bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric properties for SF6 and SF6 mixtures predicted from basic data
Authors: Kline L. E. , Davies D. K. , Chen C. L. , Chantry P. J.
Published: February 2003

We have calculated α and η, the ionization and attachment coefficients, and (E/N) *, the limiting breakdown electric-field–to–gas-density ratio, in SF6 and SF6 mixtures by numerically solving the Boltzmann equation for the electron energy distribution. The calculations require a knowledge of several electron collision cross sections. Published momentum transfer and ionization cross sections for SF6 were used. We measured various attachment cross sections for SF6 using electron-beam techniques with mass spectrometric ion detection. We determined a total cross section for electronic excitation of SF6 by comparing the predicted values of α, η, and (E/N) * with our measured values obtained from spatial current growth experiments in SF6 in uniform fields over an extended range of E/N. With this self-consistent set of SF6 cross sections, together with published He and N2 cross sections, it was then possible to predict the dielectric properties of SF6-He and SF6-N2 mixtures. Published experimental values of α for the SF6-He mixtures lie between the values of α calculated with and without ionization of SF6 by excited He atoms. Published experimental values of (E/N) * agree with our calculations to within 5% in both the SF6-He and the SF6-N2 mixtures.
Thin-film optical waveguide polarizer using semiconducting cadmium sulphide
Authors: Sasaki K. , Hamano O. , Abe H.
Published: February 2003

An optical waveguide attenuative polarizer is realized by a slab-type glass film waveguide covered with a semiconducting cadmium sulphide top layer. Cross-sectional energy distribution and absorption in the guide is vitally influenced by the top layer thickness for each polarization mode. Selection of the specific mode can be achieved by controlling the top layer thickness. Experiment is compared with theoretical analysis.
Magnetic hysteresis behavior and microstructure of severely cold-worked and aged Co-Fe-Nb alloy
Authors: Suzuki Yuichi , Sagawa Masato , Okada Masanori , Henmi Zenzo
Published: February 2003

The magnetic hysteresis behavior of severely cold-worked and aged 85Co-12Fe-3Nb alloy was studied in relation to the microstructure. Magnetic hardening of the alloy can be attributed to the pinning of the domain wall by quasispherical Co3Nb precipitates. Alloys cold worked to 97.8% reduction in area and aged at 700, 800, and 900 °C showed the hysteresis behavior characteristic of inhomogeneous domain wall pinning, whereas alloys cold worked to 99.7% and aged at 700, 800, and 900 °C exhibited extremely rectangular loops indicative of homogeneous wall pinning. The differences in hysteresis behavior can be explained by differences in their microstructures. It was ascertained by high-voltage electron microscopy that the spatial distribution of precipitates in the 99.7% cold-worked sample was more homogeneous than that in the 97.8% cold-worked one. Domain structures observed by Lorentz microscopy indicate that the domain walls are not rigid but they have sufficient flexibility. From these results, the magnetization reversal process of the alloy has been discussed.
Oxygen precipitation in silicon
Authors: Patrick W. , Hearn E. , Westdorp W. , Bohg A.
Published: February 2003

This paper presents the results of our observing oxygen precipitation in a silicon crystal at 1000 °C using infrared absorption, TEM, and x-ray techniques. Comparison of results shows excellent agreement between TEM and IR for the number of precipitate particles formed. TEM data show that the number of particles increases as the annealing time is increased for oxygen contents above a critical concentration ratio of about 4 (30 ppma at 1000 °C). The number of particles formed at lower ratios remains relatively small. Detailed analysis of the TEM results has yielded a relationship between precipitate volume and the total area of punched-out loops. These loops, however, account for only a small fraction of the silicon atoms displaced by the growing precipitates. X-ray results indicate the defects are of an interstitial nature, in agreement with TEM.
Magnetic aftereffect in ordered β′-NiAl B2 phase
Authors: Cho Seung-Am
Published: February 2003

The behavior of the time lag of magnetization of normalized β′-NiAl phase under a 15-kOe applied magnetic field is studied. The time-dependent creep magnetization curve does not fit the parabolic relation which describes the diffusion process of the magnetic moments. The magnetic relaxation process followed the Voigt-Kelvin type of anelastic behavior, from which the relaxation time τ=4.73 min was obtained.
Production of negative ions in an alkali hydride arc
Authors: Vanek V. , Dixon D. P. , Gekelman W.
Published: February 2003

Beams of negative ions have been extracted from a plasma generated in a laser-initiated arc passing through a vapor released from an alkali hydride. Beam duration has been greater than 15 msec. An attainable H− production efficiency of 41 kW/A is indicated by the present experiment. Such a source would have certain key advantages over other proposed negative ion sources.
X-ray total-external-reflection–Bragg diffraction: A structural study of the GaAs-Al interface
Authors: Marra W. C. , Eisenberger P. , Cho A. Y.
Published: February 2003

A new technique utilizing conventional x-ray diffraction in conjunction with total external reflection has provided a powerful tool for studying ordered interfaces and surface phenomena. It has been used in this work to study the details of the interface region of a molecular beam epitaxially grown Al single crystal on a molecular beam epitaxially grown GaAs single-crystal substrate. A simple model including variations of the lattice parameter and disorder in the interface region is in agreement with these experimental results.
Low-temperature helium release in nickel
Authors: Thomas G. J. , Swansiger W. A. , Baskes M. I.
Published: February 2003

