bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Oxidation of Thin Gold-Nickel Alloy Films
Authors: Khan I. H. , Francombe M. H. 
Published: April 2005

The structure and oxidation of thin alloy films of composition Au-15 at.% Ni have been investigated by means of x-ray and electron diffraction, and the oxide growth rate determined by measuring changes in the electrical resistivity of the films during oxidation. The films are prepared by sputtering and, even at low substrate temperatures, comprise single-phase homogeneous structures. Oxidation in the temperature range 250°–310°C shows a two-stage logarithmic growth rate (or resistivity change) with time similar to that observed for Ni, Cu, and Fe. This behavior is consistent with the formation of oxide only at the alloy film surface, and can be interpreted qualitatively in terms of the electron-transfer model proposed by Uhlig et al., for the oxidation of pure Ni.
Epitaxial alloy films with (001) and (111) orientation are produced by sputtering onto the cleaved surfaces of NaCl and mica at about 400°C. On annealing these films at and above 500°C, pre-precipitation effects are observed in the electron-diffraction patterns. These are associated with the formation, in succession, of the superlattice structures, NiAu3 and NiAu. True precipitation of Ni-rich alloy occurs at temperatures above 600°C.
Oxidation of epitaxial films of the disordered alloy at temperatures below 250°C results in the growth of poorly crystallized, non-oriented NiO. At 280°C both non-oriented and also three differently oriented oxide products, are formed, the NiO orientations corresponding to those reported by Collins and Heavens for oxide growth on Ni films. At 400°C only oxide orientations parallel to the metal film are detected.
Variation of the Gain Factor of GaAs Lasers with Photon and Current Densities
Authors: Nannichi Yasuo 
Published: April 2005

The variation of the gain factor with the threshold current was studied in two cases, viz., (1) a reflective film was applied on one end of a GaAs laser, and (2) antireflective films were applied on both ends of the laser. In (1) the threshold current is reduced to one third as compared with the case in which no film is applied. The gain factor increases 30%. In (2) the threshold current becomes eleven times greater and the gain factor is reduced to one fourth.
These phenomena were analyzed in the light of spontaneous and stimulated lifetime of electrons in the p region. A formula was obtained giving the gain factor as a function of the density of photons and of current. When the current is constant, the gain factor is inversely proportional to (P+1), where P is the density of photons. At the threshold current the gain factor is inversely proportional to the sum of quasi-Fermi levels, Fn and Fp.
The saturation effect of a light amplifier at a fixed current observed by Crowe and Craig and also the variation of the gain factor with the threshold current can be calculated by this formula.
Depletion Capacitance and Diffusion Potential of Gallium Phosphide Schottky-Barrier Diodes
Authors: Cowley A. M. 
Published: April 2005

The diffusion potential VBO and the intercept V0 of the 1/C2 vs bias plots for n-type GaP-metal Schottky-Barrier diodes have been measured. Photoresponse measurements indicate that VBO is not sensitive to the thickness δ of the interfacial separation between the GaP and the metal; V0 is observed to increase rapidly with δ. The 1/C2 plots are linear in all cases, with slopes independent of V0. The values for the donor density ND, calculated in the usual way from slopes of the 1/C2 plots, seem to agree within experimental error with ND calculated from the resistivity of the GaP.
Several models are proposed for the metal-interfacial-layer-semiconductor system in order to explain this behavior. The GaP-metal diodes are shown to be best characterized by a model which includes a bias-dependent charge in surface states at the semiconductor surface.
Transient Spin-Wave Buildup in Ferrites
Authors: Harker K. J. , Shaw H. J. 
Published: April 2005

