bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of metal-oxide tunnel-junction barriers
Authors: McBride Duncan , Rochlin Gene , Hansma Paul
Published: February 2004

A technique has been developed for determining unambiguously the effective barrier height φ and the average effective thickness S of the insulating layer in a metal-insulator-metal tunnel junction. The quantity Sφ3/2 is measured from the slope of the Fowler-Nordheim plot. The experimental data are then compared with a family of calculated current-voltage curves by using various pairs of S and φ with Sφ3/2 fixed at the measured value, in order to determine the pair which gives the best fit. The method has been tested on the best understood tunnel barrier, those grown thermally on an Al film, and is found to give good agreement with independent measurements. From a macroscopic viewpoint, the tunnel barrier seems adequately described by a trapezoidal barrier model of nearly uniform height but with thickness variations on a microscopic scale over the junction area. The use of the method is illustrated on barriers grown thermally on Cr, thin-film V, and bulk V. We present a series of graphs at varying S and φ for six different values of Sφ3/2 to facilitate the determination of approximate barrier parameters with lengthy computer calculations.
Design study of toroidal deflection yokes with eddy-current compensation
Authors: Wardly G. A.
Published: February 2004

Eddy-current-compensated toroidal deflection yokes are more convenient to precisely design and fabricate than their saddle-type equivalents. A simple and practical design criterion to obtain nominal compensation, which equalizes the (coil area)(ampere-turn) products for the inner and outer toroidal yokes, has been experimentally supported.
High-temperature thermal-diffusivity measurement by a negative-pulse technique
Authors: Lincoln R. C. , Donaldson A. B. , Heckman R. C.
Published: February 2004

A new technique is proposed for measuring thermal diffusivities of materials at high temperature. A thin-slab specimen is heated with a steady flux of energy on one or both faces. The flux to one face is then interrupted momentarily during which time radiative heat losses cause a negative temperature pulse to develop in the specimen and to propagate through it. The thermal diffusivity is determined from an analysis of the temperature excursion of the opposite face. A theoretical analysis of this heat-transfer problem for which one-dimensional heat flow and a general linearized form of surface heat loss are assumed is presented. Data analysis techniques are discussed, and the results are given for some measurements on AXM-9Q graphite to 3250 K. A 250-W CO2 continuous-wave laser was used as the heat source.
Times of emission of K x rays from U235 fission fragments of known mass
Authors: Lerche R. A. , Wehring B. W. , Wyman M. E.
Published: February 2004

In order to obtain information about the nuclear transitions that produce fission-fragment x rays, the yield of K x rays emitted in the thermal-neutron fission of U235 was measured as a function of the time after fission for times between 1 and 60 nsec, as a function of the mass of the fragment emitting the x ray, and as a function of the total kinetic energy of the fragment pair emitting the x ray. Three-parameter data were recorded event by event. Two of the parameters contained information about the energies of the fission fragments from which it was possible to calculate the mass of each fragment. The third parameter contained information from which the elapsed time between the detection of one of the fission fragments and the detection of the x ray could be calculated. The results are compared with previously reported results for Cf252 and U235. There appears to be little difference between the Cf252 and U235 x-ray yields per fragment. A sufficient understanding of the mechanisms responsible for x-ray emission would permit the independent yield distributions of nuclides produced in fission to be obtained from measured x-ray yields.
Note on shock compression of solids
Authors: Huang Y. K.
Published: February 2004

In the framework of a simple compression wave and a weak shock wave, an isentrope of the Tait type and a Hugoniot adiabat based on the linear velocity relation are shown to verify each other consistently. Thus, the two empirical equations of state are given a semianalytical treatment on favorable terms.
Comment on ``Anomalous structure in appearance potential spectra''
Authors: Best P. E.
Published: February 2004

Structure in appearance potential spectra which does not correspond to a characteristic absorption edge has been reported by Ramachandran and Cox. It is suggested that at least part of this structure is due to an energy-dependent electron reflection coefficient which modulates the current entering the sample, and ways in which this hypothesis could be tested are suggested. Experimentally observed changes in the reflection of electrons incident on an evaporated aluminum film are reported.
Internal friction in aluminum subjected to fatigue and neutron irradiation
Authors: Strible Fred C. , Cady James R.
Published: February 2004

The room-temperature internal friction of pure (99.989%) annealed polycrystalline aluminum has been studied as a function of fatigue and neutron irradiation. Fatigue was found to reduce the internal friction of unirradiated aluminum by more than 50% within the first 1% of the fatigue life. This effect is attributed to rapid strain hardening in the pure aluminum. Neutron irradiation causes a large reduction in internal friction, presumably because of dislocation pinning by irradiation-generated vacancies. It appears that these are multiple vacancies or vacancy clusters that are relatively stable at room temperature. Fatigue causes the internal friction of irradiated aluminum to converge to the same value as unirradiated aluminum near the fatigue limit. This result indicates that irradiation-generated vacancies may be readily absorbed by moving dislocations and explains the observation that the fatigue strength of aluminum is relatively unchanged by irradiation.
Reply to ``Comment on `Interpretation of Pt3Co FIM images as investigated with an atom probe' ''
Authors: Tsong T. T. , Müller E. W.
Published: February 2004

