bluuebunny/crossref_metadata_2025 huggingface dataset:
Steady-state and rf properties of proximity effect weak links
Authors: McNamara R. P. , Mercereau J. E.
Published: February 2003

A detailed experimental examination of the dc critical supercurrent density jc and the microwave (nonzero voltage) supercurrent jμ has been made in proximity effect thin-film weak links at temperatures above the transition temperature of the link material. These results were correlated with measured dimensional and superconducting parameters of the thin films and the link via a Ginzberg-Landau (GL) formalism. In the steady state, jc was found to be adequately described by a one-dimensional GL formalism similar to that of Likharev and Yakobson but with De Gennes boundary conditions on the order parameter applied at each interface. However, jμ decreases exponentially with increasing voltage and can be interpreted in terms of an interference modulation of the induced pair density within the line at the Josephson frequency.
Current-voltage characteristics and composition profiles of Ni-Pt silicide Schottky diodes
Authors: Shepela A. , Phaneuf R. , Kennedy E. F.
Published: February 2003

The forward current-voltage (If-Vf) characteristics of (50 wt% Ni– 50 wt% Pt) silicide Schottky diodes, formed in vacuum at 425 °C from rf sputter-deposited Ni and Pt thin films, were found to be dependent on the metal-deposition sequence. From the thermionic emission equation an empirical barrier height of 0.70 eV was calculated for diodes formed from 125 Å Pt/325  Å Ni/(111) Si, while diodes formed from 325 Å Ni/125Å Pt/(111) Si had an empirical barrier height of 0.65 eV. The deposition of a thin W-Ti diffusion marker film on the Si surface before sputter deposition of Ni and Pt layers modified If-Vf characteristics. Silicide diodes formed from 125 Å Pt/325 Å Ni/(W-Ti)/(111) Si had an empirical barrier height of 0.66 eV. Diodes formed from 325 Å Ni/125 Å Pt/(W-Ti)/(111) Si had an empirical barrier height of 0.70 eV. MeV 4He+ backscattering spectra revealed that diodes with similar If-Vf characteristics had similar Ni and Pt concentration profiles in the silicide film.
Theoretical modeling of time-dependent cataphoretic gas separation in direct-current gas discharges when end volumes are present
Authors: Metze Armin , Chanin L. M.
Published: February 2003

A theoretical model describing time-dependent cataphoretic gas separation in a direct-current glow discharge with end volumes present is formulated for a binary gas mixture. It is shown how this theoretical model differs from the previous model developed by Shair and Remer. Computed results of the axial impurity density profile for three different end volume configurations based on the new model are presented and discussed. The results indicate that optimum cataphoretic gas separation is attained for large cathode to anode end volume ratios.
Temporal and spatial spectroscopy of the plasma formation in crossed electric and magnetic fields
Authors: Miljević V. I. , To?ić D. Dj.
Published: February 2003

The formation of argon plasma in crossed electric and magnetic fields in a cylindrical diode with an incandescent cathode has been studied by means of the delay time of the anode current pulse and photon pulse (corresponding to the optical transitions) and the shape of the voltage collapse. The working conditions were: pressure p=10−5–10−3 Torr, anode voltage Ua=800 V, and maximum magnetic field Bmax=1200 Gs. Photoelectrical recording of spectral lines was performed with a monochromator in the wavelength range 3600–6000 Å, and the total optical spectrum was recorded simultaneously on a photoplate in a separate spectrograph in the wavelength range 2000–10 000 Å. The delay time of the anode current pulse and photon pulse are approximately the same and are in the millisecond range. The delay time of the photon pulse does not depend on the wavelength. Simultaneously the spectral lines of the working gas (A II), residual gas (O II), and tungsten (W I) appear. Tungsten atoms appear at the moment of breakdown as a result of ion bombardment of the cathode. Neutral atomic lines of the working gas (A I) have not been observed. Radial analysis shows that the delay time of the photon pulse does not depend on the radius. Spectroscopic results have been analyzed in terms of excitation and ionization processes during the formation time. The shape of the voltage collapse suggests the streamer breakdown mechanism.
Observations on a medium energy field emission diode
Authors: Boscolo Ilario
Published: February 2003

The results of a diode fed by a medium energy pulsed electron gun are reported. Brief explanations of several behaviors of the electron emission from cold cathodes and electron flow in the diode region with energy in the range of 20–100 keV are presented.
Reaction of hydrogen with hydroxyl-free vitreous silica
Authors: Shelby J. E.
Published: February 2003

The reacton of hydrogen with hydroxyl-free vitreous silica has been measured for temperatures between 500 and 850 °C, pressures between 0.132 and 5.78 atm, and sample thicknesses between 0.057 and 1.06 cm. The results can be explained by a simple model often used to explain tarnishing reactions. This model assumes that the reaction rate is very fast compared to diffusion, and that a fixed concentration of trapping sites exists in the specimen.
A new method for analyzing 1st and 2nd order desorption spectra and glow curves
Authors: van Gorkum Aart A.
Published: February 2003

