bluuebunny/crossref_metadata_2025_split huggingface dataset:
EQCM and Quartz Crystal Impedance Measurements for the Characterization of Thiophene-Based Conducting Polymers
Authors: Arbizzani C. , Soavi F. , Mastragostino M. 
Published: April 2011

AbstractEQCM was extensively used to investigate ion-transport phenomena during dopingundoping processes of electronically conducting polymers. Several early studies assumed that the polymer films were rigidly coupled to the quartz crystal so as to relate the mass change to the quartz crystal resonant frequency change via the Sauerbrey equation. However, the rigidity of electronically conducting polymer films is doubtful and it has to be demonstrated. Quartz crystal impedance analysis near the resonance is of paramount importance to get insight into the viscoelastic properties of the film [1] and to avoid misleading in the interpretation of EQCM data.This contribution presents and discusses quartz crystal impedance measurements, performed with a Frequency Response Analyzer in the 9MHz region, and EQCM data collected for a dithienothiophene based polymer.
Polythiophene Grafted on Polyethylene Film
Authors: Chanunpanich N. , Ulman A. , Strzhemechny Y. M. , Schwarz S. A. , Domicik J. , Rafailovich M. , Sokolov J. , Janke A. , Braun H. G. , Kratzmüller T. 
Published: April 2011

AbstractWe have successfully grafted polythiophene on polyethylene (PE) film with a three reactions step: gas phase bromination on PE, yielding PE-Br; substitution reaction of PE-Br with 2-thiophene thiolate anion, following by chemical oxidative polymerization. The polymerization was carried out in a suspension solution of anhydrous FeCl3 in CHCl3, yielding a reddish PE-PT film after dedoping with ethanol. ATR-FTIR shows that the polythiophene (PT) was grafted on PE in the 2,5-position; on the other hand, PT homopolymer shows a small amount of 2,4 coupling. XPS reveals higher intensity of the S2p, including neutral and positive sulfur. SEM image reveals the island of PT on the PE film. AFM analysis found the thickness of the island is in the range of 120–145 nm. The conductivity of these thin films is in the range of 10−6 S/cm.
Polymer Electrolyte Actuator Driven by Low Voltage
Authors: Oguro K. , Asaka K. , Fujiwara N. , Onishi K. , Sewa S. 
Published: April 2011

AbstractComposites of perfluorinated polymer electrolyte membrane and gold electrodes bend in response to low-voltage electric stimuli and work as soft actuators like muscles. The composites were prepared by chemical plating. Charge on the electrode induces electric double layer and electro-osmotic drag of water by cation from anode to cathode through narrow channels in the perfluorinated ion-exchange resin. The electro-osmotic flow of water swells the polymer near the cathode rather than anode, and the membrane bends to the anode. The actuator comprises polymer electrolyte, electrodes, counter ion, solvent, lead wires, etc. Each component affects the performance of the actuator. Surface area of electrode and species of counter ion have drastic effect on voltage-displacement response. The response may depend on water channel structure of the polymer electrolyte. Modification of these factors improved the performance and resulted in the deflection over 360 degrees at a film actuator of 10 mm length. A tubular actuator was demonstrated as a multidirectional actuator. These actuators are applicable to artificial muscle, micro robots, or micro medical equipment inside body.
Compliant Actuators Based on Electroactive Polymers
Authors: Wax S G. , Sands R. R. , Buckley L. J. 
Published: April 2011

AbstractThe field of Electroactive Polymers has experienced a considerable amount of expansion over the last decade. Much of this work has been concentrated on developing polymeric materials that mimic biological systems or that exhibit electronic and optical properties similar to inorganic materials. This paper briefly reviews some of the nearer term applications that electroactive polymers might impact: image processing and sonar. In addition, a review of compliant actuators based on the unique properties inherent in electroactive polymers is provided. Emphasis will be placed on the mechanisms responsible for actuation and on the limited mechanical, electrical and chemical data current available. A comparison between mammalian muscle properties and electroactive polymer actuator properties is provided.
Assessing Failure Mechanisms During Transformation Superplasticity of Ti-6Al-4V
Authors: Schuh C. , Dunand D. C. 
Published: April 2011

