bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation of Dielectric Constant with Voltage in Ferroelectrics and Its Application to Parametric Devices
Authors: Johnson Kenneth M.
Published: April 2005

A functional relationship between dielectric constant and voltage for a ferroelectric in the paraelectric state is derived, and Fourier capacitance coefficients for different applied voltage functions are computed. It is shown that because the loss tangent of a ferroelectric in the paraelectric state is proportional to frequency, it can be represented in the same way as a varactor; i.e., as a series resistance and capacitance. It is concluded that since the power-handling capability of single-crystalline ferroelectric is virtually unlimited, and since in many cases it has lower loss than a varactor diode, it will soon find wide application in parametric device design.
Crystal Habits of GaAs and GaP Grown from the Vapor Phase
Authors: Crocker A. J.
Published: April 2005

GaAs grown from the vapor phase is found, at near equilibrium, to form nearly spherical crystals bounded by {111} and {110} faces. Under nonequilibrium conditions whiskers are formed which on etching can be made to reveal structure.
Mid-Field Forward Scattering
Authors: Beard C. I. , Kays T. H. , Twersky V.
Published: April 2005

Experimental and theoretical results are given for forward scattering by spheres with radius large compared to wavelength, and with index of refraction η near unity. Both the intensity and phase of the scattered field (relative to that incident) are measured and computed for several spheres as functions of the separations of transmitter and receiver from the scatterer (say T and R). The scattering function of primary interest is that which reduces to the usual scattering amplitude in the limit of transmitter and receiver essentially at infinity—say, the function F such that F→f0 as T and R→∞. Differences between F and f0 arise from ``quadratic phase error'' terms involving not only the apertures of the horns, but also the size and dielectric properties of the scatterer. In the ``mid-field region,'' where the sphericity of the wavefronts is significant, the magnitude of the corrections introduced in F is of the order of Imf0, and Imf0 itself is an order of magnitude smaller than Ref0; consequently, although the ``finite geometry'' has only a second-order effect on the forward intensity |F|2, it has a first-order effect on the forward scattered phase arc tan[ImF/ReF]. In addition, since Imf0 is proportional to the total scattering cross section, the sphericity of the wavefronts has a first-order effect on the intensity integrated over all angles. Differences of a hundred percent in the phases of F and f0 may be encountered even in measurements for which T and R fulfill the usual ``far-field criterion.'' However, approximations for the far-field phase may be obtained by extrapolating measurements for several values of T and R in the usual laboratory geometry.
Defect Structures Observed in Neutron-Bombarded Aluminum
Authors: Bierlein T. K. , Mastel B.
Published: April 2005

Aluminum irradiated at approximately 60°C with neutrons has been examined by transmission electron microscopy. Results differ from those reported by other investigators. Small dislocation loops and larger dislocation rings form during an exposure of 3×1018 nvt (E>1 MeV) and increase in number with increasing irradiation dose. It is suggested that the small loops are prismatic loops which arise from the clustering and subsequent collapse of vacancies produced by neutron bombardment. Dislocations which encounter prismatic loops frequently form rings about the loops or other obstacles.
A New Semiempirical Equation for Gas Flow through Capillaries
Authors: Creutz E. S. , Zumwalt L. R.
Published: April 2005

A new equation for gas flow through capillaries in low and intermediate pressure ranges is derived without attempting to distinguish between Poiseuille flow with slip and Knudsen flow. It is assumed here simply that the total flow has two components, one characterized by an effective mean free path and the other by an effective viscosity, both of which depend on the ratio of the average pressure in the capillary to a characteristic pressure p1 and, in addition, on the mean hydraulic radius of the capillary and properties of the gas. At low pressure, the usual expression for Knudsen flow is obtained, but in a form which separates out a term, due to a viscous effect, that is related to the ``free-molecule viscosity.'' At high pressure, Poiseuille flow with slip is obtained, but the slip term is cast in a new form in terms of the characteristic pressure p1. Also, our equation has a minimum in the relationship between the permeability and the pressure, which is not given by most permeability formulas but which is observed experimentally under some conditions. At this minimum, diffusion flow and viscous flow are equal in magnitude. At pressures below that corresponding to minimum flow, the phenomenon becomes more ``diffusionlike'' and at higher pressures more ``viscouslike.''

Original data of Knudsen and Klose on the flow rates of various gases through capillaries are well fitted by this new equation at low pressure as well as in the ``transition region'' between Knudsen flow and Poiseuille flow. This fit is obtained by setting the adjustable constant α, which defines p1, equal to unity. Elementary theory of the slip-flow correction also indicates that α should be about unity. Results obtained with this equation are compared with those obtained with Knudsen's four-constant formula.
Elastic Constants of Calcite
Authors: Peselnick Louis , Robie Richard A.
Published: April 2005

The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25°C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=−2.00, in units of 1011 dyn/cm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar.
Arc Cathode Emission Mechanisms at High Currents and Pressures
Authors: Neurath Peter W. , Gibbs Thomas W.
Published: April 2005

