bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Hardening of Polycrystalline Copper, Nickel, and Aluminum
Authors: Hartmann R. J.
Published: April 2005

Fatigue hardening of polycrystalline copper, nickel, and aluminum has been determined by measuring the changes in the area of the hysteresis loop. It can be described as a superposition of two types of hardening, called VI and VII. These two types can far better be resolved by the specific irreversible work of deformation than by the increment of subsequent stress amplitudes.

Hardening VI occurs mainly at high strain amplitudes and is not peculiar to fatigue. Saturation (I) is reached between N=10 and N=104, depending on strain amplitude and stacking fault energy.

Hardening VII is effective only at low and medium strain amplitudes. It is characterized by a very low hardening coefficient. Saturation (II) is reached between N=104 and N=106.

Intermediate overloading during saturation (II) results in a pronounced softening, indicating that hardening VII is caused by the production of small-scale obstacles.
Coupled-Modes Analysis of the Phonon-Photon Parametric Backward-Wave Oscillator
Authors: Bobroff D. L.
Published: April 2005

Because of the phenomenon of electrostriction, the passage of an intense laser beam through a medium can lead to a parametric backward-wave interaction in which one of the two waves (signal and idler) is an acoustic wave and the other an optical wave. This paper analyzes this effect and determines the conditions necessary for backward-wave oscillations to occur. The time rate of build-up of the oscillations when these conditions are satisfied is determined. The behavior of the system as an amplifier of acoustical and optical energy is also determined.
Liquid-Nitrogen Cooling of a Ruby Rod
Authors: Mickey D. L.
Published: April 2005

Numerical solutions of the one-dimensional heat-flow equation have been obtained for a liquid-nitrogen end-cooled ruby laser rod. Temperature distributions, cooling times, and heat fluxes have been obtained for four initial rod temperatures from 150° to 350°K.
Role of MnO Substrates in Enhanced Photoemission from Cs3Sb
Authors: Wooten F.
Published: April 2005

Manganese oxide films are frequently used as substrates for Cs3Sb photocathodes prepared on glass windows. Such photocathodes have significantly enhanced sensitivity at wavelengths in the range 5500–6500 Å. Photovoltaic and photoemission measurements indicate that the enhanced photosensitivity results from band bending in the Cs3Sb at the MnO substrate interface. Band bending provides an electrostatic field, which reduces the barrier height for photoemission from near the substrate.
Interaction between a Dislocation and an Assembly of Dislocation Arrays
Authors: Johnson H. H. , Webster L. D.
Published: April 2005

The force exerted upon a lone dislocation by an assembly of dislocation arrays is discussed in the continuum approximation. The arrays are parallel and in equilibrium with a constant applied stress, but no further restrictions are imposed.

For both edge and screw dislocation arrays, the force parallel to the glide planes can exhibit absolute maxima and minima only at the glide planes, and the sign of the force throughout the medium is governed by the distribution functions evaluated at the glide plane ends. Some numerical results in agreement with the analysis are given for screw dislocations upon two parallel glide planes; a ``shadow effect'' is also demonstrated for this case. The analysis is also valid for the interaction between a dislocation and an assembly of parallel cracks.
Chemisorbed Coincidence Lattices on Rhodium
Authors: Tucker Charles W.
Published: April 2005

The previous low-energy electron diffraction (LEED) work of the author on coincidence lattices formed by chemisorbed monolayers is extended to include two new structures, one formed by oxygen and the other by CO, on the (100) face of Rh. These structures are analyzed and found to be coincidence lattices, that is, high-coverage structures which are out of step with the substrate lattice in particular crystallographic directions but come into coincidence with it every several substrate lattice positions. The oxygen structure forms a slightly distorted close-packed arrangement which is out of step in the Rh [11] direction by 1/7 of the Rh-Rh separation. The CO structure is out of step in the Rh [10] direction by ⅙ of the Rh face-centered unit cell. It is concluded that the coincidence lattice is a general type of chemisorbed structure and that contrary to the general presumption, and particularly for high-coverage structures, the chemisorbed species do not always reside in positions of simple coordination with respect to the substrate.
Low-Energy-Ion-Bombardment Damage in Germanium
Authors: MacDonald R. J. , Haneman D.
Published: April 2005

The depth of damage induced in Ge films by ions of energies of 200–1000 eV has been measured for He, Ne, Ar, and Kr bombardment, the depth decreasing for heavier ions. The effects exhibit saturation at critical ion dosages. From the results the damaged layer is deduced to consist of two main regions. The one nearer the surface consists mainly of lattice disorder plus trapped gas, which extends to a depth of approximately 10 atomic layers at 1000-eV ion energy. The second, lower region consists mainly of gas atoms trapped in the relatively ordered lattice, the depth of this region increasing with decreasing ion mass. It is concluded that focused atom emission observed in diamond-type lattices is due to the undisturbed surface region structure and focusing is weakened by the damage induced by ion bombardment.
Gallium Arsenide Surface Structure and Reaction Kinetics: Field Emission Microscopy
Authors: Arthur J. R.
Published: April 2005