Measurements of 3He released by thermal desorption have been made in high-purity annealed, cold-worked, and single-crystal nickel samples. The 3He was introduced by natural tritium decay to eliminate implantation produced defects. Release was observed in the temperature region from ∼100 to 300 K and above 800 K; no desorption occurred at intermediate temperatures. The low-temperature release amounted to only ∼1% of the total 3He generated. Thus, even in the case of relatively defect-free materials, helium becomes strongly trapped with a binding energy of ∼2 eV. The low-temperature data can best be modeled with a bulk mobility of ∼0.35 eV and a pipe diffusion path of lower activation energy.
Simple technique for charge centroid measurement in MNOS capacitors
Authors: Schauer Henry , Arnold Emil
Published: February 2003

A simple technique for determining the centroid of the charge injected into the nitride of an MNOS capacitor during a voltage pulse is described. The technique has the advantage over existing methods in that it requires no special test structure or specialized measurement circuitry, but employs only common commercially available electronic equipment. The technique is used to investigate the trap properties of nitrides prepared under different conditions. Using the trap parameters obtained, memory characteristics are calculated from existing MNOS models and compared with experimental results.
Time dependence of depletion region formation in phosphorus-doped silicon MOS devices at cryogenic temperatures
Authors: Saks N. S. , Nordbryhn A.
Published: February 2003

The time dependence of depletion region formation in 1015/cm3 phosphorus-doped silicon MOS devices in the temperature range 14–25 °K has been observed using three different experiments: fast ramp C-V measurements, pulsed capacitor measurements, and pulsed transistor measurements. It is observed that the time required to form a depletion region in thermal equilibrium is strongly dependent on the applied gate bias. Following the application of a gate bias from accumulation to deep depletion, a peak is observed in the substrate current versus time. These results are explained by the dependence of the electron-emission rate from the phosphorus donors on the electric field in the semiconductor (Poole-Frenkel effect). Calculations from a one-dimensional model including the field emission effect are shown to predict the major features of the data.
A new model of isothermal charge transport for negatively corona-charged Teflon
Authors: von Seggern Heinz
Published: February 2003

In this paper we study theoretically and experimentally the transport of electrons in Teflon FEP type A under isothermal conditions (145 °C) in open circuit. We suggest a theoretical model including surface, shallow, and deep traps. The model leads to a system of partial differential equations which was solved numerically using a finite-step algorithm. By fitting the theoretical to the experimental surface-voltage decay curves we found a shallow-trap-modulated mobility μQ=1.6×10−12 cm2/V sec, a deep-trap-modulated transit time tT=1.25×105 sec in the voltage range of −200 to −400 V for electrons in 25-μm-thick material. We also determined the time constants for surface injection, trapping, and detrapping. The deep-trap-modulated transit time is in good agreement with measured values. Further we found a voltage-independent mean free path for the shallow-trapped carriers λ=6.5 μm. These traps were assumed to be in thermal equilibrium with the free carriers in the conduction band.
Evidence of nonlinear processes from x-ray spectra of CO2 laser-irradiated targets
Authors: Pépin H. , Martin F. , Grek B. , Johnston T. W. , Kieffer J. C. , Mitchel G.
Published: February 2003

CH2, Al, and Pb targets have been irradiated at a maximum flux of 3×1013 W cm−2 with a focused CO2 laser in order to study the effects of nonlinear processes on x-ray emission. A multichannel x-ray spectrometer measured the x-ray spectrum from 1 to 50 keV. Above a critical flux of 6×1012 W cm−2, the results show a change in the slope of soft x-ray intensity versus laser flux, a change in the power-law dependence of hot temperature versus flux, an anisotropy of soft x-ray emission, and a strong production of energetic electrons. With increasing Z, there is no reduction of the effects of nonlinear phenomena, which appeared stronger with Al. The comparison with experiments performed at 1.06 μm suggests that the fraction of laser energy present in fast electrons scales as φλ2.
Experimental study on the onset of positive corona in atmospheric air
Authors: McAllister I. W. , Crichton G. C. , Bregnsbo E.
Published: February 2003

This paper reports the findings of a study into the gas physical processes which lead to the inception of the positive corona discharge in atmospheric air. A multiple avalanche process is observed to be a basic feature, and correlation with the works reported in the literature suggests that at corona onset the physical phenomena are independent of electrode radius of curvature ρ in the range 0.04<ρ (mm) <250. The various models used to simulate the precorona discharge sequence and to predict corona-onset field-strength values are then examined. It is concluded that the development of a rigorous physical-mathematical model of corona onset must await a full understanding of the avalanche-to-corona transition mechanism. Prior to this, a simple empirical approach is adequate for the prediction of corona-onset field strengths.
Burn-through of thin aluminum foils by laser-driven ablation
Authors: Arad B. , Eliezer S. , Gazit Y. , Loebenstein H. M. , Zigler A. , Zmora H. , Zweigenbaum S.
Published: February 2003

