bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid metal coexistence properties from corresponding states and third law
Authors: Hornung K.
Published: February 2003

An empirical procedure is introduced to describe equilibrium thermodynamic properties of metals from the experimentally covered region (0.2Tc≲T≲0.4Tc) over a very large temperature interval up to near the critical point (0.4Tc≲T≲Tc). The method uses arguments of corresponding states for the extrapolation of the interphase properties, like vapor pressure, heat of vaporization, or coexistence volumes, whereas the liquid properties, entropy, or specific heat, are determined from the gas side applying a third-law technique. Resulting high-temperature data may be used for practical description of two-phase processes as well as for estimation of basic liquid properties. two-phase processes as well as for estimation of basic liquid properties. Special application to a set of different metals (Li, Na, Sr, Ba, Pb, U, Fe, Eu), as an example, gave information about large-scale deviations of the liquid specific heat from quadratic temperature dependence (especially transition metals), and about the size of the critical compressibility Zc=pcVc/RTc, which seems to be much closer to a common value of about 0.4 than previously assumed.
Thermally stimulated ionic conductivity of sodium in thermal SiO2
Authors: Hickmott T. W.
Published: February 2003

The effect of Na+ concentration, oxide thickness, applied field, and metal electrode on thermally stimulated ionic conductivity (TSIC) measurements of positive-ion motion in SiO2 grown on single-crystal silicon has been studied. A surface trapping model, assuming blocking electrodes, has been used to analyze TSIC curves. Using a hyperbolic hearing rate (1/T ∝ time), for which analytic expressions for normalized first-order TSIC curves are obtained, both energies E and preexponential factors s appropriate to the detrapping processes are obtained. Two distinct positive-charge peaks are observed in TSIC curves. The magnitude of the low-temperature peak, the α peak, is proportional to the amount of Na+ introduced into the sample. At high fields, the magnitude of the high-temperature peak, the β peak, is independent of the evaporated Na+ concentration; its origin is uncertain but it may be due to mobile hydrogen. The temperature for the maxima in the TSIC curves, Tm, decreases with field for both the α and β peaks. At Na+ concentrations below 2×1012 Na+/cm2, the β peak is dominant in TSIC curves. Na+ motion from the Au-SiO2 interface during the first heating of Au-SiO2-Si samples follows the simple model for release of Na+ from interface traps. On the other hand, Na+ motion from the Al-SiO2 interface on the first heating of Al-SiO2-Si samples occurs at lower temperatures than for Au-SiO2-Si samples and appears to depend on reaction between Al and SiO2 rather than on a simple trap-release process. Na+ release from traps at the Si-SiO2 interface is similar with both Al and Au electrodes, and occurs at lower temperatures than for Na+ release from the metal-SiO2 interface.
Mean free path of hot electrons at the surface of boron-doped silicon
Authors: Verwey J. F. , Kramer R. P. , de Maagt B. J.
Published: February 2003

Electrons can be injected from silicon into silicon dioxide in a metal-oxide-semiconductor-transistor (MOST) structure in which electrons are accelerated in the depletion layer of the channel region in a direction perpendicular to the Si-SiO2 interface. An analysis of the resulting oxide current as a function of the reverse voltage applied to the source and drain regions is carried out using an extension of a model proposed by Shockley. This leads to an estimate of the mean free path λ of the hot electrons in the silicon. It appears that a heavily doped source and drain, formed by a phosphorus diffusion, or the dislocations generated by this diffusion, have the effect of increasing λ by, presumably, the removal of scattering centers. The largest value of λ observed, λ=135 Å, is possibly equal to the value of the mean free path for the generation of high-energy phonons.
A simple analytical calculation for x-ray photoemission
Authors: Lopez O.
Published: February 2003

A simple analytical model for x-ray photoemission is presented. The model, based on age diffusion theory, includes the effects of energy loss and multiple scattering and considers both photoelectric and Auger processes. Expressions are obtained for the photoelectric yield and differential yield. Predictions based on this model are shown to be in agreement with recent experimental data and with Monte Carlo calculations.
Surface diffusion processed multifilament Nb3Sn conductors
Authors: Deis D. W. , Shaw B. J.
Published: February 2003

Multiple coats of Sn have been applied to a Nb-Cu composite multifilament conductor and processed to form Nb3Sn layers on each filament. The critical current has been evaluated in fields up to 48 kG at 4.2 K and resistivity and critical temperatures measured. Electron microprobe and scanning electron microscope techniques have been used to investigate the Sn and Nb3Sn distributions within a reacted conductor.
Calibration of the pressure dependence of the R1 ruby fluorescence line to 195 kbar
Authors: Piermarini G. J. , Block S. , Barnett J. D. , Forman R. A.
Published: February 2003

The pressure dependence of the R1 ruby fluorescence line has been calibrated at 25 °C against the compression of NaCl. Pressures are determined using the Decker equation of state for NaCl. The dependence is linear to 195 kbar following the equation PNaCl=2.746(Δλ), where P is in kbar and Δλ in Å. The uncertainty in the value of the slope, dp/dλ, expressed in terms of a 95% confidence interval is 2.746±0.014 kbar Å−1. The coefficient of the quadratic term (Δλ)2 is not significantly different from zero; and the quadratic term makes indeed a negligible contribution to the fit. Taking into account the reported uncertainty associated with the Decker equation of state for NaCl, the value of the slope is 2.740±0.016 kbar Å−1 within a 95% confidence interval.
A new approach for treating fluctuations in noise theory
Authors: Thornber K. K.
Published: February 2003

