bluuebunny/crossref_metadata_2025 huggingface dataset:
Tidally induced turbulence and suspended sediment
Authors: Souza Alejandro J. , Alvarez Luis G. , Dickey Tommy D.
Published: October 2004

Nearly continuous data collected using novel methods are utilized to advance the understanding of turbulence and suspended particulate matter (SPM) dynamics under strong tidal flow conditions. Key instrumentation includes a single acoustic current profiler that provides nearly continuous, concurrent turbulence and SPM information with respect to depth near the seafloor and within the water column. Observations show a lag of about 1 hour in turbulence production between the bottom and 12 meters above the bottom (mab), and of about 1.5 hours for SPM. Estimates of eddy viscosity show values ranging between 10−3 and 10−2 m2 s−1, with an almost constant mean value of 3.5 × 10−3 m2 s−1 within the bottom 7 meters. The present observations and a previously reported theory show good agreement in both amplitude and phase for SPM and turbulence, when values of eddy viscosity ranging between 3.5 × 10−3 (mean) and 10−2 (maximum) are used. Our data set is valuable for evaluating, developing, and improving turbulence and SPM numerical models.
Walén and slow‐mode shock analyses in the near‐Earth magnetotail in connection with a substorm onset on 27 August 2001
Authors: Eriksson S. , Øieroset M. , Baker D. N. , Mouikis C. , Vaivads A. , Dunlop M. W. , Rème H. , Ergun R. E. , Balogh A.
Published: October 2004

We have examined Cluster spacecraft 1 (C1) magnetic field and particle observations from 27 August 2001 when the Cluster spacecraft separation was less than 0.27 RE and the spacecraft were located near the equatorial plane of the postmidnight magnetotail at xGSM ∼ −19 RE and yGSM ∼ −2.1 RE. A detailed examination of observations recorded between 0350 UT and 0435 UT is performed with special emphasis on the plasma flow reversal from strong tailward flows to earthward flows in the approximate time interval 0400 UT to 0410 UT. Evidence for the expansion phase onset of an isolated substorm between ∼0406 UT and ∼0408 UT was reported by Baker et al. [2002]. During the 0400–0410 UT interval, C1 was located in the plasma sheet where the observed plasma density N ∼ 0.3 cm−3 and the plasma ion β ∼ 1.5. The Walén analysis applied to the tailward flow interval from 0400:36 UT to 0403:14 UT is consistent with the ions being accelerated to ∼73% of the Alfvén speed across a slow‐mode shock connected to a near‐Earth neutral line located on the earthward side of the spacecraft. The occurrence of a small plasmoid‐type magnetic flux rope during the leading edge of the tailward flows provides further support in favor of an active region of magnetic reconnection earthward of Cluster. The more field‐aligned earthward flows between 0406 UT and 0408 UT, however, failed to satisfy the Walén test. Rankine‐Hugoniot analyses of upstream and downstream plasma and magnetic field parameters confirm the presence of a slow‐mode shock in connection with the passage of the tailward flow region but not with the 0406 UT to 0408 UT earthward flow interval. The confirmed shock satisfies the critical slow‐mode requirements: MI* ≤ 1.0 and MSM* > 1.0 on the upstream side and MSM* < 1.0 on the downstream side. Here, MI* and MSM* are the intermediate Alfvén speed and slow‐mode phase speed Mach numbers in the frame of the shock. The failure of both the Walén test and the Rankine‐Hugoniot analysis on the earthward flow portion of the plasma reversal event may be associated with the strong earthward ∇B of the inner magnetosphere. The successful joint Walén and slow shock analyses on the tailward flows within the plasma sheet present further evidence in favor of Petschek‐type reconnection at distances xGSM > −19 RE of the near‐Earth magnetotail.
Electric fields in a sheath near a metal–dielectric interface
Authors: Barnat E. V. , Hebner G. A.
Published: October 2004

Spatially resolved electric fields in the sheath region near a metal–dielectric junction were measured in a radio-frequency-driven argon plasma. The fields were determined by observing the Stark shifted transitions to the 13d[3∕2]1 Rydberg state by laser-induced fluorescence-dip spectroscopy. Calibration of the Stark shifts for the 13d[3∕2]1 Rydberg state were experimentally obtained in a separate apparatus. Maps of the electric fields illustrate that the structure of the sheath formed around the junction depended on both the surface material and on the configuration of the surface.
Addendum: Symmetries of the energy-momentum tensor
Authors: Sharif M.
Published: October 2004

In recent papers [J. Math. Phys. 44, 5142 (2003); 45, 1518 (2003); 45, 1532 (2004)] we have discussed matter symmetries of nonstatic spherically symmetric space–times, static plane symmetric space–times, and cylindrically symmetric static space–times. These have been classified for both cases when the energy-momentum tensor is nondegenerate and also when it is degenerate. Here we add up some consequences and the missing references about the Ricci tensor.
A strong magnetoelectric voltage gain effect in magnetostrictive-piezoelectric composite
Authors: Dong Shuxiang , Li J. F. , Viehland D. , Cheng J. , Cross L. E.
Published: October 2004

A magnetoelectric laminate composite consisting of magnetostrictive Terfenol-D (Tb1–xDyxFe2–y) and piezoelectric Pb(Zr,Ti)O3 layers has an extremely high voltage gain effect of ≈300 at its resonant state, offering potential for high-voltage miniature transformer applications.
Effect of nitride passivation on the visible photoluminescence from Si-nanocrystals
Authors: Yang Moon-Seung , Cho Kwan-Sik , Jhe Ji-Hong , Seo Se-Young , Shin Jung H. , Kim Kyung Joong , Moon Dae Won
Published: October 2004

