bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectroscopic Studies of the Ar+ Laser
Authors: Rudko R. I. , Tang C. L.
Published: January 2005

The spontaneous intensities of all the laser transitions as well as the important cascade transitions into the upper laser states of a typical cw Ar+ laser have been measured. In addition, we give here the calculated Einstein A coefficients and the radiative lifetimes of all the upper states of all these Ar+ transitions. From these results, we have also obtained the population densities and the various pumping rates of all the laser states and those states which contribute significantly to the upper laser states through cascade transitions. On the basis of these and other related data, a number of conclusions on the physical processes taking place in the Ar+ discharge can be reached. Furthermore, some of the previous suggestions and speculations on these processes can now be evaluated on a more quantitative basis; some of these are discussed here.
Electrical Properties of the Interface Region of the Ge-Si Alloyed Heterojunction
Authors: Thompson H. W. , Reenstra A. L.
Published: January 2005

The interface transition region of the n-n germanium-silicon heterojunction is studied to determine its electrical properties and its width as a function of fabrication process variations. Ohmic contacts are made to the p-type transition region while p-n junction isolation is maintained to the n-type bulk materials.

Electrical measurements of the transition region determine conductivity and Hall coefficient over the temperature range from 77° to 273°K. Capacitance data are obtained between the transition p-layer and the n-type germanium over the same temperature range. These measurements permit determination of activation energies of the interface states within the transition region, the carrier concentration, and the carrier Hall mobility. Transition widths are shown to be of the order of microns, are shown to increase with increased interdiffusion times, and decrease with slower recrystallization rates. Data suggest a nonabrupt transition from germanium to silicon in the alloyed heterojunction.
Annealing of Hall-Mobility Changes in Electron-Irradiated Germanium
Authors: Jaworowski A. , Merski K. , Rzewuski H. , Werner Z.
Published: January 2005

Annealing of Hall-mobility changes in n-type germanium irradiated with 1 MeV electrons at 85°K was investigated using an isochronal technique. Two annealing stages which have been reported earlier were confirmed and separated.

One stage at above 100°K is connected with ``contact'' annealing, and a second one close to 140°K is caused by bulk annealing. The latter stage corresponds to the stage found already by J. C. Pigg for gamma irradiation.
Mössbauer-Effect Study of Solid-Solution and Precipitated Fe-Rich Fe-Mo Alloys
Authors: Marcus H. L. , Fine M. E. , Schwartz L. H.
Published: January 2005

A detailed study of the precipitation reaction in an Fe-6 at.% Mo alloy at 550° and 650°C was made using the Mössbauer effect and Young's modulus. Mössbauer spectra of Fe2Mo, Fe3Mo2, and alloys of 2.5 and 20 at.% Mo were also obtained.

The Mössbauer spectra of the Fe-base Mo solid solution were analyzed on the basis of a 14 near-neighbor model. The six peaks of the Fe spectrum in the alloy were broadened into six envelopes. These were analyzed as a superposition of three sets of peaks, one set each for Fe atoms with 0, 1, and 2 Mo atoms among the 14 near-neighbors giving in the as-quenched Fe-6 at.% Mo alloy hyperfine fields of −335±1, −296±1, and −255±2 kOe and the isomer shifts relative to pure Fe of +0.01±0.005, −0.02±0.01 and −0.05± 0.02 mm/sec, respectively.

The precipitation in the Fe-6 at.% Mo alloy at 650°C occurred by a one-step process while the 550°C aging sequence occurred by a two-stage reaction, first clustering of Mo and then precipitation. An activation of 59 kcal/mole and a rate exponent of 1.2 were determined from modulus and Mössbauer data suggesting diffusion-controlled growth of thin long platelets.

The solvus composition Cs in the temperature range 650°–870°C was found by quantitative analysis of the Mössbauer spectra to follow the empirical relation Cs = exp − (7400/RT) at.% Mo assuming the precipitate to be Fe2Mo. A mass balance ruled out Fe3Mo2 (or Fe7Mo6). The Fe2Mo precipitate was confirmed in the Fe-20 at.% Mo alloy by x-ray diffraction.
Magnetostriction in Ferromagnetic CdCr2Se4
Authors: Eastman D. E. , Shafer M. W.
Published: January 2005

The magnetostriction constants λ100 and λ111 of CdCr2Se4 have been measured using a ferromagnetic resonance technique. At 4.2°K the results are: λ100 = +2.6×10−6 and λ111 = −28×10−6. The dominant λ111 is of single-ion origin, and its magnetization dependence is described very well by the single-ion theory of Callen and Callen. A ferromagnetic resonance linewidth of 15 Oe and anisotropy constant K1 of 3.5×103 erg/cc have been determined at 4.2°K. The Curie temperature, determined by an initial permeability method, was 129°±2°K.
Photoemission in Thin-Film Metal-SiOx-CdSe and Metal-SiOx-Metal Contacts
Authors: Waxman A.
Published: January 2005