The equations of motion for spin waves in a ferrite, together with the equations for the uniform mode, have been numerically integrated for the case in which the ferrite is spherical in shape and subjected to an applied magnetic field which rises linearly in time. The equations for the uniform mode are completely general and allow for arbitrary amplitude of the mode, so that parametric couplings which lead to spin-wave instabilities of various orders are accounted for, including the ordinary first-order and second-order spin-wave instabilities. The spin-wave equations are solved to first order in the spin-wave amplitudes.
The equations have been solved under the conditions of a linearly rising magnetic field having arbitrary rate of rise, together with a dc applied magnetic field of arbitrary magnitude, and for arbitrary angle between the orientations of the rising and dc fields. Assuming that spin waves are initially excited to thermal amplitudes, a numerical integration is performed over k space to find the aggregate spin-wave growth as a function of time, and the energy in the uniform mode as a function of time in the presence of the amplified spin waves. These results define the conditions under which useful transient devices can be operated for the generation of microwave energy in pulsed magnetic fields, to take advantage of the large rf magnetization available in ferrites when operated beyond the usual limiting values of the uniform mode which apply under steady-state operation.
Mössbauer Study of the Structure and Decomposition of Wustite
Authors: Shechter Hanan , Hillman Peter , Ron Moshe 
Published: April 2005

A series of Mössbauer, x-ray, and magnetic measurements has been made on wustite (Fe1−xO). The main new results are:
(a) The dependence of the Mössbauer quadrupole splitting on heat treatment is very similar to that of the atomic constant, confirming Hoffman's conclusions on the variation of x.
(b) The Zeeman Mössbauer lines of untreated wustite below the Curie temperature are completely smeared out; for a sample treated so as to give minimum quadrupole splitting (minimum x) these lines appear.
(c) In a heat-treated sample a Zeeman splitting in the Mössbauer spectrum is observed well above the bulk wustite Curie temperature. This is interpreted as the imposition by the magnetic decomposition products of a magnetic ordering on the otherwise paramagnetic residual wustite with which they are in intimate contact.
Power Flow in Plasma-Filled Waveguides
Authors: Bevc Vladislav 
Published: April 2005

The power flow of two types of cyclotron modes propagating in a waveguide filled with a cold collisionless axially magnetized plasma is studied as a function of the location of the point of operation on the Brillouin (ω-β) diagram. Dynamic analysis is used throughout. Partition of the total power flow corresponding to E, H, and EH power is examined and compared with results obtained by the quasistatic approximation in the domain of its presumed validity. The inadequacy of the quasistatic approximation for the analysis of the power flow, and hence the field patterns, is shown.
New properties of cyclotron and plasmaguide modes obtained from the analysis are presented. A possible explanation is offered for the lack of published experimental observation of cyclotron modes in the superluminous phase velocity region.
Behavior of Superconducting Coil Subjected to Steady Local Heating within the Windings
Authors: Stekly Z. J. J. 
Published: April 2005

The steady-state heat conduction equation in a nonisotropic solid is solved for the relationship between local heat imput, the size of the heated region and the Joule heating in the resultant normal region. The results are used to derive the steady terminal voltage-current characteristics of a superconducting coil with heat generation within the windings. These terminal characteristics exhibit both a positive as well as a negative slope of the voltage versus current curve. A map of the expected behavior of a current carrying superconducting coil with heat generation in the windings shows that the coil can do one of three things: (1) remain fully superconducting; (2) operate in a stable manner with a nonpropagating normal region; (3) go fully normal (quench).
The analytical results are compared with measurements taken with a noninductive and an inductive coil. The measured terminal characteristics as well as over-all coil behavior agreed well with the result derived analytically.
Some Remarks on Hysteresis
Authors: Biorci G. , Pescetti D. 
Published: April 2005

This paper considers two approaches by which the Preisach distribution function may be obtained from experimental hysteresis curves, and then compares the results of these approaches with Bate's experimental results.
The first method, based upon the assumption that φ(a,b) = φ1(a)·φ2(b), was proposed by the authors in 1958. The second method is valid under other assumptions, and requires simple computations only. The comparison shows good agreement between the two methods, and with experimental data.
Epitaxial Deposition of Germanium by Both Sputtering and Evaporation
Authors: Krikorian E. , Sneed R. J. 
Published: April 2005

