bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Electrical Potentials in Supersonic Nozzles
Authors: Vaišnys J. Rimas
Published: January 2005

Several possible mechanisms for generation of high electrical potentials in supersonic nozzles are examined. It is suggested that charge transfer between condensate particles and the probe, due to a contact potential, occurs during particle—probe collisions. A high electrical-probe potential develops as the kinetic energy of the charged particles in the gas flow is converted to electrical energy. This conversion is possible because the particles are massive and have a low mobility. It is suggested that particle mobility and probe voltage—current measurements can yield size and energy information about the condensate particles.
Effect of Pressure on the Electrical Properties of Bismuth
Authors: Vaišnys J. Rimas , Kirk Robert S.
Published: January 2005

The magnetoresistance, Hall effect, and electrical conductivity of bismuth have been investigated to 90 kbar. In phase I, the application of pressure decreases the number of carriers; pressure increases the hole mobility so that both electrons and holes are approximately equally mobile just before the I–II transformation occurs. These observations may be explained by an upward shift of the light carrier bands relative to the heavy carrier bands. The magnetoresistance and Hall coefficients indicate simple metallic behavior for phases II, III, and IV.
Defect Centers in GaAs Produced by Cu Diffusion
Authors: Fuller C. S. , Wolfstirn K. B. , Allison H. W.
Published: January 2005

Evidence for defect centers having an ionization energy at Ev+0.10 eV in melt-grown GaAs is given based on: (1) Hall-effect measurements on Cu-diffused crystals. (2) Residual 64Cu left in GaAs after extraction by indium. (3) Decrease in electron concentration of donor-doped crystals after annealing. The failure to observe the defect level in photoluminescence is discussed. The results suggest that Ga vacancies are present in clusters in melt-grown GaAs crystals.
Ion-Current and Schottky Effects in Thermionic Diodes
Authors: Hansen L. K.
Published: January 2005

An experimental and theoretical study is made of current nonsaturation phenomena in cesium vapor, thermionic diodes. It is shown that ion flow from the plasma to the emitter electrode produces a significant nonsaturation effect. It is also shown that this ion current produces a high-sheath field at the emitter which accentuates the nonsaturation through the Schottky and anomalous Schottky effects. These effects are incorporated into an analysis of diode behavior. It is shown that the expected diode behavior due to ion-current and Schottky effects is consistent with available experimental data.
Use of LEED Apparatus for the Detection and Identification of Surface Contaminants
Authors: Weber R. E. , Peria W. T.
Published: January 2005

A low-energy electron diffraction (LEED) system has been used to study the energy spectra of Auger electrons from clean and alkali-covered Ge and Si surfaces. Auger bands characteristic of the substrates were observed for the clean surfaces and the deposition of submonolayer coverages of K and Cs introduced new bands characteristic of the respective alkali. It is shown that a surface impurity in a quantity as small as 0.1 monolayer can be detected and identified by this measurement.
Phase-Matched Second-Harmonic Generation in Biaxial Crystals
Authors: Hobden M. V.
Published: January 2005

The allowed directions for phase-matched second-harmonic generation in acentric biaxial crystals are obtained by considering the intersections of the index surfaces at the fundamental and harmonic frequencies; the topology of these intersections is determined by the principal refractive indices. There are thirteen distinguishable cases for optically well-behaved biaxial crystals and the phase-matching directions for them are shown as loci on the stereographic projection. Phase-matching that is insensitive to small changes in the direction of propagation is possible when some principal refractive indices are equal; the mismatch of the wave vectors is given for deviations from the phase-matching direction in such cases. The disposition of the principal axes of the optical indicatrix and the symmetry of the point groups C2v, D2, Cs, C2, and C1 are examined to find those situations which have a nonzero element in the second-order polarizability tensor that will give second-harmonic generation.

Phase-matched second-harmonic generation experiments in the biaxial crystals dipotassium tartrate, lithium sulfate and ammonium oxalate demonstrate some of the possible phase-matching situations.
Radiation due to a Dipole Over a Moving Medium
Authors: Pyati V. P.
Published: January 2005

The extension of Sommerfield's problem to a moving semi-infinite lossless medium is considered in this paper. The analysis is limited to the determination of the space wave in the far zone. This is the geometrical optics solution of the problem and is carried out simply by utilizing the results of the plane-wave reflection—refraction problem obtained in a previous paper. The study includes both the vertical and the horizontal dipoles. As expected, the motion of the medium does not significantly affect the radiation pattern unless the velocity is comparable with that of light.
Measurement of Electrical Anisotropy of Clay-like Materials
Authors: Mousseau R. J. , Trump R. P.
Published: January 2005

A six-electrode cell measures both a horizontal and vertical resistivity on a single deformable sample under compacting load. The similar effects of anisotropy and sample thickness on the ratio of two voltages in the cell allow a determination of the anisotropy coefficient. The geometric mean resistivity is obtained using a cell constant appropriate to the electrically determined product of the anisotropy coefficient and sample thickness. Clay and shale materials have ratios of vertical to horizontal resistivity of from near unity to 25 to 1.
New Electroluminescent Spectrum in ZnTe resulting from Oxygen Incorporation
Authors: Kennedy D. I. , Russ M. J.
Published: January 2005

