bluuebunny/crossref_metadata_2025 huggingface dataset:
Documenting the Impact of Assistive Listening Technology in the Classroom
Authors: Palmer Catherine V.
Published: February 2009

When assistive technology is recommended for an individual or group in a classroom, the professional must be prepared to provide data regarding the impact of the listening system. Teachers, parents, and school administrators require data to document the effectiveness of any recommendation that will ultimately impact their classrooms, children, and bottom line. Traditionally, clinical measurements and questionnaires have been used to document the efficacy of using assistive listening technology for a particular child. Clinical measurements lack the face validity needed to communicate expected results in the classroom. Questionnaires are fraught with problems of bias from the respondees. This article presents a method of structured observation that we have used to evaluate the impact of assistive technology on individual children and classrooms. A case study is presented as an example of the use of this technique.
Electron structure and photoluminescence behavior of Ti0.09Y1.91O2S
Authors: Tang Yujing , Dai Shouyu , Fang Yan
Published: February 2009

The Ti-doped yttrium oxysulfide (Ti0.09Y1.91O2S) was synthesized by sintering the mixture of sulfur (S)- and Ti-doped yttrium oxide (Ti0.09Y1.91O3); Ti0.09Y1.91O3, the same as yttrium oxide, form cubic lattice (C-type) with six coordinated polyhedron of the metal ions, but the synthesized Ti0.09Y1.91O2S displays trigonal P3¯m1 structure. X-ray photoelectron spectrograph analysis reveals that the Ti ion is in quadrivalence state, no Ti2+ and Ti3+ ions were found. Besides, the shift of core level Ti 2p and valence band top was observed, which results from the change in the lattice structure. The changes in electronic state density are attributed to an increase in sulfur and a decrease in oxygen. Under the wavelength of 514.5 nm radiation of Ar-ion Laser excited, Ti-doped Y2O3 shows an asymmetry emission spectrum at about 644 nm, and Ti0.09Y1.91O2S has two broad bands emission spectra centered at 744 and 383 nm have been observed. The two broad bands correspond to usual fluorescence and upconversion spectrum, respectively. We assume that the Ti 3d level structure is similar to the Mn 3d one of manganites. The observed emission spectra were attributed to the spin-allowed T32g-T31g and T31g-T31g transition. The relation between electron structure and luminescence behavior was discussed in detail.
Domain-acoustic echo phenomenon in europium garnet and iron borate
Authors: Mamniashvili G. I. , Sharimanov Y. G. , Pohorily A. M. , Kuzmak O. M.
Published: February 2009

The results of a comparative study of domain-acoustic echo (DAE) signals in polycrystalline ferrite Co0.01Mn0.05Cu0.18Ni0.2Mg0.72Fe0.6O4, europium garnet, and iron borate are presented. The DAE signals were observed at 20MHz. They possess a long time memory and are related with displacements of domain walls. In particular, DAE in the europium garnet is characterized by particularly intensive signals and has the lowest threshold for exciting radio-frequency pulse powers and suppressing magnetic field values.
Ferromagnetic resonance study of MnAs∕(Ga,Mn)As bilayers
Authors: Cubukcu M. , von Bardeleben H. J. , Khazen Kh. , Cantin J. L. , Zhu M. , Wilson M. J. , Schiffer P. , Samarth N.
Published: February 2009

We report the investigation of the static and dynamic magnetic properties of type-A MnAs∕Ga0.945Mn0.055As (001) bilayers. Static magnetization measurements show them to be ferromagnetically coupled with an exchange bias field of ∼340Oe. The magnetocrystalline anisotropy constants of the (Ga,Mn)As layer were determined by X-band ferromagnetic resonance (FMR) spectroscopy. The (Ga,Mn)As layers are magnetically inhomogeneous as evidenced by a strong broadening of the (Ga,Mn)As uniform mode linewidth. The MnAs FMR spectra reveal the presence of a small MnAs fraction with a different orientation.
Magnetic, transport, and magnetocaloric properties of double perovskite oxide LaCaMnCoO6
Authors: Mahato Rabindra Nath , Bharathi K. Kamala , Sethupathi K. , Sankaranarayanan V. , Nirmala R. , Nigam A. K. , Lamsal Jagat
Published: February 2009

Magnetic, magnetoresistive, and magnetocaloric properties of a novel double perovskite oxide, namely, LaCaMnCoO6 have been studied. Polycrystalline sample of LaCaMnCoO6 has been synthesized by sol-gel technique. It has cubic crystal structure (space group Fm3¯m) at room temperature. The temperature variation in magnetization reveals a steep increase in magnetization around 168K (TC). The magnetization does not even saturate at 5K and a magnetic moment of 0.7μB∕f.u. is obtained at 5K in an applied field of 50kOe. The electrical resistivity measurement indicates that the material is semiconducting-like in the temperature range of ∼300–50K and below ∼50K the sample becomes insulating. A maximum magnetoresistance (MR) of about 8% is found at 200K in an applied field of 7T and MR has a negative sign. The magnetocaloric effect is calculated from the magnetization versus temperature data and a maximum magnetic entropy change of 3.1J∕kgK for a field change of 11kOe is obtained near TC. Thus a moderate magnetocaloric effect is achieved in rather low magnetic fields.
Ferromagnetism in tetragonally distorted LaCoO3 thin films
Authors: Mehta Virat Vasav , Liberati Marco , Wong Franklin J. , Chopdekar Rajesh Vilas , Arenholz Elke , Suzuki Yuri
Published: February 2009