The structural characteristics of germanium films deposited onto germanium (111) and CaF2 (111) substrates have been characterized as a function of sputtering and evaporation parameters. Diagrams defining epitaxial temperatures and amorphous-polycrystalline transition temperatures have been obtained both for sputtered and evaporated films. It is demonstrated that these transitions are a function of the growth rate and background pressure only. Neither the particular deposition conditions which control the growth rate (voltage and current in sputtering, source temperature, and source-substrate distance in evaporation) nor the deposition techniques influence the transitions as long as the background pressure and growth rates are identical.
A qualitative model based on the relation between growth rate and surface mobility is presented which appears to adequately describe the growth-rate-epitaxial-temperature relations, including background pressure effects. The experimental data yield an activation energy for the onset of epitaxy at very low background pressures (evaporation) of 18 000 cal/mole, which is in good agreement with the activation energy for surface diffusion of germanium on germanium. Other activation energies ranging from 10 800 cal/mole at 65 μ argon pressure to 17 400 cal/mole at 8 μ argon pressure, have been obtained for sputtered films. The pressure dependence of the activation energy has been accounted for by the model presented.
It is also demonstrated that the growth rates in all states of the film (amorphous, polycrystalline, and monocrystalline) are decreasing functions of substrate temperature. At any given temperature, the observed growth rates are dependent only on the incidence rate, and are independent of the technique (sputtering or evaporation) and of the conditions used to achieve the incidence rate. The dependence of growth rate on substrate temperature is consistent with established nucleation theory and yields activation energies for single-crystal growth of approximately 10 000 cal/mole, for polycrystalline growth of approximately 3000 cal/mole, and for amorphous growth of approximately 600 cal/mole. These activation energies are independent of the deposition technique (evaporation or sputtering), the deposition conditions, and the incidence rate.
Thermodynamic Aspects of the Temperature—Pressure Phase Diagram of InTe
Authors: Banus M. D. , Robinson P. M. 
Published: April 2005

The heat of transformation at one atmosphere from the metastable high-pressure phase of InTe to the low-pressure phase has been measured by metal solution calorimetry to be 0.44±0.01 kcal/g·atom and by differential scanning calorimetry to be 0.42±0.03 kcal/g·atom. These values are compared to the heat of transformation at 30 kbar obtained by applying the Clausius—Clapeyron equation to the temperature—pressure phase diagram of InTe.
The volume change on fusion of the low-pressure phase, InTe(I), at one atmosphere was measured to be 0.80 cc/mole. The initial slope of the liquidus in the phase diagram calculated using this value is in close agreement with the previously determined experimental slope. It is estimated that the triple point between the liquidus and the InTe(I)—InTe(II) phase boundary occurs at 718°C and 11 kbar.
Effect of Crystallite Size on Coercive Force of Thin Ferromagnetic Films
Authors: Heinzel C. O. , Walker G. A. 
Published: April 2005

This paper describes the effect crystallite size has on the coercive force Hc of thin ferromagnetic films. Crystallite size was determined by the use of x-ray diffraction using a small angle between the x-ray beam and film samples. Films in this study ranged in thickness from 150 to 1750 Å with crystallite size from 50 to 950 Å and Hc values of 2.1 to 8.4 Oe.
It was found that Hc is dependent on the crystallite size for films that have domain wall widths larger than the crystallite size. The data exhibits a decreasing Hc as the crystallite size increases for films with Néel or crosstie domain walls. For films with Bloch walls and crystallite size greater than the domain wall width, there is no apparent dependence on crystallite size of Hc.
To a first approximation, the results of this study are shown to agree with the anisotropy constant variation term from Middelhoek's semiquantitative theory for coercive force of thin magnetic films. For films with domain wall widths larger than the crystallite size, this term contributes to the over-all coercive force.
Magnetic Flux Compression by Magnetically Imploded Metallic Foils
Authors: Cnare Eugene C. 
Published: April 2005

A 136-kJ capacitor-bank energy source was used to implode metallic foils in a ``theta'' pinch. Aluminum foils accelerated by this scheme attained a velocity of 2.3 mm/μsec and a capacitive-to-kinetic energy conversion efficiency of 23%. An upper limit for the foil velocity depended upon the foil thickness and density, together with a parameter which accounted for electrical heating of the foil. This parameter was determined in exploding wire studies.
Experiments with and without auxiliary injection of magnetic flux are described. Thick, imploding foils have been found to be capable of compressing enclosed magnetic flux to more than 2 MG.
Further Studies of Intercrystalline Links in Polyethylene
Authors: Keith H. D. , Padden F. J. , Vadimsky R. G. 
Published: April 2005