The effect of nitride passivation on the visible photoluminescence from nanocrystal Si (nc-Si) is investigated. Silicon-rich silicon nitride (SRSN) and silicon-rich silicon oxide (SRSO), which consist of nc-Si embedded in silicon nitride and silicon oxide, respectively, were prepared by reactive ultrahigh vacuum ion beam sputter deposition followed by a high temperature anneal. Both SRSN and SRSO display photoluminescence peaks after high temperature annealing, coincident with the formation of Si nanocrystals, and similar changes in the peak luminescence position with the excess Si content. However, the luminescence peak positions from SRSN are blueshifted by about 0.6eV over that of comparable SRSO such that its luminescence peaks in the visible range. The results demonstrate that control of the surface passivation is critical in controlling the nc-Si luminescence, and indicate the possibility of using nitride-passivated nc-Si for visible luminescence applications including white luminescence.
An algorithm for quaternionic linear equations in quaternionic quantum theory
Authors: Jiang Tongsong
Published: October 2004

By means of complex representation and companion vector, in this paper we introduce a definition of rank of a quaternion matrix, study the problems of quaternionic linear equations, and obtain an algorithm for quaternionic linear equations in quaternionic quantum theory.
Intersecting hypersurfaces in dimensionally continued topological density gravitation
Authors: Gravanis Elias , Willison Steven
Published: October 2004

We consider intersecting hypersurfaces in curved spacetime with gravity governed by a class of actions which are topological invariants in lower dimensionality. Along with the Chern–Simons boundary terms there is a sequence of intersection terms that should be added in the action functional for a well defined variational principle. We construct them in the case of Characteristic Classes, obtaining relations which have a general topological meaning. Applying them on a manifold with a discontinuous connection 1-form we obtain the gravity action functional of the system and show that the junction conditions can be found in a simple algebraic way. At the sequence of intersections there are localized independent energy tensors, constrained only by energy conservation. We work out explicitly the simplest nontrivial case.
Recovering the M-channel Sturm-Liouville operator from M+1 spectra
Authors: Chabanov V. M.
Published: October 2004

For a system of M coupled Schrödinger equations, the relationship is found between the vector-valued norming constants and M+1 spectra corresponding to the same potential matrix but different boundary conditions. Under a special choice of particular boundary conditions, this equation for norming vectors has a unique solution. The double set of norming vectors and associated spectrum of one of the M+1 boundary value problems uniquely specifies the matrix of potentials in the multichannel Schrödinger equation.
Spontaneous polarization change with Zr∕(Zr+Ti) ratios in perfectly polar-axis-orientated epitaxial tetragonal Pb(Zr,Ti)O3 films
Authors: Morioka Hitoshi , Yokoyama Shintaro , Oikawa Takahiro , Funakubo Hiroshi , Saito Keisuke
Published: October 2004

Epitaxial Pb(Zr,Ti)O3 (PZT) films 50 and 250nm thick with the Zr∕(Zr+Ti) ratio from 0.13 to 0.65 were grown on (100)cSrRuO3∕∕(100)SrTiO3 substrates at 540°C by pulsed-metalorganic chemical vapor deposition. The crystal orientation, lattice parameter, axial angle, and relative volume fraction of constituent domains were determined by high-resolution x-ray diffraction reciprocal space mapping. We grew (100) and∕or (001)-oriented epitaxial PZT films for the whole Zr∕(Zr+Ti) ratio. A tetragonal single phase was obtained for the Zr∕(Zr+Ti) ratio ranging from 0.13 to 0.54 and 0.19 to 0.45 with the 50 and 250nm thick films, respectively, while mixed phases of a tetragonal and rhombohedral from 0.45 to 0.60 for the 250nm thick films was obtained. For the films consisting of a tetragonal single phase, lattice parameters of a- and c-axes and their ratio (c∕a) were almost the same as the reported data for the PZT powder, suggesting a small amount of residual strain in them. In addition, perfectly polar-axis (c-axis)-oriented tetragonal films were obtained for the 50nm thick films, while an ∼70% c-axis-orientation for the 250nm thick ones was obtained. Polarization–electric-field hysteresis loops with a good square shape were observed for all films. Also, spontaneous polarization (Ps) values that were directly measured for the 50nm thick films and estimated for the 250nm thick films taking into account the volume fraction of the polar-axis-orientated domain were closely in line with the Zr∕(Zr+Ti) ratio, and they decreased as the ratio increased. The square of the estimated Ps was found to be proportional to the crystal distortion, c∕a−1. These results are essential not only for understanding the origin of the large Ps of PZT but for the property design of the ferroelectric devices using PZT.
Slowly varying envelope kinetic simulations of pulse amplification by Raman backscattering
Authors: Sup Hur Min , Penn Gregory , Wurtele Jonathan S. , Lindberg Ryan
Published: October 2004

