bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental human muscle pain induced by intramuscular injections of bradykinin, serotonin, and substance P
Authors: Babenko Victor , Graven‐Nielsen Thomas , Svensson Peter , Drewes Asbjørn M. , Jensen Troels Staehelin , Arendt‐Nielsen Lars
Published: July 2002

After intramuscular (m. tibialis anterior) injection of three different algogenic substances, the pain intensity was continuously scored on a visual analogue scale (VAS) in eight volunteers. The subject drew the distribution of the local and referred pain areas on a map. Four times within the first hour after injection, the pressure pain–thresholds (PPTs) and supra pressure–pain thresholds were assessed at the injection point, 2 cm distal from the injection site, at the arm, and at the contralateral leg. Measurements were done before and after injection of 0.5 ml of the algogenic substance [bradykinin (BKN), serotonin (5‐HT), substance P (SP)], and isotonic saline as control. Cutaneous sensitivity to mechanical stimuli was assessed with a Von Frey hair at the same location as PPT determinations.

The pain intensity (VAS‐peak) after BKN (2, 4, and 10 nmol) and 5‐HT (2, 4, and 20 nmol) was significantly higher (p< 0.05) than after SP (0.2, 0.4, and 0.8 nmol) and isotonic saline. The VAS‐peak after infusions of hypertonic saline was significantly higher (p< 0.05) compared with VAS‐peaks after all other substances. A significantly larger (p< 0.05) local pain area was found after BKN compared with isotonic saline. After injections of hypertonic saline, the offsets of evoked pain were significantly longer (p< 0.05) and the local and referred pain areas were significantly larger (p< 0.05) compared with all other substances. There was no dose–response relation between the pain intensity and the different doses of BKN, 5‐HT, and SP. PPTs and skin sensitivity were not affected by any of the injections.

We conclude that under the present experimental conditions, BKN and 5‐HT can produce low levels of muscle pain after intramuscular injection. In the used concentrations, however, BKN, 5‐HT, and SP did not generate cutaneous or muscular hyperalgesia.
Effects of Ge concentration on SiGe oxidation behavior
Authors: Liou H. K. , Mei P. , Gennser U. , Yang E. S.
Published: July 2002

The oxidation of SiGe layers grown by molecular beam epitaxy was studied. Auger depth profile showed that after oxidation, Ge was completely rejected from the oxide and Ge-rich layers were formed. However, the Ge concentration in the SiGe layer was found to play an important role in the formation of these Ge-Rich layers. For SiGe with Ge concentration below 50%, Si was preferentially oxidized and only one Ge-rich layer was formed at the oxide/substrate interface. On the other hand, for SiGe with Ge concentration above 50%, two Ge-rich layers were formed after oxidation with one at the oxide/substrate interface and the other at the oxide surface. X-ray photoelectron spectroscopy studies showed that Ge at the oxide/substrate interface is in elemental form, while Ge at the oxide surface is in an intermediate oxidized state. A classical binary alloy oxidation theory is employed to explain the overall oxidation behavior qualitatively.
Structure and magnetic properties of R2Fe17Cx (x∼2.5)
Authors: Liao L. X. , Chen X. , Altounian Z. , Ryan D. H.
Published: July 2002

A series of rare-earth iron carbides were prepared by heat treatment of R2Fe17 compounds in methane. The nominal composition of these carbides is R2Fe17Cx, x∼2.5. The carbides retain the original Th2Zn17 or Th2Ni17 structure with a 6.5% volume expansion over the carbon-free unit cell. For Sm2Fe17C2.5, the Curie temperature is 760 K and the easy magnetization direction is along the c axis. The anisotropy field of Sm2Fe17C2.5 at room temperature is 15±0.5 T.
Nb Josephson junction with an AlNx barrier made by plasma nitridation
Authors: Shiota Tetsuyoshi , Imamura Takeshi , Hasuo Shinya
Published: July 2002

We studied Nb junctions with aluminum nitride, AlNx, tunnel barriers formed by plasma nitridation on aluminum film surfaces. The AlNx barrier junctions show current-voltage characteristics with leakage currents small enough and critical current densities large enough for use in Josephson digital circuits. The AlNx barrier junction exhibited improved annealing stability as compared to AlOx barrier junctions. For the AlNx barrier junction, decreases in critical current during annealing at 250 °C are remarkably suppressed.
Modification of HF-treated silicon (100) surfaces by scanning tunneling microscopy in air under imaging conditions
Authors: Barniol N. , Pérez-Murano F. , Aymerich X.
Published: July 2002

The modification of HF-etched silicon (100) surface with a scanning tunneling microscope (STM) operated in air is studied for the first time in samples subjected to the standard HF etching without the follow-up rinsing in H2O. The modifications are produced in air under normal STM imaging conditions (Vt=−1.4 V and It=2 nA). The simultaneous acquisition of topographical, current image tunneling spectroscopy and local barrier-height images clearly shows that the nature of the modification is not only topographical but also chemical. The features produced with a resolution better than 25 nm are attributed to a tip-induced oxidation enhanced by the presence of fluorine on the surface.
Equilibrium multiatomic step structure of GaAs(001) vicinal surfaces grown by metalorganic chemical vapor deposition
Authors: Kasu Makoto , Kobayashi Naoki
Published: July 2002