Cathode emission was studied at over 1 atmosphere pressure into He and A plasmas at 100- to 500-A total current. The cathode spot temperature and current density were measured by a high speed photometric method developed for this purpose. A low vacuum thermionic work function was found to be a most important criterion for long cathode life. Emission current densities of the order of 100 to 200 A/mm2 were found to be independent of total current; surface temperature, typically, increased 300°C for the 5-fold increase in current and was approximately 2500°C in argon for a thoriated W cathode. Calcium-barium-aluminate-impregnated W cathodes operated well in such an arc, remaining at very low temperatures, confirming the results obtained with the thoriated W.
Ferroelectric Switching and the Sievert Integral
Authors: Fang P. H. , Stegun Irene A.
Published: April 2005

A connection between some ferroelectric switching functions and the Sievert integral is established. Switching functions of Landauer et al. and of Franklin are computed and discussed.
Tables of the Conductivity Coefficients in Transverse Magnetic Fields K(γ) and L(γ)
Authors: Gray Peter V.
Published: April 2005

Tables of K(γ) and L(γ) as defined by Willardson et al. are given over the range in which simple (high and low field) approximations are not valid. The tables permit easy multi-band calculation of the transverse magnetoresistance and isothermal Hall coefficient as a function of magnetic field in nondegenerate semiconductors in the lattice scattering range.
Identification of Precipitates on Grown-In Dislocations in MgO
Authors: Venables John D.
Published: April 2005

It has been shown through means of transmission electron microscopy that precipitate particles decorate grown-in dislocations in commercially available single crystal MgO. It has now been possible to show by means of electron diffraction that these precipitate particles are ZrO2 and that they are formed even when the Zr concentration in the MgO is as low as 1 ppm.
Piezoresistive Properties of Silicon Diffused Layers
Authors: Tufte O. N. , Stelzer E. L.
Published: April 2005

The piezoresistive properties of n- and p-type layers formed by the diffusion of impurities into silicon have been investigated. The values of the three piezoresistance coefficients and the temperature dependence of the large coefficients have been measured on layers having surface concentration values from 1018 to 1021 cm−3. The piezoresistance effect in p-type diffused layers follows qualitatively the behavior expected in a degenerate semiconductor. n-type layers having high surface concentration values show a change in the symmetry of the piezoresistance effect at room temperature and a decrease in the coefficient π11 at lower temperatures. A discussion of the piezoresistance effect in diffused layers and its relation to the piezoresistance effect in uniformly doped material is also given.
Metal—Semiconductor Barrier Height Measurement by the Differential Capacitance Method—One Carrier System
Authors: Goodman Alvin M.
Published: April 2005

The differential capacitance measurement for determining the height of a Schottky barrier at a metal—semiconductor contact is based upon a number of assumptions. In practice, one or more of these assumptions may not be valid. Some of these deviations from the ``ideal case'' are examined in order to determine the effects of each upon the interpretation and validity of measurements on such contacts. Specifically, the effects of each of the following are considered: series resistance, traps in the depletion layer, effective contact area variation with depletion layer width, an insulating interfacial layer between the metal and semiconductor, semiconductor surface charge variation with bias voltage, and the reserve layer at the edge of the barrier. Experimental data for gold plated contacts to conducting cadmium sulfide single crystals are given to illustrate some of the results.
Frictional Properties of Polyvinyl Chloride
Authors: Sieglaff C. L. , Kucsma M. E.
Published: April 2005

The frictional properties of rigid and plasticized PVC have been measured as a function of temperature, speed of test, applied load, and plasticizer content. It was found that the data could be correlated by the simple equation F=F*[1−exp(−kf)], where F is the frictional force, F* is a limiting frictional force dependent upon temperature and composition, and f is the applied normal force. The constants F* and k could be correlated with the tensile strength and the bulk modulus, respectively. A mechanism of polymer frictional behavior is proposed.
Stress Anisotropy in Silicon Oxide Films
Authors: Priest J. , Caswell H. L. , Budo Y.
Published: April 2005

The residual stress in films formed by vacuum sublimation of bulk silicon monoxide has been studied as a function of the angle of incidence of the evaporant. Using a source temperature of 1350–1400°C and a system total pressure of ∼2×10−6 Torr, a pronounced dependence of stress on angle of incidence and a distinct stress anisotropy was observed. The stress in the x direction (i.e., perpendicular to the direction of the evaporant irrespective of substrate orientation) increases from 4×108 dyn/cm2 for normal incidence to 14×108 dyn/cm2 for an incident angle of ∼50° and then decreases to 4×108 dyn/cm2 for an incident angle of 80°. The stress in the y direction (i.e., perpendicular to the x direction) is peaked at ∼30° at a value of 13×108 dyn/cm2 and then decreases to ∼0.5×108 dyn/cm2 at 80°. Films formed at normal incidence are quite stable and not susceptible to the effects of water vapor. However, films formed by depositing at grazing incident angles (>30°) are very unstable and invariably buckle and rupture when exposed to atmospheres of water vapor. Substrate temperature, film thickness, and inert residual gases were found to have little effect on the stress and stability of films deposited at an angle of incidence of 45°. When a lower source temperature (<1200°C) is used and a high partial pressure (10−4 Torr) of water vapor is present during deposition, the resulting highly oxidized films show a compressive stress (∼2×108 dyn/cm2) and very little dependence on the angle of incidence. These films are stable when exposed to higher partial pressures of water vapor.
Use of Induction Heating for Floating Zone Melting above 2000°C
Authors: Johnson Robert W.
Published: April 2005