A numerical code based on an eikonal formalism has been developed to simulate laser-plasma interactions, specifically Raman backscatter (RBS). In this code, the dominant laser modes are described by their wave envelopes, avoiding the need to resolve the laser frequency; appropriately time-averaged equations describe particle motion. The code is fully kinetic, and thus includes critical physics such as particle trapping and Landau damping which are beyond the scope of the commonly used fluid three-wave equations. The dominant forces on the particles are included: the ponderomotive force resulting from the beat wave of the forward and backscattered laser fields and the self-consistent plasma electric field. The code agrees well, in the appropriate regimes, with the results from three-wave equations and particle-in-cell simulations. The effects of plasma temperature on RBS amplification are studied. It is found that increasing the plasma temperature results in modification to particle trapping and the saturation of RBS, even before the onset of Landau damping of the plasma wave. This results in a reduction in the coupling efficiency compared to predictions based on the three-wave equations.
Driven reconnection about a magnetic X point in weakly collisional plasmas
Authors: Delzanno G. L. , Fable E. , Porcelli F.
Published: October 2004

The effect of the Hall term in the process of forced magnetic reconnection for an X point magnetic field configuration, both in the collisionless limit and in the case of weak resistive dissipation, is investigated in this paper. In the case of no guide field, a two-fluid (four fields) linearized model is derived and solved as a forced initial-value problem, resulting in an unexpected insensitivity of the reconnective rates (either asymptotic or peaked) upon the ion skin depth di which characterizes the Hall term. This result is obtained by imposing the axial current density and magnetic field perturbations to vanish at the boundary of the system. In the collisionless limit, the influence of the Hall term resides in the spatial configuration of the fields, which presents an interesting phase-mixing dynamics with three nested layers of width of the order of de2/di, de, and di, with de being the electron skin depth. The first scale length arises due to the coupling between axial and perpendicular motion and is characterized by high frequency oscillations superimposed on a low-frequency carrier. In the weakly collisional limit, resistivity smooths out the high frequency oscillations typical of the innermost layer.
Performance improvement conditions and their physical origin in the pulsed poloidal current drive regime of the reversed-field pinch device TPE-RX
Authors: Frassinetti L. , Yagi Y. , Koguchi H. , Shimada T. , Hirano Y.
Published: October 2004

The application of the pulsed poloidal current drive (PPCD) technique in reversed-field pinch (RFP) devices leads to the improvement of the confinement properties of the plasma. In this article the conditions necessary to achieve high PPCD performance in the TPE-RX [Y. Yagi, S. Sekine, H. Sakakita et al., Fus. Eng. Des. 45, 409 (1999)] RFP device will be shown. One of the key parameters is the component of the electric field parallel to the magnetic field E∥. The positive trend between E∥ and the PPCD performance can be explained in terms of reduction of magnetic fluctuations. It will also be shown that important roles are played by the triggering time of the PPCD pulses, the filling pressure of the deuterium gas, and the wall condition.
Error syndrome calculation for graph codes on a one-way quantum computer: Towards a quantum memory
Authors: Schlingemann Dirk-M.
Published: October 2004

For realizing a quantum memory the encoded quantum information can be protected against decoherence via repeated decoding and re-encoding operations. This requires us to perform fast encoding and decoding operations. The computational model underlying the one-way quantum computer provides a suitable concept for a fast implementation, which has been solved in a previous article for the encoding operation. In the present paper we show that the missing part, the decoding operation, can also be realized on a one-way quantum computer. This is based on the graph code representation for stabilizer codes, on the one hand, and the relation between cluster states and graph codes, on the other hand.
Approximation of sums of oscillating summands in certain physical problems
Authors: Karatsuba Ekatherina A.
Published: October 2004

The motion of a one-dimensional harmonic oscillator caused by recurring pushes in the absence of friction is considered. In particular, two cases are studied: the case when the pushes become more frequent and the other one when the pushes become less frequent. By means of an application of the Hardy–Littlewood–Vinogradov–Van der Corput theorem on the approximation of exponential sums by shorter ones, new asymptotic formulas for the solution of the problem are obtained.
Phenomenological theory of laser-plasma interaction in “bubble” regime
Authors: Kostyukov I. , Pukhov A. , Kiselev S.
Published: October 2004

The electron trapping in the “bubble” regime of laser-plasma interaction as proposed by Pukhov and Meyer-ter-Vehn [A. Pukhov and J. Meyer-ter-Vehn, Appl. Phys. B 74, 355 (2002)] is studied. In this regime the laser pulse generates a solitary plasma electron cavity: the bubble. It is free from the cold plasma electrons and runs with nearly light velocity. The present work discusses the form of the bubble and the spatial distribution of electromagnetic fields within the cavity. We extend the one-dimensional electron capture theory to the three-dimensional case. It is shown that the bubble can trap plasma electrons. The trapping condition is derived and the trapping cross section is estimated. Electron motion in the self-generated electron bunch is investigated. Estimates for the maximum of electron bunch energy and the bunch density are provided.
The Hall instability of unsteady inhomogeneous axially symmetric magnetized plasmas
Authors: Shtemler Yuri M. , Mond Michael , Liverts Edward
Published: October 2004

