bluuebunny/crossref_metadata_2025 huggingface dataset:
The diffusion and solubility of copper in iron
Authors: Salje G. , Feller-Kniepmeier M.
Published: February 2003

The chemical diffusion coefficients and the solubility limits of copper in iron were determined in the temperature range 690–1050 °C by electron probe microanalysis. Specimens were large-grained polycrystals for the γ-iron and single crystals for the α-iron. The iron contained less than 11 wppm of impurities and had a resistivity ratio R293 °K/R4.2 °K up to 8700. The results for the diffusion coefficients are (in cm2/s) DγCu=0.19 exp(−65 100/RT) and DαCu=300 exp(−67 800/RT). An anomalous decrease of the diffusion below the Curie point was observed.
X-ray Debye temperatures of barium and strontium nitrates
Authors: Kulkarni R. G. , Bichile G. K.
Published: February 2003

The x-ray Debye temperatures ϑM of barium and strontium nitrates have been measured by two methods. The temperature variation of the integrated intensities of Bragg reflections from powder specimens (method 1) were measured in the temperature range 298–668 °K for Ba(NO3)2 and 298–659 °K for Sr(NO3)2. Using these integrated intensities ϑM values of Ba(NO3)2 and Sr(NO3)2 were extracted to be 170±7 and 195±9 °K, respectively. The room-temperature (298 °K) Debye temperatures for Ba(NO3)2 and Sr(NO3)2 were determined to be 180±8 and 188±8 °K, respectively, from integrated intensities of selected Bragg reflections (method 2).
The dynamics of air breakdown initiated by a particle in a laser beam
Authors: Lencioni D. E. , Pettingill L. C.
Published: February 2003

An experimental study was made of air breakdown induced by a single 50-μm particle at the focus of a 5-J pulsed 10.6-μm laser beam. The breakdown thresholds for 50-μm carbon and NaCl particles were ?5×107 and 8×107 W/cm2. The dynamics of plasma formation were studied with an image-converter camera. At low intensities the plasma grew as an axisymmetric volume surrounding the particle. At higher intensities the plasma formed as a thin disk which propagated towards the laser. The growth rates were measured as a function of beam intensity. The transmitted laser energy was measured as a function of beam parameters and compared to an idealized dynamics model.
Orthorhombic elastic constants of an NbTi/Cu composite superconductor
Authors: Ledbetter H. M. , Read D. T.
Published: February 2003

Elastic properties of a niobium-titanium-filament copper-matrix composite superconductor were studied experimentally at room temperature. Ultrasonic pulse and resonance measurements showed the material has orthorhombic symmetry and, therefore, nine independent elastic constants. With respect to copper, C11, C22, and C33 are about 7% lower; C44, C55, and C66 are about 15% lower; the off-diagonal elastic constants are the same; and the bulk modulus is about 5% lower. Deviations from isotropic elastic behavior are small.
High-current vacuum arc column motion on rail electrodes
Authors: Boxman Raymond L.
Published: February 2003

Experimental observations were made of the motion of the arc column sustained between Cu electrodes in a vacuum ambient when driven with currents of 1.5–35 kA. Arc-column velocities in the positive Amperian direction of (0.1–3.5) ×103 m/s were observed in a self-magnetic-field of approximately 50 G/kA with currents of 2–8 kA. The arc motion was observed to be erratic when a dc uniform external field of 450 G was superimposed on the self-field. When the arc was trapped between the self-field and an external nonuniform dc field, the arc located itself such that the net magnetic force upon it was zero. When the self-field exceeded the maximum external field, a transition from a constricted to a diffuse discharge was observed.
Torsional vibrations of laminated bars
Authors: Behrens E. W.
Published: February 2003

The results of an exact theory describing torsional vibrations of thin laminated bars are presented. It is verified experimentally with the torsion pendulum by measuring the complex shear modulus of isotactic polypropylene in the β-transition range, using homogeneous polypropylene bars as well as one- and two-sided steel/polypropylene laminates as test specimens. The method is then used for determining the complex shear modulus together with the complex Young’s modulus of isotactic polypropylene at audio frequencies from torsional and flexural resonances vibrations of two-sided steel/polypropylene laminates.
Photoelectrolysis and physical properties of the semiconducting electrode WO2
Authors: Butler M. A.
Published: February 2003

The behavior of semiconducting electrodes for photoelectrolysis of water is examined in terms of the physical properties of the semiconductor. The semiconductor-electrolyte junction is treated as a simple Schottky barrier, and the photocurrent is described using this model. The approach is appropriate since large-band-gap semiconductors have an intrinsic oxygen overpotential which removes the electrode reaction kinetics as the rate-limiting step. The model is successful in describing the wavelength and potential dependence of the photocurrent in WO3 and allows a determination of the band gap, optical absorption depth, minority-carrier diffusion length, flat-band potential, and the nature of the fundamental optical transition (direct or indirect). It is shown for WO3 that minority-carrier diffusion plays a limited role in determining the photoresponse of the semiconductor-electrolyte junction. There are indications that the diffusion length in this low carrier mobility material is determined by diffusion-controlled bulk recombination processes rather than the more common trap-limited recombination. It is also shown that the fundamental optical transition is indirect and that the band-gap energy depends relatively strongly on applied potential and electrolyte. This effect seems to be the result of field-induced crystallographic distortions in antiferroelectric WO3.
Auger recombination in PbTe
Authors: Lischka K. , Huber W.
Published: February 2003

