bluuebunny/crossref_metadata_2025 huggingface dataset:
A fast-opening switch for use in REB diode experiments
Authors: Mendel C. W. , Goldstein S. A.
Published: February 2003

The operating characteristics of a plasma-filled fast-opening switch and its performance in pinching experiments on Sandia’s Proto I accelerator (double sided, 2 MV, 7.2 Ω, 24 nsec each side) are described. The growth of a sheath between the plasma and the cathode of the switch is the mechanism responsible for the switch impedance rising from 0.1 to 50 Ω in 10 nsec. The effect of this switch on diode prepulse and machine turn-on transient suppression is discussed.
Analysis for the electromagnetic fields of a dipole located within a metal-cased borehole
Authors: Wait James R.
Published: February 2003

A solution is obtained for the electromagnetic fields of a dipole of arbitrary orientation located within a cylindrical metal tube of infinite length. The external medium is homogeneous with finite conductivity. The expressions for the resultant fields are given explicitly for the case where the wall of the tube has a thickness small compared with the skin depth of the metal. A numerical example for magnetic dipole excitation is given for the case where the observer is in the external medium at the same level as the source. Not surprisingly, the results show that the metal casing in a borehole will have a severe shielding effect on the external fields.
On the electrostatic problem consisting of a charged nonconducting disk and a metal sphere
Authors: Asano Kazutoshi
Published: February 2003

It is well known that when a metal sphere proceeds toward a charged nonconducting disk, discharge might occur between them. For this configuration, the electrostatic problem was analyzed, namely, potential, field strength, and charge. Analytical solutions of the problem were obtained. Since the solution was not satisfactory for the calculation of the potential in a certain domain, a numerical approach is also discussed. Potential contours for a particular configuration were calculated and plotted.
Study of thermal desorption: The effect of a temperature gradient along the sample
Authors: Chiarena J. C. , Gillet E.
Published: February 2003

In thermal desorption techniques some difficulties may arise of a thermal gradient in the samples; the analysis of desorption spectra under this circumstance cannot be carried out by the usual methods. We give in the case of a parabolic thermal-gradient profile a procedure for analysis of a simple peak spectrum in a first-order desorption. As a first step we have evaluated the distortion of a theoretical desorption peak by the presence of a temperature gradient. This distortion was characterized by the quantities ΔTm/Tm and Δμ/μ, Tm and μ being, respectively, the maximum peak desorption temperature and the half-width of the peak at midheight. Utilizing some mathematical properties of the desorption rate equation we have shown that ΔTm/Tm and Δμ/μ can be plotted in terms of three independent parameters. The curves so obtained allow the experimental spectra to be corrected to determine the true values of the kinetic parameters: activation energy for desorption Ed and frequency factor 1/τ0.
Secondary electron emission from 0.5–2.5-MeV protons and deuterons
Authors: Thornton T. A. , Anno J. N.
Published: February 2003

Measurement of the secondary electron currents leaving Al, V, Fe, 316 stainless steel, Nb, and Mo foils undergoing 0.5–2.5-MeV proton and deuteron bombardment were made to determine the secondary electron emission ratios for these ions. The measured secondary electron yields were of the order of 1.0, with the deuterons producing generally higher yields than the protons.
Laser isotopic enrichment of boron using catalysis
Authors: Lin C. T. , Atvars T. D. Z. , Pessine F. B. T.
Published: February 2003

Laser photochemical isotope separation using catalysis is achieved for the first time. Mixtures of 10 Torr BCl3, 20 Torr H2, and ∼1 g Ti are irradiated with 10.55-μm radiation from a TEA CO2 laser. After 1.5 h of irradiation it is found that a 10% enrichment in the ratio of 10B/11B is obtained. The effect of a catalyst in the efficiency of isotopic enrichment is discussed.
Domain-wall energy measurements in Ni-Fe-Co films
Authors: Sanders Ian L. , Collins Alan J.
Published: February 2003

The domain-wall energy density σw in 65/15/20 Ni-Fe-Co films has been determined using the domain-tip propagation technique. The method involves the measurement of the threshold field for tip motion of a reverse domain in a low-coercive-force channel as a function of channel width. The two models of tip motion which have been proposed, viz, translation and tip elongation, give rise to different expressions for the propagation threshold and, consequently, different calculated values of σw. Experimental data show that the elongation model is preferable, and σw has been calculated using this model. The wall energy is presented as a function of film thickness in the range 600–2200 Å and is compared with theoretical values. The experimental results are found to be generally higher than the theoretical wall energy.
Diffusion of mercury in Ag2Hg3
Authors: Shires P. J. , Hines A. L. , Okabe T.
Published: February 2003

Volume and grain-boundary difusion coefficients of mercury in Ag2Hg3 were measured by the residual activity method at 50, 74, and 102 °C. The volume and grain-boundary diffusion coefficients may be expressed respectively as Dv=1.2×10−4 exp (−7.25×103/RT) cm2/sec and Dg=22.8 exp (−4.56×103/RT) cm2/sec. Grain-boundary diffusion coefficients, which varied from 2.07×10−2 cm2/sec at 50 °C to 5.32×10−2 cm2/sec at 102 °C, indicate that mercury dissolves the grain boundary of the Ag2Hg3 alloy.
Comments on the evaluation of the irradiance of reflected light from rough surfaces
Authors: Leader J. Carl , Fung A. K.
Published: February 2003