Thin films of epitaxial LaCoO3 were synthesized on SrTiO3 and (La,Sr)(Al,Ta)O3 substrates, varying the oxygen background pressure in order to evaluate the impact of epitaxial growth as well as oxygen vacancies on the long range magnetic order. The epitaxial constraints from the substrate impose a tetragonal distortion compared to the bulk form. X-ray absorption and x-ray magnetic circular dichroism measurements confirmed that the ferromagnetism arises from the Co ions and persists through the entire thickness of the film. It was found that for the thin films to show ferromagnetic order they have to be grown under the higher oxygen pressures. A correlation of the structure and magnetism suggests that the tetragonal distortions induce the ferromagnetism.
WC/a-C nanocomposite thin films: Optical and electrical properties
Authors: Abad M. D. , Sánchez-López J. C. , Cusnir N. , Sanjines R.
Published: February 2009

WC/amorphous carbon (a-C) thin films were deposited by dual magnetron sputtering from individual WC and graphite targets. The influence of film composition and microstructure on the optical and electrical properties was investigated. As evidenced by x-ray photoelectron spectroscopy and grazing angle x-ray diffraction measurements, the WC/a-C films are composite materials made of hexagonal W2C and/or cubic β-WC1−X nanocrystallites embedded in (a-C) matrix. The optical properties were studied by spectroscopic ellipsometry and the electrical resistivity was measured by the van der Pauw method between 20 and 300 K. Both the optical and the electrical properties of the WC/a-C films are correlated with the chemical composition and microstructure evolution caused by a-C addition. The optical properties of W2C/a-C and β-WC1−x/a-C films with a-C content ≤10 at. % are explained by modeling their dielectric functions by a set of Drude–Lorentz oscillators. Further increase in a-C content leads only to the formation of β-WC1−x/a-C nanocomposite structures and their optical properties progressively evolve to those of a-C single phase. The electrical resistivity as a function of the temperature of all the films exhibits a negative temperature coefficient of resistivity. Theoretical fitting using the grain-boundary scattering model shows that the transport properties are mainly limited by the grain size and electron mean free path parameters.
Humidity effects on lubricant transfer in the head-disk interface of a hard disk drive
Authors: Kim Sang Hoon , Dai Qing , Marchon Bruno , Flechsig Karl
Published: February 2009

As head-media spacing decreases down to 10nm in the current hard disk drive systems, interaction of lubricant on the disk with a flying slider becomes increasingly important. With this extremely small spacing, environmental conditions such as temperature and humidity influence the interaction in the head-disk interface and lubricant transfer between the disk surface and the slider surface. This paper describes a systematic and quantitative study on humidity effects on the amount of lubricant transfer between the disk surface and the slider surface. The lubricant transfer was proportional to absolute humidity, absolute amount of water in the system, rather than relative humidity alone. Profiles of depleted lubricant layer on the disk surface also showed that the increase in the amount of transferred lubricant was directly related to the increase in the mobility of the lubricant with higher absolute humidity rather than with relative humidity alone.
Microwave-induced combustion synthesis of Li0.5Fe2.5−xMgxO4 powder and their characterization
Authors: Fu Y. P. , Lin C. H.
Published: February 2009

Li 0.5 Fe 2.5 − x Mg x O 4  (0≦x≦1.0) powders with small and uniformly sized particles were successfully synthesized by microwave-induced combustion using lithium nitrate, ferric nitrate, magnesium nitrate, and carbohydrazide as the starting materials. This process takes only a few minutes to obtain as-received Mg-substituted lithium ferrite powders. The results revealed that the lattice constant increases nonlinearly with increasing Mg content in the Li0.5Fe2.5−xMgxO4 specimens. Moreover, the magnetic properties of Mg-substituted lithium ferrite were also strongly affected by Mg concentration. The saturation magnetization (Ms) of 71.1 emu/g was found at Li0.5Fe2.5O4 specimen. As increased Mg content, the saturation magnetization (Ms) and remanent magnetization (Mr) decreased significantly. This is ascribed to the fact that as Mg content increases, A-O-B (where A represents tetrahedral sites and B represents octahedral sites in ferrite of the spinel type) interactions become weak, and consequently B-O-B interaction becomes stronger. Transmission electron microscopy (TEM) micrograph revealed that Mg-substituted lithium ferrite powders are distributed in the range from 50 to 80 nm with well-defined crystallinity.
High magnetic properties of nanocomposite ribbons made with Mischmetals–Fe–Co–Ti–B alloys
Authors: Chang H. W. , Chen C. H. , Chang C. W. , Hsieh C. C. , Guo Z. H. , Chang W. C.
Published: February 2009

Magnetic properties, phase constitution, and microstructure of melt spun R-lean and B-enriched Mischmetal (MM)–Fe–Co–Ti–B nanocomposites have been investigated. The thermal magnetic analysis show that only 2:14:1 and α-Fe [α-(Fe,Co)] phases appear for MM(A)9.5Fe78.5Ti2B10 and MM(A)9Fe79.5Co2.5Ti1B8 ribbons, while an additional Fe3B phase is present for R9.25Fe79.25Co2.5Ti1B8 [R=MM(A), MM(B), and MM(C)] ribbons. The magnetic properties of the above nanocomposites are determined not only by the phase constitution of MM–Fe–Co–Ti–B nanocomposites but also by the composition of MMs. Besides, fine grain size of 15–40 nm is almost unchanged for the ribbons with various MMs, giving rise to the strong exchange coupling effect between magnetic grains and the improved magnetic performance. In this study, the optimum magnetic properties of Br=9.6 kG, Hic=8.6 kOe, and (BH)max=18.2 MG Oe can be achieved for MM(B)9.25Fe79.25Co2.5Ti1B8 nanocomposites.
New quarternary half metallic material CoFeMnSi
Authors: Dai Xuefang , Liu Guodong , Fecher Gerhard H. , Felser Claudia , Li Yangxian , Liu Heyan
Published: February 2009