A new method to analyze 1st- and 2nd-order reaction rate curves as appearing in, e.g., thermal desorption and thermoluminescence is described. It is based on the concept of the ’’characteristic time’’ ψ of the process. It is shown that for constant temperature and hyperbolic heating schedules, the reaction rate depends on ψ only, while for the linear temperature sweep there is also a slight dependence on E/kTm with Tm being the peak temperature. The method is based on these facts, and, contrary to previous methods, makes use of all experimental data points, yielding both activation energy and frequency factor. The new method is demonstrated for a thermal desorption and a thermoluminscence peak.
Remote polar phonon scattering in Si inversion layers
Authors: Moore B. T. , Ferry D. K.
Published: February 2003

The effects upon the drift velocity and electron temperatures in silicon inversion layers due to interfacial polar-mode phonons in the Si/SiO2 interface have been calculated at various temperatures. These calculations were carried out at 77, 150, and 300 K using a three-energy-level model for transport in the quasi-two-dimensional inversion layer assuming a drifted-Maxwellian distribution. The effects of the polar interface phonon scattering are compared to the effects of scattering due to Si bulk phonons, interface charges, and interface roughness. The effects of the remote phonons are found to be small in the drift velocity, but are significant as an energy relaxation mechanism at high fields and large inversion densities.
The influence of clustering on the anisotropy of the solid/liquid interfacial free energy
Authors: Nason D.
Published: February 2003

It is proposed that roughening models of the solid/liquid interface in pure systems should be modified to require a minimum degree of clustering among solid states and among liquid states. An approximate treatment is developed in terms of a minimum cluster size and applied as an amendment to the Temkin treatment. The effect on the anisotropy of the interfacial free energy is presented as a function of the entropy of melting of the substance, the minimum cluster size, and the interface orientation parameters. It is concluded that roughening effects eliminate cusps in the γ plot for planes of comparatively high Miller indices and enshallow the cusps of planes of low Miller indices.
Oxidation of polycrystalline indium studied by x-ray photoelectron spectroscopy and static secondary ion mass spectroscopy
Authors: Hewitt R. W. , Winograd Nicholas
Published: February 2003

The chemisorption of oxygen on clean polycrystalline indium surfaces is investigated by the combined techniques of x-ray photoelectron spectroscopy (XPS) and the static mode of secondary ion mass spectroscopy (SIMS). Oxygen uptake is characterized by a moderately rapid formation of In2O3, with no preoxidation adsorbed O2 phase discernable in the XPS spectra. A high binding energy O (1s) peak becomes prominent after one monolayer of In2O3 has formed, which we ascribe to adsorbed oxygen on the oxide. Formation of In2O3 continues into the bulk either via migration of the adsorbed oxygen through the oxide layer to the metal-In2O3 interface or by the outward migration of indium cations to the surface. Both the formation of oxide and the onset of adsorption are reflected in the secondary ion yield ratios InO−2/InO− and O−2/O−. The behavior of SIMS molecular cluster ion yields with oxygen exposure are consistent with recent theoretical calculations of the cluster formation process, in which considerable local atomic order of the surface is present in the cluster.
Silicon molecular beam epitaxy with antimony ion doping
Authors: Sugiura Hideo
Published: February 2003

A new method of ionized antimony doping of silicon molecular beam epitaxial films has been investigated. Si films were grown on Si (111) substrates by evaporation of Si from an e-gun evaporator in ultrahigh vacuum. Sb ions were generated with an electron impact ion source. Carrier concentration of doped layers, grown at a substrate temperature of 860 °C, can be accurately controlled over the range 1016–1020 cm−3. Doping efficiency of Sb ions is 100%. Doping with ions in the range 130–1000 eV kinetic energy does not degrade the crystallographic or electrical quality of the films. For example, abrupt changes in the doping level of a composite film with three doped layers are given. The in-depth Sb dopant profile of this film corresponds closely to the Sb ion doping schedule, which indicates that the surface segregation of Sb does not occur attendant ion doping.
High-field electron transport in silicon-on-sapphire layers
Authors: Cook R. K. , Frey Jeffrey
Published: February 2003

Velocity-field curves for n-type silicon on sapphire have been measured at fields up to 60 kV/cm using pulsed I-V techniques and specially designed test structures. Successive etching was used to determine the dependence of drift velocity on distance from the silicon-sapphire interface. Within experimental error, the drift velocity of electrons is found to saturate at the same value as in bulk silicon, although the field required to achieve saturation is greater than in bulk Si and increases with decreasing Ohmic mobility near the interface. Sample heating can have a large effect on the experiment. The results, which are important for the design of high-speed SOSFET’s are explained using simple hot-electron physics.
Longitudinal instabilities of pulseline driven neutralized linear ion accelerators
Authors: Humphries Stanley
Published: February 2003

Linear accelerators driven by pulse forming networks and utilizing beam neutralization may be useful for obtaining high-current ion beams for inertial fusion applications. Such accelerators may be subject to longitudinal velocity bunching instabilities. These instabilities are studied with a computer simulation of longitudinal ion dynamics. It is found that they are stabilized by a velocity spread in the beam distribution determined by the properties of the pulselines. The required velocity spread does not preclude obtaining beams of sufficient quality for fusion applications.
Guiding mechanisms controlled by impurity concentrations—(Al,Ga)As planar stripe lasers with deep Zn diffusion
Authors: Ueno M. , Yonezu H.
Published: February 2003