GaAs field emission cathodes giving symmetric and reproducible emission patterns were prepared by chemical etching and low-temperature field desorption. Both electron and hydrogen ion images were obtained, although the latter showed little detail since field etching was rapid in the presence of hydrogen. Distinct differences were observed in the emission patterns and surface behavior between tips oriented in the [111] direction and tips oriented in the [1̄1̄1̄] direction. Surface migration of both Ga and GaAs was more rapid on the (1̄1̄1̄) B or As face which became thermally disordered above 300°C. The (111) A face remained ordered up to 400°C. On both faces adsorbed Ga decreased the work function by ∼0.5 V while adsorbed As reduced the emitting area without altering the work function appreciably. Heating the emitters above 500°C permanently altered the emission characteristics which then became strongly light sensitive. This was evidently due to doping changes by impurity diffusion.
Thermal Surface Impedance for Plane Heat Waves in Layered Materials
Authors: Green Donald R.
Published: April 2005

Thermal surface impedance is defined as the ratio of temperature to heat flow for plane steady-state sinusoidal heat waves at the surface of a sample. The general analytical expression relating thermal surface impedance of a two-layer material to the thermal properties of the layers and the conductance of the joint between them is given. Computed values for the special cases of two layers in perfect contact and of a single layer are graphically presented. Experimental data supporting the graphic presentation were obtained with a novel thermal transducer method. The close theoretical relationship between the sinusoidal steady-state impedance and transient behavior is also briefly discussed.
Giant-Pulse Laser Activity in Neodymium-Doped Silicate Glass: The Energy Conversion Process
Authors: Wenzel J. H.
Published: April 2005

An experiment is reported which relates the gain characteristics of the pulsed mode in a neodymium-doped silicate glass laser to the giant-pulse laser energy output. In this experiment optical pumping of both the pulsed and giant-pulse mode occur in a time short compared to laser atom metastable lifetime.

An analysis of the experimental data shows that pulsed-mode gain characteristics can be related to the giant pulse energy output through the use of a model for the giant-pulse laser similar to that derived by Wagner and Lengyel provided that corrections are included to account for the effects of resonator standing waves and gain variations across the radius of the laser rod.
Optical Properties of Thin Germanium Films in the Wavelength Range 2000–6000 Å
Authors: Grant Paul M. , Paul William
Published: April 2005

Measurements have been made of the normal incidence reflectivity and transmissivity coefficients R and T of thin germanium films. Films were deposited in vacuo on fused quartz substrates where the crystalline perfection of the film was controlled by varying the substrate temperature so that the effect of crystalline order on reflectivity could be observed. Epitaxial films were grown on cleaved CaF2 substrates to thicknesses in the range 100–3000 Å. Structure in the reflectivity and transmission spectra showed these films to possess bulk band properties. However, the amplitudes of R and T were affected by the presence of film surface roughness believed to originate from nucleation and growth phenomena. Also, compressive strain induced by the difference in thermal explansion coefficients between Ge and CaF2 shifted interband transition structure to slightly higher energies. Values of the optical constants were deduced from R and T. When experimental and calculational difficulties peculiar to the film method are accounted for, the results correspond closely to those of the Kramers-Kronig analyses of bulk reflectivity data.
Plastic Deformation of Spinning Iron Whiskers
Authors: Piotrowski W. L. , Larson D. C. , Beams J. W.
Published: April 2005

Single-crystal iron whiskers are plastically deformed centrifugally with no gripping constraints. A calculation of the stresses in a rotating body with a square cross section is given which allows a determination of the resolved shear stresses in the whiskers at their yield points. The stresses obtained are intermediate between the bulk values and the smaller whisker values as expected. The average critical resolved shear stress was 6.8 kg/mm2 for all the whiskers except three which yielded at a somewhat lower stress of 4.1 kg/mm2. For whisker widths ranging from 310 to 820 μ, no systematic dependence of yield stress on size was found.
Thermal Conductivity of SnTe between 100° and 500°K
Authors: Damon D. H.
Published: April 2005

The thermal conductivity, electrical conductivity, and Seebeck coefficient of several specimens of SnTe have been measured between 100° and 500°K. The thermal conductivity is weakly dependent on both temperature and hole concentration. The total thermal conductivity is separated into an electronic and a lattice thermal conductivity. Because of the large concentrations of Sn vacancies in the samples, the phonons are scattered both by three-phonon umklapp processes and by the Sn vacancies; this results in a lattice thermal conductivity that varies with temperature more like T−½ rather than T−1. The Lorenz number relating the electrical conductivity and the electronic thermal conductivity is an unusual function of hole concentration. The Lorenz number is larger than the Sommerfeld value L0, varies with hole concentration p, and has a maximum value of about 1.3 L0 at p=2×1020 cm−3. This is consistent with the variation of the electrical conductivity and the Seebeck coefficient with hole concentration.
Electromagnetic Scattering by Obliquely Oriented Cylinders
Authors: Lind Arthur C. , Greenberg J. Mayo
Published: April 2005

Numerical results for scattering coefficients and extinction efficiencies for obliquely oriented infinite circular cylinders with index of refraction m=1.6 are presented. The extinction efficiencies for oblique incidence have a much more intense resonance structure than those for normal incidence. An analysis is made of these resonance modes for large angles of incidence and comparison is made with the propagation modes in cylindrical dielectric waveguides. A polarization reversal via extinction is noted for thin cylinders with sufficient tilt angles. By comparison with preliminary experimental results on finite cylinders it is shown that the theoretical solution for infinite cylinders may be usefully applied to the finite case as long as the angle of incidence of the radiation is small.
Stability of Crossed-Field Electron Beams
Authors: Buneman O. , Levy R. H. , Linson L. M.
Published: April 2005