Photoemission from vapor-deposited CdSe and metal electrodes into vapor-deposited silicon monoxide films has been used to determine the barrier heights at the interface. For the CdSe-SiOx interface, a threshold energy of 4.8 eV is determined. Higher values of threshold energy are found for photoemission from gold into silicon monoxide, then from aluminum, indicating that the photocurrent is carried by electrons. In addition, the μτ product of electrons in the insulator has been determined by studying the photocurrent-voltage dependence; μτ = 2.1×10−11 cm2/V. This value is two orders of magnitude less than the results obtained for thermally grown SiO2. The presence of residual space charge with no applied field is observed and the effect of this space charge on the photocurrent is discussed.
Beam-Plasma Interaction with Transverse Modulation
Authors: Mills D. M. , Abraham E. E. , Crawford F. W.
Published: January 2005

This paper describes experimental observations of electron beam-plasma interaction in low-pressure mercury-vapor discharges. Comprehensive data have been obtained of rf growth, phase velocity, axial and radial electric field profiles in the interaction region, and Faraday rotation, for the case of transverse modulation, i.e., for growth in the first azimuthally-varying mode (m = 1). The work complements previous parallel studies of the axisymmetric mode (m = 0) made with axial modulation. The results are compared with cold- and warm-plasma theories of the interaction. It is concluded that the warm-plasma theory gives a satisfactory approximation to the experimental results, and that the remaining discrepancies are due to lack of sharpness of the experimental beam edge.
Mode Pulling in a Stimulated Raman Oscillator
Authors: Tannenwald P. E.
Published: January 2005

Stimulated Raman scattering has been observed in quartz at low temperatures in which the 467 cm−1 Stokes line is split into two or more sharp components. The quartz samples, which were in the form of resonant cavities, behaved as Raman oscillators pumped by a ruby laser. Measurement of the Fabry—Perot mode spacings of the oscillators showed that substantial mode pulling was occurring. This was interpreted according to mode-pulling theory.
Morphological Changes in Discontinuous Gold Films following Deposition
Authors: Skofronick J. G. , Phillips W. B.
Published: January 2005

Vacuum-deposited discontinuous gold films are observed to exhibit temperature-dependent morphological changes following deposition. This effect is observed on both carbon and silicon monoxide substrates. For substrate temperatures between approximately 450° to 750°K the initial deposited nuclei are nearly circular and have a doubled-peaked size distribution. Because of resolution limitations only the part of the distribution with the large sizes is quantitatively examined and discussed. Analysis of the distributions at different time intervals following deposition shows a shift in both the mean radius and the dispersion and a decrease in the number of nuclei per unit area. These changes are discussed in terms of possible mass transfer along the surface.
Ionic Conduction and Diffusion in Single Crystals of SrCl2
Authors: Hood G. M. , Morrison J. A.
Published: January 2005

This paper reports the results of measurements of electrical conductivity and tracer (90Sr and 36Cl) diffusion in single crystals of SrCl2, both nominally pure and doped with the aliovalent ions Y3+ and Na+, in the temperature region 20° < T < 780°C. The conductivities for nominally pure crystals agree well (within a factor of 1.5) with some for a more limited range (150° to 650°C) recently published by Barsis and Taylor. Moreover, the observed effects of the addition of aliovalent impurities are similar. Some of the detailed conclusions reached are different, however.

Insofar as it can be pressed, the analysis of the data leads to the following conclusions. (i) The predominant imperfections are anionic Frenkel defects. (ii) The ionic transport is overwhelmingly anionic under all conditions. (iii) The experimental correlation factors cannot distinguish between an interstitialcy and a vacancy-transport mechanism but general considerations favor the latter. (iv) The behavior of the diffusion and conductivity at lower temperatures (T < 500°C) indicates that complexes of defects form, but no detailed information is derivable.
Relaxation Phenomena in High-Resistivity Ge:Hg
Authors: Williams R. L.
Published: January 2005

Under reduced background conditions a mercury-doped germanium photoconductor has a slow component of the response time given by the dielectric relaxation time ερ/4π. It has been shown that this is valid for small or very large signals. Further, the dielectric relaxation effects are the same whether the resistance is determined through photo-generation by background radiation or by thermal generation of holes.

The capacitance calculated from the ratio of response time to element resistance is the element capacitance for low-dislocation material. For germanium with significant lineage this parameter has a value an order of magnitude larger than theory. This indicates rather gross inhomogeneities in lifetime within the crystals. Even for the best crystals 50% of the signal has the long dielectric relaxation response time.
Kinetics of an Optical Wave Packet in a Lens-like Medium
Authors: Kawakami Shojiro , Nishizawa Jun-ichi
Published: January 2005

The motion of a wave packet in a nonuniform medium is discussed. It is found that the wave-packet motion, obtained by WKB method, is the same as one obtained by geometrical optics. The wave packet, in general, undulates around the axis. As the direction of the beam and the local refractive index change as the packet travels, the axial velocity component of the beam is modulated. This seems to be in contradiction to the constancy of the group velocity. This apparent contradiction is eliminated by examining the shape of a wave packet composed of a single transverse mode, which turns out to be warped. As an example, a medium is assumed in which the dielectric constant decreases quadratically, away from some spatial axis. The group velocity of several undulating packets in the medium is very close to that of a straight ray. Numerical calculation is presented.
Effect of Heat Treatment on Photoluminescence of Zn-Doped GaAs
Authors: Hwang C. J.
Published: January 2005