We have studied, in the equilibrium state, the multiatomic step (multistep) structure only a few nanometers high on GaAs(001) vicinal surfaces grown by metalorganic chemical vapor deposition (MOCVD). Annealing (growth interruption) straightens multistep edges, but even after the annealing the multistep on the [1̄10]-misoriented surface is straighter than the multistep on the [110]-misoriented surface. This indicates that the free energy of the [1̄10]-step is lower than that of the [110]-step. Step bunching on this vicinal surface is caused by the formation of two facets with different orientations.
Wavelength dependence of T0 in InGaAsP semiconductor laser diodes
Authors: O’Gorman J. , Levi A. F. J.
Published: July 2002

The temperature sensitivity of laser threshold current in single mode, wavelength tunable, InGaAsP bulk active region semiconductor lasers diodes is measured in the temperature range, 293 K≲T≲355 K and wavelength range 1.23 μm≲λ≲1.35 μm. When proper account is taken of peak gain variation with temperature, the temperature dependence of laser threshold current (parameterized by T0) is insensitive to lasing wavelength over a wide tuning range.
Observation of cavity effect on spontaneous emission lifetime in AlGaAs quantum microcavities using continuous tuning of emission wavelength
Authors: Nishioka K. , Tanaka K. , Nakamura T. , Lee Y. , Yamanishi M.
Published: July 2002

Cavity effect on spontaneous emission lifetime has been observed through the continuous tuning of the emission wavelength by quantum confined Stark effect in AlGaAs Fabry–Perot microcavities. The obtained emission wavelength dependence of the exciton lifetime shows that the lifetime increases with the emission wavelength, specifically indicating a sharp increase at the cavity resonant wavelength. This behavior agrees well with the theoretical prediction based on the theoretical model of G. Björk, S. Machida, Y. Yamamoto, and K. Igeta [Phys. Rev. A 44, 669 (1991)]. Furthermore, we have also investigated the emission wavelength dependence of the transfer efficiency and obtained good agreement with the theory.
Very high two-dimensional hole gas mobilities in strained silicon germanium
Authors: Basaran E. , Kubiak R. A. , Whall T. E. , Parker E. H. C.
Published: July 2002

We report on the growth by solid source MBE and characterization of remote doped Si/SiGe/Si two-dimensional hole gas structures. It has been found that by reducing the Ge composition to ≤13% and limiting the thickness of the alloy layer, growth temperatures can be increased up to 950 °C for these structures while maintaining good structural integrity and planar interfaces. Record mobilities of 19 820 cm2 V−1 s−1 at 7 K were obtained in normal structures. Our calculations suggest that alloy scattering is not important in these structures and that interface roughness and interface charge scattering limit the low temperature mobilities.
Distinction of two-photon absorption from other nonlinear loss mechanisms by phase-conjugate interferometry
Authors: Tackx Peter , Kauranen Martti , Persoons André
Published: July 2002

We show that phase-conjugate interferometry is a measuring technique for third-order optical nonlinearities that can distinguish two-photon absorption from other nonlinear loss mechanisms. For the case of 3,3′-diethyloxadicarbocyanine iodide at 1064 nm, the nonlinear loss is dominated by linear absorption from the two-photon excited state. We observe a highly nonlinear absorption process in solutions of 4-methoxy-4′-nitrostilbene at 532 nm and show that it is due to a more complicated loss mechanism. This mechanism could have applications in optical limiting.
Carrier-induced strain effect in Si and GaAs nanocrystals
Authors: Zhao X. S. , Ge Y. R. , Schroeder J. , Persans P. D.
Published: July 2002

New experimental results on Raman scattering from porous silicon and silicon and gallium arsenide nanocrystals are reported. In all of these systems, almost all vibrational modes become Raman active and are remarkably soft. A carrier-induced strain model is proposed to explain the optical properties of these nanocrystal systems. According to this carrier-induced strain model, the selection rule of crystal momentum conservation for Raman scattering is greatly relaxed in Si and GaAs nanocrystals due to the dilatation strain caused by coupling of excited free carriers with the particle lattice and the optical properties of such systems are dominated by multiphonon assisted free-electron transition processes.
Intrinsic resputtering in pulsed-laser deposition of lead-zirconate-titanate thin films
Authors: Hau S. K. , Wong K. H. , Chan P. W. , Choy C. L.
Published: July 2002

Pulsed-laser deposition (PLD) of lead-zirconate-titanate [Pb(Zrx,Ti1−x)O3] (PZT) thin films under low ambient pressure has been investigated by studying the angular deposition distributions of the constituent elements of the films. Nonstoichiometric profiles are observed and a dip occurs near the target surface normal of the deposition profile of lead. Experimental results show that intrinsic resputtering of the film is important in the PLD process and is responsible for the anomalous distribution of lead.
Precision limits of waveform recovery and analysis in a signal processing oscilloscope
Authors: Dowell L. J. , Gillies G. T. , Cates M. R. , Allison S. W.
Published: July 2002

The precision limits of a waveform processing oscilloscope have been investigated for the situation where the instrument is used to recover a repetitive exponential signal from high levels of noise. In these studies, the oscilloscope was programmed to sample the signal, average it, and then calculate its exponential decay time constant. The measurement errors in the resulting time constants were found to decrease with continued averaging, but not without limit. In fact, we found that there was an optimum number of samples needed to minimize the error for any particular value of the signal-to-noise ratio at the input to the oscilloscope. We present here our empirically determined values of those optima, an intercomparison of them with the results of a theoretical model, and a description of the measurement system developed for this work.
Advantage of rapid thermal annealing over furnace annealing for P-implanted metastable Si/Ge0.12Si0.88
Authors: Lie D. Y. C. , Song J. H. , Nicolet M.-A. , Theodore N. D.
Published: July 2002