Electroluminescence was observed in ZnTe devices fabricated from crystals in which oxygen was incorporated. Main emission peaks were located at 6960 Å at 293°K and 6580 Å at 77°K, and external quantum efficiencies of 10−3–10−4 were obtained at room temperature. The emission from these devices is considered to result from recombinations taking place at oxygen centers which appear to be located approximately 0.4 eV from the band edge. Improvements in the emission properties of these devices over similar diodes fabricated from undoped material are described.
Superconductivity of Niobium Thin Films Deposited by dc Diode Sputtering
Authors: Sosniak J. , Hull G. W.
Published: January 2005

Niobium films with superconducting transition temperatures between 8.2° and 9.1°K have been deposited by dc diode sputtering. The results are shown to be due to the reduction of the film impurity content by extensive presputtering and high substrate temperatures.
Wall Streaming in Ferromagnetic Thin Films
Authors: Stein K. U. , Feldtkeller E.
Published: January 2005

In nickel-iron films thicker than about 100 nm (1000 Å), fast-rising field pulses along the hard anisotropy axis lead to a new kind of wall displacement called ``wall streaming,'' which does not require any field component parallel to the wall necessary for all other wall motion processes. The walls are displaced with a very regular wall step width per pulse which strongly depends on the strength of the pulse field and on the pulse rise and fall times, but not on the pulse duration. The direction of wall motion reverses if the pulse polarity is reversed. During the application of a sequence of uniform pulses, the direction of wall motion may also reverse, beginning at one end of the wall, with a reversing line (interpreted as being a Néel line moving along the wall. The phenomenon is explained as a consequence of the gyromagnetic behavior of the magnetization in the Bloch walls. A detailed theory is presented, in which the intrinsic spin damping and the film inhomogeneity (characterizable by the coercivity) are to be taken into account. Wall streaming may contribute to a destruction of the information stored in magnetic films thicker than 100 nm (e.g., in plated-wire memories) as soon as fast-rising (tr ≲20 nsec) pulses are applied.
Effects of Annealing on the Photoelectronic Properties of ZnS Crystals
Authors: Blount George H. , Sanderson Arthur C. , Bube Richard H.
Published: January 2005

Annealing in zinc or sulfur vapor introduces major changes in the photoelectronic properties of ZnS single crystals. Insulating insensitive crystals of ZnS were annealed for various periods of time from 20 min to 6 days at 891°C in a saturated zinc vapor. Annealing increases the dark conductivity by at least eight orders of magnitude, the photosensitivity by over three orders of magnitude, and markedly affects photoluminescence emission. The effects of annealing in zinc are reversible by subsequent annealing in sulfur vapor. Optical quenching data show that the high photosensitivity in the zinc-annealed crystals is associated with sensitizing centers lying 1.2 eV above the valence band with an electron-capture cross section of about 10−21 cm2. The photosensitivity decreases rapidly with decreasing temperature below 200°K, whether excitation is by intrinsic ultraviolet or extrinsic infrared, because of the effects of a high density of shallow electron traps. The principle effect of annealing appears to be in the variation of the Fermi-level position in the crystal.
Electrical Phenomenon Occurring during Freezing of Dilute Aqueous Solutions
Authors: Anantha N. G. , Chalmers B.
Published: January 2005

The electrical effects occurring during freezing of dilute aqueous solutions have been studied using NH4OH and NH4Cl solutions. The freezing potentials depend on the concentration of the solution and the rate of growth of the solid phase. This effect is an impurity effect and does not appear in pure material. The phenomenon can be explained by a model in which the impurity rejected by the growing solid into the solution ionizes, one kind of ion being adsorbed on the solid surface at the interface and the other kind diffusing into the liquid. The impurity ion adsorbed on the surface moves with the surface and is not incorporated into the solid phase. This effect is confined to a narrow range of concentration of the solutions.
Mobility of Holes and Interaction between Acceptor Defects in ZnTe
Authors: Aven M.
Published: January 2005

Electrical transport studies in p-type ZnTe have confirmed that in the temperature range of about 80° to 500°K the hole mobility is principally limited by LO phonon scattering. An effective mass ratio of 0.6 gives the best fit to the experimental data. The highest mobility, 6500 cm2/V·sec at 35°K, was observed in a crystal with an active defect center concentration of 2×1015 cm−3. The ionization energy of the first charge state of a native acceptor, believed to be a Zn vacancy, was found to be ≥0.057±0.002 eV. Besides acting as shallow acceptor defects in ZnTe, the elements Li, Na, and P were found to promote the incorporation of substantial concentrations of native defects. High concentrations of Li, under excess Zn firing conditions, were observed to lead to highly compensated, low-mobility material, suggestive of self-compensation of the Li dopant.
Photoluminescence, Photocurrent, and Phase-Transition Correlations in SrTiO3
Authors: Sihvonen Y. T.
Published: January 2005

