bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic Constants of Hexagonal BeO, ZnS, and CdSe
Authors: Cline Carl F. , Dunegan Harold L. , Henderson Glenn W.
Published: January 2005

The elastic moduli of hexagonal beryllium oxide, zinc sulfide, and cadmium selenide at 25°C have been determined by measuring ultrasonic wave velocities in the 20- to 50-MHz frequency range. The data are compared with other literature data and discrepancies are discussed. The adiabatic bulk modulus, volume compressibility, and Debye temperatures are also computed.
Electrical Performance of Metal-Insulator-Piezoelectric Semiconductor Transducers
Authors: Fiebiger J. R. , Muller R. S.
Published: January 2005

The theory underlying the operation of metal-insulator-piezoelectric (MIPS) electromechanical transducers is verified experimentally for time-varying loads on devices made from CdS piezoelectric film materials. Experimental transducers exhibit sensitivities of the same order as those observed under static loading within times shorter than one microsecond after the application of mechanical stress. The frequency limitations for the transducer appear to be determined by the electrical properties of the MOS structure. The MIPS effect is demonstrated experimentally in CdSe transducers. Transducers fabricated on a flexible polyimide film are described, and a microphone embodying this construction is discussed. Transducers made with CdS films have properties which are more reproducible than are obtained from transducers using CdSe films. X-ray studies show this result to be linked to crystal structure in the semiconductor layers.
Magnetostriction and Compositional Gradients in Boat-Evaporated Permalloy Films
Authors: Penn T. C. , West F. G.
Published: January 2005

Magnetostriction measurements on Permalloy films prepared by vacuum evaporation from a tungsten boat indicate an average Fe enrichment of about 2% above the original melt composition. In addition it is shown that the film composition varies continuously through the thickness from 4% to 7% per 1000 Å for typical evaporation conditions. Compositional gradients of even smaller magnitude are capable of pinning spin waves. Since filament and boat evaporation are used widely in preparing laboratory films, the anomalous spin-wave results frequently reported in the literature may be due to thickness-compositional gradients.
Steady Laminar Flow of Elasticoviscous Liquid through a Pipe with Suction or Injection
Authors: Mishra Shankar Prasad , Roy Jyotirmoy Sinha
Published: January 2005

The problem of steady laminar flow of elasticoviscous liquids through a porous pipe in the presence of suction or injection has been studied in this paper. The perturbation method has been used to obtain the axial velocity regarding the Reynolds number `R' as the perturbation parameter. The effect of elastic elements in the viscous liquid on the axial velocity, axial pressure drop, and the shearing stress have been shown graphically.
Depletion-Layer Capacitance of p+n Step Junctions
Authors: Gummel H. K. , Scharfetter D. L.
Published: January 2005

It is shown that when the contribution of holes in a p+n junction to the space charge in the n region adjacent to the doping step is considered, the capacitance C as function of applied voltage Va is given by C−2=[2(ND+NA)/qεNDNA](Va+Vx).Here NA and ND are acceptor and donor concentrations and Vx, called the offset voltage, has the classical value of built-in voltage minus 2kT/q for nearly symmetrical junctions, independent of applied voltage. For large doping ratios NA/ND, the offset voltage is nearly independent of built-in voltage but increases nearly logarithmically with applied voltage. For forward bias the present treatment gives capacitance values considerably larger than those resulting from the widely accepted treatment which neglects the charge of holes on the n side.
Domain-Wall Motion in Barium Ferrite Single Crystals
Authors: Asti G. , Colombo M. , Giudici M. , Levialdi A.
Published: January 2005

The 180° domain-wall motion in barium ferrite single crystals has been studied by the pulsed-magnetic-field technique described in a previous article.

The domain-wall velocity has been measured as a function of the internal magnetic field in a range from 50 to several hundred Oe and at temperatures of 80° and 293°K. The rate of increase of the applied magnetic field dHa/dt has no apparent effect if it does not exceed 1.6 kOe/μsec. Reasonable agreement is found between the wall velocities as measured and values foreseen on the basis of the model proposed by Hagedorn and Gyorgy to explain wall mobility in YIG.

An accurate analysis of the dependence of the wall velocity on the magnetic-field intensity suggests the existence of a threshold field Ht, which depends on the value of the damping constant α and defines the point of transition from one motion mechanism to another. We think that Ht may be identified with the critical field H0=2παMs which appears in a solution given by Walker to the domain-wall equations, and that the model proposed by Hagedorn and Gyorgy simply applies to the case H>Ht. This means that, rather than the damping constant α alone, the quantity k=H/2παMs is to be taken as a suitable parameter to distinguish between different motion mechanisms.
Simultaneous Occurrence of and Competition between Stimulated Optical-Scattering Processes in Gases
Authors: Minck R. W. , Hagenlocker E. E. , Rado W. G.
Published: January 2005

Using the gain coefficients for individually stimulated Brillouin and Raman transitions in gases, we have been able to predict the pressure and temperature at which the gain coefficients for various transitions are equal. The competition between simultaneously stimulated optical-scattering processes has been studied in the vicinity of these predicted intersections. Within a limited range of parameters, two processes can be stimulated simultaneously. The experimentally observed gain for the weaker process is affected by the presence of the intense Stokes beam associated with the dominant process in some instances, but not in others. Using idealized models, the enhancement of the gain coefficients due to the presence of additional intense-frequency components and the reduction of gain due to depletion of laser power have been considered, but neither effect yields a consistent explanation of the observed behavior.