Metastable pseudomorphic Ge0.12Si0.88 films were grown by molecular beam epitaxy on Si(100) substrates and then implanted with 100 keV 31P at room temperature for a dose of 5×1013/cm2. Samples were subsequently annealed by rapid thermal annealing (RTA) in nitrogen and by steady-state furnace annealing in vacuum. Both damage and strain introduced by implantation can be completely removed, within instrumental sensitivity, by RTA at 700 °C for 10–40 s. Vacuum annealing for 30 min at 500–550 °C removes most of the damage and strain induced by the implantation but the activation of the P is poor. At 700 °C, the activation is nearly 100%, but the crystallinity worsens and the pseudomorphic strain begins to relax. We conclude that for a lightly implanted metastable and pseudomorphic GeSi epilayer on Si, steady-state vacuum annealing cannot achieve good dopant activation without introducing significant strain relaxation to the heterostructure, while RTA can.
Horizontal-type four-circle diffractometer station of the vertical wiggler beamline at the Photon Factory
Authors: Satow Yoshinori , Iitaka Yoichi
Published: July 2002

An experimental station with a four-circle diffractometer combined with tunable and focusing optics was designed and constructed for x-ray crystallography using synchrotron radiation from the vertical wiggler at the Photon Factory. The optics implemented into beamline 14A comprises a double-crystal monochromator and a double-focusing mirror so as to yield high photon flux x rays tunable over wide wavelength regions. The diffractometer with its equatorial plane in the horizontal was specially fabricated for rapid and accurate measurements of x-ray diffraction intensities from macromolecular crystals, and was provided with an alignment carriage as well as computer control and measuring systems. The station has proved to be particularly useful for such applications as anomalous scattering studies of protein crystals and also EXAFS studies at high photon energies.
A high-pulse-repetition-frequency CO2 Doppler lidar for atmospheric monitoring
Authors: Pearson Guy N.
Published: July 2002

A monostatic pulsed CO2 Doppler lidar operating in a short-pulse (<1 μs), high-pulse-repetition-frequency (≳1 kHz), low-pulse energy (1–10 mJ) mode has been developed for Doppler and return-power measurements within the planetary boundary layer. The system has achieved near-quantum-limited performance, demonstrating a Doppler measurement capability to approximately 5 km with pulse energies of 1–2 mJ.
High-efficiency retarding-potential Mott polarization analyzer
Authors: Burnett G. C. , Monroe T. J. , Dunning F. B.
Published: July 2002

A compact retarding-potential Mott polarimeter is described that employs a thorium target. When operating at an electron accelerating voltage of 25 kV, the instrument provides effective asymmetry (Sherman) functions Seff between −0.15 and −0.25, the exact value being determined by the inelastic energy loss window selected. The corresponding scattering efficiencies I/I0 are in the range ∼6–2×10−3 resulting in optimized efficiencies η (≡S2effI/I0) of ∼1.6×10−4. These efficiencies are much larger than have been obtained previously with similar analyzers. The instrument is simple to construct, is stable in operation, and has a large electron-optical acceptance, estimated to be ∼104 mm2 sr eV. It is fully UHV compatible and is suitable for application in a wide range of spin-dependent studies.
Signal averaging x-ray streak camera with picosecond jitter
Authors: Maksimchuk A. , Kim M. , Workman J. , Korn G. , Squier J. , Du D. , Umstadter D. , Mourou G. , Bouvier M.
Published: July 2002

We have developed an averaging picosecond x-ray streak camera using a dc-biased photoconductive switch as a generator of a high-voltage ramp. The streak camera is operated at a sweep speed of up to 8 ps/mm, shot-to-shot jitter is less than ±1 ps. The streak camera has been used to measure the time history of broadband x-ray emission from an ultrashort pulse laser-produced plasma. Accumulation of the streaked x-ray signals significantly improved the signal-to-noise ratio of the data obtained.
A high capacity 0.23 K 3He refrigerator for balloon-borne payloads
Authors: Cheng Edward S. , Meyer Stephan S. , Page Lyman A.
Published: July 2002

We describe the design, operation, and performance of a high capacity, single stage, 3He refrigerator optimized for balloon-borne payloads. A temperature of ∼0.2 K is routinely maintained for more than seven days at ∼100 μW total heat load. Recycling can be completed in less than 12 h. A simple design avoids valves and explicit heat switches, resulting in simplified construction and improved performance. A numerical model characterizes the operating temperature of the system over a large range of conditions.
Soft x-ray magneto-optic Kerr rotation and element-specific hysteresis measurement (invited)
Authors: Kortright J. B. , Rice M.
Published: July 2002

Soft x-ray magneto-optic Kerr rotation has been measured using a continuously tunable multilayer linear polarizer in the beam reflected from samples in applied magnetic fields. Like magnetic circular dichroism, Kerr rotation in the soft x-ray region can be element specific and much larger than in the visible spectral range when the photon energy is tuned near atomic core resonances. Thus sensitive element-specific hysteresis measurements are possible with this technique. Examples showing large Kerr rotation from an Fe film and element-specific hysteresis loops of the Fe and Cr in an Fe/Cr multilayer demonstrate these new capabilities. Some consequences of the strong anomalous dispersion near the Fe L2,3 edges to the Kerr rotation measurement are discussed.
Diagnostics for plasma processing (etching plasmas) (invited)
Authors: Hershkowitz Noah , Breun Robert A.
Published: July 2002