A good field to develop new materials with half metallicity is the quaternary Heusler alloys. The preferred route is to combine the compounds that have been already grown in Heusler structure. As a typical example, the quaternary LiMgPdSb-type CoFeMnSi have been investigated in detail. For the quaternary LiMgPdSb-type compounds, three nonequivalent structures exist. From the calculated density of state (DOS) results, it can be seen that one superstructure shows half metallicity. The second superstructure has a pseudogap at the Fermi level. The third superstructure shows metallic behavior. Based on the analysis of the measured XRD pattern and magnetization curve, we can deduce that the CoFeMnSi compound is crystallized in the structure where half metallicity occurs.
Giant magnetoresistance in composites of organic polymers with manganese acetylacetonate and lanthanum-praseodymium chlorides exhibiting ionic conductivity
Authors: Rakhimov R. R. , Amponsah O. K. , Waller L. A. , Shevchenko V. G. , Karmilov A. Y. , Alexandrov I. A. , Aleksandrov A. I.
Published: February 2009

We present a new giant magnetoresistance (GMR) material composed of polyaniline, polystyrene, sulfur, manganese acetylacetonate, lanthanum, and praseodymium chlorides. These compounds were mixed and processed mechanochemically to obtain thin films. External magnetic field of 6000 Oe increases conductivity of films by more than 300%. Analysis of transient current kinetics after application of constant voltage (10 V) to samples showed the existence of three types of charge carriers, which we identified as e−, H+, and Cl−. Contribution of functional groups of polyaniline and elemental sulfur S in the formation of the above charge carriers in this new GMR composite material is discussed.
Variations in optical transmittance with magnetic fields in nanosized FePt ferrofluid
Authors: Wu Kung-Tung , Yao Y. D. , Chang Cheng-Wei
Published: February 2009

The optical transmittance increases with decreasing the concentration of FePt in both water-based and hexane-based ferrofluids. However, under an applied magnetic field H, the transmittance T increases with increasing H field. The variation in transmittance ΔT increases rapidly for samples in hexane at H=182 Oe. However, ΔT is very small for samples in distilled water. This can be explained due to the different aggregation ability of magnetic particles in ferrofluid. For the samples in hexane, its larger aggregation ability makes the magnetic particles easier to agglomerate and becomes much more chainlike elongated along the perpendicular magnetic field. Thus, it makes the area covered by the droplets per unit area in ferrofluid decrease and the ΔT increases with increasing the magnetic field. However, for samples in hexane, the optical properties may also be related with the Mie resonance. At H>60 Oe, the particle aggregation occurs and elongates more along the magnetic fields. This would cause the longitudinal plasmon resonance absorption to shift to a longer wavelength. Therefore, the absorption increases and the variation in transmittance ΔT decreases with increasing the incident wavelength.
Synthesis and characterization of magnetic nanoparticles embedded in polyvinyl pyrrolidone nanofiber film by electrospinning method
Authors: Lin Chun-Rong , Tsai Tsu-Chi , Chung Max , Lu Shih-Zong
Published: February 2009

We fabricated magnetic nanofiber films by manufacturing the nanoparticles with the polyol process followed by the electrospinning process to combine them into a thin film. The magnetite (Fe3O4) nanoparticles with mean crystallite size of 6–8 nm were synthesized through reduction of iron (II) acetate in the polyols and using polyvinyl pyrrolidone (PVP) as the protecting agent. The PVP-coated Fe3O4 nanoparticles were dispersed into PVP ethanol solution and then electrospun directly to make nanofiber films. The diameters of fibers range between 200–400 nm, and the film thickness is about 50 μm. The Fe3O4 nanoparticles show a saturation magnetization of 36.6 emu/g, and together with the nanofiber films display a superparamagnetic behavior.
Coexistence of ferromagnetism and cluster glass state in superconducting ferromagnet RuSr2Eu1.5Ce0.5Cu2O10−δ
Authors: Nigam R. , Pan A. V. , Dou S. X.
Published: February 2009

Systematic dc and ac magnetic susceptibility measurements performed on RuSr2Eu1.5Ce0.5Cu2O10−δ (Ru1222) demonstrate a paramagnetic to ferromagnetic transition around 95 K. The third harmonic of the ac susceptibility reveals that the system undergoes a spin glass transition below 75 K. The features of the zero-field cooled and field cooled dc magnetization curves of Ru1222 material resemble those of a cluster glass state, rather than those of a canonical spin glass state. The magnetization versus applied field loops do not saturate, even at very high applied fields, resulting in the short range magnetic order in the system, which facilitates the formation of clusters that freeze at low temperature. The temperature dependence of the second and third harmonic ac susceptibilities further confirms the coexistence of a cluster glass state and ferromagnetic order in the Ru1222 system.
Calculation of electronic structures and magnetic moments of Nd2Fe14B and Dy2Fe14B by using linear-combination-of-pseudo-atomic-orbital method
Authors: Kitagawa Isao
Published: February 2009

The electronic structure and magnetic moment of Nd2Fe14B and Dy2Fe14B were calculated by using the linear-combination-of-localized-pseudo-atomic-orbital (LCPAO) method. Magnetic moments of iron atoms in Nd2Fe14B are enhanced by spin-orbit interaction and are in good agreement with experiments. The full relativistic treatment improves calculation of the magnetic moment. In Dy2Fe14B, the total magnetic moment is 12.75 μB/f.u., which is in good agreement with experimental data, 11.3 μB/f.u. The magnetic moment calculation obtained by using LCPAO is suitable for large-scale systems with rare-earth elements.
Improved plasma uniformity in a discharge system with electron injection
Authors: Vizir A. V. , Tyunkov A. V. , Shandrikov M. V.
Published: February 2009