The competition between vibrational Raman-vibrational Raman, vibrational Raman-rotational Raman, Raman-Brillouin, and forward-reverse propagating Raman were studied. In all of these experiments, no evidence for enhancement of gain, but several examples of reduction in gain, were observed.
Thermionic Emitters Consisting of BaO–UO2 Dispersed in a Tungsten Matrix
Authors: Gifford Fay E. , Hill Robert F.
Published: January 2005

Thermionic emitters fabricated with various concentrations of BaO and UO2 dispersed in tungsten have been operated at temperatures up to 1400°C. A tentative phase diagram for the BaO–UO2 system has been constructed from microstructure and x-ray analysis. Electron-emission studies, emitter-life tests, and barium-transpiration studies have been conducted on eleven different BaO–UO2 tungsten compositions. The emission studies have indicated current-density capabilities of 10 A/cm2. Work-function measurements at 1100°C on the various emitters tested ranged from 2.03 eV for the high-barium-content samples to 2.56 eV for the low-barium-content samples. The barium transpiration rate of the emitters was evaluated for various barium contents and compositional forms. For a given quantity of barium, the transpiration rate was lower from the BaUO3+UO2 system than from the BaUO3+BaO system. At a temperature of 1200°C one type of BaO–UO2 tungsten material had a transpiration rate of 20 μg/cm2·h.
Cross Section for Light Scattering and the Lorentz-Lorenz Formula
Authors: Macrakis Michael S.
Published: January 2005

An attempt has been made to reformulate the problem of light scattering from fluctuations in order to elucidate three fundamental questions concerning: (a) the connection between microscopic and macroscopic (ensemble average) quantities; (b) single and multiple scattering; (c) the Lorentz-Lorenz formula.
Vacancy Concentration and Precipitation in Quenched Pure Gold and Gold-Silver Alloys
Authors: Fraikor F. J. , Hirth J. P.
Published: January 2005

The equilibrium vacancy concentration of gold single crystals and polycrystalline wires was determined by a dilatometric technique and was found to agree well with the results of Simmons and Balluffi. Similar measurements on gold-silver alloys and pure silver indicated some anomalies which were rationalized in terms of an ordering reaction occurring at about 600°C and in terms of divacancy migration in the silver-rich crystals. Concurrent observations of quenched Au–Ag foils by transmission electron microscopy revealed that the predominant type of vacancy sink was the black-spot defect. The proposed r2 relation between specimen size and vacancy concentration and formation energy was shown not to apply in the present work.
Current Saturation in the Evaporated GaAs Films
Authors: Yamashita A. , Tuzaki T. , Yamada T. , Yamauchi I.
Published: January 2005

Current saturation in evaporated GaAs films was observed. Thin GaAs films were fabricated by means of simultaneous evaporation of the elements of the highest purity onto the metal substrate of the Ta. Electrical characteristics of the films were measured employing the Au electrode evaporated on the GaAs films. The intensity ratio of GaKα/AsKα grows with increase of the Ga temperatures and decreases with increase of the As temperatures. The films in which current saturation was observed are formed approaching the stoichiometric structure, and exhibit n-type conduction. X-ray measurements of the crystallized GaAs films show the (111), (220), and (311) lines. Absorption threshold on the crystallized GaAs films was obtained at about 1.24 eV and approaching the transmission data of bulk GaAs after Sturge. The lowest resistivity measured about 1∼10 Ω·cm. The values of threshold voltage linearly grows with increase of the thickness of the GaAs films. Accordingly, we presumed that phenomena of current saturation in the films could be explained by the two-valley model.
Electrical Resistivity of SmAg, SmCu, and SmAu
Authors: Chao C. C. , Duwez P.
Published: January 2005

The electrical resistivity of equiatomic phases of Sm with Cu, Ag and Au was measured down to 4.2°K. Anomalies were found at 10°K for SmCu and at 42°K for SmAg. The resistivity-temperature curve of SmAu has a maximum at 40°K and a minimum at 53.5°K.
Light Scattering by Oriented Dipoles
Authors: Tewarson Shanti P.
Published: January 2005

Soleillet's theory of light scattering by a random aggregation of dipoles has been extended through Mueller matrix algebra to formulate a matrix for light scattering by an array of oriented dipoles. The proposed matrix reveals certain interesting characteristics of dipolar scattering. Linear relations between the parameters of the Stokes' vectors of incident and scattered beams have been obtained for the case of oriented dipoles. The applicability of the matrix has been indicated in the case of radiations in the horizontal plane from an ungrounded antenna or an array of antennas oriented in the vertical plane, and in polarization studies of light scattering by oriented polymer films and fibers which have completely aligned long-chain molecules.
Thickness Effects of Electron Scattering at Au-Film Surfaces
Authors: Johnson J. A. , Bashara N. M.
Published: January 2005

