bluuebunny/crossref_metadata_2025 huggingface dataset:
Phototunnel conductance effect in GaAs p-n and MIS junctions
Authors: Nishizawa Jun-ichi , Kimura Mitsuteru
Published: February 2004

p-n tunnel junctions made by alloying and MIS tunnel junctions made by contacting the metal were fabricated using degenerate n-type GaAs substrates. The conductance G and capacitance C of these diodes have large sensitivity to light irradiation and show similar spectra with respect to photon energy. The relative variation of photoconductance with initial dark conductance, ΔG/Gd, is more than ten times that of the photocapacitance, ΔC/Cd. It was found that the quenching light effect is observed in p-n tunnel junctions but not in MIS tunnel junctions. These phenomena are explained by considering the change of trapped charge in the deep level due to illumination which induces a change of the depletion layer structure and the tunneling probability, resulting in the changes of C and G (phototunnel conductance). The experimental results have been shown to agree well with theoretical calculations.
MIS electroluminescent diodes in ZnTe prepared by Al vapor diffusion
Authors: Gu Jyongsil , Tonomura Kenichi , Yoshikawa Nobuhisa , Sakaguchi Tadao
Published: February 2004

Very high-resistivity (1011–1012 Ω cm at 300°K) layers have been obtained by Al vapor diffusion into ZnTe using iodine as a carrier gas under a Zn atmosphere without surface erosion. Avalanching MIS electroluminescent diodes were fabricated using this technique. Spectral outputs of the diodes are yellow at 300°K and green or yellow-green at 77°K. The external quantum efficiencies are 0.1 [inverted lazy s] 0.2% in the yellow, 10% in the green, and 20% in the yellow-green. The yellow and the green electroluminescence appear to be due to an acceptor-donor pair consisting of the doubly ionizable Zn vacancy and an unknown donor, whereas the yellow-green is characteristic of Al-doped ZnTe.
Stability criteria of an electrified liquid jet
Authors: Neukermans A.
Published: February 2004

A derivation is made of the stability criteria of an electrified liquid jet. It is shown that the expression of Schneider et al. is incorrect. The results agree with the deviation of Bassett and Melcher.
Reply to ``Comment on 'Hot carriers in Si and Ge radiation detectors'''
Authors: Drummond William , Moll John
Published: February 2004

The generality of our calculations of the characteristics of Si and Ge nuclear radiation detectors has been questioned by Antončík. This reply defends the generality of our method with a brief discussion of how each aspect of the ionization cascade was included in our calculation.
Phase-velocity relation for an acoustic wedge guide mode
Authors: Wagers Robert S.
Published: February 2004

A variational analysis is presented for the phase velocity of an acoustic wave guided by the apex of an infinitely tall wedge. The lowest-order antisymmetric flexural mode is considered. It is demonstrated that rather simple approximations to the particle displacements lead to an accurate prediction of the mode phase velocity as a function of the apex angle. An analytic expression is obtained for phase velocity in the limit of small apex angles.
Quantitative investigation of ultrasonic attenuation in copper single crystals
Authors: Winterhager Peter , Lücke Kurt
Published: February 2004

The dislocation contribution to the ultrasonic attenuation of high-purity copper single crystals has been quantitatively determined by forming the difference between the measured attenuation and the nondislocation part of attenuation as measured after heavy irradiation. In this way mainly, the influence of temperature, deformation, γ irradiation, and heat treatment on the dislocation damping has been studied. The measurements were evaluated according to the Granato-Lücke theory of dislocation resonance. One of the main objectives of the work was to test the applicability of various experimental and theoretical methods for gaining quantitative information on dislocations from ultrasonic attenuation measurements.
Wave equation and propagation parameters for sound propagation in suspensions
Authors: Ahuja Avtar S.
Published: February 2004

A wave equation has been formulated for the propagation of sound in suspensions and emulsions, taking into consideration the different viscosities and thermodynamic properties of the suspension components. The suspension has been assumed to be homogeneous in the sound field for the particle size to be much smaller than the incident wavelength and to be a continuous fluid which enters and leaves the control volume element at volume-averaged values of velocity and momentum. This equivalent continuous fluid has been assumed to possess a density equal to the volume-averaged density and a compressibility equal to the effective compressibility of the suspension or emulsion (calculated from the scattering theory). The formulated wave equation immediately yields the acoustical properties of suspensions or emulsions, such as sound velocity and viscous and thermal attenuation coefficients.
Statistics of the thermally activated glide of a dislocation through a random array of point obstacles
Authors: Morris J. W. , Klahn Dale H.
Published: February 2004

This paper treats the statistics of thermally activated glide of a dislocation, modelled as a string of constant tension, through an array of randomly distributed identical immobile point obstacles. The parameters governing thermally activated glide are defined, and equations are developed giving the expected value and variance of the time to activate through an obstacle array or sequence of arrays in terms of the properties of the obstacle configurations encountered. The proper statistical definition of the velocity of glide is dicussed. It is shown that the velocity of glide, as determined from the strain rate, is simply proportional to the inverse of the expected time to transit the array (or sequence of arrays). Simplifying approximations are identified for use at low temperature or high stress. We finally discuss how these statistical relations and approximations may best be used in numerical simulation of thermally activated glide.
Diffusion of lead and selenium in lead selenide
Authors: Guldi R. L. , Walpole J. N. , Rediker R. H.
Published: February 2004