We present the results of experiments leading to improvement in bulk plasma uniformity of a constricted-arc discharge system with electron injection. The steady-state discharge was in argon, at a gas pressure of 0.5 mTorr, and operated with a main discharge voltage between 20 and 100 V and current between 3 and 15 A. The radial plasma distribution was measured with a movable Langmuir probe. We find that geometric modification of the intermediate electrode exit aperture and the main discharge cathode add little to the plasma uniformity. Improved bulk plasma uniformity is observed when a special distributing grid electrode is used and the main discharge voltage is less than 20–30 V. The application of a weakly divergent magnetic field in the region of the intermediate electrode exit aperture decreases the plasma nonuniformity from 20% to 14% over a radial distance of 30 cm. The plasma uniformity was further improved by compensating the magnetic self-field of the injected electron beam by a reverse magnetic field produced with a special electrode compensator. It is shown that an increase in discharge current causes a proportional increase in back current in the distributing electrode. The approach allows a decrease in plasma nonuniformity from 20% to 13% over a radial distance of 30 cm.
The effect of proton irradiation on magnetic properties of lithium ferrites
Authors: Hyun Sung Wook , Kouh Taejoon , Kim Sam Jin , Kim Chul Sung
Published: February 2009

The effect of proton irradiation on magnetic properties of lithium ferrites has been investigated with x-ray diffraction (XRD), magnetization, and Mössbauer spectroscopy measurements. Li0.5Fe2.5O4 powders have been fabricated by the sol-gel method. Following the annealing at 700 °C, these samples have been proton irradiated with 1, 5, and 10 pC/μm2. The analysis of XRD patterns by Rietveld refinement method shows that these samples have ordered cubic spinel structures with space group of P4332. We have observed that the corresponding lattice constant a0 linearly increases from 8.3301 to 8.3314±0.0001 Å with increasing proton irradiation. Compared to nonirradiated sample, which has the saturation magnetization (Ms) of 66.4 emu/g and oxygen occupancy of 3.9980 at room temperature, the values of magnetization and oxygen occupancy at room temperature are 66.0, 62.6, and 60.8 emu/g and 3.9840, 3.9452, and 3.9272, respectively, for 1, 5, and 10 pC/μm2 irradiated powders. Also, the coercivity (Hc) decreases from 175.6 to 154.0 Oe with increasing proton irradiation. The Mössbauer spectra taken at room temperature show that the values of isomer shift (δ) for the tetrahedral (A) and octahedral (B) sites are consistent with the Fe3+ valence state. The results suggest that the proton irradiation induces the oxygen vacancy defects, which in turn leads to the changes in magnetic properties.
Hydrogen-bonded structures of pyrrole-solvent clusters: Infrared cavity ringdown spectroscopy and quantum chemical calculations
Authors: Matsumoto Yoshiteru , Honma Kenji
Published: February 2009

The hydrogen-bonded structures of pyrrole-solvent (H2O,CH3OH,C2H5OH) binary clusters were studied by the combination of experimental and theoretical techniques. Infrared cavity ringdown spectroscopy was applied to observe the NH and OH stretching vibrations of the clusters. The structures, binding energies, and normal modes of the binary clusters were obtained by quantum chemical calculations of the MP2/6-31+G(d,p) and B3LYP/6-311+G(d,p) levels. For the 1:1 clusters of pyrrole-H2O, pyrrole-CH3OH, and pyrrole-C2H5OH, the hydrogen-bonded NH stretching vibrations were observed at 3448, 3414, and 3408 cm−1, respectively. They were redshifted from the NH stretching vibration of the pyrrole monomer, and the amounts of the redshift were proportional to the proton affinities of the solvent molecules. MP2 level calculations revealed that the σ-type (NH⋯O) hydrogen-bonded structures had 7.6–9.0 kJ/mol larger binding energies than the π-type structures (OH⋯π electron cloud of pyrrole), and that the vibrational frequencies of the σ-type structures are consistent with the observed spectra. In addition to the 1:1 clusters, the NH or OH stretching vibrations of pyrrole-CH3OH binary clusters were observed at 3432 and 3549 cm−1. Among three optimized structures of the pyrrole-(CH3OH)2, the σ-π bridge pyrrole-(CH3OH)2 provided a reasonable agreement between the observed and calculated vibrational frequencies. For the pyrrole-H2O binary clusters, three new bands were observed at 3414, 3435, and 3541 cm−1. These bands are consistent with the calculated NH and OH stretching vibrations of the (pyrrole)2-H2O cluster, which has a closed cyclic hydrogen-bonded structure.
Quasichemical theory with a soft cutoff
Authors: Chempath Shaji , Pratt Lawrence R. , Paulaitis Michael E.
Published: February 2009

In view of the wide success of molecular quasichemical theory of liquids, this paper develops the soft-cutoff version of that theory. This development allows molecular dynamics simulations to be used for the calculation of solvation free energy, whereas the hard-cutoff version of the theory needs Monte Carlo simulations. This development also shows how fluids composed of molecules with smooth repulsive interactions can be treated analogously to the molecular-field theory of the hard-sphere fluid. In the treatment of liquid water, quasichemical theory with soft-cutoff conditioning does not change the fundamental convergence characteristics of the theory using hard-cutoff conditioning. In fact, hard cutoffs are found here to work better than softer ones in that case.
Self-oscillations in weakly coupled GaAs/AlGaAs superlattices at 77.3 K
Authors: Rasulova G. K. , Brunkov P. N. , Egorov A. Yu. , Zhukov A. E.
Published: February 2009