Southworth's critical comments on our interpretation of Pt3Co field ion images is rebutted by pointing out the fact that the top PtCo layers used in our atom probe experiment were completely resolved.
Effect of neodymium on dislocation velocity in CaF2
Authors: Katz R. Nathan , Coble R. L.
Published: February 2004

The effects of neodymium-dopant additions on the behavior of dislocations in calcium fluoride were studied. Velocity measurements were carried out on edge and screw dislocations as a function of stress, temperature, and dopant content. It was observed that screw dislocations can be the more mobile type in CaF2, depending on the stress and concentration of aliovalent impurities present. The mobility of screw dislocations relative to edges was reduced significantly by 70 ppm Nd3+. An apparent transition in the drag mechanism from extrinsic to intrinsic was observed for edge dislocations.
Change of electrical resistivity of metal films bombarded with helium ions of low energy
Authors: Nomura A. , Kanayama M. , Kiyono S.
Published: February 2004

Copper and gold evaporated films of thicknesses between 500 and 2500 Å have been bombarded at liquid-nitrogen temperature with 4–10-keV He ion beams. The electrical resistivities of these films increase with dose without saturation, and the values of these changes in the thinner films approach tens of μΩ cm at a dose of 1017 ions/cm2. About 80% of the resistivity changes induced in copper and about 60% of the resistivity changes induced in gold are recovered after annealing to 453 K. The remarkable peaks of the thermal recoveries are mainly observed in stage II. The nature of the evaporated metal films closely relates to the large resistivity changes, which are also affected by bombarding with low-energy ions.
Critical misfit for generation of dislocations at second-phase particles
Authors: Jagannadham K. , Ramachandran E.G.
Published: February 2004

The generation of dislocation loops around spherical second-phase particles by various models is examined. A theoretical lower limit to the critical misfit is obtained and it is found to agree with the experimentally observed values.
Ultrasonic measurements of Young's modulus and extensional wave attenuation in refractory metal wires at elevated temperatures with application to ultrasonic thermometry
Authors: Papadakis E. P. , Fowler K. A. , Lynnworth L. C. , Robertson A. , Zysk E. D.
Published: February 2004

Ultrasonic velocity and attenuation measurements have been made by traveling-wave methods on several refractory metals and their alloys. Broad-band pulses centered around 120 kHz were used for extensional waves (and some torsional waves) in wire specimens. Elastic moduli calculated from the velocities decrease with increasing temperature; the slope increases in magnitude at about half the absolute melting point. At the same point, the attenuation begins to increase rapidly and peaks 300–600°C above the breakpoint. These effects are ascribed to absorption in grain boundaries. The transit time versus temperature in rhenium wire has been calibrated for the use of rhenium as an ultrasonic thermometer sensor. Ultrasonic thermometry above 2000°C is an application of the present measurements.
Electrical contact activation: A phenomenoloigcal model
Authors: Schubert Rudolf
Published: February 2004

A phenomenological model of contact activation is presented based on diffusion of trace gaseous pollutants. The chemistry of these gases when adsorbed on the contact surface is discussed. Contact operating rates, gaseous pollutant concentrations, and contact surface roughness are considered. Experiments are performed and discussed which involve the decomposition of inorganic halogenated compounds and hydrocarbon compounds, the chemical effects of these compounds when on palladium contacts with protection circuits, and the rate of operation of contacts. Experimentally, an attempt is made to simulate conditions as they are found in the field whenever possible. The results of these experiments show that both classes of compounds can activate and thereby cause contact erosion when they are present at the ppm level. It is further shown that a 1-Hz versus 10-Hz relay operating rate can increase average arc time by typically a factor of 10 when 1 ppm of selected gaseous impurities are present in the atmosphere around the contact. These results fit the model as presented, agree with data collected from the field, and are capable of explaining erosion rate differences between the field and various life tests.
Comment on approximations involving the transport equation for ions in drift tubes
Authors: Vorburger T. V. , Woo S. B. , Whealton J. H.
Published: February 2004

Two assumptions made in a previous treatment of this subject are circumvented—that the mean free time is constant and that the ion temperature is independent of position. The results are applied to drift tube analysis for errors in the interpretation of the drift velocity due to N−2 effects.
Beam-plasma waves from a finite-length plasma
Authors: Roberson C. W. , Fukai J.
Published: February 2004

By inserting a grid in a beam-generated plasma column, single waves can be produced as a result of the beam-plasma instability exciting a finite-length cavity mode. The oscillation frequency is found to increase with beam velocity, in contrast to the frequency-velocity relationship of the wave with the maximum growth rate. The nonlinear evolution of the beam-generated wave and satellites due to a test wave are observed.
Theory of potential-well formation in an electrostatic confinement device
Authors: Black W. M. , Klevans E. H.
Published: February 2004

A theoretical model is developed to describe the behavior of an ion-injection electrostatic confinement device. It is assumed that there is a shallow potential well in the center. Distribution functions, which are consistent with atomic processes occurring and with mechanisms leading to particle angular momentum, are obtained for ions and electrons. Using these distribution functions, Poisson's equation is solved to obtain potential and density profiles. By varying the experimental parameters, the conditions needed to go from a shallow potential well to a deep potential well are studied. The most important problems are found to be nonspherical focusing through grid construction asymmetry, and neutralization by electrons. Deeper wells are produced by increasing ion perveance, improving spherical symmetry, and reducing pressure.
Hypervelocity impact heating of porous aluminum
Authors: Rehfuss Donald E.
Published: February 2004