Photoluminescence emanating from ``pure'' high resistivity SrTiO3 has been examined between 4000 and 13 000 Å as a function of temperature and 3650 Å irradiation. One strong narrow peak (7929 Å at 95°K; half-width ≤1 Å) and 9 associated peaks (7852, 8005, 8051, 8098, 8280, 8304, 8469, 8574, 8726 Å), each of which exhibit maximum intensity at 35° and 95°K, which are within the temperature ranges associated with the ferroelectric-paraelectric transition, and the tetragonal-cubic transition, respectively. As this emission extinguishes below 35°K, an asymmetric structureless broadband emission begins, which extends from ≈4200–≈8000 Å, and peaks near 5000 Å. Concurrent photocurrent measurements show: a maximum at 105°K and a minimum at 35°K; the existence of extensive trapping effects, including long-duration (hours to days) dark-current relaxation, a field-induced persistent internal polarization (due to spacial separation of trapped electrons and holes), and an interaction between irradiation and ferroelectric hysteresis. Sublinear responses exist common to the photoluminescence peaks and photocurrents at various temperatures, viz. response ∝ Jβ(T) where ½<β(T)<1. The behavior observed is in part interpretable on the basis of recombination processes via multiple defects.
Electron-Cyclotron Resonance Heating of Alkali Plasmas
Authors: Levine A. M. , Kuckes A. F. , Motley R. W.
Published: January 2005

A method has been developed for heating the electrons in a thermally generated alkali plasma by the resonant absorption of electromagnetic waves at the electron-cyclotron frequency. The electron temperature was increased from 0.2 eV to ∼1.0 eV with the application of ∼1 W of power at a frequency of 10 kMHz. Excellent consistency has been found between diamagnetic measurements of plasma pressure, microwave determinations of plasma density, and double-probe determinations of temperature. The observed temperature increases were in quantitative agreement with computations which consider the heat loss by thermal conduction.
Electron Tunneling between a Metal and a Semiconductor: Characteristics of Al-Al2O3-SnTe and −GeTe Junctions
Authors: Chang L. L. , Stiles P. J. , Esaki L.
Published: January 2005

The process of electron tunneling from a metal to a semiconductor through an insulating layer is considered. Theoretical current-voltage expressions have been obtained, in particular, for the case when the semiconductor is degenerate p type and the conduction band of the insulator provides the dominant tunneling barrier. The existence of an energy gap and a relatively small Fermi energy in the semiconductor makes the current highly asymmetrical with respect to the polarity of the applied voltage. Experimentally, junctions of Al-Al2O3-SnTe and −GeTe have been fabricated and their I-V characteristics measured at 4.2°K. Good agreement is observed between the theoretical and experimental current behavior, from which energy parameters of the semiconductors and the barrier relations of the junctions have been obtained.
Scattering of Light by Ringed Spherulites Containing Biaxial Crystals
Authors: Clough S. B. , Stein R. S.
Published: January 2005

The theory of the scattering of light by ringed two-dimensional spherulites containing biaxial crystals oriented at an arbitrary angle to the radius and helicoidally rotating about the radius is developed. The presence of intensity maxima at various scattering angles is predicted in patterns which are similar to those which are experimentally observed.
Chemical Reversibility and Solar Excitation Rates of the Nitrosyl Chloride Photodissociative Laser
Authors: Giuliano C. R. , Hess L. D.
Published: January 2005

Chemical reversibility of the nitrosyl chloride photodissociative laser is achieved by addition of a large excess of chlorine which also serves as an efficient buffer gas, and thereby eliminates the need for helium. Consideration is given to the prospect of utilizing this system as a means of converting solar radiation to monochromatic coherent emission.
Effect of Hydrostatic Pressure on p-n Junction Characteristics and the Pressure Variation of the Band Gap
Authors: Jayaraman A. , Sikorski M. E. , Irvin J. C. , Yates G. H.
Published: January 2005

The effect of hydrostatic pressure on p-n junctions of Si and GaAs in which both ideal and generation-recombination currents were present has been investigated. It is shown that the pressure coefficients of the energy gap can be obtained directly from the pressure-induced shifts in the forward-bias voltage, measured at a constant total junction current. Presently determined pressure coefficients of −1.5±0.005×10−3 eV/kbar for Si and 10.9±0.1×103 eV/kbar for GaAs are in good agreement with values obtained for Si and GaAs by other methods. In the case of GaAs, the pressure-induced shift in the forward-bias voltage reverses sign when the conduction-band minimum shifts (to the [100] valleys) at high pressure.

The effect of pressure on the reverse breakdown voltage for Si junctions has also been determined. The results seem to offer some support to the theory of Hauser and Wortman.
Temperature Dependence of the Ferromagnetic Resonance Linewidth of Europium Sulfide
Authors: Franzblau M. C. , Everett G. E. , Lawson A. W.
Published: January 2005

The temperature dependence of the ferromagnetic resonance linewidth of highly polished single-crystal spheres of EuS was measured in the range from 2.2° to 30°K, using standard microwave techniques at a frequency of 22.65 GHz. The linewidth increases from ∼5 Oe at 2.2°K to ∼400 Oe at the Curie point, and continues to increase in the paramagnetic range to a value of 1000 Oe at 78°K. The linewidth varies linearly with reciprocal magnetization from 2.2° to 18°K, as predicted by the Landau-Lifshitz equation and can be characterized by a temperature-independent microphysical damping constant, λ, equal to 1.9±0.09×108 rad/sec within this temperature range.
Comparison of Langmuir Probe and Microwave Diagnostic Techniques
Authors: Graf K. A. , De Leeuw J. H.
Published: January 2005

Electron densities have been measured in the subsonic portion of a free-expansion argon jet by microwave and Langmuir-probe methods. Microwave phase-shift measurements were made with an interferometer in such a way that the spatial variation of electron density could be determined. The data were analyzed with a ray-tracing technique.