We report 77.3 K self-oscillations in a 30-period weakly coupled GaAs/Al0.3Ga0.7As (28/10 nm) superlattice (SL). A study of frequency spectra of self-oscillations under external sinusoidal force in frequency-locked regime at different fixed voltages showed that current oscillations detected in the structureless regions of the I-V characteristic of weakly coupled SLs are forced oscillations. It was established that oscillations of free oscillator arising when the voltage is fixed at the first negative differential conductivity region at the beginning of the plateaulike region in the I-V characteristic are forcing oscillations. It was also shown that in order to describe the mechanism of the current oscillations in weakly coupled SLs, the model of the current oscillations in resonant tunneling diodes can be successfully applied.
Reshocks, rarefactions, and the generalized Layzer model for hydrodynamic instabilities
Authors: Mikaelian Karnig O.
Published: February 2009

We report numerical simulations and analytic modeling of shock tube experiments on Rayleigh–Taylor and Richtmyer–Meshkov instabilities. We examine single interfaces of the type A/B where the incident shock is initiated in A and the transmitted shock proceeds into B. Examples are He/air and air/He. In addition, we study finite-thickness or double-interface A/B/A configurations such as air/SF6/air gas-curtain experiments. We first consider conventional shock tubes that have a “fixed” boundary: A solid endwall which reflects the transmitted shock and reshocks the interface(s). Then we focus on new experiments with a “free” boundary—a membrane disrupted mechanically or by the transmitted shock, sending back a rarefaction toward the interface(s). Complex acceleration histories are achieved, relevant for inertial confinement fusion implosions. We compare our simulation results with a generalized Layzer model for two fluids with time-dependent densities and derive a new freeze-out condition whereby accelerating and compressive forces cancel each other out. Except for the recently reported failures of the Layzer model, the generalized Layzer model and hydrocode simulations for reshocks and rarefactions agree well with each other and remain to be verified experimentally.
Methane activation by cobalt cluster cations, Con+ (n=2–16): Reaction mechanisms and thermochemistry of cluster-CHx (x=–3) complexes
Authors: Citir Murat , Liu Fuyi , Armentrout P. B.
Published: February 2009

The kinetic energy dependences of the reactions of Con+ (n=2–16) with CD4 are studied in a guided ion beam tandem mass spectrometer over the energy range of 0–10 eV. The main products are hydride formation, ConD+, dehydrogenation to form ConCD2+, and double dehydrogenation yielding ConC+. These primary products decompose to form secondary and higher order products, ConCD+, Con−1D+, Con−1C+, Con−1CD+, and Con−1CD2+ at higher energies. Adduct formation of ConCD4+ is also observed for the largest cluster cations, n≥10. In general, the efficiencies of the single and double dehydrogenation processes increase with cluster size, although the hexamer cation shows a reduced reactivity compared to its neighbors. All reactions exhibit thresholds, and cross sections for the various primary and secondary reactions are analyzed to yield reaction thresholds from which bond energies for cobalt cluster cations to D, C, CD, CD2, and CD3 are determined. The relative magnitudes of these bond energies are consistent with simple bond order considerations. Bond energies for larger clusters rapidly reach relatively constant values, which are used to estimate the chemisorption energies of the C, CD, CD2, and CD3 molecular fragments to cobalt surfaces.
Dielectric and electrical properties of amorphous La1−xTaxOy films as higher-k gate insulators
Authors: Zhao Yi , Kita Koji , Kyuno Kentaro , Toriumi Akira
Published: February 2009

In this study, we investigated the applicability of an amorphous, high-permittivity (k) dielectric film La1−xTaxOy as an alternative gate insulator in next-generation complementary metal-oxide-semiconductor devices and metal-insulator-metal capacitors. La1−xTaxOy films not only show a crystallization temperature higher than 1000 °C, but also a permittivity as high as 30. La1−xTaxOy films also have a much larger band gap than Ta2O5 films because of the coupling effect between the 5d orbitals of La and Ta atoms bonding to a common oxygen atom. Therefore, La1−xTaxOy films with appropriate Ta concentration are promising amorphous high-k gate insulators.
Modification of dispersion, localization, and attenuation of thin metal stripe symmetric surface plasmon-polariton modes by thin dielectric layers
Authors: Adato Ronen , Guo Junpeng
Published: February 2009

We systematically investigated the properties of the fundamental symmetric surface plasmon-polariton mode supported by a finite width gold microstripe with thin dielectric layers placed above and below it. This paper describes the dispersive behavior of the fundamental symmetric mode and the dependence of its attenuation and confinement on the thin dielectric layers’ thickness and refractive index. When the dielectric layers have a refractive index less than that of the cladding, the dispersion curve shifts toward the cladding light line and the mode attenuation is reduced with the tradeoff of reduced confinement. For dielectric layers with an index of refraction higher than that of the cladding, the dispersion curve shifts away from the cladding light line and the mode confinement is enhanced at the cost of increased attenuation. When designed properly, the higher refractive index dielectric layers in combination with the low index cladding can achieve tight mode confinement which cannot be obtained by using either a high or low index homogeneous dielectric cladding. The dependence of the mode’s properties on the thickness and width of the metal stripe and dielectric layers is also investigated.
Damage mechanisms in thin film solar cells during sputtering deposition of transparent conductive coatings
Authors: Fan Qi Hua , Deng Michael , Liao Xianbo , Deng Xunming
Published: February 2009