The electron scattering at the surfaces of an Au film vacuum deposited on Bi2O3 is analyzed as a function of film thickness using the Fuchs-Sondheimer theory modified to allow the determination of the scattering parameters separately at each of the film surfaces. The scattering at the air-Au interface becomes less specular as Au-film thickness increases. In the analysis the assumption is made that the scattering parameter at the Au−Bi2O3 interface is unaffected by variation in Au-film thickness. The justification for this assumption is the strong influence of the Bi2O3 on the growth characteristic of the Au film. It is known that a given Au-film thickness will become continuous when deposited on Bi2O3, whereas a film of that same thickness would be discontinuous deposited on bare glass or quartz.
Fe-Co and Fe-V Alloys for Pressure Calibration in the 130- to 300-kbar Region
Authors: Bundy F. P.
Published: January 2005

Fe-Co and Fe-V alloys, tested in static ultrahigh pressure apparatus, have been found to have resistance jumps resulting from the α to ε transformation, as in pure Fe. The pressure of initiation of the transformation increases with the alloy content; from 131 kbar for pure Fe up to 290 kbar for 20 wt% Co. The V alloys rise much faster: 280 kbar at 6 wt%. The Fe-Co alloys can serve as convenient samples to pressure-calibrate apparatus in the 160 to 300-kbar region. The difference between the pressures of initiation of transformation under static conditions, compared to shock conditions, is zero for pure Fe and progressively greater as the alloy content increases.
Dislocations and Fault Surfaces in Synthetic Quartz
Authors: Lang A. R. , Miuscov V. F.
Published: January 2005

Defects in a rather perfect synthetic quartz crystal have been surveyed by x-ray topography. Etching behavior and stress birefringence were also studied. The crystal, grown from a z-plate seed, contained Na and Al in concentrations of 50 ppm by weight. The crystal had grown in the c direction with low dislocation density (∼ 3000 lines cm−2). The majority of dislocations made about 10° with the c axis, only 15% had Burgers vectors with a c-axis component. Cellular growth had developed as growth in the c direction proceeded. The cell walls were identified with fault surfaces made visible by diffraction contrast. These surfaces were inclined at fairly small angles with [0001] and their intersections with (0001) formed an irregular polygonal network. Dislocations congregated in or near the fault surfaces in the later stages of growth. The fault surfaces outcropped at the grooves between protuberances on the rough external crystal surface of mean orientation (0001). The presence of fault fringes indicates impurity segregation in the cell walls: the fringe contrast could arise from a layer a few microns thick with a lattice parameter a few parts in 105 different from that of surrounding material.
Observations of Sub-Unit-Cell Stacking Elements in Mixed-Layer Structures by Electron Microscopy
Authors: Cook C. F.
Published: January 2005

The ``hexagonal ferrites'' comprise a quasipolytypic series of ferrimagnetic oxides containing Ba, Fe3+, and a divalent metal cation (Me2+). These encompass a family of hexagonal and rhombohedral mixed-layer structures derived by the c-axis stacking of two complex invariant building blocks, mainly ``M'' and ``Y''. The M stacking element is a 5-anion-layer block, 11.6 Å in height with the composition BaFe12O19, and the Y stacking element is a 6-anion-layer block, 14.5 Å high with the composition Ba2Me22+Fe12O22. The largest series, M2Yn(n=0 to 21), involves the stacking of two M blocks and a variable number of Y blocks. Permutation of the M and Y elements allows mixed-layer polytypism within a given stoichiometry, i.e., M to Y ratio. More than twenty (20) mixed-layer structures and their polytypes have been examined by electron microscopy after direct replication of the basal face.

Basal faces which were etched with dilute hydrochloric acid exhibit etch steps of sub-unit-cell heights. The specific M and Y stacking sequence of a mixed-layer structure may be obtained by measuring the step-height ratio, MYx/MYn−x, of two adjacent steps, provided either the shadow angle or the x-ray c-axis dimension is known. In addition it has been found that the c-axis dimension and the specific stacking sequence may be uniquely determined by counting the individual M and Y building blocks which are replicated as separate and distinct etch-planes on a crystal surface that has been process-etched.
p-n Junctions in Compensated Solution-Grown GaP
Authors: Logan R. A. , White H. G. , Trumbore F. A.
Published: January 2005

Two distinct processes are suggested for the formation of p-n junctions in crystal platelets of GaP grown from Ga solution doped with Zn, Te, and O, over wide ranges of composition and growth conditions. In each growth melt, about one half of the p-type crystals contain a shallow n-type surface layer, ∼2 μ in thickness, formed by out-diffusion of Zn after growth. These p-n junctions have relatively high (>10−3) external electroluminescence quantum efficiencies at room temperature. The remaining p-type crystals contain deeper, less efficient junctions, built into the crystals by impurity segregation effects during growth. The efficiencies of p-n junctions degrade with the heat treatment at 600°C used to alloy the Ohmic contacts. The extent of degradation correlates with the dislocation density and is ascribed to precipitation. The precipitates nucleate preferentially in the junction plane and grow with subsequent heat treatment.
Thermoelectric Power of CoO near the Néel Temperature
Authors: Bruck A. , Tannhauser D. S.
Published: January 2005

The Seebeck coefficient of nonstoichiometric CoO was measured in the vicinity of the Néel temperature. A steep decrease in the Seebeck coefficient was found at TN. This decrease, as well as the change in the activation energy of conductivity at TN found previously, can be explained either by a change in the ionization energy of the charge carriers or by a change of mobility activation energy.
Positive Streamer Spark Breakdown at Low Pressures in Air
Authors: Oshige T.
Published: January 2005