Aluminum foils 1–75 μm thick were irradiated by 500-psec Nd-glass laser pulses with intensities 6×1012 to 1014 W/cm2. The reflected and transmitted light and the produced x rays were measured using PIN photodiodes and crystal spectrometers. Two torsion pendula were used to measure the target and the plasma momenta. Both measurements are consistent with a simple hydrodynamic model. We obtain plasma pressures in the range 1.5–13 Mbars, shock-wave velocities between 0.9×106 and 2.6×106 cm/sec, penetration depths of the ablation surface in the domain of 3–10 μm for laser intensities in the range 6×1012 to 1014 W/cm2. The burn-through times (i.e., the times that a hole is opened in the foil) for foils 25, 50, and 75 μm thick are measured to be 8±5, 18±5, and 25±5 nsec, respectively.
Linear compressibilities of NaNO2 and NaNO3
Authors: Hazen R. M. , Finger L. W.
Published: February 2003

The linear compressibilities of sodium nitrite and sodium nitrate have been determined from x-ray diffraction of synthetic single crystals mounted in a miniature diamond-anvil high-pressure cell at pressures to 27 kbars. Compressibilities of both compounds are anisotropic; compression perpendicular to rigid N-O bonds is approximately 3.5 times greater than compression within the plane of N-O bonding. In NaNO2 axial compression ratios are a : b : c=1.0 : 0.46 : 0.28. For a second-order Birch-Murnaghan equation of state, K0=219±2 kbars and K′=4.3±0.8. The a : c axial compression ratio of NaNO3 is 0.35 : 1.0. Linear compressibilities are in agreement with data of Bridgman, who determined bulk modulus, K0=258±6 kbars, and K′=6.6±1.5. The product of bulk modulus and molar volume (K0V0) is a constant for alkali halides with the NaCl structure, and the same value is observed for NaNO2, which is only slightly distorted from an NaCl arrangement of Na+ and NO−2. Sodium nitrate, which does not posssess the NaCl topology of Na+ and NO−3, deviates from this constant. Broadening of x-ray diffraction maxima of NaNO2 above 10 kbars may be due to twinning in a high-pressure phase of NaNO2. Such twinning could indicate reduced symmetry; however, the high-pressure diffraction data indicate a deviation from orthogonality of less than 1°.
Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs
Authors: Partin D. L. , Chen J. W. , Milnes A. G. , Vassamillet L. F.
Published: February 2003

Nickel diffused into VPE n-GaAs at 700 °C for 20 min reduces the hole diffusion length Lp from 4.3 to 1.1 μm. Deep-level transient spectroscopy (DLTS) has been used to identify energy levels in Ni-diffused GaAs at Ev+0.39 eV and Ec−0.39 eV, which have identical concentration profiles. The as-grown VPE GaAs contains traces of these levels as well as an electron trap at Ec−0.75 eV in a concentration of 1.5×1015 cm−3. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. Previous work has shown that the Ec−0.75 eV level is related to growth under As-rich conditions, so it may be a gallium vacancy complex. A technique for measuring minority-carrier capture cross sections has been developed, and indicates that Lp in Ni-diffused VPE n-GaAs is controlled by the Ec−0.39 eV level.
Intrinsic limitations of doping diamonds by heavy-ion implantation
Authors: Kalish R. , Deicher M. , Recknagel E. , Wichert Th.
Published: February 2003

The local environment of 111In implanted into diamonds has been studied by means of the perturbed angular correlation technique as a function of annealing temperature and of implantation dose. It is found that even when the diamond is heated under vacuum to the highest possible temperature before graphitization occurs (2100 K), the implants are not driven to spherically symmetric sites in the lattice. This lack of annealing, if common to all heavy implants, may have serious consequences on the usefulness of doping of diamond by heavy-ion implantation.
TEM observation of catastrophically degraded Ga1−xAlxAs double-heterostructure lasers
Authors: Ueda Osamu , Imai Hajime , Kotani Tsuyoshi , Wakita Koichi , Saito Hideho
Published: February 2003

Defect structures of degraded GaAs/Ga1−xAlxAs double-heterostructure (DH) lasers applied with pulsed current under high current density are studied by transmission electron microscopy. Several kinds of defects are observed corresponding to the 〈110〉 dark-line defects which are observed in the photoluminescence patterns of the degraded DH lasers. They are arrays of dislocation tangles, nearly perfect dislocation networks, pipe-shaped defects with strong dark contrast, and simple dislocation dipoles. The former three kinds of dislocations are assumed to be caused by the propagation of molten zone due to local heating at the mirror surface and the last defects may be caused by thermal stress.
Scaling laws for pulsed chain-reaction chemical lasers
Authors: Mirels H. , Hofland R. , Whittier J. S.
Published: February 2003

Scaling laws for pulsed chain-reaction chemical lasers are deduced with the use of a two-level vibrational model. The performance of a saturated laser depends only on the parameter K=tcd/tp, where tcd and tp are the characteristic collisional-deactivation and pumping times, respectively. The normalized output energy per unit volume per pulse of a saturated HF chain-reaction laser is 2E/εH2,0 =K[1+0(K)], where E is output energy per unit volume per pulse, ε is energy per mole of photons, and H2,0 is the initial concentration of H2 in moles per unit volume. In the range 0.02?φ≪1, the normalized output energy from a saturated HF laser can be expressed as 2E/εH2,0=φ, where φ∼ (F/F2)1/20(F2/H2)0[1 +0.094(F2/H2)0]−1/2. In the latter regime the product Ete is a constant for a saturated laser (te=pulse length).
Acceleration of the gradual degradation in (GaAl)As double-heterostructure lasers as an exponent of the value of the driving current
Authors: Mizuishi Ken’ichi , Chinone Naoki , Sato Hitoshi , Ito Ryoichi
Published: February 2003