A new method, introduced in a previous article, is shown to overcome certain physical difficulties encountered in noise problems when treated by more common approaches. In particular, an internal inconsistency in the original Langevin approach for treating Brownian motion is explicitly presented in which problems arise because the statistical treatment is carried out at a too macroscopic level. As another example, a more realistic expression for the retrogression of a fluctuation is obtained in which the cusp at t=0, characteristic of Markov approaches, is avoided. The method is extended to treating systems of subsystems, and the concept of internal noise is introduced to enable a simpler, more macroscopic noise analysis. The method is also applied to determine statistical properties of fluctuations in irreversible thermodynamcis. We hope that our discussion will further illustrate the origin, nature, and treatment of fluctuations in linear classical systems.
Optical and dielectric constants of hafnium and its anodic oxide films
Authors: Saxena A. N. , Mittal K. L.
Published: February 2003

Optical and dielectric constants of Hf films deposited by sputtering were measured at a wavelength of 546.1 nm using ellipsometry. The thicknesses of the films deposited were 300 nm. Also, ellipsometric results are reported for HfO2 films obtained by anodizing Hf films at various forming voltages. The average value of the refractive index n1 of HfO2 films was found to be 2.09 and it remains essentially constant for the range of thickness (12.5–53.7 nm) studied.
Gaussian-beam distribution of magnetostatic surface waves in inhomogeneous dc field
Authors: Bini M. , Millanta L. , Rubino N.
Published: February 2003

Experiments of magnetostatic surface-wave propagation in YIG slabs have been performed which show a transverse distribution of rf field of Gaussian shape. Previous theories are for uniform internal dc field and give uniform or cosine rf distribution. The observed Gaussian shape can be tentatively explained in terms of propagation in a nonuniform lossy medium, the nonuniformity being a consequence of the internal dc field profile.
Uniform magnetic fields in deflection coil design and the problem of the ellipsoid
Authors: Marsh G. E.
Published: February 2003

The problem of obtaining a uniform magnetic field within a nondegenerate ellipsoid by the use of an appropriate surface current distribution is investigated. The curves of constant current on the surface of the ellipsoid are determined. The relation of the present work to the design of deflection coils is discussed.
Noise characteristics of ion-implanted MOS transistors
Authors: Nakamura Kunio , Kudoh Osamu , Kamoshida Mototaka
Published: February 2003

Low-frequency excess noise characteristics of ion-implanted MOS transistors annealed above 1000 °C were investigated. Noise characteristics strongly depended on implant species, implant condition, and measurement conditions. In the case of implantation into opposite-type conductivity substrates, such as 11B+-implanted p-channel or 31P+-implanted n-channel transistors, the equivalent input noise voltages measured at lower drain currents exhibited generation-recombination (G-R) noise caused by residual damage in the substrate. This noise component increased with increasing acceleration energy or implant dose. The G-R noise decreased with increasing drain current. At higher drain currents the G-R noise disappeared and the noise voltages of the implanted samples were somewhat smaller than that of the unimplanted samples. On the contrary, in the case of implantation into the same-type conductivity substrate, such as 31P+-implanted p-channel or 11B+-implanted n-channel transistors, no G-R noise component was observed and noise voltages increased with increasing dose. The difference was also observed in the surface recombination velocity measurements. These results could be attributed to the difference in the position of the carrier path due to the change of surface band bending. The G-R noise could not be removed by heat treatment up to 1200 °C. It was confirmed that there were no dose rate dependences within the range 0.1–10 nA/cm2.
Acoustic-surface-wave measured majority-carrier surface mobilities
Authors: Pierret R. F. , Gunshor R. L.
Published: February 2003

Theoretical predictions are noted for majority-carrier surface mobilities and compared against previously published ASW measured surface mobilities in silicon.
Tunneling of photoexcited carriers in metal oxide varistors
Authors: Philipp H. R. , Levinson Lionel M.
Published: February 2003

ZnO-based ceramic varistors exhibit photocurrents which vary in a highly nonlinear manner with applied voltage. It follows that varistor behavior is controlled by electrical barriers at the ZnO-grain–intergranular-layer interface.
Electrical conduction in thin polycrystalline TiO2 films
Authors: Lalevic B. , Taylor G.
Published: February 2003

Transport properties of thin polycrystalline TiO2 (rutile) films were studied as a function of the applied field, temperature, and frequency. The I-V-T plots showed that the Poole-Frenkel emission mechanism is responsible for high-field dc conduction, while low-field ac conductivity is in agreement with the theory of hopping conduction.
Total radar cross section of thin wires at all angles of incidence
Authors: Tavis M. T.
Published: February 2003