The Hall instability in cylindrically symmetric resistive magnetized plasmas in vacuum is investigated. The unperturbed self-similar equilibrium solutions for imploding Z-pinches with time-dependent total current It∼tS,S>1/3, are subjected by short-wave sausage perturbations. The instability criterion is derived in slow-time, frozen-radius approximation. In cylindrically symmetric configurations the instability is driven by the magnetic field curvature. The near-axis and near-edge branches of the neutral curve in the plane of the inverse Hall parameter and phase velocity with the frozen radial coordinate as a parameter are separated by the critical point, where the modified gradient from the unperturbed number density changes sign. The critical radius may be treated as a new characteristic size of the Z-pinch that emerges due to the instability: the pinch is envisaged restructured by the short-scale high-frequency Hall instability, in which a central stable core is surrounded by an outer shell. Such a modified equilibrium may explain the observed enhanced stability against magnetohydrodynamic modes.
Quantitative force measurements in liquid using frequency modulation atomic force microscopy
Authors: Uchihashi Takayuki , Higgins Michael J. , Yasuda Satoshi , Jarvis Suzanne P. , Akita Seiji , Nakayama Yoshikazu , Sader John E.
Published: October 2004

The measurement of short-range forces with the atomic force microscope (AFM) typically requires implementation of dynamic techniques to maintain sensitivity and stability. While frequency modulation atomic force microscopy (FM-AFM) is used widely for high-resolution imaging and quantitative force measurements in vacuum, quantitative force measurements using FM-AFM in liquids have proven elusive. Here we demonstrate that the formalism derived for operation in vacuum can also be used in liquids, provided certain modifications are implemented. To facilitate comparison with previous measurements taken using surface forces apparatus, we choose a model system (octamethylcyclotetrasiloxane) that is known to exhibit short-ranged structural ordering when confined between two surfaces. Force measurements obtained are found to be in excellent agreement with previously reported results. This study therefore establishes FM-AFM as a powerful tool for the quantitative measurement of forces in liquid.
Reach-through band bending in semiconductor thin films
Authors: Roussillon Y. , Giolando D. M. , Karpov V. G. , Shvydka Diana , Compaan A. D.
Published: October 2004

We describe a phenomenon of reach-through band bending in thin film semiconductors. It occurs through generation of defects that change the semiconductor work function. This translates the effect of the metal presence through the semiconductor film and induces a Schottky barrier in another semiconductor tangent to the film on the opposite side (reach-through band bending). We have found experimental evidence of this effect in CdTe photovoltaics.
Effect of initial conditions on two-dimensional Rayleigh–Taylor instability and transition to turbulence in planar blast-wave-driven systems
Authors: Miles A. R. , Edwards M. J. , Greenough J. A.
Published: October 2004

Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh–Taylor, Richtmyer–Meshkov, and decompression effects. In this paper, the results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility [E. M. Campbell, Laser Part. Beams 9, 209 (1991)] are presented. Using the multiphysics, adaptive mesh refinement, higher order Godunov Eulerian hydrocode, Raptor [L. H. Howell and J. A. Greenough, J. Comput. Phys. 184, 53 (2003)], the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types is considered. Compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Certain aspects of the initial conditions, including the rms amplitude, are shown to have a strong effect on the time to transition to the quasi-self-similar regime.
Energetic ion transport and concomitant change of the fusion reactivity during reconnection events in spherical tori
Authors: Kolesnichenko Ya. I. , Lutsenko V. V. , White R. B. , Yakovenko Yu. V.
Published: October 2004

Effects of MHD (magnetohydrodynamic) reconnection events on the beam-plasma fusion reactivity and transport of the beam ions are studied. Based on the analysis of fusion reactivity changes induced by MHD events, the conclusion is drawn that the strong drops of the neutron yield during sawtooth crashes observed in the national spherical torus experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] are associated with both a particle redistribution inside the plasma and a loss of the beam ions. Mechanisms of the energetic ion transport during sawtooth crashes are analyzed, in particular, with the use of the resonance adiabatic invariant derived in this paper. A numerical simulation of the particle motion during a sawtooth crash in NSTX is done with the code OFSEF (orbit following in the sawtooth electromagnetic field) [Ya. I. Kolesnichenko et al., Nucl. Fusion 40, 1325 (2000)] extended for a better description of the particle precession. It is shown that the motion of toroidally passing particles in NSTX can become stochastic under the influence of a crash. This stochasticity, as well as the motion along the resonance island, leads to the escape of some particles from the plasma.
Graphitic features on SiC surface following oxidation and etching using surface enhanced Raman spectroscopy
Authors: Lu Weijie , Feldman L. C. , Song Y. , Dhar S. , Collins W. E. , Mitchel W. C. , Williams J. R.
Published: October 2004

Graphitic features are detected on 4H-SiC surface following oxidation and etching using surface enhanced Raman spectroscopy (SERS). The electronic state of the carbon is sp2 on both the Si- and C-faces of 4H-SiC. The structures of the “carbon clusters” consist of two-dimensional graphitic flakes less than 2 nm and one-dimensional polyenes. The degree of graphitization on the C-face SiC is higher than those on the Si-face SiC. This study provides experimental evidence for “carbon clusters” existing on SiC surfaces following oxidation at atmospheric pressure and demonstrates that SERS is an effective technique to probe low concentration species on the SiC surface.
Spin-dependent boundary resistance in the lateral spin-valve structure
Authors: Kimura T. , Hamrle J. , Otani Y. , Tsukagoshi K. , Aoyagi Y.
Published: October 2004

We report the detection of clear spin-valve signal without any spurious magnetoresistive signal in a lateral spin-valve structure consisting of Cu∕Ni−Fe ohmic junction using local current injection. The obtained spin-valve signal is much larger than that of the nonlocal spin-valve configuration because of the efficient spin accumulation. The local current injection experiments with different probe configurations proved that the spin-valve signal is caused by the spin-dependent boundary resistance at the interface between the ferromagnetic voltage probe and the spin-polarized nonmagnetic wire.
Direct observation and analysis of nanoscale precipitates in (Sm,Eu,Gd)Ba2Cu3Oy
Authors: Muralidhar M. , Sakai N. , Jirsa M. , Koshizuka N. , Murakami M.
Published: October 2004