Double-heterostructure (GaAl)As lasers are tested at various temperatures and driving conditions, including spontaneous mode operation. Results show that the rate of degradation is primarily determined by driving current rather than optical output when aging at optical outputs of 10 mW/facet or less and heat-sink temperatures of 50–100 °C. A new composite Arrhenius relation including a current-dependent factor is empirically derived, and excellent agreement is found between calculated and experimental results, especially in regard to the effects of current on the rate of gradual degradation. The thermal activation energy derived by the above relation is estimated to be 0.8±0.1 eV, and laser lifetime at an optical output of 5 mW/facet and heat-sink temperature of 25 °C is expected to exceed 3.4×105 h. The role of current in inducing gradual degradation is also discussed.
Surface-wave reflection phenomena at interfaces on y-z LiNbO3
Authors: Goruk W. S. , Stegeman G. I.
Published: February 2003

Light-scattering techniques were used to study various aspects of the reflection of surface acoustic waves (SAW) at three different interfaces on y-z LiNbO3. Investigated were a free-metallized surface boundary, the edge of a thick gold film, and a crystal corner. In all three cases, the reflection coefficient was measured and found to be a maximum for the crystal corner and small for both film interfaces. Light scattering from the acoustically created surface corrugations near the interface was used to identify the transition region in which bulk modes as well as SAW are present. The angular spectrum and total power of bulk waves created via mode conversion from surface waves were also measured.
Analysis of the thermal lensing effect for an optically thick sample—A revised model
Authors: Fang Howard L. , Swofford Robert L.
Published: February 2003

A revised model of the thermal lensing effect is presented which treats the sample as an extended optical medium having a transverse quadratic index of refraction gradient. The revised model relaxes the restriction on sample cell length inherent in earlier models which treated the sample as an optically thin lens. It is shown how the increased sample length allows higher-sensitivity measurement of optical absorption. Possible sources of error in the thermal lens experiment are discussed. The present model specifically addresses the problem of accounting for the elliptical beam shape of the cw dye laser used in the thermal lens experiment. The absorptivity of benzene at 607 nm (the 6←0 transition of the C-H stretching vibration) is measured to be (2.3±0.2) ×10−3 cm−1.
Bernstein waves in bismuth
Authors: Tewari D. P. , Sharma R. R.
Published: February 2003

In this paper we have derived the general dispersion relation for electrostatic waves in bismuth in the presence of a static magnetic field along the trigonal axis by solving the Vlasov equation for electrons and holes. The effect of many-valley band structure, anisotropy in the carrier mass, and degeneracy in the distribution function are incorporated. The dispersion relation is explicitly solved for Berstein waves. In the limit of negligible degeneracy, the dispersion relation resembles very closely to the one in gaseous plasmas.
Experimental properties of injection lasers: VIII. Narrow stripe lasers with induced waveguide
Authors: Sommers H. S.
Published: February 2003

The properties of a type of cw (AlGa)As injection laser whose waveguide is produced or modified by the conditions of operation are studied as a function of current and of delay after the start of a 10-μs square current pulse. They are illustrated by data on a representative unit from a popular structure, the oxide stripe laser, operating in the fundamental spatial mode and with linear power-current characteristic. At the start of the pulse the laser behaves like an oscillator with rigid cavity walls, with mode profiles invariant of current, mode powers linear in junction voltage, and smooth envelope of the spectrum. With delay, all these properties are lost; the beam changes its shape and direction, the shape and position of the coherent near field are changed, and the spectral envelope changes erratically. Since the voltage profile across the facet retains its shape and symmetry and is invariant of delay, the effects are not associated with modifications of the profile of gain or free carriers. They seem to be due to development of a temperature profile beneath the stripe contact. Comparison at fixed current between the changes with delay of the profiles of the modes and the change in propagation constant strengthens the interpretation. Analysis of this laser shows that a 15% increase in free-carrier density is inconsequential to the observed mode confinement, and that spatial hole burning has no role in the modification of its waveguide.
Acousto-optic measurement of bulk wave generation by interdigital transducers excited at SAW resonance
Authors: Goruk W. S. , Stegeman G. I.
Published: February 2003

The angular distribution and total power of bulk acoustic waves generated by one and 25 finger pair interdigital transducers on y-z lithium niobate are reported. It was found that the bulk wave radiation from the 25 finger pair grid originates primarily from the transducer ends.
Resolution criteria in scanning microscopes
Authors: Nongaillard B. , Rouvaen J. M. , Bruneel C. , Bridoux E. , Torguet R.
Published: February 2003

The physical nature of the sample-illuminating wave (coherent or incoherent and focused or plane) and of the detector (phase or intensity sensitive) must be accounted for in the definition of a resolution criterion for a scanning microscope. The purpose of this paper is to study the resolution criterion for coherent scanning acoustical and optical microscopes, owing to the properties of the available detectors for each kind of radiation. The theoretical results are well supported by the experimental findings for the scanning acoustic microscope.
Fabrication of 6H-SiC light-emitting diodes by a rotation dipping technique: Electroluminescence mechanisms
Authors: Ikeda M. , Hayakawa T. , Yamagiwa S. , Matsunami H. , Tanaka T.
Published: February 2003