New measurements of the radioactive tracer diffusion coefficients of selenium-75 and lead-210 in PbSe, obtained using a vapor source diffusion technique, are reported. These measurements yield significantly lower values of the diffusion coefficients for both species than those previously reported by others. For selenium-saturated PbSe, DSe*=8.13×10−4exp(−1.33 eV/k T) and DPb*=9.81×10−4exp(−1.67 eV/k T), while for lead-saturated PbSe, DSe*=0.553 exp(−2.22 eV/k T) and DPb*=3.74×10−2exp(−2.05 eV/k T). An analysis of these results indicates that selenium atoms diffuse by means of interstitial defects in selenium-rich material and most probably through selenium vacancies in lead-rich material, and that lead atoms diffuse through lead vacancies in selenium-rich material and most probably through lead interstitials in lead-rich material. The tracer data are used in conjunction with a theoretical model of interdiffusion to predict values of the p-n junction diffusion coefficients in PbSe which are in excellent agreement with published experimental results. A similar comparison of the tracer data with n-p junction diffusion data shows good qualitative agreement. Quantitative discrepancies are observed which are explained by the theoretical model.
Generation of high-energy plasmas by electromagnetic implosion
Authors: Turchi Peter J. , Baker William L.
Published: February 2004

Multimegajoule high-temperature high-Z plasmas are of interest as high-intensity radiation sources for use in a number of applications. This paper describes a possible method of generating such plasmas by means of the j × B driven implosion of thin metallic foil cylinders. Basic analytical guidelines are developed and the results of numerical computations are displayed. Experimental problems associated with the creation of high-energy plasmas by this technique are discussed with some initial experimental results presented.
Electrical properties of CuGaS2
Authors: Tell B. , Kasper H. M.
Published: February 2004

A series of CuGaS2 crystals were annealed in excess sulfur at temperatures between 250 and 850°C. This treatment varies the room-temperature hole density from 5 × 1015 cm−3 to 2 × 1018 cm−3. From the temperature dependence of the resistivity, the acceptor ionization energies of several representative samples were determined. The energy increases from 5 to 70 meV as a function of increasing resistivity.
Waveguide and luminescent properties of thin-film Pb-salt injection lasers
Authors: Weber W. H. , Yeung K. F.
Published: February 2004

We describe the waveguide properties of the asymmetric dielectric slab formed by a very-high-index film on a low-index substrate. The analysis is appropriate for Pb-salt films grown on fluorite structure substrates. The mode reflectivities, surface scattering losses, and gain enhancements for the low-order TE and TM modes are considered. The stronger confinement of the TM modes leads to larger gain enhancements than for the TE modes. For the film thicknesses of interest, 2–4 μm, the TE and TM mode reflectivities are comparable. Using the theory of Tien, the TE modes show substantially lower surface scattering losses than TM modes of the same order. The magnitude of this loss, however, depends on an unknown parameter σ, the variance of the surface height. Experimental results are presented for thin-film diode lasers made with Pb Schottky barriers on p-type PbTe (index 6.4) grown epitaxially on BaF2 substrates (index 1.42). The spontaneous emission at 77°K is shown to agree with the band-band recombination model, assuming k conservation. Laser emission at 6.5 μm, both pulsed and cw, is observed at 10–15°K. Well above threshold the spectra generally show two dominant modes spaced by ≃ 1.4 meV. This splitting is attributed to a strain-induced shift of the energy bands. Using the deformation potentials for PbTe the observed splitting leads to an estimate −2 × 10−4 of the strain component in the [111] direction normal to the film surface. All observed laser lines are TE polarized. An analysis is made of the gain and loss parameters at threshold. The optical gain is estimated from the measured current and quantum efficiency, while the free carrier and reflection losses are calculated from the device parameters. The remaining losses can then be estimated from the threshold condition. If these losses are attributed to surface scattering, the analysis can be used to give an upper limit on σ of 0.03–0.06 μm. In every case the surface scattering loss is dominant in establishing the laser threshold, which is consistent with the strong preference shown for TE modes.
X-ray measurements of stress in thin single-crystal silicon films
Authors: Kamins T. I. , Meieran E. S.
Published: February 2004

X-ray diffraction techniques have been used to measure the lattice parameters of thin, electrochemically etched, single-crystal silicon films supported by polycrystalline-silicon substrates. The lattice parameters of silicon-on-sapphire films were also measured for comparison. From these measurements, the stresses and strains in the films were determined. The strains in the electrochemically etched films were very small (≲0.01%), while those in the silicon films deposited on sapphire were substantially higher ([inverted lazy s]0.3%). The corresponding high stresses may significantly affect the electrical properties of devices fabricated in silicon-on-sapphire films, while the much lower stresses in devices fabricated in the electrochemically etched films should be of little importance.
Electromagnetic generation of ultrasonic waves in 3-d transition metals
Authors: Hanabusa M. , Kushida T. , Murphy J. C.
Published: February 2004