AbstractDuring thermal cycling through the α/β phase transformation under the action of a small external biasing stress, Ti alloys exhibit an average deformation stress exponent of unity and achieve superplastic strains. We report tensile experiments on Ti-6Al-4V with an applied stress of 4.5 MPa, aimed at understanding the failure processes during transformation superplasticity. The development of cavities is assessed as a function of superplastic elongation, and macroscopic neck formation is quantified at several levels of elongation by digital imaging techniques. The effects of thermal inhomogeneity on neck initiation and propagation are also elucidated experimentally.
Influence of Deformation Speed on Fatigue and Tensile Properties of a Ti-Ni-Cu Shape Memory Alloy
Authors: Kishi Y , Yajima Z. , Shimizu K , Asai M. 
Published: April 2011

AbstractThe mechanical fatigue life and tensile property of a Ti-41at.%Ni-8.5at.%Cu alloy, which was solution-treated after some thermo-mechanical treatments, were investigated at 370±1 K as a function of deformation speed. The tensile properties were also investigated at 295±1 K as a function of deformation speed. The B2→B19 martensitic transformation start temperature, Ms, of the alloy was determined to be 338 K by a differential scanning calorimetry, while that of the as-rolled alloy could not be determined. Two types of fatigue tests were carried out by using plate-shaped specimens of 3.5 mm width and 1.5 mm thickness with sinusoidal waveform stresses of 20 Hz and 0.5 Hz frequencies being applied respectively. The fatigue life obtained from the 20 Hz tests was superior to that from the 0.5 Hz tests, the former being about 2 times longer than the latter at the same stress level. Tensile tests were performed at three tensilem speeds of 8.3 × 106, 8.3 × 10−5 and 8.3 × 10−3 m/s. In all the stress - strain curves obtained, an apparent yielding was observed after the liner elastic deformation. The apparent yielding is due to the occurrence of martensitic transformation. The critical stress for inducing martensite and tensile fracture stress increased with increasing tensile speed. Therefore, it is clear that fatigue and tensile properties of Ti-Ni-Cu shape memory alloys are strongly affected by not only test temperature but also deformation speed.
Properties and Applications of Magnetorheological Fluids
Authors: Jolly M.R. 
Published: April 2011

AbstractMagnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in rheological behavior. Typically, this change is manifested by the development of a yield stress that monotonically increases with applied field. Interest in MR fluids derives from their ability to provide simple, quiet and rapid response interfaces between electronic controls and mechanical systems. In this paper, the basic composition and properties of example MR fluids are reviewed. Some contemporary applications of MR fluids are then discussed.
Computer Microvision for MEMS
Authors: Freeman Dennis M. 
Published: April 2011

AbstractWe have developed a versatile instrument for in situ measurement of motions of MEMS. Images of MEMS are magnified with an optical microscope and projected onto a CCD camera. Stroboscopic illumination is used to obtain stop-action images of the moving structures. Stopaction images from multiple focal planes provide information about 3D structure and 3D motion. Image analysis algorithms determine motions of all visible structures with nanometer accuracy.Hardware for the system includes the microscope, CCD camera and associated frame grabber, piezoelectric focusing element, and a modular stimulator that generates arbitrary periodic waveforms and synchronized stroboscopic illumination. These elements are controlled from a Pentium-based computer using a graphical user interface that guides the user through both data collection and data analysis. The system can measure motions at frequencies as high as 5 MHz with nanometer resolution, i.e., well below the wavelength of light.
Effect of As-Processed and Annealed Microstructures on the Mechanical Properties of Liga Ni MEMS
Authors: Xie Z. L. , Pan D. , Last H. , Hemker K. J. 
Published: April 2011

AbstractMicrostructure – mechanical property relations of 200 μm thick LIGA deposited Ni films have been investigated with a combination of optical cross-sectional microscopy and microsample tensile testing. Measurements of the grain size and morphology of nine different asdeposited films evidenced a predominantly columnar microstructure with significant variations in grain size. These as-deposited microstructural variations resulted in a range of Young's modulus, yield strength, and ultimate tensile strength values that are consistent with previously reported measurements, but these values did not appear to scale with the as-deposited microstructures. By contrast, significant changes in both the microstructure and mechanical properties were observed when these films were annealed at 800'C for 1 hour. Recrystallization and grain growth transformed the grain morphology from columnar to equiaxed, which resulted in a dramatic decrease in the tensile strength and corresponding increase in the ductility of the annealed films.
Static and Dynamic Characterization of Buckled Composite SiO2-Au Microbridges
Authors: Nicu L. , Bergaud C. , Martinez A. , Temple-Boyer P. 
Published: April 2011