The method described uses an eddy current concentrator to focus the energy of an rf magnetic field on a small part of a ¼-in.-diam rod. Zone melting has been carried out at temperatures above 2600°C, and can probably be extended to temperatures above 3000°C. The advantages of this method over some others used in the same temperature range are that it can be carried out under an inert gas atmosphere instead of a vacuum, and uses for its power supply conventional 450-kc induction heating equipment.
Crystallographic Polarity of ZnO Crystals
Authors: Mariano A. N. , Hanneman R. E.
Published: April 2005

The crystallographic polarity of the noncentrosymmetric material zincite (ZnO) has been determined by a rapid x-ray absorption edge method. The polarity results have been correlated to marked differences in etching behavior and crystal morphology in opposite polar directions of ZnO crystals. These differences are shown to be consistent with the proposed surface bonding model for AII-BVI compounds. Crystal morphology is shown to be a useful criterion to indicate crystallographic polarity in well-formed wurtzite-type crystals.
Thermoelectric Properties of Diphasal Systems Combining As2Te3 and Tl2Se with Sb2Te3, Bi2Te3, or Sb2Se3
Authors: Uphoff H. L. , Healy J. H.
Published: April 2005

Fourteen sample compositions, representing combinations of As2Te3 and Tl2Se with Sb2Te3, Bi2Te3, or Sb2Se3, were prepared and tested. A number of the samples were amorphous while others were diphasal including both amorphous and crystalline phases. The material parameters were structure dependent with room temperature parameters ranging from 7.2×10−4–1.8×103 Ω-cm in resistivity, 3.1–1040 μV/°K in Seebeck coefficient magnitude, and 3.6–19.0 mW/cm-deg in thermal conductivity.
Sliding and Wear in Ionic Crystals
Authors: Steijn R. P.
Published: April 2005

Wear tests by sliding single crystals of calcium fluoride, sodium chloride, magnesium oxide, and lithium fluoride on their natural cleavage faces beneath a weighted indenter are described. The slip systems responsible for the resultant deformation were determined and details thereof studied microscopically with the aid of etchants to reveal dislocation etch pits. In calcium fluoride, the structure of the material in the wear track is interpreted as a damage structure called ``friction damage.'' Etching revealed clusters of point defects left behind by moving screw dislocations. Subsequent annealing in inert atmospheres produced microscopically visible cavities a short distance below the wear track. Their possible origin and role in surface deterioration and wear are discussed. In calcium fluoride, surface cracks emanating from the wear track lie along ordinary cleavage faces; in rock-salt-type crystals, however, they are interpreted as dislocation cracks on the dodecahedral planes.
Influence of Vacuum Conditions on Epitaxially Grown Permalloy Films
Authors: Baltz Alfred
Published: April 2005

Permalloy films (83 wt% Ni-17 wt% Fe) epitaxially grown on (100) NaCl were examined in the electron microscope before and after beam annealing. An ultra-high vacuum system with an ultimate vacuum of 10−10 Torr and a vacuum system with an ultimate vacuum of 10−6 Torr were used for the evaporation. Films at 10−5 Torr were prepared in both systems to rule out the influence of the vacuum system on the films. Evaporation rates were adjusted to either 30 Å/sec or 14 Å/min. Electron micrographs and electron diffraction patterns showed that the films ranged from polycrystalline for films evaporated at 30 Å/sec and 10−5 Torr to single crystalline with grains of several millimeters diameter for films evaporated at 30 Å/sec and 10−9 Torr. The crystallographic misorientation varied widely in films which were partially single crystalline and amounted to only a few degrees over areas up to ⅛-in. diameter for films which exhibited perfect single-crystal electron diffraction patterns.
Avalanche Effects in Silicon p—n Junctions. I. Localized Photomultiplication Studies on Microplasmas
Authors: Haitz R. H. , Goetzberger A. , Scarlett R. M. , Shockley W.
Published: April 2005

An improved experimental technique is described for the investigation of carrier multiplication in very small areas, particularly microplasmas. A light spot of a few microns diameter is positioned to cover a microplasma of comparable or smaller size and the multiplied photocurrent is measured as a function of reverse voltage.

When the size of the microplasma is much smaller than the light spot, then the multiplication as a function of voltage is dependent upon the characteristics of the microplasma in an upper voltage range just below the microplasma breakdown voltage. In a lower voltage range the microplasma has negligible effect on multiplication. By comparing for the upper and lower voltage ranges the behavior of the reciprocal of the multiplication factor as a function of voltage, it is possible to determine that the diameters of the area of the microplasma regions vary from less than one to more than 5 μ.

Multiplication factors as high as 106 were measured. At high multiplication (M>100), a deviation from the theoretically expected linear dependence of 1/M vs V is observed. This deviation can be described by two effects: (1) the influence of the space charge of the multiplied carriers and (2) the pulsing mechanism of the microplasma. Because of this deviation, microplasma diameters of less than 1 μ cannot be accurately determined.

