bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical characteristics of ion-implanted p-channel MOS transistors
Authors: Nakamura Kunio , Kamoshida Mototaka
Published: February 2004

11B+ ions of 1011−1012/cm2 were implanted through gate oxides of 800–2000 Å into the channel regions of p-channel MOS transistors. For 50-keV implantation, the dose dependence of threshold voltage could be explained by Swanson and Meindl's theory. In the case of implantation above 100 keV, slight deviation of the threshold voltage from the theoretical values was observed. Corresponding to this, the gate-oxide-thickness dependence of the threshold voltage was slightly deviated from the theoretical values in the range of less than 1300 Å. For more than 1500 Å, the measured threshold voltages coincided with calculated values. The energy dependence of the dose limit for ``ability to turn on-off'' showed good agreement with the curve calculated on the basis of Swanson and Meindl's theory within this experimental error. Source-drain current in the saturation region was slightly increased with increasing dose at least up to 5 × 1011/cm2, presumably due to the carrier compensation (band bending) and increase of the mobility. No significant change due to the implantation was observed in the breakdown voltages within the examined dose and energy ranges. Device stability was confirmed by the positive or negative BT treatments (125°C, 100 h and 300°C, 60 min). Again, no significant instabilities resulting from the implantation process was detected in this experiment.
Current injection and collection in a rectangular superconductor
Authors: Moreno Héctor , Rabinowitz Mario
Published: February 2004

A general two-dimensional analytical solution is presented for the problem of transport current injection from a normal conductor into a superconductor and collection back into a normal conductor. The current distribution is solved for the general case which takes in the full range from essentially point source to full-width injection and collection. The current distribution also represents that in a split-ring superconductor joined by a link of variable width, such as that in a Josephson junction. A comparison is made with current injection into and collection from a normal conductor. Computer calculations are included showing a virtual anomaly which is reconciled. Speculation is made regarding the formation of transport current vortices in an initially simply connected superconductor.
Current-voltage characteristics of superconducting tunnel junctions
Authors: Stewart W. C.
Published: February 2004

The lumped equivalent circuit model of a superconducting tunnel junction with a voltage-dependent normal conductance current represented by Ir = I0(V/V0)n is analyzed for the cases n = 2 and n → ∞. Analytic expressions for the hysteresis parameter as a function of the damping factor are obtained. The time-averaged voltage-current characteristics for n = 2 are given in closed form. The results are qualitatively similar to the linear conductance case where n = 1, but the hysteresis is more pronounced for larger n.
Electronmicroscopic evidence for a columnar-void-type structure in sputtered NbN films
Authors: Wagner W. , Ast D. , Gavaler J. R.
Published: February 2004

Transmission electron microscopy of sputtered NbN films shows that the films contain columnar grains with an average axial diameter of 100 Å or less. A large number of narrow (≈ 20 Å) voids separate most of the grains. The voids extend through the film and are probably responsible for the strong pinning observed in these films. The high resistivity and relatedly the high upper critical field values of the films are also believed to be due to this columnar-void structure.
Application of ion-milling techniques to microparabolic surface formation
Authors: Yasuda Hiroshi
Published: February 2004

A study has been made on a microparabolic surface formation by ion bombardment. The 10-keV argon ion beams focused to about 30 μm in diameter were scanned electrostatically in a programmed manner to make a parabolic surface of a 200 × 200-μm2 area on a Si single crystal. The curvature of the formed surface was related to the total number of the ions which bombard the target. Some features of this formation technique are discussed.
Positive column of the Cs–Ar low-pressure discharge
Authors: van Tongeren H.
Published: February 2004

A model for the positive columns of dc low-pressure discharges in Cs–Ar mixtures, which includes radial depletion of Cs ground-state atoms and radiation trapping, is presented. The available experimental data for this discharge system were extended in such a way that comparison could be made between model calculations and experiments for a wide range of discharge currents and Cs vapor densities (0.2 × 1019−3.0 × 1019 m−3) and a reasonable agreement is obtained.
Monte Carlo simulation of the kinetics of heterogeneous nucleation
Authors: Michaels A. I. , Pound G. M. , Abraham Farid F.
Published: February 2004