Langmuir-probe measurements were made with cylindrical and flat probes under essentially collision-free conditions, and over a range of probe radius to Debye length ratios of about 10–50. Both electron and ion collection were measured and analyzed. Three methods of analyzing the electron-current part of the characteristic were compared. It was found that one method gave values two or three times higher than another method. The discrepancy was due to the failure of the experimental Langmuir-probe characteristic to follow the theoretical one in the vicinity of plasma potential: the so-called ``knee'' of the curve. This difficulty has been overcome by analyzing the data with the aid of theoretical particle-collection curves.
Anomalous Heat Capacity of TiNi
Authors: Berman H. A. , West E. D. , Rozner A. G.
Published: January 2005

Calorimetric measurements on a sample of TiNi (50 at.%) show that the heat-capacity maximum at approximately 87°C represents a higher-order transition. The transition was shifted to lower temperatures each time the material was heated through the transition from slightly above room temperature to about 150°–200°C. The transition enthalpy decreased in three such cycles from 4150 to 3375 J/mole TiNi.
Energy Relations for Plane Waves Reflected from Moving Media
Authors: Daly P. , Gruenberg Harry
Published: January 2005

When a plane wave is obliquely incident from vacuum on a semi-infinite moving medium, the energy flow carried by the incident wave, is in general, not carried away by the reflected and transmitted waves. This is only the case when the medium velocity is parallel to its vacuum interface. Otherwise there is a net inflow or outflow of electromagnetic energy, which can be accounted for by the change of stored energy in the system, and the work done by the mechanical forces acting on the medium. A detailed energy balance is drawn up for two different media moving normal to their vacuum interfaces: (a) a moving conductor and (b) a moving dielectric.
A Theoretical Study of the Effect of Elastic Strain on the Electrical Resistance of Thin Metal Films
Authors: Meiksin Z. H. , Hudzinski R. A.
Published: January 2005

Theoretical equations for the strain coefficient of resistance in metallic thin films are derived. The films considered range from ultrathin, discontinuous films of theoretical average thickness of less than an angstrom to relatively thick films of about 6000 Å which exhibit bulk material properties. The films are classified into five thickness ranges according to the predominating conduction mechanisms. It is found that ultrathin films exhibit strain sensitivity of two orders of magnitude higher than the bulk metal. The sensitivity reduces with increasing average film thickness to a minimum value which occurs in the transition region in which the film conduction properties change from those of a semiconductor to those of a metal. With further increase in thickness the bulk value of sensitivity is approached. The theory is compared with experimental studies and possible misinterpretations in previous studies are discussed.
Stimulated Emission from Nd3+ and Yb3+ in Noncubic Sites of Neodymium- and Ytterbium-Doped CaF2
Authors: Robinson M. , Asawa C. K.
Published: January 2005

Three new laser lines are reported: Two lines, at 1.0448 and 1.0661 μ, occur for a CaF2 crystal which is heavily doped with NdF3; a line at 1.0336 μ occurs for a CaF2 crystal containing NdF3 and YbF3. Details of the absorption and fluorescence spectra indicate that the laser oscillations arise from Nd3+ ions at noncubic sites in the first crystal and from Yb3+ ions in the second crystal. The growth techniques are summarized; the special growth procedures minimize the oxygen content, thereby reducing the number of impurities in sites for Nd3+ and Yb3+.
Change in Field Intensification Factor β of an Electrode Projection (Whisker) at Short Gap Lengths
Authors: Miller H. Craig
Published: January 2005

The field intensification factor, β, was found theoretically to be a function of gap length, projection height, and projection tip radius. The electrode projection was approximated by a grounded plane and separate grounded sphere, the opposing electrode by a charged plane. The results may be used to find the height and tip radius of a projection in a small gap by measuring β as a function of gap length.
Single-Crystal Elastic Properties of Tungsten from 24° to 1800°C
Authors: Lowrie Robert , Gonas A. M.
Published: January 2005

The velocities of ultrasonic shear and compressional waves in tungsten crystals have been measured in several directions and as functions of temperature to 1800°C. Adiabatic crystal elastic stiffnesses have been calculated from these velocities as follows: C11=5.2349×1012−4.5967×108T−5.467×104T2±0.25% dyn·cm−2C44=1.6028×1012−1.0320×108T−2.054×104T2±0.25% dyn·cm−2CN=5.2480×1012−3.5005×108T−3.163×104T2±0.25% dyn·cm−2C12=2.0445×1012−0.3403×108T+3.249×104T2±2.3% dyn·cm−2C′=1.5952×102 −2.1282×108T−4.358×104T2±1.8% dyn·cm−2.

Values for the elastic constants of random, polycrystalline tungsten were calculated from these crystal stiffnesses. They agree well with values determined on polycrystalline tungsten as functions of temperature.
Controlled Crystalline Orientation of Sputtered Ferromagnetic Films on Amorphous Substrates
Authors: Larson H. W. , Walker G. A.
Published: January 2005

The effects of thermionic sputtering parameters on crystalline orientation and coercive force of magnetic films are discussed in this paper. By controlling the crystalline orientation within the film it is possible to produce films with a coercive-force range from 0.9 Oe to 35.8 Oe. The crystalline orientation is controlled by the magnetic field, the electric field, and the substrate position within the apparatus. All of the films were prepared on substrates which were not exposed to the sputtered material until the target had the adsorbed gases removed.