We employed atomic-resolution high-angle annular dark-field scanning transmission electron microscope to characterize the chemical composition and nature of the nanoparticles dispersed in melt-processed (Sm0.33Eu0.33Gd0.33)Ba2Cu3Oy superconductor. We found two types of stable nanometer-scale particles, small LRE-Ba2CuZrOy and (LRE,Zr)BaCuOy(LRE=Sm,Eu,Gd) ones, in the 10–60nm range, and larger particles of Gd2BaCuO5 “Gd-211,” around 100nm in size. A substantial increase of critical current density was observed up to 90K. Experimental data were interpreted in terms of additive pinning by “large” defects and a point-like disorder. The nanosized particles open a new horizon for production of bulk high-Tc superconducting magnets.
Covariants, joint invariants and the problem of equivalence in the invariant theory of Killing tensors defined in pseudo-Riemannian spaces of constant curvature
Authors: Smirnov Roman G. , Yue Jin
Published: October 2004

The invariant theory of Killing tensors (ITKT) is extended by introducing the new concepts of covariants and joint invariants of (product) vector spaces of Killing tensors defined in pseudo-Riemannian spaces of constant curvature. The covariants are employed to solve the problem of classification of the orthogonal coordinate webs generated by nontrivial Killing tensors of valence two defined in the Euclidean and Minkowski planes. Illustrative examples are provided.
Optical properties of single InAs quantum dots in close proximity to surfaces
Authors: Wang C. F. , Badolato A. , Wilson-Rae I. , Petroff P. M. , Hu E. , Urayama J. , Imamoğlu A.
Published: October 2004

The optical properties of single InAs∕GaAs quantum dots (QDs) were studied as a function of their distance from the air∕GaAs interface. A short-period superlattice structure allows us to controllably shorten the distance between the QDs and the surface in 6-nm steps. The QD luminescence intensity and lifetime measurements show that quantum tunneling effect results in a sharp reduction in fluorescence efficiency and lifetime when the wetting-layer–surface distance is within 9 nm. For distances between 15 and 40 nm, broadening of the photoluminescence linewidths of single QDs was observed. Since exciton recombination time and efficiency are in this case unchanged with respect to bulk QDs, the observed line broadening is most likely due to dephasing or spectral diffusion processes.
Two-dimensional Riemannian and Lorentzian geometries from second-order ODE’s
Authors: Gallo Emanuel
Published: October 2004

In this paper we give an alternative geometrical derivation of the results recently presented by García-Godínez, Newman, and Silva-Ortigoza on the class of all two-dimensional Riemannian and Lorentzian metrics from second-order ODE’s which are in duality with the two-dimensional Hamilton–Jacobi equation. We show that, as it happens in the null surface formulation of general relativity, the Wünschmann-type condition can be obtained as a requirement of a vanishing torsion tensor. Furthermore, from these second-order ODE's we obtain the associated Cartan connections.
Stretchability of thin metal films on elastomer substrates
Authors: Li Teng , Huang Zhenyu , Suo Z. , Lacour Stéphanie P. , Wagner Sigurd
Published: October 2004

Many flexible electronic surfaces comprise inorganic films on organic substrates. Mechanical failure of such integrated structures of stiff and compliant materials poses a significant challenge. This letter studies the stretchability of metal films on elastomer substrates. Our experiment shows that, when stretched, elastomer-supported metal films rupture at strains larger than those reported for freestanding films. We use a finite element code to simulate the rupture process of metal films. A freestanding metal film ruptures by forming a single neck. By contrast, a metal film on an elastomer substrate may develop an array of necks before rupture. While the pre-rupture necks do not change the electrical conductance appreciably, they elongate the metal film, leading to a large overall rupture strain.
Generation and propagation of surface plasmons in periodic metallic structures
Authors: Torosyan G. , Rau C. , Pradarutti B. , Beigang R.
Published: October 2004

The generation and propagation of surface plasmon polaritons in periodic metallic structures using femtosecond terahertz pulses is reported. The transmission and emission properties clearly show the influence of Wood’s anomalies. The velocity of propagation is determined experimentally and is in good agreement with a simple model.
The application of convolution-based statistical model on the electrical breakdown time delay distributions in neon
Authors: Maluckov Čedomir A. , Karamarković Jugoslav P. , Radović Miodrag K. , Pejović Momčilo M.
Published: October 2004

The convolution-based model of the electrical breakdown time delay distribution is applied for statistical analysis of experimental results obtained in neon-filled diode tube at 6.5 mbar. At first, the numerical breakdown time delay density distributions are obtained by stochastic modeling as the sum of two independent random variables, the electrical breakdown statistical time delay with exponential, and discharge formative time with Gaussian distribution. Then, the single characteristic breakdown time delay distribution is obtained as the convolution of these two random variables with previously determined parameters. These distributions show good correspondence with the experimental distributions, obtained on the basis of 1000 successive and independent measurements. The shape of distributions is investigated, and corresponding skewness and kurtosis are plotted, in order to follow the transition from Gaussian to exponential distribution.
Almost sharp quantum effects
Authors: Arias Alvaro , Gudder Stan
Published: October 2004