AbstractTheoretical and experimental investigations have been made to study the nonlinear static and dynamic behavior of composite Si02-Au microbridges. Measurements of maximal deflection amplitude were carried out on arrays of clamped-clamped SiO2-Au beams buckling under the effect of thin film effective residual stress. The static analysis adresses the issue of microfabricated beam buckling from an energy point of view. SiO2-Au and Au effective residual stresses are evaluated by considering the measured buckling maximal deflection and by through an adequate approximation of the shape of the microbeam deflection curve. The dynamic approach is based on a direct analytical model yielding an exact solution to the linear problem associated with the nonlinear vibrations of initially buckled clamped-clamped structures. Several experimental multi-mode dynamic responses of composite buckled beams are also given to illustrate the validity and accuracy of this analytical model.
Synthesis of High-K Titanium Oxide Thin Films Formed by Metalorganic Decomposition
Authors: Fukuda Hisashi , Ishikawa Yoshihiro , Namioka Seiogo , Nomura Shigeru 
Published: April 2011

AbstractTitanium oxide (TiO2) thin ftlms were formed on a Si substrate by metalorganic decomposition(MOD) at temperatures ranging from 600 to 1100°C. As-deposited films were in the amorphous state and were completely transformed after annealing at 600°C to a crystalline structure with anatase as its main component. During crystallization, a reaction between TiO2 and Si occurred at the interface, which resulted in the formation of a thin interfacial SiO2 layer. Capacitance-voltage measurement showed good dielectric properties with a maximum dielectric constant of 76 for films annealed at 700°C. For the crystallized TiO2 films, the interface trap density was 1 × 1011 cm−2 eV−1, and the leakage current was 1 × 10−8 A/cm2 at 0.2 MV/cm. The modified structure of TiO2/SiO2/Si is expected to be suitable for the dielectric layer in an integrated circuit in place of conventional SiO2 films.
Selection and Design of Precursors for the MOCVD of Lead Scandium Tantalate
Authors: Jones A.C , Davies H.O. , Leedham T.J. , Crosbie M.J. , Wright P.J. , Brien P.O'. , Fleeting K.A. 
Published: April 2011

AbstractMetalorganic chemical vapour deposition (MOCVD) is a promising technique for the deposition of the pyroelectric oxide lead scandium tantalate, Pb(Sc0.5Ta0.5)O3. In order to exploit the full potential of the method, it is important to identify the optimum combination of precursors so that process parameters and film properties are optimised. In this paper, the molecular design of new, more compatible Ta and Sc oxide precursors is described and it is shown how the use of carefully matched precursors allows the growth of Pb(Sc0.5Ta0.5)O3 in the required perovskite phase at low substrate temperatures.
Deposition of SiO2:F:C Films With Low Dielectric Constant and With High Resistance to Annealing
Authors: Lubguban J. , Kurata Y. , Inokuma T. , Hasegawa S. 
Published: April 2011

AbstractSiO2:F:C films were deposited using a plasma-enhanced chemical vapor deposition (PECVD) technique from SiH4/O2/CF4/CH4 mixtures. Increasing amount of carbon were introduced to the SiO2:F films by changing the CH4 flow rate, [CH4], while keeping constant other conditions such as rf power and deposition temperature, TD. It was found that the addition of CH4 decreases the dielectric constant, k; from 3.36 for [CH4] = 0 sccm to 2.95 for [CH4] = 8 sccm. For the [CH4] condition where the film has a lowest k, the deposition temperature and rf power were optimized by depositing films using different values of TD and rf power The k for films in the new series as well as the stress and water absorption was investigated. Results show that the dielectric constant further decrease up to 2.85. Some films were then annealed from 400 - 800 °C and it was found that the k for films deposited with higher [CH4] has a better stability with respect to annealing up to a temperature of 600 °C.
Time-Resolved Photoluminescence Studies of InxGa1−xAs1−yNy
Authors: Smith M. , Mair R. A. , Lin J.Y. , Jiang H. X. , Jones E. D. , Allerman A. A. , Kurtz S. R. 
Published: April 2011