A recent communication provided numerical calculations of the simplified scattering integral and concluded that analytical approximations of this integral were valid only when a parameter Q was much less than unity. It is demonstrated that this conclusion is false and that the correct application of the approximate methods is determined primarily by the product of the wavenumber and the height deviation. The numerical calculations responsible for the erroneous conclusion are shown to be dominated by the coherent scattering component.
Flashover breakdown of an insulator in vacuum by a voltage impulse in the presence of a magnetic field
Authors: Golden J. , Kapetanakos C. A.
Published: February 2003

The flashover strength of Plexiglas insulators subjected to submicrosecond voltage impulses in vacuum and in the presence of a magnetic field that is perpendicular to the insulator surface is studied. Flashover breakdown strength is reduced by magnetic fields of a few kilogauss. Observation by fast-framing photography does not reveal curvature of the breakdown arc greater than 20°.
Changes in the superconducting critical temperature after fast-neutron irradiation
Authors: Brown B. S. , Hafstrom J. W. , Klippert T. E.
Published: February 2003

The decrease in the superconducting transition temperature Tc after fast-neutron irradiation has been measured in V2Hf (C-15 Laves phase), Nb3Al (A-15 phase), PbMo6S7 (Chevrel phase), and SnMo5S8 (Chevrel phase). The samples were irradiated at 6 K and warmed to 300 K during transfer to the measuring cryostat. The Tc of the samples was measured as a function of dose up to 3.0×1019 n/cm2 (E≳0.1 MeV). The different crystal structures showed a marked difference in the sensitivity of the Tc depression with irradiation. The total decrease in Tc of V2Hf was 5%, while ΔTc(Nb3Al) =23%, ΔTc(PbMo6S7) =61%, and ΔTc(SnMo5S8) =51%. Log(ΔTc) was linear with dose for all samples as expected for radiation saturation, i.e., the damage rate was proportional to the undamaged fraction. The recovery of Tc after a series of 5-min isochronal anneals up to 1200 °C has been measured, and the annealing stages observed are discussed in terms of the radiation-induced defects.
Zone-plate coded imaging on a microscopic scale
Authors: Ceglio N. M.
Published: February 2003

An experimental demonstration of the applicability of zone-plate coded imaging (ZPCI) techniques on a microscopic scale has been completed. The electron emission from microscopic test-pattern sources was imaged. Optically reconstructed images were compared with numerically calculated image distributions and the agreement was good. These experiments verified the theoretical resolution limit on a scale less than 10 μm, while also demonstrating the applicability of ZPCI to charged-particle imaging. This coded imaging technique appears well suited to high-resolution imaging of short-wavelength radiations (x rays and charged particles) from laboratory plasmas of limited size.
Infrared absorption in ThO2-doped Y2O3
Authors: Harrington James A. , Greskovich C.
Published: February 2003

The optical absorption has been measured over the 2–4-μm region in dense polycrystalline Y2O3 containing 10 mole% ThO2 in solid solution. Measurements of the absorption coefficient (β) in ThO2-doped Y2O3 indicated an intrinsic (multiphonon) level of 2.6×10−5 cm−1 at DF(3.8 μm) wavelengths although calorimetrically obtained β’s were in the low 10−3-cm−1 region for the best materials. This difference is attributed to extrinsic absorption mechanisms and, in particular, to an impurity band of as yet undetermined origin lying directly between the DF and HF frequencies. Various ceramic processing techniques were applied to sintered ThO2-doped Y2O3 ceramic to reduce this absorption with the most successful being a high-temperature anneal in a higher partial pressure of oxygen.
Photovoltaic properties of five II-VI heterojunctions
Authors: Buch Fredrik , Fahrenbruch Alan L. , Bube Richard H.
Published: February 2003

Five heterojunction systems, involving the II-VI compounds CdSe, CdTe, ZnSe, and ZnTe, have been prepared using the close-spaced vapor transport method. Current transport through these heterojunctions was found to be dominated by recombination at the interface. Using a collection function, introduced to describe the voltage dependence of the collection of photogenerated carriers, diffusion potentials were determined, and from them values of the electron affinity of CdSe (4.53 eV) and ZnTe (3.73 eV) relative to CdTe (4.28 eV).
Growth and properties of liquid-phase epitaxial GaAs1−xSbx
Authors: Nahory R. E. , Pollack M. A. , DeWinter J. C. , Williams K. M.
Published: February 2003

A detailed study is presented of the Ga-As-Sb ternary phase diagram. Liquidus temperatures have been measured between 700 and 900 °C by direct observation of the solutions, and layers then grown epitaxially on GaAs substrates. The nonequilibrium effect of constitutional supercooling on the compositions of the grown layers is investigated. Solidus compositions, from layers slowly grown to minimize this effect, are used together with the liquidus data to fit a calculated phase diagram. These results lead to the conclusion that GaAs1−xSbx is a borderline case between miscible and immiscible solid solutions. An accurate determination of the ternary band gap has been made as a function of composition over the range 0⩽x⩽0.2. The room-temperature electrical properties of undoped, Te-doped (n-type), and Ge-doped (p-type) epilayers have also been determined.
Background deep-level defects in VPE GaP
Authors: Wessels Bruce W.
Published: February 2003

