bluuebunny/crossref_metadata_2025 huggingface dataset:
Interpretation of the Neutron or X-Ray Scattering from a Liquid-Like Binary
Authors: Keating D. T.
Published: April 2005

In the general liquid-like binary three radial densities relating to A-A, B-B, and A-B pairs are needed to characterize the scattering. The three densities can be obtained by the Fourier inversion of the weighted combination of three diffraction patterns, each of which differs by the alteration of the scattering of one or both components. If the density of atoms regardless of type is the same around both components, then only two functions, one this distribution, and the other involving the order between A-B pairs is needed to characterize the scattering. This case is the liquid analog of the crystalline alloy with short-range order. These two functions can be obtained by the Fourier inversion of a weighted combination of two patterns differing by the alteration of the scattering of the components.
Electrical Conduction in Discontinuous Thin Metal Films
Authors: Hartman Thomas E.
Published: April 2005

Evaporated or sputtered metal films of less than 100 Å average thickness are generally discontinuous and consist of a plane array of finite but very small particles. The level spacing of quantized electronic states becomes greater than kT for microparticles of this size. The electrical conduction mechanism of tunneling is dominated by transitions from the first excited level of one particle to the corresponding level in the next. The electrical conductivity is derived assuming tunneling as the conduction mechanism and results in an exponential dependence on reciprocal temperature in the limit of zero applied electric field. The activation energy depends on the particle size and is the difference in energy between the ground and first excited electronic levels in the particle. The results are in good agreement with published experimental data.
Duo-Emitter Diode
Authors: Hernqvist K. G. , Fendley J. R.
Published: April 2005

Theoretical and experimental studies of the duo-emitter diode are described. In this diode an electron emitter and an ion emitter are facing each other. Two space-charge configurations have been found for this diode, one where the interelectrode space is occupied by a dense plasma and one where potential barriers for the emitted particles exist near the emitters. The experiment, using a low-pressure cesium-vapor diode, gives results in good agreement with theory.
Ion Bombardment of Single Crystals of Aluminum
Authors: Cunningham R. L. , Gow K. V. , Ng-Yelim Joyce
Published: April 2005

This paper presents the results of bombarding the (100), (110), and (111) surfaces of aluminum single crystals with a narrow beam of 8-kV argon ions. The crystals were tilted at the angles required to bring [110], [100], [112], and [111] directions parallel to the beam. The experiments were designed to study the effect of incident ion direction on ejection directions and etching rates.

Ejection directions, as determined from the positions of deposits on hemispherical collectors, were found to be independent of incident ion direction for a given surface orientation. The quantity of material ejected along equivalent ejection directions was observed to decrease as the angle of deviation between the incident ion beam and the ejection direction increased. The principal ejection directions observed were [110]. Apparent [116] ejection directions were observed when (110) and (111) surfaces were bombarded. These were caused by an abrupt deflection of momentum from [110] directions of the crystal to directions close to [110] of elementary twins. These are formed by surface atoms in twin positions on (111) surfaces developed, in the case of the (110) surface, during bombardment. The [110] directions of an elementary twin are parallel to certain [114] directions of the crystal, and, had multilayer twins been formed, the resulting ejection would have been along apparent [114] directions as a result of Silsbee focusing. Ejection along apparent [116] directions was not observed from (100) surfaces presumably because predominant [100] surface grooves produced by bombardment could not contain (111) facets. Under these conditions [100] ejection was detected.

Etching rates, as judged by the occurrence of matte spots, were least when the beam was parallel to the close-packed [110] directions and greatest when parallel to high index directions making large angles with the [110] directions. Low etching rates were also observed when the beam became parallel to [100] and [112] directions. Any anisotropy in surface migration rates was shown to be negligible in controlling etching rates under the conditions of these experiments.
Conductivity of a Medium Containing a Dense Array of Perfectly Conducting Spheres or Cylinders or Nonconducting Cylinders
Authors: Keller Joseph B.
Published: April 2005

The effective electrical conductivity σ is computed for a composite medium consisting of a dense cubic array of identical, perfectly conducting spheres imbedded in a medium of conductivity σ0. When f, the fractional volume occupied by the spheres, is near its maximum value π/6, the result is σ/σ0=−(π/2)log [(π/6)−f]+…,(π/6)−f≪1. This result exhibits the singularity of σ at f=π/6, when the spheres touch each other. The previous results of Maxwell, of Rayleigh and of Meredith and Tobias are not valid near the singularity and they fail to reveal it. For f=0.5161 our result yields σ/σ0=7.65, while the measurement of Meredith and Tobias yielded σ/σ0=7.6.