Based on experimental shock data of Al'tschuler, Anderson, and Kormer, an equation of state from Zel'dovich is used to estimate thermodynamic characteristics of a porous aluminum target, after impact by iron or aluminum projectiles, in the impact velocity range ∼8–20 km s−1, which produces shock pressures in the range 0.4–8Mbar. The initial target distention, m=ρ0/ρ00, is varied from 1 to 3. It is found that projectile and target pressures and the projectile thermal energy are monotonically decreasing functions of m. The thermal energy E′ retained in the relaxed target is a monotonically increasing function of m. The electronic fraction of thermal pressure ranges from a few percent for a nonporous target at 8 km s−1 up to 20% at 20 km s−1 and m=3. Within the ranges of target density, ρ0i, and target distention, m, considered in this study, and in the impact velocity range Vi=8–16 km s−1, the relative effectiveness of these parameters in producing target heat E′ (erg/g) can be roughly characterized by the relation E′∝ lim ∼ρ0i0.47 m1.49 Vi2.13. The minimum velocity that will produce significant target vaporization in aluminum-aluminum impact decreases from 18.4 to 7.9 km s−1 as m is changed from 1 to 3, whereas that for iron-aluminum impact drops from 14.0 to 7.4 km s−1.
Gas migration in vitreous B2O3
Authors: Shelby J. E. , Wayne R. C.
Published: February 2004

Permeation, diffusion, and solubility of three gases (helium, deuterium, and neon) were measured in vitreous boric oxide. Results indicate that these parameters are especially sensitive to the thermal history of the glass. If experimental times are comparable to structural relaxation times, anomalous results may be obtained.
The rise of small bubbles in water
Authors: Bachhuber Carl , Sanford Cecil
Published: February 2004

Contrary to the conclusions of previous researchers who found the drag coefficients of small bubbles in water to coincide with those expected for solid spheres, we found the drag coefficients of small bubbles in water (Reynolds numbers from 2 to 40) to be significantly less than those expected for solid spheres and close to what we expect are the drag coefficients for ideal fluid spheres. The difference between the present results and those of previous workers is ascribed to velocity measurements nearer to the point of formation, thus giving the surface of a bubble less time to age and collect surfactants.
Zero-bias anomaly in GaAs/Mo tunnel junctions
Authors: Sood B. R. , Pak Y. L.
Published: February 2004

A large zero-bias anomaly has been observed in the point contact tunnel junctions made between a degenerate p-type GaAs and Mo. The anomaly corresponds to a resistance peak centered at zero bias. The junction resistance at zero bias is a strong function of temperature, increasing with decreasing temperature. A quantitative study of the voltage and temperature dependence of the zero-bias anomaly has been made. No effect of the magnetic field up to 12 kG was found. When the temperature was lowered below the transition temperature of Mo, the superconducting energy gap of Mo was observed, which indicated that the mechanism of current flow is by electron tunneling.
Discussion of the surface-potential fluctuations caused by oxide-charge fluctuations
Authors: Declerck G. , Van Overstraeten R. , Broux G.
Published: February 2004

Experimental values of the standard deviation σs of fluctuations of surface potential are discussed. A comparison is made between the experiments and the theory of Nicollian and Goetzberger recently generalized by the mathematical model of Brews. We conclude that Brews's model adequately represents most of the data, provided both positive and negative fixed charges are assumed to be present simultaneously in our devices.
Monolithic solid-state traveling-wave amplifier
Authors: Gover Avraham , Yariv Amnon
Published: February 2004

A new monolithic structure for solid-state traveling-wave amplifiers is proposed, which promises efficient interaction between a drifting charge carrier stream and a slow electromagnetic wave component. The suggested configuration is potentially suitable for operation in the far-ir frequency regime. A one-dimensional analysis of the interaction between the electromagnetic waveguide mode and the carrier current is presented, including the loss contribution due to the nonsynchronous space harmonics of the electromagnetic mode.
Electron-beam spreading and its effect on sustainer current and field distribution in CO2 lasers
Authors: Jacob J. H. , Reilly J. P. , Pugh E. R.
Published: February 2004

An electron-beam-initiated high-pressure CO2 laser discharge is investigated. It is assumed that initially the discharge current flows along the vacuum electric field direction. The resulting distortion of the electric field is calculated by a linearization of the continuity equation. We have computed the solution for the special case of a finite electron beam and infinite planar electrodes. The predicted variation of the sustainer current and distortions of the applied voltage are compared with experimental results.
Observation of compressed picosecond pulses of high repetition rate from a Nd-glass laser
Authors: Drexhage K. H. , Eisenthal K. B.
Published: February 2004

Picosecond pulses generated by a mode-locked neodymium-glass laser have been compressed down to 0.5 psec with a repetition rate up to 3 × 1011 Hz by the insertion of a glass flat inside the laser cavity. The reduction in pulse width is attributed to a frequency-dependent transit time on transmission through the glass flat.
Elastoresistance of n-type silicon on sapphire
Authors: Hynecek Jaroslav
Published: February 2004