Residual deep-level defects in vapor-phase epitaxial GaP were determined by transient capacitance spectroscopy. The dominant trap in the temperature range studied occurs at Ec−0.44 eV and was present in concentrations of (0.1–1.6) ×1014 cm−3. Two other traps were observed at the epitaxial-layer–substrate interface with energies of Ec−0.23 eV and Ev+0.51 eV. The capture cross section and concentration of these defects are also presented.
Morphology and size distributions of islands in discontinuous films
Authors: Andersson Thorwald , Granqvist C. G.
Published: February 2003

We have investigated sizes and shapes of islands in discontinuous gold films. These were UHV deposited in an electric field parallel with the surface of the glass substrates. Films with average thickness t in the range 10⩽t⩽45Å have been studied. The two-dimensional island shapes are represented by ellipses where, from experiments, both the major and minor axes obey log-normal distribution functions. These facts can be reconciled with a statistical model of island coalescence. Empirically, the median island diameter is approximately proportional to t, whereas the geometric standard deviation σ falls in the range 1.25⩽σ⩽1.30, irrespective of thickness. We define a mean eccentricity ē as an average over the ratio between major and minor axes; as expected ē increases with increasing t. Supplementing the size determinations with evaluations of area fraction of the substrate covered with metal we find the three-dimensional form of the islands to be accurately approximated by prolate spheroids (symmetry axes parallel with substrate plane). Finally, we have studied the role of field-induced coalescence which appears to be significant already at t=20 Å.
Analogue simulation of Josephson junction with linear-periodic current-phase relation
Authors: Gundlach K. H. , Kadlec J. , Heller W.
Published: February 2003

It is shown that an RCL sweep oscillator can serve as a simple analogue of a Josephson-like junction with linear-periodic current-phase relation. The presentation includes the ac Josephson effect, response to external rf signals and the hysteresis in the dc characteristic. The analogue has obvious value for instructional purposes and is useful where numerical analysis becomes complicated.
Magnetic surfaces in a dc toroidal octupole field under the influence of magnetic field perturbations
Authors: Rudmin J. W. , Meade D. M.
Published: February 2003

Calculations are presented which show the effects of magnetic field perturbations on toroidal multipole fields used for plasma confinement. The field topology was destroyed, with the attendant formation of magnetic surfaces. In contrast to earlier calculations, exact equations are solved numerically and the results apply to actual experiments in which the plasma lifetime was seriously decreased by the perturbing field.
A model for 1/f noise from singularities in the fluctuation weighting function
Authors: Weissman Michael B.
Published: February 2003

Noise with a 1/f (ω−1) power spectrum or a spectrum approaching ω−1 in the high-frequency limit is shown to result from thermodynamics and other stationary fluctuations in the neighborhood of certain types of singularities in the fluctuation weighting function. The limiting behavior of such ω−1 noise is shown to be essentially independent of the nature of the fluctuation transport mechanism. The transport dependence of noise which approaches ω−1 is described. Several plausible physical illustrations are presented.
Measurements of 400-MW/cm2 proton fluxes
Authors: Eichenberger C. , Humphries S. , Maenchen J. , Sudan R. N.
Published: February 2003

Proton current densities in excess of 1 kA/cm2 have been measured at the cathode in the center of a pinched-electron-beam diode. Efficiencies (Ii/I) of about 10% have been achieved to obtain in excess of 12 kA of ions. A surface breakdown plasma on the anode allows attainment of the pinched-beam equilibrium early in the voltage pulse. The peaking of the ion current density near the pinch roughly follows the theoretical predictions. Measurements were made with biased charge collectors. The theory of these probes has been reconsidered for the high-current-density limit, and it is shown that the probe response gives the actual ion current density independent of secondary emission processes on the collector.
Higher-order Bragg coupling in periodic media with gain or loss
Authors: Jaggard Dwight L. , Elachi Charles
Published: February 2003

We consider wave propagation in longitudinally periodic media with gain or loss. An extended coupled-waves (ECW) approach and Floquet approach are used to study index and gain (or loss) coupling in periodic media at the first few Bragg resonances by the use of Brillouin diagrams. Phase speeding or slowing that is dependent upon the type of coupling occurs in periodic media. Even and odd resonances display different dispersion characteristics. Several examples of coupling due to multiharmonic periodicities are also covered. Coupling or feedback strength can be continuously varied by changing the relative phase of multiharmonic periodicities.
Scattering by a dielectric-loaded trough in a conducting plane
Authors: Sachdeva B. K. , Hurd R. A.
Published: February 2003

A low-frequency solution to the diffraction problem of an E-polarized plane wave incident on a dielectric-loaded trough in a conducting plane is obtained. The dielectric loading consists of a circular cylinder which fits the semicircular trough in the conducting plane. The method used is a powerful low-frequency technique which has been succesfully applied to other problems of cylindrical geometry.
High photoemission efficiency of submonolayer cesium-covered surfaces
Authors: Wang Chen-Show
Published: February 2003

Long-wavelength photoemission current from Cs and O2 coadsorbed W (100) surfaces has been measured as a function of the amount of Cs and O2 deposition. Auger, work-function, and LEED measurements were used to monitor the exact amount of Cs and O2. We found that for different initial oxygen exposure a distinct maximum of photoemission efficiency exists at Cs coverage of φCs=0.229±0.3 (2.9×1014 Cs atoms/cm2), which is near but not at the well-known work-function minimum (φCs=0.25). The maximum photocurrent increases as the initial oxygen exposure increases. At optimum peak, the photoemission efficiencies are typically three to five times that of other Cs and O2 coverages.
Aggregation and migration of ion-implanted silver in lithia-alumina-silica glass
Authors: Arnold G. W. , Borders J. A.
Published: February 2003