Plasma processing diagnostics play two different roles—characterization and control. The goal of plasma characterization is to establish connections of data with external parameters and to verify models. The goal of control diagnostics is to make noninvasive in situ measurements of relevant processing parameters. Diagnostics used in semiconductor etching are considered. These include Langmuir probes, laser induced fluorescence, optical emission spectroscopy, infrared and Fourier transform infrared absorption spectroscopy, mass spectrometry, microwave interferometry, and radio frequency diagnostics. An example is given of the use of many diagnostics in characterizing SiO2 and Si etching by fluorocarbons.
Perturbation theoretical analysis and its application for TM010-mode microwave cavity of a gas laser
Authors: Guochang Xu , Jun Liu
Published: July 2002

An analytical expression and a perturbation formula for the cavity resonant frequency dependence of plasma are derived for the cylindrical TM010-microwave plasma cavity. A comparison between the exact and the approximate solution shows that the perturbation theory can be used accurately to analyze the perturbation effect on the cavity resonant frequency caused by microwave plasma in low pressure microwave excited gas lasers. A new method is proposed to prevent detuning of the cavity by the perturbation of the plasma and glass tube, so that a uniform and steady-state microwave plasma is successfully formed and a stable laser output power is also obtained. The electron density and the microwave dielectric constant of a tube shell can be measured by the perturbation approach.
Fluorescence decay-time characteristics of erbium-doped optical fiber at elevated temperatures
Authors: Zhang Z. Y. , Grattan K. T. V. , Palmer A. W. , Meggitt B. T. , Sun T.
Published: July 2002

An investigation of lifetime characteristics of fluorescence, over the wavelength region ∼1.5 μm from pumped Er-doped fibers of various activator concentrations, at temperatures up to ∼950 °C, has been carried out and a significant variation of fluorescence lifetimes with temperature was seen. The results have an impact upon the use of laser or stimulated emission processes at much higher temperatures and for lifetime-based, fiber-optic temperature sensors, showing a very favorable characteristic for such latter applications.
Diagnostics for initial plasma operations on the National Spherical Torus Experiment
Authors: Kaita R. , Hatcher R. , Johnson D. , Kugel H. , McCormack B. , Roquemore A. L. ,   the NSTX Team
Published: July 2002

The goals of the diagnostic set for initial plasma operations on the National Spherical Torus Experiment (NSTX) are to provide information on the fundamental discharge parameters necessary to characterize NSTX plasmas, and guide NSTX operations for optimized performance. While most of these diagnostics involve relatively straightforward techniques requiring little or no research and development, and rely heavily on reusing existing equipment, a few pose considerable challenges due to the NSTX geometry. Magnetic diagnostics and visible discharge imaging will be the primary systems for plasma control and equilibrium. Confinement and transport studies will be supported by electron temperature, density, and impurity profile diagnostics. Scrapeoff layer and divertor physics will be investigated with spectroscopic and bolometric diagnostics, thermocouples, and edge Langmuir probes. X-ray fluctuation diagnostics and magnetic pickup coils will be provided for MHD stability analysis. The latter impose special difficulties for NSTX, because of the high temperature environment and the very limited space on the center stack. This article provides an overview of the diagnostics planned for the first phase of NSTX, and highlights the design features needed to satisfy the difficult constraints the device imposes on magnetic diagnostics.
A frequency modulated mm-wave interferometer with a single sideband upconverter
Authors: Kim B. C. , Hong J. , Yang J. G. , Na H. K. , Hwang S. M. ,   Hanbit Project Team, Chung K. H.
Published: July 2002

A frequency modulated interferometer is developed, which uses a 94 GHz Gunn oscillator and a single sideband (SSB) upconverter as a frequency modulator. An SSB upconverter makes it possible to use a heterodyne phase measurement technique with one mm-wave source. In addition, the influence of frequency drift and phase noise of a mm-wave source on the phase measurement can be reduced. In this work, the performance of a SSB upconverter as a frequency modulator is examined. Also, overall performance of the mm-wave interferometer with a SSB upconverter and line density measurement results in a mirror device are described.
Influence of nitrogen additions on hot-filament chemical vapor deposition of diamond
Authors: Bohr S. , Haubner R. , Lux B.
Published: July 2002

The influence of N2 additions (5%–40% N2/CH4) on various features of hot-filament chemical vapor deposition (CVD) of diamond layers is presented and discussed using experimental results and calculations of the thermodynamic equilibrium. Small N2 additions (5%–10% N2/CH4) improved the diamond phase purity but led surprisingly either to an increase or decrease of the growth rate depending upon the filament temperature. The effects are attributed to a reduction of carbon supersaturation due to an abstraction of adsorbed hydrogen atoms caused by CN and HCN. Higher N2 additions (20%–40% N2/CH4) revealed a deterioration of the diamond phase purity and reversal growth rates. These results are probably caused by a beginning reconstruction of the diamond surface which is originated from enhanced abstraction of adsorbed hydrogen and the inefficiency of CN or nitrogen species to stabilize the diamond surface structure.
Crystalline carbon nitride films formation by chemical vapor deposition
Authors: Zhang Yafei , Zhou Zhonghua , Li Hulin
Published: July 2002

