bluuebunny/crossref_metadata_2025 huggingface dataset:
Luminous Front Thickness in Electric Shock Tubes
Authors: Barach J. P. , Sivinski J. A.
Published: April 2005

Five electric shock tube arrangements have been studied by means of photomultiplier signals. The risetime of the luminous front as it passes the detector station is converted to a thickness by means of the measured front speed. These thicknesses are correlated with initial conditions of pressure from 0.15 to 5.0 Torr of argon, and input power from 0.8 to 262×106 W, for tubes with luminous front speeds from 3 to 30 mm/μ sec. For each tube the front thickness increases with input energy and, in general, the thickness of the luminous transition zone is proportional to the peak current. Identification of the luminous front is with the ``hairpin'' driving current, rather than with a shock wave initiated by it. A maximum current density picture of this driving current is suggested by the data.
Square-Loop Properties of Materials in the System NiFe2O4–Fe3O4–MnFe2O4
Authors: Im Ho Bin , Wickham D. G.
Published: April 2005

Toroids composed of polycrystalline materials of a number of compositions in the system NiFe2O4–Fe3O4–MnFe2O4 exhibit rectangular magnetic hysteresis loops. The squareness ratios, switching coefficients, and coercivities, and their temperature coefficients demonstrate the usefulness of these materials as the storage elements in coincident-current computer memories. The square hysteresis loops in this system can be explained with the aid of existing knowledge of the magnetocrystalline and stress anisotropies.
A Study of Standing Spin Waves in Thin Permalloy Films at Radio and Ultrahigh Frequencies
Authors: Hasty Turner E.
Published: April 2005

A study of standing spin waves in thin Permalloy films in the frequency range 50–4200 Mc/sec was conducted with a dc magnetic field applied perpendicular to the film surface. The purpose of the experiment was to study the behavior of the spin-wave absorption lines at fields just above saturation and to investigate the possibility of exciting standing spin waves at fields below saturation. It proved possible to excite one spin-wave line when the field was less than that required for saturation. Comparison of the field separating this line from the main absorption line with the separation of the spin-wave lines when the dc field is above saturation indicates that this line is the N=1 line. Further study based on the concept of dynamic pinning demonstrates that the surface spins are not pinned in this unsaturated region and that this N=1 line is excited only by an inhomogeneous field. An expression for the rf susceptibility and the general boundary conditions are derived in the Appendix.
Superconducting-to-Normally Conducting Transitions in Strip Transmission Line Structures
Authors: Sass A. R. , Friedlaender F. J.
Published: April 2005

A theoretical and experimental investigation of superconducting-to-normally conducting transitions in strip transmission line structures is presented. The theoretical analysis is based on a macroscopic model, which is the transmission line analog of the Pippard model. It is assumed that during the transition a superconducting-normally conducting (S-N) interface propagates along the transmission line structure. This situation is treated theoretically as a moving boundary value problem. The S-N interface propagation velocity is determined explicitly in terms of the current that induces the transition, the operating temperature, and the superconductive penetration depth. Experimental results indicate that the model is useful for predicting the transition time of a strip transmission line structure.
Exo-Emission from Abraded and Etched Aluminum
Authors: Mueller R. K. , Pontinen Ken
Published: April 2005

Successive surface layers were removed from freshly abraded and from abraded and aged Al by chemical etching and the exo-emission of the new surface observed in a Geiger-Mueller counter. Aging affected emission properties only in extremely thin surface layers. A one-second etch in 1% HF was sufficient to recover 90% of original activity. Decay rates of original and recovered activity and distribution of potentially active centers in depth was not affected significantly by aging.
Electrical Measurements on Photographic Grains Containing Cadmium
Authors: Brady L. E. , Hamilton J. F.
Published: April 2005

Ionic conductance and electron lifetime measurements have been made on emulsion grains containing cadmium. The reduction in the concentration of interstitial silver ions because of the divalent cationic impurity, decreases the ionic conductivity, correspondingly increases the electron lifetimes in the grains, and introduces a high-intensity, reciprocity-law failure in the emulsion. These results confirm the conclusion that silver ions are the dominant carriers of ionic current and that these same silver ions play a major role in the initial trapping of photoelectrons during latent-image formation. Moreover, they strongly suggest that the silver ions responsible for ionic conductance in grains with no impurity additions are interstitials generated at kink sites on the grain surface and moving in a space-change layer within the grains.
Stacking Fault Nucleation in Epitaxial Silicon on Variously Oriented Silicon Substrates
Authors: Mendelson S.
Published: April 2005

Epitaxial growth of silicon is studied for seven low-index orientations of the silicon substrate. Stacking fault traces are observed on all growths in both the single line and polygonal forms, the latter being dominant in the better growths. For each orientation the largest uniform size stacking fault polyhedra nucleate on the substrate surface and have traces on the film surface with dimensions directly related to the film thickness through a geometric factor. This factor is computed by taking the bounds of the faults (which lie in {111} planes) as 〈110〉 directions.