Comparisons of photoluminescence at 20°, 77° and 300°K are made for Zn-doped GaAs before and after heat treatment. It is found that the intensity of the Zn acceptor band I (hvZn) increases after heat treatment at 800°C for acceptor concentrations NA up to approximately 7×1018 cm−3. For NA > 7×1018 cm−3, I (hvZn) remains unchanged by heat treatment. These results can be attributed to lattice defects which dominate the nonradiative processes and are annealed out by heat treatment. Isochronal annealing of a lightly doped crystal in the temperature range 600°–1100°C shows that 800°C is the optimum heat-treatment temperature for maximum luminescence intensity. This result can be rationalized by considering the temperature dependence of the total defect concentration. The broad band at 1.37 eV commonly seen in p-type GaAs photoluminescence is found to practically disappear after heat treatment at temperatures greater than 600°C.
Cataphoretic Purification of Gases
Authors: Freudenthal J.
Published: January 2005

Two types of purification devices for gases are described. The purification effect is based on the cataphoretic segregation in the positive column of a low-pressure discharge. This segregation as a function of time is given in terms of the tube current, gas pressure, and the tube dimensions. From them optimum conditions can be chosen for a high final purity and a high purification velocity. Experimental results of the segregation in a discharge in neon with an impurity of argon are given.
Domain Structure and Twinning in Crystals of Vanadium Dioxide
Authors: Fillingham P. J.
Published: January 2005

Domain patterns visible in reflected polarized light on surfaces of vanadium dioxide are described. Several x-ray reflection techniques and analysis of the reflected polarized light are used to investigate the domain structure of the low-temperature monoclinic phase of VO2. This is shown to be due to transformation twinning in which the monoclinic unit cell is rotated into successive ninety-degree positions about the a-monoclinic axis.
Self-Absorption Effects in the Soft X-Ray Mα and Mβ Emission Spectra of the Rare Earth Elements
Authors: Fischer David W. , Baun William L.
Published: January 2005

The Mα and Mβ emission spectra and the MIV and MV absorption spectra have been studied for the rare earth elements. It is conclusively shown that the complicated multiplet structure observed in the emission spectra is not real emission structure but is, instead, produced by sample self-absorption. This is demonstrated by observing the emission spectra over wide variations in take-off angle and bombarding-electron energies and finally by comparing the detailed structure of both the emission and absorption spectra. The MIV and MV absorption structure completely overlaps the Mα and Mβ emission lines which are each found to have but one intensity maximum when obtained under conditions of minimum self-absorption. Some of these spectra have never been shown previously, while others have been studied in detail by several investigators. Points of agreement and disagreement with previous work are mentioned and the wavelengths of the emission lines and absorption edges are listed for all of the lanthanides. It is concluded that 4f→3d electron transitions are reversible in these elements.
Phonon-Terminated Coherent Emission from V2+ Ions in MgF2
Authors: Johnson L. F. , Guggenheim H. J.
Published: January 2005

Infrared fluorescence and phonon-terminated stimulated emission from V2+ ions in MgF2 is reported. Fluorescence is produced in transitions from the first excited state 4T2(4F) to the ground state 4A2(4F). Stimulated emission occurs in the vibronic sideband at 1.1217 μ (8915 cm−1) and lies 1166 cm−1 from the no-phonon line. A gain curve calculated from the optical spectra predicts an oscillation frequency in reasonable agreement with the observed frequency, with a cross section for stimulated emission of 8×10−21 cm2. From the effect of excited state absorption on the gain profile it is concluded that the excited state absorption cross section at the maser frequency is <3×10−21 cm2.
Triaxial Fracture Studies
Authors: Lindsey Gerald H.
Published: January 2005

The fracture behavior of a polyurethane elastomer in a hydrostatic tensile field has been experimentally studied via the ``poker-chip test.'' Microscopic examination of the material revealed residual gaseous bubbles, which were taken as fracture nucleation points. A study of the cavity behavior up through fracture initiation and propagation led to a determination of the fracture stress level, the identification of two regimes, or modes, of fracture, and the associated velocities of propagation.
Low-Field Galvanomagnetic Effects in Sn-Doped Bi Crystals at 77°K
Authors: Bate R. T. , Hardin W. R. , Einspruch N. G.
Published: January 2005

Measurements of weak-field galvanomagnetic effects in single crystals of bismuth doped with varying concentration of tin up to 4×1018 cm−3 are reported. In addition to the two resistivity components, ρ110 and ρ330, and the two Hall coefficients, R123 and R231, values for most of the second order galvanomagnetic coefficients, Aij, and some of the third- and fourth-order coefficients, Tijk and Fijk, are given. (The notation is that of Juretschke.) Some measurements on pure bismuth are also reported, and evidence is given that earlier workers did not use magnetic fields sufficiently small to avoid contributions from terms of higher order in magnetic field.
Dielectric and Optical Properties of Crystalline Argon
Authors: Lefkowitz I. , Kramer K. , Shields M. A. , Pollack Gerald L.
Published: January 2005