Quantum effects are represented by operators on a Hilbert space satisfying 0⩽A⩽I, and sharp quantum effects are represented by projection operators. We say that an effect A is almost sharp if A=PQP for projections P and Q. We give simple characterizations of almost sharp effects. We also characterize effects that can be written as longer products of projections. For generality we first work in the formalism of von Neumann algebras. We then specialize to the full operator algebra B(H) and to finite dimensional Hilbert spaces.
Experimental evidence of redistribution of fields during processing in a high-power microwave cavity
Authors: Dube D. C. , Ramesh P. D. , Cheng J. , Lanagan M. T. , Agrawal D. , Roy R.
Published: October 2004

A sensing probe has been introduced to profile the magnetic fields in a 2.45GHz, high-power single-mode microwave cavity. The treatment of a ferrite sample inside the cavity has established that, during the heating process, there is an unusual concentration of a magnetic field around the sample. During field heating, intense magnetic fields have been monitored, and are analogous to the redistribution of an electric field reported by Riedel and Svoboda [Proceedings of the Eighth Ampere Conference and Microwave Heating (2001)] in their simulation studies on microwave sintering.
Field-effect transistors with LaAlO3 and LaAlOxNy gate dielectrics deposited by laser molecular-beam epitaxy
Authors: Lu X. B. , Lu H. B. , Chen Z. H. , Zhang X. , Huang R. , Zhou H. W. , Wang X. P. , Nguyen B. Y. , Wang C. Z. , Xiang W. F. , He M. , Cheng B. L.
Published: October 2004

High permittivity LaAlO3 (LAO) and LaAlOxNy (LAON) thin films have been deposited directly on a Si(100) substrate using a laser molecular-beam epitaxy technique. Metal–oxide–silicon field-effect transistors (MOSFETs) are fabricated using such LAO and LAON thin films as gate dielectrics and well-behaved transistor characteristics have been observed. High-resolution transmission electron microscopy observations indicate that LAO thin films can remain amorphous structure even after annealing at 1000°C. The small equivalent oxide thickness (EOT) of 17Å is achieved for 75Å LAO film with an effective dielectric constant of 17.2±1 for the whole gate stack. Furthermore, a smaller EOT, larger drive current, and lower subthreshold slope have been observed for devices with the LAON thin film. For all the devices, the gate leakage currents are at least two orders of magnitude lower than that of the same electrical thickness SiO2. Reasonable subthreshold slopes of 248 and 181mV∕dec were obtained for MOSFETs with LAO and LAON films, respectively.
Nonmonotonic excitation rates in argon positive column
Authors: Arslanbekov R. R. , Kolobov V. I. , Bogdanov E. A. , Kudryavtsev A. A.
Published: October 2004

Nonmonotonic radial distributions of electron excitation rates are obtained in simulations of positive column (PC) in argon for a wide range of gas pressures 5<p<100Torr, in the tube of radius R=1cm. This effect cannot be understood from the hydrodynamic point of view and has its origin in the peculiarities of electron kinetics in PC under the studied conditions.
Laser emission from a dye-doped cholesteric liquid crystal pumped by another cholesteric liquid crystal laser
Authors: Chanishvili Andro , Chilaya Guram , Petriashvili Gia , Barberi Riccardo , Bartolino Roberto , Cipparrone Gabriella , Mazzulla Alfredo
Published: October 2004

We report the observation of laser emission from a luminescent dye-doped cholesteric liquid crystal (CLC) excited by another dye-doped CLC laser. The idea is based on the cascade of two CLC cells containing two different dyes where the emission band of the first overlaps the absorption band of the second. This system of low threshold mirrorless lasers emphasizes the main advantages of these organic materials for lasing applications and identifies a simple laser device. Preliminary characterizations of these CLC laser systems produce evidence of remarkable features that suggest fascinating developments. The main aspects are related to the wavelength tunability of the laser emission and to the miniaturization of the device.
Sulfur passivation for shallow Pd∕W∕Au ohmic contacts to p-InGaSb
Authors: Wang S. H. , Mohney S. E. , Robinson J. A. , Bennett B. R.
Published: October 2004

The relationship between the specific contact resistance of nonalloyed Pd∕W∕Au ohmic contacts to p-In0.25Ga0.75Sb and premetallization surface preparations is examined. The resistance of ohmic contacts is minimized when p-InGaSb is exposed briefly to a dilute (NH4)2S solution. This treatment minimizes the thickness of any residual oxide or sulfide layer on the semiconductor and avoids excessive etching of the semiconductor, which would make the contact less shallow. A specific contact resistance of 5.9×10−7Ωcm2 is achieved for a Pd∕W∕Au (2∕50∕145nm) contact that consumes no more than 5nm of InGaSb.
Negative capacitance in polymer-nanocrystal composites
Authors: Bakueva L. , Konstantatos G. , Musikhin S. , Ruda H. E. , Shik A.
Published: October 2004

The effect of negative capacitance (NC) was observed and investigated in conducting polymers with embedded PbS nanocrystals. NC occurred for signal frequencies up to 1MHz and was absent in control samples without nanocrystals. The amplitude of NC increased with the applied bias and was accompanied by a superlinear current–voltage characteristic. A theoretical description of NC is presented based on a voltage-induced redistribution of carriers in a nonuniform sample with nanocrystals playing the role of potential wells for carriers. The characteristic time of carrier capture by nanocrystals, determined from the frequency dispersion of NC, was ∼3×10−5s.
Self-assembly of Ag∕SiOx spherules in triangular pattern on strained surface of primary particles
Authors: Zhang X. N. , Li C. R. , Zhang Z. , Cao Z. X.
Published: October 2004