This paper describes a computer simulation experiment which reproduces, upon an idealized (100) cubic crystalline surface, the atomic processes occurring in condensation, evaporation, and surface diffusion. Nucleation of two-dimensional clusters was observed. The equilibrium distribution of cluster sizes and the critical cluster size were measured for various parameter values and compared to predictions of the Walton-Rhodin atomistic nucleation theory. Very good agreement between the simulation and theoretical values was obtained. The nucleation rate was also measured for one particular set of parameter values and found to agree satisfactorily with the atomistic theory prediction. Consequently, we conclude that the Monte Carlo method is suitable for the simulation of the phenomena of heterogeneous nucleation. Suggestions are offered for the refinement and extension of the simulation model for future simulation experiments to help answer the unresolved questions of heterogeneous nucleation theory.
Search for correlations between dielectric relaxation and polymerization in trioxane crystals
Authors: Reneker D. H. , Martin G. M. , Broadhurst M. G.
Published: February 2004

After exposure to ionizing radiation, trioxane polymerizes rapidly at temperatures between 50 and 60°C. The nature of the molecular motions involved in this solid-state reaction is not clear. Line narrowing in nuclear magnetic resonance absorption has been reported as one indication of such motions. No related dielectric loss peaks were found in trioxane at temperatures from −180 to 55°C and frequencies from 1 to 10 000 Hz. Ionic conductivity is large above room temperature and it may play an important role in this polymerization reaction.
Second harmonic generation and parametric excitation of surface waves in elastic and piezoelectric solids
Authors: Tiersten H. F. , Baumhauer J. C.
Published: February 2004

Nonlinear electroelastic equations, quadratic in the small field variables, are applied in the analysis of second harmonic generation of surface waves in piezoelectric solids. Preliminary to the treatment of the anisotropic piezoelectric case, the more tractable problems of the second harmonic generation and parametric excitation of surface waves in isotropic elastic solids are treated. In all instances the solutions asymptotically satisfy the nonlinear differential equations and boundary conditions on the surface of the semi-infinite solid to a specified order in a small parameter. Since the equations are quadratic rather than cubic in the small field variables, only initial spatial rates of growth of the harmonically generated and parametrically excited waves are determined. Nevertheless, an extension of the analysis to enable the calculation of more than the aforementioned initial slopes is indicated. In the isotropic elastic case the solution for the second harmonic reveals, among other things, that the ratio of the dilatational to equivoluminal portions of the growing second harmonic is the same as in the input Rayleigh wave.
The kernal of Sommerfeld's transform as solution to difference equations for a class of diffraction problems
Authors: Van Lennep A. G. R.
Published: February 2004

The complete solution of certain diffraction problems can be found in the form of a Sommerfeld integral. To obtain solutions in this form, a kernel must be obtained. There are no doubt, many different techniques for finding them. However, in solving the two-dimensional problem in a wedge-shaped region, Malyuzhinets demonstrates that the kernel (except for a periodic factor) is the solution to a difference equation. He gives conditions and proves theorems about this fact. For such problems as he treats, no immediate method is clearly discernible for obtaining the solution of this difference equation. This paper will fill that void.
Study of deformation in polytetrafluoroethylene by x-ray line broadening
Authors: Wecker S. M. , Cohen J. B. , Davidson Theodore
Published: February 2004