Studies of the crystal optics, dielectric properties from 10 Hz to 10 kHz, and the electro-optical properties of crystalline argon, grown with a modified Bridgman technique, are reported. The optical character of the solids was examined using polarized light, with varying crystal growth parameters, viz., rate, annealing, and pressure. Using crossed polaroids to examine the transparent crystals, three basic kinds of optical regions were observed: optically isotropic, optically anisotropic (birefringent), and sharp, horizontal, alternate isotropic and anisotropic striations. Low-order strain birefringence with broad and diffuse patterns is also described. The observations are considered in terms of impurity segregation and strain effects and it is concluded, with support from annealing and electro-optic studies up to 40 kV/cm, that the birefringent regions have hcp structure and the isotropic regions have fcc structure. The dielectric constant (ε) was directly measured for solid argon between two concentric stainless-steel cylinders in a three-terminal network that minimized stray fields. It was found that ε = 1.586 over the entire frequency range with an estimated experimental error of 2%. Variation of ε with growth rate and annealing qualitatively supports the optical observations on hcp and fcc structure.
Temperature Effects on Whistler Resonance
Authors: Kent Gordon
Published: January 2005

The effects of longitudinal temperature on the index of refraction of the whistler mode are calculated. The theory involves an unusual assumption on the initial rf velocity, and as a consequence the problem is stated in terms of a singular integral equation. The integral equation is solved with no limitation on the analyticity of the distribution function. Numerical data are given showing the index of refraction as a function of magnetic field, with temperature as a parameter. The whistler resonance responses of two structures are presented, and a necessary condition for the observation of a whistler resonance in a one-dimensional warm plasma is derived. It is proposed that the whistler resonance could be used for plasma diagnostics in a discharge produced in a microwave cavity.
Helicon-Wave Propagation in InSb
Authors: Burke B. E. , Kino G. S.
Published: January 2005

Measurements have been made of the phase velocity and attenuation of helicon waves at microwave frequencies propagated along cylindrical samples of InSb at 77°K. Two of the modes of propagation (m = 0 and m = 1) were studied in two different samples. Experimental results are compared to a theory of Klozenberg et al., which takes into account the vacuum fields of the wave. Phase-velocity measurements are in good agreement with theory, but attenuation results are in some cases substantially lower due, in part, to displacement current effects neglected in the theory. No effects were observed when the electrons were subject to a pulsed drift field.
Calculations on the Collisional Coalescence of Gas Bubbles in Solids
Authors: Baroody E. M.
Published: January 2005

A largely analytical study is made of the collisional coalescence of spherical gas-filled pores similar to those involved in the swelling of nuclear fuel materials. Physical assumptions are essentially the same as adopted by earlier workers, and major attention is given to situations where pore mobility results from surface diffusion. The calculations are based on the integrodifferential equation for the distribution in radius ψ (r, t) and emphasize problems for which similarity (or self-preserving) solutions can be obtained readily. For these cases, ψ is a power of the time t multiplied by a function of a single variable G (η), where η = rtβ. It is found immediately that the pore density varies as t2β, and the moments 〈rn〉 as t−nβ. For two important problems, one finds β = −⅕ (random-migration coalescence) and β = −1 (biased-migration coalescence). Convenient procedures lead with little computation to estimates of the magnitudes of the lower moments. The estimates are good, as comparisons with the numerical studies of Gruber show. (A large discrepancy appears in an example, but is clearly the result of an incidental arithmetical error.) Limited results are also obtained on how a simple initial distribution goes over quickly to the similarity form. A few results are given for related problems, such as the coagulation by Brownian motion of liquid droplets in colloidal suspension. It is pointed out that some problems of interest for pore coalescence appear not to lead to solutions of the similarity type.
Substrate-Condensate Chemical Interaction and the Vapor Deposition of Epitaxial Niobium Films
Authors: Hutchinson T. E. , Olsen K. H.
Published: January 2005

Investigation of films formed by vacuum deposition of Nb on single-crystal MgO has demonstrated the importance of chemical interaction between the substrate and overgrowth in the epitaxial growth process. The interaction layer is composed of an oxygen-stabilized face-centered cubic modification of the normally bcc Nb, or the compund NbO, the thickness of which is controlled by the oxygen diffusion process in the layer. The previously observed nucleation-coalescence process of thin film formation is replaced by ordered chemical reaction. Defect-producing misorientations between nuclei, predominant in the nucleation-coalescence case, are not present in the ordered chemical reaction process. Thin films may thus be produced having defect density no higher than that of the substrate crystal. The effect of interaction between the substrate and condensate, although large in the example presented, should not be overlooked in other considerations of the epitaxial process where chemical reaction cannot be ruled out.
Spot Distortion Caused by Magnetic Deflection of an Electron Beam
Authors: Wang C. C. T.
Published: January 2005

When a focused electron beam is deflected by a transverse magnetic field through a small angle, the spot shape on the target is distorted. The electron density distribution within it also varies. A novel method of calculating and presenting the characteristics of the distorted spot is presented. The positions of the electrons at the incoming aperture are mapped into the target plane subsequent to the deflection. The resultant density distribution is plotted by the computer.
Simplified Analysis of Point-Cathode Electron Sources
Authors: Everhart T. E.
Published: January 2005