No data existed as to the lower pressure limits of streamer breakdown in positive point-to-plane geometry. Using a combination of Lichtenberg figure techniques in the coplanar mode and a two-photomultiplier analysis of the movement of luminous pulses between the electrodes, the streamer mechanism has been observed to 4 Torr in room air; below this pressure, it is too faint to observe. A primary streamer starts from the anode. Its speed of the order of 107 cm/sec varies across the gap, depending on overvoltage and pressure. It is influenced by encounter with photoelectrically initiated avalanches from the cathode and by streamer-tip-cathode fields. On arrival at the cathode, fast space waves of potential gradient travel up the branch tips. Where such waves converge at the junction of the channel branches near the anode, a bright secondary streamer pulse appears. The tips of the midgap event move towards cathode and anode as secondary positive and negative streamers, respectively, at speeds around 106 cm/sec. The luminosity engendered when the streamers are launched initiates a new negative photoelectrically triggered group of electron avalanches that move up the channel at about 106 cm/sec. When this group meets the positive secondary streamer tip, the arc channel is completed. Observations leading to this picture constitute the content of this paper.
A Phenomenological Theory of Dielectric Response
Authors: Tilley Donald E.
Published: January 2005

The phenomenological theory of the electret effect, as developed by Wiseman and Feaster and extended by Perlman and Meunier, is cast into a form which allows a unified treatment of a variety of experiments. Introducing Mikusinski operators, a superposition principle expresses the electric displacement operator as εE+Pb with Pb(t)= ∫ −∞0χ(t−T)E(T)dT,and ε=ε0+χi+χ, where the operator χ characterizes the slow polarization response and the constant χi gives the fast response. Then, the field E within a dielectric of conductivity c is related to the electrode current density J by the operator equation E=Z(J—J̄), where Z=1/(c+sε) determines the impedance operator and the operator J̄={dPb/dt}−εiE(−0) gives the effects of fields applied before t=0. Applications include a derivation of interesting relations discovered by Gross, an evaluation of the accuracy of the quasiequilibrium approximation used by Perlman and Meunier, and the construction of an equivalent circuit.
Temperature Dependence of Photoluminescence in Cadmium-Doped Epitaxial GaAs
Authors: Williams E. W. , Chapman R. A.
Published: January 2005

The relative photoluminescence intensities of band-to-band and band-to-acceptor radiative recombination were measured as a function of temperature. p-Type cadmium-doped epitaxial GaAs was studied. The samples that were used had carrier concentrations in the range of 5×1017 to 3.5×1016/cc as determined from Hall measurements at 300°K. Over the temperature range 40° to 150°K the two emission peaks were sufficiently resolved so that accurate intensity measurements could be made. The temperature dependence of the band-to-acceptor luminescence intensity is in agreement with theoretical estimates of the inverse lifetime for this recombination mechanism. The variation of the diffusion of photoexcited minority carriers as a function of temperature must be considered in order to relate the band-to-band luminescence with the lifetime for the mechanism. Minority carrier diffusion theory analysis suggests that the good agreement obtained between theory and experiment for the band-to-acceptor luminescence occurs because the total lifetime and the diffusion coefficient have similar temperature dependence in the temperature range studied.
Double Magnetic Resonance of Coupled Spins
Authors: Bates Clayton Wilson
Published: January 2005

A perturbation procedure is introduced to solve for the probability amplitudes of a system of coupled spins under the action of two rf magnetic fields; one a large saturating signal, the other a relatively weak one. The power absorbed when the saturating signal connects two states in the system is affected by the presence of the second signal connecting two other states especially if both signals have one state in common. The mixing of these states by the saturating signal can become large enough in some instances that it becomes meaningless to speak in terms of population differences and rate equations for these levels. It is further shown that the effect of the intermediate levels is to cause a shift in the resonance frequency for these levels. For widely spaced levels this ``intermediate'' effect may be neglected, but for closely spaced levels it can become appreciable.

A four-level system is used to illustrate the method. Relaxation effects are neglected.
Dielectric Properties of Films Formed by Vacuum Evaporation of Silicon Monoxide
Authors: Anastasio Thomas A.
Published: January 2005

Dielectric constant and dissipation factor at 1 kHz for films formed by vacuum evaporation of silicon monoxide have been measured as a function of deposition rate and residual oxygen pressure. The dielectric properties are found to depend strongly on the ratio of molecular-impingement rates at the substrate of O2 and SiO. A model based on changes in the film of the concentrations of Si, SiO, and Si2O3 is proposed to explain the dielectric behavior. The model is compared to optical data reported by other workers.
Photo and Thermal Effects in Compensated Zinc-Doped Germanium
Authors: Keyes Robert J.
Published: January 2005

Below 30°K zinc-doped germanium exhibits a number of unusual photo and temperature effects when the lowest zinc-acceptor levels have been filled by electrons from compensatory antimony impurities. These effects include negative photoconductivity, a discontinuity in the temperature dependence of the sample conductivity, as well as the storage of free electrons produced by intrinsic photoexcitation. Hole trapping by the Zn atoms which are singly or doubly ionized is the prime source of these effects. A simple theory is presented which qualitatively explains all of the observed effects and quantitatively fits the data in those areas that are accessible to rigorous measurement.
Evidence for Damage Regions in Si, GaAs, and InSb Semiconductors Bombarded with High-Energy Neutrons
Authors: Bertolotti M. , Papa T. , Sette D. , Vitali G.
Published: January 2005