The stability of crossed-field electron beams is treated for arbitrary values of the parameter q=ωp2/ωc2 = (plasma frequency/cyclotron frequency)2. The theory bridges a gap between existing theories applicable for q«1 and for q=1. For wavelengths longer than about five beam thicknesses an instability occurs with a growth rate not exceeding ∼¼qωc. It can be shorted out by conducting walls, or else one can prevent long wavelengths in closed (cylindrical or toroidal) beam geometries. For wavelengths shorter than roughly 6q beam thicknesses a cyclotron instability occurs with a growth rate ∼½qωc exp(−2/q). This becomes practically unimportant for q⪝0.2. Observations support these theoretical results.
Electron Beams from a Duoplasmatron using a Hollow Cathode Arc as Electron Source
Authors: Roberts A. S. , Cox James L. , Bennett Willard H.
Published: April 2005

A high-density electron source was obtained by a modification of the duoplasmatron which employed a hollow cathode discharge (HCD). An electrostatically shielded and water-cooled Faraday cup probe was developed for use in measuring the radial current density distributions of electron beams obtained from this source. These electron beams, formed in a high-vacuum drift space, were found to have symmetrical current density distributions. Under certain conditions, spherical aberration of the beam was observed.
Demagnetizing and Stray Fields of Elliptical Films
Authors: Chang H. , Burns J.
Published: April 2005

The magnetostatic fields inside and outside of a ferromagnetic thin film, called demagnetizing and stray fields, respectively, are known to be calculable from the model of a uniformly magnetized flat ellipsoid. In this paper, these fields are plotted as functions of the spatial coordinates with the aspect ratios b/a and c/a as parameters. The information is applied to a number of magnetic thin-film device and physics problems.

Demagnetizing fields influence wall motion threshold, shape anisotropy, and the stability of domain configuration. Stray fields affect the creeping and switching thresholds of memory elements in an array. The effectiveness of demagnetizing field reduction in a film pair dictates the drive line configuration. In films coupled magnetostatically or by exchange force, the planar components of stray field are important in determining both the quasistatic and dynamic magnetization reversals. However, the normal component of stray field, being much smaller than the normal component of demagnetizing field, has no significant effect on switching.
Magnetic Switching in Ni-Fe Single-Crystal Films
Authors: Lo D. S.
Published: April 2005

Quasistatic magnetic switching in Ni-Fe single-crystal films for different orientations of the reversal fields were studied both experimentally by Lorentz microscopy and theoretically. It was found that the switching processes can be explained quantitatively by a theory combining the Stoner-Wohlfarth rotational switching curve and the theoretical wall motion switching curve derived in this paper from a simple model. Eight typical switching processes are illustrated by Lorentz micrographs with explanation for two types of films; one type has a higher ratio of coercive force to biaxial anisotropy field than the other. Both wall motion switching and rotational switching were observed. In some cases, the complete switch takes place in two separate consecutive stages, each stage corresponding to a different easy axis direction 90° apart, each stage being by a different switching mechanism. Cross-tie walls were observed in single-crystal films in the proper thickness range. Although the films studied had nearly zero magnetostriction and a good single-crystal structure, all films exhibited magnetization ripple in the Lorentz micrographs.
Shock Propagation in Nonreactive Porous Solids
Authors: Linde Ronald K. , Schmidt David N.
Published: April 2005

Shock propagation and attenuation have been studied in porous graphite and aluminum foams (40% to 80% of crystal density). The effects of such material parameters as particle (or pore) shape, size, and size distribution on response of the materials to shock loading were investigated, and Hugoniot measurements below 25 kbar were made. It was found that in the pressure and porosity range studied, the ``compacted'' volumes for pressures above a few kilobars are essentially those of the solid materials at the same pressure. The densities of specimens of aluminum foam recovered after shocking to about 10 kbar correspond approximately to that of solid aluminum, while the densities of recovered specimens of ATJ graphite are very close to their initial densities, even after shocking to 50 kbar. An artificial viscosity computer code has been successfully adapted to calculation of shock attenuation in porous solids. Within the idealizations of the models employed, calculated transit times and shock profiles are in reasonably good agreement with the experimentally measured quantities.
Decoration of Semiconductor Surfaces for Electron Microscopy by Displacement Deposition of Gold
Authors: Coutts Maurice D. , Revesz Akos G.
Published: April 2005

The electrochemical displacement plating of gold on silicon in an HF solution has been studied by electron microscopy using a transfer replica technique. The gold deposits begin as localized nuclei whose diameters are equal to or less than 20 Å. At this stage of the plating process the gold nuclei show a preferred orientation corresponding to that of the substrate. During subsequent growth the orientation becomes random. The dissolution of silicon, which accompanies the deposition of gold, is generally independent of crystallographic directions and occurs in a random manner around the gold nuclei. Some p-type specimens, however, reveal an oriented etch pattern. The preferred nucleation of gold at surface defects is demonstrated on cleaved specimens where the cleavage steps act as preferred sites for the nucleation. These steps sometimes form bands. Between the single steps or bands there are flat regions of random nucleation whose width can be as large as 2 μ. The nucleation density on these regions is the same as that on chemically polished specimens and is high, on the order of 1011−1012 cm−2. The preferred sites for nucleation, with the exception of surface defects, are probably related to surface states. The nucleation kinetics resemble an adsorption process. The growth is diffusion-limited and the particle diameter is roughly proportional to the cube root of time.
Low-Frequency Oscillations in CdS Single Crystals
Authors: Yasukawa Takeshi , Yoshizawa Michio , Ibuki Sumiaki
Published: April 2005