Direct observations are presented to show that stacking faults form at slip lines, at microscratches produced in the polishing procedure, at particles on the substrate surface, at regions of localized impurity segregation, at surface oxides, and at cleaning stains. Most of the faults can be removed by annealing in hydrogen but not in argon. Among mechanically polished substrates, {111} substrates have the highest stacking fault density. No orientation effect is observed for growths on chemically polished substrates. The effects are consistent with nucleation by small incorrectly deposited two-dimensional layers and by the presence of a foreign substance (probably an oxide) on the substrate surface; the model attributing stacking fault nuclei to collapsed vacancy disks is highly unlikely.
Polymer Deformation. VI. Twinning and Phase Transformation of Polyethylene Single Crystals as a Function of Stretching Direction
Authors: Kiho H. , Peterlin A. , Geil P. H.
Published: April 2005

The deformation occurring during the drawing of polyethylene single crystals consisting only of {110} fold domains was studied by means of electron diffraction and bright-field and dark-field electron microscopy. Samples of several types of polyethylene crystals were used; all crystals studied being drawn 25% on a Mylar substrate. This paper is particularly concerned with the relationship between the draw direction and the crystal axes as it affects the type of deformation. Four different types of deformation, involving different combinations of twinning and phase changes, can be distinguished as follows: (1) When the draw direction is near the b axis, a phase transformation from orthorhombic to monoclinic occurs such that (21̄0)Mo corresponds to (200)Or. (2) When the draw direction lies at an angle between b and 〈110〉, i.e., is nearly perpendicular to a growth face, the phase transformations described here under 1 and 3 both occur. (3) When the draw direction is nearly parallel to 〈110〉, a phase transformation to a monoclinic cell occurs such that (200)Mo corresponds to (200)Or. (4) When the draw direction is near the a axis {110}Or twinning is the primary result. It was concluded that the shear direction for the (110)Or twinning is [11̄0] and that the phase transformation occurs in bands parallel to a, these bands corresponding to striations previously seen in bright- and dark-field micrographs of similarly deformed crystals. The possibility of twinning in the monoclinic phase and the necessity to consider slip parallel to c and molecular tilting is also pointed out.
Diffusion of Xenon in Ceramic Oxides
Authors: Morrison David L. , Elleman Thomas S. , Sunderman Duane N.
Published: April 2005

Postirradiation measurements were made at 700° to 1500°C of the release of 133Xe recoiled into single-crystal α-Al2O3, BeO, MgO, and ZrO2 crystals during neutron irradiation in contact with UO2 powder. The release pattern from most of the specimens was identical: a high rate of loss of 133Xe for several minutes followed by a slower release for which the cumulative fractional release was linear with the square root of the heating time. Diffusion coefficients for 133Xe have been calculated from the slope of the release curve following the initial release. The magnitudes of the diffusion coefficients above 1100°C for α-Al2O3, BeO, and MgO were nearly the same whereas the diffusion coefficients in ZrO2 were ten to a hundred times larger. The activation energy for 133Xe release from α-Al2O3 above 1100°C was 64 kcal/g-mole. The xenon release behavior has been compared to anion diffusion in these oxides.
Strength Reduction and Length Changes in Porous Glass Caused by Water Vapor Adsorption
Authors: Hiller K. H.
Published: April 2005

The reduction in strength of porous Vycor glass caused by adsorption of water vapor has been related to the lowering of the surface free energy, which has been obtained from measurements of dimensional changes. Deviations from this simple relationship have been explained by capillary condensation, which causes a negative pressure under the concave menisci of completely filled pores. It has been shown that the Griffith equation accounts quantitatively for the observed weakening effect if the negative pressure under the menisci is taken into account. The data permit an estimate of γ0=700∓100 erg/cm2 for the surface free energy of the Vycor glass in a vacuum. At complete saturation with water vapor the surface free energy is reduced to ∼200 erg/cm2. It is shown that adsorbates that are not freely mobile on the surface do not cause expansion of the porous glass, although they do reduce the strength. The significance of this result is discussed.
Use of the Interaction of Thermal and Ultrasonic Waves to Study Radiation-Induced Defects in Quartz
Authors: Fitzgerald Thomas M. , Chick Bruce B. , Truell Rohn
Published: April 2005

Evidence is presented showing that the interaction of high-frequency stress waves with lattice vibration waves provides a means of studying crystal perfection. This discussion is concerned specifically with quartz single crystals, but the method has been found to apply to other materials as well.
Impurity States in Semiconducting Masers
Authors: Zeiger H. J.
Published: April 2005

A formalism is developed for computing negative conductivities for inverted populations involving impurity states in semiconductors. General expressions are obtained for three classes of systems: class (1), transitions between states belonging to the same band edge; class (2), direct transitions between states belonging to two different band edges; and class (3), indirect transitions between states belonging to two different band edges. The expressions for negative conductivities are simplified by using the effective mass approximation. The results are then applied to an example of each of the three classes of processes. Class (2) is represented by a model of the GaAs diode laser. It is concluded for this model that at low temperatures, with an acceptor concentration Na∼1018/cc, and an effective acceptor radius of a∼20 Å, population inversion of donor states relative to acceptor states yields a greater negative conductivity than inversion of donor states relative to the valence band. A brief discussion is presented of the threshold conditions for diode lasers.
Size-Dependent Spontaneous Energy Loss in Lasers due to Self-Stimulated Emission
Authors: Waite Tom
Published: April 2005