The waveguiding characteristics in a (Al, Ga) As double-heterostructure laser, where a built-in refractive-index profile in the active layer is introduced by impurity concentration profile, have been investigated under the lasing conditions using the planar stripe laser with deep Zn diffusion. The effective refractive-index step, which determines the waveguiding mechanism, consists of the built-in refractive-index step and a negative index step associated with injected electrons into the active region. It has been found that waveguiding characteristics can be changed from antiguiding tendency to normal guiding by varying the combination of hole and electron concentrations.
Characteristics of a UF6-H2/HF nuclear-pumped laser
Authors: Kushner M. J.
Published: February 2003

Nuclear pumped lasers are characterized by high-threshold neutron fluxes and low gain. This is due primarily to the fact that the fissile gas, which has the largest partial pressure and hence has the largest fraction of fission energy deposited in it, is not the lasing species. The closer the fissile gas can be coupled to the actual lasing process, the more efficient the laser will be. In this paper, a model for a potential new nuclear-pumped HF laser is presented. Using a 235UF6-H2 gas mixture, a peak gain of about 50%/m and a threshold neutron flux of <1014/cm2 s are predicted. Recommendations are made concerning optimum use of the new system.
The multipass amplifier: Theory and numerical analysis
Authors: Lowdermilk W. H. , Murray J. E.
Published: February 2003

Theoretical and numerical analysis of the multipass amplifier illustrates its flexibility in applications ranging from efficient high-power pulse amplification to short-pulse generation with great amplitude and pulse-width stability.
Studies of the single-mode and multimode cw dye lasers as sources for obtaining power-squared corrected two-photon spectra
Authors: Johnson M. C. , Lytle F. E.
Published: February 2003

The single-mode and multimode free-running dye lasers are examined as possible sources for generating power-squared corrected two-photon absorption spectra. The observed differences between the two sources is attributed to the presence of mode noise in the multimode output, which yields inaccuracies in spectra when used as a source for two-photon spectroscopy. Using an accurate reference spectrum generated with the single-mode source, the utility of ratioing to obtain accurate spectra with the multimode laser is demonstrated. Alternate techniques for obtaining power-squared corrected two-photon spectra with the multimode laser are considered.
Structures and SAW properties of rf-sputtered single-crystal films of ZnO on sapphire
Authors: Mitsuyu T. , Ono S. , Wasa K.
Published: February 2003

Single-crystal films of ZnO have been epitaxially grown on the (0001) and (011̄2) planes of sapphire by rf sputtering. Crystalline structures and electrical properties of the films were investigated. Surface acoustic wave (SAW) properties, including a phase velocity, a coupling coefficient, a propagation loss, and a temperature coefficient of delay, were measured for SAW propagating along the c-axis of the ZnO films, on the (011̄2) planes of sapphire. Availability of this structure for high-frequency SAW devices has been demonstrated by a filter with a 1050-MHz center frequency.
Experimental measurements of time-dependent cataphoretic gas separation in a direct-current glow discharge when end volumes are present
Authors: Metze Armin , Chanin L. M.
Published: February 2003

A study has been made regarding the influence of end volumes on time-dependent cataphoretic gas separation in the positive column of a dc glow discharge containing 0.05% neon in helium. The neon 5400-Å-line intensity was monitored at several fixed points within the positive column of the discharge. The experimental data are compared with theoretical predictions based on the model formulated in the concurrent paper. The simplified model predicts the general features of time-dependent cataphoretic gas separation for the two end volume configurations considered.
Deuterization of synthetic quartz
Authors: Koumvakalis Nicholas , Markes Mark
Published: February 2003

Conditions sufficient for the electrolytic exchange of D+ for H+ ions in synthetic quartz are established. The deuterium-swept quartz crystals are characterized by electron paramagnetic resonance and infrared absorption.
1/f noise in Hall effect: Fluctuations in mobility
Authors: Kleinpenning T. G. M.
Published: February 2003

From theoretical and experimental investigations on 1/f noise in the Hall voltage at high magnetic induction it is concluded that 1/f noise is caused by mobility fluctuations.
Enhanced secondary electron emission yield from doped vanadate-phosphate glasses
Authors: Flinn E. A. , Salehi M.
Published: February 2003

Previous measurements of secondary electron emission from vanadate-phosphate glasses, using extremely clean surfaces, suggest that where these materials are used in practice as secondary emitters, surface contamination by materials such as cesium plays an important role. Samples of glasses containing significant quantities of cesium in the initial melt were manufactured, and did indeed show increases of 50% or more in the secondary electron emission yield. The yield increased monotonically with cesium content for all samples tested. The inelastic reflection coefficient for these materials was high—about 0.2. Similar materials containing sodium rather than cesium behaved very similarly where the V2O5 content was 60% or more, although the reflection coefficient was lower—about 0.1. Where the V2O5 content was less than 60%, however, high sodium concentrations produced a drastic fall in yield. V2O5-P2O5-Cs2O or V2O5-P2O5-Na2O glasses are easily manufactured by the same techniques as V2O5-P2O5 materials, and in view of their increased secondary electron emission coefficient, they should prove useful as secondary emitters in a variety of applications.
Piezoresistive effects in thick-film resistors
Authors: Canali C. , Malavasi D. , Morten B. , Prudenziati M. , Taroni A.
Published: February 2003