Various light-emitting diodes of 6H–SiC, doped in the n layers with Al, Ga, or B acceptors and N donors, have been fabricated using a rotation dipping technique. A detailed study of electroluminescence mechanisms from ∼100 to 400 K has been carried out using photoluminescence, electroluminescence, and time-resolved spectra. At low temperatures the radiation originates mainly in the p layer, and around room temperature in the n layer. The luminescence mechanisms are free-exciton recombinations for the peak at ∼425 nm, donor-acceptor pair recombinations for the main broad band, transitions within localized centers for the peak at ∼455 nm, and recombinations due to divacancies for the series of peaks beginning at ∼470 nm. The dependence of the electroluminescence efficiency on the N concentration in the n layers is studied and methods to improve efficiency are discussed. The maximum external quantum efficiencies obtained were 1.2×10−5 for Al-doped, 9×10−6 for Ga-doped, and 2.5×10−5 for B-doped diodes, and were improved by a factor of 2 by using an epoxy coating.
Iron-free solid-disk-rotor asynchronous machines
Authors: Sultanem F. , Rioux C.
Published: February 2003

In this paper the authors present a two-dimensional geometrical study of the simplified theoretical model of an asynchronous machine with air-coil windings and disk rotor. Detailed experiments with a mock-up enable them to adjust a parameter (pole pitch length) to obtain theory/experiment agreement systematically.
A physical model for acoustic signatures
Authors: Atalar Abdullah
Published: February 2003

A physical model is presented to explain the interference phenomenon that gives rise to the material-dependent signature obtained from an acoustic reflection microscope. An approximate formula is derived for the peak separation of the characteristic response, and it agrees well with the experimental results.
The temperature variation of the dielectric constant of ’’pure’’ CaF2, SrF2, BaF2, and MgO
Authors: Wintersgill Mary , Fontanella John , Andeen Carl , Schuele Donald
Published: February 2003

Improved values of the real part of the low-frequency dielectric constant are presented for ’’pure’’ CaF2, BaF2, SrF2, and MgO over the temperature range 5.5-400 K. Accurate measurements of both the real and imaginary parts of the dielectric constant were made so that corrections could be made to allow for dipolar impurities. The final results are thought to be accurate to better than 0.1% over the full range of temperatures.
The evaporation rate from a single cathode spot on precious metal electrodes in vacuum arcs
Authors: Kubono Takayoshi
Published: February 2003

Utilizing the values of a cathode spot radius and its temperature, which are calculated on the basis of the cathode mechanism theory proposed recently by Kubono, the rate of metal evaporation from a single cathode spot on Ag, Au, Ir, Pd, Pt, and Rh electrodes is expressed in simple approximate formulas as a function of arc current. In the case of Ag and Au electrodes, the calculated results are found to be in agreement with experimental data by different investigators, but it is difficult to compare calculations with measurements on the other electrodes because of few experimental data. This estimating process and these approximate formulas for the radius, temperature, and evaporation rate on the cathode spot as a function of arc current are useful, because it is very laborious to measure the cathode spot radius, temperature, and the evaporation rate.
Nonlinear elastic effects in the ultrasonic assessment of cumulative internal damage in filled polymers
Authors: Knollman G. C. , Martinson R. H.
Published: February 2003

Dewetting and cumulative internal damage in filled polymers are being studied by means of a new ultrasonic technique. Previously, a theoretical model was formulated which relates ultrasonic measurements made on a polymer to vacuole formation and growth. In this model, the effect on soundwave propagation of higher-order (nonlinear) elastic phenomena in the material was neglected in comparison with that of the vacuoles. The nonlinear elastic effects are the subject of the present analysis. The theory developed here is combined with the previous analytical treatment to obtain a quantitative model for ultrasonic assessment of polymer damage which is valid for nondewetted as well as dewetted material. Computations made according to the comprehensive theoretical model are found to be in close agreement with ultrasonic data taken on typical specimens of a filled polymer undergoing uniaxial strain.
Temperature dependence of the resonant frequency of electroded doubly-rotated quartz thickness-mode resonators
Authors: Tiersten H. F. , Sinha B. K.
Published: February 2003

A system of approximate equations for the determination of thermal stresses in piezoelectric plates with large thin films of a different material plated on the surfaces is derived. The plate equations are obtained by making a suitable expansion of the pertinent variables in the thickness coordinate, inserting the expansion in the appropriate variational principle and integrating with respect to the thickness in the manner of Mindlin. Conditions resulting in both extensional and flexural stresses are considered and the full anisotropy of the quartz is included in the treatment. The particular case of purely extensional thermal stresses resulting from large electrodes of equal thickness plated on the major surfaces of doubly-rotated quartz thickness-mode resonators is treated in detail. The changes in resonant frequency resulting from the thermally induced biasing stresses and strains are determined from an existing perturbation equation. Calculations, using the newly defined first temperature derivatives of the fundamental elastic constants of quartz, are performed for large gold electrodes on doubly-rotated quartz plates.
Effect of interfacial species on shear strength of metal-sapphire contacts
Authors: Pepper Stephen V.
Published: February 2003