Crystalline carbon nitride films have been synthesized in a rf plasma assisted hot filament chemical vapor deposition system. Large crystalline grains up to ∼10 μm in size as well as film-like regions are observed in the morphology of the films. β-C3N4 with two groups of lattice parameters (one is consistent with the theoretical value and the other is ∼3% smaller) in the deposited films on polycrystalline Ni substrate has been revealed by x-ray diffraction spectrum (XRD). No Raman shift peaks have been found by Raman scattering measurement, but some presently unknown diffraction peaks appeared in the XRD spectrum. It is proposed that there are possible unknown structures of crystalline C-N in the films.
Nanometer-scale recording on an organic-complex thin film with a scanning tunneling microscope
Authors: Ma L. P. , Song Y. L. , Gao H. J. , Zhao W. B. , Chen H. Y. , Xue Z. Q. , Pang S. J.
Published: July 2002

Nanometer-scale recording on an organic-complex thin film with a scanning tunneling microscope (STM) under ambient conditions is demonstrated. The recording marks are made by applying external voltage pulses between the tip and the highly ordered pyrolytic graphite substrate. A 30×30 nm2 STM image with recorded marks is given. The average recorded mark is 1.3 nm in diameter, which corresponds to a data storage density of about 1013 bits/cm2. The current–voltage characteristics measured by the STM show an insulator behavior for the unrecorded regions, and a conductor behavior for the recorded regions, which indicates that the data are recorded by local change of the electrical property of the films.
Structures and defects induced during annealing of sputtered near-equiatomic NiTi shape memory thin films
Authors: Gong F. F. , Shen H. M. , Wang Y. N.
Published: July 2002

Structures and defects induced during annealing were studied in free-standing NiTi thin films produced by rf magnetron sputtering. Ni4Ti3 precipitates coherent with the (B2) matrix do not affect the shape memory behavior of the thin films annealed at 550 °C for short times. With the further increase of the annealing time and/or temperature, less coherent Ni4Ti3 precipitates develop and hinder the shape memory behavior. The embrittlement of the annealed films probably results from grain–boundary precipitation, thermal etching, and stress gradients.
Linewidth broadening by 1/f noise in wavelength-tunable laser diodes
Authors: Amann M.-C. , Hakimi R. , Borchert B. , Illek S.
Published: July 2002

The excess linewidth broadening of continuously tunable InGaAsP/InP laser diodes at 1.5 μm wavelength is investigated. Terminal electrical and FM noise measurements indicate that the recombination processes in the forward biased tuning region produce significant 1/f carrier noise. Below 1 MHz the 1/f noise dominates yielding a noise enhancement of about 30 dB at 1 kHz. The discrepancy observed so far between theoretically expected and measured spectral linewidth can be well resolved by taking into account this additional noise source.
Low noise in a diffusion-cooled hot-electron mixer at 2.5 THz
Authors: Karasik B. S. , Gaidis M. C. , McGrath W. R. , Bumble B. , LeDuc H. G.
Published: July 2002

The noise performance of a Nb hot-electron bolometer mixer at 2.5 THz has been investigated. The devices are fabricated from a 12-nm-thick Nb film, and have a 0.30 μm×0.15 μm in-plane size, thus exploiting diffusion as the electron cooling mechanism. The rf coupling was provided by a twin-slot planar antenna on an elliptical Si lens. The experimentally measured double sideband noise temperature of the receiver was as low as 2750±250 K with an estimated mixer noise temperature of ≈900 K. The mixer bandwidth derived from both noise bandwidth and IF impedance measurements was ≈1.4 GHz. These results demonstrate the low-noise operation of the diffusion-cooled bolometer mixer above 2 THz.
Metal/polymer adhesion enhancement by reactive ion assisted interface bonding and mixing
Authors: Wu P. K. , Lu T.-M.
Published: July 2002

The adhesion strength between sputter deposited Al on Teflon AF 1600 was increased from <0.15 N/mm to >0.7 N/mm by treating the interface with reactive ion assisted interface bonding and mixing (RIAIBM) and subsequent annealing. X-ray photoelectron spectroscopy measurements indicate the RIAIBM process and subsequent annealing promotes material mixing, implantation of the reactive species, bond breaking, and new bond formation at the interface. These factors are known to increase adhesion strength. The implementation of RIAIBM is straight forward and is suitable for application to both metal-on-polymer and polymer-on-metal systems.
Frequency upconversion in Er3+/Yb3+-codoped chalcogenide glass
Authors: Oliveira A. S. , de Araujo M. T. , Gouveia-Neto A. S. , Medeiros Neto J. A. , Sombra A. S. B. , Messaddeq Y.
Published: July 2002

Frequency upconversion of cw infrared radiation at 1.06 μm into the visible in Er3+/Yb3+-codoped Ga2S3:La2O3 chalcogenide glass samples is presented. Intense green and red emission bands around 530, 555, and 670 nm, respectively, are observed in addition to near-infrared 830 and 925 nm less intense signals. Energy transfer processes and nonradiative phonon-assisted decays account for the population of the H211/2, S43/2, and F49/2 emitting levels. The dependence of the red emission with the Yb3+ concentration is also analyzed. The potential application of the Er/Yb-codoped Ga2S3:La2O3 glass for upconversion based optical devices is discussed.
Stimulated emission from vacuum-deposited thin films of a substituted oligo(p-phenylene vinylene)
Authors: Brouwer Hendrik-Jan , Krasnikov Victor V. , Pham Thuy-Anh , Gill Richard E. , Hadziioannou Georges
Published: July 2002