Laser amplifiers when pumped to a significant degree of population inversion undergo decay via (1) natural spontaneous emission of radiation from individual excited atoms, and (2) a size-dependent decay due to self-amplification of the spontaneously emitted radiation which passes through a large fraction of the amplifier length before escaping. This latter effect has a definite size threshold near which the decay rate changes several orders of magnitude. The decay rate is roughly independent of size except near the threshold.
Ion Distributions in a Pulsed Townsend Discharge
Authors: Edelson D. , Morrison J. A. , McAfee K. B.
Published: April 2005

The equations for the pulsed Townsend discharge involving two ions interacting through the γ process have been solved for the ion densities as a function of time and position. The same mathematical approach yields equations for the single ion case, with or without diffusion, which are valid for all time. Negative ions are a special case in which γ=0. Plots are presented of the rate of ion arrival at the electrode and of ion current, both of which are experimentally accessible. The temporal increase of ion flux in the neighborhood of Townsend's breakdown condition is shown.
Ion Optics of Fields with Rotational Symmetry and Circular Main Orbit
Authors: Boerboom A. J. H.
Published: April 2005

Part I. First-order theory of fields with an axis and a plane of symmetry. By using a symmetry property of the ion orbits in magnetic or electric fields with rotational symmetry, the ion optics inside these fields can be simply deduced. The physical meaning of the various terms in the expressions for the ion orbits is clarified. First-order imaging properties are derived.

Part II. First-order theory for the general case. The calculations on the ion optics of fields with an axis and a plane of symmetry are generalized by omitting the requirement of the symmetry plane. The trajectories in the field are calculated up to the second order. The general equation of the ion path is given by r−R=Σ akl cos[k(αw+[open phi])+l(γw+ψ)]z=Σ ckl cos[k(αw+[open phi])+l(γw+ψ)].The first-order imaging properties are discussed.

Part III. Second-order theory of configurations of consecutive fields and the principle of object aberrations. The method is extended to calculate the ion paths up to the second order in instruments having one or more fields with a plane and an axis of symmetry. By introducing the concept of optical aberrations in the object, the calculation of higher-order aberrations can be simplified to a large extent.
Cataphoresis in Helium-Neon Mixtures
Authors: Schmeltekopf Arthur L.
Published: April 2005

Cataphoresis in He-Ne mixtures was studied spectroscopically and the measurements checked by mass spectroscopy. The pressure was varied from 6 to 90 Torr, the wall temperature from 30° to 500°C, and the current from 10 to 500 mA in quartz tubes of 9.52 and 12.7 mm diameter. The results are compared with the theoretical predictions of Druyvesteyn. Cataphoresis improves with increasing pressure, as predicted, except at pressures above 40 Torr, where the quality of cataphoresis improves only slowly with pressure. The slope of the impurity concentration curve does not change linearly with current from 20–100 mA; it increases with current at very low currents and then becomes independent of current. Because of this discrepancy between theory and experiment, a new empirical equation governing cataphoresis in the region of higher currents is suggested. An increase of temperature markedly decreases the effectiveness of cataphoresis. Increasing the tube diameter and decreasing its length also decreases the effectiveness.

In order to check for a possible ``retrograde'' cataphoresis some measurements were made with He as a minor constituent in Ne. Spectroscopic observations at the cathode indicate an enhanced He concentration there (retrograde cataphoresis); mass spectroscopic analysis shows that the cataphoresis, while slight, is still normal. The extreme excitation conditions at the cathode render spectral intensity interpretations difficult if not misleading there.
Fields Excited by Periodic Beam Currents in a Cavity-Loaded Tube
Authors: Kriegler F. J. , Mills F. E. , Van Bladel J.
Published: April 2005

A method is given for the determination of the electromagnetic fields excited in accelerator cavities by a bunched beam of charged particles passing through the cavities. The electric and magnetic fields within a cavity are determined by solving a ``coupled regions'' problem, where the regions consist of a coaxial cavity and a cylindrical waveguide coupled through a gap. Numerical results are obtained by use of a digital computer for a few configurations representing linear accelerator cavities with drift tubes. The results are presented as a series of normalized curves of pertinent electrical quantities; they should give a clear qualitative picture of the effects of beam loading in linear accelerator cavities. Owing to space limitations, only the fundamental resonance excited by the fundamental beam harmonic was investigated in any detail. The general expressions advanced in this paper can be used to investigate higher-order resonances excited by higher-order beam harmonics.
Viscosity of Partially Ionized Gaseous Cesium
Authors: Robinson C. A. , McNab I. R.
Published: April 2005

The Chapman-Enskog solution of the Boltzmann equation is used to obtain theoretical data for the viscosity of gaseous cesium, including the effects of up to 10% ionization. Results are presented for the viscosity of ionized cesium at pressures of 10−2, 10−3, 10−4, and 10−5 atm in the temperature range 1000°–3500°K, and for unionized cesium over the same range. The viscosity of the 10% ionized gas is found to be about 20% lower than that of unionized cesium under the same conditions.
Saturation Magnetostriction Constants of Gadolinium
Authors: Alstad J. , Legvold S.
Published: April 2005