Evidence is reported for the existence of damage regions in Si, GaAs, and InSb irradiated with mono-energetic 14-MeV neutrons. The regions were revealed by using a chemical etch and observing carbon replicas of the surface with an electron microscope.
Steady-State Theory of an Intermediate-Pressure Discharge Column in a Magnetic Field
Authors: Ewald H. N. , Crawford F. W. , Self S. A.
Published: January 2005

A steady-state theory of a discharge column in a magnetic field is presented which covers the intermediate pressure range where the ion mean free path is neither much greater than, nor much less than, the discharge radius. With increasing pressure and magnetic field, its predictions tend to those obtainable from ambipolar diffusion theory. With decreasing pressure they approximate those of low-pressure discharge theory based on the use of the third-moment equation for the ions. The analysis in this paper is based on continuity and momentum-transfer equations for the electrons and ions, but in contrast to linear ambipolar diffusion theory, the nonlinear ion inertia term is retained. In the plasma approximation, retention of this term gives rise to a plasma-sheath boundary, where the density is nonzero and the potential finite, located where the ambipolar drift velocity reaches the isothermal sound speed [k(Te+Ti)/mi]1/2. Numerical solutions are presented for the profiles of density, velocity, and potential, for planar and cylindrical discharges. These indicate that potential inversion can occur, and that under such conditions the potential rises to a maximum and then decreases towards the plasma-sheath boundary.
Lattice-Dynamical Theory of Switching in Barium Titanate Single Crystals
Authors: Nettleton R. E.
Published: January 2005

A lattice-dynamical approach to calculation of the switching probability is developed for use in connection with the Miller-Weinreich model of 180° domain-wall motion in barium titanate single crystals. According to the new approach, the nuclei of permanently reversed polarization, which appear on the domain-wall surface in the presence of a field, are produced by a superposition of optic modes. The probability that this superposition will attain the amplitude required to switch a nucleus can be calculated as the probability for the outcome of a random walk. This probability is a function of the optical frequency and of the number of modes which contribute to switching. From a previous renormalization of the Hamiltonian which describes the lowest transverse optic mode, the field and thickness dependence of the parameters which govern switching can be determined. In this way it is predicted that (1) the product of field and activation energy will increase with the field; and (2) the thickness dependence of the switching activation energy, which is primarily of lattice-dynamical origin, should exceed the corresponding thickness dependence of the electric susceptibility measured on the same crystal. The role of the surface layer is assumed, following Janovec, to lie in the production of backswitched microdomains behind the advancing domain wall. This backswitching can produce electrostatic fields which retard the wall in the same way as depolarization fields which earlier theories have attributed to charges deposited on the inner surface of an unswitched layer. This picture of retardation permits us to separate the mechanism which slows the wall from that which accounts for the thickness dependence of switching and thus to avoid contradictions which have arisen in attempts to explain the latter effect by depolarization fields.
X-Ray K Absorption Edges of Alloys. II. Nickel-Cobalt and Nickel-Iron Solid Solutions
Authors: Donahue Raymond J. , Azároff Leonid V.
Published: January 2005

Changes taking place in the fine structure of the cobalt K edge in Ni-Co solid solutions indicate a decline in the 3d-4s hole density at cobalt atom sites. Changes in the Ni K edge in the same alloys suggest that the hole density at nickel atoms increases, thus supporting the rigid-band model for these alloys.

Significant changes in the Ni K edges of fcc (gamma) Ni-Fe solid solutions suggest that the rigid-band model may be valid for these alloys also. It does not appear to be applicable, however, to bcc (alpha) solid solutions. In both alloy types, the fine structure at the Fe K edge remained unchanged. Good agreement was obtained with magnetic measurements on bcc Ni-Fe alloys.
Breakdown Conduction in Al-SiO-Al Capacitors
Authors: Budenstein Paul P. , Hayes Paul J.
Published: January 2005

Destructive breakdown has been studied in Al-SiO-Al capacitors using transmission electron microscopy and electron diffraction, while the capacitors were subjected to controlled electrical stresses. Extensive electrical measurements were made outside the electron microscope on other capacitors. The purpose is to describe destructive breakdown and to relate it to prebreakdown conduction, conditions of fabrication, and capacitor structure.

It is found that breakdowns originate at inhomogeneities in the dielectric which appear in electron micrographs as irregularly shaped dark spots about 0.5 μ in diameter. The structure of these dark spots has not been determined. Breakdowns are not concentrated at pinholes, dust spots, or fissures. Breakdown is accompanied by the growth of crystalline silicon. Electrical measurements with a given capacitor reveal two well-defined polarity-sensitive threshold voltages, one for the onset of breakdown and one for the cessation of breakdown. Both are virtually independent of temperature from 80° to 380°K. The voltage threshold for the onset of breakdown varies approximately as w1/2, where w is the dielectric thickness, while the voltage threshold for the cessation of breakdown is found to be independent of dielectric thickness. The diameter of a typical breakdown is 10 to 100 μ. The conductivity of the breakdown site at the onset of breakdown changes by a factor of about 1010 in a time less than 0.1 μsec. Duration of a breakdown is usually about 1 μsec.