For a medium containing a square array of perfectly conducting circular cylinders we obtain σ/σ0=π32/2[(π/4−f)]12+…,(π/4)−f≪1. This result agrees well with the numerical results of H. B. Keller and D. Sachs. We also prove that for any value of f, σ/σ0 for a medium containing a square array of nonconducting cylinders is the reciprocal of σ/σ0 for the same array of perfectly conducting cylinders.
Calculation of Crystallite Size Distributions from X-Ray Line Broadening
Authors: Bienenstock Arthur
Published: April 2005

The distribution of column lengths p(n)/Nc in a powder sample is given by the following combinations of the coefficients of the Fourier series expansion of the x-ray diffraction line shape: p(n)/Nc=(2An−An+1−An−1)/A0−A1).
Low-Energy Electron-Diffraction Study of the Surface Reactions of Germanium with Oxygen and with Iodine. II
Authors: Lander J. J. , Morrison J.
Published: April 2005

The effects of pressure and temperature on the O–Ge and I–Ge surface reaction systems were studied by means of low-energy electron-diffraction with single-crystal (100) and (111) surfaces. The results are very similar to those reported for silicon, but have a displacement to lower temperatures of about 350°C. On both surfaces the oxide films are amorphous, but well-crystallized two-dimensional iodide structures were obtained and the transitions to the iodides are ``reconstructive.'' The slopes for all four transitions from the ``clean'' surfaces correspond to energies of about 55 kcal/mole. Clustering phenomena are also discussed.
A Particular Solution of the Linearized Boltzmann Equation
Authors: Kent Gordon
Published: April 2005

A particular solution of the linearized Boltzmann equation, applicable to longitudinal oscillations of a one-dimensional plasma without collisions, is constructed. It has the properties that (i) the Vlasov dispersion relation (1) is satisfied rigorously; (ii) that for large values of time, the perturbation decays as 1/t½; and (iii) that the solution may be singular at some points. The solution is not included in the theories of Van Kampen or Landau because of (iii), but it is in no sense a general solution of the initial value problem. The frequency at which damping is slowest is approximately twenty-five percent above the plasma frequency.
A Single-Crystal X-Ray Study of Order in β′-AgCd
Authors: Walker C. B. , Marezio M.
Published: April 2005

A single-crystal x-ray study of β′-AgCd has confirmed that this alloy has the ordered CsCl structure and has shown that the order is essentially perfect at room temperature. The measurements illustrate the high sensitivity of single-crystal techniques in such studies.
Effect of Low-Temperature Phase Changes on the Mechanical Properties of Alloys near Composition TiNi
Authors: Buehler W. J. , Gilfrich J. V. , Wiley R. C.
Published: April 2005

X-ray diffraction and dilation studies have shown that alloys near the stoichiometric TiNi composition undergo transformation into the related phases Ti2Ni and TiNi3 at low temperatures. The main factors controlling these phase transformations are alloy composition, temperature, and mode of plastic deformation. In plastic deformation, tensile or compressive stressing produced separate and unlike decomposition phases; this finding was dramatically demonstrated by unique temperature-sensitive dimensional changes in plastically deformed specimens. Changes of large magnitude in vibration damping have also been noted and appear related to variations in the phase equilibria of the system.
DC Detection of Ferromagnetic Resonance in Thin Nickel Films
Authors: Egan W. G. , Juretschke H. J.
Published: April 2005

Experimental work on nickel films is presented which verifies the theory that the dc voltages accompanying ferromagnetic resonance in thin metallic films arise from the nonlinear electrical conduction terms in ferromagnetics involving the extraordinary Hall effect and the magnetoresistive anisotropy. Each of a group of four nickel films of different thickness was subjected to microwave pulses in well-defined configurations of local microwave fields, as required for quantitative comparison of theory and experiment, and the resulting dc pulses were studied as a function of applied magnetic field and of microwave power and field configuration. The results lead to a complete specification of the films' electrical and magnetic properties at microwave frequencies. The films studied showed low magnetization but similar relaxation times compared to bulk nickel. The microwave resistivity is usually larger than at dc and complex. The magnetoresistive anisotropy has its bulk value, while the extraordinary Hall constant is very large.
Effects of Transition Metal Solutes on the Thermoelectric Power of Copper and Gold
Authors: Christenson Elmer L.
Published: April 2005

The thermoelectric powers (TEP) of copper alloys containing dilute amounts of iron, cobalt, or chromium and up to 10 at. % manganese or nickel have been measured between 4.2° and 1000°K. Similar alloys of gold have been measured between 4.2° and 100°K. The individual solutes produce comparable effects in either solvent. In copper, 0.1% iron produces a minimum TEP of −14 μV/°K near 20°K. A similar level of cobalt produces a TEP of −10 μV/°K near 200°K. All of the solutes measured exhibited minima in the TEP vs temperature data, but nickel, manganese, and chromium are much less effective than cobalt or iron in altering the TEP of copper. The thermopower does not increase indefinitely with concentration. In gold, iron produces its maximum TEP at about 0.2 at. % concentration, cobalt at about 2%. Several of the alloys measured also exhibited maxima in the 4.2°K region, similar to results obtained by others with nontransition solutes. Resistivity counterparts for these TEP-temperature curves have been published earlier.
Internal Friction in the Tantalum-Hydrogen System
Authors: Kofstad Per , Butera Richard A.
Published: April 2005