The texture of the films is described by means of several x-ray photographs taken on a specially designed Laue camera, capable of giving a pattern from films as thin as 100 Å.
Studies of Cataphoresis and Electrophoresis—Some New Effects
Authors: Kenty Carl
Published: January 2005

A study is made of the rate of transport of Hg in a uniform positive column in a mixture of a rare gas and Hg vapor. In one case, the phenomenon of retrograde cataphoresis is encountered, that of Xe+Hg at currents above 1 A, in which the Hg is carried to the anode end of the tube. In all other cases, the Hg is transported to the cathode end.

A pulsating discharge is described in which the color changes from the red of Ne to the blue-white of Hg and back again within a period of 1–2 sec. The boundary between the two colors travels along as a wave motion. This phenomenon is related to the properties of the tube walls and the nature of the ions striking them.

When an ac discharge is passed through a cataphoretic mixture, the trace gas of lower ionizing potential is urged from the ends toward the center of the tube, e.g., Hg in Ar, Ne and Kr, but from the center to the ends in He+Hg. With a trace of Ar in He, the Ar is urged toward the center of the lamp. With Xe+Hg, the Hg may go either to the center or to the ends, depending upon conditions. The phenomenon is believed to be due to traveling striations which start out from the anode and progress only part way toward the cathode. Such a striated discharge pumps Hg faster than a steady discharge in the case of Ar, Kr, and Ne, but apparently slower in the case of He.

Attempts to demonstrate electrophoretic effects in a straight sealed-off tube failed. However, the positive pressure effects are quite striking in a tube with an external return path.
Inertial-Electrostatic Confinement of Ionized Fusion Gases
Authors: Hirsch Robert L.
Published: January 2005

The nonmagnetic, inertial-electrostatic confinement of ionized gases in spherical geometry is discussed theoretically, and associated experiments are described. Assuming monoenergetic ion and electron distribution functions, the Poisson equation for bipolar currents is solved numerically. The results indicate spatially periodic solutions which respresent the alternate formation of virtual anodes and virtual cathodes. Particle pressures are found to vary approximately as the inverse square of the radius and extremely high electric fields are indicated. Near the center of the spherical cavity, there exists a high-density, high-energy region, which may be of controlled fusion interest.

The experimental apparatus consists of a hollow spherical cathode concentrically placed within a spherical anode on which six ion guns are located. Steady, reproducible operation up to −150 kV and 60 mA yields a copious neutron emission, a part of which originates from a luminous spherical region within the cathode. After crowbar of the main power supply, approximately 1016 particles are released from within the cathode. This number is significantly greater than the 1012−1014 ions/cm−3 calculated from the fusion rate. The difference is attributed to the formation of two or more virtual anodes. A bremsstrahlung collimation study indicates a spatially periodic emission pattern, suggesting the formation of at least two virtual anodes, the outer of which is about 2.5 cm in diameter. No instabilities have been observed.
Determination of the Pressure of the Barium I-II Transition with Single-Stage Piston-Cylinder Apparatus
Authors: Haygarth J. C. , Getting I. C. , Kennedy G. C.
Published: January 2005

The pressure of the barium I-II transition has been determined in a modified single-stage piston-cylinder apparatus to be 55.0±0.5 kbar at 22°C. Three barium samples of different purity were used and no significant variation of the transition pressure found. The temperature coefficient of the transition pressure is 0–0.015 kbar/°C near room temperature. The effect of the presence of dissolved hydrogen on the transition pressure is discussed.
Wavelength Identification of Ultrasoft X Rays by the Critical Angle of Total Reflection
Authors: Herglotz Heribert K.
Published: January 2005

If absorption in the reflector is low, ultrasoft x rays exhibit a well-defined critical angle of total reflection. Experiments with simple apparatus verify critical angles calculated for paraffin of θc≈4° for carbon radiation (λ=44.7 Å) and θc≈6° for boron radiation (λ=67.7 Å). Utilization of this concept in a low-resolution (10<λ/Δλ<20) instrument for the chemical analysis of carbon and boron by a paraffin reflector and of nitrogen, oxygen, and fluorine by a lithium fluoride mirror is suggested.
Heat Generated during Torsional Oscillations of Polymethylmethacrylate Tubes
Authors: Tauchert T. R. , Afzal S. M.
Published: January 2005

Experimental data on the heat generated during torsional oscillations of polymethylmethacrylate tubes are presented. Various factors which affect the internal heat generation, including the amplitude and frequency of oscillation and the ambient temperature are investigated. A comparison of the mechanical energy added to a specimen during a cycle of deformation and the resulting heat indicates that some energy is ``stored'' during the process. In addition to the detail of the response during a single cycle of deformation, the longtime response of the material to constant strain-amplitude oscillations is investigated. The data demonstrate that thermomechanical coupling effects can be extremely important.
Decay of High-Frequency Longitudinal Phonons
Authors: Klemens P. G.
Published: January 2005

The anharmonic decay of a high-frequency longitudinal elastic wave at low temperatures, such that ℏω> KT, is calculated by perturbation theory, using a Grüneisen parameter as measure of the anharmonicity. The attenuation at very low temperatures varies as the fifth power of frequency, and is small at frequencies below 1012 Hz.
Plasma Acceleration with Microwaves near Cyclotron Resonance
Authors: Kosmahl H. G. , Miller D. B. , Bethke G. W.
Published: January 2005