Piezoresistive properties of thick-film resistors obtained with ink series supplied by different manufacturers have been investigated as a function of composition, structure, sheet resistivity, and applied strain between 0 and ±1000 μ strain. The strain sensitivity of thick-film resistors appears to be a strong function of the nature of the conductive grains and of the sheet resistivity of the paste; the results obtained suggest a dominant role of the tunneling effect in the conduction mechanism and in the strain sensitivity.
Are impurities the cause of ’’self’’-compensation in large-band-gap semiconductors?
Authors: Neumark G. F.
Published: February 2003

A possible role of impurities in the well-known difficulty of obtaining well-conducting large-band-gap material is investigated. Specifically, the limitations imposed on carrier concentrations by chemical equilibrium considerations are analyzed for a (model) system of a single amphoteric impurity. It is also shown that energies of formation of at least some Group-I interstitials in a typical II–VI semiconductor, ZnSe, are expected to be low compared to those of native donor defects. Since Group-I impurities act as acceptors on a metal substitutional site, but as donors when on a interstitial site, a stable interstitial form results in amphoteric behavior and thus in constraints on achievable carrier concentrations if such impurities are present either deliberately or accidentally.
Self-consistent potential calculation for a magnetized electron beam flowing through a cavity
Authors: Genoni T. C.
Published: February 2003

A self-consistent, steady-state potential calculation is performed for a hollow, magnetized electron beam flowing in a cylindrical drift tube interrupted by a cavity. The dependence of limiting current on cavity length is also investigated.
E-beam initiated discharges in high-pressure Hg vapors
Authors: Schlie L. A. , Jusinski L. E. , Rathge R. D. , Drummond D. L. , Hamil R. A.
Published: February 2003

Studies are reported of stable glow discharges in high-pressure Hg vapors (?2 amagats) produced by a 20-nsec ionizing electron beam pulse. The discharges were very stable and operated for 4–5 μsec after the e-beam initiating pulse at E/N values up to 8×10−17 V cm2 and discharge current densities of 4 A/cm2. Power loadings of 3–6 kW/cm3 were typically obtained. An electron recombination coefficient of 7.4×10−9 cm3 sec−1 was measured. Strong continuum radiation from both the visible (4900 Å) and UV (3350 Å) bands of molecular Hg were observed. Absorption measurements from 4000 to 6764 Å are presented. No gain in this spectral region was ever detected. A peak absorption cross section at 4800 Å was estimated to be 2×10−16 cm2. The implication of this absorption on other potential laser systems employing Hg as a buffer gas are discussed.
Analysis of the anode boundary layer of high intensity arcs
Authors: Dinulescu H. A. , Pfender E.
Published: February 2003

A one-dimensional analysis of the anode boundary layer of an atmospheric pressure, high intensity argon arc reveals substantial deviations from local thermodynamic equilibrium (LTE) in this layer. The temperature of the heavy species approaches the temperature of the anode in the immediate vicinity of the anode surface, whereas the electron temperature remains sufficiently high to ensure the required electrical conductivity. Temperature and density gradients in the anode boundary layer contribute substantially to the electric current flow so that the potential drop across the boundary layer becomes negative. The main voltage drop, which is in the order of 1 V, is essentially confined to the sheath at the bottom of the boundary layer overlying the anode surface. The thickness of this sheath is several orders of magnitude smaller than the anode boundary layer and the potential drop in the sheath is also negative. Therefore, the anode fall becomes negative for the entire parameter range covered in this paper, in contrast to the results of previous theories. This finding affects the anode energy balance as well as the interpretation of indirect (calorimetric) anode fall measurements which is important for the design of arc gas heaters.
Influence of growth parameters on CdTe low temperature thermal conductivity
Authors: Jouglar J. , Hetroit C. , Vuillermoz P. L. , Triboulet R.
Published: February 2003

The conditions of the growth of single crystals of CdTe produce marked changes in their thermal conductivities. This study shows the influence of some specific parameters of the growth conditions: (i) material purity, and (ii) growth temperature and growth rate on the microprecipitate concentration (S?1014 cm−3 with a?100 Å) in CdTe obtained by the ’’traveling heater method’’. An upper limit of the homogeneity region is deduced that takes into account all the defects, including nonelectrically active ones.
X-ray study of lattice strain in boron implanted laser annealed silicon
Authors: Larson B. C. , Barhorst J. F.
Published: February 2003

The strain distribution in boron implanted, laser annealed silicon has been investigated using x-ray Bragg reflection profiles. The 400 Bragg reflection profile from implanted, laser annealed silicon was analyzed, using the dynamical theory of scattering for distorted crystals, to obtain the strain distribution in the implanted layer as a function of depth. The depth distribution of the strain for an implantation dose of 1×1016 35 keV B+/cm2, followed by a 1.6 J/cm2 ruby laser pulse, was found to have a magnitude of −5.8×10−3 near the surface and was found to decrease rapidly for depths greater than 0.2 μm. The shape of the depth distribution of the strain was found to be essentially the same as that for the boron distribution after laser annealing.
LPE growth of Mn, Ni- and Al-substituted copper ferrite films
Authors: van der Straten P. J. M. , Metselaar R.
Published: February 2003

Single-crystalline Mn-, Ni-, and Al-substituted copper ferrite films are grown by the LPE method from a PbO-B2O3 flux on (111)-MgO substrates. Solid solutions between copper ferrite and Mn3O4, NiFe2O4, and CuAl2O4 are obtained. The segregation coefficients for Ni and Al are shown to be linearly dependent on the growth temperature. From domain-structure observations and from torque measurements it is concluded that a positive uniaxial anisotropy is present in the copper ferrite films. After stress relief at the deposition temperature a stress develops during cooling to room temperature due to a difference in thermal expansion coefficients of film and substrate. This stress is responsible for the observed anisotropy.
Electrical conductivity of metallic selenium, tellurium, and silicon under high pressure
Authors: Dunn K. J. , Bundy F. P.
Published: February 2003