The interfacial shear strength of the metal-insulator system has been studied by means of the coefficient of static friction of copper, nickel, or gold contacts on sapphire in ultrahigh vacuum. The effect on contact strength of adsorbed oxygen, nitrogen, chlorine, and carbon monoxide on the metal surfaces is reported herein. It was found that exposures as low as 1 L of O2 on Ni produced observable increases in contact strength, whereas exposures of 3 L of Cl2 lead to a decrease in contact strength. These results imply that submonolayer concentrations of these species at the interface of a thin Ni film on Al2O3 should affect film adhesion similarly. The submonolayer concentrations of these species are present on the metal surface as chemisorbed phases, without the formation of surface films of metal compounds. Thus, chemical reaction of metal compounds (oxides, for example) with Al2O3 is excluded as a source for the increase in interfacial strength. The atomic mechanism by which these surface or interface phases affect interfacial strength is not yet understood.
Structure, photovoltaic properties, and angle-of-incidence correlations of electron-beam-deposited SnO2/n-Si solar cells
Authors: Feng Tom , Ghosh Amal K. , Fishman Charles
Published: February 2003

The effects of the angle of incidence on the structural and photovoltaic properties of electron-beam-deposited SnO2/n-Si solar cells have been studied in detail. X-ray diffraction analyses of SnO2 films deposited on silicon indicate the presence of multiple phases of tin oxide. A correlation is observed between the angle of incidence and x-ray diffraction pattern. The angular dependences of the short-circuit photocurrent, open-circuit photovoltage, fill factor, conductivity, and efficiency were similar. A model is proposed to explain the observed photovoltaic parameter versus angle of incidence results. In this model, the carrier ’’transmission’’ or tunneling probability across the interfacial SiO2 layer is assumed to be a function of the crystallite orientation and phases of the tin oxide.
Boundary scattering and 1/f noise
Authors: Hooge F. N. , Kedzia J. , Vandamme L. K. J.
Published: February 2003

Noise measurements on thin bismuth films show that boundary scattering does not contribute to 1/f noise.
Excess thermal noise and low-frequency oscillations in capillary flow of non-Newtonian aqueous polymer solutions exhibiting elasticity
Authors: Hedman K. , Klason C. , Kubát J.
Published: February 2003

Results of thermal noise measurements (frequency range 0.01–1000 Hz) on aqueous solutions of poly(ethylene oxide) and maltose/poly(acrylamide) during capillary flow are reported. The flow of these solutions, both being of the pseudoplastic (shear thinning) type, gave rise to an excess thermal noise exhibiting a 1/fα-frequency distribution. The excess noise level increased with the flow rate. At a critical value of this rate, the noise showed a pulsating character. The corresponding frequency spectra contained a number of sharp peaks, all being multiples of a fundamental frequency of the order of 1 Hz. Increasing the flow rate still higher caused the pulsations to disappear, the excess noise regaining its 1/fα character. The pulsations appear to be associated with the elasticity of the solutions used. Solutions with comparable shear thinning properties but lacking elasticity did not produce such effects. No excess thermal noise was observed with Newtonian solutions of comparable viscosity.
The inductance of a superconducting strip transmission line
Authors: Chang W. H.
Published: February 2003

An analytical formula is derived to calculate the inductance of a finite-width superconducting strip transmission line. The formula gives an accurate inductance value when the aspect ratio (the ratio of the linewidth to the insulation thickness) exceeds about unity.
Defects in synthetic quartz: Radiation-induced mobility of interstitial ions
Authors: Markes M. E. , Halliburton L. E.
Published: February 2003

Electron-spin resonance (ESR) has been used to investigate defect formation, anneal, and migration effects in commercially available high-quality synthetic quartz. Electronic-Grade and premium Q material, both unswept and swept, were included in the study and an electron accelerator was used for all irradiations. Previously unreported holelike and electronlike paramagnetic defects have been observed and their production and decay properties are described. The concentration of aluminum-associated trapped hole centers (now known as [Ale+]° centers) was found to be a strong function of irradiation temperature and previous electrodiffusion (sweeping) treatments. Irradiation of an as-received unswept sample at 77 K produced very few [Ale+]° centers. If the same unswept sample was irradiated at room temperature and then reirradiated at 77 K, the [Ale+]° center concentration was enhanced by one to two orders of magnitude. The intermediate irradiation at room temperature is believed to remove interstitial Na+ ions from the vicinity of the substitutional aluminum ions and thus allow the aluminum ions to trap holes during the second 77 K irradiation. The onset of the radiation-induced mobility of the Na+ ions occurs between 200 and 250 K. An intense [Ale+]° center ESR spectrum was found after the initial 77 K irradiation of the as-received commercially swept samples, and the intermediate room-temperature irradiation caused no enhancement of the spectrum during a subsequent reirradiation at 77 K. This suggests that radiation-induced mobility of hydrogen ions occurs at 77 K. As an application of these results, a sensitive testing procedure is described for measuring the extent to which the interstitial Na+ ions have been removed from a synthetic quartz sample by the commercial sweeping process.
Studies on dielectric behavior of insulator-conductor composites
Authors: Rajagopal C. , Satyam M.
Published: February 2003

This paper describes the dielectric behavior of an insulator-conductor composite, namely, the wax-graphite composite. The variation of specific capacitance of these composites with parameters such as volume fraction and grain size of the conducting particles and temperature has been studied. These observed variations have been explained using the same model [C. Rajagopal and M. Satyam, J. Appl. Phys. 49, 5536 (1978)] which explains electrical conduction in composites. The specific capacitance of these materials appears to be governed by the contact capacitance between the conducting particles and the number of contacts each particle has with its neighbors. The variation of specific capacitance with temperature is attributed to the change in contact area.
Strain-enhanced luminescence degradation in GaAs/GaAlAs double-heterostructure lasers revealed by photoluminescence
Authors: Wakefield B.
Published: February 2003