A breakdown mechanism is proposed that is based upon an electrochemical solid reaction in the presence of the breakdown electric field: Si−O−Si+(breakdown electric field)→Si−Si++O+e,where the term Si−Si+ means the two silicon atoms are in crystalline form and one is singly ionized. A description of the breakdown process is given using this reaction.
Electron-Bombardment Desorption of Carbon Monoxide Adsorbed on Tungsten
Authors: Sandstrom D. R. , Leck J. H. , Donaldson E. E.
Published: January 2005

The ion current produced by electron bombardment of the (211) crystal face of a W ribbon is shown to be predominantly O16+. The only impurity detected, H+, was never more than 4% of the total current even when the ribbon operated in hydrogen with a carbon monoxide impurity as low as 1%.
Flash Evaporation and Thin Films of Cuprous Sulfide, Selenide, and Telluride
Authors: Ellis S. G.
Published: January 2005

Films of Cu1.8S have been made by flash evaporation. They have a resistivity of 6.2×10−4Ω·cm and an absorption coefficient to 1.5 eV radiation of 1.13×103 cm−1. The corresponding quantities for Cu1.8Se are: 1.6×10−4Ω·cm, and 1.18×103 cm−1. The resistivity of Cu1.8Te films increases with time.

It is found that if during flash evaporation the ratio of partial pressures of Cu and Se at the substrate fluctuates then the film does not have the composition of the charge.

Cu1.8S has potential applications for producing transparent conducting coatings on substrates which cannot be heated above room temperature.
Enhanced X-Ray Diffraction from Substrate Crystals Containing Discontinuous Surface Films
Authors: Blech Ilan A. , Meieran Eugene S.
Published: January 2005

The lattice distortions in single-crystal Si substrates due to stressed surface films were calculated by linear elastic theory. It is shown that the strains are localized directly underneath discontinuities in the films, and these regions are responsible for the enhanced diffracted intensity experimentally observed in x-ray topographs of the substrate. A simplified theory is presented which is used to semiquantitatively describe the relationship between film stress and thickness, and enhanced diffracted intensity.
Evidence for Domain-Wall Compressibility in Permalloy Wire
Authors: Schulz-DuBois E. O.
Published: January 2005

This paper describes dynamic magnetization experiments in hard-drawn niobium-silver Permalloy wire of the type used in domain-wall shift registers. In particular, it reports evidence for the compression, under the influence of an applied bucking field, of the transition region separating two domains of antiparallel longitudinal magnetization. In the absence of external field, the transition region is characterized by a domain wall roughly conical in shape, with a minimum length of about 1 cm for wire of 0.005-cm diameter. The length of the transition region is inversely proportional to the longitudinal derivative of flux, which may also be referred to as magnetic pseudocharge. The latter quantity was measured by a bifilar pickup coil wound around the wire, and subsequent electronic integration. Dynamic experiments employing ac bucking fields with or without an additional homogeneous field result in hysteresis loops of particularly simple and predictable types. Identifiable individual processes within the cycle are nucleation, compression and expansion of the transition region, and wall motion. A compression of the longitudinal dimension of the domain wall by a factor four is observed with a bucking field of 17 Oe. The curved portion of the loops is, with good accuracy, described by a parabolic dependence. This shape is expected from magnetostatic arguments which predict a domain-wall length proportional to (HB±HW)−½, where HB is the applied bucking field and HW is the wall-motion threshold.
Cathode- and Anode-Induced Electrical Breakdown in Vacuum
Authors: Utsumi T.
Published: January 2005

The problems considered are whether the breakdown that occurs between two parallel-plane electrodes in a vacuum is an anode-induced or cathode-induced breakdown and what conditions determine which type of breakdown is dominant. The critical anode power density for an anode-induced breakdown and the critical cathode current density for a cathode-induced breakdown were measured and the experimental results were compared with predictions from theory of heat conduction. An analysis of these experimental results led to a criterion for determining the type of breakdown that predominates as a function of separation between electrodes and of the thermal and electrical conductivities of the material of the electrodes. It was shown that there were four distinct regions of separation: two anode-induced regions, one cathode-induced region, and one transition region of both types.
Slow-Wave Parametric Pumping of the Electrostatic Wave in a Plasma
Authors: Paik S. F.
Published: January 2005

The electrostatic wave in a plasma may be amplified parametrically by applying a pump power at microwave frequencies. The theory of the parametric interaction between the electrostatic wave and a guided electromagnetic wave is presented, and the gain parameter is derived in terms of the pump power. The pump power required to observe the effect of the pumping at microwave frequencies is calculated to be orders of magnitude less than the optical power required to produce the Raman effect in plasmas.
Localized Vibrational Modes of Lithium in Lithium-Diffused p-Type GaAs
Authors: Lorimor O. G. , Spitzer W. G.
Published: January 2005

Samples of Mn-, Cd-, and Zn-doped GaAs were diffused to near compensation with Li. A number of Li-localized vibrational-mode absorption peaks have been observed. Three bands are present in Mn- and Cd-doped material. A simple model is proposed which is based upon interstitial Li paired with Mn or Cd, where the ion pairs are oriented along a 〈100〉 direction. In Zn-doped material four Li bands associated with Li-Zn complexes are observed. In this case the authors are unable to present a model consistent with existing experimental data.
Evaporated Metallic Contacts to Conducting Strontium Titanate Single Crystals
Authors: Carnes James E. , Goodman Alvin M.
Published: January 2005