The near-surface nucleation and crystallization behavior of Ag+ ion-implanted lithia-alumina-silica glasses has been studied. For room-temperature Ag implants, crystallization of the glass ceramic phase was prevented by dissolution of Ag precipitates and migration of Ag atoms at temperatures below that necessary for formation of the glass ceramic phase. Crystallization was demonstrated after low-temperature or low-dose-rate implantations. Optical spectroscopy was used to monitor the size of colloidal Ag particles and to detect the presence of the crystalline phase. Rutherford backscattering spectroscopy (RBS) was used to obtain the depth distribution of Ag atoms in the glass and thus monitor Ag migration. For samples implanted at room temperature and at relatively high dose rates (∼1 μA/cm2), aggregation of the Ag atoms into colloids occurred during implantation and also during subsequent annealing to temperatures ?350 °C. The RBS spectra indicate some migration of the Ag to the surface at these temperatures. For annealing temperatures ≳350 °C, both optical and RBS measurements show that Ag is lost from the glass surface. The initial spatial distribution of the Ag for these high-dose-rate room-temperature implantations was distorted by interactions with the associated damage and possibly by local electric fields caused by neutralization of the implanted ions. It was possible to obtain dispersed Ag nuclei by implanting at low sample temperatures (80 K) or at low beam current (∼200 nA/cm2) to reduce ion-beam heating. Although some migration to the surface was seen in these samples, it occurred at higher temperatures and crystalline precipitation was achieved by annealing at 500 °C.
Helium migration in lithium aluminosilicate glasses
Authors: Shelby J. E.
Published: February 2003

Helium permeation, diffusion, and solubility have been measured for a number of lithium silicate and aluminosilicate glasses. Helium mobility in the lithium silicate glasses is controlled by the two-phase morphology of these glasses. Addition of as little as 2 mol% alumina strongly suppresses the tendency toward phase separation, i.e., yields homogeneous glasses. The compositional dependence of helium mobility in these glasses indicates that a major change in the glass structure occurs when the alumina-to-lithia ratio exceeds unity. Comparison of these results to those for analogous sodium aluminosilicates indicates that lithium has a greater effect than sodium on the free volume of the glass.
Raman scattering measurement of the free-carrier concentration and of the impurity location in boron-implanted silicon
Authors: Beserman R. , Bernstein T.
Published: February 2003

Using Raman scattering we have measured the number of free carriers and the fraction of boron ions in substitutional positions, in boron-implanted silicon, as a function of the annealing temperature. After implantation, silicon is n type and becomes p type above 600 °C. The doping is governed at low temperatures by the annealing of defects and above 600 °C by the migration of boron ions into substitutional positions.
On the crystal structure of α′-cerium
Authors: Zachariasen W. H.
Published: February 2003

X-ray diffraction data for the high-pressure form of cerium metal recently published by Schaufelberger confirm that α′-Ce has the α-uranium structure as previously reported by Ellinger and Zachariasen. The pressure deduced from the α-Ce lattice constant is 9 kbar smaller than reported by Schaufelberger. At a deduced pressure of 43 kbar the unit-cell dimensions are a=4.621±0.003 Å for α-Ce and a=3.094±0.002 Å, b=6.007±0.004 Å, c=5.246 ±0.004 Å for α′-Ce with ΔV/V=−0.012.
A bond-orbital interpretation of the linear dielectric and magnetic properties of the ternary chalcopyrites
Authors: Lines M. E. , Waszczak J. V.
Published: February 2003

The bond-orbital theory developed for the elemental and binary tetrahedral semiconductors has been extended for application to the ternary chalcopyrite structure. Using only bond-orbital parameters defined and determined earlier for the corresponding binary systems we show that the theory is able to reproduce the known experimental data for the long-wavelength electronic contribution to refractive index of the ternary systems with a rms accuracy of the order of 3%. We also report the experimental measurement of room-temperature diamagnetic susceptibility for several chalcopyrites and use these data to test the bond-orbital theory in the magnetic context. Again, we find that the theory is able to reproduce the experimental data (this time with a rms accuracy of about 4%) using only parameters defined for the corresponding binary systems. Finally, we give the bond-orbital estimates for refractive index and diamagnetic susceptibility for the complete series of I-III-VI2 and II-IV-V2 ternary chalcopyrites.
Studies of surface composition of Ag-Au, Au-Cu, and Ag-Cu alloys after ion bombardment by Auger electron spectroscopy
Authors: Betz G. , Braun P. , Färber W.
Published: February 2003

Changes in the surface composition of the single-phase binary alloy systems Ag-Au and Au-Cu and the two-phase system Ag-Cu after sputtering with 1-keV Ar+ ions have been studied by Auger electron spectroscopy. A different behavior was observed for single-phase and two-phase systems. For the single-phase systems no change in surface composition can be detected after stopping sputtering. Therefore, the results in surface composition agree with those obtained during sputtering. However, for the two-phase system Ag-Cu the surface becomes enriched in Ag within a few minutes after prolonged ion bombardment is stopped. Assuming surface diffusion a simple model shows that the surface becomes covered by about one to two atomic layers of Ag, independent of the Ag bulk concentration. Furthermore, experiments with a 40 at.% Ag–60 at.% Cu sample indirectly heated to 350 °C indicate that surface diffusion is enhanced by radiation damage produced by ion bombardment.
Ion-implantation into As-diffused junctions in Si
Authors: Bogardus E. H.
Published: February 2003

