to be an ideal absorber material for thin film solar cells. A series of compositionally different p-type CIS films were produced by using different electrochemical deposition potentials. Cadmium sulfide (CdS) window layers were deposited directly on these CIS films using a chemical bath process. CdS is a naturally ntype wide-bandgap semiconductor which has good transparency and is well lattice-matched to CIS. Zinc oxide thin films were grown by electrochemical deposition directly on the CdS films. ZnO is a transparent and conductive thin film that serves as the top contact of the cells. The structural and elemental properties of the individual ZnO, CdS and CIS films were characterized by x-ray diffraction and energy dispersive spectroscopy. The electrical behavior of the CdS on CIS junctions was determined using current versus voltage measurements. We will discuss the performance of these devices based on the physical properties of the component films and the processing methods employed in their fabrication.
Pentadionate: An Alternate Sol-Gel Method for the Synthesis of Ferroelectric Ba1−xSrxTiO3
Authors: Sharma Pramod K. , Jose K. A. , Varadan V. V. , Varadan V. K. 
Published: April 2011

AbstractSol-gel synthesis of transitional metal oxides is one of the important technique to obtain the pure and homogenous materials at low temperature. In this work, Barium strontium titantate (BST) was synthesized by sol-gel processing using 2,4-pentadionate as the precursors of metal oxides. The Ba1−xSrxTiO3 was prepared for four values of x i.e. 0.2, 0.4, 0.5 and 0.6. The obtained powders were heated from 400 °C to 800 °C at the interval of 100 °C to determine the temperature of crystallization. The phase of the final products was investigated by x-ray diffraction (XRD). Two particle sizes (< 100 nm and 200-400 nm) were observed under the scanning electron microscope (SEM) of the heat treated xerogel. The dielectric properties were determined by impedance analyzer at the frequency of 1MHz and explained in detail for the different values of x.
Effect of Layer Relaxation on the Internal Photoemission in Pt/Si1−xGex Schottky Barrier Type Infrared Detectors
Authors: Aslan B. , Turan R. , Nur O. , Karlsteen M. , Willander M. 
Published: April 2011

AbstractA Schottky type infrared detector fabricated on a p-type Si1−xGex substrate has a higher cut-off wavelength than one on a pure Si substrate because the barrier height of the Schottky junction on p-type Si1−xGex decreases with the Ge content and the induced strain in the Si1−xGex layer. We have studied the effect of the strain relaxation on the internal photoemission and I-V characteristics of a Pt/Si1−xGex Schottky junction with x=0.14. It is shown that the cut-off wavelength of the diode made on a strained Si0.86Ge0.14 layer is higher than that on a Si substrate as expected. This shows the possibility of tuning the range of these detectors in the mid-infrared region. However, the thermal relaxation in the Si0.86Ge0.14 layer is found to reduce the cut-off wavelength to lower values, showing that the difference between the Fermi level of the metal and the valence band edge increases with the layer relaxation. This effect should be taken into account when a Schottky type infrared detector is manufactured on a strained Si1−xGex film. I-V characteristics of the junctions also indicate an increase of the barrier height with the relaxation of Si1−xGex. These results demonstrate the band edge movements in a Si ixGex layer experimentally agree with the expected changes in the band structure of the Si1−xGex layer with strain relaxation.
Infrared Photosensitivity Due to the Yb-Induced Defect States in Pb1−xGexTe Alloys
Authors: Skipetrov E.P. , Chernova N.A. , Zvereva E.A. , Slyn'ko E.I. 
Published: April 2011

AbstractGalvanomagnetic properties and photoconductivity kinetics of Pb1−xGexTe(x≤0.04) alloys doped with Yb have been investigated. The alloys exhibit high infrared photosensitivity at temperature under 40 K; at helium temperature, the effect of persistent photoconductivity has been observed. The photoconductivity kinetics after terminating of infrared illumination consists of a fast and a long-term relaxation regions. We explain the observed effects by a capture of electrons into the Yb-induced states, that are subjected to the Jahn-Teller instability. The parameters of the Jahn-Teller states are estimated.
Strained SiGe Materials for High Quantum Efficiency Photodiodes at µ = 1.3 to 1.5µm
Authors: Giovane L. M. , Luan H.-C. , Fitzgerald E. A. , Kimerling L. C. 
Published: April 2011