AbstractTime-resolved photoluminescence spectroscopy has been used to investigate carrier decay dynamics in InxGa1−xAs1−yNy (x ∼ 0.03, y ∼ 0.01) epilayers grown on GaAs by metalorganic chemical vapor deposition. Time-resolved PL measurements, performed for various excitation intensities and sample temperatures, indicate that the broad PL emission at low temperature is dominated by localized exciton recombination. Lifetimes in the range of 0.07–0.34 ns are measured; these photoluminescence lifetimes are significantly shorter than corresponding values obtained for GaAs. In particular, we observe an emission energy dependence of the decay lifetime at 10 K, whereby the lifetime decreases with increasing emission energy across the PL spectrum. This behavior is characteristic of a distribution of localized states, which arises from alloy fluctuations. We have also studied the effects of post-growth rapid thermal annealing (RTA) on the integrated photoluminescence emission intensity, which indicate that the optimal annealing conditions is 690 °C when annealed for 120 seconds in a nitrogen ambient.
Germanium Photodetectors for Silicon Microphotonics by Direct Epitaxy on Silicon
Authors: Luan Hsin-Chiao , Lim Desmond R. , Colace Lorenzo , Masini Gianlorezo , Assanto Gaetano , Wada Kazumi , Kimerling Lionel C. 
Published: April 2011

AbstractWe have grown high-quality Ge epilayers on Si using two-step ultrahigh vacuum/chemical-vapor-deposition followed by post-growth cyclic thermal annealing. Cyclic annealing was effective in reducing threading dislocation densities. The annealing process was improved by optimizing the dislocation velocity. We fabricated and tested metal-semiconductor-metal planar photodetectors using Ge epilayers grown on Si. Our measurement showed an improvement in the photodetector performance as a result of the improved materials quality. The process described in this paper for making high-quality Ge on Si is uncomplicated and can be easily integrated with Si CMOS processes.
PbEuTe/PbTe Multi-Quantum Wells: Structural and Optical Properties
Authors: Abramof E. , Rappl P.H.O. , Ueta A.Y. , Motisuke P. , Ferreira S.O. 
Published: April 2011

AbstractA series of Pb1−xEuxTe/PbTe multi-quantum well (MQW) samples were grown on (111) cleaved BaF2substrates by molecular beam epitaxy. The Eu content was maintained at x∼0.06 and the PbTe well width was varied from 50 to 200 Å. The co/2Θ scans of the (222) Bragg reflection showed very well resolved satellite peaks for all samples indicating that sharp interfaces were obtained. The strain inside the MQW structure was obtained as a function of the PbTe well width by fitting the ω/2Θ scans to the ones calculated by dynamical theory of x-ray diffraction. The transition energies between the confined states in the conduction and valence bands of the PbTe well were determined through the infrared transmission measurement analysis.
Development of Large High-Quality Chalcopyrite Single Crystals for Nonlinear Optical Applications
Authors: Ruderman W. , Zwieback I. 
Published: April 2011

AbstractStriking progress has been made in the development of thigh optical quality, large size and low absorbing single crystals of ZnGeP2, AgGaS2 and CdGeAs2. This will now enable continuously tunable infrared laser sources to be built covering the spectral region from 3.9 to 11 µm.
Electronic Structure and Derived Linear and Nonlinear Optical Properties of Chalcopyrites
Authors: Lambrecht Walter R. L. , Rashkeev Sergey N. , Limpijumnong Sukit , Segall Benjamin 
Published: April 2011

AbstractThe electronic band structures were calculated for a number of chalcopyrites in both the II-IV-V2 and I-III-VI2 families using the linear muffin-tin orbital method. From these band structures, the second harmonic generation coefficients were calculated using a recently developed methodology in which a separation is made of inter- and intraband contributions. We found that the high value of d36 in CdGeAs2 is in large part due to the fact, that in this material, unlike in the other chalcopyrites, almost no compensation occurs between inter- and intraband contributions, the former one being unusually small. For the case of ZnGeP2, a detailed investigation of the band structure, reveals that it has an indirect band gap rather than a pseudodirect one. The implications of this for the interpretation of the optical spectra are discussed. Finally, for the I-III-VI2 materials, we find that the Te based materials have far higher d36 than the selenides. Combined with their potential for non-critical phase matching, this makes AgGaTe2 an interesting compound.
I-V CHARACTERISTICS OF a-Si:H p-i-n Diodes with Uniform and Non-Uniform Defect Distributions
Authors: Kroon M.A. , van Swaaij R.A.C.M.M. , Metselaar J.W. 
Published: April 2011