Amorphous silicon (a-Si) based thin film solar cell grown on flexible stainless steel substrate is one of the most promising energy conversion devices in the future. This type of solar cell uses a transparent conductive oxide (TCO) film as top electrode. It has been a widely accepted opinion that the radio frequency sputtering deposition of the TCO film produces a higher yield than direct current sputtering, and the reason is not clear. Here we show that the damage to the solar cell during the sputtering process is caused by a reverse bias applied to the n-i-p junction. This reverse bias is related to the characteristics of plasma discharge. The mechanism we reveal may significantly affect the solar cell process.
Dye degradation induced by hydrogen-terminated silicon nanowires under ultrasonic agitations
Authors: Chen Z. H. , Tang Y. B. , Liu Y. , Kang Z. H. , Zhang X. J. , Fan X. , Lee C. S. , Bello I. , Zhang W. J. , Lee S. T.
Published: February 2009

A method for degradation of environmentally hazardous dyes using silicon nanowires (SiNWs) has been developed. Environmentally unfriendly methyl red was degraded with assistance of H-terminated SiNWs under ultrasonic agitation. The hydrogenated surfaces of SiNWs are shown to be responsible for the surface reaction and decay of methyl red. The rate of degradation increases with the amount of SiNWs and agitation power. SiNWs after their application can be recycled and reactivated for further uses by a simple heating in hydrogen plasmas.
Blow-up profile to the solutions of two-coupled Schrödinger equations
Authors: Chen Jianqing , Guo Boling
Published: February 2009

The model of the following two-coupled Schrödinger equations, it+12Δu=(g11|u|2p+g|u|p−1|v|p+1)uu, (t,x)∊R+×RN, and ivt+12Δv=(g|u|p+1|v|p−1+g22|v|2p)v, (t,x)∊R+×RN, is proposed in the study of the Bose–Einstein condensates [Mitchell, et al., “Self-traping of partially spatially incoherent light,” Phys. Rev. Lett. 77, 490 (1996)]. We prove that for suitable initial data and p the solution blows up exactly like δ function. As a by-product, we prove that similar phenomenon occurs for the critical two-coupled Schrödinger equations with harmonic potential [Perez-Garcia, V. M. and Beitia, T. B., “Sybiotic solitons in heteronuclear multicomponent Bose-Einstein condensates,” Phys. Rev. A 72, 033620 (2005)], iut+12Δu=Ω2|x|2u+(g11|u|2p+g|u|p−1|v|p+1)u, x∊RN, and ivt+12Δv=Ω2|x|2v+(g|u|p+1|v|p−1+g22|v|2p)v, x∊RN.
Separation of topographic features from magnetic force images using capacitive coupling effect
Authors: Kim Byung I.
Published: February 2009

Separation of topographic features from magnetic images has been an issue for the past two decades in magnetic force microscopy (MFM). The frequent pickups of the topographic features are interpreted as transitions of the tip between bistable states of the tip-sample assembly in the noncontact and tapping regions. MFM using electrostatic force modulation demonstrates the separation of the topographic features from the magnetic images by removing the tapping state from the bistable states through the introduction of a capacitive coupling.
Experimental setup and realization of thin film specimens for microtensile tests
Authors: Malhaire Christophe , Seguineau Cédric , Ignat Michel , Josserond Charles , Debove Laurent , Brida Sebastiano , Desmarres Jean-Michel , Lafontan Xavier
Published: February 2009

This paper describes a microtensile test system and the design as the realization of the samples dedicated to the tensile experiments. Two different technologies for the development of miniaturized specimens are detailed: self-standing tensile samples sustained by silicon frames and metal on polymer specimens obtained by laser cutting. The design of the samples has been optimized by means of finite element simulations. Aluminum beams with very large length on thickness ratio have been released from their silicon substrate using a standard etching process. Stress/strain curves are derived from experimental force/displacement values and discussed in terms of Young’s modulus values and critical parameters (flow and rupture stresses).
Instabilities of a nonrelativistic electron beam in a magnetized waveguide partially filled with semiconductor
Authors: Rusanov A. F. , Yakovenko V. M.
Published: February 2009

The potential for developing new terahertz sources based on the interaction between a nonrelativistic electron beam and a semiconductor plasma is examined. The article presents a theoretical study of the beam-plasma interaction in a magnetized rectangular waveguide. Such an interaction gives rise to broad-band instabilities of the space-charge waves of the electron beam. The effects of the external magnetic field and the electron collision frequency on the growth rates of the unstable waves are studied and discussed.
Interfacial defects controlled electrical and magnetotransport in Co/ZnO nanocomposites
Authors: Hsu C. Y. , Huang J. C. A. , Lee Y. H. , Chen S. F. , Liu C. P. , Sun S. J. , Tzeng Yonhua
Published: February 2009

This work demonstrates, by frequency-dependent electrical measurements, significant variation associated with interfacial defects in Co/ZnO nanocomposites (NCs) for electrical and magnetic transport. Radio-frequency impedance measurements showed that heat treatment in an ultrahigh vacuum (UHV) increased interfacial defect density. Interfacial defects-assisted transport reduced the magnetoresistance (MR) ratio from 5.04% for the as-grown sample to 0.17% following heat treatment in UHV. The evolution of the onset frequency of power-law dispersion conductivity revealed that the increase in the interfacial defect density in Co/ZnO NCs upon heat treatment was consistent with the change in MR.
High-Q micromechanical resonators in a two-dimensional phononic crystal slab
Authors: Mohammadi Saeed , Eftekhar Ali Asghar , Hunt William D. , Adibi Ali
Published: February 2009