Low-frequency current oscillations in CdS single crystals were observed. One type of oscillations was a damped one, and the other type of oscillations was continuous and only observed under superposed infrared light which produces quenching. The retrapping rate of the free holes and the occupation probability among the traps control the free electron density oscillation.
Noble Gas Plasma Produced by Fission Fragments
Authors: Leffert Charles B. , Rees David B. , Jamerson Frank E.
Published: April 2005

The generation of a plasma by fission-fragment ionization of noble gases is reported. The experimental data consist of steady-state current-voltage (I-V) characteristics obtained with ceramic-metal ionization tubes which were operated in the high neutron flux region of a nuclear reactor. The observed dependence of I on V½ for applied potentials <100 V is shown to be consistent with the theory that the predominant charge loss in the plasma is volume recombination of diatomic ions and electrons. The ion generation rate is calculated from the energy loss rate of the fission fragments in the gas and I-V characteristics for the noble gases are computed. These characteristics, which do not contain any adjustable parameters, are in agreement with the experimental data within±10%. Data are presented for neon, argon, xenon, and neon-argon (Ar/Ne=10−3) for gas pressures in the range 30 to 400 Torr. Typically, for a gas pressure of 240 Torr and a neutron flux of 1013 cm−2·sec−1, the computed values for ion generation rate and electron density in the pure gases were ≈5×1016 cm−3·sec−1 and ≈3×1011 cm−3, respectively. For the neon-argon mixture, the electron density was estimated to be ≈7×1011 cm−3. This higher density arises not only because of additional production of Ar+ ions via neon metastables encountering argon neutrals, but also because of a reduction in the formation rate of Ar2+ ions (followed promptly by dissociative recombination). The point is that Ar++Ar+Ne→Ar2+ is unlikely compared with Ne++2Ne→Ne2+, for a small argon admixture.
Electron Emission from Aluminum after Quenching
Authors: Claytor R. N. , Gragg J. E. , Brotzen F. R.
Published: April 2005

Emission of electrons (``Exo-electrons'') from aluminum was observed by an openwindow Geiger-Müller counter after quenching from temperatures between 300° and 450°C. Emission rates as a function of time at room temperature agreed well with data calculated on the basis of a model involving the diffusion of point defects toward the surface. The energy of formation for the process was determined and discussed in terms of point imperfections.
Optical Properties of Copper Oxide Films
Authors: Wieder Harold , Czanderna A. W.
Published: April 2005

The transmittance and reflectance of CuO0.67 and CuO films ranging in thickness from 392 to 2335 Å have been measured in the wavelength region of 400 to 800 mμ. These data were used to obtain the wavelength dependence of the optical constants of these materials. Differences between the optical properties of CuO0.67 and Cu2O are attributed to differences in stoichiometry rather than to size effects. A method for measuring absolute reflectance is described.
Nonlinear Laser Noise and Coherence
Authors: Fleck J. A.
Published: April 2005

The effect of spontaneous emission noise on the coherence properties of a laser operating above thresbold is considered on the basis of a noise-driven van der Pol oscillator model. The oscillator constants are derived from the theory of Lamb. The noise function is represented as a sequence of randomly phased, damped sine pulses with a Doppler spread of frequencies. The noise function is normalized on the basis of equilibrium considerations at positive temperatures. The nonlinear linewidth, intensity fluctuations, and intensity correlation function are derived.
Laminar Elastico-Viscous Flow in Channels with Porous Walls
Authors: Mishra Shankar Prasad
Published: April 2005

The laminar flow of an elastico-viscous liquid in a channel having a rectangular cross section and two equally porous walls is discussed in this paper. The fluid dynamical equations have been solved to obtain a complete description of the fluid flow in the channel. The solution of the flow equations leads to detailed expressions for the dependence of the velocity components and the pressure on position coordinates, channel dimensions, and fluid properties.
Magnetic Field Distribution in a Type II Superconductor
Authors: Cline H. E. , Rose R. M. , Wulff J.
Published: April 2005

Direct measurements of the magnetic field distribution in the gap between half-ellipsoids of niobium in plastically deformed and annealed states were made using a bismuth thin-film magnetoresistance probe. An empirical equation of the form r−r0=C0B+C1 (eC2B−1) for the field distribution in the deformed sample was found. For the annealed sample, a surface discontinuity of the field was observed, which is a boundary condition for the equilibrium magnetization. Flux jumping was observed when the field was not increased slowly. The distribution in the annealed specimen had reproducible irregularities.
Low-Energy Electron Diffraction Study of the Adsorption of Cesium on the (111) Surface of Si
Authors: Gobeli G. W. , Lander J. J. , Morrison J.
Published: April 2005