The effect on PTFE of crystallization conditions and subsequent tensile deformation have been examined by Fourier analysis of the shapes of diffraction peaks. Crystal perfection increases with decreasing rate of cooling from the melt. During deformation, the crystallite size is reduced drastically in the range of strain from 35 to 185%. The microstrains are not altered over this range, implying crystal breakup rather than distortion within crystallites. It is in this range that previous studies with the same specimens have indicate a sharp transition in texture. The fact that root-mean-square (rms) microstrains increase due to elongation suggests that the crystalline regions not only break up but that they are also deforming plastically. Electron microscopic investigation indicate that the striation spacing on crystals in the fracture faces is much smaller than the crystallite size measured with x-rays; thus the striations do not represent alternating crystalline and amorphous regions.
Inductance bridge for current-quantum-phase measurements in superconductors at zero frequency
Authors: Meservey R. , Paraskevopoulos D. , Gruenberg L. W. , Tedrow P. M.
Published: February 2004

A zero-frequency bridge has been developed for measuring the inductance and the current-vs-quantum-phase relation of superconductors. The current null detector is a SQUID magnetometer coupled to the bridge by a superconducting transformer. The bridge is balanced by adjusting precision resistors at room temperature. The theory of the bridge and analysis of the null-detector circuit for optimizing the sensitivity are given. For current-dependent inductors, a definition of inductance based on the quantum-phase difference is shown to be useful. Construction and operation of the bridge are described and measurements of inductance vs temperature for Al thin-film meander lines are presented. Zero-frequency measurements avoid the stray coupling to capacitances and normal metal inductances found in high-frequency measurements and the method could give high-precision absolute measurements. The sensitivity of the present instrument is such that an inductor of 4×10−7 H was measured to a relative precision of one part in 104 with a measuring current of 5×10−6 A. Considerable improvement is possible, especially for circuit elements of very small inductance such as Josephson junctions and weak-link superconductors.
Uniaxial stress component in tungsten carbide anvil high-pressure x-ray cameras
Authors: Singh A. K. , Kennedy George C.
Published: February 2004

A method is proposed to detect the presence of a uniaxial stress component in samples belonging to the cubic system, pressed in a tungsten carbide anvil x-ray camera unit. The method is based on fitting the experimental data to an expression of the form εw(hkl)=εwp−m t(C11+4C12−2C44)/2 (C11+2C12)(C11−C12+3C44)+n t [S12+(S11−S12−S44/2) Γ(hkl)], where εw(hkl) is the strain calculated from the shift of the diffraction line (hkl) at a load w applied between the anvils, εwp is the strain arising from the hydrostatic component of the stress p, t is the uniaxial stress component, and Γ(hkl)=(h2k2+k2l2+l2h2)/ (h2+k2+l2)2. If the state of stress continuity in the crystallites is assumed, then m =0 and n =1; and m =1 and n =0 if the state of strain continuity in the crystallites is assumed. The experimental data for Si at w = 1400 kg and for NaCl at w = 510 kg indicate a linear dependence of εw(hkl) on Γ(hkl) as is expected for n ≠0. The slope of the εw(hkl) versus Γ(hkl) plot is negative for Si and positive for NaCl; this is in agreement with the theory as the value of (S11−S12−S44/2) is positive for Si and negative for NaCl, and t, being a compressive stress, is negative by convention. The lowest estimates of t, made from the slope of the εw(hkl) versus Γ(hkl) plot, is obtained if m =0 and n =1 are assumed. The slope of the εw(hkl) versus Γ(hkl) plot shows a considerable variation from run to run. For Si, for example, the lowest estimate of t varied between 21±4 and 32±4 kbar in the four runs made at w = 1400 kg. For NaCl, the lowest estimate for t varied between 4.2 ± 1.5 and 5.5 ± 1.5 kbar in the six runs made at w = 510 kg.
Dielectric properties of fresh and sea ice at 10 and 35 GHz
Authors: Vant M. R. , Gray R. B. , Ramseier R. O. , Makios V.
Published: February 2004

A free-space and in-waveguide dielectric constant measurement facility at 10 and 35 GHz is described. Results are presented for the dielectric constant and loss of both fresh and sea ice at these frequencies, and are interpreted in terms of a dielectric model of sea ice. Suggestions are made for possible improvements in the model and the measurement technique.
Transport of excess charge in electron-irradiated dielectrics
Authors: Gross B. , de Oliveira Luíz Nunes
Published: February 2004