The saturation magnetostriction constants of single-crystal Gd have been measured from 4.2° to 340°K with a strain gauge technique. A marked change in slope of λA was observed near 220°K; this is the temperature region where the easy direction of magnetization in Gd shifts from the c axis to a cone around the c axis. The constant λC shows a definite maximum near 130°K.
Superposition of Semi-Infinite Solenoids for Calculating Magnetic Fields of Thick Solenoids
Authors: Brown Gerald V. , Flax Lawrence
Published: April 2005

A simple method is given for calculating the magnetic field components in or around any thick finite solenoid by superposition of fields of semi-infinite solenoids with zero inner radius. Equations and graphs are presented for the field components of such semi-infinite solenoids. From these graphs, the fields for solenoids of practical interest can be obtained with errors of less than a few percent. Greater accuracy is possible if numerical tables are used instead of graphs.
Bauschinger Effect in Explosively Loaded Mild Steel
Authors: Jones O. E. , Holland J. R.
Published: April 2005

Experimental results are presented which indicate that the Bauschinger effect is operative in cold-worked SAE 1018 steel for the extreme strain rates (∼106/sec) associated with explosive loading. For approximately 20% prior tensile cold work the compressive dynamic yield stress for a propagation distance of 1.905 cm is about 8.8 kbars as compared to 15.7 kbars for annealed material. For heavily cold-worked metals, which generally exhibit the Bauschinger effect, the results indicate that neglect of the Bauschinger effect under explosive loading conditions can lead to serious errors in the interpretation and extrapolation of experimental results. In the case of metals in annealed or slightly worked states, neglect of the Bauschinger effect in the elastic-plastic model for shock loading and unloading may not be justified.
High-Precision Density Determination of Natural Diamonds
Authors: Mykolajewycz R. , Kalnajs J. , Smakula A.
Published: April 2005

Densities of 35 diamonds have been determined by an improved high-precision flotation method. The density varies from ρ25 = 3.51477−3.51554 g/cm3. The average density of 35 samples is ρ25 = 3.51532 g/cm3. The type I diamonds have higher density and narrower range than type II. Comparison with density computed from the lattice constant shows that type II diamonds contain either vacancies (voids) or impurities of lower atomic weight than carbon, or both, and that type I are contaminated by impurities of higher atomic weight than carbon. Computed nitrogen impurity concentration is in excellent agreement with that found by Kaiser and Bond.
Metastable Resistance States in the Intermediate Region of Superconductors
Authors: Lalevic Bogoljub
Published: April 2005

The present report extends resistance fluctuation studies in the current-induced intermediate state to the intermediate state induced by the application of an external magnetic field. Evidence for the existence of resistance levels is again found for both directions of the superconducting transition. The resistance levels are interpreted in terms of superconducting domains. The number of levels consequently represents the number of superconducting domains present and the difference ΔR between the two successive resistance levels correspond to a spread of the normal phase over a length Δl of a specimen. The transition time between two successive resistance levels is identified as the time of collapse of a domain. The observed transition times for soft superconductors are compared with the theory of propagation of a normal phase boundary and some conclusions on the structure of the intermediate state are presented.
Quantitative Calculation of the Magnetic Ripple of Uniaxial Thin Permalloy Films
Authors: Hoffmann Horst
Published: April 2005

The magnetic ripple of thin films with uniaxial anisotropy is calculated for the field and the magnetization lying along the easy and the hard direction of the uniaxial anisotropy. For small dispersion of the direction of magnetization, the variational principle, applied to all energy terms including the exchange, crystalline anisotropy, uniaxial anisotropy, magnetostriction, magnetostatic, and stray field energies, yields a Bessel's differential equation. Its solutions (cylindrical functions) describe the two-dimensional magnetic ripple of the film. Along the mean direction of the magnetization the fluctuations of the magnetization vector are much greater than perpendicular to it. In the first case these fluctuations are coupled by exchange forces, and in the second case by the stray field. The dispersion of the magnetization depends on the dispersion of the anisotropy, on the magnetic constants of the film, on the thickness of the film, and on the applied field. The theory is able to explain the image of the ripple observed by the electron microscope and to explain the variation of the ripple quantitatively, if the applied field is varied. The estimation of the mean magnetization dispersion agrees with the experimental data of Fuller and Hale. The statements of the theory concerning the mean wavelength λ of the ripple for the mean direction of magnetization along the easy axis λL=2πA12Ku−12(hL+1)−12,and along the hard axis λs=2πA12Ku−12(hs−1)12,are verified by experimental observations. (A is the exchange constant, Ku the uniaxial anisotropy constant, hL = HL/Hk is the reduced field along the easy axis, hs = Hs/Hk is the reduced field along the hard axis.) The calculated domain width, occuring at magnetization reversal along the hard axis, is in good agreement with the experiments of Middelhoek, Feldtkeller, and Smith. The domain splitting is fine at a great dispersion of the anisotropy axis and is less fine at smaller dispersions. The smallest domain width of 80–20 Permalloy films is of the order of 2 μ.