Internal friction in a series of Ta-H alloys has been measured over the temperature range −190° to +250°C. Six peaks were observed at mean temperatures of −170°, −83°, 1°, 36°, 54°, and 210°C. The peaks occurring at −170°, −83°, and 1°C are found only in the samples containing greater than 33.3 at. % hydrogen. Both the −83° and the 1°C peaks have an amplitude dependence on the hydrogen concentration, suggesting that they are caused by stress-induced ordering of hydrogen in Ta2H. The 36° and 54°C peaks are compared with heat capacity data obtained by Saba, Wallace, Sandmo, and Craig and are assigned to the long and short range order of hydrogen in the Ta2H phase. Consideration is given to the effect of hydrogenation on the stress-induced ordering of interstitial oxygen and the activation energy of the stress-induced ordering of interstitial hydrogen. This consideration gives rise to the suggestion of both tetrahedral and octahedral locations for the hydrogen atoms in excess of 33.3 at. %.
Method of Determining Dynamic Properties of Viscoelastic Solids Employing Forced Vibration
Authors: Lee Tung-Ming
Published: April 2005

Both the longitudinal vibration method and the torsional vibration method are used for evaluating dynamic properties of viscoelastic solids. The criterion of using Rmax (the maximum amplitude ratio of the free end of a sample to the end attached to a driver) and fro (the corresponding vibration frequency) is introduced. The complex modulus is used to describe the stress-strain relationship for a viscoelastic solid. Simple expressions relating dynamic properties to Rmax and fro are obtained. When Rmax and fro are measured from experiment, one may readily determine the dynamic properties of the sample.
Influence of Anisotropy Dispersion on Magnetic Properties of Ni–Fe Films
Authors: Cohen Mitchell S.
Published: April 2005

The dispersion of the magnetic anisotropy was monotonically increased in several Ni–Fe films by subjecting them to increasingly severe heat treatments, and the room-temperature magnetic properties were monitored after each anneal by Lorentz electron microscopy. A gradual transition towards increasingly anomalous properties in a single film was thereby observed. An increase, with annealing, of the magnetization ripple intensity, the measured angular anisotropy dispersion, and the wall coercive force Hw was found. After sufficient annealing, locking was seen upon reversal parallel to the easy axis; further annealing increased the locking-wall density. The anisotropy field Hk monotonically decreased with annealing until the uniaxial character of the film was lost and it became a rotatable-initial-susceptibility (RIS) film. Reversal at azimuths away from the easy axis proceeded by labyrinth propagation after the early anneals, but by partial rotation after more severe annealing.
Attenuation of Pure Elastic Modes in NaCl Single Crystals
Authors: Papadakis Emmanuel P.
Published: April 2005

Pulse-echo ultrasonic attenuation measurements were made for longitudinal and transverse waves in the [100], [110], and [111] propagation directions in NaCl specimens cut from a single boule. The attenuation α was proportional to the orientation factor Ω (relating the resolved stress on the slip system of the crystal to the applied stress), and to the square of the frequency f. Under x-ray irradiation, α decreased for modes with Ω=≠0 but remained constant where Ω=0. Dislocation damping is considered to cause the loss.
Tunneling Current Density as a Function of Crystallographic Polarity
Authors: Minamoto Miriam T. , Malafi Hilary T.
Published: April 2005

Esaki diodes using the A and B or opposite {111} faces of zinc-doped gallium antimonide were fabricated using tin—tellurium spheres. Diodes made by alloying to the B face exhibit approximately an order-of-magnitude higher peak tunneling current density than those made by alloying to the A face. Differences are found in the junction geometries. Junctions fabricated by alloying to the B or {1̄1̄1̄} face are generally planar and delineation of these is pronounced, suggesting enhanced impurity concentration in their recrystallized regions. A or {111} face alloyed junctions are curved and tend to be obscurely delineated. The capitance per unit area of the B diodes was approximately twice that of the A diodes. Thus Jp/C values were typically 5–7 times higher for the B diodes. Calculations indicate, for typical A and B diodes, excess carrier concentrations 4.0×1018 and 1.5×1019/cm3, respectively. The higher tunneling current, the higher capacitance, and enhanced delineation of the planar B junction are apparently the effects of higher impurity concentration in the regrowth region due to the difference of the segregation coefficient of tellurium in gallium antimonide with crystallographic direction of growth.
Velocity Modulation of Propagating Waves
Authors: Landauer Rolf
Published: April 2005

Waves moving through a medium in which the wave velocity is a function of time and space suffer frequency changes. If the velocity modulation is small and adiabatic, very elementary kinematic considerations define these frequency changes. For a uniformly moving velocity pattern the frequency change suffered by a portion of the wave is shown to depend only on the wave velocity at the input and output end of the modulating system, and not on the intermediate velocities experienced by the wave. Electro-optic modulation and deflection experiments are treated in this framework. The paper is intended to present a particularly simple viewpoint, and does not arrive at really new results.
In-Pile Hall Coefficient and Conductivity Measurements on Zone-Refined,p-Type Silicon
Authors: Bailey G. C. , Williams C. M.
Published: April 2005

The Hall coefficient and conductivity have been measured during pile-irradiation for a number of zone-refined, p-type silicon crystals with initial resistivities of 1, 8, and 100 Ω-cm. To supply the magnetic field for the Hall measurements, a small electromagnet was used. The conductivity of zone-refined silicon shows much faster changes with irradiation than pulled silicon samples of equivalent resistivity. The 100-Ω-cm samples exhibit a monotonic nonlinear decrease of lnσ, conductivity, vs φf, integrated fast flux, whereas the other samples with initial Fermi levels closer to the valence band have one or two regions of linear decrease in lnσ vs φf before the nonlinear decrease region is observed. The Hall mobility for the 100-Ω-cm samples decreases and becomes negative as a result of the carrier density decreasing with irradiation. In the case of the 8-Ω-cm sample, the Hall mobility decreases with irradiation whereas the 1-Ω-cm sample shows no change in Hall mobility with irradiation up to the maximum integrated flux used in the present experiment. The origins of the dependence of lnσ on φf as well as the behavior of the Hall coefficient and Hall mobility with irradiation are discussed.
Average Neutron Energy of Reactor Spectra and Its Influence on Displacement Damage
Authors: Kantz A. D.
Published: April 2005