The accelerating field of a point-cathode electron source is divided into two regions, a diverging spherical-field region located in the immediate vicinity of the point cathode, and a converging-field region which occupies most of the cathode-anode space. Analysis of this model gives the Gaussian source size, axial position of the source, and spherical- and chromatic-aberration constants of the pointed-cathode electron gun. After including diffraction effects, the electron-optical parameters are optimized for minimum possible source size. The current density which appears to be emitted by the apparent source is introduced as a figure of merit for this type of electron gun, and the performance of field-emission and Schottky-emission pointed cathodes are compared. Source diameters below 100 Å are predicted for oriented-tungsten field-emission pointed cathodes, with apparent current densities exceeding 104 A/cm2; source diameter below 1000 Å are predicted for oriented-tungsten Schottky-emission pointed cathodes, with apparent current densities of approximately 100 A/cm2.
Wave-Optical Aspects of Lorentz Microscopy
Authors: Cohen Mitchell S.
Published: January 2005

The customary defocused and Foucault modes of Lorentz microscopy of magnetic films are usually described in terms of geometric optics. However, Wohlleben has shown that geometric optics has a restricted range of validity; a more fundamental approach is provided by wave optics. The defocused and Foucault modes may be discussed in terms of wave optics, and for the defocused mode, it can be shown explicitly that the geometric theory is simply the first approximation to the wave-optics theory. Consideration of wave optics also leads to the proposal of two additional modes of Lorentz microscopy: Zernike phase-contrast and interference microscopy; these modes cannot be described on the basis of geometric optics. The most fundamental problems in magnetic films which are amenable to study by Lorentz microscopy are investigations of the fine structures of domain walls and magnetization ripple. These problems are discussed in terms of wave optics for all four modes of Lorentz microscopy; in particular, the intensity distribution of the zero-width divergent domain wall is explicitly calculated for each mode. For practical experiments, the importance of coherence, i.e., of the illumination source size, is emphasized, and the experimental aid of holography is suggested. Since the Wohlleben limit is valid for all four modes, however, there is no resolution advantage inherent in any one mode. The choice of modes for solution of the domain wall and ripple problems therefore depends upon experimental convenience. It is concluded that the defocused mode seems most promising for practical application; Fresnel diffraction is preferred for the domain-wall problem, while Fraunhofer diffraction using low-angle electron-diffraction techniques is fruitful for the ripple problem.
Paramagnetic Resonance of Trivalent Iron in Single-Crystal Potassium Tetrafluoaluminate
Authors: Gladney H. M.
Published: January 2005

Single-crystal potassium tetrafluoaluminate-doped substitutionally with iron has been prepared. The room-temperature spectrum of isolated iron ions may be described by a conventional spin Hamiltonian with parameters: g∥=2.005, g⊥=1.999, D=0.1471 cm−1, a=0.0020 cm−1, and F=0.007 cm−1. From the linewidths an upper limit to the fluorine hyperfine structure is estimated.
Capacitance Changes in Thin CdS Crystals under dc Bias
Authors: Binggeli B. , Kiess H.
Published: January 2005

Appreciable increases in capacitance have been observed in thin single-crystal CdS platelets when measured under conditions of dc bias. Data have been obtained in the frequency range 20 cps-20 Mc/sec. Crystals could be roughly divided into two groups (denoted by I and II). Group I crystals, exhibiting an approximate V2 dependence of the I-V characteristic, showed low-frequency-capacitance increases of up to a factor of ten under bias. These changes could be explained in terms of SCLC. Group II crystals, exhibiting I-V characteristic with a voltage exponent much greater than two, showed low-frequency-capacitance increases of up to a factor of 1000. This behavior cannot be understood in terms of SCLC flow, and a two-layer model is proposed which provides a satisfactory explanation.
Theory of Plasma Transconductance due to Landau Waves
Authors: Derfler Heinrich , Simonen Thomas C.
Published: January 2005

We present here an N-pole circuit analysis of a network of parallel plane grids immersed in an isotropic hot-electron plasma. The associated self- and trans-impedances are expressed in terms of the discrete spectrum of electrostatic waves. Voltage-transfer ratios and transconductances between pairs of grid assemblies are calculated to study the feasibility of this scheme for launching and detecting Landau waves. Results show that widths of about 5 Debye lengths are optimum for modulator and detector gaps and that close-range transmission between gaps is predominantly due to the fundamental exponentially damped Landau wave.
Experimental Verification of Landau Waves in an Isotropic Electron Plasma
Authors: Derfler Heinrich , Simonen Thomas C.
Published: January 2005

We report here measurements of dispersion and damping of plane electrostatic waves having phase velocities between 1.5 and 3 times electron thermal speed 3×107 cm/sec. These waves were excited and detected at frequencies ωp<ω<2.5ωp using gridded rf probes within an isotropic, quiescent, and collision-free sodium plasma at thermal equilibrium. As plasma electron density (1×107 to 2×108 cm−3) and rf (30 to 180 MHz) are varied, the measured wavelengths and spatial damping rates were scaled to Debye length using independent Langmuir probe data. Full agreement is then found between the experimental results and the fundamental solution of Landau's dispersion relation.
A Cause and Cure of Stacking Faults in Silicon Epitaxial Layers
Authors: Pomerantz D.
Published: January 2005