Acceleration of a microwave-energized plasma by expansion in a diverging magnetic field is studied. Results of a theoretical collisionless particle analysis are reviewed. An experimental accelerator is described and its pertinent conditions are considered. Measurements of plasma beam shape and potential are compared with the theoretical predictions. The conclusions are that, while some experimental characteristics (beam shape and potential profile) agree with theory, collisions in the experimental device prevent it from attaining operating conditions predicted by collisionless theory.
MOS Avalanche and Tunneling Effects in Silicon Surfaces
Authors: Goetzberger A. , Nicollian E. H.
Published: January 2005

Avalanche generation of minority carriers was studied under pulsed-field conditions in thermally oxidized silicon surfaces. In the doping range between 5×1016 and 1×1018 cm−3 avalanche breakdown voltages and fields are in agreement with step-junction results. For lower doping, breakdown voltages are below the expected values. Avalanche light-emission observations revealed this effect to be due to field concentration at the contact edges. In the higher doping range between 1018 and 1019 cm−3 minority carriers are produced by Zener tunneling. Band bending for tunneling is 1.1 V, independent of doping.
Recombination Processes following Impact Ionization by High-Field Domains in Gallium Arsenide
Authors: Southgate P. D.
Published: January 2005

When a field greater than that required to produce Gunn instabilities is applied to gallium arsenide containing free electrons in concentrations of 1017 cm−3 or more, excess current rather than current saturation is seen. Impact ionization due to high-field domains causes a substantial increase in carrier density. The processes involved in the generation and recombination of these excess carriers are analyzed here. Recombination occurs by competing radiative and nonradiative mechanisms, with long-term trapping also playing a role. Measurements of the time dependence of excess conductivity and recombination radiation, the spectral distribution of the radiation, and its intensity as a function of excess carrier concentration, allow the generation rate and recombination cross sections to be deduced. The generation rate is consistent with that expected from flat-topped domains. Cross sections for the capture of both holes and electrons by the recombination centers dominant under these conditions are of the order 10−17 cm2. The emitted radiation is strongly self-absorbed; correction for this factor shows that most of the original emission has energy greater than the bandgap. The direct recombination cross section is deduced to be near 5×10−18 cm2, which is in reasonable agreement with that derived from the van Roosbroeck-Shockley theory.
Effect of Carrier Heating on the Diffusion Currents in Space-Charge-Limited Current Flow
Authors: Stratton R. , Jones E. L.
Published: January 2005

The theory of hot electron diffusion is developed for the case of space-charge-limited current flow in insulators or weakly doped semiconductors. To compare the results of the calculation with experiments on silicon n+-π-n+ structures by Denda and Nicolet, a crude theory of the uniform-field hot-electron effect in n-type silicon is developed.
Electronic Theory of Adhesion
Authors: Derjaguin B. V. , Smilga V. P.
Published: January 2005

A consistent electronic theory of adhesion is developed relating to the contact of bodies of different nature.

The strength (as well as energy) of adhesion is calculated for the contact of crystal bodies (semiconductors, metals) as well as for the contact of amorphous bodies whose surface is saturated by donor and acceptor functional groups. The theory developed allows us to calculate the electrostatic component, when certain (experimentally determined) physiochemical characteristics of studied objects are known. The theory also determines the temperature dependence of the adhesion strength. The main inference is that cases of electrostatic component reading values of the order of 108−109 (dyn/cm2) are fairly realistic. There follows from the theory the role of surface conditions as the chief factor of high adhesion. The theory suggests the ways for conditioning the adhesion via chemical modification of the surfaces (sometimes also of the bulk) of contacting bodies, and indicates which characteristics of solid bodies are to be studied when investigating the adhesion.
Infrared Studies of Some Perovskite Fluorides. I. Fundamental Lattice Vibrations
Authors: Perry C. H. , Young E. F.
Published: January 2005

The reflectance spectra of the cubic fluoride perovskites KMgF3, KMnF3, KCoF3, KNiF3, RbMnF3, and mixed crystals of K (Mg0.8:Ni0.2) F3 and K (Mg0.5:Ni0.5) F3 have been measured from 4000−40 cm−1 at 300° and 85°K. The spectra of all crystals at both temperatures have been fitted by means of a classical dispersion analysis to yield the frequencies, oscillator strengths, and damping constants of the three ir active lattice vibrations. An assignment of the normal mode frequencies to particular vibrations has been made. The high- and low-frequency dielectric constants of these materials have been determined from the reflectance measurements. The isotropic polarizabilities of Mg2+, Mn2+, Co2+, Ni2+, and Rb+ have been calculated. The transverse effective charge at 300°K has been obtained in order to determine the strength of second-order dipole moments due to charge deformation during lattice vibrations.
Infrared Studies of Some Perovskite Fluorides. II. Multiphonon Spectra
Authors: Young E. F. , Perry C. H.
Published: January 2005

The transmission spectra of thin single-crystal samples of KMgF3, KMnF3, KCoF3, KNiF3, KZnF3, and K (Mg0.5:Ni0.5) F3 have been investigated from 2.5–400 μ (4000−25 cm−1) at 300° and 85°K. A large number of bands have been observed in each material and these have been interpreted in terms of multiphonon processes at critical points in the lattice dispersion curves. The average energies of the phonon branches at the edge of the Brillouin zone have been deduced from the observed infrared spectra.
Electromagnetic Pulse Propagation in Lossless, Inhomogeneous, Dispersive, Dielectric Media
Authors: Ott E.
Published: January 2005