We investigated experimentally acoustic waves generated by electromagnetic means in the surface of 3-d transition metals. The signal amplitude was greatest when the static magnetic field was normal to the generating surface. The amplitude increased in proportion to the external field only up to 3 kOe in both polycrystalline and single crystals of Ni, while there was a tendency for the signal to decrease at high fields. Generation efficiency in Ni improved with increasing temperature at low fields, but the amplitude observed at high fields decreased at high temperatures. The experimental results in ferromagnetic nickel are explained in terms of dynamic magnetostriction. Above the Curie temperature, the magnitude of the amplitude was accounted for by the Lorentz force mechanism applicable to nonmagnetic metals. The same mechanism also accounted for the amplitude observed in Fe and Co at room temperature. The results in ferromagnetic nickel are unique because of the large magnetostriction and small crystal anisotropy.
Field ion microscope images of DNA and other organic molecules
Authors: Graham W. R. , Hutchinson Franklin , Reed D. A.
Published: February 2004

Molecules of DNA, transfer RNA, and copper phthalocyanine on a sharp iridium tip were surrounded with ordered layers of platinum by vacuum deposition. The field ion microscope was used to show cavities in the platinum layers with dimensions of the same order as the molecules being visualized.
Evidence for dislocation-controlled crater wear of polycrystalline aluminum oxide cutting tools
Authors: Kim C. H. , Smith W. C. , Hasselman D. P. H. , Kane G. E.
Published: February 2004

Transmission electron micrographs are presented which show evidence of plastic deformation in the form of high densities of dislocations and twins in the subsurface of the crater area of polycrystalline alumina cutting tools. The inverse dependence of crater area on hardness for four different tool materials suggests that plastic flow controls the rate of crater wear.
Convolution and parametric interaction with semiconductors
Authors: Kino G. S. , Gautier H.
Published: February 2004

A simple theory of the coupled semiconductor-piezoelectric convolver is given and compared to a full theory by Otto. The approximations used are valid over the interesting experimental range. For YZ–LiNbO3 and silicon, the range of validity of our theory corresponds to σ > 0.5 mho/m and f < 500 MHz.
Dielectric constants of quartz. II. Experiment
Authors: Pradoux Denise , Blanc Franc̊ois , Fanguin René , Raoult Gaston
Published: February 2004

We have given formulas for the determination of the rotation and the ellipticity of a wave that has propagated through a quartz sample in a waveguide. Taking into account the multiple reflections, calculations made with the help of a computer were compared with the experimental results. Dielectric constants of quartz are found to be 4.63 parallel and 4.51 perpendicular. Both results are believed to be correct to ± 0.7%.
Intrinsic nonstoichiometry in the lead zirconate-lead titanate system determined by Knudsen effusion
Authors: Holman Robert L. , Fulrath Richard M.
Published: February 2004

The range of the intrinsic nonstoichiometry in lead zirconate-titanate at 1100 °C has been established independently by two gravimetric techniques. A modified Knudsen effusion experiment allowed for an extended interpretation of the vapor pressure data. A single experiment was used to determine the width of any Pb1−x □x (TiyZr1−y)O3−xφx single-phase region, the equilibrium PbO vapor pressure, activity data as a function of both temperature and composition, and the exact location of the stoichiometric composition within the single-phase region. The ``vapor phase equilibration'' (VPE) method was used as a supplemental measurement of the width of most PZT single-phase regions. Results obtained by the two methods for the extent of nonstoichiometry were in close agreement (xmax = 0.10 at y = 1.0; xmin = 0.016 at y = 0.40; T = 1100°C). The Knudsen effusion experiment established that for all the compositions studied, the stoichiometric composition, Pb(TiyZr1−y)O3, was coincident with the (liquid + PZT) phase boundary.
Secondary electron emission from Au, Mo, and CuBe by high-charge-number laser-produced metal ions
Authors: Cano Gilbert L.
Published: February 2004

The secondary electron emission coefficient γ for gas-covered Au, Mo, and CuBe surfaces was determined in the energy range 0.3–22.4 keV for incident ions as follows: H+, C+ 1 → 6, Al+ 1 → 10, Cu+ 1 → 9, Ta+ 1 → 3. Energetic highly charged ions produced by a Nd laser beam focused on solid targets in vacuum were allowed to impinge on a metal target. The electrons ejected were collected and the current measured. Potential ejection is dominant over kinetic ejection in this energy range. The Parilis-Kishinevskii theory of secondary electron emission, based primarily on ionization of metal target atoms with subsequent recombination through an internal Auger process, and the present experimental results for low charge numbers (n ≤ 3e) and high mass (A ≥ 27) are only in qualitative agreement. For high charge numbers (n ≥ 4e) or low mass (A ≤ 12), there is no agreement.
Free-volume model for ionic conductivity in polymers
Authors: Miyamoto Teruo , Shibayama Kyoichi
Published: February 2004

Electrical conduction in polymers under a relatively low applied electric field is considered to be ionic and is affected strongly by the structural factors of the polymers. The following equation for the electrical conductivity σ was derived in which free volume Vf, jump energy Ej, and ionic dissociation energy W were taken into consideration: σ=σ0exp{− [γ Vi*/Vf+(Ej+W/2ε)(kT)−1]}, where σo is a constant, γ the numerical factor to correct the overlap of free volume, Vi* the critical volume required for transport of an ion, ε the dielectric constant, k Boltzmann's constant, and T the absolute temperature. This equation describes well the conduction phenomena in polymethylmethacrylate, polystyrene, and an unsaturated polyester. Relationships between electrical conduction and free volume are discussed.
Infrared absorption spectra of lithium and potassium silicate glasses at high pressure
Authors: Ferraro John R. , Manghnani Murli H. , Basile Louis J.
Published: February 2004