In many applications of silicon epitaxial layers grown on silicon substrates it is necessary to oxidize the substrate and then remove the oxide prior to epitaxial deposition. This oxidation step is found to produce a greatly increased density of stacking faults in the deposit. This anomalous increase in stacking faults can be eliminated if the back (undeposited) substrate surface is treated either to abrasive processes such as lapping and scribing or to a boron-gettering process prior to oxidation. Both types of treatment are likewise found to eliminate saucer-like pits observed in oxidized slices after structural etching. The incidence of these pits is closely correlated with the incidence of stacking faults in the grown layer. It is concluded that the pits represent precipitates of fast-diffusing impurities and are probable nucleation sites for stacking faults.
Properties of Magnetic Materials with a Nonuniform Saturation Magnetization. I. General Theory and Calculation of the Static Magnetization
Authors: Schlömann Ernst
Published: January 2005

A general theory concerning the properties of magnetic materials having a nonuniform saturation magnetization is developed. In this theory, the local saturation magnetization and the local exchange interaction are assumed to vary in an arbitrary manner throughout the sample. It is further assumed that a dc magnetic field is applied which is sufficiently large to magnetize the sample substantially to saturation. The general theory is then specialized for a calculation of the static magnetization, assuming that the host material contains inclusions of a material with a different saturation magnetization. If all inclusions are fairly large, the effect of the exchange interaction becomes negligible and a result previously derived by Néel is obtained. The inclusion of exchange reduces the deviation of the magnetization from its saturation value, particularly at low values of the internal field. If exchange is neglected, this deviation becomes infinitely large at zero internal field. If exchange is included, however, the deviation remains finite. The theory is, therefore (for suitable materials), still approximately valid at remanence.
Electromagnetic Forces in Conductors
Authors: Dodd C. V. , Deeds W. E.
Published: January 2005

Relaxation-averaging formulas are derived for magnetic-induction problems involving axially symmetric fields with sinusoidal or pulsed time dependence in media which may be linear or nonlinear, homogeneous or inhomogeneous. Solutions have been obtained from a high-speed digital computer for time-harmonic fields in linear, inhomogeneous media. From these solutions, the electromagnetic forces are calculated and compared with experimental measurements. It is found that the computed and measured values agree quite well and that most of the discrepancy can be explained by the fact that the permeability of the ferrite used in the measurements was different from that assumed in the calculations.
Electrical Conductivity of Iodine-Doped Polyethylene
Authors: Swan D. W.
Published: January 2005

Measurements of the electrical conductivity of polyethylene film containing absorbed iodine are described and discussed. The influence of temperature, film thickness, iodine concentration, and voltage is examined. It is believed that carriers arise from a charge transfer between polymer molecules and the iodine. The results suggest that space charge is important.
Current Oscillations in Iodine-Doped Polyethylene at High-Field Strengths
Authors: Swan D. W.
Published: January 2005

With applied dc electric fields in excess of 1.2 kV/mil, the current in iodine-doped polyethylene is found to be no longer invariant with time, but to exhibit continuous oscillations superimposed upon a large background current. These oscillations appear at a well-defined threshold field, which is found to be independent of temperature, but to depend on the concentration of iodine in the film. The frequency of the oscillations is very temperature dependent, having an activation energy of almost the same value as the conductivity. Increase of iodine concentration increases the frequency, but the frequency decreases with increase of field strength. The frequency is also found to be inversely proportional to film thickness. Transient response characteristics suggest that the formation of space-charge regions may be important. The experimental results are compared with the theory of recombination waves in dielectrics, which considers the propagation of low-field domains through the sample.
Optical Determination of Cs Ground-State Depletion in Cs-Ar Low-Pressure dc Discharges
Authors: Bleekrode R.
Published: January 2005

The results of an experimental study of the absorption properties of Cs as present in Cs-Ar low-pressure discharges under various discharge conditions are presented. The total Cs concentration at zero discharge current was varied between 1.5 and 15×1012 cm−3. Absorption was measured in the 4555-Å and 8521-Å lines of Cs from which the stationary concentration of Cs (62S1/2) could be derived. Special attention was paid to determine the Cs concentration as the discharge changed from a low-burning voltage mode to a high-burning voltage mode. The pronounced variations of the discharge properties were found to be accompanied by rather drastic changes of the Cs concentration for which variations of a factor of ten or more were found.
Wave Propagation in a Beam-Plasma System
Authors: Bliman Samuel , Bouchoule André
Published: January 2005

A nonquasistatic treatment is established in order to study wave propagation along beam-plasma systems in the presence of a dc magnetic field. Solutions to the dispersion equations are given for two cases: The column completely fills a cylindrical waveguide, or it is in an infinite dielectric (vacuum). The results are compared qualitatively to those already obtained by various authors for the same conditions by a quasistatic analysis.
Nonradiative Relaxation Time between 4T1, 2 and 2E States in Ruby
Authors: Pollack S. A.
Published: January 2005