Furthermore the theory gives a new method for the determination of the anisotropy field strength Hk.
A Comparison of the Optical Faraday Rotation and Magnetic Susceptibility of Cerous Phosphate Glass
Authors: Berger S. B. , Rubinstein C. B.
Published: April 2005

The optical Faraday rotation and magnetic susceptibility of cerous phosphate glass of concentration Ce2O3·2.67 P2O5 has been studied as a function of temperature. The Verdet constant exhibits the same temperature dependence as the magnetic susceptibility, consistent with the theory formulated by Van Vleck and Hebb.
Calculation of the Current and Field Distribution and the Magnetization Curves for High-Field, Superconducting Materials in the Form of Sheet
Authors: Riemersma H.
Published: April 2005

This paper determines the field and current distribution in a high-field, superconducting material in sheet form, where the applied magnetic field is parallel to the sheet. The distributions are obtained from a critical state equation and Maxwell's equations, and determined for the two cases of absence or presence of a net transport current in the material.

The field distributions are used to determine the magnetization of the material as a function of applied magnetic field, with the short-sample current-carrying capacity as a parameter. The zero transport current magnetization curves show good agreement in general shape with those experimentally observed. The analysis indicates a reduction in magnetization with increasing transport current.
Role of Displaced Metal in the Sliding of Flat Metal Surfaces
Authors: Cocks M.
Published: April 2005

This paper describes an investigation of the interaction between pairs of flat metal surfaces sliding against one another. The experiments show that the junctions which are formed when the surfaces are first placed in contact do not break when the surfaces begin to slide. The relative motion of sliding is accommodated by plastic deformation of the metal near the contact areas. The plastic shearing takes place in a direction slightly inclined to the surfaces and causes the formation of wedges of displaced metal in much the same manner as was observed in a previous investigation with hemispherical riders sliding against cylindrical drums. With a pair of flat surfaces several wedges are formed simultaneously at various places between the surfaces. The wedges force the surfaces apart, and the separation is often as much as 0.1 to 0.4 mm. The variations in the distance of separation during sliding were measured with a dial indicator. The wedges and the gap between the surfaces were also observed visually with and without the microscope. Metallographic sections cut through the wedges were examined. Differences in the phenomena observed with various metals indicate that with some metals the plastic shearing by which the wedges are generated continues to occur during extended periods of sliding, while with others it occurs mainly during an initial period of sliding, though the wedges once formed remain between the surfaces.
Elastic Constants of Aluminum
Authors: Vallin J. , Mongy M. , Salama K. , Beckman O.
Published: April 2005

The adiabatic elastic constants of aluminum have been measured with an ultrasonic pulse technique at liquid-heluim, liquid-nitrogen, and room temperatures. The values of the elastic constants at 4°K are c11=11.63, c12=6.48, and c44=3.09 in units of 1010 N/m2. The Debye characteristic temperature calculated from these figures is θ=425°K in good agreement with the value obtained from speciffic heat data.

The shear elastic constants ½(c11−c12) and c44 are discussed with reference to the theory given by Leigh.
Lowering the Breakdown Voltage of Silicon p-n Junctions by Stress
Authors: Goetzberger A. , Finch R. H.
Published: April 2005

A reversible reduction of breakdown voltage is observed when mechanical stress is applied to silicon p-n junctions. This effect can best be investigated in junctions exhibiting uniform avalanche breakdown. When uniaxial stress is applied the normalized reduction of breakdown voltage ΔV/VB is proportional to stress, the proportionality constant being of the order of 10−12 dyn−1 cm2. When stress is applied by means of a flat stylus, ΔV/VB is proportional to the load, when a spherical stylus is used, ΔV/VB is proportional to the cube root of load. It can be shown that the relative current change for a given force is to a first approximation independent of diode area and breakdown voltage VB. It is proposed that the effect is caused by reduction of the energy gap.
Polar Properties of ZnS Crystals and the Anomalous Photovoltaic Effect
Authors: Brafman O. , Alexander E. , Fraenkel B. S. , Kalman Z. H. , Steinberger I. T.
Published: April 2005

ZnS platelets grown from the vapor phase, bounded by (2̄11), (011̄), and (111) faces, were used. The crystals showed birefringence bands perpendicular to the [111] axis. X-ray rotation, oscillation, and Laue photographs showed that the bands are due to changes in crystal structure (cubic, hexagonal, and polytypes) and one-dimensional stacking disorder. The polarity of the common [111] axis of the various bands was determined by several techniques. On the (2̄11) faces, heating with H2O2 caused the appearance of triangular etch pits, aligned with bases parallel to the [01̄1] direction and apexes pointing all in the same sense. The (111) face towards which the triangles pointed was attacked faster by the etchant than was the opposite one. The same (111) face became negatively charged if a (2̄11) face was uniformly illuminated by 343 mμ radiation. Furthermore, the same face turned out to be a zinc plane, as revealed by comparing the intensity of two (111) reflections, using wavelengths at both sides of the Zn K-absorption edge. The sense of the crystal growth along the [111] axis was also determined. A correlation was established between the morphology and crystallographic polarity as well. The results show that in spite of the polytypism, twinning, and one-dimensional stacking disorder, the sense of the [111] axis remains constant. Moreover, the one-to-one correspondence between the sign of the photovoltage and the crystallographic polarity restricts the possibilities of interpretations of the anomalous photovoltaic effect observed along the [111] axis in ZnS crystals favoring Neumark's theory [G. F. Neumark, Phys. Rev. 125, 838 (1962)].
Anisotropic Stress Effect on the Excess Current in Tunnel Diodes
Authors: Bernard W. , Rindner W. , Roth H.
Published: April 2005