The average energy of the neutron spectrum for reactor sources may be evaluated to good approximation by a threshold-reaction technique using the activation of only two threshold-reaction foils. For plutonium (effective threshold 0.001 MeV) and sulfur (effective threshold 3.0 MeV) foils the average energy of a reactor spectrum is found to be Ē=7.42R+0.30 MeV, where R is the ratio of the number flux measured above the sulfur threshold to the number flux measured above the plutonium threshold.

The carrier removal rate per unit flux has been measured for vacuum floating zone n-type silicon (phosphorus-doped) as a function of the average energy of the reactor spectrum as measured by the two-foil method. Resistivities of 1-, 10-, and 100-Ω-cm samples were used in these irradiations at seven different reactor spectra. The carrier removal rate is found to be proportional to the average energy of the neutron spectrum. The highest average energy realized in the experimental work was 2.3 MeV.
CsCl-Type Compounds in Binary Alloys of Rare-Earth Metals with Gold and Silver
Authors: Chao C. C. , Luo H. L. , Duwez P.
Published: April 2005

In binary alloys of silver with Sm, Tb, Ho, and Tm, and of gold with Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm, intermediate phases containing stoichiometric proportions of the two metals were found to crystallize into the CsCl (B2)-type structure. The lattice parameters of these phases are reported and a correlation has been found between these lattice parameters and the trivalent ionic radii of the rare-earth metals.
Transient Growth of the Spin-Wave Population in a Strong RF Magnetic Field Applied Parallel to the DC Field
Authors: Schlömann Ernst
Published: April 2005

The transient phenomena that occur immediately after a strong microwave pulse has been applied to the sample are analyzed. The calculation is performed on a quantum-mechanical basis and assumes that the spin waves are in thermal equilibrium before the pulse is applied. Saturation effects are neglected. For this reason the theory is applicable only as long as the spin-wave amplitudes are not too large. General expressions for the transient time dependence of the dc and rf magnetic moments and for the power absorbed are derived. Simple results are obtained for the asymptotic behavior, realized after the microwave pulse has been applied for a long time. It is shown that the apparent critical field, at which spin-wave instability first becomes detectable, should depend approximately linearly on the inverse of the pulse length.
Applications of Miniature Coil, Pulsed-Field Techniques to Studies of Magnetic Phase Transitions
Authors: Flippen R. B.
Published: April 2005

A miniature coil, pulsed-field technique is described in which magnetic fields above 100 kOe can be easily obtained in 20- to 40-μsec pulse lengths. Detailed description is given of the apparatus. The use of such pulsed fields in study of antiferromagnetic-ferrimagnetic transitions in Mn1.90Cr0.10Sb is described. The transition latent heat in Mn1.90Cr0.10Sb is found to be 0.35 cal/mole°C from these measurements. Critical fields for ferromagnetic-antiferromagnetic transitions in holmium and dysprosium are determined with this technique. The transition entropy change in dysprosium is found to be 2.59×104 ergs/g°C. Spin flopping is observed in Mn1.84Cr0.16Sb between 20° and 85°C. The anisotropy field of the canted spin state in Mn1.84Cr0.16Sb is found to be of the order of 103 Oe. Pulsed field measurements of ferromagnetic-paramagnetic transitions are discussed. It is shown how this technique can be used to determine Curie temperatures of such transitions. Curie temperatures of 16° and 118°C are found, respectively, for gadolinium and CrO2.
Thermionic Properties of Some Refractory Metal Carbides
Authors: Ingold J. H.
Published: April 2005

The low-field thermionic emission properties of vacuum hot-pressed samples of MoC, Ta0.8Zr0.2C, TiC, HfC, TaC, and ZrC in polycrystalline bulk form have been measured over the temperature range 1300° to 1900°K. The samples were well characterized by metallographic examinations and x-ray diffraction analyses. A correlation between microstructure and thermionic emission was observed. The MoC sample was found to be the most copious electron emitter, while the ZrC sample, which was carbon deficient, had the smallest electron emission over the temperature range investigated.
Equation of State of 6061-T6 Aluminum at Low Pressures
Authors: Lundergan C. D. , Herrmann Walter
Published: April 2005

The Hugoniot equation of state of 6061-T6 aluminum was determined in the pressure range from 0 to 31 kbars from measurements of velocities of plane waves induced by plate impact. Below the Hugoniot yield point of 6.4±0.7 kbars, only an elastic wave was observed, while above both elastic and plastic waves were observed. The measured wave velocities corresponded closely to values predicted from elastic parameters for the material determined in static tests. Above the elastic limit, the free-surface velocity was less than the interface velocity by an amount slightly greater than predicted by theory, and appeared to be a function of target thickness.