The R-line fluorescence in ruby was excited with the nanosecond light pulses, and the slope of the rise curve was studied as a function of the pulse width at room temperature. The purpose of the experiment was to determine the value or the upper limit of the nonradiative relaxation time between the pump bands 4T1, 2 and the fluorescence state 2E. The upper limit of 5 nsec was determined. A brief review of previous work is given.
Electrical Properties of Cr-SiO Cermet Films
Authors: Lood D. E.
Published: January 2005

The Hall coefficient, temperature coefficient of resistance, and conductivity of Cr-SiO cermet films were measured as a function of film composition. The behavior of the Hall coefficient indicates this material should be treated as a two-carrier system. A model is proposed which may account for this behavior and for the dependence of the temperature coefficient of resistance on small concentrations of SiO.
Position and Waveform of Light Emission in Reverse-Biased GaAs Diodes
Authors: Yamada Shoji , Araki Tohru
Published: January 2005

The light emission from reverse-biased GaAs p-n junctions was investigated using current pulses. Appreciable light emission was obtained only in the breakdown range. Light-emission waveform had three components, i.e., emission waveform of nearly the same shape of current pulse (first component), emission wave delaying about 2 μsec from the onset of current pulse (second component), and unstable emission peak near the last part of the current pulse (third component). For the first component, the position of the reverse-biased emission was the same as that of the forward-biased emission. The light of the second component was emitted from n-type region of the diode, and this component will occur from the saturation of recombination rate near the junction. The third component was emitted from the relatively wide range of the n-type region containing p-n junction, and this emission peak is the phenomenon preceding the destruction of the diodes.
High-Field Hall Coefficient in a Compensated, Multiband Conductor
Authors: Allgaier R. S.
Published: January 2005

The theory of the magnetic-field dependence of the Hall coefficient in a simple, multiband model is reviewed. The complete expression rapidly becomes more complicated as the number of bands increases. Simple limiting forms, valid for any number of bands, have been derived earlier for weak magnetic fields, and for the high-field limit when there is no compensation (i.e., when the electron and hole concentrations are not equal). It is shown that a simple result also occurs in the high-field limit, with compensation, for any number of bands.
Solution of Ginzburg-Landau Equations for Arbitrary Tangential Magnetic Fields and Experimental Verification
Authors: Alphonse Gerard A. , Bergstein Leonard
Published: January 2005

The Ginzburg-Landau equations are solved for thin superconductors in the presence of arbitrary tangential magnetic fields and yield an essentially position-independent order parameter if the superconductor contains no vortices. The magnetic transition is always first order unless the field is symmetrical on the surface; if the field comes from a superposition of external source and transport current, the critical order parameter Φc is a one-third power function of the current. It is shown that the physical conditions for the above solution can be realized with a superconducting transmission line, and that the order parameter is directly measurable in terms of the resonant frequency of the line. The measurements made on tin samples at temperatures down to 0.6Tc show excellent agreement with the theory, and constitute an experimental vertification of the latter.
Superconductivity in Thin Indium Films
Authors: Vogel H. E. , Garland M. M.
Published: January 2005

Superconducting indium films are studied to determine the effect of film thickness on transition temperature in the range of thicknesses from about 100 to about 1000 A. Films of varying thicknesses are produced by vacuum deposition onto z-cut quartz substrates. To ensure reproducibility, films are produced in groups of five. Comparisons are made with the theoretical models of Toxen and Strongin et al., and the effect of electron mean free path is calculated in an approximate manner. In addition, an effective electron-phonon coupling constant is obtained for the surface-layer model.
A Theoretical Interpretation of the Contour and Symmetry of Switching Transients in Ferroelectric Crystals
Authors: Gonzalez-Ibeas J.
Published: January 2005

Analytical expressions are developed for obtaining the form that would correspond to the switching-current pulse of a ferroelectric, if the transit time were non-negligible. In such a case, two important factors controlling the switching would be: (a) the share of surface area switched by direct nucleation of domains, and (b) the transit velocity of domains walls through the crystal. An experimental switching transient can be characterized by two adimensional data: the expression (im·tm)/(2Ps) and the ratio (change of polarization before the maximum of the current pulse)/(change of polarization after such a maximum). Using these two data as coordinates, a switching pulse can be represented by a point on an x−y plane. From our analytical expressions, a network is plotted on the x−y plane, relating directly the shape of a current pulse to the factors controlling the switching, according to our theory. The method is illustrated using several oscillograms of switching pulses appearing in the literature.
Photoelastic Properties of Selected Materials and Their Relevance for Applications to Acoustic Light Modulators and Scanners
Authors: Dixon R. W.
Published: January 2005

Measurements of the photoelastic tensor components and figures of merit of several materials selected for possible application in acoustic light modulators and scanners are presented. The most important results are that GaP is superior to fused quartz by nearly two orders of magnitude for modulation and scanning of visible light of wavelength longer than 0.58 μ, and that GaAs is similarly superior at wave-lengths longer than about 1 μ.
Microwave Rectification using Piezoelectric Quartz and Zinc Oxide
Authors: Carr Paul H. , Slobodnik Andrew J.
Published: January 2005