The existence is reported of large reversible changes in the excess current of germanium, silicon, and gallium arsenide tunnel diodes subjected to highly localized stress. The relationship of this effect to the anisotropic stress effect recently reported by Rindner and Braun in conventional p-n junctions is discussed. It is suggested that both effects may arise from deep-lying electronic states associated with strain-induced lattice defects in the junction region. A consistent interpretation is presented of the tunnel diode excess current in terms of strain-induced intermediate tunneling states, and of the conventional diode current in terms of strain-induced generation-recombination centers.
Temperature Autostabilizing Nonlinear Dielectric Element (TANDEL). II. Explanation of Its Function
Authors: Dvořák V. , Málek Z. , Mastner J. , Janovec V. , Glanc A.
Published: April 2005

A simplified explanation of the automatic temperature stabilization of a nonlinear dielectric element is presented. The explanation is based on energy considerations of the heat produced in consequence of dielectric losses in the element and of heat transferred to the ambient medium. The principle of bringing the element into the autostabilizing state is discussed in detail, as well as the falling out of this state, and the nature of temperature hysteresis of this element is explained. Measurements of complex permittivity at the fundamental frequency and high amplitudes of applied voltage as functions of crystal temperature are given for various values of the heating voltage. From these experimental results the temperature stabilization of the element is calculated for its dependence on variations of ambient temperature and heating voltage; a good agreement was found with the experimental values previously reported. The principle of automatic stabilization of temperature is not limited to the TANDEL produced from a triglycine sulfate single crystal but can be realized with some other materials having a decreasing dependence of ε″ on the temperature.
Electron Effective Mass in ZnSe
Authors: Marple D. T. F.
Published: April 2005

Infrared reflectance and Faraday rotation data were obtained for pure and for highly Al-doped n-type ZnSe crystals. Comparison of these data gave the free-carrier contribution to the dielectric constant and Faraday rotation, which, in turn, yielded the electron effective mass and carrier concentration. The result for the effective mass ratio, m*/m=0.17±0.025, agrees satisfactorily with previous estimates. The Hall scattering constant r was obtained from the optically measured carrier concentration and Hall effect data on the optical samples. The result, r≃1.4, for N≃0.7 Ndeg, is consistent with values found in other II-VI compounds.
Rate of Spherulitic Crystallization with Chain Folds in Polyoxymethylene
Authors: Baer Eric , Carter D. R.
Published: April 2005

Spherulitic growth rate data for polyoxymethylene have been successfully analyzed with the recently proposed nucleation theory by Hoffman and co-workers that assumes a coherent nucleation mechanism. Lamellar step heights, which were calculated as a function of the crystallization temperature, were in good agreement with experimental values obtained by Geil who used small angle x-ray scattering. The surface free energy of the nucleus and the end free energy of the fold surface were calculated to be 10.5 and 26 ergs/cm2, respectively. These reasonable values lend further support to this kinetic analysis.
Low-Energy Electron Diffraction Studies of Gas Adsorption on Platinum (100), (110), and (111) Surfaces
Authors: Tucker Charles W.
Published: April 2005

A low-energy electron diffraction apparatus has been built and used to study the adsorption of simple gases on platinum (100), (110), and (111) faces. Some simple structures formed on various faces are described. Adsorption of oxygen on the (110) face is shown to lead to a rearrangement of the top layer of Pt atoms. On the basis of single scattering it is shown that the adsorbate-substrate combination leads to reflections to be expected from each lattice considered separately. When double scattering is permitted, reflections appear in positions given by the sums and differences of the reciprocal lattice vectors of the separate lattices. This double scattering or multiple reflection is shown to play an important role in low-energy electron diffraction. In particular, two sets of complex diffraction patterns formed by oxygen on the Pt (100) face are shown to have an easy interpretation in terms of multiple reflection. The simple oxygen structures formed are rotated with respect to the Pt substrate but form coincidence lattices with it.
Diffusion-Induced Dislocations in Silicon
Authors: Washburn J. , Thomas G. , Queisser H. J.
Published: April 2005

Plastic deformation produced by phosphorus diffusion into a (001) silicon surface has been studied by transmission electron microscopy. The lattice parameter differences in regions of steep solute concentration gradient are accommodated by a crossed grid of edge dislocations having Burgers vector a/2[110] and a/2[1̄10]. The long edge dislocations end at nodes, which suggests that they are formed by dislocation reactions between pairs of dislocations that can glide into the crystal on {111} planes.
X-Ray Line Broadening in Calcium Fluoride
Authors: Lewis D. , Pearson H.
Published: April 2005