A previous study of intercrystalline links in polyethylene, carried out using fractionated polymer only, has now been extended to mixtures of fractions and to whole polymer. There is little difference between links grown from concentrated (50%) solutions of polyethylene in n-C32H66, regardless of the molecular weight distribution of the polymer. These links exhibit surfaces that are more or less featureless and the evidence indicates that they are composed of molecules crystallized, for the most part, with extended conformations. However, when these links are used as substrates upon which polyethylene is deposited epitaxially from dilute (1% or less) solution in later, quite separate, crystallization experiments, lamellar overgrowths are formed which demonstrate unambiguously the crystallization of molecules in folded conformations.
The marked difference between these cases is attributed to entanglements which, as crystallizing molecules are ``reeled in'' to growth fronts, cause neighboring molecules to become extended and partly aligned in directions normal to these fronts. Links grown from concentrated solutions are built up from such molecules whose conformations are grossly disturbed by this crystallization-induced orientation. However, epitaxial overgrowths deposited from dilute solution are built up from molecules whose conformations in solution are unaffected, and these then crystallize conventionally with folded conformations.
Dislocations Caused by Chain Ends in Crystalline Polymers
Authors: Predecki Paul , Statton W. O. 
Published: April 2005

The molecular arrangement in the immediate vicinity of a chain end in a crystalline polymer such as 66 nylon is considered. It is shown that four simple kinds of line defect can be generated by such a chain end. One of these, called a coupled-screw dislocation, is unique to long chain structures and has not been proposed before. The remaining three are (1) vacant chain site or coupled-edge dislocation, (2) and (3) the more conventional screw and edge dislocations. These dislocations run from one chain end to another and create a three-dimensional defect network, possibly explaining the anomaly of weak x-ray diffraction intensity from (010) planes. If the ends are randomly distributed, the network may disorder the structure sufficiently to make it appear ``amorphous'' to x rays.
When sufficient segmental mobility exists, it is probable that this network will rearrange itself into a more ordered substructure of lower energy. Such a substructure might include: (a) clusters of chain ends and associated defects, (b) chain ends which are condensed into line defects, (c) boundaries between adjacent misaligned crystalline regions.
Cold-Beam-Plasma Interaction Theory for Finite Transverse Dimensions and Finite Magnetic Fields
Authors: Simpson J. E. , Dunn D. A. 
Published: April 2005

The dispersion relation for interaction between a cold electron beam and the electrons of a cold, uniform density plasma of a circular cylindrical cross section and of a radius equal to that of the beam inside a conducting pipe of a larger radius has been solved on a computer for a number of values of finite magnetic field, the ratio of plasma density to beam density, and beam perveance. Complete ω-k diagrams are given for various cases along with more extensive data on the growing wave gain that occurs below the plasma frequency and the cyclotron frequency.
A comparison with experimental data on a beam-generated plasma is given and the theory is shown to provide a satisfactory explanation for the onset of oscillations in such a system with a finite length.
Scaling Underwater Exploding Wires
Authors: McGrath James R. 
Published: April 2005

The parameters of peak pressure and decay time constant of the shock wave caused by electrically exploding wires underwater have been compared to TNT data and theory. The wire used was 5-mil, ½-in. Nichrome. Electrical energy up to 100 J was stored in the capacitor.
The results indicate that peak pressure reduces to the same kind of similitude functions as those used for TNT data if losses owing to the circuit and heating of the wire are accounted for. On this basis, an expression for the equivalent weight of TNT (on the order of micropounds) is presented in terms of the electrical parameters and heat of detonation.
The reduced time constant for exploding wires also reduces to the same kind of similitude function as those used for TNT data. The magnitude and behavior of the reduced time constant are comparable to TNT data.
Effect of Deformation-Induced Crystal Imperfections on Magnetocrystalline Anisotropy of Nickel Single Crystals
Authors: Bhattacharyya Arup , Pollack Solomon R. , Maddin Robert 
Published: April 2005