The measured Hugoniot was found to correspond well with elementary elastic-plastic theory, in which the yield stress is assumed to be a constant, and the change in compressibility with compression is predicted by second order elastic theory. It was found that the measured Hugoniot yield stress corresponded to the static yield stress obtained in simple tension tests, and that the Hugoniot joined smoothly onto an extrapolation of the high pressure Hugoniot data of Walsh and Al'Tshuler.
Magnetic Domains in Orthoferrites by the Kerr Effect
Authors: Fowler C. A. , Fryer E. M. , Brandt B. L. , Isaacson R. A.
Published: April 2005

The successful application of the Kerr magneto-optic technique to observe magnetic domains in orthoferrite single crystals is described. A series of photographs portray domain developments in thick samples of YFeO3 and HoFeO3 similar to those previously revealed in thin, transparent sections by the Faraday effect. Quantitative measurements of the normal, polar Kerr rotation for the two orthoferrites are reported for several wavelengths, and an apparatus for making such measurements is described.
Photography of Magnetic Domains Using the Transverse Kerr Effect
Authors: Dove D. B.
Published: April 2005

A technique is described for photographing magnetic domains using the transverse magneto-optic Kerr effect. Domain photography by the longitudinal effect is, of course, a well-established technique, but we are unaware of previous use of the transverse effect in this connection. The method involves the use of crossed polarizers and a phase-adjusting arrangement. An expression is derived for optical contrast between adjacent domains.
Photocontrol of Growth Rate of Thin Polymer Films Formed by Electron Bombardment
Authors: Mayer Ludwig
Published: April 2005

This paper reports on an exploratory study concerned with the formation of thin polymer films on metal film substrates bombarded by slow electrons. The essential results of the investigation are: Cracking, polymerization, and crosslinking of organic molecules adsorbed on surfaces by electron bombardment can be achieved with electron energies as low as 6 eV. The formation rate of thin polymer films in the low electron region is voltage-dependent. Polymer films formed from organic molecules inherently present in a high vacuum system show electrical photoresponse in the visible and near-infrared region of the spectrum. By utilizing this photoresponse and the voltage dependence of the film growth rate, polymer film configurations can be grown which correspond to light patterns projected onto them.

All experiments were conducted in an electron mirror microscope which proved to ideally suited for this type of study. Such a microscope is a very sensitive tool for the detection and observation of extremely thin insulating films. It permits formation of thin polymer films in an easy fashion and it serves equally well as a convenient instrument for immediate detection and study of such films during growth. The transition from growing polymer films to observing them can be accomplished simply by switching the bias potential on the polymer film's conductive substrate.

In one example, illustrated by an electron mirror micrograph, the experimental procedures are described in detail.
Magnetic Properties of the Dual Oxide System CuO–Fe2O3
Authors: Milligan W. O. , Tamai Y. , Richardson J. T.
Published: April 2005

It has been demonstrated that hydrous ferric oxide and cupric oxide gels consist of very small particles and contain magnetically dilute Fe3+ and Cu2+ ions, respectively. Heating or aging these gels produces an increase in particle size with the onset of crystalline magnetic interactions. Coprecipitated samples of these oxides contain no CuFe2O4 when merely air-dried or heated at 170°C, but consist of mixtures of CuO and α-Fe2O3.

Higher heat-treatment of these samples up to 900°C results in mixtures of CuFe2O4 and/or α-Fe2O3 and CuO, with the amount of CuFe2O4 increasing with temperature of heat-treatment. Heat-treatment at 1100°C produces a solid solution of CuF2O4 and γ-Fe2O3 in the range greater than 40 mole % Fe2O3. Analysis of the ferrimagnetic magnetization and Curie points suggest that γ-Fe2O3 has a Curie point of 625°C and a magnetization of 65.0 emu/g. The results are consistent with cationic distribution of Fe[Fe5/3□1/3]O4 and Fe[CuFe]O4.
Current Flow in Very Thin Films of Al2O3 and BeO
Authors: Meyerhofer Dietrich , Ochs Stefan A.
Published: April 2005

This paper describes a study of current flow through very thin insulating films. Several possible conduction mechanisms are presented and their properties are discussed. The dominant conduction process in the layers studied is quantum-mechanical tunneling. Previous work on this mechanism is extended by an exact calculation which shows the current-voltage characteristic to be divided into three regions of different logarithmic curvature. The dielectric constant of the insulator is found to have a large effect, via the image force, on the tunneling current. The theoretical results are fitted to measurements made on insulating layers less than 100 Å thick, sandwiched between metal electrodes. For Al2O3 layers the fit is excellent, resulting in barrier heights of 2.0–2.5 eV and thicknesses approximately 25 Å less than the values determined from capacitance, as expected. In contrast the conduction characteristics of BeO layers can be explained by tunneling only in the low-voltage region; barrier height and thickness are similar to the Al2O3 case. At intermediate voltages the currents are lower than predicted and at high voltages reproducible hysteresis effects are observed with time constants of the order of minutes. These effects are only weakly temperature dependent. They appear to be due to tunneling from one of the metals into trap states in the forbidden gap of the insulator, creating space charge which distorts the barrier for tunneling.
Isotropic Permalloy Films
Authors: Fuchs E. , Zinn W.
Published: April 2005