The pressure induced metallic state of Se, Te, and Si has been studied using a cryogenic clamp press. The resistance versus temperature curves were analyzed and used for derivation of the characteristic temperature ϑ. Good agreement was obtained between the experimental results and the Grüneisen-Bloch relation for the resistance of metals.
Thermal blooming in liquid N2 during high repetition rate stimulated Raman scattering
Authors: Wild E. , Maier Max
Published: February 2003

Stimulated Raman scattering in liquid nitrogen was studied with a high repetition rate Nd : YAG laser. Severe distortions of the laser and Raman light beams were observed. These thermal-blooming effects are the result of heating of the laser path by vibrational energy relaxation which changes the refractive index of the medium.
Characterization of ZnO piezoelectric films prepared by rf planar-magnetron sputtering
Authors: Yamamoto Takashi , Shiosaki Tadashi , Kawabata Akira
Published: February 2003

ZnO films with an excellent crystal orientation and surface flatness have been prepared by high-deposition-rate rf planar-magnetron sputtering. A detailed study of these films has been carried out using x-ray diffraction, scanning electron microscopy, reflection electron diffraction, optical measurement, and electromechanical measurement. These films have the c-axis perpendicular to the substrate. The value of the standard deviation angle σ of the c-axis orientation distribution is smaller than 0.5°, and the minimum value of σ is 0.35°, where the sputtering conditions are that the gas pressure is 5×10−3–3×10−2 Torr of premixed Ar (50%)+O2(50%) and the substrate temperature is 300–350 °C. ZnO films with a thickness up to 48 μm have been reproducibly prepared without the decreases of film quality and surface flatness. The surface flatness of these films is similar to that of a glass substrate. An optical waveguide loss for the TE0 mode of the He-Ne 6328-Å line is as low as 2.0 dB/cm in a 4.2-μm-thick film, without postsputtering treatment. The effective surface wave coupling factors are greater than 95% of the theoretical values of the ZnO/glass structure, both in the case of the interdigital transducer (IDT)/ZnO/glass and ZnO/IDT/glass structure.
XeI* production via laser absorption processes at 193 nm: Quenching kinetics
Authors: Hemmati H. , Collins G. J.
Published: February 2003

Strong fluorescence is observed on the XeI (B→X) excimer band upon excitation of a mixture containing an iodine compound and Xe with 193 nm photons. This emission is observed when I2, CH2I2, CH3I, or CF3I are used as iodine donors. Radiative lifetime and two-body collisional quenching rate of XeI(B) by Xe, I2, and CH3I have been measured. The relevance of these results with regards to use of this excimer as a source of UV stimulated emission is discussed.
Space-charge controlled conduction in thick metal-insulator-metal barriers
Authors: Henisch H. K. , Manifacier J.-C. , Callarotti R. C. , Schmidt P. E.
Published: February 2003

Numerical solutions of the (field and diffusion) transport equations yield energy and concentration contours for thick M1-I-M2 (metal-insulator-metal) barriers, and their appropriate current-voltage relationships, with and without traps. Traps must ordinarily be expected in such films, and it is shown that they result in a curvature of the barrier profile, which exercises a controlling influence over I-V characteristics in the forward direction.
Electrical properties of polycrystalline GaAs films
Authors: Yang J. J. J. , Dapkus P. D. , Dupuis R. D. , Yingling R. D.
Published: February 2003

Electrical properties of Se- and Zn-doped polycrystalline GaAs deposited by metalorganic chemical vapor deposition on substrates of polycrystalline alumina and glass were investigated. Hall-effect and resistivity measurements were made over a wide range of temperature (77–420 K). The electrical activation energies were found by measuring the variation of resistivity and carrier mobility of the polycrystalline GaAs films with sample temperature. The resistivity and mobility were found to be temperature activated over a wide temperature range as exp(Eb /kT) and exp(−Eb /kT), respectively, with the same activation energy applying to both properties. The results have been interpreted in terms of a modified grain boundary trapping model.
Loop inductance of a Josephson junction interferometer
Authors: Chang W. H.
Published: February 2003

In a Josephson junction interferometer, the current flow between the junctions is not uniform along the stripe line. The current is crowded around the junctions and becomes uniform along the strip line only when it is far away from the junction area. The inductance of such a structure with nonuniform current flow is analyzed. Several analytical formulas are derived to calculate the loop inductance of a Josephson junction interferometer.
The effect of demagnetization on the eddy-current loss in a single-layered multifilamentary superconducting coil
Authors: Sumiyoshi F. , Irie F. , Yoshida K.
Published: February 2003

The demagnetization effect of a single-layered superconducting coil made of a cylindrical multifilamentary wire on its eddy-current loss is studied for the case of ac magnetic fields parallel to the coil axis. An expression for an effective demagnetization coefficient of the wire is obtained by taking account of the interaction among turns of the coil. It is shown from this expression that the magnitude of the eddy-current loss increases remarkably with the distance between neighboring turns of the coil. The experimental loss values of the wires wound into various kinds of coils are within 20% of the theoretical values.
Domain-wall oscillation of bubble and stripe lattices in hexagonal ferrites
Authors: Dötsch H. , Tolksdorf W. , Welz F.
Published: February 2003