The influence of the morphology on the light emission properties of vacuum-deposited polycrystalline oligo(p-phenylene vinylene) thin films under intense laser excitation was studied. The morphology of the thin films was varied by annealing just below the first melting point (crystal-mesophase transition) and by crystallization from the isotropic melt. Amplified spontaneous emission occurred within the individual domains and was only observed when the domain size was increased by thermal treatment. The amplified spontaneous emission threshold for the melt-crystallized thin films was found to be comparable to that for conjugated polymer thin films.
Visible emission from Er-doped GaN grown by solid source molecular beam epitaxy
Authors: Steckl A. J. , Birkhahn R.
Published: July 2002

Visible light emission has been obtained from Er-doped GaN thin films. The GaN was grown by molecular beam epitaxy on sapphire substrates using solid sources (for Ga, Al, and Er) and a plasma gas source for N2. Above GaN band-gap photoexcitation resulted in strong green emission. The emission spectrum consists of two narrow green lines at 537 and 558 nm and a broad peak at light blue wavelengths (480–510 nm). The narrow lines have been identified as Er transitions from the H11/22 and S3/24 levels to the I15/24 ground state. The intensity of the 558 nm emission decreases with increasing temperature, while the intensity of the 537 nm line actually peaks at ∼300 K. This effect is explained based on the thermalization of electrons between the two closely spaced energy levels.
Silicon single electron memory cell
Authors: Stone N. J. , Ahmed H.
Published: July 2002

A compact single-electron memory cell has been fabricated in silicon using a process that is compatible with complementary metal–oxide–semiconductor circuit fabrication. The device is based on the Coulomb blockade effect observed in highly doped silicon nanowires. The circuit shows clear memory operation with a >100 mV gap between “0” and “1” levels when tested at a temperature of 4.2 K. The response of the circuit to write and erase pulse sequences is also presented.
InGaAsN solar cells with 1.0 eV band gap, lattice matched to GaAs
Authors: Kurtz Steven R. , Allerman A. A. , Jones E. D. , Gee J. M. , Banas J. J. , Hammons B. E.
Published: July 2002

The design, growth by metalorganic chemical vapor deposition, and processing of an In0.07Ga0.93As0.98N0.02 solar cell, with 1.0 eV band gap, lattice matched to GaAs is described. The hole diffusion length in annealed, n-type InGaAsN is 0.6–0.8 μm, and solar cell internal quantum efficiencies >70% are obtained. Optical studies indicate that defects or impurities, from InGaAsN doping and nitrogen incorporation, limit solar cell performance.
Self-defocusing in ultrasonic hyperthermia: Experiment and simulation
Authors: Floch Claire Le , Tanter Mickaël , Fink Mathias
Published: July 2002

During hyperthermia treatments with high intensity focused ultrasounds, the temperature elevation locally induces a change of sound speed which acts itself as an aberrator for the ultrasonic beam. Such a thermal lens effect may become noticeable as time increases and leads to significant effects like the self-defocusing of the beam. This letter presents an experimental evidence of this effect, and a finite difference simulation of the coupled wave and heat equations is presented that demonstrates similar phenomenon.
Dielectric hysteresis from transverse electric fields in lead zirconate titanate thin films
Authors: Xu Baomin , Ye Yaohong , Cross L. Eric , Bernstein Jonathan J. , Miller Raanan
Published: July 2002

Excellent symmetric dielectric hysteresis is observed from lead zirconate titanate (PZT) thin films using transverse electric fields driven by interdigitated surface electrodes. The 1-μm-thick PZT films with a Zr/Ti ratio of 52/48 are prepared on ZrO2 buffered, 4-in.-diam silicon wafers with a thermally grown SiO2 layer. Both the ZrO2 buffer layer and PZT film are deposited by using a similar sol–gel processing. Remanent polarization of about 20 μC/cm2 with coercive field less than 40 kV/cm is obtained as measured using a triangle wave at 50 Hz. Thicker films are being developed and retention for the transversely polarized state is currently under study. One of the objectives of this study is to develop a large array of d33-driven unimorph sensing elements for a high-resolution acoustic imaging system.
TiN
x
films with metallic behavior at high N/Ti ratios for better solar control windows
Authors: Smith G. B. , Swift P. D. , Bendavid A.
Published: July 2002

Using cathodic arc deposition with 700 eV nitrogen ion assistance, metallic response in TiNx thin films to at least N/Ti=1.3 is found. Metallic behavior is usually limited to N/Ti ratios just above 1.1. Defects are almost exclusively Ti vacancies which further enhances optical changes. The resulting large shift in onset of Drude reflection to longer wavelengths enhances the view, daylighting, and environmental performance of a coated window relative to stoichiometric TiN films on glass.
Magnetic anisotropy of ferromagnetic La0.7(Sr, Ca)0.3MnO3 epitaxial films
Authors: Steenbeck K. , Hiergeist R.
Published: July 2002

The biaxial and uniaxial magnetic anisotropy in epitaxial (100)-oriented La0.7(Sr, Ca)0.3MnO3 films on different substrates were measured by torque magnetometry in the range from T=20 K to room temperature. The biaxial anisotropy with easy axes 〈110〉 dominates and can be described by a cubic crystal anisotropy constant up to K1≈−104 J/m3. A tendency of increasing |K1| with increasing lattice constant c was explained by compressive stress. The uniaxial anisotropy was |KU|⩽103 J/m3 and explained by anisotropic stress not correlated to the crystal axes.
Enhancement of Jc by 211 particles in ternary (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy melt-processed superconductors
Authors: Muralidhar M. , Koblischka M. R. , Diko P. , Murakami M.
Published: July 2002