The total radar cross section (RCS) of thin perfectly conducting wires is calculated by two methods using the general Van Vleck, Bloch, and Hamermesh theory of RCS. These methods involve calculating the work done on the wire by the incident field or calculating the total flux scattered by the wire. It is found the two methods give nearly identical results and it is suggested that the method of work be used due to its simpler formulation. Numerical examples are presented and it was observed that resonances in the broadside total RCS occur at half-integer values of βl, where β is the propagation vector and l is one-half the wire length.
Barrier height of Hf/GaAs diode
Authors: Kajiyama K. , Sakata S. , Ochi O.
Published: February 2003

Schottky barrier heights of 0.72 V for Hf/n-GaAs and 0.68 V for Hf/p-GaAs are experimentally obtained. These values agree with the empirical rule. Existence of an interfacial insulating layer is suggested.
Obliquely deposited amorphous Ge films. I. Growth and structure
Authors: Pandya D. K. , Rastogi A. C. , Chopra K. L.
Published: February 2003

The structure and growth of amorphous Ge films deposited at an angle of incidence ranging from 0° to 80° have been studied by electron microscopy and electron diffraction as a function of the film thickness, deposition temperature, deposition rate, and annealing temperature. Like crystalline films, the growth of amorphous films proceeds via random nucleation centers and is controlled by the small but finite adatom mobility. The small adatom mobility results in the formation of a large concentration of vacancies, vacancy clusters, voids, and associated dangling bonds in a-Ge films. The adatom mobility is enhanced by the elevated deposition temperatures and oblique incidence and, consequently, the concentration of vacancy clusters and voids decreases. The formation of columns and decoration of structural defects associated with the cleaved NaCl single-crystal substrates during the growth of a-Ge films are a direct consequence of the enhanced adatom mobility. The observed thickness dependence of the resistivity and the variation of density, crystallization temperature, and short-range order with the deposition parameters are in accord with the structural model as deduced from our observations of the growth behavior of a-Ge films. The marked structural changes in a-Ge films on deposition at an angle of incidence result in significant changes in their physical, electrical, and optical properties.
Properties of vacancy defects in GaAs single crystals
Authors: Chiang S. Y. , Pearson G. L.
Published: February 2003

The electrical properties of GaAs single crystals were measured after annealing at various elevated temperatures in controlled atmospheres. Two types of defects were introduced as the result of annealing: (i) donors having a high concentration near the surface and (ii) acceptors having a lower surface concentration but extending further into the crystal. The As overpressure dependencies indicate that the donors are As vacancies and the acceptors are Ga vacancies since their respective concentrations are proportional to iPAs4−1/4 and iPAs4+1/4. The entropy and enthalpy changes for the vacancy formation reactions at the surface were evaluated, based on experimental data and thermodynamic analysis. The diffusion coefficients of vacancies follow the relations D (VGa) =2.1×10−3 exp(−2.1/kT) and D (VAs) =7.9×103 exp(−4.0/kT). Both types of vacancies form nonradiative centers as determined from photoluminescence experiments.
Theoretical examination of imperfections in the imaging of the output of a solid-state heterojunction laser
Authors: Lewin L.
Published: February 2003

Radiation pattern narrowing, distance effects, and scale distortion, as well as limited lens aperture, are examined for their effects on the image of a laser mode output. For moderate apertures a broadening of the image is calculated, relative to that of an ideal transformation. For very large apertures the image would be narrowed. The finite lens aperture also has the effect of raising the expected exponential wings of the image. Both these effects have already been reported. Attention is drawn to the fact that, no matter how ’’perfect’’ the lens system may be, spectral components are inevitably lost, so perfect reproduction is in principle not possible. Numerical computation is recommended for an exact evaluation of the image distortion.
Switching effects in polycrystalline cadmium telluride films
Authors: Denton G. A. , Friedman G. M. , Schetzina J. F.
Published: February 2003

Experimental observations of switching phenomena in evaporated polycrystalline CdTe films are described. The off-state behavior of CdTe samples sandwiched between crossed metallic electrodes was investigated using standard I-V curve tracing techniques. Symmetric I-V characteristics were observed for different combinations of metallic electrodes. The CdTe samples exhibited Ohmic conduction (ρ∼108 Ω cm) for small applied voltages followed by an exponential current region of the form I=I0 exp(V/V0) which terminated with memory switching. The resistance of the memory on state was typically 100–200 Ω. A single reset voltage pulse (∼ 1 μsec duration, 50 nsec rise time) of magnitude comparable to the switching voltage and applied through a 10-K load resistor usually sufficed to return the samples to the off state. The switching voltage was found to increase with film thickness in an approximately linear fashion. A rudimentary form of threshold switching was also detected when the samples were subjected to short voltage pulses. Many of the observations can be accounted for by considering the CdTe films to be crystalline trap-dominated relaxation semiconductors.
Theory of mode locking with a fast saturable absorber
Authors: Haus Hermann A.
Published: February 2003

This paper presents a closed-form analysis of saturable absorber mode locking of a homogeneously broadened laser. A solution is obtained for the case of a short relaxation time of the saturable absorber. This pulse is a hyperbolic secant as a function of time. For each choice of parameters two pulse widths are found. A stability analysis shows that the solution of greater width is stable. The requirements for achieving mode locking with a fast saturable absorber are stated. The effect of a time-varying laser medium gain is investigated analytically.
Optical and electrical properties of Mn-doped GaAs grown by molecular-beam epitaxy
Authors: Ilegems M. , Dingle R. , Rupp Jr. L. W.
Published: February 2003