Ion implantation into the n+ region of Si gated diodes gives leakage currents equivalent to unimplanted diodes after a 700 °C anneal and several orders of magnitude lower after a 900 °C anneal. It is suggested that the improvement in leakage current occurs due to gettering of metallic impurities from the depletion region.
Magnetic properties to TM80P20 glasses
Authors: O’Handley R. C. , Hasegawa R. , Ray R. , Chou C.-P.
Published: February 2003

Saturation magnetic moments (4.2 K), room-temperature magnetizations, and some Curie temperatures are reported for several TM80P20 metallic glasses (TM=Fe, Co, and Ni). These data complement previously published results for TM80B20 glasses and confirm the model in which approximately 2.4 and 1.6 electrons/metalloid atom are transferred by P and B, respectively, to TM d states.
The temperature variation of the thermo-optic coefficient of CaF2
Authors: Tsay Y. F. , Lipson H. G. , Ligor P. A.
Published: February 2003

We report measurements of dn/dT, the thermo-optic coefficient, i.e., the temperature derivative of the refractive index, for single-crystal CaF2 at temperatures ranging from 95 to 175 °K. Over this temperature range dn/dT shows a strong variation, with a substantial reduction in magnitude from that at room temperature. These data along with those obtained previously at room temperature indicate that dn/dT for this crystal is proportional to the thermal expansion coefficient over a wide temperature range and that the proportionality constant can be accurately obtained from the pressure dependence of the refractive index.
0.9-W Raman oscillator
Authors: Ammann E. O. , Decker C. D.
Published: February 2003

Substantial average output powers have been achieved from a Raman oscillator operating at kHz pulse repetition frequencies (PRF’s). The Raman oscillator is composed of a lithium iodate crystal placed inside a Nd : YAlO3 laser; feedback is provided at the Stokes wavelengths by means of mirrors surrounding the crystal. In separate experiments, we have obtained 900-mW average output power from the 1.18-μm first Stokes line at a 3.2-kHz PRF, and 200 mW average output power from the 1.31-μm second Stokes line at a 1-kHz PRF. Pulse lengths were approximately 6 and 2 ns for the 1.18- and 1.31-μm outputs, respectively.
Enhancement of laser machining and aging characteristics of thin metal films by means of a sensitizing layer
Authors: Lou D. Y.
Published: February 2003

On the basis of the Maxwell-Garnett theory, it is theoretically possible to change the optical constants of a material from its bulk values by reducing the size of grains surrounded by a dielectric, which may be its oxide, air gaps between the grains, or a substrate material. Thus, it should be possible, by controlling the nucleation characteristics of a film, to produce a layer of predominantly small-grain material in between the substrate and a normal large-grain layer. The different optical constants of the two layers can be utilized to reduce the reflectivity of the large-grain film when light is incident through a transparent substrate. This can lead to improved sensitivity in the laser machining of thin films. Such a layer of small-grain material may be produced by the preliminary deposition of a suitable sensitizing layer. Various 1.0% transmission films of the structure Celanar-Mg0.25In0.75-Bi have been studied. The sensitivity of the film systems to laser micromachining was evaluated with a Nd-YAG laser at 1.06 μm with 30-nsec-duration 6.8-μm-diam pulses. The most sensitive film system studied consists of a layer of 86% transmission Mg0.25In0.75, with enough Bi over it to make the film 1.0% transmitting. This system shows a threshold for laser machining of 6 nJ and requires 16 nJ to machine a 6-μm-diam hole. Film stability against changes in optical transmission is also improved.
Stresses in superconducting solenoids
Authors: Arp V.
Published: February 2003

This paper develops and summarizes analytical techniques for calculating radially dependent stress and strain in superconducting windings having anisotropic mechanical and thermal properties. The analysis considers stresses due to fabrication procedures, cooldown to helium temperature, and magnetic forces. Representative calculations for a particular superconducting coil are presented.
Untuned Josephson detectors of microwave and millimeter-wave radiation
Authors: So C. K. , Hamilton W. O.
Published: February 2003

The intrinsic response of Josephson junctions to microwave and far-infrared radiation is studied. Junctions are formed by pressing a Nb or Nb-Ti pointed wire onto a Nb thin film which in turn is pressed against the open end of a waveguide. Electromagnetic radiation is applied through the back of the film so that only the wave magnetic field is coupled to the junction. The change of the dc Josephson current is monitored at different levels of microwave power over a frequency range from 22 to 105 GHz. The dependence of the responsivity of these currents on film thickness over a range from 50 to 500 Å is studied. The observed responsivity agrees very well with that predicted by theory. Higher responsivity is observed for thinner films and lower microwave frequencies. The observed responsivity of a 50-Å film junction at 22 GHz is (6±3) ×10−2 V/W. To facilitate comparison of our results with other experiments, a more conventional coupling configuration in which the wave electric field rather than the wave magnetic field is coupled to the junction is studied. The results are comparable with other experiments with the responsivity in the E field coupling case 106 times larger than in the B field coupling configuration. We demonstrate that for successful use of simple Josephson junction detectors in the microwave and millimeter region it seems crucial to impedance match the junctions to the radiation source, probably by making them a part of a resonant structure.
Magnetic bubbles, walls, and fine structure in ion-implanted garnets
Authors: Puchalska I. B. , Jouve H. , Wade R. H.
Published: February 2003