X-ray diffraction profiles of calcium fluoride show broadening which is partly caused by small crystallites and partly by deformation. Annealing eliminates most of the broadening and is accompanied by a parameter change that takes place between room temperature and 250°C and is probably associated with the precipitation of calcium oxide. By cold working the annealed calcium fluoride, it was possible to produce a specimen showing profile integral breadths equal to the original material, but which analysis showed to be caused almost entirely by strain.
Three-Dimensional X-Ray Topographic Studies of Internal Dislocation Sources in Silicon
Authors: Authier A. , Lang A. R.
Published: April 2005

Stereo pairs of x-ray projection topographs have been used to elucidate the configuration of dislocations in a silicon bar lightly deformed at about 900°C. Dislocation reactions and interactions associated with a ten-turn Frank-Read spiral are described.
Diffusion Mechanism of Zn in GaAs and GaP Based on Isoconcentration Diffusion Experiments
Authors: Chang L. L. , Pearson G. L.
Published: April 2005

Precise relationships between the diffusion coefficient D and the zinc concentration C are obtained from isoconcentration diffusion experiments performed at 900°C for zinc in GaAs and at 1000°C for zinc in GaP. It is found that D varies with C from a slightly less than cubic to a somewhat less than square dependence over the concentration range 1018 to 1020 cm−3.

Possible mechanisms that result in concentration-dependent diffusion are discussed. Under the conditions given above, it is concluded that diffusion occurs by an interstitial-substitutional mechanism with the interstitial mode being dominant. The charge states of the various species involved in the diffusion are believed to be: (1) interstitial zinc atoms are doubly ionized donors; (2) substitutional zinc atoms are either neutral or singly ionized acceptors; and (3) gallium vacancies are neutral. A theoretical expression for D versus C, derived under these assumptions, fits the isoconcentration diffusion data over wide ranges of D and C through the use of only one adjustable parameter.
Damaged Layers in Abraded {111} Surfaces of InSb
Authors: Pugh E. N. , Samuels L. E.
Published: April 2005

A metallographic investigation has been made of the nature and depth of the damaged layers in abraded {111} surfaces of InSb. It is shown that the damage consists of cracks which are associated with crack-like dislocation arrays of the type known to exist in abraded germanium and silicon surfaces. However, in InSb the damaged layer also contains glide dislocations and features which are thought to correspond to twins, both of which are absent in the elemental semiconductors. Contrary to previous reports by other workers, the depth of damage, taken as the depth of the deepest cracks, is found to be the same in surfaces terminating with In atoms and in those terminating in Sb atoms. In both cases, the glide dislocations and the twins extend to approximately half the depth of the deepest cracks.
Diffusion of Zn into GaAs under the Presence of Excess Arsenic Vapor
Authors: Rupprecht H. , LeMay C. Z.
Published: April 2005

The concentration dependence of the diffusion coefficient of Zn in GaAs has been measured under excess arsenic vapor pressure at 850°C. The diffusion coefficient varied under these conditions only from 10−11 to about 10−10 cm2/sec as the zinc concentration increased from 1017 to 1020 zinc atoms/cm3. These results are compared with diffusion coefficients found in the absence of excess arsenic by the authors and other workers. The observed difference can be explained by means of an interstitial-substitutional equilibrium. The excess arsenic increases the substitutional component of the diffusion and suppresses the interstitial component. These results are in good agreement with the model first suggested by Longini. The activation energy of the substitutional diffusion coefficient is found to be about 2.8 eV.
Electron Density Measurement of a Plasma Column by Surface Wave Resonances
Authors: Akao Yasuo , Ida Yoshio
Published: April 2005

A method for determining electron density in cylindrical plasma columns uses surface wave resonances which occur when the length of plasma column is an integral multiple of the half-wavelength of the surface wave. One type of resonance is in an axially symmetric mode, the other in a dipolar mode. A theory is given for the relation of resonance frequency to electron plasma frequency. Experiments were carried out with both propagation modes excited simultaneously; the axially symmetric resonances are at much lower frequencies than the electron plasma.
Exo-Electron Emission due to Ultrasonic Irradiation
Authors: Langenecker J. A. M. , Ray D. B.
Published: April 2005

The emission of electrons from metals can be excited through a variety of treatments and stimulated by thermal energy and as shown only recently, by high-intensity ultrasound. Investigations were carried out on disks of 99.999% pure aluminum and aluminum 6061, exposed to acoustic irradiation up to 100 W/cm2 at 20 kc/sec. The peak emission at certain intensity levels of the acoustic field is presented, compared with emission from thermal stimulation, and discussed from the viewpoint of acoustic activation of lattice defects in metal crystals.
Correlation of Emission Processes for Adsorbed Alkali Films on Metal Surfaces
Authors: Rasor Ned S. , Warner Charles
Published: April 2005

An analytical model is described in which the time-averaged charge of adsorbed particles is a function of the energy of transition between atomic and ionic states, as in a thermally ionized gas. This relation is used to determine the dipole moment of the adsorbed layer, including the effect of depolarization by adjacent charges. An expression is obtained which relates the emission properties to the temperature, degree of surface coverage, and basic properties of the substrate and adsorbate. Through estimation of the atom adsorption energy, a relationship is obtained which gives a good correlation of most available data for the emission properties of surfaces immersed in cesium vapor.
Experimental Determination of the Drift Velocity of Low-Energy Electrons in Ar, N2, CO2, Several Ar–N2 Mixtures, and Several Ar–CO2 Mixtures
Authors: Levine Norman E. , Uman Martin A.
Published: April 2005