The carrier lifetime τ in PbTe was determined by measuring the decay time of the photoconductivity. The experimental values of τ are compared with a theory for Auger recombination recently presented by Emtage. It has been shown by this author that Auger recombination in semiconductors with a many-valley band structure such as that of PbTe comes principally from the collision of carriers in different valleys of one band. The qualitative fit of experimental and theoretical data shows that Auger recombination is, in fact, an important recombination mechanism in PbTe. This may have a considerable influence on the effectivity of infrared luminescence devices.
Contact printing in amorphous (Gd,Tb,Dy) -Fe alloy films
Authors: Imamura N. , Mimura Y. , Kobayashi T.
Published: February 2003

Some properties of contact printing in amorphous (Gd, Tb,Dy) -Fe alloy films were studied, that is, the amorphous alloy film with the perpendicular easy axis of magnetization was placed in contact with the conventional tape or card and the contact-printed pattern thus obtained was observed by means of the magneto-optical polar Kerr effect. The contact-printed domain pattern had a very high image contrast and was influenced by both the thickness and the saturation field of the amorphous film. The Dy-Fe film had a very low Curie temperature and thus could be used for contact printing by means of the thermal transfer as in the case of CrO2 tape.
Plasma influence in tantalum sputtering
Authors: Chouan Y. , Collobert D.
Published: February 2003

The angular distribution function (ADF) and the sputtering yield have been measured in a triode sputtering system where a dense ionic current (35 mA/cm2) drawn from an argon plasma confined by a magnetic field impinges upon a tantalum target biased at 1.8 keV. The system was placed in a vacuum chamber at a pressure on the order of 10−4 Torr. The results are the following for the two phases of Ta deposited. For α-Ta the ADF is Lambertian but the associated yield is lower than the theoretical one; for β-Ta the ADF curve lies below the Lambertian cosine curve. We suggest the following interpretation based on the influence of impurities. For α-Ta there are many impurities which can be ionized and contribute to the current. Also, these ions destroy the Ar* metastables and, therefore, lower the Ta-Ar* collision probability. For β-Ta there are no impurities. The current is due only to ionized argon and Ar* metastables are not destroyed (i.e., the collision probability is much higher). In such a way, we are able to explain the discrepancies observed in these two cases in terms of both the sputtering yield and the ADF.
Gain spiking and mode-beating control by signal injection in CO2 lasers
Authors: Cason Charles , Werkheiser A. H. , Otto W. F. , Jones R. W.
Published: February 2003

Gain spiking and mode-beating effects in a high-power pulsed CO2 laser have been experimentally shown to be controllable by the injection of a low-power signal. The laser was pumped by a 1-atm 10–100- kW/cm3 discharge controlled by a 175-kV e-beam at 0.4 A/cm2. A line-selectable low-power CO2 laser beam was injected on axis into the relatively large Fresnel number square unstable resonator cavity of the pulsed laser through a centered hole in the primary mirror. Analysis of the pulse output without signal injection showed as many as eight longitudinal modes were present which produced beats. On rare occasions the beat pattern envelope was seen to rise above the gain spike. Injecting a cw plane-polarized 0.3-W P-20 signal into the CO2 oscillator cavity caused the pulsed laser to operate plane polarized at a single frequency for several hundred nsec. Increasing the injected signal power to 5 W caused a substantial suppression of the gain spike. The observed spike suppression was significantly more than that predicted by the one-dimensional model analysis.
X-ray sensitivity of a charge-coupled-device array
Authors: Peckerar M. C. , Baker W. D. , Nagel D. J.
Published: February 2003

The quantitative response of a charge-coupled device (CCD) to x rays in the 5–14-keV range was measured and computed. Comparison of experimental and theoretical quantum efficiencies provides a method to determine electron diffusion lengths in these devices. Compared to a common x-ray film, the CCD amplifier combination tested in this work has a similar threshold and significantly smaller range of response. The CCD offers somewhat poorer spatial resolution than the x-ray film. Comparisons of the CCD with other active x-ray detectors are also presented.
The influence of transverse magnetoresistance on Hall-effect measurements on n-type germanium and other semiconductors
Authors: Partain L. D. , Lakshminarayana M. R. , Westgate C. R.
Published: February 2003

The conditions under which magnetic field reversal and voltage averaging can be used to eliminate the contributions of transverse magnetoresistance to Hall voltage measurements have been generalized. The conditions are shown to be satisfied for three specific orientations of the magnetic field to the crystallographic axes of n-type germanium. In general, the conditions are demonstrated to be met in any crystal material with a cubic structure if the magnetic field is applied in a direction parallel to a crystallographic axis of threefold or fourfold rotational symmetry. At sufficiently high fields it is shown that magnetoresistance contributions can be made negligibly small regardless of the B-field orientation to the sample’s crystal structure. Experimental data on n-type germanium at 77 °K verifies the validity of the theory by demonstrating that magnetoresistance contributions are cancelled by averaging when the magnetic field is parallel to a highest-symmetry 〈100〉 crystal axis direction as well as parallel to a lower-symmetry 〈110〉 direction.
Electrochemical doping of silicon with arsenic
Authors: Antula Jovan
Published: February 2003