The description and interpretation of bubbles with associated domains and charged walls in Sm YIG garnets implanted with H+ ions are presented. The nature of the contrast obtained with Bitter solution is shown to result from the polarization of the grains by the external bias field. The use of this contrast allows the determination of the direction of the magnetization in the plane of the film and perpendicular to it. The domain arrangements around the bubbles are found to be strongly dependent on the presence of an in-plane anisotropy. In the specimen studied here, the magnetocrystalline threefold symmetry and in-plane easy direction coming from a crystallographic tilt are predominent. The shape of the domains associated with bubbles changes significantly with the magnitude and the direction of the applied in-plane field. The structure can be interpreted in terms of the flux closure and bubble-wall configurations for the S=+1 states investigated here. The fine structure inside the bubbles is revealed and shown to be linked with external walls. The charged walls are attached to unimplanted disks. Their position, polarity, and shape are found to be highly dependent on the symmetry properties of the film as well as the characteristics of the applied in-plane field. Bubbles with charged walls of opposite polarity are strongly attracted to each other; however, a simple model based on magnetostatic interaction is found to be insufficient as the charged walls and the bubbles do not always rotate with exactly the same phase.
Self-pulsation in the output intensity and spectrum of GaAs-AlGaAs cw diode lasers coupled to a frequency-selective external optical cavity
Authors: Risch Ch. , Voumard C.
Published: February 2003

The laser emission of a cw diode laser coupled to an external cavity is self-pulsing at a frequency of 3–30 MHz, that is, two orders of magnitude lower than the resonance frequencies of the external cavity (typically 0.5 m long). The low-frequency self-pulsation is also present with a wavelength-selective external cavity using a grating as a reflector that narrows the laser emission to a single longitudinal mode. This paper describes some of the characteristics of the self-pulsation such as the pulse shape, the frequency dependence, the shift of the wavelength of the lasing mode during a pulse, and their dependence on the wavelength selection by the grating.
Numerical calculation of elastically deposited energy by energetic heavy ions in multicomponent materials
Authors: Matsutani Yoshikazu , Ishino Shiori
Published: February 2003

Based on the LSS theory, elastically deposited energy and its partition to each atomic constituent of a binary system by energetic heavy ions are numerically calculated. The target is TaO, and the projectiles are He, Be, C, O, Al, Ar, Fe, Kr, Ta, and Bi ions with energies up to 400 keV. It has been shown that the ratio of partial damage energy imparted to each atomic species to total damage energy remains constant and does not depend on the atomic species of the projectiles for the high-energy region. For intermediate and low energies, however, this ratio depends appreciably on the boundary condition, energy, and the nature of the projectiles. These results have been compared with the work of Andersen and Sigmund, and the correlation between them are discussed. A generalized relation as to the partition of damage energy in multicomponent cases is also suggested.
The yield stress of opposed anvils
Authors: Dunn Keh-Jim
Published: February 2003

The Lur’e solution for an elastic cone has been integrated to give a more reasonable solution of the state of stress of a Bridgman anvil. The maximum shear stress at the center axis is plotted as a function of the tapered angle. It shows that with a smaller tapered angle the anvil gives higher pressure before it plastically yields. It is estimated the maximum pressure can be achieved in a Drickamer-type apparatus with pistons made of maraging steel is around 85 kbar and that of cemented tungsten carbide is around 300 kbar. Based on published claims of achieved pressures, the maximum pressure capability of sintered-diamond compact is greater than 1.2 Mbar and that of a single-crystal diamond could possible be as high as 3.2 Mbar.
A diffraction study of the substructure in cold-worked Ni3Al
Authors: Arnoth F. W. , Clark J. P. , Mohanty G. P.
Published: February 2003

A study of the substructure in cold-worked Ni3Al (Ll2) phase was performed employing x-ray powder diffraction technique. Analyses of the peak shapes, positions, and intensities of the fundamental and superstructure reflections show the importance of several substructural features, including especially the a/6 {211} {111}-type single-layer and multilayer stacking faults following deformation at the liquid-nitrogen temperature. Atomic disorder and antiphase boundaries on {111} and {100} also occur in the cold-worked material; however, these are not as prominent as those reported in the Cu-based L12 phases under comparable or less severe deformation conditions. An attempt to determine the importance of the low-energy a/3 〈211〉 {111}-type stacking fault on the basis of the limited number of superstructure reflections available in the powder pattern shows it to be less significant in the low-temperature-deformed material compared to the usual a/6 〈211〉 {111}-type intrinsic fault, although the latter has a higher energy in the Ll2 structure.
Transmission characteristics of Bleustein-Gulyaev waves at a corner
Authors: Tanaka K. , Kawasaki Z.
Published: February 2003