Another consequence of the pulsing effect is an apparent negative resistance in the V—I characteristic of a diode containing a microplasma. Dependence of the apparent negative resistance on load resistance, shunting capacity, and light intensity was investigated, and can be explained with the pulse model.
DC Electroluminescence in Thin Films of ZnS
Authors: Goldberg P. , Nickerson J. W.
Published: April 2005

Electroluminescent thin films of the composition ZnS:Cu,Mn,Cl, which are capable of dc excitation, are examined for their optical, chemical, and electrical properties. The emission is dominated by electronic and ionic processes occurring at the anode. A model is proposed for the excitation mechanism which is based on hole injection across a heterojunction composed of ZnS and a copper-rich phase. The mechanism explains emission at lower-than-band-gap voltages. The spectrum of the yellow emission of Mn in these films is composed of two closely spaced emission bands and is, therefore, different from the known yellow emission from Mn in ZnS phosphors.
Microwave Frequency Multiplication by Hot Electrons
Authors: Seeger Karlheinz
Published: April 2005

An experimental study is made of microwave frequency multiplication observed in germanium at power levels of several kW. Using a fundamental frequency of 9.4 Gc/sec, a third harmonic yield of about 1% was found. The data agree with calculations based on the observed deviations from Ohm's law. The anisotropy and the high frequency limit of the multiplication are calculated.
Polynomial Approximation to Focal Constants of Equidiameter Two-Cylinder Lenses
Authors: Morikawa Minoru
Published: April 2005

The approximate polynomials to the focal constants of equidiameter coaxial two-cylinder lenses are given by making use of the methods which are used to approximate elementary functions for computer applications. The range of voltage ratio Φ2/Φ1 of two cylinders are taken as 1/20≲Φ2/Φ1≲20. The polynomials obtained by Chebyshev expansions are better than those obtained by Taylor expansions. The convergence of the expansion depends greatly on the choice of the expansion parameters (arguments) as well as on its range. The polynomials of the 8th degree, obtained from the partial sums of Chebyshev expansions with the parameter x=½ log(Φ2/Φ1), give smaller relative errors than 2×10−4 in the above range for the focal constants of the lenses with typical axial potentials.
Paramagnetism and Lattice Spacings of Some Cerium-Rich Cerium—Europium Alloys
Authors: Arajs Sigurds , Chessin Henry , Colvin R. V. , Dunmyre G. R.
Published: April 2005

Paramagnetic susceptibility of cerium-rich cerium-europium alloys has been studied from 300° to 1050°K. These measurements indicate that the electronic structure of the localized 4f-electrons of europium atoms in solid solution with cerium is very much the same as in europium metal. This finding is supported by the lattice parameter measurements on these alloys at 298°K. The solubility limit of europium in cerium is found to be at 4.6 at.% europium at about 800°K.
Secondary-Electron-Emission Phase-Angle Distributions in High-Frequency Multipacting Discharges
Authors: Miller A. , Williams H. Bartel , Theimer O.
Published: April 2005

Numerical calculations of emission phase-angle distributions of electrons in a low-pressure, high-frequency (multipacting) electric discharge have been carried out on a Burroughs 220 digital computer. An integral equation for the phase-angle distribution is developed, and the numerical techniques used for its solution are outlined. The distribution of multipacting electrons with respect to the parameter v/v0, the ratio of impact velocity to emission velocity, has been calculated for several situations. These distributions show distinctive peaks which explain the success of the assumption v/v0=constant, used by previous workers, in predicting the breakdown region.
Ultrasonically Induced Switching in (80% Ni−20% Fe) Ferromagnetic Films
Authors: Hasty Turner E. , Penn T. C. , Einspruch Norman G.
Published: April 2005

Results of an experiment in which the magnetization vector of a thin (80%Ni−20%Fe) ferromagnetic film is switched from one quadrant to another by the simultaneous application of a magnetic field and an ultrasonic strain, both in the plane of the film, are reported. The observations of critical switching fields and critical strains are found to be in excellent agreement with a model based on Stoner—Wohlfarth theory.
Gas—Solid Suspensions at High Temperatures
Authors: Soo S. L.
Published: April 2005

The study consists of thermal electrification of a gas—solid suspension and its electrical conductivity at high temperatures. Possibilities of enhancing ionization and removal of electrons of a high temperature gas by solid particles were considered.
Electrical Resistivity of Thin Single-Crystal Gold Films
Authors: Chopra K. L. , Bobb L. C. , Francombe M. H.
Published: April 2005

Resistivities of evaporated or sputtered polycrystalline and epitaxially grown single-crystal gold films of thickness 100–1000 Å have been measured in situ during deposition. Single-crystal gold films have been grown epitaxially on cleaved mica by sputtering and, as indicated by electron diffraction studies, are atomically smooth over large areas. The resistivities of such films are very close to the bulk value for all thicknesses greater than a limiting thickness at which the film becomes continuous. Since the limiting thickness is appreciably lower than the mean free path for conduction electrons, this result is considered to be a consequence of the existence of specular (elastic) reflection of electrons from the film surface. Resistivities of polycrystalline films of thicknesses comparable to the electron mean free path are higher than the bulk value; and, for films grown on cold substrates, their dependence on thickness is in qualitative agreement with the theory of diffuse (inelastic) scattering of conduction electrons from the surface. For polycrystalline films deposited on heated substrates, the measured resistivity appears to be dominated chiefly by structural changes occurring during growth.
Effect of Cobalt Content on the Properties of Elongated Iron Particles
Authors: Luborsky Fred E.
Published: April 2005