The results of the depth-profile analysis of p-type silicon, electrolytically doped with arsenic, show in the semilogarithmic representation a straight-line depth profile. An example is presented, where a predeposition of arsenic was carried out electrochemically and then driven in by diffusion.
Thickness dependence of internal voltage in metal-insulator-metal structure with dissimilar electrodes
Authors: Gupta S. K. , Singal C. M. , Srivastava V. K.
Published: February 2003

A study of the thickness dependence of internal voltage in a metal-insulator-metal structure with barium stearate as the dielectric film has been carried out with aluminum and tin electrodes and the internal voltage has been found to decrease linearly with thickness of the dielectric film. The internal voltage is directly related to the difference of the work function of the two metals when the dielectric film has no net dipole moment. For the case when the insulator has a net dipole moment, the internal voltage is found to increase when aluminum is the bottom and tin the top electrodes. The measured internal voltage is found to be consistent with that derived from the study of tunneling currents.
Critical currents in liquid-quenched Nb3Al
Authors: Lo K. , Bevk J. , Turnbull D.
Published: February 2003

Critical current densities of over 1.8×106 A/cm2 at 4.2 °K and 150 kG have been achieved in Nb3Al tapes rapidly quenched from the liquid state at rates of 105–106 °C/sec. The superconducting transition temperature is about 16 °K, indicating a relatively high degree of order, and increases to 18.4 °K upon annealing at 750 °C. The observed microstructure depends sensitively on the quenching rate and consists of small submicron grains surrounded by a thin boundary layer of different composition. The grain size is roughly inversely proportional to the temperature gradient during quenching. The quoted critical current densities, the highest observed to date in any superconductor, should be regarded as a lower limit of the material critical value imposed by the heating problems due to the contact resistance.
Slow magnetic domain wall motion
Authors: Baldwin John A. , Milstein Frederick , Wong Russel C. , West James L.
Published: February 2003

The speed u of slow magnetic domain wall motion has been measured as a function of applied field, H, over the interval 3.4×10−7⩽u⩽0.24 m/s at room temperature. It is found that speed does not vary exponentially with field although it may be approximated as such over restricted intervals. The data are analyzed both from the point of view of thermally activated motion and also quantum-mechanical tunneling. It is found that the formalisms of these two cases are identical. They differ only in the definition of a characteristic distance l. It is concluded that thermal activation is more likely than tunneling to be the mechanism that is operative at room temperature.
Field calibration using the energy distribution of a free-space field ionization
Authors: Sakurai Toshio , Müller Erwin W.
Published: February 2003

Utilizing free-space field ionization, a new method of field calibration for field ion emitters has been developed. Plotting the differences of relative energy deficits of free-space ionized H2, D2, or Kr for sets of various applied voltages V against the logarithm of the voltage ratios yields a field factor k from which the surface field F0=V/krtip is obtained with 3% accuracy. Refinement of this method also enabled us to determine the local radii of the specimen tip. In addition to new and more reliable data of evaporation fields of various materials, such as W, Mo, Rh, Ir, Pt, and Ni, it has revealed several significant facts on the geometrical shape of the emitter.
Optical thickness measurement of very thin films with a Fabry-Perot interferometer
Authors: Huang Wei-tze , Zitter R. N.
Published: February 2003

It is proposed here that the Fabry-Perot interferometer be used for optical thickness measurements of very thin (<100 Å) dielectric films and membranes. It is also pointed out that a Fabry-Perot might be able to detect the small change in the refractive index of a live axon during the passage of an action potential in biophysical studies.
Dissociation of fluorine by electron impact
Authors: Chen Hao-Lin , Center R. E. , Trainor Daniel W. , Fyfe W. I.
Published: February 2003

Using a previously developed F-atom diagnostic technique, the efficiency of F2 dissociation by an electron beam or an electron-beam-sustained discharge was systematically studied. By monitoring the transient concentration of ions generated during the electron-beam-sustained discharge, we have determined the F−+F+2 ion-ion recombination and F2 dissociative attachment rate constants at various E/P conditions. The dissociative attachment rate constant of F2 at an average electron energy of 1 eV was found to be about (2.3±0.3) ×10−9 cm3/molecule sec−1 and increased with decreasing electron energy. The F−+F+2→3F recombination rate constant at an E/P of 18 kV/cm/atm was found to be about (1.5±0.2) ×10−8 cm3/molecule sec−1 and also increases with decreasing E/P values. The sustained-discharge enhancement of F-atom production from these experiments is F2 is small, ∼1.7.
Numerical calculations of focal and aberration properties of unipotential electron lenses
Authors: Saito Tsunenari , Sovers Ojars J.
Published: February 2003

Focal properties and aberration coefficients of equidiameter unipotential electron lenses are calculated by numerical solution of Laplace’s equation and the electron trajectory equations. A wide range of central electrode length-to-diameter ratios is investigated. The variation of focal and aberration properties with lens geometry is well described by relatively simple analytic functions, which are found to be useful in practical lens design problems. Agreement with experimentally measured focal properties is excellent.
Analytical solutions for laser heating and burnthrough of opaque solid slabs
Authors: Harrach Robert J.
Published: February 2003