An isolated acceptor impurity is shown to be responsible for the ∼113-meV deep luminescence band which is frequently seen in GaAs layers grown by molecular-beam epitaxy. We establish that this center, which is also observed in melt-grown and solution-grown GaAs and which has often been associated with the presence of native defects, is due to Mn. The luminescence arises from donor-acceptor and conduction-band–acceptor recombination involving holes bound at the Mn acceptor. Electron paramagnetic resonance on Mn-doped layers shows that Mn is incorporated as an isolated defect with cubic symmetry. This result, coupled with the suppression of Mn-associated luminescence and electrical activation under Ga-rich growth conditions, indicates that Mn is incorporated primarily as a substitutional acceptor on Ga sites. Hole concentrations scale with Mn source temperature in a manner consistent with arrival-rate-controlled incorporation from a Knudsen effusion source. Room-temperature hole concentrations up to the 1018-cm−3 level can be achieved while maintaining excellent surface morphology. This suggests that Mn will be a useful dopant in the growth of junction structures by molecular-beam epitaxy.
Electrical properties and injection luminescence in ZnSe-ZnTe heterojunctions prepared by liquid-phase epitaxy
Authors: Fujita Shigeo , Arai Seiichi , Itoh Fumi , Sakaguchi Tadao
Published: February 2003

The electrical properties and the injection electroluminescence in the ZnSe-ZnTe n-p heterojunctions prepared by the liquid-phase epitaxial growth from Zn or Bi solution have been studied. The prepared heterojunctions consist of a p-s-n structure with distributed trap centers at the boundary region. The heterodiodes show an emission band peaking at about 1.94–2.04 eV at room temperature. At 77 K, the spectra generally have four emission bands at 1.98, 2.32, 2.70, and 2.78 eV. The dominance of any one of these emission bands over the others depends upon the preparation conditions. The photoluminescence measurements of the heterojunctions show that the light generation of the heterodiode occurs at the ZnSe branch of the junction: The emission occurs through hole injection from the p-type ZnTe into the n-type ZnSe. The best value for the external quantum efficiency of the light emission in the heterodiodes measured by an integrating sphere method is about 4×10−3 photons per electron at 77 K. The relation between the luminescence and the electrical characteristics of the prepared heterodiodes is discussed with tentative band models.
Effect of electron-hole interaction on the Auger recombination process in a semiconductor
Authors: Takeshima Masumi
Published: February 2003

The effect of the electron-hole interaction on the Auger recombination process in a semiconductor is discussed. Using a simplified treatment based on an excitonic picture, a theory for an excess carrier lifetime is developed. The calculation is done for an n-type material with direct band gap, taking account of both nondegenerate and weakly degenerate statistics. The result is compared with the experimental data on n-type InAs. It is shown that both the electron-hole interaction and the statistical degeneracy have an important effect on the temperature dependence of the Auger recombination lifetime of excess carriers.
Electron impact desorption of ions from gas-covered Si(111) surfaces
Authors: Nishijima M. , Fujiwara K. , Murotani T.
Published: February 2003

The electron impact desorption of ions was investigated using ∼100-eV electrons from Si(111) surfaces covered with O2, H2O, CO, NO, HC1, H2S, and NH3. The observed ions are O+ from Si-O2 and Si-NO; H+ and O+ from Si-H2O; and Cl+ from Si-HCl. The ion yields, energy distributions of ions, and electron energy dependence of relative ion yields are reported. It is found that O2, H2O, and NO adsorb in a single state, respectively, and HCl adsorbs in at least two states.
Evidence for interfacial space-charge regions in electron-beam-evaporated SiO
Authors: Roger Jean-Alain , Dupuy C. H. S. , Fonash Stephen J.
Published: February 2003

We report here I-V and capacitance data and SEM observations made on thin-film SiO metal-insulator-metal structures. Devices were fabricated using electron-beam-evaporated SiO and several different metals for the electrodes. I-V observations alone could be interpreted as bulk-limited conduction; however, the dispersion of the capacitance in frequency is bias dependent and suggests interfacial space-charge regions. SEM observations support this interpretation and show these regions growing and shrinking with bias, demonstrating that the interfacial regions are not of negligible resistance.
Optical emissions from e-beam-excited gas mixtures
Authors: Gutcheck R. A. , Hill R. M. , Lorents D. C. , Huestis D. L. , McCusker M. V. , Nakano H. H.
Published: February 2003

A high-energy electron beam has been used to pump mixtures of rare gases and atmospheric gases or metal vapors. Bright optical emissions have been produced, and a table is given listing both the observed transitions and their relative intensities.
Photo-Compton currents emitted from a surface
Authors: Dellin Theodore A. , MacCallum Crawford J.
Published: February 2003

Weymouth’s method for calculating electron transport in a half-space is generalized and used to obtain algebraic expressions for the magnitude and angular distribution of the photo-Compton current emitted from a surface irradiated by photons of any energy between 10 keV and 10 MeV. Algebraic expressions for the energy deposition at the surface and for the energy distribution of the emitted electrons are also obtained. Comparisons with Monte Carlo calculations and with experiment are presented.
Electron microscopy of colloidal metal particles in alkali halides
Authors: Ekmanis Yuris A. , Rosauer Elmer A.
Published: February 2003