Infrared absorption spectra of five lithium silicate and six potassium silicate glasses of varying composition (20–35 mole% Li2O and 15–40 mole% K2O, respectively) are examined in the range 1500–100 cm−1. The frequencies of the main absorption bands decrease with an increase of alkali-metal oxide (M2O) content, with the exception of the −960 cm−1 shoulder for the lithium silicate glasses. The pressure dependences to [inverted lazy s]40 kbar, of all the main infrared absorption frequencies, which are pressure sensitive, are found to be positive. The values of d νi/d P are higher for potassium silicate glasses than for sodium and lithium silicate glasses. The effects of pressure are found to be opposite to the compositional effects. The Grüneisen mode γ's, γi, evaluated from the pressure dependence of the infrared absorption frequencies, are apparently related to the polarizing power of the alkali-metal ion. The results discussed in light of previous high-pressure infrared absorption studies of fused silica and sodium silicate glasses clearly indicate that γi, γth, and γHT generally increase with M2O content in alkali silicate glasses.
Elimination of degradation in the laser output from Ho3+ in sensitized YAG
Authors: Johnson L. F. , Ingersoll K. A.
Published: February 2004

At the present time the most efficient insulating crystal laser is α-YAG (Ho3+ in sensitized YAG), but the 2.1-μ cw output from many α-YAG crystals undergoes a degradation under continuous tungsten lamp illumination. With the aid of a series of liquid optical filters, it is shown that degradation is caused by high-energy pump photons. At least three different types of degradation are produced depending on the wavelength of pump radiation, but all may be eliminated with a liquid filter that absorbs radiation below 5000 Å.
Electron beam dissociation of fluorine
Authors: Wilson Jack , Chen Hao-Lin , Fyfe Walter , Taylor Raymond L. , Little Roger , Lowell Robert
Published: February 2004

A high-energy pulsed electron beam has been used to dissociate fluorine molecules in fluorine, helium, CO2, and hydrogen chloride gaseous mixtures. By using a probe HF laser and monitoring the amount of ir absorption by hydrogen fluoride resulting from the rapid F + HCl → HF + Cl reaction in these mixtures, the fluorine atom concentration was determined. It was found that an upper limit of approximately three fluorine atoms is produced from each electron-molecule ionizing collision.
Instability of screw dislocation pile-ups
Authors: Adelman N. T. , Dundurs J.
Published: February 2004

An instability mechanism for a pile-up of perfect screw dislocations is investigated where the cross-slip barrier is that of the Peierls-Nabarro force. The pile-up is found to reach a state of unstable equilibrium under the condition τ* = 0.66(μs)1/2, where τ* is the tip stress of the pile-up, μ the shear modulus, and s the initial slope of the Peierls force. Satisfaction of this relation will lead to cross slip of the second dislocation resulting in a blunting of the pile-up tip.
Variational bounds of unidirectional fiber-reinforced composites
Authors: Yeh Hsiang-Tao
Published: February 2004

Variational bounds for plane strain bulk modulus k, transverse shear modulus m, longitudinal Young's modulus E1, and transverse Young's modulus E2 are derived for transversely isotropic fiber-reinforced composites with periodic structure. Our results are in satisfactory agreement with experimental data. We have also derived variational bounds for the shear modulus g of an orthotropic composite lamina. Our results are again in good agreement with experimental data.
Large-area metal-oxide-semiconductor avalanche photodiodes
Authors: Foss Norman A. , Ward Samuel A.
Published: February 2004

A large active-area avalanche photodiode is described. The use of the ``reach through shortly before breakdown'' concept for achieving high stable electric fields in conjunction with a metal-oxide-semiconductor structure allows stable device operation for active areas up to 5 cm2.
The dielectric relaxation of insulating oils at low temperatures
Authors: Hakim Raymond M.
Published: February 2004

It is shown that insulating oils can be supercooled and that they exhibit a glass transition temperature and a secondary dielectric relaxation peak. The similarity in these properties between oils and polymers is discussed.
Self-enhancement of LiNbO3 holograms
Authors: Gaylord T. K. , Rabson T. A. , Tittel F. K. , Quick C. R.
Published: February 2004

Self-enhancement (an increase in diffraction efficiency upon readout with a single laser beam) is reported for iron-doped LiNbO3 holograms which have not been ``fixed'' (crystal heated to 100°C during or after recording). The rate of change for self-enhancement was observed to be equal to and opposite in sign with the rate of erasure observed in the same crystal at the symmetrical Bragg angle.
Determination of relative signs of nonlinear optical coefficients
Authors: Crane G. R.
Published: February 2004

A simple extension of Miller and Nordland's interference method for determining relative signs of nonlinear optical coefficients is given. The extended method uses a (1/4)λ retardation plate to interchange ``simple'' and ``complex'' interference signals. This makes it possible to determine relative signs of coherence lengths as well as nonlinear coefficients without independent measurements of indices of refraction.
Pressure-induced elasticity changes in V3Si
Authors: Larsen R. E. , Ruoff Arthur L.
Published: February 2004