The thermal response of an opaque solid slab exposed to intense laser radiation is described using the heat-balance integral method. Approximate analytical solutions are obtained for the one-dimensional temperature distribution T (x,t), for the velocity ?s(t) of the moving vapor-phase boundary, and for various characteristic quantities such as the front-surface vaporization time tv, the time tl required for heat to diffuse through the sample to the back surface, and the slab burnthrough time tBT. Account is taken of the influence on tl and tBT of partial vaporization of the target material. The thermophysical properties of the target are assumed to be constant independent of temperature, but the theory accommodates a time-varying laser intensity and a temperature-dependent surface absorptivity. Illustrative calculations are presented which compare the results of this theory to those derived from heat-transfer computer programs. These include a treatment of laser heating of an aluminum slab with temperature-dependent absorptivity and calculations of the time required to burn through aluminum, stainless-steel, and carbon-phenolic targets, covering a wide range of values of target thickness and laser intensity.
Determination of predominant carrier species in organic polymers by a galvanic cell
Authors: Sawa Goro , Inayoshi Tatsuhiro , Nishio Yoji , Nakamura Shyuhei , Ieda Masayuki
Published: February 2003

A novel method for determining the predominant carrier species in organic polymers is presented using a galvanic cell consisting of the Cu-Au-polymer-Al-Cu system. It can be concluded that the ionic conduction is predominant at a low electric field, if the open-circuit voltage of the galvanic cell is almost independent of temperature and if the conduction current of the Au-polymer-Au system and the short-circuit current of the galvanic cell give identical temperature dependence. The results on nylon 66 and 7,7,8,8,-tetracyanoquinodimethane complex salt of poly(N-xylylene, N,N′-piperazinium) are presented.
Laser vaporization of metal films–Effect of optical interference in underlying dielectric layers
Authors: North J. C.
Published: February 2003

The interference of incident laser light with light reflected from dielectric interfaces plays an important role in the completeness with which a laser beam vaporizes thin metal films, even though the dielectric layers lie underneath the metal film being vaporized. A structure consisting of titanium-platinum links on a two-level dielectric consisting of silicon nitride and silicon dioxide on a silicon substrate was used to demonstrate the effect. The resistance of the titanium-platinum links after vaporization by pulses of 1.06-μm light from a Q-switched YAG laser varied by more than seven orders of magnitude as the thickness of the silicon dioxide, the lower dielectric, was varied. Photographs are included which show visible variations in the effect of the laser pulses. The experimental results are correlated with the calculated resultant light intensity at the surface of the dielectric layers. This intensity varies from 0.07 to 1.6 times the incident beam intensity depending upon the thicknesses of the two dielectric layers.
Temperature dependence of photoluminescence from Mg-implanted GaAs
Authors: Yu Phil Won , Park Y. S.
Published: February 2003

Photoluminescence emission characteristics from Mg-implanted GaAs are presented for the temperature range T=4.2–293 °K. The emission due to recombination of free electrons with holes bound to neutral Mg acceptors is a dominant radiative process in heavily implanted samples at temperatures T≲210 °K. Changes in the emission energies and intensities as a function of temperature lead to the determination of the binding energy of Mg as 28±2 meV. The donor-acceptor pair band involving Mg, which has a large energy shift with the change of excitation intensity, shows the lower-energy shift with an increase of temperature in the range T=4.2–50 °K. This is explained by associating deeper donor states than the hydrogenic donors to the donor-acceptor pair band. Depth dependence of the donor-acceptor pair and the free-electrons to the neutral Mg acceptor bands show a deep penetration of Mg acceptors.
Intense tunable ir generation by four-photon mixing in germanium
Authors: Lee N. , Aggarwal R. L. , Lax B.
Published: February 2003

We have considered the method of noncollinearly phase-matched four-photon mixing of CO2 laser beams in germanium at room temperature for the generation of intense tunable or quasitunable pulses of infrared radiation. Our theoretical analysis shows that it should be possible to obtained output intensities of multi-MW/cm2 in the 8-μm region with conversion efficiencies as high as 37%. In the initial experiments reported here, we have observed as much as 33 mJ of energy per pulse (corresponding to a peak pulse intensity of ∼0.3 MW/cm2) at 8.6 μm from a 10-cm-long antireflection(AR) -coated crystal using CO2 laser beams of ∼10-MW/cm2 intensity. This corresponds to a conversion efficiency of ∼1%. We have also examined several other practical aspects of this four-photon mixing technique. Use of single-mode CO2 lasers should provide a step-tunable ir radiation with linewidth much less than 0.01 cm−1. A simple analysis of the heat dissipation from the germanium crystal into a copper block indicates that the temperature rise is only a few degrees even at pulse repetition rates of several hundred Hz. Thus, the noncollinear four-photon mixing scheme should find important applications in laser photochemistry.
Photovoltaic properties and junction formation in CuInSe2
Authors: Tell B. , Bridenbaugh P. M.
Published: February 2003

Studies of diffusion and photovoltaic effects in CuInSe2 p-n junctions are reported. Junctions were formed by annealing Zn-, Cd-, and Cu-plated p-type samples at temperatures from 200 to 450 °C. The most efficient photodetectors are formed by 5–10-min anneals at 200 °C with a calculated interdiffusion coefficient of ∼5×10−10 cm2/sec.
High-efficiency graded-band-gap Ga1−xAlxAs light-emitting diodes
Authors: Dawson L. Ralph
Published: February 2003