Evaporated metallic contacts (area = 0.1 mm2) have been made to etched (100) surfaces of conducting strontium titanate single crystals. The metals employed were Mg, In, Au, Pd, and Pt. The electrical properties of these contacts were studied by measurements of: (1) differential capacitance as a function of bias voltage, (2) spectral variation of photoemission from the metal into the strontium titanate, and (3) current-voltage characteristics. The measurements have been analyzed to yield effective values of Δφ (work function of the metal with respect to the strontium titanate conduction band at the contact) with the following results: (1) the electrical properties of the contacts are different for the different metals, (2) the low-work-function metals (Mg and In) form low-resistance contacts, (3) the high-work-function metals (Au, Pd, and Pt) form blocking contacts, and (4) none of the blocking contacts can be characterized by a single value of Δφ; i.e., each blocking contact behaves as if it consists of patches of different Δφ.
LSA Oscillator-Diode Theory
Authors: Copeland John A.
Published: January 2005

The efficiency, negative resistance, and conditions for space-charge control relevant to operation of a bulk semiconductor diode in the limited space-charge accumulation (LSA) mode of oscillation are discussed. Numerical results for n-GaAs indicate a maximum dc to rf-conversion efficiency of 18.5% for sine-wave excitation. The usable range of doping to frequency for n-GaAs is found to be 2×104 to 2×105 sec/cm3 with an optimum value of about 6×104 sec/cm3. Although a reduction in efficiency at frequencies above 100 GHz is expected due to the finite response time of GaAs, worthwhile efficiency may be obtained at several hundred GHz.
A Method for Evaluating the Stability of Composite Superconductors
Authors: Purcell J. R. , Brooks J. M.
Published: January 2005

Data are presented for tests which were conducted on Nb-33% Zr superconducting cable. The method of testing is described and provides a reliable method for predicting the maximum stable current and field which can be expected for a magnet wound from the cable.
Derivation and Experimental Verification of an Equation for Exposure-Dose Rate due to X-Ray Continua
Authors: Ray Satyabrata , Dodd C. G. , Muchow G. M. , Neilson G. F. , Kaup D. J.
Published: January 2005

An equation has been derived for the exposure-dose rate due to radiation emitted by x-ray tubes and transmitted through media which absorb all characteristic radiation. The parameters involved in this expression are the operating voltage and current of the tube and the linear-absorption coefficient and thickness of the absorbing media. Experimental verification of the equation shows that exposure-dose rates can be calculated within ±6% on a relative basis.
Surface Vacancies on Metal Crystals
Authors: Schwoebel Richard L.
Published: January 2005

It is demonstrated that equilibrium concentrations of surface vacancies on the principal planes of metal single crystals may exceed the concentrations of atoms in adsorbed positions. Surface vacancy concentrations on some of the higher index planes of gold are calculated to be of the order of 10−2 or more at 1000°K. The interactions of mobile surface vacancies with steps are considered and contrasted with those of atoms diffusing on the surface. The possible influence of surface point defects on transport and growth mechanisms are discussed assuming that vacancy generation occurs mainly at kink sites on the free surface.
Comment on ``Positron Focusing in an Accelerating Field''
Authors: Nickle H. H.
Published: January 2005

It is pointed out that the idealized problem of positron focusing considered by G. W. Hong has a simple analytical solution, but the properties of the exact solution do not agree at all with the approximate solution obtained by Hong's iterative procedure. In addition, the idealized problem considered by Hong completely ignores two factors which may play decisive roles in any practical focusing scheme.
Transient Interference Studies of Emission from a Pulsed Ruby Laser
Authors: Berkley David A. , Wolga George J.
Published: January 2005

A transient interference experiment has been performed using the radiation from a normally spiking, pulsed ruby-laser oscillator. In the experiment the laser output at time t is made to interfere with emission corresponding to an earlier time, t-τ, by means of an optical delay inserted into a two-pinhole Young's interferometer. A light-pipe photomultiplier oscilloscope system permits photographic recording of the interference fringes during a single spike of the laser emission, with a time resolution of less than 15 nsec. From the data obtained both the fringe visibility and the relative pattern phase of the interference pattern may be evaluated. Data are presented for both visibility and pattern phase for several delay times. The principal observation is that during a single laser spike the frequency increases with time. An analysis of the experiment and of possible causes for frequency variation of the laser with time results in the hypothesis that there is lattice strain in the ruby associated with the optical pumping to the excited state from which laser emission occurs. Linearity is assumed between strain and the number of excited ions. This permits a calculation to be made of the frequency change resulting from the strain and very reasonable agreement is obtained upon comparison with experiment. The visibility data are discussed but quantitative conclusions cannot be drawn.
Characterization of the Fe-FexSb Eutectic System with Respect to Structure and Ferromagnetic Properties
Authors: Galasso F. S. , Douglas F. C. , Darby W. , Batt J. A.
Published: January 2005