Replicas of previously prepared alkali halides were found to be extraction replicas with metal-containing colloidal particles. These particles were examined in the scanning and the transmission electron microscopes. It is shown that qualitative and quantitative elemental analysis of such colloidal particles may be performed in both instruments. Comparisons are made and limitations are discussed.
Stress-induced anisotropy in the electrical properties of Si/Al2O3
Authors: Hughes A. J.
Published: February 2003

The effect of stress on the electrical properties for a number of orientations of Si/Al2O3 has been theoretically determined. The stress model developed and employed is based upon the differential in thermal expansion between Si film and an Al2O3 substrate. The anisotropy in substrate thermal expansion coefficients and in Si film stresses is rigorously included and treated within the framework of a thin-film thick-substrate approach. The phenomenological piezoresistance formalism is used to determine the effect of stress on resistivity which is then in turn related to the carrier mobility. Mobility calculations were performed for the common Si orientations— (001), (111), and (221) —and for a number or orientations not yet grown and investigated experimentally. For n-type Si the mobility is either reduced or enhanced depending upon mode of epitaxy and orientation. For p-type Si the mobility is always enhanced and for some orientations by a significant factor. The theoretical results obtained indicate that the thermal stress effect on mobility has a strong orientation dependence and that, compared with the commonly employed (001) Si/Al2O3 orientation, substantially larger mobilities could be obtained with other Si/Al2O3 orientations.
Analysis of eddy-current flowmeters
Authors: Feng C. C. , Deeds W. E. , Dodd C. V.
Published: February 2003

Coils can induce and detect eddy current in nearby conductors. If the conductor is moving, the eddy currents are carried along with it slightly, and properly designed coils can measure the velocity of the moving conductor with considerable accuracy. Calculations have been made for various axially symmetric arrangements of coils and conductors using a relaxation program for a computer. Experiments have also been made, using mercury as the flowing conductor, with three- and five-coil flowmeters, with good agreement between measured and computed values. For any given arrangement there is an optimum frequency of operation, and different frequencies can give information about the velocity distribution.
Relativistic Brillouin flow in the high ν/γ diode
Authors: Creedon John M.
Published: February 2003

Relativistic Brillouin solutions have been derived for electron flow in crossed electric and magnetic fields. The application of these solutions to the high ν/γ diode is discussed and an approximate analytical expression for the anode current is derived. Measurements of diode current are compared to the theoretical and empirical expressions for diode current which have been developed.
Total backscattering yields of 3–15-keV protons from polycrystalline Nb
Authors: Verbeek H.
Published: February 2003

Polycrystalline Nb samples were bombarded by 3–15-keV proton beams at normal incidence. The energy and angular distributions of backscattered positively and negatively charged particles were measured quantitatively. By means of the charged fractions measured previously, the energy and angular distributions of the total number of backscattered particles including the neutrals were obtained. Integration of the distributions over all energies and angles yield the total reflection coefficients. These are considerably lower than existing theoretical values.
Electrostatically driven overdense rf plasma source
Authors: Motley R. W. , Bernabei S. , Hooke W. M. , Jassby D. L.
Published: February 2003

We describe a radio-frequency plasma generator consisting of two collinear cylinders surrounding a magnetically confined plasma column, excited by up to 7 kW of power at 155 MHz. The source is capable of generating plasma densities of the order of mi/me times the critical density nc=meω2/4πe2. The plasma density, the efficiencies of plasma heating, and the ion and electron heating associated with this generator are described in detail.
Tensile strength and work hardening of ultrafine-grained high-purity copper
Authors: Merz M. D. , Dahlgren S. D.
Published: February 2003

Sputter-deposited high-purity copper specimens with grain sizes from 8.4 to 0.056 μm were tested in tension to investigate the influence of grain size on yield strength for small grain sizes. The smallest grain size in the sputter-deposited copper was a factor of 40 smaller than the smallest grain size previously available for yield-strength–grain-size studies of high-purity copper. The 0.2% offset yield strengths varied from 73.4 MPa for the coarsest-grained copper to 481 MPa for the finest-grained copper. The hardening was related to grain- and twin-boundary spacings. The yield strength obeyed the Hall-Petch relation even for the finest grain size of 0.056 μm, giving σy=6.39+3.74(l̄)−1/2 MPa, where σy is the 0.2% offset yield strength and l̄ is the mean intercept length (mm) between boundaries. The data agreed with the Ashby model, σ∼ (ε/l̄)1/2, only at very low strains (ε<0.001) for the specimens with very fine grain sizes (l̄⩽0.077 μm).
Growth of multineedles of tungsten caused by reaction of tungsten oxide with acetone
Authors: Okuyama Fumio
Published: February 2003

The growth of crystalline needles of tungsten on the tungsten substrate through chemical reaction between vacuum-deposited tungsten oxide and acetone vapors of (3–5) ×10−6 Torr was investigated with the aid of a field emission and a transmission electron microscope. A large number of tungsten needles were found to be grown by heating the substrate, onto which tungsten oxide had been deposited, initially at a temperature in the range ∼1500–1800 °K in acetone and then at a temperature between ∼2300 and ∼2600 °K in acetone-free vacuum. The needles were mostly [110] oriented and their number density amounted to ∼107/cm2. It is believed that the needle growth was closely related to the reduction of the oxide by carbon provided from acetone through the thermal cracking.
Effect of impurities and strain amplitude on slip in fatigue of niobium single crystals
Authors: Nine Harmon D.
Published: February 2003