Low-energy electron diffraction studies of the system Si(111)+Cs in the concentration range from zero to one monolayer of cesium have been made on freshly cleaved and on annealed samples of silicon at room temperature. The cleaved surfaces produce three ordered phases depending on coverage. The annealed clean surface (which is reconstructed) did not exhibit a characteristic ordered phase anywhere in the concentration range. Measurements of the dependence of work function on concentration and on desorption with increased temperature were correlated with photoelectric emission and work function measurements reported by Gobeli and Allen.
Determination of Electron Trapping Parameters
Authors: Bube Richard H. , Dussel Gustavo A. , Ho Ching-Tao , Miller Lewis D.
Published: April 2005

A detailed investigation of different methods for determining electron trap parameters has been made on crystals of CdS-CdSe. The principal techniques involved are decay of photoconductivity and thermally stimulated conductivity (TSC). Direct evidence of a quasicontinuous trap distribution with total density of 5×1015 cm−3, trap depth range of 0.1–0.7 eV, and capture cross sections of the order of 10−16 cm2 is obtained, for which correct values of the parameters can be calculated from Fermi-level analysis of either decay or TSC data. In the same crystals a discrete trap level with density of 2×1014 cm−3, depth of 0.73 eV, and apparent cross section of 10−14 cm2 is also found. In spite of the large value of cross section derived from the freeing of trapped electrons, these traps exactly obey monomolecular kinetics. A temperature threshold at 180°K is found, below which it is not possible to fill these traps. Examination of a number of possibilities favors the proposal that these traps are characterized by a Coulomb-repulsive barrier.
Compositional Uniformity of Ni–Fe Films
Authors: Ahn K. Y. , Beam W. R.
Published: April 2005

Large compositional variations reported in thin evaporated nickel-iron films by Chu, Wolfe, and Wagner have not been observed in three new independent microprobe studies. Apparent compositional variations in the vicinity of isolated lumps of material are explained via thickness dependence of the nickel-iron count ratio.
Light Emission Associated with Growth Defects from Reverse-Biased GaP p-n Junctions
Authors: Gershenzon M. , Ashkin A.
Published: April 2005

Diffused junctions prepared from GaP grown by the rotating floating-zone technique exhibit microplasma breakdown and accompanying light emission at 298°K at defects due to dislocations and a precipitated second phase. At 77°K this mechanism does not occur in the same bias range. Instead, at higher reverse bias, breakdown and light emission occurs from many spots which form a gross spiral pattern when the junction plane is normal to the growth axis. The breakdown regions correspond to local fluctuations in impurity concentrations produced during growth, these fluctuations being introduced at one point during each rotation of the floating-zone ingot. The shape of the solid-liquid interface during growth agrees well with that predicted from the dimensions of the spiral pattern and the growth parameters.
Magnetic Decay in a Hollow Elliptic Cylinder
Authors: Weinstein M. A.
Published: April 2005

An exact formula is obtained for the relaxation time of an axial magnetic field in an infinitely long conducting cylinder whose cross section is bounded by two confocal ellipses. Approximate formulas are given for thin-walled cylinders and for nearly circular cylinders. The discontinuity in the relaxation time at the transition to a solid elliptic cylinder is discussed and calculated. Some numerical values are given.
Third-Order Elastic Coefficients of Quartz
Authors: Thurston R. N. , McSkimin H. J. , Andreatch P.
Published: April 2005

All 14 third-order elastic coefficients of quartz have been calculated from the measured transit times for small-amplitude ultrasonic waves as functions of applied stress. Thirty-four different experimental runs were made, ten under hydrostatic pressure, and 24 under uniaxial stress. The data permit calculation of the 14 coefficients with 20 crosschecks. Our recommended values at 25°C, based on a least-squares fit, are as follows, all in 1012 dyn/cm2. CoefficientValueStandard errorC111−2.100.07C112−3.450.06C113+0.120.06C114−1.630.05C123−2.940.05C124−0.150.04C133−3.120.07C134+0.020.04C144−1.340.07C155−2.000.08C222−3.320.08C333−8.150.18C344−1.100.07C444−2.76 0.17.
Effect of Magnetic Field on Resonances of Surface Waves Propagating along a Cylindrical Plasma Column
Authors: Akao Yasuo , Ida Yoshio
Published: April 2005

The effect of axial magnetic field on the resonances of surface waves propagating along a cylindrical plasma is examined. When the magnetic field is increased and the exciting frequency maintained constant, the resonance peaks in the symmetric mode are shifted towards the lower discharge current side whereas the peaks in the dipolar mode split into two peaks with increasing separations. A method for determining plasma density by use of surface wave resonances is thus extended to the case of magnetoplasma columns.
LEED Beam Broadening as a Result of Sputtering Damage
Authors: Park Robert L.
Published: April 2005

Investigations of sputtering damage based only on changes in LEED intensities are unable to distinguish between lattice distortions resulting from bombardment atoms imbedded in the lattice and localized structural defects such as vacancies. Such a distinction can be made on the basis of beam broadening. The observed beam broadening due to bombardment of a clean annealed (100) nickel surface with 500-eV argon ions can be accounted for by assuming that a strain of 0.05 is introduced by occluded argon atoms. As a result of the finite beam width, plots of the intensity of the beam as a function of electron energy are affected by the mechanics of recording and reducing the data. It is shown that the correct intensity can be obtained regardless of beam width by superimposing plots of collector current versus electron energy for all values of the collector angle.
Effect of Carrier Traps in Polyethylene under Gamma-Ray Irradiation
Authors: Yahagi Kichinosuke , Shinohara Kenichi
Published: April 2005

Stimulated currents are detected with increasing temperature in polyethylene films following the irradiation with high-energy electron beams at 77°K. A peak current occurs at about 200°K in low-density specimens and 250°K in high-density ones.