Elastoresistance of n -type silicon on sapphire is measured. The measurement is performed with a gated MOS Hall bridge. An extrapolation method is developed to minimize errors due to aluminum autodoping. From the obtained result, it is concluded that the lateral stress present in the silicon causes almost complete depopulation of the energy surface in the kz direction, perpendicular to the surface of the silicon. This in turn causes pronounced changes in the transport properties, such as resistivity or Hall mobility. Qualitative agreement with the theory, in which no scattering mechanism is considered, is obtained.
On the efficiency of coupling light from stripe-geometry GaAs lasers into multimode optical fibers
Authors: Brackett C. A.
Published: February 2004

The coupling between GaAs injection lasers and multimode optical fibers using spherical ends on the optical fibers is examined. In particular, the results previously published by Kato are shown to be overly optimistic, although considerable improvement over using a flat-ended fiber is still predicted. Neglecting reflection losses, we predict maximum coupling efficiencies of the order of 60–70% for our typical double-heterostructure laser diodes and have experimentally measured 62% in a case for which 60% is expected from the theory.
Double injection in insulators: Theoretical description and analysis of some double-injection experiments in anthracene crystals
Authors: Schwob H. P. , Williams D. F.
Published: February 2004

The fundamental relationships concerning double injection into an insulator have been developed using the free-carrier densities n and p as variables. Particular attention has been paid concerning the limitations imposed by the assumptions used in obtaining the solutions for the final integrals representing the voltage, crystal current, and crystal thickness. Many different forms of the n(p) relationships have been discussed, particularly those which may be experimentally obtainable. Finally, these theoretical results have been applied to an actual experimental result reported for injection into anthracene, and the theory satisfactorily reproduces the observed current-voltage dependence. The additional information obtainable from this analysis is discussed.
Optical properties of gold acceptor and donor levels in silicon
Authors: Braun S. , Grimmeiss H. G.
Published: February 2004

The absolute values of all four photoionization cross sections for electron and hole emission from the gold acceptor and donor levels in silicon have been evaluated by measuring junction photocurrents. By using two light sources it has been shown that steady-state photocurrents provide a unique determination of threshold energies for transitions between the energy bands and the impurity levels, independent of the type of junction. Not too far away from the threshold energies, the experimental results are in good agreement with the δ-function impurity potential model of Lucovsky. Threshold energies of 0.555 and 0.61 eV are obtained for the electron and hole emission from the acceptor levels, respectively, and 0.75–0.83 and 0.345 eV for the corresponding emissions from the donor levels. For the acceptor levels, the sum of the threshold energies (1.165 eV) is very close to the band gap (1.166 eV), which indicates that relaxation effects are small. In addition, the influence of the valence-band structure on the energy dependence of the photoionization cross section for the hole emission has been investigated.
Electronic collision: Induced transition between the upper levels of a He–Cd laser
Authors: Sakurai Takeki
Published: February 2004

Interruption of the laser field in a 4416-Å He–Cd laser modulates the spontaneous emissions originating not only from the laser levels but also from other excited levels. From the measurement of the intensity ratio of these spontaneous emissions, the rate coefficient of the transition between 4d9 5s2 configurations in Cd II induced by electronic collision and its cross section are obtained. The total deexcitation rate of the level by electronic collision is also measured.
Dynamic properties of high-mobility garnet films in the presence of in-plane magnetic fields
Authors: Shaw Roger W. , Moody J. W. , Sandfort R. M.
Published: February 2004

The dynamics of domain wall motion in GdyY3−yGax Fe5−xO12 garnet films has been studied using optical response to a fast-rise pulse in bias field. Damped oscillations of the domain walls have been observed and analyzed to yield domain wall mass per unit area, mobility, and limiting velocities. Masses have been found which are in excess of the accepted theoretical values for thick samples by factors between 1.5 and 3.6. Limiting velocities have been determined in general agreement with values predicted by Slonczewski for motion involving generation and propagation of horizontal Bloch lines. The application of a magnetic field in the plane of the film and in the plane of the domain walls under observation caused a decrease in domain wall mass density and increases in mobility and limiting velocity. The mass decrease is substantially greater than that predicted by theory.
Josephson frequency conversion in the range 145–1600 GHz with Nb–Nb superconducting point contacts used as oscillator-mixer
Authors: Vernet G. , Adde R.
Published: February 2004

The Josephson frequency conversion in the millimeter and submillimeter wave region is studied with superconducting Nb–Nb point-contact junctions at 4.2 °K, using the contact both as the local oscillator and the mixer with intermediate frequencies of 0.1, 0.3, and 9.2 GHz. The point contact is in a nonresonant structure and fed by a constant current source: neither a strong rf coupling of the contact with a cavity nor a stabilizing shunt resistance was proved necessary. The direct observation of frequency conversion was performed with a microwave receiver at 9.2 GHz in a range of Josephson frequencies between 145 and 1600 GHz. The experiments with intermediate frequencies fi of 0.1 and 0.3 GHz indicate that conventional frequency conversion does not occur but that the observed signals are related to noise effects. An analysis of the frequency conversion mechanism in a Josephson junction operated as an oscillator-mixer is proposed which includes the noise effects and also the feedback effects induced in a junction driven by a constant current source. The results show that low-frequency current components are induced in the junction, which can give large spurious signals when small i.f. are used.
Wave conversion in stratified media with hyperbolic-tangent nonuniformities
Authors: Doane J. L.
Published: February 2004