The wall resonance frequencies of bubble and stripe lattices in the hexagonal ferrites BaFe12O19 and PbFe12O19 have been measured as a function of crystal thickness and magnetic fields applied parallel and perpendicular to the c axis, which is oriented normal to the crystal surface. The dependence of the resonance frequencies on the normal field is in agreement with theory. For the dependence on the in-plane field, however, a similar deviation between theory and experiment occurs, as is observed in garnet bubble materials; furthermore, the resonance frequencies increase stronger with decreasing thickness of the crystals than is predicted by theory.
Conduction and threshold switching in small area lateral metal-polymer-metal devices
Authors: Sa Neto A. , Octavio M. , Callarotti R. C. , Schmidt P. E. , Esqueda P.
Published: February 2003

We report on measurements of conduction and threshold switching in organic polymer films using a new lateral geometry with very small (∼4 μm2) metallic contact areas. This geometry is shown to be quite useful in the study of both the conduction and switching mechanisms in thick (1–2 μm) polymethylmethacrylate (PMMA) films and should be equally useful in the study of switching mechanisms in other organic, semiconducting, or insulating materials. Results are presented showing reproducible and consistent ’’zero-voltage’’ resistance values. Evidence is presented which suggests that filament formation occurred during threshold switching in our polymethylmethacrylate films.
Saturation of absorption in p-Ge using picosecond CO2 laser pulses
Authors: Kwok H. S.
Published: February 2003

A time-resolved measurement on the recovery of saturation in p-Ge was performed with picosecond CO2 laser pulses. It was directly confirmed that the relaxation of hole excitation in p-Ge was faster than 40 psec and that this type of measurement can provide additional temporal information on picosecond pulses.
The preparation and properties of CeB6, SmB6, and GdB6
Authors: Tanaka T. , Nishitani R. , Oshima C. , Bannai E. , Kawai S.
Published: February 2003

Single crystals of CeB6, SmB6, and GdB6 have been prepared by a floating-zone technique under a pressurized gas atmosphere of Ar. A zone leveling technique has successfully been applied to prepare single crystals of GdB6, a compound which peritectically decomposes. The crystals so obtained were almost stoichiometric and had a low-impurity level. The measured work functions of (001) surfaces of CeB6 and GdB6 are 2.6±0.1 and 3.8±0.1 eV, respectively. The temperature dependence of the electrical resistivity of CeB6 resembles that of CeAl3. The temperature dependence of the resistivity of SmB6 single crystals is like that of a semiconductor and is similar to those reported for polycrystalline specimens. The resistivity has a very high saturation value of 70.7 Ω cm at low temperatures. A new phase transition of GdB6 was observed at about 7 K, which is indicated by hysteretic behavior in the resistivitiy versus temperature curve.
The effect of ambient atmosphere in the annealing of indium tin oxide films
Authors: Steckl A. J. , Mohammed G.
Published: February 2003

Isochronal annealing experiments on dc-sputtered indium tin oxide (ITO) films in inert (N2), reducing (N2/H2) and oxidizing atmospheres were cumulatively performed over the 50→500→50 °C range. Three anneal regimes have been identified. In region I, TA=50→200 °C, crystallization occurs, resulting in a sharp drop in sheet resistance (Rs) due to increasing mobility. TA?200 °C results in a minimum Rs. In region II, 200→500→200 °C, Rs is proportional to TA, increasing (decreasing) during the forward (reverse) anneal cycle. This behavior is apparently due to a temperature-dependent active oxygen concentration and its effect on the carrier concentration. In region III, 200→50 °C, Rs is constant with TA. Optical transmission and x-ray diffraction experiments were performed at 100 °C intervals. Successive anneals tended to increase the transmission in the visible and near-UV regions and to decrease it in the near- and far-IR region. Strong evidence of the Burstein-Moss shift was observed and an extrapolated intrinsic band gap of 3.85 eV was determined. Free-carrier absorption over the 2–5-μm regions was evident after the 200 °C anneal for all ambients. From the x-ray data, no evidence of crystallinity was observed in the as-deposited case and for anneals up to 100 °C. For anneals in the 300–500 °C range, a grain size of the order of 600 Å with an orientation normal to the (222) plane was observed for all ambients.
Memory switching in glass-metal particulate systems
Authors: Das G. C. , Chakravorty D.
Published: February 2003

A particle stretching model under the influence of an electric field has been developed in the case of a composite consisting of metallic granules of diameters ranging from 100 to 2000 Å dispersed in an oxide glass matrix. A one-dimensional heat equation has been solved in this system to delineate the temperature profile within the specimen. The critical field for switching has been computed and found to be of the same order of magnitude as that observed experimentally.
Radiation characteristics of a circular microstrip antenna
Authors: Chew W. C. , Kong J. A. , Shen L. C.
Published: February 2003

Radiation patterns of a circular microstrip antenna have been calculated with Green’s functions for a two-layer medium and compared with previous results which are valid for thin slabs and small dielectric constants. A mode expansion technique is then used to find fields and resonant frequencies. The theoretical results for the input impedances are found and are in good agreement with experimental data.
Excited-state densities in a multicathode-spot Al vacuum arc. I. Spectroscopic measurements
Authors: Boxman Raymond L. , Goldsmith S.
Published: February 2003