Induced currents I under gamma-ray irradiation of polyethylene at room temperature depend on dose rate R via I ∝ RΔ. In high-density polyethylene preirradiation by electron beams of about 5×107 rads at room temperature Δ increases from 0.5 to 0.84 and is accompanied by a decrease of induced current. In the low-density specimens Δ decreases from 0.8 to 0.6 and the induced current increases with the same preirradiation. After boiling the preirradiated specimen for 5 min, Δ becomes 0.5 in both cases, and in the high-density specimens the induced current I returns to that of the nonirradiated sample. This behavior suggests that the increase and decrease of carrier traps by these treatments influence the induced current characteristics. Another factor influencing the induced conductivity is the crystallinity; with decreasing crystallinity the induced conductivity of all specimens decreases, while in most cases Δ values increase. This behavior suggests the domination of electrons as charge carriers and that they are able to flow more easily in the crystalline parts than in the amorphous parts.
Optical Frequency Plasma Resonance in Gases
Authors: Minck R. W. , Rado W. G.
Published: April 2005

An intense optical beam is reflected backwards from a laser-induced spark in argon and nitrogen gas at high pressures. The reflected beam is about 10% as intense, diverges with a comparable angle, and has the same frequency (to within about 0.01 cm−1) as the incident beam. By simultaneously focusing a weak second harmonic beam onto the discharge, the reflectivity at the higher frequency was measured. One percent of the incident harmonic beam was reflected in a nearly collimated beam, and with no apparent frequency shift (less than 0.05 cm−1).

The proposed model is that stationary region having very high electron density (ne≈2×1021 electrons/cc) is created in the focal volume and exhibits plasma resonance at the laser frequency. The resonance would appear quite damped due to the high collision rate.

Experiments have been performed which support the hypothesis and discriminate against several other possible explanations such as reflection from the mismatch of index of refraction at the shock front, stimulated Brillouin scattering, and stimulated plasma-wave scattering.
Evaluation of Some Transport Integrals
Authors: Adawi I. , Glasser M. L.
Published: April 2005

The transport integrals ∫0∞x2n(x2+a2)−1ex(ex±1)−2 dx for Fermi-Dirac (+) and Bose-Einstein (−) statistics are expressed simply in terms of tabulated functions. Some examples from the theory of lattice thermal conductivity and electron-electron collisions in metals are discussed. The related integrals ∫0∞ x2n+1(x2+a2)−1(ex±1)−1 dx are also evaluated.
Theory of a Microwave Plasma Instability due to Transverse Breakdown
Authors: Toda Minoru
Published: April 2005

A theory describing a plasma instability in solids occurring in the microwave frequency region is presented. Oscillations of the uniform-mode magnetoplasma resonance type are excited because of the dependence of the electron-hole generation rate on the strong Hall electric field. The generation rate necessary for the instability to grow in InSb at 77°K is larger than 9×109 sec−1, in a transverse magnetic field of 8400 G. The existence of the magnetoplasma resonance in a bar-shaped crystal of n-InSb has been confirmed experimentally. The theory explains in qualitative fashion many features of the microwave radiation from InSb observed by Suzuki.
Light Modulation and Beam Deflection with Potassium Tantalate-Niobate Crystals
Authors: Chen F. S. , Geusic J. E. , Kurtz S. K. , Skinner J. G. , Wemple S. H.
Published: April 2005

The dielectric and electro-optic properties of KTaxNb1−xO3(KTN) are discussed from the point of view of the material's usefulness in light modulators and beam deflectors. It is shown that baseband light modulators with 200- to 300-Mc/sec bandwidths and analog deflectors with 200 to 300 resolvable spots are within the practical capabilities of this material.
Thermal Conductivities of MgO, Al2O3, and ZrO2 Powders to 850°C. I. Experimental
Authors: Godbee Herschel W. , Ziegler Waldemar T.
Published: April 2005

Thermal conductivities were measured for extensively characterized magnesia, alumina, and zirconia powders. Thermal conductivities of the powders in dry air at atmospheric pressure were determined at volume fractions solid varying from 0.49 to 0.70 as a function of temperature from about 100° to about 850°C. Particle-size distribution, chemical composition, x-ray diffraction pattern, weight loss on heating, pore-free density, and surface area of each powder were measured. Thermal conductivities were determined by a steady-state method employing radial heat flow in a hollow cylinder and by an unsteady-state method based on the model of heating a cylinder of a perfect conductor surrounded by an infinite amount of the material whose thermal conductivity is being measured.