The single-crystal elastic moduli of V3Si have been measured for hydrostatic pressures to 2.5 Kbar and temperatures from 13.5 to 296°K to determine the influence of volume decreases on the anomalous C′ = (C11 − C12)/2 shear mode softening in this A-15 material. Moduli values were obtained by measuring the cw resonance frequencies of three thin specimens that did not undergo at room pressure the well-known structural transformation exhibited by some V3Si crystals near 20°K. The measurements show all moduli to be linear in pressure. dBs/dP, which is nearly constant at 4 for temperatures down to 40°K, is near 7 at 13.5°K. dC′/dP varies from unity at 296°K to −5 at 13.5°K, vanishing at near 90°K. These results are compared with those obtained earlier for large C′-type shear loads. The possibility of inducing a structural transformation with hydrostatic pressure is discussed.
Secondary electron emission from Cs3Sb
Authors: Wooten Frederick
Published: February 2004

Monte Carlo calculations of secondary electron emission from Cs3Sb have been made for primary electron energies in the range 0.6–10 eV. All parameters in the model were determined by analysis of independent photoelectric emission experiments. Good agreement is obtained between calculated and measured secondary emission yields. Structure in the measured yield related to the threshold for electron pair production also shows up in the calculations. The results indicate that the semiclassical three-step model for photoelectric emission (excitation, scattering, and escape) also provides an accurate description of secondary electron emission.
Formation of ionization channel in high-pressure gas using pulsed relativistic electron beam
Authors: Hammer D. A. , Kapetanakos C. A. , Ury M.
Published: February 2004

The formation of an ionization channel in a high-pressure gas using a 109-W 50-nsec pulse of 500-keV electrons has been investigated. A 3-kA electron beam was injected into air, hydrogen, and helium at pressures ranging from 0.2 to 600 Torr in the presence of applied magnetic guide fields ranging up to 6 kG. It was found that the resultant beam-spreading data can be explained on the basis of elastic scattering, and that magnetic fields of a few kG can be expected to effectively control beam spread in hydrogen (and helium) up to 2 atm. Rapid loss of the plasma after the passage of the beam was observed and has been interpreted to be the rapid recombination of a very cold plasma left behind by the beam. This mechanism appears to be an attractive alternative to laser preionization of a long high-pressure Z pinch experiment.
Theoretical estimates of the temperature dependence of shear moduli in crystalline polymers
Authors: McCullough R. L. , Peterson J. M.
Published: February 2004

The shear moduli, C44 and C55, and the temperature dependence have been computed for the orthorhombic unit cell of paraffinic hydrocarbons. The computations were conducted by expressing the shear moduli in terms of intermolecular interactions formulated for infinitely long rows of H…H force centers. The interaction parameters used for the row formulation were shown to predict the correct equilibrium unit-cell dimensions. Temperature dependence was introduced by varying unit-cell dimensions according to reported thermal expansion data. These computations show that C44 decreases nearly linearly from 5×1010 dyn/cm2 at −263 °C to 3×1010 dyn/cm2 at 138 °C; C55 decreases nearly linearly from 2.4×1010 dyn/cm2 at 263 °C to 1×1010 dyn/cm2 at 138 °C. These results show that the decrease in the shear moduli resulting from changes in the intermolecular interaction field facilitates deformation at elevated temperatures. The decrease of the elastic constants with temperature further suggests that the equilibrium population of crystal defects increases more rapidly with temperature than a Boltzmann factor alone would predict.
Variation of minority-carrier diffusion length with carrier concentration in GaAs liquid-phase epitaxial layers
Authors: Casey H. C. , Miller B. I. , Pinkas E.
Published: February 2004

Minority-carrier diffusion lengths in GaAs at 298 K were determined in Ge-doped p-type layers and Sn-doped n-type layers by short-circuit photocurrent measurements. The layers were grown by liquid-phase epitaxy and utilized a 1- to 2-μ top layer of Al0.5Ga0.5As to eliminate surface recombination. Electron diffusion lengths Ln of 7–8 μ were obtained at concentrations less than 1×1018 holes/cm3 with a decrease to 0.8 μ at 1×1019 holes/cm3. Hole diffusion lengths Lp of 2–4μ were obtained at concentrations less than 1×1018 electrons/cm3 with a decrease to 0.3 μ at 6×1018 electrons/cm3. The relatively constant diffusion length in p- and n-type layers below concentrations of 1×1018 cm−3 is determined by nonradiative recombination. At hole concentrations above 1×1018 cm−3, the radiative recombination contributes to the decrease in Ln. For the n-type layers, the rapid decrease in Lp above concentrations of 1×1018 cm−3 results from an increase of nonradiative recombination at high donor concentrations.
Thermal conductivity of Ga1−xAlxAs alloys
Authors: Afromowitz Martin A.
Published: February 2004

This paper presents the results of our measurement of the room-temperature thermal conductivity of the Ga1−xAlxAs alloy system. The study was motivated by our need to characterize the thermal properties of cw heterostructure lasers, in which the heat generated in the optically active layer must flow through a substantial thickness of Ga1−xAlxAs to reach the heat sink. The measurement was made on LPE layers which were separated from their substrates and fashioned into rectangular bars. A steady-state heat flow was established in the bars utilizing an argon laser as the heat source, and the conductivity was obtained by measuring the temperature gradient in the bars with thin films of cholesteric liquid crystals. The results indicate that the thermal conductivity of the alloy is well described by an existing theoretical treatment of high-temperature lattice thermal conductivity of disordered semiconductor alloys. In the Ga1−xAlxAs system, the increased thermal resistivity of the alloy is shown to be a result of phonon scattering from mass defects and not lattice strain, which is negligible due to the excellent lattice parameter match of GaAs and AlAs.
Parametric excitation of spin waves by phonon pumping
Authors: Lyons Donald H. , Matthews H.
Published: February 2004