The dependence of the magnetic properties of 200-Å-diam elongated particles of iron on cobalt alloy content is reported over the range from 0% to 90% cobalt. In particular, the compositional dependence of coercive force, corrected to zero packing density, is examined and compared to that expected theoretically for shape anisotropy. To a first approximation theory and experiment agree. Differences between theory and experiment in the compositional behavior of coercive force as well as temperature coefficient of coercive force and coercive force change with packing are attributed to a small crystal anisotropy contribution. However, the crystal anisotropies required do not agree with bulk measurements. Magnet energy was constant and at a maximum from 20 to 70% cobalt rather than only at 38% cobalt as predicted from considering shape anisotropy energy alone.
Temperature Dependency of Resistance of Thin Metal Films
Authors: Feldman Charles
Published: April 2005

The temperature dependency of resistance of vacuum deposited gold and platinum films between room temperature and 400° and 600° C, respectively, has been studied. Particular emphasis has been placed on the transition between thick, continuous films with positive temperature coefficients and thin, granular, or lacunary films with negative temperature coefficients. In addition to the low positive coefficients usually observed in this transition region, a minimum in the resistance vs temperature curve is observed. It is shown that the observed behavior can be attributed to a linear combination of the resistance of the individual grains or aggregates and the resistance due to gaps or potential barriers between the grains. The behavior in the transition region depends critically on the size of both the barriers and grains in the film.
Measurement of Thermal Conductivity of Electrical Conductors at High Temperatures
Authors: Cutler M. , Cheney G. T.
Published: April 2005

A new method for measuring the thermal conductivity of electrically conducting materials has been investigated that is particularly well suited for use at high temperatures. The sample has the shape of a narrow bridge between two larger masses of the same substance. The thermal conductivity is derived from the change in resistance which occurs when the narrow bridge is heated by passage of an electric current through it. The small size of the heated region makes it possible to neglect radiation at very high temperatures. It is not necessary to control the exact shape of the bridge, since geometric effects cancel out in the equations used to interpret the heating phenomena. Experimental measurements of the Lorentz ratio and thermal conductivity are reported for single-crystal molybdenum and tungsten at temperatures up to 1700°K. The application of this method to brittle semiconductor materials is also discussed.
Photoinduced Discharge Characteristics of Amorphous Selenium Plates
Authors: Li H. Tung , Regensburger Paul J.
Published: April 2005

A theoretical model is developed to account for the observed photoinduced discharge characteristics of amorphous selenium plates. This model takes into account not only the bulk trapping of the mobile carriers, but also the recombination of the photogenerated holes and electrons, the effect of which has been neglected in other earlier models. The selenium hole trapping range and recombination lifetime are determined from the present result to be 8×10−8 cm2/V and about 10−9 sec and are consistent with values obtained by using pulse techniques. This suggests that the present work has led to a new method for estimating these two parameters of a photoconductor.
Field-Effect Light Modulation in Germanium
Authors: Seraphin B. O. , Orton D. A.
Published: April 2005

Infrared light that is sent through a germanium prismatoid so that it is reflected several times internally, becomes modulated in intensity if the space-charge layers along the reflecting surfaces are changed by means of the field effect. The phase angle between the modulation signal and the field voltage changes by π when the surface is changed from n to p type, or vice versa, by change of the gaseous ambient. The modulation signal shows twice the frequency of the field voltage in the transition region between n and p type. This, together with other observations such as the waveform analysis of the modulation signal and the dependence of the modulation depth upon field voltage, indicates that the modulation is caused by free-carrier absorption in the space-charge layer, which follows roughly the master curve of the field-effect surface conductivity. The results are interpreted in terms of the field-effect mobility.
Magnetization of Manganese Ferrite
Authors: Butler Sidney R. , Buessem Wilhelm R.
Published: April 2005

The magnetization of manganese ferrite has been measured at low temperatures on samples prepared at several values of oxygen pressure and temperature within the stability field of the material. The systematic variation observed which extends from 4.55 to 4.88 Bohr magnetons is correlated with the degree of oxidation (determined by weight gain and lattice constant measurements) and possible changes occurring during quenching. Some suggestions are made concerning the wide spread in the Bohr magneton values previously reported in the literature.
Threshold Currents for Line Narrowing in GaAs Junction Diodes
Authors: Mayburg Sumner
Published: April 2005

The threshold currents required to produce narrowing of the emitted radiation from GaAs junctions can be estimated from the requirement that the quasi-Fermi levels lie near the band edges, as was first suggested by Bernard and Duraffourg. The observed threshold currents are obtained and the temperature dependence is deduced to be T32.
Space-Charge Polarization in Photoconducting Insulators
Authors: Harnik E. , Pratt B.
Published: April 2005