A systematic procedure is developed for finding analytical solutions of certain ordinary linear differential equations of arbitrary order, describing reflection and conversion of waves in multiwave media having a concentrated region of nonuniformity. This procedure involves transformation to equations solvable by generalized hypergeometric functions which have the form of normal modes, exp(−ikz), in uniform regions. It is applicable when the variable coefficients in the original equation contain only linear combinations of one varying parameter, p(z), and in certain cases its derivatives or ratios thereof, if p(z) is proportional to tanhz. Arbitrary gradients and dissipation are allowed. The applicability of this procedure to solve for the reflection and conversion coefficients is indicated for second-, fourth-, and sixth-order problems in magnetostatic, spin, and elastic-wave conversion in magnetic insulators such as yttrium iron garnet, and for electromagnetic-to-electrostatic wave conversion in hot plasmas. Some of these problems involve fourth-order singular turning points formed by the coalescence of resonance and cutoff. Explicit expressions for the reflection and conversion coefficients are given for fourth-order systems in terms of Γ functions of complex arguments. In the absence of dissipation, the absolute magnitude of these coefficients may be expressed in terms of ordinary transcendental functions.
Magnesium fluoride metal atom oxidation laser from explosively generated metal vapor
Authors: De Koker Jon G. , Rice Walter W.
Published: February 2004

Magnesium fluoride laser emission has been produced from the chemical reaction of explosively generated magnesium jets and fluorine. The temporal and spectral characteristics of these laser pulses are similar to those reported earlier for the MgF exploding wire laser, i.e., pulse duration of 1–3 μs, and wavelength > 11μm, which suggests a purely chemical pumping mechanism for both of these metal atom oxidation lasers.
Superconductive tunneling in junctions containing lead-gold layered films
Authors: Basavaiah S. , Lahiri S. K.
Published: February 2004

Tunneling between lead-gold layered films separated by an oxide barrier has been investigated. From these results, the superconducting transition temperature and the energy gap of the compound, AuPb3, present in these films have been deduced.
Electron distribution in a gridded Penning discharge
Authors: Conte Dominick , Kent Gordon
Published: February 2004

Electron distributions in a Penning discharge, consisting of two glow discharges separated by a cylindrical microwave cavity with gridded ends, were measured using the shift of resonant microwave frequencies and Langmuir probe data. The shape and magnitude of the distributions were determined for a range of pressure, discharge current, magnetic field, and for several cathode shapes. The microwave technique gives the distribution as a two-parameter function, and the probe data gives a more detailed profile but quantitatively less reliable. All data indicated that the plasmas were electron rich. The distributions were azimuthally symmetric with a maximum at the center at higher pressures; at lower pressures and higher magnetic fields, the densities were depressed in the center, indicating the development of a circulating sheath of electrons. The data indicates that the microwave diagnostic technique is quite suitable when the distribution is a maximum at the center, and it is a useful procedure for calibrating a probe when there is no suitable probe theory for a particular range of experimental parameters.
Determination of hafnium-p-type silicon Schottky barrier height
Authors: Beguwala M. , Crowell C. R.
Published: February 2004

The Schottky barrier height for holes in hafnium (Hf)-p-type silicon junctions was determined to be 0.58±0.02 eV by current-voltage, capacitance-voltage, and photothreshold techniques. The barrier height determined here does not agree with the earlier reported value of 0.90 eV by Saxena. We have shown that interface effects can account for only minor changes—viz., 0.02 eV in our barrier height value. The reasons for the discrepancy with Saxena's value are not fully understood, but our results are consistent with those expected from conventional Schottky barrier models.
Uniqueness of time-independent electromagnetic fields
Authors: Karlsson Per W.
Published: February 2004

As a comment on a recent paper by Steele, a more general uniqueness theorem for time-independent fields is mentioned.
Grüneisen constants of some group V and VI elements
Authors: Aggarwal M. D. , Verma J. K. D.
Published: February 2004

Some comments on the evaluation of the Grüneisen parameter from a log(Debye temperature)-vs-log(atomic volume) plot are presented. The values of the Grüneisen constant of group V and group VI elements obtained from this plot are 1.57 and 0.8, respectively.
The effects of ionizing radiation on the hardening of KBrxCl1−x
Authors: Hopkins J. R. , Martin J. J. , Larkin J.
Published: February 2004

The flow stress of a series of KBr–KCl mixed crystals has been measured as a function of radiation damage. The magnitude of the increase in flow stress is approximately the same as it is for pure KCl or KBr for equivalent amounts of damage. This result shows that the radiation hardening and alloy hardening are additive. The data have also been used to indicate the size and shape of the interstitial clusters in these mixed crystals.
Dielectric losses in organic monomolecular layers
Authors: Marc G. , Messier J.
Published: February 2004