Parametric excitation of spin waves by a traveling phonon pump is possible because of the magnetoelastic interaction. Expressions for the threshold phonon intensity required for spin-wave pair excitation are presented. The functional dependence of the threshold intensity on pump frequency, internal field, and other pertinent parameters has been obtained numerically for several cases and the results are given here in graphical form. Experiments demonstrating spin-wave excitation by transversely polarized phonons are reported.
Scaling laws for flux pinning in hard superconductors
Authors: Kramer Edward J.
Published: February 2004

For all hard high-field superconductors examined to date, there is a maximum in the pinning force density Fp as a function of the reduced magnetic field h. Fietz and Webb first demonstrated in dilute Nb alloys that the peak in Fp scales as [Hc2(T)]2.5 if the temperature is changed; the maximum value of Fp occurred at the same value of reduced field regardless of temperature. Recent data on the temperature dependence of pinning in Nb3Sn, Nb–25% Zr and a Nb–Ti alloy, which exhibits the ``peak effect'', are analyzed to show that similar scaling laws are obeyed by these materials. All presently available evidence indicates however that the reduced field hp at which the maximum Fp occurs, as well as the height and shape of this maximum, can be altered by metallurgical treatment. Apparently weak pinning defects, or widely spaced ones, produce a small peak in Fp(h) at high h whereas strong closely spaced pins produce a large peak in Fp(h) at low h without producing much change in Fp(h) at high h. A model which predicts these metallurgical effects, as well as the scaling laws, is proposed. According to the model at h≪hp, flux motion occurs primarily by unpinning of line pins, whereas at h≫hp it occurs by synchronous shear of the flux line lattice around line pins too strong to be broken. In the high-field regime, where quantitative predictions are possible, the magnitude and field dependence of Fp are in good agreement with experiment. In this model the anomalous ``peak effect'' occurs whenever line pins are relatively weak, producing a narrow peak in Fp(h) at high h.
Optical damage and internal fields in pyroelectrics
Authors: Wood Van E.
Published: February 2004

The physical conditions under which the models of optical damage in pyroelectrics suggested by Johnston and by Amodei might be valid are described. Whether the zero-internal-field final state described by Johnston or the no-current-flow steady state of Amodei can be reached depends on the pattern of excitation and the dynamics of the damage process. In view of the small carrier diffusion lengths, the one-dimensional models generally used may not be entirely satisfactory for investigation of dynamics.
Elastic constants of Ti–40 at.% Nb at 298 °K
Authors: Reid C. N. , Routbort J. L. , Maynard R. A.
Published: February 2004

The single-crystal elastic constants of a commercial superconducting alloy Ti–40 at.% Nb have been measured at 298 °K. The results are C11=156.5±0.4 GPa, C12=111.6±0.4 GPa, C44=39.63±0.08 GPa, and C′=22.47±0.04 GPa. The value of C′ predicted by an empirical expression involving the effective electron-to-atom ratio, e*/a is 16% smaller than the measured value. The β-alloy was found to be stable to 78 °K.
Photovoltaic effects in the ionization response of tantalum capacitors
Authors: Baker R. T. , Flanagan T.M. , Leadon R.E.
Published: February 2004

The response of unbiased tantalum capacitors to ionizing radiation has been measured for both small and large dose rates. The results have been analyzed using a two-trap model for the Ta2O5 dielectric and an equivalent circuit model is presented. A significant reduction in the response of slug capacitors can be achieved by connecting two capacitors in the back-to-back or inverted-parallel configuration.
Analysis of pore shrinkage by volume diffusion during final stage sintering
Authors: Rosolowski J. H. , Greskovich C.
Published: February 2004

The steady-state flows of gas atoms and vacancies leaving a pore that is either on the surface, or at various positions inside of a spherical grain have been calculated by approximation methods for the conditions that exist during the final stage of sintering. Gas and vacancies were assumed to leave pores by volume diffusion only. It was found that the position of a pore in a grain should have little effect on its shrinkage rate—a result that appears to be in general accord with previous experimental observations on various materials. The rate of shrinkage of pores on grain boundaries in the one material investigated appears to be many times greater than that predicted by the calculations, implying that shrinkage of such pores was not controlled by volume diffusion. Pore-to-pore diffusion and removal of porosity by grain-boundary migration are also discussed.
A lattice-dynamics approach to the acoustic signal by a uniformly moving dislocation
Authors: Cortellazzi G. , Boffi S. , Caglioti G. , Rossitto F.
Published: February 2004

The acoustic signal generated by a uniformly moving edge dislocation is interpreted as the linear response of the crystal to the excitation produced by this motion. The proposed approach is based on the atomistic model of Frenkel and Kontorova, but the rigidity of the substrate is here removed. The expectation value of the atomic displacement induced in the crystal is thus directly evaluated in terms of lattice dynamics via a normal mode expansion. Numerical predictions are presented for several selected dislocation velocities in a specific case. These model calculations could help in interpreting experimental results.
Escape length of Auger electrons
Authors: Tarng M.L. , Wehner G.K.
Published: February 2004