Spontaneous emergence of nanoscaled structures provides a potential alternative to the conventional bottom-up and top-down fabrication techniques. By a two-step thermal evaporation of mixed Ag2O and SiO2 powder onto sapphire substrate, concentric Ag∕SiOx spherules were assembled into a triangular pattern upon cooling on the spherical surface of large particles, which, of generally a few microns in dimension, were primarily grown with the substrate held at 1270K. The occasional presence of pentagon or heptagon defect, as required by the spherical geometry of the primary particle, was also recognized. Strain field in the oxide shell arising from expansion mismatch with the silver core seeds the subsequent nucleation events. The triangular pattern of the secondary nanoparticles can be accounted for with a minimized strain energy in the spherical surface. The self-assembled structure of striking uniformity is promising for the generation of a large family of building blocks for device production.
Revealing all types of threading dislocations in GaN with improved contrast in a single plan view image
Authors: Datta R. , Kappers M. J. , Barnard J. S. , Humphreys C. J.
Published: October 2004

In this letter, we demonstrate a transmission electron microscope based technique which reveals all types of threading dislocations (TDs) in GaN with high contrast over a relatively large area, even if the specimen is bent. This method uses a bright-field image with the crystal oriented at the ⟨1–21–3⟩ zone axis, taken using multi-beam diffraction conditions. Such an image reveals all screw, edge, and mixed types of threading dislocations. The multi-beam imaging technique described here for GaN is more generally applicable to counting the total dislocation density in a wide range of materials and structures.
Experimental verification of cross talk reduction in photonic crystal waveguide crossings
Authors: Roh Young-Geun , Yoon Sungjoon , Jeon Heonsu , Han Seung-Ho , Park Q-Han
Published: October 2004

We have experimentally demonstrated a very low cross talk in photonic crystal waveguide crossings of any kind. For cross talk reduction, we added a resonant cavity to the waveguide intersection designed to operate in microwave frequencies. The two-dimensional waveguide crossing structure was sandwiched between two parallel metal plates to eliminate radiation loss in the vertical direction. Transmission measurements revealed that when designed properly the cross talk reduction was as large as −30dB at resonance, which is qualitatively consistent with simulation results. From the experimental results, the detailed resonant mode shape at the waveguide intersection was found to play a key role in relaying the input signal in the forward direction and therefore reducing cross talk.
The characteristics of hole trapping in HfO2∕SiO2 gate dielectrics with TiN gate electrode
Authors: Lu Wen-Tai , Lin Po-Ching , Huang Tiao-Yuan , Chien Chao-Hsin , Yang Ming-Jui , Huang Ing-Jyi , Lehnen Peer
Published: October 2004

The characteristics of charge trapping during constant voltage stress in an n-type metal–oxide–semiconductor capacitor with HfO2∕SiO2 gate stack and TiN gate electrode were studied. We found that the dominant charge trapping mechanism in the high-k gate stack is hole trapping rather than electron trapping. This behavior can be well described by the distributed capture cross-section model. In particular, the flatband voltage shift (ΔVfb) is mainly caused by the trap filling instead of the trap creation [Zafar et al., J. Appl. Phys. 93, 9298 (2003)]. The dominant hole trapping can be ascribed to a higher probability for hole tunneling from the substrate, compared to electron tunneling from the gate, due to a shorter tunneling path over the barrier for holes due to the work function of the TiN gate electrode.
Upconversion luminescence of Al2O3–SiO2:Ce3+ glass by femtosecond laser irradiation
Authors: You Hongpeng , Hayakawa Tomokatsu , Nogami Masayuki
Published: October 2004

Near-infrared to visible upconversion luminescence was observed in a sol-gel processed Al2O3–SiO2 glass containing Ce3+ ions under femtosecond laser irradiation. The optical properties of the glasses reveal that the upconversion luminescence comes from the 5d→4f transition of the Ce3+ ions. The relationship between the intensity of the Ce3+ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs.
High-contrast modulation of light with light by control of surface plasmon polariton wave coupling
Authors: Krasavin A. V. , MacDonald K. F. , Zheludev N. I. , Zayats A. V.
Published: October 2004

We have demonstrated a mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave. An optical fluence of 15mJ∕cm2 in the control channel is sufficient to achieve nearly a ten-fold intensity modulation of the signal beam reflected from a Glass ∕MgF2∕Ga structure. The mechanism depends on a nanoscale light-induced structural transformation in the gallium layer and has transient switching times of the order of a few tens of nanoseconds. It offers high modulation contrast for signals in the visible and near infrared spectral ranges.
A hybrid epitaxy method for InAs on GaP
Authors: Chen A. , Yulius A. , Woodall J. M. , Broadbridge C. C.
Published: October 2004