The type of slip deformation and the fatigue life in torsional fatigue of niobium single crystals were found to depend on both the cyclic strain amplitude and the interstitial impurity content. Two different slip-type populations were observed. At low strain amplitude, one population showed persistent slip bands, but the other, fatigued under identical conditions, showed asymmetric slip and asymmetric deformation. Differences in the two populations were related to interstitial impurity content. It is suggested that interstitial impurities affect the slip type by inhibiting cross-slip of dislocations.
Studies of the optimum conditions for growth of rf-sputtered ZnO films
Authors: Khuri-Yakub B. T. , Kino G. S. , Galle P.
Published: February 2003

A technique for deposition of highly oriented rf-sputtered zinc oxide films on (111) gold, (111) silicon, (0001) sapphire, and fused quartz is described. The major parameters that were controlled during deposition are substrate temperature, input rf power, deposition pressure, and the deposition atmosphere. It was found that the best results were obtained with an rf power of 160 W, a deposition at 4 μ pressure in an 80 : 20 argon : oxygen mixture, and with the substrate temperature varied between 225 and 400 °C depending on the substrate. The deposition rate varied slightly around 120 Å/min, with very small variation for different substrates. The quality of the ZnO films was determined by reflection electron diffraction and scanning electron microscopy. Acoustic-bulk-wave and acoustic-surface-wave delay lines were made by this technique. In all cases, high coupling coefficients were obtained.
Transmission of a transient electromagnetic plane wave into a lossy half-space
Authors: Papazoglou T. M.
Published: February 2003

The problem of a causal transient plane wave incident at an arbitrary angle on a lossy half-space is considered. The frequency domain solution is inverted to the time domain through a detailed analysis of its features in the complex frequency plane. Previously derived results for the interface are extended to include the interior of the dissipative medium. The effect of frequency dependence of the conductivity and permittivity of the lossy medium is considered. The Debye dispersion model is adopted and is shown to be compatible with the analytical method employed. Numerical applications are provided for each case.
Anode phenomena in a collision-dominated plasma
Authors: Biblarz O. , Dolson R. C. , Shorb A. M.
Published: February 2003

Anodes display either a glow mode or a constricted mode in plasmas of interest for MHD generator applications. The purpose of this paper is to outline the conditions underlying the existence of anode constrictions or anode spots in conjunction with criteria governing the anode glow. A steady current flowing through velocity and thermal boundary layers is investigated. The sheath and the ambipolar region are considered from an approximation theory viewpoint, and then the nonexistence of a one-dimensional Cartesian or diffuse mode for a nonreacting anode region is shown using the continuum equations for electrostatic probes.
Memory switching in glow discharge polymerized thin films
Authors: Pender L. F. , Fleming R. J.
Published: February 2003

Two distinct forms of memory switching have been observed in thin films (500–4000 Å thick) of glow discharge polymerized styrene, acetylene, benzene, and aniline. These two forms, called the high-voltage switching regime (HVSR) and the low-voltage switching regime (LVSR) are characterized by high (≳20 V) and low (1–5 V) threshold voltages, respectively. Their occurrence depends on three parameters; namely, electrode thickness, film thickness, and the nature of the ’’forming’’ atmosphere. The low-resistance (switched on) state of both modes is associated with highly conductive filaments. It is suggested that in the HVSR the filaments are metallic and result from localized fusing of the two electrodes, the intervening polymer film having been completely vaporized. In the LVSR the filaments are thought to be of carbon, formed from localized pyrolysis of the polymer film.
Preparation and optical properties of Ga1−xInxN thin films
Authors: Osamura Kozo , Naka Shigehisa , Murakami Yotaro
Published: February 2003

By the use of the electron beam plasma technique, it has been found that the solid solutions of Ga1−xInxN can be synthesized over the entire composition region. From the optical measurements, the direct energy gap at 78 °K was determined to be 3.46 eV for GaN and 2.11 eV for InN. Also its composition dependence was found to deviate downward from linearity. From the infrared reflectivity measurement and the resultant K-K dispersion analysis, the transverse optical frequencies for long-wavelength phonons of GaN and InN were 563 and 478 cm−1, respectively. The optical phonons in this quasibinary system were concluded to exhibit a one-mode–type behavior. The Brout sum rule was discussed for a large number of the diatomic crystals of ANB8−N type and its relation with respect to the reduced mass was derived as Σiω2i(k=0) =A μ−1.5. According to this relation, the longitudinal optical frequency of InN was deduced to be 694 cm−1. On the other hand, from the result of the annealing treatment for the solid-solution alloys and the theoretical consideration, it was pointed out that this quasibinary system has a solid-phase misibility gap in chemical equilibrium.
On the theory of diffraction by holographic gratings
Authors: Storck E. , Wolff U.
Published: February 2003

The well-known results given by the theory of coupled waves for the diffraction of light by volume holograms are shown to go over into Born’s first approximation in the case of low diffraction efficiency. They are, therefore, valid over the whole range of thick and thin holograms with and without Bragg incidence.
A nonlinear coupled-wave theory of holographic storage in ferroelectric materials
Authors: Vahey David W.
Published: February 2003