Excited-state densities in the interelectrode plasma produced by a 1.2-kA-peak-current 0.65-ms HAFW discharge between Al butt electrodes, 12 mm in diameter spaced 4.4 mm apart and located in a vacuum ambient, were determined by measurement of the absolute line intensities. Densities divided by degeneracies at midplane near peak current for the Al I 3s2 4s2S, Al II 3p2 1D, and Al III 4p 2p states were 8×1014, 2×1016, and 3×1016 m−3, respectively. Densities in Al II and Al III states studied could be described by distribution temperatures of 1.1 and 1.2 eV, respectively. As a function of distance from the cathode, Al I and Al II densities declined from their maximum near the cathode, with the Al I density rising slightly near the anode, while Al III states generally rose from minimum values near the cathode, reaching maximums after midplane. As a function of time, Al III densities reached a maximum near current maximum, and then decayed rapidly, while Al II densities reached their maximum about 0.2 ms after peak current, and Al I reached its maximum only near the tail end of the current pulse.
Excited-state densities in a multicathode-spot Al vacuum arc. II. Theoretical approach
Authors: Goldsmith S. , Boxman Raymond L.
Published: February 2003

A model is formulated to calculate excited-state densities in a multicathode-spot (MCS) vacuum arc. The model is composed of two components: (1) a semiempirical model for the emission of ions from the cathode surface and subsequent plasma flow and (2) a theoretical model for inelastic collisions, including excitation and ionization, and radiation in the interelectrode plasma. After consideration of characteristic times prevalent in MCS arcs, the model is reduced to a set of P-1 simultaneous linear equations and one differential equation for each ionic species considered, where P is the number of states considered for that species, where the independent variable is time in the frame of the flowing plasma, or equivalently distance from the cathode, and where the dependent variables are the populations of the various states. The model was used to determine the electron temperature in a MCS Al arc by leaving the electron temperature as a free parameter and choosing the value giving the best agreement with experimentally determined excited-state populations. For a 107-A m−2 arc an electron temperature of 6 eV was determined. It was further concluded that inelastic collisions dominate elastic collisions as an electron energy loss mechanism in this plasma.
Relative cathode spot and cell areas and currents in a copper cathode vacuum arc
Authors: Smith Glen P. , Dollinger R. , Malone Dennis P. , Gilmour A. S.
Published: February 2003

High-speed photographs of a decreasing-current vacuum arc are used to examine the luminous zone area of cathode spots. The luminous zone was observed because it provides an upper limit to the area of the spot and because it provides for relative comparisons to other published data. The photographs are used to obtain experimental values for relative total emitting area, spot area, and spot current as a function of time for decreasing current. These data were taken both for periods when a spot extinguished and when it did not. The data were obtained from a series of high-speed photographs with exposure times as short as 2.5 μs. The electrode orientation was such that a direct line of sight was used.
The shrinkage and growth of oxidation stacking faults in silicon and the influence of bulk oxygen
Authors: Hu S. M.
Published: February 2003

Preexisting oxidation stacking faults in silicon are expected to shrink when annealed in inert ambients. We have found that they sometimes exhibited a strange behavior of first shrinking and then expanding, though eventually shrinking again until disappearance. This phenomenon was not observed in silicon substrates with bare surfaces, or in oxygen-free substrates. It was traced to the combined effect of oxygen precipitation and the action of certain surface coverings, silicon nitride films in particular. In a model to explain this phenomenon, the precipitation of bulk oxygen would generate excess silicon self-interstitials which, when allowed to build up to some supersaturation, would feed the growth of the stacking faults. A bare surface would readily assimilate the excess self-interstitials by means of surface regrowth, thus suppressing a supersaturation. Information concerning the supersaturation of self-interstitials and the kinetics of surface regrowth, previously unavailable, has been obtained from this work.
Neutron transmutation doping of silicon. II. Resistivity inhomogeneity as a function of compensation ratio
Authors: Meese J. M. , Glairon Paul J.
Published: February 2003

The resistivity inhomogeneity in neutron transmutation doped (NTD) silicon is a function of both the initial inhomogeneity before transmutation doping and the final compensation ratio after transmutation doping which, in turn, is a function of the irradiation thermal-neutron fluence. Calculations of this inhomogeneity Δρ/? as a function of compensation ratio are presented. These calculations are then compared to experimental data obtained by probe measurements of NTD silicon compensated to resistivities as high as 100 000 Ω cm. Calculations are also presented which yield the maximum possible mean resistivity which can be obtained, given an initial Δρ/?, before fluctuation-induced mixed typing occurs.
A comparison of initial damage rates due to electron and neutron irradiations measured by internal friction techniques. I. Flux and temperature dependencies; scaling law
Authors: Goldstone J. A. , Parkin D. M. , Simpson H. M.
Published: February 2003