Sputter deposition of Mo atoms on W substrates (and vice versa) was shown to form uniform overlayers. Such overlayers are ideally suited for studies of the escape length of Auger electrons. The results show that the escape length increases with Auger electron energy as expected. In both Mo and W the escape length of 48-eV Auger electrons is about 5 Å. For 1736-eV Auger electrons it increases to 24 Å in Mo and 17 Å in W. For a Mo overlayer on W, the Mo signal can reach an intensity 1.2 times that of the bulk Mo signal due to the higher backscattering coefficient of W. For a W overlayer on Mo, a corresponding reduction in the W signal compared to bulk W, i.e., an increase in the apparent escape depth was observed. With a model in which the backscattering effect is incorporated, one obtains satisfactory agreement with the experimental results. In addition the result indicates that while high-energy Auger peaks are generated by the primary beam alone, a substantial fraction of observed low-energy Auger electrons are generated by backscattered electrons. For the case of the Mo (120-eV) Auger signal with 3-keV primary beam energy, this fraction amounts to approximately 40%.
Shear strength and friction measurements on polyethylene under high pressure
Authors: Towle Laird C.
Published: February 2004

A rotating-anvil shear press was used to measure the friction coefficient and shear strength of thin layers of polyethylene at room temperature in the pressure range up to 4 kbar. A significant linear increase in shear strength with pressure was observed. The friction coefficient was observed to drop rapidly, approaching a small asymptotic value at high loads. Deformation of polyethylene under pressure was found to produce a permanent densification.
Metal-to-semimetal transition in NiS
Authors: Koehler Richard F. , White Robert L.
Published: February 2004

Measurements of the conductivity, magnetic susceptibility, and specific heat have been made on single crystals of hexagonal NiS (NiAs structure) of controlled purity and stoichiometry. Above the transition temperature NiS is found to be a metal having a density of states at the Fermi surface of approximately 26.5×1022 states/cm3 eV and displaying only Pauli paramagnetism. Below the transition temperature NiS is found to be a semimetal with a density of carrier states at the Fermi surface roughly half that of the metallic state. Below the transition temperature NiS is an antiferromagnet with a Néel temperature of approximately 1600°K. The data are interpreted and a density of states for hexagonal NiS is presented which is, we believe, in accord with all presently known data. This model resembles in many ways that of White and Mott and attributes the conductivity change to a splitting and narrowing of the Ni(eg) bands below the conductivity transition.
Memory switching phenomena in thin films of the S–Se–Te system
Authors: Hirose Yooichi , Kunioka Akio
Published: February 2004

Threshold fields have been measured with respect to switching phenomena in thin films of the S–Se–Te systems. The measured threshold field Eth was found to vary as 1/d where d is the film thickness, ranging from 0.1 to 2 μm. The relationship observed between the treshold voltage and ambient temperature indicated that the glass transition temperature played a significant role in both conduction and switching phenomena.
Continuous laser-sustained plasmas
Authors: Franzen Douglas L.
Published: February 2004

Continuous plasmas sustained by a focused high-power CO2 laser are described. The power required for maintaining a cw plasma following preionization has been determined for Xe, Kr, and Ar, and attempted for Ne and He. Measurements indicate the noble gases with the lowest ionization potentials have the lowest sustaining thresholds. Radiative properties of some of the plasmas were studied with calorimetric techniques. Under certain conditions, more than half of the incident laser radiation can either be scattered or absorbed by the plasma. A major loss mechanism for the plasma is shown to be radiation in the visible and ultraviolet. Spectra of low-pressure Xe plasmas indicate the presence of ultraviolet transitions with a high contrast over the continuum.
Properties of thick-walled cylindrical magnetic domains in uniaxial platelets
Authors: DeBonte W. J.
Published: February 2004

Additional properties are reported for the thick-walled domain model introduced in a previous paper. Substantial magnetostatic wall broadening is shown to occur when the dimensionless anisotropy q≡Ku/2π Ms2 is of the order q≲3. When q ∼ 1, the wall thickness may be as much as 75% larger than the wall thickness of the corresponding infinite planar Bloch wall, lw=π(A/Ku)1/2. The size and range of variation of the wall thickness are shown to preclude the formulation of a useful generalization of the usual bubble force equation unless q≳3. Several parameters of particular relevance to device work are presented as functions of q, and a brief treatment of the interaction of thick-walled bubbles is given.
Magnetic properties of DyCd and related CsCl-type compounds
Authors: Buschow K. H. J.
Published: February 2004

The magnetic properties of the compounds DyCd, DyZn, and some ternary compounds DyCd1−xZnx have been studied. At 4.2 K the compound DyCd shows a field dependence of the magnetization characterized by a strong increase for fields higher than 15 kOe. This increase of the magnetization is not reversible but is accompanied by a large hysteresis without involving a remanent magnetization. This behavior has been explained by a model in which DyCd is considered to be a ferromagnet in which a special type of lattice imperfection can provide sites of easy nucleation and/or strong Bloch wall pinning.
Proximity effect bridge and superconducting microcircuitry
Authors: Notarys H. A. , Mercereau J. E.
Published: February 2004