This paper describes a theoretical study of the diffraction of Bleustein-Gulyaev waves at a corner of a homogeneous elastic wedge formed by two stress-free and metalized planes. First, an integral representation theorem is obtained for shear horizontal elastic waves in a semi-infinite piezoelectric medium, on the assumption that the surface of the medium is coated with an infinitely thin conducting layer. Then, with the use of an integral equation method, the problem of the diffraction of Bleustein-Gulyaev waves at a given corner is formulated. With first-order approximations, the transmitted Bleustein-Gulyaev waves and diffracted bulk shear waves are obtained. To obtain a qualitative idea of the propagation characteristics of Bleustein-Gulyaev waves at a corner, numerical illustrations of the transmission coefficient for Bleustein-Gulyaev waves are shown together with those of the diffracted power and diffraction pattern for the bulk shear waves.
On the growth of stacking faults and dislocations induced in silicon by phosphorus predeposition
Authors: Armigliato A. , Servidori M. , Solmi S. , Vecchi I.
Published: February 2003

The growth of extrinsic stacking faults associated with SiP platelets induced by phosphorus predeposition in thin silicon foils has been followed by transmission electron microscopy. The role of the precipitates and of the phosphorus diffusion on the climb of the Frank partials is discussed. Unfaulting reactions, observed to annihilate isolated extrinsic Frank loops, are assumed to take place also in the case of the stacking faults associated with precipitates, resulting in the generation of 60° perfect dislocations, which have been revealed by x-ray topography. Different climb rates for the 60° dislocations have been observed after predeposition experiments performed by varying the oxidation and the phosphorus-doping kinetics; the relationship between these two parameters and the vapor partial pressures of the gas flowing in the furnace has been obtained as a result of careful experimental work. From the results of all our experiments, it has been deduced that the ingoing phosphorus, rather than the associated oxidation, is the main factor responsible for the climb of both partial and unit dislocations. The growth of these defects is attributed to the interstitial supersaturation produced at the interface Si-SiO2 by the phosphorus atoms entering the silicon lattice.
Annealing of irradiation-induced defects in arsenic-doped silicon
Authors: Evwaraye A. O.
Published: February 2003

The annealing of the E3 (Ec−0.30 eV) and E4 (Ec−0.42 eV) defect levels in electron-irradiated arsenic-doped silicon has been studied by deep-level transient spectroscopy. The annealing studies of the E4 defect level in the diffused junctions indicate first-order kinetics with activation energies of 1.40 and 1.38 eV for the neutral and negative charge state of the defect, respectively. Even though the activation energies for thermal anneal at the two annealing modes are practically equal, charge state effects are operative. A secondary defect level E5 (Ec−0.24 eV) appeared in the spectrum during the annealing of the diffused p+nn+ junctions. The growth of E1 (Ec−0.17 eV) as the E4 defect anneals out seems to suggest that dissociation is the dominant process by which E4 is removed from the system.
Mechanical properties and microstructure of sintered PVC powder. I. Elastic properties and porosity
Authors: Behrens E. W. , Butto A. M.
Published: February 2003

Torsion-pendulum measurements were carried out with a variously sintered PVC powder of two different DOP-plasticizer concentrations. Aluminum foils were used as substrates for supporting the fragile specimens in the torsion pendulum. Based on a recently developed analysis, storage and loss shear moduli of the sintered powders were calculated from the experimental torsional rigidities of the laminated test specimens for a wide range of porosities and temperatures. The unrelaxed (glassy) shear modulus correlated well with density. After accounting theoretically for the porosity effect on the modulus, the latter was used for characterizing the internal cohesion of the material as it varies with the degree of sinter.
Crystallization kinetics of amorphous germanium
Authors: Germain P. , Squelard S. , Bourgoin J. , Gheorghiu A.
Published: February 2003

The variation of conductivity in amorphous germanium layers, due to crystallization, has been studied. The fraction which has crystallized is deduced from the variation of conductivity. Depending upon the conditions of preparation, the crystallization is induced at germanium-substrate interface (around 380 °C) or in the bulk (around 450 °C). The interpretation of the variation with time of the crystallized fraction, in terms of surface or bulk induced crystallization, allows the determination of the growth rate and of the initial concentration and size of the crystallites. The variation with the temperature of the growth rate is in good agreement with previously published results. The value found for the initial size of the crystallites is confirmed by electron microscopy observations.
Observation of anodic oxide-film growth on GaAs by i
n s
i
t
u differential reflectance
Authors: Moritani A. , Kubo H. , Nakai J.
Published: February 2003

The anodic film growth on GaAs during the anodization process and the dissolution of the grown film in the open-circuit condition have been observed with the in situ differential reflectance technique. It is shown that the dissolution curve of the grown film is useful in characterization of the film rather than the anodization curve. The anodic process in the open-circuit transient region is discussed.
An electron microscope study of Sm-Co-Cu–based magnetic materials with the Sm2Co17 structure
Authors: Melton K. N. , Nagel H.
Published: February 2003

In an electron microscope study of aged Sm-Co-Cu–based magnetic materials with the Sm2Co17 structure, it is shown that the previously reported coercivities of these materials are a consequence of the presence of very fine precipitates of the Cu-containing SmCo5 phase which act as pinning centers. In comparing the microstructures of alloys with different Sm/Co,Cu ratios, and with some Co replaced by Fe, a marked difference is observed both in the precipitate morphology and the fault density of the matrix phase. Possible reasons for this are discussed, and it is shown that the lattice misfit has a marked effect on the morphology.
Optically pumped atomic mercury photodissociation laser
Authors: Komine H. , Byer R. L.
Published: February 2003