Magnetically isotropic Permalloy films have been prepared by evaporation or vacuum-annealing in a 50-cps rotating field of crossed pairs of Helmholtz coils. The magnetization reversal in magnetically isotropic films is similar to that of films with uniaxial anisotropy in the hard axis or that of inverted films (Hc>Hk) in the easy and the hard axis. This is shown by hysteresis measurements on 25 film-matrix patterns and by electron micrographs. At zero field the magnetic structure is caused by the film inhomogeneities and by the wall and edge stray fields. The locked state characterized by a domain splitting perpendicular to the applied field occurs when the reversed field is increased. Locking disappears at the coercive field strength by migration of Bloch lines on the Néel walls. Locking by partial rotation is not possible with Hk=0. Maze-like domains occurring in an increasing field applied obliquely or perpendicularly to the previous saturation direction are caused by stray field coupling between strips of varying magnetization direction already present at zero field.
Microwave Reflection from Small-Diameter Plasma Columns
Authors: Stern R. A.
Published: April 2005

The scattering cross section of electromagnetic waves incident normally on a small-diameter plasma column exhibits resonances as a function of plasma density when the waves are polarized at right angles to the axis of the column. The electron density at resonance has been measured, using a microwave cavity technique, in pulsed helium arc discharges, as the frequency of the incident microwaves was varied from 2 to 4 kMc/sec. At resonance, the squared ratio of plasma frequency to incident frequency is found to be independent of frequency and neutral gas pressure, but somewhat dependent on pulse duration. Results are in qualitative agreement with recent analyses of the interaction between electromagnetic fields and thermal plasmas with finite dielectric boundaries.
Calculation of Fields, Forces, and Mutual Inductances of Current Systems by Elliptic Integrals
Authors: Garrett Milan Wayne
Published: April 2005

A minimum-ordered set of elliptic integral equations is given for magnetic vector potential, axial and radial fields, the mixed gradient ∂Bρ/∂z for axially symmetric iron-free current systems, and for mutual inductance and force between coaxial units. The units may be circular loops, cylindrical or plane annular current sheets, or coils of thick section. With full use of correlations, six basic equations suffice for all properties of loops, solenoids, or combinations. The axial solenoid field is calculated by a superior new method. Thick coils are analyzed with the solenoid rather than the loop as element. Magnetic properties are then integrated in radial depth by Gaussian numerical quadrature of variable order. This method can deal with coils whose sections are not rectangular, and whose current densities are a function of the cylindrical radius.

No tables are used, and the procedure is simpler and faster than previous methods, for computer use or for solving smaller problems by hand. It has been coded as a unified set of programs for the IBM 7090. These will be described elsewhere; they can compute fields, and trace lines of force even within the windings, or force and mutual inductance between coils in contact, also self-inductance of ideal solenoids or of thick cylindrical coils. Errors are normally less than one part per million, in extreme cases less than one per thousand.
Ion-Emission Requirements for Removal of Electron Space-Charge Barriers
Authors: Hansen L. K. , Warner C.
Published: April 2005

A space-charge analysis is made for a parallel plane, collisionless diode where ions as well as electrons are generated at the emitting electrode. The resulting potential distributions are examined to determine the required conditions for diode operation in the retarding field, space-charge-limited, or the saturated emission mode. Such analyses have already been given for vacuum diodes. This paper first summarizes and then generalizes these results.
Electron Reflection from Cesium-Coated Polycrystalline Metals at Low Primary Energy
Authors: Zollweg R. J.
Published: April 2005

The reflection of low-energy electrons from polycrystalline metal surfaces partially coated with cesium has been investigated by the retarding potential difference technique. The technique is described and results for primary energies below 5 eV are given. Retarding potential measurements of the longitudinal component of the reflected electron energy are consistent with elastic reflection and a cosine angular distribution at low primary energy.
Direct and Indirect Tunneling in Germanium at Different Temperatures
Authors: Breitschwerdt K. G.
Published: April 2005

The current—voltage characteristics of narrow germanium p—n junctions, measured for reverse biases at 4.2°, 77°, 195°, and 298°K, are in agreement with the usual tunneling probability expressions. The reverse current increases at the onset of the direct tunneling transition, that is, in addition to the indirect transition at lower biases. The onset voltage shifts from −0.121 V at 4.2°K to −0.082 V at 298°K in agreement with the band shift in germanium and the smeared-out carrier distribution around the Fermi level. The absolute value of the onset voltage is within 16% of the calculated voltage. The slope d ln(J/V)/dV is −11 (V)−1 for a typical junction; the constant field approximation gives −7 (V)−1.
Approximate Electromagnetic Transition Probabilities and Relative Electron Excitation Cross Sections for Rare-Gas Masers
Authors: Statz H. , Tang C. L. , Koster G. F.
Published: April 2005

Numerical values for the electromagnetic transition probabilities for a large number of rare-gas maser lines are calculated and tabulated for assisting in the evaluation of existing and new gaseous masers as well as for other applications such as work in astrophysics. In addition, in order to determine the dominant pumping mechanisms in such masers, an approximate method has been developed for calculating the relative cross sections under electron impact for production of various excited states from the ground state of the rare-gas atoms. A brief discussion of the experimental observations in the rare-gas masers is made in terms of the results given here.
X-Ray Diffraction and Diffusion in Metal Film Layered Structures
Authors: Dinklage J. , Frerichs R.
Published: April 2005