Quantitative analysis of space-charge polarization in photoconducting insulators, characterized by fast trapping, is extended to the case of an arbitrary distribution of carrier generation along the sample. It is shown that when the condition of fast trapping is properly formulated, the time dependence of the electric-field distribution and subsequently that of the photocurrent, is determined by a linear integrodifferential equation.
Experiments with Peltier Junctions Pulsed with High Transient Currents
Authors: Idnurm M. , Landecker K.
Published: April 2005

It was shown in a previous article by Landecker and Findlay that when transient currents are passed through a cooling Peltier junction the resulting transient temperature depends strongly on the current waveform. In particular, an extremal of the current as a function of time exists for which the resulting transient temperature is much lower than for any other current waveform. With the aid of an experimental method developed for the purpose, temperatures well below 100°K were in fact observed with bismuth telluride junctions. Since the occurrence of temperature transients producing such low junction temperatures is rather difficult to reconcile with some notions of solid-state theory, these results have been reexamined for current densities of up to ∼4000 A/cm2 using a modified technique that eliminates possible sources of systematic errors in the previous method. The results may be summarized as follows. Up to the highest current densities that could be produced a monotonic increase of the temperature drop with final current density was observed. The final temperature drops ranged from 205° to 120° measured from a reference temperature of ∼20°C (room temperature) depending on the efficiencies of the junctions. These efficiencies were difficult to predict from the performance of the junctions with stationary currents. For the highest currents and the very low transient temperatures an error of up to 150° may arise from imperfect heat transfer from the hot junctions to the water-cooled heat sinks unless special probes are provided to measure the Seebeck voltage. It is very likely that the accuracy of the measurements cannot be expected to be improved much further as long as grown crystalline n and p branches are used. It is hoped to produce sintered junctions of more suitable shape and greater mechanical strength for further experiments.
Explosive-Induced Pressures in Iron
Authors: Soper William G. , Potteiger Lester A.
Published: April 2005

The metallographic technique of C. S. Smith for determining peak pressures induced in iron by explosives is extended to include loading by oblique detonation waves. Wave interaction in an iron plate is analyzed to determine peak pressure as a function of detonation velocity and location of the hardness discontinuity in the plate. A series of oblique-wave experiments with the explosives composition B, C-3, C-4, and H-6 is described. Peak pressures computed by the metallographic method lie in the range 170–185 kbars.
Magnetic Properties of Lithium-Substituted Manganese Ferrite
Authors: McGuire T. R. , Ferebee F. S.
Published: April 2005

The result of substituting lithium for manganese in manganese ferrite is to lower the magnetic moment and raise the Curie temperature. The variation of magnetic moment with concentration is consistent with about 90% of the lithium going on B sites.
Fracture on (110) Planes in LiF
Authors: Wiederhorn S.
Published: April 2005

A study was made of (110) fracture in LiF using birefringence and etch-pit techniques. Fracture always occurred parallel to birefringence bands, and it is suggested that the stress of these bands aids (110) crack propagation. Surfaces formed by (110) fracture appear to be flat. If (100) steps are present, as suggested by Kuznetsov, they are less than 100 Å in height. By comparing etch-pit density data with birefringence data, it is estimated that only about one in twenty etch pits was due to single, unpaired dislocations. All the rest were probably caused by dipoles.
Faulting and Electroluminescence in Hexagonal ZnS Phosphors
Authors: Peters T. , Singer J. , Brophy V. A. , Birman J. L.
Published: April 2005

Controlled experiments have been conducted to isolate the processing parameters which produce bright electroluminescence in hexagonal ZnS:Cu, Cl phosphors. Crystal structure, in particular, was studied as it is affected by the mechanical, thermal, and chemical treatments of this processing. The correlation between electroluminescent brightness and stacking disorder which has often been suggested has been more quantitatively established. It was possible only partially to separate the effects of the entry of activator (Cu) from those of faulting upon electroluminescence. It was found that these two phenomena are intimately related in their importance for high brightness.

The nature and extent of the disorder has been investigated by precision x-ray diffractometry of the powders and by single-crystal x-ray diagrams of individual granules from them. Each granule has been found to be heterogeneous to xrays so that the analysis of the powder patterns is not straightforward. Much, or most of the disorder is obscured in the background of powder patterns and shows itself clearly only on single-crystal diagrams. The latter have been analyzed according to Jagodzinski's model based on two independent fault parameters; the fits obtained with this model between calculated and observed x-ray scattering are impaired by heterogeneity. The analysis discloses that the disorder in the homogeneously scattering-faulted regions may be an order of magnitude larger than indicated by the line breadth of the parent phase, which indicate faulting frequencies seldom exceeding 3%. Coherence in both the transformed and residual parent phase is favored by faulting in the presence of activator during the processing which produces bright EL. This coherence is lacking, even when faulting is extensive, if the disorder occurs without activator; under such conditions EL is practically not observed.