We have generated superfluorescent laser action in atomic mercury at 0.546 and 0.365 μm by optically pumping Hg2 with 0.266-μm radiation. Superfluorescent thresholds were observed at less than 6 mJ/cm2 input energy density in a 5-nsec pulse for an atomic mercury density greater than 3×1018 cm−3.
Thermo-optical instabilities and bistable behavior with the frequency-doubled Nd : YAG laser
Authors: Barry J. D. , Kennedy C. J.
Published: February 2003

The operation of the frequency-doubled Nd : YAG laser may be affected by the thermo-optical distortion in intracavity elements. A theoretical model of the laser has been developed which couples the thermo-optical effects in the frequency-doubling crystal and the laser parameters. Oscillatory behavior and bistable power level operation are predicted. The model is supported by experimental data.
Calculated stresses in multilayered heteroepitaxial structures
Authors: Olsen G. H. , Ettenberg M.
Published: February 2003

A useful closed-form expression for stresses within individual layers of a multilayer composite has been obtained as a function of position within the layer. Equal and isotropic elastic constants were assumed in the calculation, although the error introduced by this assumption is found to vary by no more than the difference in elastic constants. Unequal elastic constants may be handled via computer solutions. The stresses within heterojunction AlxGa1−xAs/GaAs lasers are calculated as an example of the technique. The addition of Al to the active GaAs region is shown to have a drastic effect upon the active-region stress, changing it from tension to compression. This change of sign in stress is correlated with improvements in operating lifetimes of lasers.
Diffusion length determination in thin-film CuxS/CdS solar cells by scanning electron microscopy
Authors: Oakes J. J. , Greenfield I. G. , Partain L. D.
Published: February 2003

Minority-carrier diffusion lengths on both sides of the CuxS/CdS heterojunction in polycrystalline thin-film solar cells were determined from the decay of the short-circuit current generated by a 20-keV electron beam traversing the junction. The measured diffusion lengths in the low-field regions of these cells ranged from 0.11 to 0.57 μm for electrons in the p-type cuprous sulfide and from 0.07 to 0.31 μm for holes in the n-type cadmium sulfide. Uncertainties introduced by surface recombination effects, internal fields, and experimental accuracy specified that the actual bulk diffusion lengths could range from 0.09 to 1.71 μm for minority electrons in the cuprous sulfide and from 0.06 to 0.44 μm for minority holes in the cadmium sulfide. Measurement and analysis errors were estimated to cause bulk diffusion lengths to differ from measured values by less than the worst case limits of +200 and −31%.
Recombination centers in aluminum-doped silicon diffused in high phosphorus concentration
Authors: Marchand Raymond L. , Stivers Alan R. , Sah C. T.
Published: February 2003

Deep level recombination centers were observed in aluminum-doped silicon after high-temperature diffusion at high phosphorus surface concentration from thermally stimulated capacitance measurements on n+p and Mg on p-Si Schottky barrier diodes. Three-hole traps at EV+214 meV, EV+312 meV, and EV+392.5 meV were observed in good agreement with earlier measurements made on Schottky barriers. Profile measurements indicate that the phosphorus n+ layer is a sink for the recombination centers which are aluminum-oxygen complexes. The complexes dissociate at 1150 °C and the diffusivity at 1150 °C is (4.4±0.2) ×10−11 cm2/sec which is consistent with the published oxygen diffusion coefficient.
Nucleation and pinning at 360° domain walls in SmCo5 and related alloys
Authors: Gaunt P. , Mylvaganam C. K.
Published: February 2003

It is shown that in a high forward field neighboring 180° ferromagnetic domain walls come together and either annihilate one another (’’unwinding walls’’) or combine to form 360° walls separating domains magnetized in the same direction (’’winding walls’’). If the 360° wall encounters:i an inhomogeneity of lower zero-field wall energy (∞𝒵AK), it may be pinned. A finite reverse field is then required to split the 360° wall nucleus into two transient 180 ° walls which will reverse the magnetization. The model is developed micromagnetically and applied to the pinning of domain walls at grain boundary inhomogeneities in SmCo5 alloys. The nucleation–unpinning coercive field is calculated for inhomogeneities which are assumed to have the magnetic properties of pure cobalt. Inhomogeneity widths from 55.6 to 204 Å give coercive forces from zero to 3.8×104 Oe..A critical constants chosen, this thickness is 55.6 Å It is suggested that one function of liquid-phase sintering may be to increase the inhomogeneity thickness beyond the critical value.
Measurements of the elastic stiffness constants of single-crystal SmCo5 and of liquid-phase sintered SmCo5 permanent magnet material
Authors: Doane D. A.
Published: February 2003

The five elastic stiffness constants were determined for both single-crystal SmCo5 and for the commercially processed liquid-phase sintered (LPS) SmCo5 permanent magnet material. The LPS material is an aligned polycrystalline aggregate of SmCo5 crystallites oriented so that their magnetically easy c axes are approximately parallel. The elastic constants were obtained from the velocities of propagation of ultrasound in various directions in samples of known thickness and density. For the single crystal, the room-temperature values of the constants (in units of 1012 dyn/cm2) are c11=1.968±2%, c12=1.032±4%, c13=1.049±4%, c33=2.398±2%, and c44=0.483±2%, and for the LPS permanent magnet material, c11=1.330±2%, c12=0.616±5%, c13 =0.485±5%, c33=1.659±2%, and c44=0.419±2%. The decrease in elastic constants in SmCo5 relative to cobalt can be related qualitatively to a corresponding decrease in the number of nearest-neighbor cobalt bonds in SmCo5.