This paper develops geometrical optics ray techniques for problems of transient electromagnetic wave propagation in inhomogeneous, lossless, dispersive, dielectric media. The method results in a series expansion of the fields about the wavefronts. The theory is applied to solve a few illustrative problems dealing with wave propagation in a cold isotropic plasma. Special attention is given to the fact that in all physical media the wavefronts must propagate at the speed of light in vacuum. This physical requirement does not seem to have been incorporated into the mathematical models used in previous works dealing with geometrical optics techniques for solving transient electromagnetic wave problems.
High-Temperature Thermal and Electrical Properties of GaSb-InSb Alloys
Authors: Kudman I. , Ekstrom L. , Seidel T.
Published: January 2005

The thermal conductivity, Seebeck coefficient, and electrical resistivity have been measured as a function of temperature for various impurity concentrations and alloy compositions. n-type alloys, doped with tellurium to give room-temperature resistivities of 0.7−2×10−3Ω·cm, provided the optimum figure of merit, which reached a maximum of 1.15×10−3 deg−1 at 600°K. This represents an improvement by over a factor of two above the best values for n-type Ge-Si alloys below 800°K. In contrast, the figure of merit for p-type alloys are generally inferior to that of Ge-Si alloys at all temperatures.
On the Conditions for Self-Locking of Modes in Lasers
Authors: Statz H.
Published: January 2005

Before self-locking of modes can be accomplished in a laser, all adjacent longitudinal modes must have the same frequency separation. It can be shown that the dispersion associated with the laser transition generally causes longitudinal modes to have slightly different frequency separations. For homogeneously broadened lines these differences are indeed very small, but for inhomogeneously broadened lines they become significant. An equidistant mode separation can be produced when the mode oscillations shift slightly in frequency and lock onto nonlinear polarization source terms produced by the interaction of three modes. The question as to whether mode locking is actually achieved depends upon the relative size of the required frequency shift and the amplitude of the nonlinear source terms. Among other variables, the nonlinear polarization is proportional to the fourth power of the dipole matrix element between the two states in question, and thus depends strongly on their radiative lifetime. For example, in Nd3+-doped glass the matrix element between the laser states is too small for locking, but a short-lifetime saturable absorber inserted into the cavity will produce self-locking.
Re-emission Coefficients of Si and SiO2 Films Deposited through rf and dc Sputtering
Authors: Jones R. E. , Standley C. L. , Maissel L. I.
Published: January 2005

Re-emission coefficients for SiO2 films and for Si films deposited through rf sputtering have been measured as a function of pressure and input power. Values for SiO2 were 0.86−0.30 and for Si 0.45−0.07. High re-emission coefficients correlated with negative potentials on the deposit surface, which, in turn, caused resputtering of the deposit by positive ions drawn from the glow discharge. The existence of additional mechanisms for re-emission was established for rf-sputtered silicon deposited at zero substrate bias. The re-emission coefficient of dc-sputtered silicon was found to have values comparable to those of rf sputtering.
Radiant Heat Transfer in Fibrous Thermal Insulation
Authors: Hager Nathaniel E. , Steere Robin C.
Published: January 2005

Expressions are derived for calculating radiant heat transfer rates in laminar arrays of high-emissivity fibers having diameters much larger than the wavelengths of the emitted radiation. New experimental results are given for a sample composed of 280-μ fibers, with the mean sample temperature near or below room temperature, so the dominant wavelengths of fiber emission are of the order of 10 μ. The data show general agreement with the theory, and establish clearly that the rate of radiant heat transfer is proportional to the cube of the mean absolute temperature of the sample. A brief review of published data suggests that the derived expressions also give correct functional dependence on insulation parameters for finer fibers having diameters equal to, or less than, the wavelengths of the emitted energy. But the absolute magnitude of the values reported for finer fibers is generally larger than that predicted by the large-diameter expression, and in some cases is larger by a whole order of magnitude. Reflection, diffraction, and fiber transparency effects are probable causes of the higher values. Since these effects are neglected in this analysis, it is suggested that the expressions given here may represent a lower limiting value for smaller-diameter fibers.
Coefficient of Expansion of GaAs, GaP, and Ga(As, P) Compounds from −62° to 200°C
Authors: Pierron E. D. , Parker D. L. , McNeely J. B.
Published: January 2005

Precise cell dimensions of GaAs, GaAs0.59P0.41, GaAs0.5P0.5, and GaP have been determined from x-ray powder diffraction patterns from −62° to 200°C. Within the temperature range investigated, the constant thermal coefficients of expansion are, respectively, 6.86×10−6, 7.81×10−6, 5.91×10−6, and 5.81×10−6°C−1. The cell dimension of pure GaP (impurity less than 3.0 ppm) is 5.4495±0.0001 Å at 24°C.
The Te-Rich Region of the Bi-Tl-Te System: Bi2Te3-Tl2Te3 and BiTlTe2-Te Sections
Authors: Chiang Ping-Wang , Gluck J. V.
Published: January 2005