Artificial layered structures that produce sharp diffraction of x rays are described. The structures were made by alternately evaporating 140 Pb and Mg layers onto a glass slide (d=27 Å). The diffracting efficiency of the layered structures is compared with other structures used in soft x-ray spectroscopy. The usefulness of the structures is limited by diffusion in the layered system which caused the diffraction pattern to decay to half intensity in 2 days at room temperature. At 0°C the half life was 5 weeks. The diffusion model of DuMond and Youtz was used to determine an effective diffusion constant for the system over the temperature range 0–62°C. The equation Deff=5.2×10−6 exp(−20 600/RT) cm2/sec was satisfied.
A Comparison of the Elastic Constants of Chromium as Determined from Diffuse X-Ray and Ultrasonic Techniques
Authors: Sumer Ali , Smith J. F.
Published: April 2005

The elastic constants of the same single crystal of chromium have been determined by both ultrasonic pulse-echo and thermal diffuse x-ray techniques. The difference between the numerical results of the two sets of measurements is primarily attributable to the limited precision which attends the measurement of diffuse x-ray intensities. Any additional factors which may contribute to the difference are masked by the precision. If suitable single crystals can be prepared, the ultrasonic technique is much to be preferred.
Representation of a Function by Its Line Integrals, with Some Radiological Applications
Authors: Cormack A. M.
Published: April 2005

A method is given of finding a real function in a finite region of a plane given its line integrals along all straight lines intersecting the region. The solution found is applicable to three problems of interest for precise radiology and radiotherapy: (1) the determination of a variable x-ray absorption coefficient in two dimensions; (2) the determination of the distribution of positron annihilations when there is an inhomogeneous distribution of the positron emitter in matter; and (3) the determination of a variable density of matter with constant chemical composition, using the energy loss of charged particles in the matter.
Residual Temperatures of Shocked Copper
Authors: Taylor John W.
Published: April 2005

A photoelectric technique is described for measuring the residual temperature of strongly shocked metals. Data for copper shocked to pressures ranging from 0.9 to 1.7 Mbars are in good agreement with published calculations of temperatures.
Implications of the Intensity Dependence of Photoconductivity in Metal-Free Phthalocyanine Crystals
Authors: Heilmeier G. H. , Harrison S. E.
Published: April 2005

The evaluation of phthalocyanine as a photoconductive material has lead to the unusual result that the photocurrent varies as the one-third power of the light intensity. In this paper, this effective desensitization is analyzed in terms of diffusion effects involving the surface.
Temperature Effects in Coherent GaAs Diodes
Authors: Engeler W. E. , Garfinkel M.
Published: April 2005

The radiation output of GaAs coherent diodes has been studied for temperatures between 4° and 125°K. The coherent output follows the temperature variation of the band gap of pure GaAs. The threshold current follows no simple temperature dependence. It rises exponentially for temperatures below 30°K with the slope 0.9%/°K and seems to vary as T3 for T above 100°K. The temperature variation of the cavity modes is calculated, and agrees with experiment to within 5%. These results are briefly discussed in terms of a band-to-band model for the radiation.
Plasma Edge in Bi2Te3
Authors: Sehr Robert , Testardi Louis R.
Published: April 2005

The reflectance minima associated with the free carrier plasma edges in p- and n-type Bi2Te3 have been observed at 78° and 300°K. The data together with the measured Hall and Seebeck coefficients have yielded combined band structure-relaxation time parameters when proper account is taken of the anisotropy. These are compared with the results of other experiments from which similar information has been obtained. For n-type Bi2Te3 fair agreement is found with galvanomagnetic and optical band structure determinations. For p-type material the agreement with the results of similar experiments is considerably poorer but recent de Haas—van Alphen and galvanomagnetic measurements have established the value of the parameter measured in this experiment to within approximately the experimental error.
Migration of a Liquid Zone through a Solid: Part I
Authors: Tiller W. A.
Published: April 2005

The migration of slab, cylindrical, and spherical zones through a block of solid under the influence of a temperature gradient has been analyzed theoretically. The relative rates of migration are in the above order if KS>KL and the reverse order if KS<KL (K=thermal conductivity, S=solid, L=liquid). The migration rate was predicted to be directly proportional to the temperature gradient in the system and to depend upon orientation-dependent atomic kinetics of the melting and freezing processes. The magnitude of the atomic kinetic effect was predicted to depend upon the size of the molten zone and the particular mechanism of crystal growth which is operative. Fit with experimental data on the migration of Ge–Al cylindrical zones through Ge indicate that a screw-dislocation mechanism is operative. Finally, stable zone migration was predicted to occur only in certain crystallographic orientations in agreement with the observations on the Ge–Al cylindrical zones.
Migration of a Liquid Zone through a Solid: Part II
Authors: Tiller W. A.
Published: April 2005