AbstractSilicon-gemanium is a promising materials system for delivering near-IR photodetection on the ubiquitous silicon substrate. The 4% lattice mismatch leads to biaxial strain for SiGe films grown coherently on (100) Si substrates, which both extends the long wavelength detection limit by reducing the band gap and defines the critical thickness for the SiGe film. We have studied the use of strained-layer superlattices grown on high quality relaxed SiGe buffers. Graded buffers are ideal virtual substrates for achieving a complete range of compositions and strains for GeSi alloys. A physical model has been created to map out the absorption coefficient as a function of Ge fraction and (100) biaxial strain. Based on calculated absorption spectra as a function of composition and strain, we have designed and grown a Ge/Ge0.5Si0.5 strain-balanced superlattice on a high quality Ge0.75Si0.25 relaxed buffer using UHV-CVD. The strain-balanced superlattice has an effective absorption coefficient of 5000 cm−1. The relaxed buffer serves as a virtual substrate with relatively low threading dislocation density (106 cm-−2). The effect of the threading dislocations on the leakage current of P-I-N junctions is also investigated. Electron beam induced current (EBIC) is used to determine the dislocation density of SiGe relaxed buffer junctions grown with different grading rates. Mesa isolated devices are used to determine bulk leakage current densities for the SiGe junctions. The bulk leakage current density scales directly with the dislocation density. Bulk leakage currents density per dislocation length (2×10−5 A cml) agrees with deep level transient spectroscopy (DLTS) determined literature values for SiGe capture cross-section and defect density per dislocation in Si.
Progress in Antimonide-Based Mid-IR Lasers
Authors: Turner G.W. , Manfra M.J. , Choi H.K. , Goyal A.K. , Buchter S.C. , Calawa S.D. , Sanchez A. , Spears D.L. 
Published: April 2011

AbstractMid-infrared optically pumped semiconductor lasers (OPSLs) are presently being investigated for a variety of commercial and military applications. Active regions in such optically pumped lasers must meet the dual requirements of high gain and low loss at mid-IR wavelengths, combined with sufficient absorption of the optical pump at shorter wavelengths for efficient power conversion. In this paper we report the successful growth, fabrication, and characterization of high-performance OPSLs that employ novel active regions consisting of combinations of GalnAsSb integrated-absorber layers with type-II GaInSb/InAs quantum well regions. With 1.85-µm optical pumping at 85 K, OPSLs with such active regions have exhibited a peak output power of 2.1 W at 3.9 pm, improved beam quality, power conversion efficiency of ∼8%, and characteristic temperatures of ∼47 K.
Photoluminescence and EPR of Phosphorus Vacancies in ZnGep2
Authors: Moldovan M. , Stevens K. T. , Halliburton L. E. , Schunemann P. G. , Pollak T. M. , Setzler S. D. , Giles N. C. 
Published: April 2011

AbstractZinc germanium diphosphide (ZnGeP2) is a nonlinear optical material used in mid-infrared optical parametric oscillators. The near-infrared photoluminescence (PL) from single crystals of bulk ZnGeP2 has been studied as a function of excitation power, wavelength, temperature, and polarization. At 5 K, a broad PL band extending from 0.7 µm to beyond 1 µm is typically observed. Two distinct emissions with different polarization, power, and temperature behaviors have been resolved. These bands have peaks in intensity near 1.6 eV and 1.4 eV. The relative intensities of these two bands were found to correlate with the presence of phosphorus vacancies, as determined by electron paramagnetic resonance (EPR). A resonance in the intensity of the 1.6-eV band occurs when pumping into a level ∼90 meV below the minimum conduction band. This level is tentatively assigned to the shallow state.