Techniques have been developed with which it is possible to fabricate superconducting thin-film structures with a wide variety of electrical and superconducting parameters which show Josephson-like phenomena. These bridges-based on the proximity effect-are made in layered thin-film ``substrates'' using a large variety of superconducting and nonsuperconducting materials. In this paper we detail the fabrication techniques and the electrical and superconducting characteristics for these proximity effect bridges including a simple low-frequency (<10 GHz) equivalent circuit based on analysis and experiment which closely describes the quantum phase coherence operation of the bridges in their voltage sustaining state. Extension of these fabrication techniques to entire thin-film electrical circuits including resistors, capacitors, and inductors with these bridges and leading to an entire superconducting microcircuit technology is discussed.
Hot-electron mobility in InSb
Authors: Nag B. R.
Published: February 2004

Values of hot-electron mobility in InSb calculated by using the Monte Carlo method are presented and compared with the experimental values and also with those calculated by using the displaced Maxwellian distribution function.
Near-infrared lasers from HCHO
Authors: Barry J. D. , Boney W. E. , Brandelik J. E.
Published: February 2004

Both CO and CO2 cw laser emissions have been produced from gaseous HCHO premixed with He and air. The CO and CO2 molecules are produced from the HCHO by oxidation reactions initiated by a glow discharge through the flowing gas mixture within the laser cavity. The CO laser action occured with liquid-nitrogen cooling; increasing the temperature to −40°C or to room temperature caused the change to CO2 laser action.
Ion wave dispersion in the presence of a finite-amplitude electron-plasma wave
Authors: Arunasalam V.
Published: February 2004

It is shown that in the presence of a large-amplitude finite-wave-number electron-plasma wave, the ion waves (of frequency ω and wave number k) do not satisfy an acoustic-type dispersion relation (i.e., ω is not proportional to k).
Readout sensitivity of an amorphous semiconductor electron beam memory
Authors: Chen A. C. M. , Dunham A. M. , Wang J. M.
Published: February 2004

The theory of readout modulation efficiency of recording by surface deformation of amorphous semiconductor targets in an electron beam memory has been derived. The theory is based on the enhancement of the secondary yield due to oblique incident electrons. This angular dependence of the yield of amorphous and crystalline forms of Ge37Te60As3 and Mo has been measured. Based on these measurements, the possible modulation efficiencies are described.
Experimental and computer-simulated studies of changing surface morphology during free evaporation
Authors: Tester J. W. , Herrick C. C. , Reid R. C.
Published: February 2004

Surface morphology of the (0001) face of arsenic was characterized by the formation and growth of equilateral triangular and truncated triangular etch pits during free evaporation. The evaporation rate was correlated with observed changes in etch pit geometry and with the variation in intensity of a reflected gas-laser beam. Experiments were supplemented by a computer simulation of free evaporation on the (0001) surface to provide a means for delineating the effect of the primary variables which control the morphology as well as the kinetic phenomena. The important controllable variables included the distribution between triangular and truncated forms, the growth rate, birth time, and the general geometric features of each pit. The birth time distribution strongly influenced the relationship between pit geometry and laser intensity. Other independent variables, such as the variation in the growth rate and degree of truncation, affected these quantities to a lesser extent.
Pyroelectricity in polyvinylidene fluoride
Authors: Pfister G. , Abkowitz M. , Crystal R. G.
Published: February 2004

The pyroelectric behavior of as-received 2-mil polyvinylidene fluoride films was studied as a function of the poling treatment. It is shown that poling induces a thermally reversible electric polarization in addition to an electric polarization which vanishes upon the first heating of the sample. Experimental evidence is given that the reversible polarization involves charge injection from the electrodes in addition to a field-induced structural change (probably the formation of oriented crystalline form I). For short poling times ([inverted lazy s] seconds) the mechanism of charge injection appears to be dominant. Initial results of the temperature and voltage dependence of the dc conductivity and of the temperature dependence of the dielectric loss at 50 and 100 Hz for unpoled and poled 2-mil polyvinylidene fluoride (PVF2) films are presented.
Effect of hydrostatic pressure on torsional stress-strain curves of single-crystal copper
Authors: Abey A. E.
Published: February 2004

The torsional stress-strain curves for single-crystal copper samples were determined at hydrostatic pressures from 1 bar to 15 kbar. The pressure derivative of the yield stress was found to be 3.8×10−3. At strains of about six, the pressure derivative of the flow stress increased to 1.78×10−2. Stress-strain curves for the various pressures are provided. A simple model of dislocation cell structure is presented in an attempt to explain the experimental results.
Intrinsic nonlinearity of secondary electron emission
Authors: Abate J. , Mandel L.
Published: February 2004

Possible nonlinearities of the secondary emission process are examined by a difference technique that compensates for other nonlinearities. At a current of 0.3 μA any intrinsic nonlinearity is found to be less than 1 part in 1000.
Surface ionization of indium and aluminum on iridium
Authors: Wilson R. G.
Published: February 2004

Atomic beams of In and A1 were ionized on a heated Ir surface in a good vacuum. Curves of ion current density versus reciprocal surface temperature are plotted with atomic reservoir temperature as parameter, yielding also desorption energies of 4 to 5 eV. Ion current densities from [inverted lazy s] 10−9 to 10−6 A/cm2 were measured in the temperature range from [inverted lazy s] 1400 to above 2000°K. The calculated ionization efficiency for the system In on Ir is about 40% taking into account excited atomic states.