By creating line defects in the structure of a phononic crystal (PC) made by etching a hexagonal array of holes in a 15 μm thick slab of silicon, high-Q PC resonators are fabricated using a complimentary-metal-oxide-semiconductor-compatible process. The complete phononic band gap of the PC structure supports resonant modes with quality factors of more than 6000 at frequencies as high as 126 MHz. The confinement of acoustic energy is achieved by using only a few PC layers confining the cavity region. The calculated frequencies of resonance of the structure using finite element method are in a very good agreement with the experimental data. The performance of these PC resonator structures makes them excellent candidates for wireless communication and sensing applications.
Domain structure of (100)/(001)-oriented epitaxial PbTiO3 thick films with various volume fraction of (001) orientation grown by metal organic chemical vapor deposition
Authors: Utsugi Satoru , Fujisawa Takashi , Ikariyama Rikyu , Yasui Shintaro , Nakaki Hiroshi , Yamada Tomoaki , Ishikawa Mutsuo , Matsushima Masaaki , Morioka Hitoshi , Funakubo Hiroshi
Published: February 2009

(100)/(001)-oriented epitaxial PbTiO3 films thicker than 1 μm were grown on various types of substrates by chemical vapor deposition. The domain structures of these films with different volume fractions of (001) were investigated. Domain structures, consisting of (100)/(001)-oriented domains, were observed regardless of the type of substrate. However, the tilting angles of the a- and c-domains from the surface normal linearly changed with the volume fraction of the (001) orientation. These results suggest that the volume fraction of the (001) orientation is crucial in identifying the domain structure of PbTiO3 thick films.
Phase transitions and the temperature dependence of the dielectric properties in tetragonally strained barium strontium titanate films
Authors: Alldredge L. M. B. , Chang Wontae , Kirchoefer Steven W. , Pond Jeffrey M.
Published: February 2009

The dielectric properties of sputter-deposited Ba1−xSrxTiO3 (BST) thin films on (001) MgO substrates with in-plane or out-of-plane tetragonal lattice structure distortions were characterized as a function of temperature. A temperature-dependent interpolation calibration technique was developed for increased efficiency of the microwave measurements. The BST films showed significant differences in the ferroelectric phase transition due to lattice distortions with a strong temperature dependence of the in-plane dielectric behavior for films under tensile strain and a weak temperature dependence for films under compressive strain. The experimental data agreed well with theoretical modeling of the BST film strain effect based on Devonshire’s theory.
Broadband and omnidirectional antireflection from conductive indium-tin-oxide nanocolumns prepared by glancing-angle deposition with nitrogen
Authors: Chang C. H. , Yu Peichen , Yang C. S.
Published: February 2009

Characteristic formation of highly oriented indium-tin-oxide (ITO) nanocolumns is demonstrated using electron-beam evaporation with an obliquely incident nitrogen flux. The nanocolumn material exhibits broadband and omnidirectional antireflective characteristics up to an incidence angle of 70° for the 350–900 nm wavelength range for both s- and p-polarizations. Calculations based on a rigorous coupled-wave analysis indicate that the superior antireflection arises from the tapered column profiles which collectively function as a gradient-index layer. Since the nanocolumns have a preferential growth direction which follows the incident vapor flux, the azimuthal and polarization dependence of reflectivities are also investigated. The single ITO nanocolumn layer can function as antireflection contacts for light emitting diodes and solar cells.

At the request of the authors and editor, this article is being retracted effective 1 July 2014.
Local thermal bistability in MgB2 microwave coplanar resonators: Opposite jumpwise response to weak-link switching and to vortex avalanches
Authors: Ghigo G. , Gerbaldo R. , Gozzelino L. , Laviano F. , Lopardo G. , Monticone E. , Portesi C. , Mezzetti E.
Published: February 2009

We report on specific nonlinear features in the response of microwave coplanar resonators obtained from magnesium diboride thin films. Different jumpwise behaviors observed in the resonance curves are found to be generated by either weak-link switching or vortex avalanches. Both mechanisms can be explained in terms of local-heating-induced thermal bistability, but they result in opposite effects, i.e., opposite signs in the abrupt variations of the quality factor and of the resonance frequency, due to the rf-current distribution. The weak-link-switching response shows promising characteristics (jumpwise signal, bistability, and hysteresis) for applications of MgB2 films in nonlinear devices.
Dual nonlinear dielectric resonance and strong natural resonance in Ni/ZnO nanocapsules
Authors: Liu X. G. , Jiang J. J. , Geng D. Y. , Li B. Q. , Han Z. , Liu W. , Zhang Z. D.
Published: February 2009

The electromagnetic characteristics of Ni/ZnO nanocapsules were studied at 2–18 GHz. The dual nonlinear dielectric resonance and strong natural resonance at 16.6 GHz contribute to excellent electromagnetic absorption. A reflection loss (RL) exceeding −20 dB was calculated in 14–18 GHz for an absorber thickness of 2.05 mm, and RL exceeds −10 dB in the whole X-band (10–12.4 GHz) and the whole Ku-band (12.4–18 GHz) for a thickness of 2.50 mm. The equivalent circuit model was used to explain the dual nonlinear dielectric resonance, which is ascribed to a cooperative consequence of the core/shell interfaces and the dielectric ZnO shells.
Anisotropic transport in quantum waveguides due to the spin-orbit interactions
Authors: Wang Miao , Chang Kai , Chan K. S.
Published: February 2009