A new simple-geometry (sawed rectangular parallelopiped) Ga1−xAlxAs LED having external quantum efficiency as high as 27% has been developed. The material is prepared by a single-step multiple-slice liquid-phase-epitaxy technique and contains a steep Al composition gradient. This gradient is exploited by removing the GaAs substrate and extracting photons from the first-to-grow side of the epitaxial material along a path of very low absorption. The spectral distribution of these LED’s can be varied over a broad range. Accelerated aging studies indicate very high reliability for these devices.
A study of the optically produced hexagonal pattern on ZnO single crystals
Authors: Lin T. T. , Lichtman David
Published: February 2003

A hexagonal spot pattern (or light figure) was observed on ZnO single crystals during an Auger electron spectroscopy (AES) study. It is known that blue-green luminescence excitation can be produced in ZnO by electron bombardment. Thus, the electron bombardment provides an alternative internal luminescence light source to produce the light figure on the etched ZnO crystals. A main feature of the electron-induced luminescence light figure is characterized by a missing central spot. A detailed comparison of the similarities and differences between the light figure produced by electron bombardment and by illuminating with an external collimated light beam is given. An overall consistent picture between these two types of light figures can be drawn and understood on the basis of ray tracing. Though both the O polar face and Zn polar face show distinguishable etched structures, the result shows that the forming of the light pattern is mainly due to the existence of the hexagonal pyramidal etched structure on the O polar face.
Gas breakdown initiated by laser radiation interaction with aerosols and solid surfaces
Authors: Smith David C.
Published: February 2003

The threshold for generation of high-density plasma caused by the interaction of laser radiation with solids is examined theoretically. The developed semiquantitative model is applicable for predicting the threshold for generating laser-supported absorption waves, absorbing plasma produced on surfaces with high-intensity laser radiation, and also for predicting the threshold of aerosol-induced gas breakdown, commonly referred to as dirty air breakdown. In developing the model, the vapor density generated by laser interaction with the solid is calculated and then the intensity required to cascade ionize the vapor to full ionization is calculated. Analytic expressions are derived for the breakdown intensity which show the parametric dependence of the threshold. Since the vapor density is a function of laser intensity, and characteristics of the solid, different parametric dependence of the threshold on wavelength, pulse length, and particle characteristics is predicted compared to those determined by previous theoretical models of gas breakdown. Comparison of the threshold predicted by the model agree within a factor of 2 of experimental data for a wide range of experimental conditions including laser pulse duration from 10 nsec to cw, particle sizes from 0.1 μ to laser spot sizes of 1 cm, and wavelength scaling of 1.06–10.6 μ wavelength. Based on the good agreement between theoretical predictions and experimental data, the model can be used to predict thresholds for plasma production for a wide variety of atmospheric and solid-surface conditions.
Ion densities in a positive column He-Cd+ laser discharge
Authors: Mori M. , Takasu K. , Goto T. , Hattori S.
Published: February 2003

By combining the modified absorption method with the modified double-probe method, the He+ and Cd+ ion densities in a cataphoresis type of positive column He-Cd+ laser discharge were separated without using the Cd+ ion mobility. They agreed with the He+ and Cd+ ion densities calculated on the basis of the electron energy distribution function in the He-Cd discharge well.
Interdiffusion in composition-modulated copper-gold thin films
Authors: Paulson Wayne M. , Hilliard John E.
Published: February 2003

Vapor-deposited Cu-Au thin films were produced containing composition modulations with wavelengths between 8 and 26 Å. The modulations produced satellite peaks in the x-ray diffraction patterns. Amplification factors and the corresponding diffusion coefficients were obtained by measuring the decay rate of the satellite intensities. The amplification factor reached a maximum at 17 Å and decreased at both shorter and longer wavelengths. Interdiffusion coefficients between 10−21 and 10−19 cm2/sec were measured over the temperature range 200–260 °C. The effective diffusion coefficient is linearly dependent on the function B2(λ) for λ≳10 Å. From the wavelength dependence of the measured diffusivities, a gradient-energy coefficient of −4.7×10−6 erg/cm was obtained and is in good agreement with theoretical estimates. These experimental results were compared with the predictions from a proposed model for diffusion on cubic lattices.
Metal-nonmetal transition in NiS under pressure
Authors: Anzai S. , Ozawa K.
Published: February 2003

The thermodynamical model of Lidiard for an itinerant antiferromagnet is extended to involve the strain energy and the volume dependence of the energy gap between up- and down-spin bands. The model is manipulated to fit the pressure effect of metal-nonmetal transition temperature and its first-order characteristics in NiS. Here, the volume compressibility used is measured to be 1.1×10−3 kbar−1. Changes in magnetic moment on the Ni sublattice and in enthalpy at the transition temperature are calculated from the obtained parameters and compared with the available experimental data. The nature of metal-nonmetal transition in NiS under pressure is discussed. Present study constitutes the first attempt to understand the energetics of the metal-nonmetal transition in NiS throughout its T-P diagram.
Second- and third-order piezoelectric stress constants of lithium niobate as determined by the impact-loading technique
Authors: Graham R. A.
Published: February 2003