Dielectric losses of aluminum/organic monolayer/aluminum structures were studied between −170 and +50°C within the frequency range 100 Hz to 50 kHz. They are due largely to oxide layers on the electrode surfaces and partly to movements of dipoles linked to the organic molecules. At a measurement frequency of 1 kHz, absorption maxima appear at −100 and −30°C and are attributed to dipole movements in the amorphous and crystalline regions of the layers, respectively.
Microwave phonon attenuation in yttrium aluminum garnet and gadolinium gallium garnet
Authors: Dutoit M.
Published: February 2004

Measurements of the attenuation of longitudinal acoustic waves in pure and Nd-doped YAG and GGG between 0.3 and 3 GHz and from 4 to 300 K are presented. At low temperatures, these results are successfully interpreted in terms of scattering of microwave phonons by quasicollinear longitudinal thermal phonons. The total attenuation at 300 K and 1 GHz is 0.15 dB/μsec in YAG and 0.25 dB/μsec in GGG and varies as the square of frequency. The attenuation due to thermal phonons is within a factor of 2 of the value predicted for Akhiezer loss. The differences between pure and Nd-doped samples are smaller than experimental uncertainties.
Attenuation and dispersion of longitudinal acoustic waves in α-sulphur
Authors: Vacher René , Sapriel Jacques , Boissier Maurice
Published: February 2004

Velocities and attenuations of longitudinal acoustic waves propagating along the three principal directions of α-sulphur were measured by means of ultrasonic waves between 20 and 500 MHz and by Brillouin scattering between 4 and 25 GHz. Velocity and attenuation variations plotted versus frequency are continuous along the whole investigated range 20–25 000 MHz. Besides, an important velocity dispersion has been pointed out, with a relative variation of about 1.5%. A phenomenological interpretation involving a loss process with a single relaxation time is given which allows us to account for the whole set of results.
Oxide structure in evaporated aluminum films
Authors: Pettit Richard B. , Silcox J.
Published: February 2004

Transmission electron microscopy, small-angle and selected-area diffraction, and surface-plasmon dispersion studies are used to characterize the microstructure of evaporated aluminum films. The grain size of the films is obtained from the width of the Bragg reflections. Energy-loss studies show that the surface-plasmon dispersion is a function of the average grain size for films grown at low condensation rates, i.e., ``dirty'' films, while the average surface-plasmon energy for all films, ``clean'' and ``dirty'', is close to 6.7 eV, the value characteristic of an aluminum-aluminum oxide interface. In clean films the dispersion depends on thickness in the normal fashion and no dependence on grain size is detected. We conclude that in dirty films a thin layer of oxide surrounds each grain. Small-angle electron scattering and out-of-focus transmission electron microscopy identify a cluster effect in which somewhat larger oxide boundaries surround clusters of approximately 36 grains (in most films). A similar structure is shown to develop at a stage in the growth of gold films.
Coaxial dielectric waveguides. II
Authors: DeVore R.
Published: February 2004

Coaxial dielectric waveguides were investigated in order to ascertain their useful bandwidth. The operating bandwidth is defined as a region of dominant HE11 mode propagation only, where 93% or more of the electromagnetic energy is transported internally. Guide loss characteristics are highly dependent on the loss tangents of the several dielectrics. Coaxial dielectric waveguides have more linear phase characteristics than do their hollow metallic counterparts. Cutoff wave numbers for the four lowest of the high-order modes have been found for a number of combinations of dielectrics.
Anode surface radiance from microsecond vacuum arcs
Authors: Grissom J. T. , Newton J. C.
Published: February 2004

Measurements of anode surface radiance as a function of time for microsecond-duration vacuum arcs have been performed using an infrared-sensitive solid-state detector. Anode surface temperatures have been inferred from the measured radiance values using information concerning the surface spectral emittance. Particular attention has been given to the measurement of anode spot temperatures as a function of time. The anode materials investigated are Al, Cu, and Kovar. In addition, surface temperatures due to plasma heating of Al2O3 (alumina) and BeO (beryllia) ceramics surrounding the active anode area have been determined. Values of the average anode current density ranged from 6×103 to 5×104 A/cm2, with arc current pulse lengths of 1–12 μsec. Anode spot temperatures between 2600 and 3300°C for Cu, and between 2000 and 2400°C for Al were observed. The maximum surface temperatures of the ceramic insulators were between 2900 and 3500°C for Al2O3 and between 2000 and 2300°C for BeO. Calculations based on an integral equation solution to the heat-flow equation suggest that the input power density to the surface falls between 106 and 107 W/cm2 for Al, Cu, Al2O3, and BeO. Based on these values, estimates of the anode spot current density for Al and Cu fall between 105 and 106 A/cm2.
Anisotropic relaxation time in quantized (110) silicon inversion layers
Authors: Nelson A. R.
Published: February 2004

The relaxation times have been calculated for the [1̄10] and [001] directions on a silicon (110) surface inversion layer. Three different scattering processes have been considered: surface potential fluctuation, independent coulomb centers, and surface roughness. The results have been used to explain the anisotropic mobility, which has been previously observed experimentally for this surface orientation. Also, further verification of each scattering process is provided. It appears that the scattering due to charge distributions is important at weak gate voltages, while surface roughness is dominant in the strong-field limit.
Characterization of the dose from a pulsed electron beam using holographic interferometry
Authors: Mix L. P. , Perry F. C.
Published: February 2004