Unidirectional solidification of the Fe-FexSb eutectic resulted in the formation of aligned twelve-sided iron rods in an FexSb matrix. The iron rods grew in the [111] direction and the FexSb matrix in the [001] direction. Half of the interfaces were parallel to the {110}Fe and {211}FexSb and the others were parallel to {211}Fe and {100}FexSb. Magnetic measurements on the controlled specimens showed that they had a much larger coercive force than bulk iron. The opening of the hysteresis loop is attributed to the small size and large aspect ratio of the iron rods.
Frequency Dependence of Dislocation Damping in Single-Crystal Copper
Authors: Heiple Clinton R. , Birnbaum H. K.
Published: January 2005

The frequency dependence of the amplitude-independent and amplitude-dependent dislocation damping was measured on the same high-purity copper single crystal in both the kilocycle and megacycle frequency ranges. The dislocation contribution to the elastic modulus was also measured in the kilocycle range. The results are discussed in terms of a theoretical calculation which treats the dislocation as a pinned elastic string which experiences a viscous drag proportional to its velocity. The kilocycle dislocation damping exhibited an approximately linear frequency dependence; however, a somewhat better fit to the data can be made with a relation of the form Δ=αω−1+βω. It is proposed that the term αω−1 is a contribution from the high-frequency side of a low-frequency dislocation damping maximum. The dislocation damping in the megacycle range was proportional to ω−1. The kilocycle and megacycle data are consistent with a curve of the form Δ=K[ωτ/(1+ω2τ2)] (except at the lower kilocycle frequencies measured), as predicted by the string model. The maximum is at 1.7 Mc/sec. Based on the agreement of the data with the theoretical model, the dislocation density is calculated to be 1.1×106 cm−2 and the average loop length to be 5.7×10−4 cm, assuming an exponential loop-length distribution. The modulus defect was found to be independent of frequency, except for a possible small rise with decreasing frequency below 30 kc/sec.

The amplitude-dependent internal friction of the specimen in the kilocycle range was found to be frequency dependent in the annealed state and to be frequency independent in the irradiated state. The strain amplitude above which the specimen exhibited amplitude dependence was observed to increase with frequency in the kilocycle range.
Crystal Growth and Defect Structure of Zinc Sulfide and Zinc Selenide Platelets
Authors: Fitzgerald A. G. , Mannami M. , Pogson E. H. , Yoffe A. D.
Published: January 2005

An electron-microscope study has been made of the growth of zinc sulfide and zinc selenide platelets from the vapor phase. One of the typical growth habits, corresponding to a thin plate parallel to (12̄10), was studied in detail. Many of the crystals are in the form of flat platelets, sawtoothed along one edge. The distribution of stacking faults in these crystals has several characteristic features related to the shape of the crystal. For example: (i) A stacking fault, near and parallel to the straight edge of the crystal, divides the crystal in two parts; one is almost defect-free and the other contains many defects. (ii) There is a decrease in the number of stacking faults on moving away from the dividing stacking fault. (iii) The grooves on the ragged edge of the crystal are terminated by stacking faults. (iv) The stacking faults near the ragged edge are distributed roughly on lines perpendicular to the straight edge. These lines are directed to the grooves of the ragged edge. A possible model for the growth process of the platelets is discussed on the basis of these observations: Prior to the platelet formation, a whisker of wurtzite structure grows by an axial dislocation mechanism. The whisker broadens into a platelet by the two-dimensional nucleation of the atomic steps on the surfaces. The process of the formation of the atomic steps and the shape of the crystal are discussed from the observed distribution of the stacking faults.
Interactions between a Solute Atom and an Array of Edge Dislocations
Authors: Cosgrove G. J. , Liu H. W.
Published: January 2005

Elastic and electrostatic interactions between an impurity atom and an edge-dislocation array have been investigated. The elastic interaction is calculated from the volume difference of the solute atom and the stress field of an edge-dislocation array piled up at a barrier. The range of the elastic interaction of an array of dislocations with an impurity extends much further than that with an isolated dislocation.

Classical electrostatic theory has been employed to study the interaction between a charged impurity atom and an array of edge dislocations. In the calculation, a linear electric dipole is assumed to be associated with each edge dislocation. The electrostatic-interaction potential of a dislocation array with an impurity atom is taken as the sum of the potentials of all the dislocations in the array. An expression for the electrostatic-interaction potential has been derived and numerical results are calculated and compared with the interaction between a charged impurity atom and an isolated dislocation as given by Cottrell, Hunter, and Nabarro. The electrostatic-interaction potential of an array is found to be higher than the interaction with an individual dislocation only when the leading dislocations are very close together. This is expected since the range of the electrostatic field of a dipole is very short. Both electrostatic and elastic interactions are dependent upon the net applied stress on the slip plane.
High-Frequency Conductivity of a Partially Ionized Plasma in the Long-Wavelength Limit
Authors: Joyce Glenn R. , Willett Joseph E.
Published: January 2005

The high-frequency conductivity of a partially ionized, homogeneous plasma near equilibrium is calculated. Interactions between charged particles are treated by BBGKY methods, and interactions between neutral and charged particles are treated by a Boltzmann collision integral. Solution of the second hierarchy equation is facilitated by a modification of an operator technique developed by Dupree. Numerical results in the limit of infinite ion mass are studied in terms of an effective charged-particle-charged-particle collision frequency which is found to depend on the neutral-particle density and the external-field frequency.