The interface formation mechanism during the molecular-beam epitaxy (MBE) of InAs∕GaP has been studied with the aid of the In–Ga–P phase diagram. It is discovered that an initial dissolution and crystallization process similar to liquid phase epitaxy (LPE) may happen at sufficiently high temperature, resulting in a graded composition at the interface. Consequently, “parasitic LPE∕MBE” is the name for this hybrid form of MBE. High-resolution TEM images confirm the existence of the interfacial layer in the sample grown at high temperature. The graded interface smears out the band offset and leads to a nonrectifying heterojunction. Low-temperature (LT) MBE growth can turn off the LPE component, enabling the growth of an abrupt interface. Based on this “LPE∕MBE” model, a LT MBE technique is developed to grow an abrupt InAs∕InGaP interface for heterojunction power Schottky rectifiers. The LT InAs∕InGaP heterojunction demonstrates nearly ideal Schottky rectifier characteristics, while the sample grown at high temperature shows resistive ohmic characteristics. The LT InAs∕InGaP Schottky diode also demonstrates good stability with respect to anneal temperature, similar to the InAs∕GaP heterojunctions.
Ferroelectric nanomesa formation from polymer Langmuir–Blodgett films
Authors: Bai Mengjun , Ducharme Stephen
Published: October 2004

We report the fabrication and characterization of nanoscale ferroelectric structures consisting of disk-shaped nanomesas averaging 8.7±0.4nm in height and 95±22nm in diameter, and nanowells 9.8±3.3nm in depth and 128±37nm in diameter, formed from Langmuir–Blodgett films of vinylidene fluoride copolymers after annealing in the paraelectric phase. The nanomesas retain the ferroelectric properties of the bulk material and so may be suitable for use in high-density nonvolatile random-access memories, acoustic transducer arrays, or infrared imaging arrays. The nanomesa and nanowell patterns may provide useful templates for nanoscale molding or contact-printing.
Inhomogeneous electronic structure of copper phthalocyanine film measured with microspot photoemission spectroscopy
Authors: Munakata T. , Sugiyama T. , Masuda T. , Aida M. , Ueno N.
Published: October 2004

We have applied photoemission microspectroscopy to copper phthalocyanine film grown on a polycrystalline copper with a lateral resolution of 0.3μm and an energy resolution of 30meV. The photoemission band due to the highest occupied molecular orbital peaked at the binding energy of either 1.6 or 1.2eV depending on the sample positions, while the work functions were 4.3 and 4.5eV for the respective positions. The band was intense when the binding energy was low. The results demonstrate that a large inhomogeneity exists in the interface electronic structure.
Effects of high-intensity ultrasound on Bi2Sr2CaCu2O8+x superconductor
Authors: Prozorov Tanya , McCarty Brett , Cai Zhihua , Prozorov Ruslan , Suslick Kenneth S.
Published: October 2004

Slurries of powdered Bi2Sr2CaCu2O8+x (BSCCO-2212) superconductor in high-boiling alkanes were irradiated with intense ultrasound. Significant enhancements of magnetic irreversibility as well as transport critical current are reported. The effects are dependent on the concentration of the slurry and are optimal for 1.5wt% slurry loading. Electron microscopy shows that ultrasonic treatment leads to a change in grain morphology and intergrain welding. The observed enhancement of superconducting properties is consistent with the limitations in critical currents in BSCCO superconductor being due to intergrain coupling rather than intragrain pinning strength.
Hydrogen site energetics in LaNi5Hn and LaCo5Hn: Toward predicting hydrides
Authors: Herbst J. F. , Hector L. G.
Published: October 2004

We have investigated the energetics of hydrogen site occupation in LaNi5Hn (hexagonal P63mc structure) and LaCo5Hn (orthorhombic Cmmm structure) via calculation of the site-dependent enthalpies of hydride formation ΔH. For each structure ΔH was determined for a broad variety of hydrogen configurations. In LaNi5Hn(LaCo5Hn) we find that the minimum ΔH occurs for hydrogen filling of the 2b6c16c2(4e4h) sites, precisely those identified by neutron diffraction. Hydrogen-richer hydrides are predicted for both structures, in qualitative agreement with experiments performed at higher pressures.
Microfluidic method for in-situ deposition and precision patterning of thin-film metals on curved surfaces
Authors: Goluch Edgar D. , Shaikh Kashan A. , Ryu Kee , Chen Jack , Engel Jonathan , Liu Chang
Published: October 2004

We present a technique for patterning thin-film metals (silver and gold) without the need for photolithography. The technique involves microfluidics and can be performed on planar or curved surfaces. Patterns of thin-film metal are fabricated by flowing electroless silver or gold plating solutions through predefined microchannels made of polydimethylsiloxane sealed against a surface of interest. We demonstrate metal resistors with 100-μm-wide traces fabricated on planar and curved surfaces. The surface profile, mechanical gauge factor, and temperature coefficient of resistance have been characterized. Application of the resistors as hot-wire flow sensors has also been demonstrated.
Second-harmonic generation in transparent surface crystallized glasses in the BaO–B2O3–TeO2 system
Authors: Murugan G. Senthil , Suzuki Takenobu , Ohishi Yasutake , Takahashi Yoshihiro , Benino Yasuhiko , Fujiwara Takumi , Komatsu Takayuki
Published: October 2004

A transparent glass–ceramic containing borate crystallites in tellurite glass is reported. Controlled heat treatment resulted in surface crystallization of BaB4O7 in the BaO–B2O3–TeO2 glass system. The second-order optical nonlinearities observed in these surface crystallized glasses were attributed to the distortion present in the BaB4O7 unit cell as evidenced by x-ray powder diffraction studies. A d33 value of 0.08pm∕V was obtained from the Maker fringe analysis for a surface crystallized glass.