Detailed studies have been carried out to define the phase relations in the Te-rich region of the Bi-Tl-Te system. Isopleths were constructed for the Bi2Te3-Tl2Te3 and BiTlTe2-Te sections, and a schematic diagram is suggested for the projections of the liquidus lines and the invariant planes. The phase behavior can be characterized by the cooling reactions: L+Bi2Te3→BiTlTe2+Te at 325°C, and L→Tl2Te3+BiTlTe2+Te at 223°C. No evidence was found to support the existence of the compound ``BiTlTe3'', as reported by Borisova et al.
Wave Excitation in Compressible Plasma and Equivalence Relations
Authors: Wu Yung-Kuang , Chu Chiao-Min
Published: January 2005

A general, unified solution of the wave excitation due to electric-current sources, magnetic-current sources, fluid-flux sources, and mechanical-body sources in a compressible plasma which may be anisotropic and inhomogeneous is presented. The Maxwell—Euler equations are reformulated through linear operator and generalized transform techniques into an equivalent matrix integral equation. The dispersion relation can be obtained from the kernel of the integral equation. When the medium is homogeneous, this integral equation has an ideal kernel and the explicit solution can be easily obtained. Equivalence relations between different types of sources are obtained from the forcing function of the integral equation, which can be employed to express the field excited by one type of source in terms of the field excited by another type of source. Generalized telegraphist's equations are also derived in due course.

Some dispersion curves, and asymptotic solutions for the radiation field from a point current source oriented in the direction of a constant magnetic field, are presented in graphical form. A proper ionospheric plasma is assumed for this calculation, which combines some of the results obtained for anisotropic cold-plasma problems on the one hand and some of the results obtained for isotropic warm-plasma problems on the other hand.
An Integral Formula for Two-Dimensional Fields
Authors: Beth Richard A.
Published: January 2005

The complex analytic function treatment previously given [J. Appl. Phys. 37, 2568 (1966)] for two-dimensional magnetic fields outside conductors is extended to regions of constant current density, σ, inside conductors. Separate analytic functions for field points Z = X+iY inside and outside such conductors are given by the integral formula F(Z)=iσ∮z*dz/(z−Z), where z* is the complex conjugate of z = x+iy on the conductor circumference. The complex field, H = HY+iHX, is then F(Z) + 2πσZ* for points Z inside the conductor and F(Z) for Z outside. If we replace σ by −iρ we obtain the field E = EY+iEX in the analogous electrostatic case with constant charge density ρ, e.g., for a uniform beam of charged particles. The results are illustrated by evaluating the integral for an elliptical contour.
Electrical Properties of Niobium-Doped Ferroelectric Pb(Zr, Sn, Ti)O3 Ceramics
Authors: Taylor G. W.
Published: January 2005

Hysteresis loop, pulse switching, and aging measurements have been made as a function of composition, sample preparation and thickness, electrode material and size, on 24 rhombohedral ferroelectrics from the Pb0.99[(ZrxSny)1−z Tiz]0.98Nb0.02O3 ceramic family to determine their properties and usefulness for device applications.

Results show that many of these ceramics have extremely high remanent polarization, saturation polarization, loop squareness, tolerance-to-matrix-type disturb pulses, switching speed, and minimal excitation aging. The polarizations, squareness, apparent coercive field, disturb-pulse tolerance, and aging of the apparent coerive field all increase with increasing x/y. The definite dependence of the properties on z is, in general, random. Samples prepared with smooth surfaces, such as by polishing or doctor-blading, had properties approaching those of a single crystal. The observed electrode-edge effects can be explained in ceramic terms.

These materials, while retaining all the conventional advantages of ceramics, have electrical properties equal to, and in some cases, such as polarizations and disturb-pulse tolerance, superior to single-crystal ferroelectrics. These ceramics are thus very suitable for ferroelectric memory and display devices.
Particle-Size Distribution of CoFe2O4 Formed by the Coprecipitation Method
Authors: Hasegawa Kin'ichi , Satō Toshihiko
Published: January 2005

The particle size distribution of CoFe2O4 formed by the coprecipitation method was investigated by x-ray diffraction and electron microscopy. In the x-ray diffraction method, 〈110〉 column length distributions were calculated by Warren's procedure. A particle size distribution was obtained from the 〈110〉 column length distribution by assuming that each particle was a spherical crystallite. The particle size distribution of CoFeO4 formed at 100°C covered a range of 0–350 Å and showed a maximum at 180–200 Å on volume base. From changes of the 〈110〉 column-length distribution by heat treatments, it was suggested that crystal growth of smaller particles was noticeably advanced at a temperature of 300°–400°C. The above results were supported by electron microscopy.
An Interferometric Study of a High-Intensity, Hollow-Cathode Source
Authors: Davies D. Kenneth
Published: January 2005

Measurements of the profile of the λ 3247.5-Å copper resonance line emitted from a high-intensity, hollow-cathode source of the Sullivan—Walsh type have been made using a pressure-tuned, Fabry—Perot interferometer. It is found that the enhanced intensity from this source compared with that from a conventional hollow-cathode source is accompanied by a considerable decrease in the self-absorption of the resonance line within the source. The line-profile measurements together with measurements of the decay of the resonance radiation on switching off either the hollow-cathode discharge or the auxiliary discharge are in qualitative agreement with the hypothesis that the radiation is emitted partly from the hollow-cathode discharge and partly from the auxiliary discharge.