Determination of the e22, e33, and e15 second-order piezoelectric stress constants, several third-order piezoelectric stress constants, and the cD11 and cD33 elastic stiffness constants are reported for lithium niobate from experiments with input strains from 7×10−4 to 8×10−3 produced by the elastic impact-loading method. Measurements of the e33 constant were made on a large number of samples to establish sample uniformity. The differences were found to be less than 1%. The present value of e33 is higher than that reported in previous work and appears to call for a revision of the accepted value along with that of the elastic constant cE33. The third-order piezoelectric stress constants are readily detectable, but the values determined in the present investigation are limited in accuracy due to the relatively low strains which could be applied to the samples before conductivity became excessive.
Molecular-beam sampling of a hollow-cathode discharge in argon as a plasma diagnostic and a source for fast neutrals
Authors: Theuws P. G. A. , Beijerinck H. C. W. , Schram D. C. , Verster N. F.
Published: February 2003

Velocity analysis of the molecular beam is done with a time-of-flight method. The measured velocity distribution of the fast neutral atoms is described by the sum of two Maxwell-Boltzmann distributions with temperatures on the order of 0.25 and 1 eV, respectively. This bimodal distribution is attributed to an overpopulation of the high-energy tail of the ion velocity distribution. The measured intensities of the fast neutrals vary between 5×1014 and 7×1015 (molecules s−1 sr−1).
Ion current reduction in pinched electron beam diodes
Authors: Quintenz J. P. , Poukey J. W.
Published: February 2003

A new version of a particle-in-cell diode code has been written which permits the accurate treatment of higher-current diodes with greater physical dimensions. Using this code, we have studied ways to reduce the ion current in large-aspect-ratio pinched electron beam diodes. In particular, we find that allowing the ions to reflex in such diodes lowers the ion to electron current ratio considerably. In a 3-MV R/d=24 case this ratio was lowered by a factor of 6–8 compared with the corresponding nonreflexing-ion diode, while still producing a superpinched electron beam.
Cataphoretic distributions of Zn and F in a ZnF2-He positive-column discharge
Authors: Gokay M. Cem , Cross Lee A.
Published: February 2003

Measurements of the longitudinal distributions of Zn and F atoms in a positive-column helium discharge tube have been made using ZnF2 as a source in a conventional appendage reservoir. It has been shown that while the cataphoresis of Zn+ ions is mainly responsible for determining the Zn longitudinal distribution, the cataphoresis of F− ions probably formed by capture of free electrons from the discharge by F atoms strongly influences the distribution of F atoms. The application of metal-fluoride–noble-gas discharges to further metal-vapor laser research is discussed.
Half-width and peak-intensity measurement of a rocking curve obtained from silicon on sapphire using soft x-ray beams
Authors: Kishino Seigô , Iida Shinya , Aoki Shigeru , Mizutani Tatsumi , Watanabe Tetsuo
Published: February 2003

The crystalline quality of a silicon film on a sapphire substrate (SOS) is investigated by measuring both a half-width and a peak intensity of a rocking curve using a double-crystal arrangement. Contrary to conventional techniques, it is confirmed that an asymmetric diffraction technique using a soft x-ray beam (TiKα1) enables the sampling of only a surface layer within 0.12 μm. The improved technique is successfully applied to SOS wafers. As a result, the half-width is found to correlate with both a fault density and a Hall mobility. On the other hand, the intensity has a correlation with an interstitial Al content in the film which is introduced by autodoping during growth.
New method of detection of weak anharmonic modes of a quartz crystal and its applications for generating multicrystal resonance frequencies
Authors: Bahadur Harish , Parshad R.
Published: February 2003

An experimental method has been described for detection of various oscillating modes of a quartz crystal and accurate measurement of their resonance frequencies. In effect, a parallel tunable L-C circuit is coupled to the quartz crystal in a crystal oscillator circuit. As the L-C resonant frequency approaches one of the crystal mode resonance frequencies, the crystal takes control and makes the crystal oscillator circuit generate this frequency. The method, thus, not only enables accurate determination of crystal mode resonance frequencies but also permits generation of a number of stable frequencies using a single quartz crystal.
Critical field variations for domain-wall motion in ferroelectric/ferroelastic Gd2(MoO4)3
Authors: Tosima S. , Nishikawa M.
Published: February 2003

The critical field Ec for domain-wall motion in ferroelectric/ferroelastic gadolinium molybdate has been studied. Metal-film electrodes were evaporated onto the samples at around room temperature. The measured critical field depends strongly on the particular location X0 of the domain wall before the measurement is made. Ec tends to be high for wall motion away from X0 and low for motion towards X0. When the wall is shifted from X0 and kept for a time at a new position, Ec relaxes to a new value in the region traversed by the wall. The average value of Ec for both directions of motion is 1.4±0.2 kV/cm, essentially uniform in space and constant in time, despite the nonuniform distribution and the relaxation of Ec for each direction of wall motion.
Optical properties of arc-evaporated carbon films between 0.6 and 3.8 eV
Authors: Arakawa E. T. , Williams M. W. , Inagaki T.
Published: February 2003

Ellipsometric measurements have been performed at room temperature on arc-evaporated carbon films between 0.6 and 3.8 eV. Previously published data on evaporated carbon films are reviewed and a comparison made between the present data and those for glassy carbon over the same energy range.
Crystal orientation and temperature effects on Pd2Si-Si Schottky-barrier diodes formed by solid-phase epitaxy
Authors: Das R. M. , Neville R. C.
Published: February 2003

Silicon solid-phase epitaxy utilizing Pd2Si as a transport medium is shown to be dependent on the substrate orientation and postepitaxial heat-treatment temperature. It is demonstrated that devices fabricated on (1-0-0) substrates are superior to devices made on (1-1-1) substrates.
Temperature- and time-dependent properties of polycrystalline (Li,Na)NbO3 solid solutions
Authors: Zeyfang R. R. , Henson R. M. , Maier W. J.
Published: February 2003