The initial pinning rate of dislocations, as computed from changes in Young’s modulus, was measured in high-purity polycrystalline copper during electron and neutron irradiations. For the same sample, flux and temperature dependencies of the pinning rate were studied for irradiations by 14.1-MeV neutrons and 1.0- and 0.5-MeV electrons. For a temperature of 330 K, the initial pinning rate depended on the flux to the 0.89±0.2 power in contradiction of simple kinetics. Additionally, to duplicate a given pinning rate due to a 14.1-MeV neutron flux between 1011 and 1012 m−2 s−1, a 0.5-MeV electron flux of 21.7±0.7 or a 1-MeV electron flux of 2.2±0.1 times the neutron flux was necessary. Temperature dependence studies from 310 to 390 K showed the same dependence for neutron and electron irradiations. The difference in migration energies in the lattice and along the dislocations was found to be 0.18±0.02 eV over this temperature range. The copper sample exhibited the Simpson-Sosin peaking of the decrement during all irradiations. The above observations lead us to conclude that the same defect, the interstitial, is responsible for pinning during both electron and neutron irradiation.
A comparison of initial damage rates due to electron and neutron irradiations measured by internal friction techniques. II. Neutron energy dependence
Authors: Goldstone J. A. , Parkin D. M. , Simpson H. M.
Published: February 2003

Neutron energy dependence of the initial dislocation pinning rate was studied from 1.9 to 23.4 MeV on a copper sample. By comparing initial pinning rates from 0.5- and 1.0-MeV electron irradiations and the neutron irradiations, and using the defect production rate for electron bombardments, an estimate of the free interstitial production cross sections (FIPCS) for neutrons was made. These FIPCS values are compared with several theories which predict the total number of Frenkel pairs produced as a function of recoil energy. Comparison with the simplest of these models (Norgett-Robinson-Torrens) showed good agreement with the trend of the energy dependence of the FIPCS. Additional comparison showed that only 1% or less of the predicted number of interstitials survive as free interstitials. A gold sample was also studied and results of 2-MeV electron and 14.3-MeV neutron irradiations are also presented.
Characteristics of the wavy interface and the mechanism of its formation in high-velocity impact welding
Authors: Botros K. K. , Groves T. K.
Published: February 2003

The known similarity between the wavy weld interface observed in high-velocity impact welding of metals and the wakes behind an obstacle in a uniform stream was analyzed. The wavelength, the wave size, and the wave shape were established in terms of semi-empirical relationships. The energy consumed in the formation of the interface wave was found to be over 90% of the collision energy for copper to steel welds. The Mathieu function was found to provide a very good approximation to the wave shape. The analysis was based on applying Birkhoff’s model of the swinging Foppl wake behind an obstacle as an analogy to determine the shape and size of the developed waves.
Parallel silicide contacts
Authors: Ohdomari I. , Tu K. N.
Published: February 2003

Parallel silicide contacts consisting of PtSi and NiSi with fixed ratios of contact areas were prepared for current-voltage and capacitance-voltage measurements of Schottky barrier height. These measurements were analyzed with models assuming a linear combination of thermionic emission currents or junction capacitances. The measured and the computed values of barrier height have been found to agree very well. A systematic diagnosis of parallel contacts under a variety of conditions is presented in the Appendix.
Electrical properties of as-grown Hg1−xCdxTe epitaxial layers
Authors: Shin S. H. , Chu M. , Vanderwyck A. H. B. , Lanir M. , Wang C. C.
Published: February 2003

The Hall coefficient and resistivity of Hg1−xCdxTe epitaxial layers with 0.195<x<0.351, have been measured between 4 and 300 K. At 77 K the results for x=0.30 show that as-grown epitaxial layers are p type, with a carrier concentration and mobility on the order of 1.2×1016 cm−3 and 400 cm2/V s, respectively. The acceptor ionization energy determined by the Hall measurements is found to change with the energy gap of Hg1−xCdxTe . The electrical parameters and compositional uniformity (Δx=±0.001) of the epilayer for x=0.30 indicate that the material is comparable to the best reported bulk Hg1−xCdxTe single crystal.
Magneto-optical properties of tin substituted MnSb films
Authors: Vijayaraghavan M. S. , Sivaramakrishnan V.
Published: February 2003

Polycrystalline films of Sn-substituted MnSb have been prepared from bulk by Flash evaporation. The Faraday rotations and optical absorption coefficients of MnSb1−xSnx (0⩽x⩽0.3) films are measured in the visible region. Room temperature specific saturation rotation F, decreases with increasing Sn concentration at all wavelengths while the optical absorption coefficient α (uncorrected for reflection) does not show any significant change. The Magneto-optic figure of merit (2F/α) for different compositions and wavelengths are estimated for evaluating these films as beam-addressable storage elements.
Monitoring i
n s
i
t
u retorting processes of oil shale by reflected and transmitted electromagnetic waves
Authors: Hong S. H. , DuBow J. B.
Published: February 2003

A theoretical model for an in situ oil shale retort with three distinct vertical zones, all surrounded by a wall of oil shale, overburden and underburden, is considered for the study of potential electromagnetic monitoring of the progression of retorting processes using wave propagation techniques. The overall power reflection and transmission coefficients for both transverse electric and transverse magnetic waves are used for finding the position of a combustion zone in the retort, based upon the assumption of straight-line propagation of monochromatic plane waves through layered lossy dielectric media characterized by the dielectric constants and loss tangents. The behavior of each power coefficient is discussed as a function of burn front positions and signal frequencies. As a result of the relatively moderate signal power for each coefficient required for detection, and the one-to-one correspondence between each power coefficient and burn front position at typical conditions, the feasibility of using low radio-frequency waves to monitor relatively large scale in situ retorting process is established.