A theory is presented that describes the time evolution of the diffraction properties of holographically formed thick phase gratings in ferroelectrics, particularly in iron-doped lithium niobate. The theory is based upon a model that relates the instantaneous electromagnetic fields in a grating to the refractive index in a manner consistent with the work of Young et al.; that is, the index modulation amplitude is proportional to the product of the amplitudes of the writing fields, while index maxima and intensity maxima are spatially shifted by some fraction of a fringe. The model leads to coupled nonlinear equations for the writing fields that are analogous to the linear equations of Kogelnik, and in certain limits, yield identical results. Closed-form solutions of the coupled nonlinear equations are found to describe the interaction between writing beams observed by Staebler and Amodei, as well as the time evolution of diffraction efficiency observed by Amodei et al. In conjunction with the latter experiment, the present theory affords a striking verification of the grating formation concepts of Young et al.
Photoresponse of the GaAs controlled field avalanche photodiode (CFAPD)
Authors: Piqueras J. , Muñoz E.
Published: February 2003

A GaAs metal-semi-insulating-p-n+ avalanche photodiode has been evaluated as photodetector in current gain and spectral response. The influence of deep chromium levels on the behavior of the device in the semi-insulating region has been taken into account. A donor level at 0.56 eV and an acceptor level at 0.93 eV from the conduction band have been detected by photocurrent and photocapacitance measurements. An internal current gain, due to avalanche multiplication higher than 104, has been obtained. Spectral response is extended up to 1.61 μm.
Microwave-optical experiment on bismuth-substituted yttrium iron garnet
Authors: Takeuchi Hiroshi , Mikami Itsuo , Taniguchi Satoshi
Published: February 2003

Microwave-optical experiments were made on a bismuth-substituted yttrium iron garnet Y2.55Bi0.45Fe5O12. It was shown that about a 1% amplitude modulation of He-Ne laser (6328 Å) will be obtained for the analyzer set at 45° if we input 12 mW microwave (9180 MHz) power. It was also shown that the degree of modulation depends not only on the Faraday effect but also on the Voigt effect in general.
Current flow in large Josephson junctions
Authors: Barone A. , Johnson W. J. , Vaglio R.
Published: February 2003

Some aspects of current flow in large Josephson junctions are discussed within the approximation of a linear current-phase relationship. The behavior of various geometrical junction configurations, widely employed in practice, has been investigated.
Mass-spectrographic analysis of high-Tc Nb-Ge sputtered films
Authors: Santhanam A. T. , Gavaler J. R.
Published: February 2003

Secondary ion mass spectroscopy (SIMS) has been used to determine the concentration profiles of niobium and germanium in high-Tc (22 K) Nb-Ge films which were deposited onto polished sapphire substrates by a low-energy sputtering technique. X-ray lattice parameter data on such films indicate that in some cases their average composition is Nb-rich nonstoichiometric Nb3Ge. The SIMS analysis reveals a nonuniform composition within these sputtered films. The Ge concentration increases with film thickness but at least a portion of the film has the stoichiometric Nb3Ge composition. The occurrence of high critical temperatures in such films is thus still compatible with the hypothesis that the highest Tc’s in the Nb-Ge system are due to the presence of the stoichiometric or near-stoichiometric Nb3Ge compound.
Contribution of active transport current to the effective membrane impedance
Authors: Strandberg M. W. P.
Published: February 2003

It is shown that a membrane which supports active transport of ions will have an impedance which differs from that represented by the passive distributed resistance and capacitance (1) if the active transport current magnitude varies with transmembrane potential and (2) if the active transport current relaxes to its stationary value with a finite relaxation time after a small change in membrane potential. The low-frequency electrical impedence reported for the isolated frog skin is discussed from this point of view. A physically plausible explanation for the offset of the impedance circle observed in these data and commonly observed in similar data is offered.
Threshold switching in melanin
Authors: Culp C. H. , Eckels D. E. , Sidles P. H.
Published: February 2003

Threshold-switching measurements of synthetic melanin confirm that this organic semiconductor switches to a low-resistance state in low electric fields as reported by McGinness et al. Time-dependent current-vs-voltage curves show that the time to traverse the negative-differential-resistance (NDR) segment is much slower than would be expected from electronic-switching mechanisms. Double-pulse measurements add to the evidence that thermal effects dominate electronic effects in melanin. A pseudomemory effect was found in melanin.
Current-fluctuation noise in toad urinary bladder during active transport of sodium ions
Authors: Strandberg M. W. P. , Hammer Earle I.
Published: February 2003