Conclusions reached in the past about the effect of structure upon EL, and also upon birefringence in ZnS phorphors, should be re-examined for the validity of the x-ray diffraction work on which they may have been based, inasmuch as in the course of the present work it has been shown that high precision diffractometry and single granule diagrams are needed to obtain an adequate picture of the disorder. Film diffraction may be entirely misleading.
X-Ray Studies of Epitaxial Copper Electrocrystallization
Authors: Lighty P. E. , Shanefield D. , Weissmann S. , Shrier A.
Published: April 2005

With the use of x-ray diffraction and etch-pit techniques, the imperfections in electrodeposited copper single crystals were compared to corresponding substrate imperfections. Areas of local polycrystallinity in the deposit were found to be associated with areas of misorientation in the substrate. The deposit perfection is influenced by the interaction of both dislocations and impurities in the substrate. With special purification of the electrodeposition solution, a deposit could be produced with a degree of perfection higher than that of the substrate.
Pressure Dependence of the Creep of Lead
Authors: DeVries K. L. , Baker G. S. , Gibbs P.
Published: April 2005

Apparatus is described for maintaining hydrostatic environment, 1 in. in diameter by 4 in. long, with 8 to 12 electrical leads, up to 20-kbar pressure and various temperatures. Bending creep of 99.999+% lead is reported with an activation volume of about 21×10−24 cm3, essentially independent of temperature between 0° and 57°C. Evidence for recrystallization is given.
Effect of Pressure on Creep in Tin
Authors: DeVries K. L. , Baker G. S. , Gibbs P.
Published: April 2005

Bending creep of tin is reported with an activation volume of approximately 8.5×10−24 cm3, essentially independent of temperature between 0° and 57°C, and pressures to 8 kbar. The pressure dependence of the output of resistance-type strain gauges is given.
Work Function and Thermal Desorption in the System Thorium-on-Rhenium
Authors: Anderson J. , Danforth W. E. , Williams A. J.
Published: April 2005

This investigation consists of two different but related parts.

1. The thermionic properties of rhenium and rhenium with an adsorbed layer of thorium atoms, were investigated. The Richardson constants for rhenium were found to be φ=4.85 eV, A=66 A per cm2-deg2. The work function decreases with increasing thorium coverage σ to a minimum of 3.15 eV at σ=4.2×1014 atoms per sq cm then rises to a constant value of 3.3 eV at σ=8×1014 atoms per sq cm. A comparison with the system tungsten—thorium shows that: (a) φmin occurs at the same surface density in both cases, (b) φconst is attained at the same surface density in both cases, and this density is that of the atoms in a (100) plane of thorium metal, and (c) the values of φconst are equal and different from that of bulk thorium by only 0.1 eV.

On the basis of these regularities a model is proposed to explain the variation of φ with σ.

2. The thermal desorption of the adsorbed atoms was studied at temperatures between 2203° and 2468°K. At low coverage the desorption rate per atom η0, was found to be constant with coverage, and to obey the relation η0=CT exp (-ε/kT) with C=4×1010 sec−1 deg−1 and ε=8.30 eV. The desorption rate increased for coverages between 0.05 and 0.5 monolayer and this increase agreed well with the predictions of a theory based on interactions among the adsorbed atoms.
Heat-Transfer Intensity from Induction Plasma Flames and Oxy-Hydrogen Flames
Authors: Reed Thomas B.
Published: April 2005

The heat transfer of flames generated in the induction plasma torch was measured with a water-cooled copper split-surface probe moved with respect to the flame. The resultant data were inverted mathematically to give the radial distribution of heat-transfer intensity q.

The distribution of q was measured for plasma flames as a function of distance from the nozzle and gas composition, using argon and mixtures of argon with oxygen or helium. For comparison, q was also measured for two oxy-hydrogen flames. The peak q for the various flames ranged from 56 to 145 W/cm2, with total heat transfer ranging from 0.64 to 4.21 kW.
Gradients in Mercury—Rare-Gas Discharges
Authors: Walsh P. J. , Manning G. W. , Larson D. A.
Published: April 2005

Mercury—rare-gas discharges at low mercury pressures and moderate rare-gas pressures form one of the simplest mixed-gas systems. The mercury supplies the ionization while the rare gas controls particle motions. The product ER is expected to depend upon paR, pmR, I/Rn. E is the positive column gradient, R the tube radius, pm and pa the mercury and rare-gas pressures, respectively, and n is expected to vary in the vicinity of 1 or 2. The quantity I/Rn is a sensitive indicator of any processes in the discharge which are not linear in the electron density. It is important in single-component discharges also. DC gradient measurements were made in mercury—argon discharges and verify the expected behavior. The ranges covered were 1.0 to 2.1 in., 1.0 to 75 μ, 0.7 to 35 mm, and 0.1 to 3.0 A, respectively, for R, pm, pa, and I, respectively. The behavior of n is partly explained by two-stage ionization involving resonance atoms whose lifetimes are governed by the imprisonment of resonance radiation. It is also shown how to reduce the gradient measurements in one mercury—rare-gas combination to those in another rare-gas combination. Comparison of mercury—argon and mercury—krypton gradients on this basis indicate that the average electron collision cross section in krypton is 1.4 times that in argon for energies near one electron volt.
Changes in Electron Concentration of Donor-Doped GaAs Crystals Caused by Annealing
Authors: Fuller C. S. , Wolfstirn K. B.
Published: April 2005