( Nd 0.33 Eu 0.33 Gd 0.33 ) 2 BaCuO 5 (NEG-211) particles are added to ternary (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy (NEG) bulk, melt-processed superconductors. By means of transmission electron and polarized light microscopy, we found that two types of 211 particles are formed; large NEG-211 and submicron-sized particles containing mostly Gd in the rare earth site are formed which can act as effective flux pinning sites. The critical current density at zero field increases monotonously as a function of the NEG-211 concentration, but the secondary peak vanishes above 40 mol % 211 addition. As a result, a critical current density of 68 000 A cm−2 at 77 K and 2.5 T applied field is achieved with at 40 mol % 211 additions.
Launching surface plasmons into nanoholes in metal films
Authors: Sönnichsen C. , Duch A. C. , Steininger G. , Koch M. , von Plessen G. , Feldmann J.
Published: July 2002

We investigate optical transmission through individual nanometer-sized holes in opaque metal films using scanning near-field optical microscopy. We show unambiguously that excitation and lateral propagation of surface plasmons support the light transmission through these nanoholes. The direction of the surface plasmon propagation is given by the light polarization, thus controlled addressing of individual holes is possible. In addition, we find characteristic interference effects due to scattering of surface plasmons off holes.
Relaxational polarization dynamics in soft ferroelectrics
Authors: Chen Yun-Han , Viehland Dwight
Published: July 2002

Investigations of the frequency dependence of the P–E (polarization versus field) and ε–E (strain versus field) behavior have been performed on soft 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 polycrystalline ferroelectrics at various maximum field strengths below and above that of the coercive field (Ec). For E<Ec, a strong relaxational polarization was observed. At low frequencies, in this field range, P–E curves indicative of polarization switching were observed with an apparent remanence, however at higher frequencies near-linear P–E behavior was found.
The H+N2O→OH(2ΠΩ,υ′,N′)+N2 reaction: OH rotational angular momentum polarization
Authors: Brouard M. , Gatenby S. D. , Joseph D. M. , Vallance C.
Published: July 2002

The OH state-resolved angular momentum polarization generated by the H+N2O reaction has been investigated at a mean collision energy of 1.5 eV. The data were obtained under room temperature bulb conditions using 225 nm photolysis of H2S to generate translationally excited H atoms, and employed Doppler-resolved laser induced fluorescence to probe the nascent OH reaction products. The measurements revealed the OH rotational angular momentum, j′, to be aligned in the scattering plane (i.e., in the plane containing the reactant and product relative velocity vectors, k and k′). Furthermore, j′ was found to be preferentially aligned parallel to k′, particularly for lower OH rotational states. Out-of-plane torsional forces have been shown, therefore, to play an important role in generating OH rotation as the fragments separate. The new data are discussed in light of previously published studies of the title reaction, both from our own laboratory, and from those of other workers. Insight into the reaction mechanism is provided by comparison with the photodissociation dynamics of HN3, which helps, in particular, to clarify the origin of the propeller-like OH rotational angular momentum polarization.
Strained InGaAs/GaPAsSb heterostructures grown on GaAs (001) for optoelectronic applications in the 1100–1550 nm range
Authors: Braun W. , Dowd P. , Guo C.-Z. , Chen S.-L. , Ryu C. M. , Koelle U. , Johnson S. R. , Zhang Y.-H. , Tomm J. W. , Elsässer T. , Smith D. J.
Published: July 2002

We present a novel semiconductor quantum well (QW) structure consisting of alternating (In,Ga)As and Ga(P,As,Sb) layers grown pseudomorphically on a GaAs substrate by all-solid-source molecular beam epitaxy. The band gap of the QW is determined by the thickness and composition of both types of layers and can be varied from 1.1 to 1.55 μm. Calculations show that the observed strong room-temperature photoluminescence in this wavelength range can be explained by a type-II transition in the QW. Structural investigations by reflection high-energy electron diffraction, transmission electron microscopy, and secondary ion mass spectroscopy confirm a triple layer structure with laterally modulated composition. Photoluminescence measurements reveal a linewidth of 50 meV at 1.3 μm and a luminescence decay time of 240 ps. Our investigations demonstrate the feasibility of this materials system for vertical cavity surface-emitting lasers and other optoelectronic devices on GaAs.
Quantum cascade lasers with monolithic air–semiconductor Bragg reflectors
Authors: Hvozdara L. , Lugstein A. , Finger N. , Gianordoli S. , Schrenk W. , Unterrainer K. , Bertagnolli E. , Strasser G. , Gornik E.
Published: July 2002

Electrically pumped GaAs/AlGaAs quantum cascade lasers with monolithic one-dimensional photonic-band gap mirrors are presented. The mirrors consist of two, precisely defined grooves trenched across the laser ridge using a focused ion beam. A substantial improvement of the laser performance is achieved due to the increased reflectivity of these mirrors. A decrease of the threshold current by 40% at 150 K is observed. The maximum operation temperature increases from 155 K for an unmodified laser to 170 K for the laser with the modified mirrors, and an increase of the T0 parameter from 99 to 114 K is found.
IRMA: A tunable infrared multicomponent acquisition system for plasma diagnostics
Authors: Röpcke J. , Mechold L. , Käning M. , Anders J. , Wienhold F. G. , Nelson D. , Zahniser M.
Published: July 2002