The thermal conductivities of the powders increased with increasing volume fraction solid. The influence of gas conductivity was greater than that of the solid on the thermal conductivity of the powers. The thermal conductivity for each powder measured increased at a decreasing rate with increasing temperature, following an approximately quadratic temperature dependence. Thermal conductivity was increased by the presence of a sorbed water film as well as by mechanical pressure on the particles.
Anomalous Diffusion and Instabilities of an Argon Plasma in a Strong Magnetic Field
Authors: Chen Che Jen
Published: April 2005

The electron density decay with time in an argon discharge tube energized with a capacitor bank of energy up to 3000 J in a magnetic field up to 30 kG parallel to the axis of the tube is measured by using electron continuum intensity, ion current probe, and microwave techniques. The electron temperature decay is obtained by the spectral line intensity ratio method. The oscillation or instability in the plasma is monitored with electrostatic and magnetic probes. The coefficient of ambipolar diffusion is evaluated from the decay data obtained in the diffusion dominated region. The data thus obtained indicate that the coefficient of ambipolar diffusion agrees with the prediction of the collision theory up to a critical magnetic field of about 1000 G. Beyond 1000 G, the onset of oscillations is detected and the coefficient of diffusion is much higher than the collision theory prediction. For B>1000 G, the coefficient of diffusion varies as B−1 and the absolute values are quite close to Bohm's. It is thought that the mechanism responsible for the anomalous diffusion is the onset of instabilities in the plasma, ion oscillations dominating at low magnetic fields, and the universal drift instability at high magnetic fields.
Grüneisen Parameter of Magnesium Oxide
Authors: White G. K. , Anderson O. L.
Published: April 2005

Experimental data for the thermal expansion of magnesium oxide extending down to 20°K indicate that the Grüneisen parameter γ is about 1.60 at low temperatures and at room temperature. Near to the Debye temperature θ(800° to 1000°K), γ≃1.5. These values agree well with those calculated from the pressure dependences of the elastic moduli.
Hot-Electron Transfer through Thin-Film Al–Al2O3 Triodes
Authors: Nelson O. L. , Anderson D. E.
Published: April 2005

Triode devices, consisting of Al–Al2O3–Al–Al2O3–Al films, were used to inject hot electrons into an oxide film. Transmission ratios were measured as a function of collection-oxide thickness, collection bias, and injection at 77° and 300°K. These data were compared with a model for hot-electron penetration in which electron-electron interactions in the metal were invoked, with a mean free path le∝ (ε−εf)−2; once-scattered electrons were included in the collected fraction. Assuming an energy loss of 0.1 eV per interaction in the oxide (from optical absorption data), the comparison of the model and the experimental data yielded a mean free path between these interactions of approximately 12 Å. The predicted transmission ratios agreed quite well with the experimental data.
Linear Response Functions and the Phenomenological Equations of Internal Friction
Authors: Garcia-Moliner F. , Thomson R.
Published: April 2005

Linear response function analysis has been applied to the internal friction problem. With the use of the Kramers-Kronig relations, the analysis takes on a very convenient form which is of particular usefulness for experimental analysis. The Fourier transform of the response function is related very simply to the phase lag and the modulus defect. The general formulation is applied to simple cases of relaxation and resonance. It is also applied to the space-dependent vibrating dislocation model of Granato and Lücke, and the effects of higher modes are treated. It is shown that on the high-frequency side of the damping peak, for low damping, the higher modes contribute an increase in the damping which has the same frequency dependence as the fundamental. For high damping, the situation is indeterminate on the far high-frequency side, but for frequencies near the peak, the fundamental mode analysis of Granato and Lücke is unchanged.
Surface and Grain-Boundary Diffusion of Gold-Copper
Authors: Austin A. E. , Richard N. A. , Wood Van E.
Published: April 2005

The diffusion of gold into copper grain boundaries from thin sources has been studied from 760° to 625°C. The activation energy for the grain-boundary diffusion of gold into copper is 25 kcal/mole. At the lower temperature, there was observed surface depletion of gold at the grain boundary in accordance with theoretical solutions. The surface diffusion of gold on copper (100) surface was studied from 705° to 580°C under 10−9 Torr. The activation energy for surface diffusion was about 25 kcal/mole. The rates of surface diffusion were found to be less than those for grain-boundary diffusion at the same temperature. Gold-copper whiskers were generated adjacent to the grain boundaries for diffusion at or below 660°C. The growth of such whiskers is diffusion-controlled and is attributed to the stress resulting from volume increase due to gold diffusion into the grain boundary.
Local Mode Absorption in Compensated Silicon-Doped Gallium Arsenide
Authors: Lorimor O. G. , Spitzer W. G.
Published: April 2005

Infrared-active localized vibrational modes in lithium- and copper-compensated silicon-doped GaAs are reported. A number of absorption peaks due to both Si and Li are seen at liquid-nitrogen temperature. The local mode of the Si donor, SiGa, occurs at ν=384 cm−1; the Si acceptor, SiAs, at 399 cm−1. Two bands at 374 and 393 cm−1, along with a component of the 384-cm−1 band, are tentatively identified as the SiGa bands split by a Li (or Cu) acceptor. The three corresponding Li bands are seen near 450 cm−1 with 7Li and near 480 cm−1 with 6Li. For Li(Cu)-Si-doped GaAs a weak coupling model between Si-Li or Si-Cu ion pairs is proposed. This model has been previously proposed for Li-B-doped Si. Si concentration studies indicate that the strengths of the SiGa 384-cm−1 and SiAs 399-cm−1 bands are related more closely to the total Si concentration than to the carrier concentration. A number of additional and, at present, unexplained peaks are also observed.
Temperature and Strain-Rate Dependence of the Flow Stress of AgMg Single Crystals
Authors: Mukherjee A. K. , Ferguson W. G. , Barmore W. L. , Dorn J. E.
Published: April 2005