An experimental determination of the drift velocity of low-energy electrons in argon, nitrogen, carbon dioxide, several mixtures of argon and nitrogen, and several mixtures of argon and carbon dioxide used a pulsed ionization chamber with alpha particles as the source of ionization. The experimental data for the single gases serve to verify the experimental technique. The results and a detailed estimation of the possible experimental errors are presented.
X-Ray Measurements of Faulting in α Cu-Ge Alloys
Authors: Vassamillet L. F. , Massalski T. B.
Published: April 2005

The shifts of the (111) and (200) x-ray diffraction lines have been measured by both the centroid and the peak method. From these measurements the stacking fault probability α and the twinning fault probability β can be obtained on powdered samples prepared by filing. These results show a parabolic type of dependence of α with composition, whereas the stacking fault probability α obtained from previous measurements using the same technique on Cu-Zn and Ag-Cd alloys had a linear dependence with composition.

By means of a simple argument the relative stacking fault energies for these alloys can be deduced and compared with those obtained on similar Cu-Ge alloys by Howie using thin-film electron microscopy and by Haasen and King using tensile tests.
Generalized Thermal J-V Characteristic for the Electric Tunnel Effect
Authors: Simmons John G.
Published: April 2005

The thermal J-V characteristic for a tunnel junction is derived in terms of a generalized theory. The resulting functional form of the equations is similar to that of Stratton; however, in the present formulation, the physical parameters of the junction appear explicitly, and their effect upon the thermal characteristic is readily appreciated. In Stratton's work, the physical constants appear in the integrand of integral that can be solved only numerically.

The theory is applied to symmetric and asymmetric junctions. For the symmetric case, it is shown that, at a given temperature, the percentage change Ĵ in the high-temperature thermal component of current from the low-temperature value increases initially with increasing voltage bias up to a maximum peak, and thereafter decreases rapidly. The voltage bias at which the component of thermal current maxima occurs is equal to the interfacial barrier height and, as such, permits what is probably the most accurate method of barrier height determination. Similar results are obtained for the asymmetric barrier; however, in this case, Ĵ depends upon the polarity of the voltage bias for V>φ1, and two Ĵ maxima occur at voltages corresponding to the two distinct interfacial barrier heights φ1 and φ2.
Potential Distribution and Negative Resistance in Thin Oxide Films
Authors: Hickmott T. W.
Published: April 2005

Al–SiO–Al–SiO–Au triodes with SiO thicknesses between 150 and 500 Å have been used to measure the potential distribution in thin oxide films before, during, and after the development of voltage-controlled negative resistance (VCNR) in the current-voltage characteristics. Development of VCNR in the triode is accompanied by the establishment of a high-field region about 120 Å in thickness near the negative electrode. If triode potentials are reversed after developing conductivity, VCNR is still found in the current-voltage (I-V) characteristic of the triode but the potential distribution in the triode is only slightly changed. VCNR in the I-V characteristic is a high-field phenomenon but it does not depend on field emission of electrons from the metal electrodes. Conductivity in the bulk of the insulator is Ohmic with electron mobilities ∼10−3−10−2 cm2/V-sec. The behavior of Al–SiO–Au diodes is identical to that of triodes. Electroluminescence of Al–SiO–Au diodes, which appears when conductivity is developed, is characterized by a steep rise in intensity at 1.8 V, the voltage at which electron emission into vacuum from such diodes is first detected. Both electroluminescence and electron emission provide evidence for high-energy processes in the oxide film. A phenomenological model of conductivity and voltage-controlled negative resistance in thin oxide films is developed in which impurity conduction is the most important conduction mechanism.
Acoustoelectric Effect
Authors: Eckstein S. G.
Published: April 2005

General expressions for the acoustoelectric current in the presence of external electric and magnetic fields have been derived. The Weinreich relation is shown to be valid in materials in which carriers of one sign only are present, to the extent that collision-drag effects may be neglected. The Weinreich relation is not valid for semimetals. However, in high magnetic fields, the acoustoelectric current and field in semimetals are proportional to the attenuation. The acoustoelectric field is then in the direction q×H, where q is the wave vector, and H the magnetic field. The acoustoelectric current reinforces the original direct current under amplifying conditions, in agreement with observations of anomalous magnetoresistance in Bi.
Diffusion in a Polymer With Lamellar Morphology, Polyethylene
Authors: Eby R. K.
Published: April 2005

Data for the diffusion of ethane in polyethylene are presented together with the results of optical microscopy and of large- and small-angle x-ray diffraction for the same samples. The orientation of the lamella boundaries with respect to the concentration gradient of the diffusing molecules is important in determining the diffusion rate. In unoriented, as-crystallized polymers, the diffusion constant varies inversely with the lamella thickness. The results support the concept of lamella boundary diffusion. Lamella perfection is also important. In both oriented and unoriented polymers, the solubility constant apparently varies inversely with the lamella thickness, suggesting absorption in the lamella boundaries.