The first magnetocrystalline anisotropy constant of plastically deformed nickel single crystals was studied as a function of deformation. Contributions of specific types of imperfection, viz., interstitials, vacancies, and disclocations on the ``effective magnetic anisotropy constant'' K1′ were analyzed from the recovery characteristics of K1′. The dislocation structure of the deformed crystals was investigated by transmission electron microscopy at various stages of recovery.
The absolute value of K1′ increased with deformation. The maximum change occurred at a strain ε≈0.17 with an increase of about 6.5% from the undeformed value of K1 = −5.52×104±0.02×104 erg/cc measured at 21.5°C and at a magnetic field of 8 kOe. Point defects were not found to have a measurable effect on the recovery of K1′. Deformation-induced dislocations were mainly responsible for the observed change. The recovery of K1′ was interpreted in terms of rearrangement and annihilation of disclocations.
Cation Self-Diffusion and Electrical Conductivity in Polycrystalline Beryllium Oxide
Authors: De Bruin H. J. , Watson G. M. , Blood C. M. 
Published: April 2005

Beryllium self-diffusion coefficients were determined in high-density polycrystalline BeO in the temperature range 800° to 1795°C. A precision lapping method using Be as a radiotracer was used in the interval above 1180°C, and electrical conductivity between 800° and 1250°C. Volume diffusion coefficients determined by both methods correlate well between 1100° and 1250°C. The results can be expressed over the temperature range 1100° to 1800°C by the relation D=3.2×10−3 exp(−63.0×103/RT).
Above 1100°C, the agreement between the results obtained by the two techniques supports an ionic drift mechanism for the electrical conductivity of BeO. Below this temperature, however, the transport behavior appears to be considerably influenced by the history of the sample as well as the nature and concentrations of impurities.
Classical volume diffusion was observed in a region near the surface of the specimens; at greater depths, deviations occurred and the magnitude of the deviations increased with decreasing grain size of the BeO. These discrepancies have been explained on the basis of a simultaneous grain-boundary diffusion mechanism.
Thermal Properties of Molecular Crystals. I. Heat Capacity and Thermal Expansion
Authors: Bondi A. 
Published: April 2005

The lattice heat capacity Cvs and especially the difference Cps-Cvs of molecular crystals composed of rigid molecules is shown to be well represented by a suitably modified form of the Leibfried and Ludwig theory of anharmonic crystals. Crystals of low packing density (ρ*&lt;0.65) such as benzene require a (fairly large) heat capacity correction for the heat of lattice defect formation. An empirical correction of the theory is proposed to adapt it for the estimation of Cvs of crystals composed of flexible molecules.
The expansion coefficient (αs) of molecular crystals composed of rigid molecules at 0.7Tm&lt;T&lt;0.9Tm is represented by a universal value of the dimensionless number αs*=αsΔHs/Cvs first proposed by Grueneisen and also derivable from Ludwig's theory of anharmonic oscillator crystals. Variants of αs* are discussed also for hydrogen-bonded crystals and for crystals composed of flexible molecules.
Improved Surface Ionization Efficiency by High Work Function Refractory Metals and Alloys
Authors: Husmann Otto K. 
Published: April 2005

For continuous one-year operation without deterioration of the surface ionization engine characteristic, the neutral efflux should be in the 0.1% range. For the neutral efflux reduction the Saha equation implies the use of high work function metals. Therefore, tungsten-rhenium alloys and iridium filaments were investigated. For completeness, tungsten and rhenium filaments were also studied with regard to their thermionic work function and threshold temperature for cesium surface ionization. The data were measured in an all-metal guard ring diode with directly heated filament under clean surface conditions. The electron work functions and the threshold temperatures of the tungsten-rhenium alloys increase with increasing amount of rhenium in tungsten. For φ-I≤0.5 eV the electron work function governs the surface ionization.
One porous tungsten-25% rhenium pellet and two porous tungsten substrates chemically coated with rhenium and iridium yielded work functions below those measured with the corresponding filaments. At 10-mA/cm2 cesium ion current density, the neutral efflux from the rhenium coated pellet was, with 2×106 pores/cm2 (traverse counting technique), 1%±0.1%. Under clean conditions 0.3% neutral efflux may be expected. The increase of the threshold temperature with electron work function leads to increased grain size and lower pore density for long term stability of the porous structure.