The effect of temperature and strain rate on the flow stress of β-AgMg single crystals was investigated in the temperature range of 77° to 900°K and strain-rate range of 10−4 to 104 sec−1. The low-temperature data were found to obey the predictions of the Peierls mechanism up to strain rates of 1.8×104 sec−1. Above strain rates of 1.8×104 sec−1 the shear stress becomes athermal and strain-rate-sensitive. The high-temperature data were found to be thermally activated and showed increasing strength with decreasing temperature and increasing strain rate. There is a temperature-sensitive, strain-rate-insensitive region which divides the low- and high-temperature thermally activated mechanisms and shows increasing strength with increasing temperature.
Effective Biaxial Anisotropy in Double-Layered Thin Magnetic Films
Authors: Hayashi Nobuo , Goto Eiichi
Published: April 2005

Quantitative experimental results have been obtained in support of a previously developed theory which represents the deformation of the critical curves of multilayered magnetic thin films in terms of effective multiaxial anisotropies. The effective biaxial anisotropy field has been experimentally observed to be proportional to the square of film thickness in the case of thinner films, as expected from the theory. From this dependence, the value of the exchange constant of Ni-Fe-Co (70–19–11 wt%) alloy is found to be A=1.6 ×10−6 erg/cm, which is in fair agreement with the value A=0.86×10−6 erg/cm obtained from a spin-wave resonance measurement. Deviation from the quadratic dependence in thicker films has been observed and explained.
Effects of Gases on the Properties of Vapor-Deposited Ni-Fe Films
Authors: Paul M. C. , Hanson M. M.
Published: April 2005

Effects of O2, N2, H2, and H2O on characteristics of vapor-deposited Ni-Fe films are determined with the aid of quadrupole and monopole gas analyzers. Data obtained for films deposited in getter-ion or oil-diffusion-type vacuum systems show that the presence of high oxygen partial pressures during deposition has a pronounced effect on the anisotropy field, coercive force, magnetoelastic strain coefficient, and product of easy axis dispersion and anisotropy field, while the other gases tested have little if any effect on film properties. High oxygen pressures or slow deposition rates during formation of the initial few-hundred-angstrom layer, followed by ``normal'' deposition, showed that propagation of a physical structure established in the initial layer is probably not responsible for the effects brought about by oxygen.

Post-deposition annealing in an oxygen-rich atmosphere resulted in changes of magnetoelastic strain coefficient, indicating a surface oxide effect and/or diffusion into the films. ``Soaking'' glass substrates in high oxygen partial pressures for a short time prior to deposition did not have a noticeable effect on film properties, but treatment of substrates with oxygen-bearing chemicals prior to deposition did cause significant changes in film properties.

Attempts to find oxides in the Ni-Fe films by electron-diffraction techniques were unsuccessful, but microscopy studies revealed smallest grain size in films which were deposited in the presence of highest oxygen pressures. Electron-diffraction analysis of pure nickel and pure iron films deposited in oxygen-rich atmospheres showed the presence of NiO, FeO, Fe2O3, and Fe3O4.
Low-Temperature Elastic Properties of ZrC and TiC
Authors: Chang Roger , Graham L. J.
Published: April 2005

The elastic constants of zirconium carbide and titanium carbide were determined over the temperature range of 4.2° to 298°K using a pulsed-ultrasonic phase comparison technique, and are compared to previously determined values for uranium carbide. Since these carbides are of the NaCl structure, only three independent constants are required to describe their elastic behavior. Their values at 298°K are ZrC0.94TiC0.91C114.720±0.0055.145±0.005C120.987±0.0051.060±0.002C441.593±0.0021.788±0.002all in units of 1012 dyn/cm2. The differences in the elastic behavior of these group IV, transition metal carbides and the monocarbide of uranium are discussed in reference to their different electronic structure.
The Metastable Solid—Liquid Phase Boundary
Authors: O'Hara Sydney
Published: April 2005

The solid—liquid interface of a material which is transforming under transport-controlled conditions is examined from the point of view of stability. Three forms of interfaces, namely the spontaneously unstable, the metastable, and the stable, appear to be possible. The metastable form of solid—liquid interface has not, as yet, been considered, apparently because its presence has not been recognized. As is shown, however, it can be predicted by the perturbation analysis of interface stability and examples of its occurrence in crystal growth are examined.
Elastic Constants of Cadmium from 300° to 575°K
Authors: Chang Y. A. , Himmel L.
Published: April 2005

The adiabatic elastic constants of single-crystal cadmium have been determined by means of the ultrasonic pulse-echo technique over the temperature interval from 300° to 575°K. The values obtained at 300°K are C11 = 11.45, C33 = 5.085, C66 = 3.750, C44 = 1.985, and C13 = 3.99 in units of 1011 dyn/cm2. The temperature dependences of the linear compressibilities, the Grüneisen parameter, and the lattice contribution to the specific heat have been calculated using the elastic constants obtained in the present study and other necessary thermal data available in the literature.