Energy deposition of a pulsed electron beam has been investigated using double-pulse holographic interferometry. The technique has been shown to provide depth-dose data over the illuminated area for a thermoelastic absorber. Possibilities of employing the method at higher doses are discussed.
Annealing properties of ion-implanted p-n junctions in silicon
Authors: Michel A. E. , Fang F. F. , Pan E. S.
Published: February 2004

Phosphorus-, arsenic-, and boron-implanted junctions have been investigated with special emphasis on their annealing behavior of the junction-leakage currents. It is shown that a minimum of about 900°C and 30 min annealing is required for junction qualities equal to that of diffused ones. Hall-effect measurements of the implanted region show that about 900°C for phosphorus annealing and 1000°C for arsenic and boron annealing are required to restore carrier concentrations corresponding to the implanted impurities, respectively. The relative importance of surface area and perimeter contribution to the junction leakage is identified. It is shown that for an area-to-perimeter ratio smaller than about 1 mil, the perimeter contribution dominates. There are indications that the distribution of the leakage contributing g-r centers coincide with the implanted impurities.
Optical properties of aggregated Ag and Au thin films—MG approach
Authors: Tokarsky R. W. , Marton J. P.
Published: February 2004

The effect of aggregation on the optical properties of Ag and Au metals in thin-film form is analyzed with the simple Maxwell-Garnett theory. Free-electron damping and interband transitions in the particles are considered, along with the effect of an interparticle dielectric material. Numerical analysis shows that interband transitions severely damp the free-electron conduction resonance and that they introduce bound-electron resonance structure in the dielectric functions of the aggregated medium. These results are used to interpret experimental data.
Preparation of self-supporting carbon foils of uniform thickness below 2 μg/cm2 density
Authors: Holl M. , Haas D. , Berger R. , Schürmann D. , Buttlar H. v.
Published: February 2004

Self-supporting thin carbon foils (areal density, 5 μg/cm2) produced by vacuum evaporation are thinned to less than 1 μg/cm2. The thinning is achieved by the bombardement of atomic hydrogen produced from the dissociation of H2 at the surface of a hot tungsten filament (temperature, 2450 K). The areal density of the foils is measured by means of uv light transmission. The thinned foils are mechanically stable and uniform in thickness.
Intensity filtration of laser light
Authors: Thorne James M. , Loree Thomas R. , McCall Gene H.
Published: February 2004

The nonlinear optical properties of carbon disulfide and bleachable dyes are utilized to construct a variety of intensity filters for 1.06-μm picosecond pulses. The principle object of the study was the development of a filter that discriminates against low intensities, but the devices may be easily adjusted to limit high-intensity hot spots or combined to form positive or negative notch filters. Applications to other wevelengths and/or time regimes are possible. The devices also show promise as isolators and pulse shapers.
Characterization of the interface states at a Ag/Si interface from capacitance measurements
Authors: Deneuville A.
Published: February 2004

From the variation of the quasi-Fermi levels at the interface of a Ag–Si diode under forward bias, we present a new way to characterize the interface states of such an interface from capacitance and conductance measurement. We obtained the density, the time constant, and the capture cross section of the interface states. The relative energy distribution of the interface states is in close agreement with those deduced from our photoelectric measurements. Such a determination implies that interface states are in equilibrium with silicon, in agreement with Heine's theory.
Experimental determination of optimum operating conditions of a superconducting interferometer
Authors: Pascal D. , Sauzade M.
Published: February 2004

A superconducting interferometer (SQUID) behaves as a nonlinear impedance, the value of which changes periodically when an linearly increasing flux is applied to it. Conditions of utilization of this device, when stimulated by an rf flux to obtain maximum sensitivity, where studied and were found to satisfy the relation k2Q≃1 and 2πLsic/φ0≃1. Experimental results show that the signal response increases as √f and the sensitivity obtained at 245 MHz is 4 × 10−5 φ0 Hz−1/2.
rf reactively sputtered superconducting NbNx films
Authors: Keskar K. S. , Yamashita T. , Onodera Y. , Goto Y. , Aso T.
Published: February 2004

NbNx films containing various phases have been prepared by the radio frequency (rf) reactive sputtering technique and examined for their superconducting and electrical properties. These films have been found to have a wide range of upper critical magnetic fields, transition temperatures, and normal-state resistivities depending on the partial pressure of nitrogen in the sputtering atmosphere and the substrate temperature. The fcc NbN films exhibit Hc2(4.2°K) ranging 150 to 230 kOe, whereas some of the Nb+Nb2N+NbN and Nb2N+NbN films exhibit high critical fields more than 320 kOe which are probably caused by the existence of thin connected superconducting filaments in the multiphase films at high field.
Domain patterns of a magnetic garnet bubble film in an arbitrarily oriented field
Authors: Shimada Yutaka
Published: February 2004