Photoluminescence degradation observed in room-temperature-lifetested GaAs/GaAlAs DH stripe lasers has been correlated with the strain field induced in the devices by the stripe-defining oxide. A degradation mechanism based on strain- and nonradiative-recombination-enhanced point-defect migration is proposed.
Measurement of phase fluctuations in a HF chemical laser beam
Authors: Wang C. P. , Varwig R. L.
Published: February 2003

A new phase detector, which uses an acousto-optic modulation and optical heterodyne technique, has been developed. The minimum detectable phase difference is 4 °, with a temporal response of 10 μsec and a spatial resolution of 0.14 mm. This phase detector was used to measure fluctuations in the wave front of a cw HF chemical laser beam caused by mechanical vibration, medium turbulence, and gain variation. Potential applications are laser beam quality measurement, beam steering measurement, and sensing for an active resonator.
Electric discharge excitation of thallium in high-pressure xenon
Authors: Schumann L. W. , Wildman D. W. , Gallagher A. C.
Published: February 2003

We report data obtained in pulsed 1.5–280-MW/l electric discharges in thallium-doped xenon gas at thallium densities of (1.5–26) ×1015 cm−3 and xenon densities of (1–4) ×1019 cm−3. Stable steady-state discharges were obtained without the use of preionization or sustainers. Steady-state E/N, J/N, and Tl and Xe excited-state populations were determined for the positive column of the discharge. These measurements indicate an electron temperature of 0.45–0.65 eV, with the gas temperature remaining at ∼0.1 eV during the several-microsecond discharges. The thallium states lower in energy than Tl(8S1/2) generally show a higher excitation temperature than the states from Tl(8S1/2) to the thallium ionization limit, particularly at the higher current densities. The homogeneity of a 9-cm-long transverse discharge and the effects of this discharge on a laser beam propagating through the thallium-xenon medium were investigated. The implications of these results for a discharge-pumped Tl-Xe excimer laser are discussed.
Glow-discharge optical spectroscopy measurement of B-, Ge-, and Mg-implanted GaAs
Authors: Williamson Kenneth R. , Theis W. M. , Yun S. S. , Park Y. S. , Ehret J. E.
Published: February 2003

Glow-discharge optical spectroscopy (GDOS) was used as a technique for obtaining impurity-concentration profiles of annealed and unannealed GaAs implanted with Ge, B, and Mg. Calibration to obtain the absolute concentration was accomplished by comparison to pure elemental standards. For implantation fluences of 1×1015/cm2 and energies of 60 and 120 keV, the range and magnitude are compared with the theoretical predictions of LSS. Large surface pileup and out diffusion have been observed for Mg implants annealed at temperatures between 700 and 900 °C. As-implanted Mg samples exhibited different profiles for pyrolytic and plasma Si3N4 encapsulation due to differences in deposition temperatures.
State identification and stability of magnetic bubbles with unit winding number
Authors: Gallagher Timothy J. , Ju Kochan , Humphrey Floyd B.
Published: February 2003

High-speed photography has been used to distinguish between the possible S=1 bubble states. Transient photographs show that one of the states has two slow wall sections, each of which contains one member of a pair of opposite-winding vertical Bloch lines. The two unichiral states are detectable because of the characteristically slow velocity of a wall whose center spin is opposed to an applied in-plane field. It is confirmed that bubbles containing a pair of opposite-winding VBL’s automote when subjected to bias field pulsing and a constant in-plane field. Under certain pulse conditions, unichiral bubbles are shown to automote. The stability of each of the possible S=1 states with respect to the pulse amplitude and width is investigated.
Double-pulse excitation experiments on the Ca+ cyclic laser
Authors: Cross Lee A. , Cem Gokay M.
Published: February 2003

The total energy output of a Ca+ laser oscillating on the 866.1- and 854.2-nm emision lines in a double-pulse laser system as a function of the delay time between pulses has been measured. A very significant increase in the output energy occurs as the delay time between the discharges is decreased, reaching a maximum value at about 90 μsec for the discharge conditions employed. This improvement in performance is attributed to the difference between the destruction rates of the Ca+ ions in the 3d 2D3/2 and 3d 2D5/2 laser terminal states and that of the 4s 2S1/2 Ca+ ion ground state and to the fact that the initial discharge produces a considerable concentration of Ca+ ions which persist until the second discharge occurs. The consequences of this observation to the construction of a high-repetition-rate laser are discussed.
Film-thickness effect on the calculation of pressure using Hertz’s law
Authors: Gupta Mool C. , Ruoff Arthur L.
Published: February 2003

When a diamond indentor with a spherical tip is pressed against a diamond flat, the high pressures generated can be calculated using Hertz’s equation. By use of Newton’s ring technique it is shown that the pressure with a thin film present between the diamonds is essentially the same pressure as calculated for diamond-to-diamond contact using Hertz’s equation.
Nonlinear dislocation motion via nonequilibrium molecular dynamics
Authors: Hoover William G. , Hoover Nathan E. , Moss William C.
Published: February 2003