The voltage-fluctuation noise spectrum appearing across the excised urinary bladder of the female Dominican toad Bufo marinus during active transport of sodium is identified as arising from random current fluctuations in the sodium-ion active transport current. The noise is observed to disappear with the sodium-ion active transport blocked when the bladder is bathed in choline Ringer solution. The noise magnitude with the bladder open-circuited and with the bladder short-circuited is proportional to the sodium-ion active transport current. The open-circuit active transport current is taken to be equal to the Ohmic current through the bladder resistance at the resting potential. The short-circuit active transport current is taken to be equal to the external current that must be injected into the bladder to drive the transbladder potential to zero. The bladder resistance is determined from the measurement of the frequency-dependent impedance of the bladder. Interpretation of the voltage-fluctuation spectral density according to the theoretical expressions for current-fluctuation noise indicates that the fluctuations are produced by the correlated movement through the bladder of a large number of sodium ions, carrying approximately 5000 electronic charges in a time of 0.02 sec.
Improved performance of an electric-discharge N2-CO mixing laser
Authors: Brunet Henri , Mabru Michel
Published: February 2003

An electric-discharge CO mixing laser is described in which N2 is vibrationally excited in a discharge and then mixed with cold CO providing laser action between 5.0 and 5.8 μ in a low-pressure high-Mach-number channel. Results of experiments with a 21-cm-wide 1.3-cm-high channel are described. Maximum laser power obtained is 720 W corresponding to an efficiency of 7% and a specific power of about 21 kW  (kg/s)−1.
Dynamic tensile strength of mercury
Authors: Carlson G. A.
Published: February 2003

The dynamic tensile strength of mercury has been determined using very-short-duration (∼100 ns) stress pulses generated by an electron-beam machine. Tensile strengths of 1900 MPa (19 kbar) are observed for mercury at maximum tensile stress rates of ∼75 MPa/ns. These results are somewhat lower than the value of 3000 MPa predicted by homogeneous nucleation theory.
Interfacial impurities and the reaction between Si and evaporated Al
Authors: Best John S. , McCaldin J. O.
Published: February 2003

As commonly formed, the interface between substrate Si and evaporated Al is laden with impurities; subsequent heating causes modest dissolution of Si into solid Al, the dissolution morphology being influenced by the interface impurities. In the present experiments, the amount of Si dissolving was considerably enhanced, causing sufficient interface movement to carry most interfaces clear of the original impurities. Under these conditions, the Si/Al interface assumes, during brief heat treatment, a simple shape composed of a few {111} facets. Such Si/Al interfaces produced in situ should be useful for low-temperature solid-state growth of Si.
Short pulses tunable in the 0.69–0.99-μ range from N2 laser pumped dye solutions
Authors: Lin Chinlon
Published: February 2003

Subnanosecond pulses tunable in the 0.69–0.96-μ range, and nanosecond pulses tunable up to 0.99 μ, have been obtained from N2 laser (λ=337 nm) pumped dye lasers. These are achieved as a result of the recent availability of new efficient near-ir laser dyes for direct uv pumping, and the application of the technique of controlled resonator transients.
Kinetic effects in the electrical response of a shock-compressed ferroelectric ceramic
Authors: Lysne P. C.
Published: February 2003

Projectile impact experiments were conducted on specimens of PSZT 70/30-6. The shock-wave-induced depolarization of this material has an equilibration time of ?0.2 μsec which is similar to that of other ferroelectric ceramics. However, PSZT 70/30-6 does not revert rapidly to a poled state upon unloading. Thus, a nearly constant voltage is produced in our axial-mode experiments even though shock and release waves reverberate within the specimens. This interesting response of PSZT 70/30-6 is likely caused by a phase transformation near 0.3 GPa.
Preparation of thin windows in silicon masks for x-ray lithography
Authors: Schmidt C. J. , Lenzo P. V. , Spencer E. G.
Published: February 2003

Soft x-ray lithography requires the fabrication of thin windows in a material which is relatively transparent at the wavelength of the x rays used. A system under evaluation employs Al Kα radiation, thin window silicon masks, and pattern written in gold on the thin silicon membrane. Windows of uniform 1–5 μ thicknesses up to ∼4 cm in diameter have been made. A description is given of the procedures we now use for producing the complete masks. The etching itself takes 15–45 min. The procedures are uncritical and lend themselves to semiautomated operation. The yield for the etching procedure alone is close to 100%.
Self-mode-locking of an iodine photodissociation laser
Authors: Pirkle R. J. , Davis C. C. , McFarlane R. A.
Published: February 2003

The observation of self-mode-locking of an iodine photodissociation laser is reported. A typical laser output takes the form of a train of fully or partially mode-locked relaxation spikes. Simultaneous oscillation on at least eight longitudinal modes and locking of both longitudinal and transverse modes have been observed.
Total reflection of a Gaussian beam from an inhomogeneous medium
Authors: Kozaki S. , Mushiake Y.
Published: February 2003

For the purpose of radio and optical propagation, it is of practical importance to study how the shape of a Gaussian beam is deformed by a total reflection from an inhomogeneous medium. A fundamental problem, where the two-dimensional Gaussian beam is obliquely incident on the boundary surface between a homogeneous half-space and an inhomogeneous half-space whose permittivity decreases linearly in one direction, is analyzed. The theoretical result obtained by means of a Fourier transform is valid for cases of a collimated beam and a slowly varying medium. The characteristics of the reflected beam after it has propagated through the inhomogeneous medium are discussed. It is found for the first time that the shape of the reflected beam has the same form as an original beam when incident anlge φ is equal to the critical angle defined by φc=cos−1[({1±[1−2b (Z0+L)]1/2}/2)1/2]. When φ is not equal to φc, the reflected beam is deformed compared with the original beam.