Pressure-sintered LixNa1−xNbO3 in the range 0.015⩽x⩽0.15 exhibits electromechanical properties amenable to high-frequency device applications with radial-frequency constants fR(r) between 1.75 and 1.95 kHz m, coupling coefficients up to 0.4, and permittivities between 100 and 200. The temperature and time dependencies of fR are shown to be strongly related to composition, where for x=0.12, the temperature coefficient between −40 and 80 °C is −2×10−4 °C−1 and the ageing coefficient is −2.5×10−3 per decade. The results are discussed in relation to composition and with respect to anomalies at phase transitions in (Li,Na)NbO3.
Laser (cw CO2) -induced electrical damage in Ge and Si
Authors: Gulati S. K. , Grannemann W. W.
Published: February 2003

This paper presents the experimental results on the electrical studies of cw CO2 laser-induced damage in Ge and Si. The damage first appears at the surface of the semiconductor and penetrates the bulk, creating defects that cause carrier removal and mobility degradation. The defects so created are more active at lower temperatures than at room temperature, as seen from the mobility-vs-temperature curves before and after laser damage. Carrier removal and mobility degradation curves appear qualitatively to be similar to those observed for electron, neutron, and γ-ray damage. The experimental results can be satisfactorily explained by assuming the creation of vacancy and interstitial pairs and applying the model of James and Lark-Horovitz.
On the optimization of electron-emitting arrays
Authors: Nordgard John D.
Published: February 2003

The field emission current anticipated from a planar array of brushlike protrusions of needle-shaped conducting metallic pins embedded in an insulating dielectric substrate is studied as a function of the array packing density with pin height, pin cross-sectional area, pin tip geometry, pin base geometry, pin spacing, and pin anode spacing as parameters. Spheroidal models of the emitters are presented to analyze the total macroscopic current emitted by the pin array before and after arcing. An optimum array packing density to maximize the total macroscopic current is shown to exist and is determined for various typical pin heights in the range 4–40 μm.
Scale-up of NF(a1Δ) produced by the H+NF2 system in a subsonic cw laser device
Authors: Herbelin John M. , Spencer Donald J. , Kwok Munson A.
Published: February 2003

A peak density of the electronically excited free-radical species NF(a1Δ) of 2.4×10−9 mol cm3 has been chemically produced in a subsonic laser device. This high concentration confirms previous analyses and predictions of the chemical system. This is a concentration scale-up of 104 from previous flow-tube results.
Electromechanical stress analysis of transversely isotropic solenoids
Authors: Gray W. H. , Ballou J. K.
Published: February 2003

The mechanical behavior of superconducting magnets deviates from isotropy due to their construction techniques, which involve layering superconductor, insulation, and sometimes structural reinforcement within the windings. Previous mechanical analyses considered the windings of a magnet to behave isotropically. This paper describes an analytical solution for the deflection, stress, and strain of axisymmetric electromechanically loaded rotationally transversely isotropic solenoids. The results indicate that for magnets with a large radial build compared to inner radius, transverse isotropy has a dramatic effect upon the mechanical response to load; for magnets with a small radial build compared to inner radius, transverse isotropy has a negligible effect.
Buckling and vibrations in a five-coil superconducting partial torus
Authors: Swanson C. , Moon F. C.
Published: February 2003

Further experimental results are presented on the phenomenon of magnetoelastic buckling of superconducting magnets. A 46-kA five-coil superconducting partial torus is described. Experiments show that the three 20.3-cm-diam flexible coils in the torus become elastically unstable at a critical value of the current. The model is also used to measure torques on the toroidal magnets produced by pulsed poloidal field coils. These tests are designed to check out numerical analyses of buckling and vibration in full-scale magnetic fusion reactors.
Low-temperature film thickness measurements by a quartz thickness monitor
Authors: Barrett P. H. , Pasternak M.
Published: February 2003

A quartz-crystal thickness monitor was successfully applied at low temperatures (5–80 K) and used to determine the areal density of condensed CH4, N2, CO2, Ar, Kr, and Xe. The frequency-shift dependence on the deposited mass was calibrated using the x-ray absorption technique. The stability, reproducibility, and temperature variation of the resonance frequency in the 5–300 K temperature range are discussed.
Recombination lasers from cooled hydrogenlike plasmas
Authors: Jones W. W. , Ali A. W.
Published: February 2003

Time-dependent inversion density and gain calculations are presented for n=2→1 and some n=3→2 transitions for cooled He+ to C5+ plasmas. The effects of radiation and the plasma cooling on the inversion density and gain coefficient are emphasized.
Lateral mode selection in semiconductor injection lasers
Authors: Wittke James P. , Ladany I.
Published: February 2003

Various methods have been used to control the lateral modes of injection lasers. We report on lateral mode selection in continuous-wave double-heterojunction lasers using the differential diffraction losses of different modes at a narrow reflector stripe on one emitting facet. Power output curves and far-field beam patterns scanned in the lateral (junction) plane are shown both before and after an antireflection coating was deposited on one facet except in a narrow stripe. The stripe defines the mode-selecting reflective region. Calculations, based on a simple model of DH injection lasers, are made by estimating the magnitude of the effect. Output powers of 12 mW from one facet were obtained.
Reply to ’’Comment on ’Permeation of helium and hydrogen from glass-microsphere laser targets’ ’’
Authors: Souers P. Clark
Published: February 2003