The domain pattern formation process of an epitaxial garnet film in an arbitrarily oriented field has been investigated. Depending on the orientation of the field, a bubble array or stripe domains aligned in various directions appeared. A sixfold symmetry in the sample plane was observed. The behavior of the stripe domains in an arbitrarily oriented field was theoretically described, and an explanation was given to the bubble formation process. Based on the experimental and theoretical results, some applications of these properties will be briefly discussed.
Correlation functions for predicting properties of heterogeneous materials. III. Effective elastic moduli of two-phase solids
Authors: Corson Peter B.
Published: February 2004

The Beran-Molyneux bounds on the effective bulk modulus and the McCoy bounds on the effective shear modulus of a statistically homogeneous and isotropic heterogeneous material require a knowledge of several three-point correlation functions. These correlation functions are contained within integrals which must be evaluated. Both sets of bounds are here evaluated for two-phase materials, using the correlation functions developed in Paper II of this series. The method of evaluation includes a simplification of the integrals containing the correlation functions and a numerical evaluation of the simplified integrals. The resultant bounds are compared with experimental data on the effective shear modulus of three two-phase systems: aluminum-lead, iron-lead, and tungsten-lead. The bounds are also compared with the less restrictive Hashin-Shtrikman bounds which do not require any knowledge of correlation functions. It is shown that both sets of bounds are a significant improvement over the Hashin-Shtrikman bounds, and that they are in agreement with existing experimental data.
Comment on ``Source of error in foil thickness calibration by x-ray transmission''
Authors: Haggmark L. G.
Published: February 2004

A recent paper by Boster showed that the x-ray transmission through a nonuniform foil is greater than that through a uniform foil that has the same area, weight, and density. Through examples, it was demonstrated that the ratio of the transmission in the two cases is independent of the foil thickness. It was claimed that the percent error in the average foil thickness as determined by x-ray transmission is related directly to this ratio and thus also independent of the foil thickness. It is shown in this note that the error in the average foil thickness depends on the natural logarithm of this ratio, and the percent error is inversely proportional to the average foil thickness.
Reply to ``Comment on `Source of error in foil thickness calibration by x-ray transmission' ''
Authors: Boster Thomas A.
Published: February 2004

The basic difference between the approaches of Haggmark and of Boster is the selection of ``thickness'' as opposed to ``transmission'' as the working variable.
Optimum values of the elastic constants of single crystals with particular reference to CaMoO4
Authors: James B. W.
Published: February 2004

A survey is given of the values of the seven independent elastic constants of CaMoO4 obtained by three different methods from the same set of measurements of the velocity of fourteen ultrasonic waves. Values of the seven elastic constants calculated from various appropriate sets of seven velocities are presented. An optimum set of elastic constants has been obtained from all the velocities. It is noted that specimens oriented accurately in particular directions are not necessary.
Note on the aluminum suboxides
Authors: Yamaguchi S.
Published: February 2004

It was demonstrated in terms of electron diffraction analysis that aluminum suboxides, i.e., Al2O and AlO were formed at the boundary between aluminum and gamma alumina (γ-Al2O3).
Photodepression in As–S thin films
Authors: Kasai M. , Nakatsui H. , Hajimoto Y.
Published: February 2004

A small depression (about 80 Å) was observed when As–S thin films were exposed to a xenon 500-W lamp. The depression is considered to be a structural change in amorphous As–S.
Decoration of NaCl with Au: Contamination effects
Authors: Frederick Paul S. , Hruska S. J.
Published: February 2004

The traditional procedure for decorating cleaved NaCl crystals is found to be substantially affected by contaminants frequently found in high-vacuum systems. Transmission electron microscope photographs of Au decorant show effects caused by vapors from mechanical vacuum-pump oils, diffusion-pump oils, and other oils. No appreciable decoration of monatomic steps was observed in those cases where decoration was carried out in a sufficiently cleaned ion-pumped system.
Comment on ``Glide systems and Peierls stresses in fcc and bcc metals from phonon energies''
Authors: Taylor G. , Vitek V.
Published: February 2004

The theory of Boffi et al. of Peierls stresses in crystals is criticized on physical grounds on a number of points.
Addendum: Transient behavior of the electrically controlled birefringence in a nematic liquid crystal
Authors: Labrunie G. , Robert J.
Published: February 2004

A modified viscosity coefficient accounts for the back-flow effect in a homeotropic nematic cell.
Grain-boundary solute electromigration in polycrystalline films
Authors: Ho P. S. , Howard J. K.
Published: February 2004

It is demonstrated that with proper analysis of the diffusion profiles, the effective charge and diffusivity for grain-boundary electromigration can be separately measured. Electromigration profiles are analyzed based on Fisher-type approximations for an equiaxial and perfectly textured grain structure. Electromigration profiles were obtained for Cu in Al at 255°C by measuring the spreading of a Cu cross-stripe subject to a direct current; the results were checked by annealing experiments performed under similar conditions. Cu was observed to migrate in the direction of electron flow. Results obtained from analysis of the anode and annealing profiles are −16.8±1.2 for the effective charge and (1.75±0.12) × 10−14 cm3/sec for the diffusivity parameter αDbδ. The over-all consistency of the results is better than 5%. Whipple analysis gives a more exact value of (2.74±0.16) × 10−14 cm3/sec for αDbδ.