Methods are developed to treat the nonlinear propagation of edge dislocations in atomic lattices. Static or low-velocity calculations incorporate Eshelby’s analytic solution of the elastic equations. At higher, even transonic velocities, a novel fixed-displacement boundary is used to allow steady-state propagation of edge dislocations. These techniques are applied to crystals with the triangular-lattice structure. The dependence of the Peierls-Nabarro strain and propagation velocity on the range of the forces is studied. Propagation at higher strains and nonlinear effects, transonic dislocation velocities and climb, are also described.
Accordion-type laser-Raman (ALR) oscillations in crystalline polymers
Authors: Peterlin A.
Published: February 2003

If one interprets the ALR absorption lines of crystalline polymers in terms of oscillating elastic rods of length equal to the thickness L of the crystalline lamellae, or the thickness D of the crystalline core of the lamellae, one obtains for the elastic modulus of these rods values which are substantially higher than the axial elastic modulus Ec of the crystal lattice. The effect is particularly conspicous with polymers which in the crystalline state exhibit a helical-chain conformation. The explanation of this effect seems to be the elastic coupling of longitudinal oscillations of chain stems of subsequent lamellae by the intervening amorphous layers. The apparent increase of the ALR oscillation frequency by such coupling is particularly large if the elastic modulus Ea of the amorphous layers is equal or even higher than that of the crystal lattice. The high value of Ea derived from such an analysis is a consequence of the very high ALR frequency (∼0.3 THz), which makes the amorphous layer react as a rigid glass.
X-ray diffraction and dielectric temperature dependence study of the K2Cd2(SO4)3 paraelastic-ferroelastic phase transition
Authors: Lissalde F. , Abrahams S. C. , Bernstein J. L. , Nassau K.
Published: February 2003

The thermal expansion coefficients of the orthorhombic a, b, and c axes in langbeinite-type K2Cd2(SO4)3 are α=24(2) ×10−6, 12(1) ×10−6, and 19(2) ×10−6 deg−1, β=5(1) ×10−8, 8(1) ×10−8, and 5(1) ×10−8 deg−2, γ=2(1) ×10−10, −6(1) ×10−10, and 6(1) ×10−10 deg−3, respectively, between 287 and 425 K. Above the first-order phase transition at Tc=432 K, α=19(1) ×10−6 deg−1. The sulfate tetrahedra angular rotations are less than 5° between 298 and 417.5 K but are as much as 20° between 417.5 and 443.5 K. Over 70% of the rotations are estimated to take place within 2–3 K of Tc. The room-temperature dielectric constants ε1, ε2, and ε3 are about 8, 8, and 16, respectively, at 1 kHz: a jump of about 5% occurs at Tc. Two spontaneous strains decrease markedly as Tc is approached, but all three remain greater than 2×10−3. The ferroelastic displacements decrease by as much as 0.25 Å between 298 and 417.5 K to values ranging from 0.22 to 0.91 Å. The absolute sense of the piezoelectric shear coefficient d14 has been measured as positive, i.e., a tensile stress along [011] generates positive polarity on (100), negative on (1̄00). The magnitude of d14 is about 7.3(5) ×10−12 C N−1, the electromechanical coupling factor k14 is 0.124(5), and the elastic compliance s11 is 1.72(2) ×10−11 m2 N−1.
Microstructural evaluation of multicomponent ZnO ceramics
Authors: Santhanam A. T. , Gupta T. K. , Carlson W. G.
Published: February 2003

A microstructural evaluation was made of experimental non-Ohmic ZnO ceramics by optical, scanning, and transmission electron microscopy complemented with electron beam microprobe and x-ray analyses. Four crystalline phases were identified: a major phase of ZnO grains containing Co and Mn in solid solution and three minor phases of bismuth silicate (12 Bi2O3⋅2SiO2), pyrochlore (Bi2[Zn4/3Sb2/3]O6) and spinel (Zn7Sb2O12) in the intergranular region. Transmission electron microscopy revealed that the ZnO grains are mostly in direct contact with each other and that the intergranular phase is located primarily in the multiple grain junctions. In those regions where ZnO grains are in contact with each other, the measured grain-boundary width was ?25 Å. It is suggested that the barrier to conduction in ZnO varistors resides in the vicinity of the grain boundary within the ZnO grains and not in the intergranular insulating layer.
Auger analysis of ultrathin SiO2 layers on silicon
Authors: Wager J. F. , Wilmsen C. W.
Published: February 2003

The Auger LVV lines of ultrathin SiO2 layers thermally grown on Si are analyzed by comparing the measured lines with lines synthesized from standard SiO2 and Si lines. The synthesized lines were corrected for ion and electron beam effects and charging. The synthesis technique provides quantitative interpretation of the Auger lines in the interfacial region. An apparent thickness-dependent transition region is observed which can be explained as either a graded SiO2-Si region or as an abrupt SiO2-Si transition with a nonuniformly thick oxide. The latter is the more probable.
Quasistatic theory of frost deformation in thermoplastic films
Authors: Handojo Andrianto
Published: February 2003

For the description of frost deformation in thermoplastic films, a quasistatic approach has been used. Considering equipotential and nonequipotential models, a relation between the spatial wavelength λ and the amplitude of the deformation is derived from the pressures in the equilibrium state. From this relation follows a predominant value of the frost wavelength to film thickness ratio λ/h. Reasonable agreement with the experimental results reported in the literature is obtained, i.e., the equipotential model is more appropriate, the predominant value of λ/h is approximately equal to π, and the frost can also occur if the surface potential is lower than the threshold value.