An ensemble of glass microbubbles at constant temperature does not show straight exponential outgassing, but instead tails out. The curvature of this tail may be related to the distribution of permeability time constants in the ensemble.
Electromagnetic surface waves at the interface of a relativistic electron beam with vacuum
Authors: Shoucri M. M. , Gagné R. R. J.
Published: February 2003

The dispersion relation for electromagnetic surface waves propagating at the interface between a relativistic electron beam and vacuum is derived. The excitation of surface modes in a plasma at rest by a relativistic electron beam is discussed.
Behavior of porous tungsten under shock compression at room temperature
Authors: Dandekar Dattatraya P. , Lamothe Roger M.
Published: February 2003

This work reports the results of room-temperature shock-compression experiments on porous tungsten. The porous tungsten was fabricated by sintering 1-μm tungsten particles. The initial density of the material was 15290 kg/m3. Around 97% of the pores in the material were interconnected. The main features of the results are as follows: (1) porous tungsten behaves as a linear elastic material to 1.43 GPa; (2) the shock wave following the elastic precursor is unstable in the material in the stress range 1.43–2.7 GPa; (3) a stable two-wave structure is established at and above 6.4 GPa; (4) the response of porous tungsten is accurately described by the Mie-Grüneisen equation of state at stresses above 4.9 GPa, the stress at which the voids suffer a complete extinction in the material; (5) the deformations induced in the material due to shock compression are irreversible; (6) the recentered Hugoniot of porous tungsten becomes stiffer with the increasing magnitude of initial compressive stress.
Growth mechanism for solid-phase epitaxy of Si in the Si 〈100〉/Pd2Si/Si(amorphous) system studied by a radioactive tracer technique
Authors: Pretorius R. , Liau Z. L. , Lau S. S. , Nicolet M-A.
Published: February 2003

A tracer technique using radioactive 31Si (T1/2=2.62 h) was used to study solid-phase epitaxial growth (SPEG) of silicon. After depositing Pd and Si onto single-crystal substrates which had been activated in a nuclear reactor, Pd2Si was formed with about equal amounts of radioactive and nonradioactive silicon during heating at 400 °C for 5 min. After a second annealing stage (450 °C→500 °C in 1 h) the silicide layer which moves to the top of the sample during SPEG was etched off with aqua regia. From the absence of radioactive 31Si in the etchant solution it is concluded that SPEG takes place by dissociation of the Pd2Si layer at the single-crystal interface to provide free Si for epitaxial growth, while new silicide is formed at the interface with the amorphous Si. These results were confirmed by evaporating radioactive silicon onto nonactivated silicon substrates before evaporation of Pd and stable amorphous Si and by measuring the activity in the SPEG sample before and after etching off the silicide layer.
Thermal oxidation of silicon in various oxygen partial pressures diluted by nitrogen
Authors: Kamigaki Y. , Itoh Y.
Published: February 2003

Oxide growth kinetics of SiO2 films grown on silicon at 950 to 1100 °C in an O2/N2 mixture is empirically studied. It is found that a linear-parabolic law is in excellent agreement with the oxidation data under the oxygen partial pressure PO2 of 1 or 10−1 atm. However, a parabolic law is obtained at 10−2 atm, and an inverse-logarithmic law at 10−3 atm. The Mott-Cabrera oxidation rate equation is adapted to the thermal oxidation of silicon in the case of PO2≲10−2 atm. Finally, 43.9 kcal/mole is derived as the activation energy value of silicon atoms entering into the oxide.
Some electrical and optical properties of ferroelectric lead-zirconate–lead-titanate thin films
Authors: Okada Akira
Published: February 2003

Ferroelectric and transparent thin films of lead-zirconate–lead-titanate (PZT) were fabricated by rf diode sputtering. The substrates used were platinum, fused quartz, and In2O3-coated fused quartz, but no substantial difference on the film properties was observed. Films deposited at substrate temperatures below 300 °C were amorphous. At substrate temperatures of 350–450 °C the films crystallized in a pyrochlore structure. Films deposited at above 500 °C showed a perovskite structure and ferroelectric properties. The measured dielectric constant of the ferroelectric PZT was 751. Spontaneous polarization of the film was 26.1 μC/cm2 and the Curie temperature was 325 °C. The coercive field and remanent polarization were found to be 23.3 kV/cm and 20.4 μC/cm2, respectively. The refractive index of the perovskite PZT film was 2.36 at 6328 Å, and the absorption edge was found to be at 2950 Å. The edge of the pyrochlore film was at 3300 Å. Optical waveguiding properties of the PZT thin film were investigated at 6328 Å, but attenuation was impracticably large.
Microwave cavity-perturbation equations in the skin-depth regime
Authors: Ong N. P.
Published: February 2003

The frequency shift and loss of a microwave cavity for ellipsoidal samples in the skin-depth regime are calculated using the surface impedance concept. Equations qualitatively different from the widely used quasistatic equations are obtained when the skin depth is much smaller than the sample dimensions. These results agree with more rigorous calculations on spherical samples in the skin-depth regime. A geometrical representation based on the Smith Chart is developed as an aid to the analysis of experimental data for low-loss samples.