GaAs doped with ∼1019 cm−3 Se or Te shows reversible temperature-dependent changes in electron (donor) concentration over the temperature range 650 to 1100°C. Crystals containing between 2×1018 cm−3 to approximately 1019 cm−3 donors conform to the same equilibrium curve with an enthalpy of ∼0.5 eV. The behavior is that expected for a solubility equilibrium. Evidence against an equilibrium involving donor precipitation is presented, and the suggestion that the donors may interact to form molecules is discussed.
Visual Observation of Piezoelectric Modes
Authors: DeMaria A. J. , Barnard G.
Published: April 2005

The rotation of the optical index ellipsoid of piezoelectric crystals by an electric field has been widely used for the modulation of light. In particular, KDP and ADP crystals have found extensive use because of their large electro-optical (Pockel) effect; whereas, quartz crystals have found no application for this purpose because of their low Pockel effect. This paper reports experiments in which the rotation of the index ellipsoid of a quartz crystal by the crystal's piezoelectric resonant modes has been used: (1) to modulate in amplitude a laser beam at a fixed frequency and (2) to trace the piezoelectric modes by mean of an X-Y plotter.
A Reanalysis of Short-Range Order in Cu3Au
Authors: Walker C. B. , Keating D. T.
Published: April 2005

Cowley's measurements of the short-range order parameters αi in Cu3Au at T=405°C have been reevaluated taking into account the effects of thermal vibrations and static displacements due to differing atomic sizes. The separate corrections for the thermal vibrations and the first-neighbor atomic size factor are found to be quite large, demonstrating their importance in the usual experiments. When combined, the corrections in this case largely cancel, and only the values of α1 and α3 are appreciably changed. The corrected values are: α1=−0.113, α2=+0.185, α3=−0.009, α4=+0.082, and α5=−0.058.
Self-Diffusion in Polycrystalline Yttrium Oxide
Authors: Berard Michael F. , Wilder D. R.
Published: April 2005

The self-diffusion coefficient of yttrium in polycrystalline yttrium oxide determined in the temperature range 1400° to 1800°C is D=2.41×10−4 exp(−43 900/RT) cm2/sec.
Plastic Deformation in Magnesium Oxide Crystals Subjected to Rolling-Contact Stresses
Authors: Amateau M. F. , Spretnak J. W.
Published: April 2005

Magnesium oxide single crystals were subjected to rolling-contact loads, in the range from 130 000-psi to 173 000-psi Hertz stress, by rolling a ⅛-in. ball on a (001) plane in the [010] direction. The resulting plastic deformation indicated that the stress distribution is not very different than that predicted for isotropic, elastic media. Slip occurred predominantly on the glide planes, which coincided with the planes of maximum shear stress. Plastic deformation was caused by the operation of dislocation sources beneath the surface near the region of the calculated maximum shear stress. The depth of penetration and the number of slip lines were greater on those {110}45 planes which intersected the rolling surface parallel rather than normal to the rolling direction.
Infrared Spectra of Polyethylene Crystals
Authors: Brown R. G.
Published: April 2005

The infrared absorption spectrum of polyethylene crystals grown from solution was investigated. Intensities of bands, attributed to defects, in the region 1250–1400 cm−1 were observed to change with heat treatment, first decreasing and then increasing as the temperature of the treatment was increased in the range 120°–135°C. This observation is interpreted in terms of reduction of the number of folds accompanied by introduction of a different type of defect. The doublet at 720–731 cm−1 was monitored during the process of refolding at T≈130°C. A vestige of the high-frequency component was observed at all times, indicating the persistence of space-group symmetry. The suggestion of morphological similarity of polyethylene crystallized from solution and from the melt is supported by the similarity of their spectra. Two new weak bands at 692 and 1243 cm−1 were observed in the spectra of specimens cooled with liquid nitrogen. The frequency 1243 cm−1 is nearly equal to that predicted for a CH2 twisting mode which is inactive under selection rules for an isolated molecule.
Thermal Conductivity Measurements of Silicon from 680° to 1000°K
Authors: Morris Robert G. , Martin Joel J.
Published: April 2005

Series comparative measurements of the thermal conductivity K of single-crystal silicon have been extended to 1000°K. The results show that K remains nearly linear in T−1 to 1000°K and has a value of 0.29±0.06 W/cm C° at this temperature. This temperature dependence indicates the conduction is predominantly by the lattice vibrations and is limited by phonon-phonon scattering.
Electron-Beam Probing of a Penning Discharge
Authors: Dow D. G.
Published: April 2005

An electron beam probe has been used to study the distribution of electric fields within the cold-cathode Penning discharge. Three basically different potential distributions have been observed, in addition to the high pressure mode, which could not be studied with this technique. At the lowest pressures, the potential is roughly parabolic. As the pressure increases, a region develops in the center of the discharge, in which there is no electric field, that is, the potential profile is flat. Upon further increase in pressure, this central portion enlarges until it fills the majority of the discharge. At a pressure in the vicinity of 10−4 mm Hg the mode abruptly changes to one in which there is very little electric field throughout the discharge, although there are reasons to suspect a narrow region of high electric field near the anode. At still higher pressures (about 10−3 mm Hg) there is another abrupt change into the high pressure mode which acts essentially like a magnetically confined glow discharge.

Due to instrumentation difficulties, and end effects of considerable magnitude, it was not possible to measure numerical values for the electric field and potential, but their qualitative behavior has been plotted over a range of pressure, voltage, and magnetic field which is characteristic of the device.