ABSTRACTThis paper compares a-Si:H p-i-n diodes having a spatially uniform distribution of defect states with diodes in which the defect distribution is non-uniform, i.e. equilibrated according to the Defect-Pool model. Diodes with a uniform defect distribution exhibit a clear dependence of the current-voltage characteristics on the width of the intrinsic region, whereas in equilibrated diodes, this dependence is absent. This difference is explained by comparing the space-charge distribution and the recombination profile of the intrinsic region in both types of diodes.
Er environment in a-Si:HEr> prepared by PECVD
Authors: Piamonteze Cínthia , Tessler Leandro R. , Tolentino Hélio , Alves Maria do Carmo Martins , Weiser Gerhard , Terukov Eugeny 
Published: April 2011

ABSTRACTThe Er local environment of a-Si:H<Er> prepared by PECVD using a metalorganic precursor was determined by EXAFS. We found that in as-deposited samples Er is coordinated to 6 oxygen atoms at 2.28±0.01Å, very similar to Er2O3. Annealing at 420°C hardly affects the Er neighborhood, but higher annealing temperatures (starting at 600°C up to 1033°C) decrease the Er-O separation as much as 0.05Å, maintaining the Er average coordination around 6. This is interpreted as due to the formation of a carbon second neighbor shell. Our results show that the Er local environment is not related with the luminescence enhancement for annealing at moderate temperatures.
Large Area Flexible Amorphous Silicon Position Sensitive Detectors
Authors: Fortunato Elvira M.C. , Brida Donatello , Ferreira Isabel M.M. , Åguas H. M.B. , Nunes Patrícia , Cabrita Ana , Giuliani Franco , Nunes Yuri , Maneira Manuel J.P. 
Published: April 2011

ABSTRACTLarge area thin film position sensitive detectors based on amorphous silicon technology have been prepared on polyimide substrates using the conventional plasma enhanced chemical vapour deposition technique. The sensors have been characterised by spectral response, illuminated I-V characteristics and position detectability measurements. The obtained one dimensional position sensors with 5 mm wide and 60 mm long present a maximum spectral response at 600 nm, an open circuit voltage of 0.6 V and a position detectability with a correlation of 0.9989 associated to a standard deviation of 1×10−2, comparable to those ones produced on glass substrates. The surface of the sensors at each stage of fabrication was investigated by Atomic Force Microscopy.
Hot-electron Phototransistors in Hydrogenated Amorphous Silicon
Authors: Shannon J. M. , Gerstner E. G. 
Published: April 2011

ABSTRACTIt has been shown that useful current gains can be obtained in hot-electron device structures containing very thin chromium disilicide layers of nanometer dimensions in hydrogenated amorphous silicon [1]. The a-Si:H/a-CrSi2/a-Si:H device structure made using PECVD and sputtering techniques naturally forms a hot-electron transistor device where the electrons are emitted across a high potential barrier on one side of the silicide and are collected over a low barrier on the other. Recent results [2] have shown that current gains can be in excess of 40 in structures having a-CrSi2 bases ∼1 nm thick.Here we outline the relatively simple technology used to make these devices and examine their performance as phototransistors in which the photo-current is amplified by hot-electron transistor action. The speed of response can be maximised by operating the phototransistor with high electric field across the collector since it is the transit time of the photo-induced carriers that determines the response time. We show that these devices provide a useful new active element for large area amorphous silicon electronics.
Increase of Hydrogen-Radical Density and Improvement of The Crystalline Volume Fraction of Microcrystalline Silicon Films Prepared by Hot-Wire Assisted Pecvd Method
Authors: Yoshida Norimitsu , Itoh Takashi , Inouchi Hiroki , Harada Hidekuni , Inagaki Katsuhiko , Yamana Noriyuki , Yamamoto Kanta , Nonomura Shuichi , Nitta Shoji 
Published: April 2011

ABSTRACTHigher crystalline Si volume fractions in hydrogenated microcrystalline silicon ( µc-Si:H) films have been achieved by the hot-wire assisted plasma enhanced chemical vapor deposition (HWA-PECVD) method compared with those in films by conventional PECVD. µc-Si:H films can also be prepared by HWA-PECVD under typical conditions used for preparing hydrogenated amorphous silicon (a-Si:H) films by PECVD, in which the hydrogen-dilution ratio (H2 / SiH4) is ∼ 10. The hot wire seems to produce hydrogen radicals. As a result, the HWA- PECVD method can control hydrogen-radical densities in the RF plasma, and this method can also control the ratio of hydrogen coverage at the surface of the film.