We theoretically investigate the charge transport in the quantum waveguides in the presence of the Rashba spin-orbit interaction and the Dresselhaus spin-orbit interaction. We find that the interplay between the Rashba spin-orbit interaction and Dresselhaus spin-orbit interaction can induce a symmetry breaking and consequently leads to the anisotropic charge transport in the quantum waveguides, the conductance through the quantum waveguides depends sensitively on the crystallographic orientations of the quantum waveguides. The anisotropy of the charge transport can even survive in the presence of disorder effect in realistic systems.
Junctionless multigate field-effect transistor
Authors: Lee Chi-Woo , Afzalian Aryan , Akhavan Nima Dehdashti , Yan Ran , Ferain Isabelle , Colinge Jean-Pierre
Published: February 2009

This paper describes a metal-oxide-semiconductor (MOS) transistor concept in which there are no junctions. The channel doping is equal in concentration and type to the source and drain extension doping. The proposed device is a thin and narrow multigate field-effect transistor, which can be fully depleted and turned off by the gate. Since this device has no junctions, it has simpler fabrication process, less variability, and better electrical properties than classical MOS devices with source and drain PN junctions.
A comparative study of effects of SiNx deposition method on AlGaN/GaN heterostructure field-effect transistors
Authors: Higashiwaki Masataka , Chen Zhen , Chu Rongming , Pei Yi , Keller Stacia , Mishra Umesh K. , Hirose Nobumitsu , Matsui Toshiaki , Mimura Takashi
Published: February 2009

The effects of thin SiNx deposition on AlGaN/GaN heterostructure field-effect transistors were systematically studied by comparing their electrical and device characteristics. Two aspects of the thin SiNx film deposition were investigated: (i) the increase in two-dimensional electron gas (2DEG) density at the heterointerface and (ii) its capability as a gate insulating layer. Three different SiNx deposition methods were studied: catalytic chemical vapor deposition (Cat-CVD), metalorganic chemical vapor deposition (MOCVD), and plasma enhanced chemical vapor deposition (PECVD). A large increase in 2DEG density was obtained after SiNx deposition for all methods. The devices with MOCVD SiNx gate insulator showed a larger gate leakage current than those with the Cat-CVD and PECVD SiNx, implying that a thinning of the AlGaN surface barrier occurred due to Si diffusion into the AlGaN barrier during the high-temperature MOCVD process.
Corrected Article: “Self-organized periodic domain structure for second harmonic generations in ferroelastic β′-(Sm,Gd)2(MoO4)3 crystal lines on glass surfaces” [Appl. Phys. Lett. 94, 041915 (2009)]
Authors: Tsukada Yuta , Honma Tsuyoshi , Komatsu Takayuki
Published: February 2009

Ferroelastic β′-(Sm,Gd)2(MoO4)3 (SGMO) crystal lines are patterned on the surface of Sm2O3–Gd2O3–MoO3–B2O3 glasses by continuous wave Yb:YVO4 laser irradiations (wavelength is 1080 nm, power is 1.2 W and scanning speed is 5 μm/s). Crystal lines show self-organized periodic domain structures with periodic refractive index changes. The intensity of second harmonic (SH) waves changes periodically depending on the domain structure. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of SH intensities that the orientation of (MoO4)2− tetrahedra in SGMO crystals changes gradually and periodically along the crystal line growth direction due to the spontaneous strains in SGMO crystals.
Movement and the Rubber Hand Illusion
Authors: Dummer Timothy , Picot-Annand Alexandra , Neal Tristan , Moore Chris
Published: February 2009

When a participant views a rubber hand being stroked by a paintbrush while his/her real hand is unseen and similarly stroked by another paintbrush, a misperception known as the rubber hand illusion occurs whereby tactile sensations are falsely referred to the non-body part. The purpose of the current study was to further examine the rubber hand illusion with conditions of movement. An apparatus was devised that would synchronise visual with felt movement in an active condition and a passive condition. An asynchronous condition was included as a control in which visual and felt movement were purposely disconnected. The three movement conditions (active, passive, and asynchronous) were statistically compared in order to assess our prediction that synchronous conditions of movement (especially active) would generate more reports of the illusion. The performance of the movement conditions was evaluated against a visual-tactile condition, which is a known contributor to the rubber hand illusion. Not only significantly more robust reports of the illusion were obtained when visual movement and felt movement were synchronised but there was also a trend toward stronger reports in the active condition rather than the passive condition. Interestingly, the pattern of results differed according to the particular question on the self-report.
Spatial Spread of Interocular Suppression is Guided by Stimulus Configuration
Authors: Maruya Kazushi , Blake Randolph
Published: February 2009

When the two eyes view dissimilar monocular stimuli, the resulting interocular suppression can spread beyond the region of explicit stimulus conflict: portions of one rival target will disappear even though there is no competing stimulation at the corresponding location in the other eye's view. In a series of experiments we examined whether this spread of suppression is spatially isotropic or governed by the configuration of the stimulus a portion of which is subject to suppression. Observers reported the incidence of stimulus disappearance at different locations along or nearby the contours of a large figure, part of which was suppressed by presentation of a continuous flash-suppression stimulus to a restricted region of the other eye. For all observers, suppression spread over several degrees along the contours of the figure, but tended not to spread to locations nearby but disconnected from the figure. Suppression spread effectively over a smoothly curved contour, and it spread around a sharp corner defined by two abutting contours, albeit less effectively. Suppression tended not to spread to features within the interior of a figure (a face), even if those features formed an integral part of the figure. A gap within a spatially extended stimulus arrested the spread of suppression, unless that gap appeared to arise from occlusion. Spread of suppression was unrelated to sensory eye dominance and was found with a more conventional binocular rivalry configuration, too. These findings implicate the involvement of neural circuitry in which inhibition propagates along paths of excitation beyond spatial regions of explicit interocular conflict.