A compact and transportable infrared multicomponent acquisition (IRMA) system based on infrared absorption spectroscopy has been developed for plasma diagnostics and control. The IRMA system contains four independent tunable diode lasers which can be temporally multiplexed and directed into plasma reactors or into a multipass cell for exhaust gas detection. Rapid scan software with real-time line shape analysis provides simultaneous measurements of the absolute concentrations of several molecular species.
Room-temperature electron spin relaxation in bulk InAs
Authors: Boggess Thomas F. , Olesberg J. T. , Yu C. , Flatté Michael E. , Lau Wayne H.
Published: July 2002

Polarization-resolved, subpicosecond pump–probe measurements at a wavelength of 3.43 μm are used to determine the electron spin relaxation time T1 in bulk InAs at room temperature. The measured T1 of 19±4 ps is in excellent agreement with the theoretical value of 21 ps, which is obtained from a nonperturbative calculation based on the D’yakonov–Perel’ mechanism of precessional spin relaxation [M. I. D’yakonov and V. I. Perel’, Sov. Phys. JETP 38, 177 (1974)].
Simulations of the nucleation of AgBr from solution
Authors: Shore Joel D. , Perchak Dennis , Shnidman Yitzhak
Published: July 2002

We use molecular dynamics to study the nucleation of AgBr in water. After first testing our Born–Mayer–Huggins potentials for Ag+ and Br− by looking at bulk AgBr and at AgBr clusters in vacuo, we consider small numbers of Ag+ and Br− ions immersed in water. The system shows the expected qualitative features of nucleation form solution, including a critical cluster size that decreases with increasing concentration. However, we find that for cluster sizes at least as large as Ag18Br18, the most stable cluster is disordered. This is in stark contrast to clusters in vacuo where clusters as small as Ag4Br4 from ordered fragments of the lattice. These results lend some support to the conjecture that nucleation of crystals from solution is a two-stage process with the first stage consisting of the formation of disordered clusters of solute and the second stage involving the nucleation of a crystal from this solute “melt.”
EL2, EL3, and EL6 defects in GaAs highly implanted with sulfur
Authors: Yokota Katsuhiro , Kuchii Hideto , Nakamura Kazuhiro , Sakaguchi Masanori , Takano Hiromichi , Ando Yasunori
Published: July 2002

Sulfur ions were implanted into a semi-insulating GaAs wafer at 50 keV at a dose of 1×1015 cm−2. The implanted GaAs wafer was annealed at temperatures of 650–1000 °C for 15 min. Deep levels were measured in regions with carrier concentrations lower than 3×1017 cm−3, after layers of various thicknesses were removed from the surface of the wafer. The dominant defects in samples annealed at temperatures lower than 850 °C were EL2 and EL6, while 1000 °C annealed samples exhibited isolated EL2 and EL3 defects. Isolated EL2 defects were observed in regions of carrier concentrations lower than 1×1017 cm−3, and EL3 defects were observed in regions of carrier concentrations higher than 2×1017 cm−3.
Transmittance in irradiated poly(methyl methacrylate) at elevated temperatures
Authors: Lu K.-P. , Lee Sanboh , Cheng Cheu Pyeng
Published: July 2002

The transient transmittance of gamma-ray irradiated poly(methyl methacrylate) at elevated temperatures is investigated. The transmittance in the ultraviolet and visible range decreases with an increase of radiation dose. We propose that the color center is responsible for the reduction of transmittance in the irradiated specimen. Then the concentration of the color center decreases with increasing annealing time at elevated temperatures. The transmittance data at 407 nm are in excellent agreement with the theoretical model in which the color center is annihilated by a second order kinetic process. The rate constant follows the Arrhenius equation. The activation energy in the range of 44.27–51.52 kJ/mol decreases with increased dose.
Vibrational spectra of the methanol tetramer in the OH stretch region. Two cyclic isomers and concerted proton tunneling
Authors: Vener Mikhail V. , Sauer Joachim
Published: July 2002

Second order Mo/ller–Plesset perturbation theory and density functional theory are employed to localize several stationary points on the potential energy surface of the cyclic methanol tetramer. Two cyclic isomers are identified: one of S4 symmetry, with methyl groups in up-down-up-down configuration, and a second one of Ci symmetry, with the methyl groups in up-up-down-down configuration. The latter minimum is 360 cm−1 above the S4 minimum, with a barrier of 475 cm−1 separating them. These isomers give rise to four asymmetric OH modes around 3300 cm−1. A model of the concerted proton transfer, S4→D2d→S4 (D2d is the transition structure), yields an estimate of 0.7 cm−1 for the tunneling splitting of the totally symmetric OH stretch vibrational fundamental. Raman spectra would show evidence of this fundamental and help to identify admixtures of the Ci isomer.
Dynamic light scattering with femtosecond laser pulses: Potential and limitations toward quasielastic nonlinear light scattering
Authors: Clays Koen , Persoons André
Published: July 2002

We have implemented dynamic linear and second-order nonlinear light scattering with femtosecond laser pulses. The periodical structure of the impinging light itself does not impede the measurement for intensity correlation times longer than the pulse-to-pulse period. However, the inherently large spectral bandwidth of femtosecond pulses considerably reduces the amplitude of the autocorrelation function. Reducing the coherence volume to increase this amplitude results in a lower count rate. The low efficiency of the second-order nonlinear light scattering, possible relaxation oscillation in solid-state femtosecond lasers, and its quadratic amplification in second-order nonlinear scattering have pronounced influence on the autocorrelation function. Finally, typical relaxation times expected for the dynamics associated with large fluctuations in second-order nonlinearity put a severe limit on the applicability of quasielastic nonlinear light scattering for the study of chemical reaction dynamics.