A theoretical and experimental study was made of the rectification of microwave energy by a thin piezo-electric disk placed in a ∼3-GHz reentrant cavity. Using a one-dimensional approximation, an equivalent circuit consisting of a frequency-dependent voltage source in series with a capacitance was derived for the rectified output. The voltage is the sum of a coherent part, proportional to the nonlinear coefficients of the constitutive relations and to the Maxwell—Faraday stress, and a thermal part, proportional (for quartz) to the coefficient of thermal expansion. The risetime for the coherent voltage at an overtone acoustic resonance frequency was about 1 μsec, while that for the thermal heating was of the order of milliseconds. The rectified voltage is proportional to the microwave power and is typically mV/W when polished X-cut disks are excited at acoustic resonance frequencies and one to two orders of magnitude smaller at other frequencies. No acoustic resonance was observed for C-cut zinc oxide, and a nearly frequency-independent value of 20 mV/W was measured.
Intensity Fluctuations of the Radiation from a Dispersive Blackbody
Authors: Osborn R. K. , Akcasu A. Z.
Published: January 2005

Statistical properties of the output fluctuations of a photon detector measuring the intensity of radiation at a given frequency emitted by a dispersive blackbody are investigated using Langevin's technique. The variance-to-mean ratio of the accumulated counts, and the power spectral density of the count rate are obtained in terms of properties of the emitting medium. The possibility and limitations of obtaining information about the emitter by measuring these quantities are discussed. It is found in particular that the temperature of the emitting medium can be determined in principle by observing the intensity fluctuations of the radiation at a single frequency. The photon fluctuations in a microwave cavity are also discussed in the framework of the present formalism and compared to previous work.
Cobalt-Doped TlMnF3, a Zero Anisotropy Cubic Antiferromagnet
Authors: Eastman D. E. , Shafer M. W. , Figat R. A.
Published: January 2005

Single crystals of cobalt-doped thallium manganese fluoride (TlMn1−xCoxF3) have been studied by antiferromagnetic resonance for cobalt concentrations of 0≤x≤0.001. In this range the antiferromagnet remains cubic at 4.2°K, with its crystalline anisotropy varying linearly with cobalt concentration from K1/M = −5.1 Oe for pure TlMnF3 to +8.2 Oe, passing through zero for x=0.0004. Other magnetic properties, such as Néel temperature and exchange field, are unaffected by the small cobalt concentrations. Multiple non-equivalent equilibrium spin-orientation states, which have been observed in spin-flopped resonance in the 〈100〉 and 〈110〉 crystal planes when K1/M is greater than zero, are described.
Preparation and Properties of Eutectic Bi-MnBi Single Crystals
Authors: Yim W. M. , Stofko E. J.
Published: January 2005

Single crystals of Bi containing ordered MnBi filaments (∼4% by volume) have been grown by a zone-melting technique in the presence of a longitudinal magnetic field. Metallographic and x-ray examinations showed that the long axis of the MnBi needles (∼4 μ in diameter and ∼200 μ long) was aligned along the preferred growth direction, which is perpendicular to the trigonal axis, of the single crystalline Bi matrix. The long axis of the needles is the c axis of MnBi, the direction of easy magnetization. These needles rendered the eutectic Bi-MnBi crystal ferromagnetic with a strong magnetic anisotropy, as revealed by magnetic moment measurements. The dependences on temperature and magnetic field of its electrical and thermal properties were essentially the same as those of pure Bi, which is a nonmagnetic semimetal. Thus, a controlled growth technique has been used here to achieve an ordered structural arrangement that combines the properties of semimetals and ferromagnetics into a single material.
A Similarity Principle for Multipacting Discharges
Authors: Woo Richard , Ishimaru Akira
Published: January 2005

A similarity principle is introduced for multipacting discharges in geometrically similar electrode configurations. For phase-similar breakdowns, it is shown that the rf and dc voltages are proportional to (fl)2, the electron velocity is proportional to fl, and the rf and dc magnetic fields are proportional to f, where f is the frequency of the rf voltage and l is the characteristic length for similar configurations. If the electron kinetic energy is similar as well, fl must also be invariant. These similarity relations are applied to previous work in parallel plates, and it is shown that the results of the different multipacting cases can be unified under the similarity principle. A physical explanation is also given for the success of the constant vf/vi assumption, where vi and vf are the respective emission and impact electron velocities. When applied to geometries other than parallel plates, the similarity principle yields important scaling information and allows prediction of the breakdown behavior in these geometries, where analytical solutions are otherwise not available.
High-Pressure Apparatus for Optical Studies at 77°K
Authors: Offen H. W. , Tanquary R. L. , Sterrett K. F.
Published: January 2005

A high-pressure optical cell, modeled after the Drickamer cell I, has been developed for absorption and luminescence in the 0–40 kbar and in the 77°–383°K ranges. The windows consist of a NaCl-sapphire combination in order to retain transparency down to 77°K. The window transmission varies as a function of temperature and/or pressure between tolerable limits. The largest contribution to nonreproducible errors in intensity measurements arises from the sample—salt interfaces. The pressure scale has been approximately determined at low temperatures by means of sudden changes in light transmission during the KCl phase transformation around 20 kbar. The liquid—solid phase transition in heptane is also studied.