The migration of slab, cylindrical, and spherical zones of liquid through a solid under the influence of an electric field has been analyzed theoretically. The absolute magnitude of the migration velocity has been predicted to be directly proportional to the macroscopic potential gradient E*; the relative migration rates for these zone shapes was found to be in the order slab>cylinder>sphere for ζS>ζL and in the reverse order for ζS<ζL (ζ=dielectric constant, S=solid, L=liquid). An analytical expression has been developed for the zone migration velocity in terms of (i) the effective ionic mobility of the solvent atoms U, (ii) the Peltier coefficient at the solid—melt interface SPL, (iii) the imposed macroscopic field gradient E* and temperature gradient G*, (iv) the zone size l, and (v) the atomic kinetics of the freezing and melting processes. It was determined that the zone could migrate either up or down the potential gradient E* depending on the magnitude and sign of U, SPL, and G*.
Fission-Fragment Damage in Gold Films
Authors: Merkle K. L. , Singer L. R. , Hart R. K.
Published: April 2005

The effects of fission-fragment irradiation on evaporated single-crystalline gold films have been studied by transmission electron microscopy. The outstanding feature observed after irradiation is the appearance of black spots of 20 to 300 Å in diameter. These images are diffraction effects caused by damage regions and their surrounding strain field. It is believed that the damage regions are produced by energetic primaries. In some instances the defects could be identified as triangular dislocation loops on (111) planes. Dark-field observations indicate that defects with a compressive as well as defects with a tensile strain field are present. From determinations of the density of spots it is concluded that the average fission fragment produces 25 spots along its path in gold.
Structure Defects in Pyrolytic Silicon Epitaxial Films
Authors: Miller D. P. , Watelski S. B. , Moore C. R.
Published: April 2005

Metallographic and electron microscopic examination of defects in silicon epitaxial films, grown on silicon wafers on graphite heaters, disclose the origin and characteristics of ``faults'' and tetrahedral growths. The occurrence of ``snowstorm'' spheres has also been investigated. Silicon carbide has been identified epitaxial on (111) substrates etched in hydrogen. The carbide grows as thin needles against the {1̄1̄2} step risers of the [111] zone. The steps appear to be formed during the room temperature oxidation of the silicon wafer surface prior to hydrogen etch. The ``faults'' are shown to be twin lamellae resulting from overgrowth of the carbide by the silicon. The methane transport reaction is proposed as the cause of carbide formation. Tetrahedral growths are shown to result from silicon nucleating directly on the carbide away from surface steps. They are twinned to the substrate, and grow faster than the adjacent epitaxial film. Their growth morphology is discussed. The spheres are polycrystalline silicon—silicon carbide matrices apparently resulting from reacted carbon particles which settle upon the substrate at the same time.
On Strain-Enhanced Diffusion in Metals. III. Interpretation of Recent Experiments
Authors: Ruoff A. L. , Balluffi R. W.
Published: April 2005

A critical interpretation of recent experimental results on the effects of plastic deformation on diffusion is carried out with the aid of the results established in the preceding Parts I and II. Attention is focused on experiments carried out at elevated temperatures (higher than half the absolute melting temperature) in which diffusion occurred over macroscopic distances. The results are discussed in terms of the following possible causes of apparent enhanced diffusion: (1) generation and migration of excess point defects during deformation; (2) short-circuiting along static or moving dislocations or grain boundaries created in the deformation; (3) short-circuiting along cracks created in the deformation; and (4) experimental difficulties associated with interface roughness. Causes (3) and (4) are of little basic interest but must be considered in any survey of experimental results.

Fourteen experiments in all are considered. Ten of these experiments showed no apparent enhancements within the expected experimental error of about 50% in the diffusivity. In one of these ten experiments a large enhancement was reported, but is is shown that this was due solely to an error in mathematical analysis.

Two of the experiments showed large apparent enhancements, and it is shown that they were almost certainly due to (4). One of the experiments showed apparent enhancements due to (3) but showed no enhancement in the absence of cracking. One of the experiments showed enhancements which, it is concluded, are not inconsistent with present knowledge of (2). [Very recent work by Brown and Blackburn (unpublished) indicate that at least some of the enhancements in this experiment may have been due to (4)].

It is generally concluded that in no case has a diffusion enhancement been detected due to the generation of excess vacancies. However, enhancement in one case may have occurred as a result of short-circuiting. These results are consistent with other high temperature deformation phenomena, e.g., creep kinetics, and are also consistent with the point defect and short-circuiting models developed in the preceding Parts I and II which predict very small effects due to point defects and possibly larger effects in certain cases due to short-circuiting.
Range and Damage Effects of Tunnel Trajectories in a Wurtzite Structure
Authors: Beeler J. R. , Besco D. G.
Published: April 2005

This article describes machine calculation results on some specific effects that the tunneling of energetic atoms in a crystal lattice enforces on the range and damage productivity of these atoms. Tunneling refers to the alignment of an energetic atom trajectory with the axes of straight, open cylindrical avenues in a crystal lattice. The stopping power for a tunnel trajectory is anomalously small and the range anomalously large. The particular case of 2-keV beryllium and 6-keV oxygen primary knock-on atoms (PKA) in BeO (wurtzite structure) is treated. With respect to the inducement of tunneling, our results indicate that the initial azimuthal direction of a PKA in a plane parallel to the wurtzite basal plane is a more important parameter than the position of its starting position on a line normal to this plane. Oxygen PKA manifested quasitunnel behavior when the azimuthal angle was within ±10° of a tunnel direction and beryllium PKA manifested this behavior over a ±25° sector centered on a tunnel direction.