Irradiation of dielectrics with nonpenetrating electron beams has been used for practical purposes, e.g., manufacturing of electrets, and as a research tool, e.g., the investigation of induced conductivity and transport properties. The present paper develops some aspects of the theory of charge transport and storage and radiation-induced conductivity in irradiated dielectrics. It is assumed that the dielectric is kept in short circuit and that the range of the incident electron beam is smaller than half the sample thickness. The treatment applies only to dielectrics which have a very low dark conductivity and contain a great number of deep traps.
Gap excitation of an axial conductor in a circular tunnel
Authors: Hill David A. , Wait James R.
Published: February 2004

We consider the excitation of modes on an axial conductor in a circular tunnel by a circumferential gap. Numerical results are presented for the power into the monofilar mode and the attenuation of the mode. The power delivered to the monofilar mode increases as the conductor approaches the tunnel wall, but the attenuation also increases. The results have application to systems which use coaxial cables for long-distance communication in mine tunnels.
Behavior of electron-emitting plasma probes in the space-charge-limited regime
Authors: Schuss J. J. , Parker R. R.
Published: February 2004

The properties of cylindrical electron-emitting plasma probes are reviewed. Poisson's equation is formulated and solved for a cylindrical emissive probe biased several volts negative of plasma potential and operating in the space-charge-limited regime. It is shown that in this regime the emitted current at fixed voltage is proportional to the reciprocal of the Debye length. The theory is shown to be in good agreement with experimental results. Expected deviations of probe behavior from the theory and the theory's limitations are discussed. Due to the emission limitations of such probes the technique appears useful only for those plasmas whose Debye length is greater than about 10−2 cm.
Hot electron galvanomagnetic conduction in cadmium sulfide— a Monte Carlo investigation
Authors: Chattopadhyay D.
Published: February 2004

Hot electron transport coefficients of cadmium sulfide in crossed electric and magnetic fields have been calculated by the Monte Carlo method at a lattice temperature of 77 °K. Piezoelectric, deformation-potential acoustic-mode, polar-mode, and ionized impurity scattering are included in the calculations. The application of a magnetic field increases the drift mobility at high electric fields. The Hall-to-drift-mobility ratio is found to increase and then decrease with increasing electric field. Its value is reduced as the magnetic field is raised.
Optical spectra and laser action in Nd3+-doped CaY2Mg2Ge3O12
Authors: Sharp E. J. , Miller J. E. , Horowitz D. J. , Linz A. , Belruss V.
Published: February 2004

Crystals of the garnet-structured germanate CaY2Mg2Ge3O12 have been grown from a melt containing 6 mole% Nd3+. The fluorescence, absorption, excitation spectra, lifetime, and linewidths have been measured and were compared with the results for Nd3+:YAG. The important spectroscopic features of Nd3+:CaY2Mg2Ge3O12 are a lifetime of 305 μsec, a strong absorption in the near infrared, a very intense fluorescence line at 941 nm, and a linewidth at this wavelength of approximately 37 cm−1. Laser action has been achieved at 1058.96 nm at room temperature. An estimate of the laser transition cross section gives a value of σ=6×10−20 cm2.
Single-heterostructure PbS(1−x)Sex diode lasers
Authors: Sleger K. J. , McLane G. F. , Strom U. , Bishop S. G. , Mitchell D. L.
Published: February 2004

PbS(1−x)Sex single-heterostructure diode lasers have been fabricated using a 300 °C vacuum deposition process to grow layers of p- or n-PbS0.72Se0.28 onto n-PbS0.78Se0.22 bulk substrates. At 12 K, laser emission occurs at 4.98 μm in the grown PbS0.72Se0.28 layer. Maximum power outputs are on the order of 1 mW. The 0.20% lattice mismatch at the heterojunction does not impose serious limitations on laser performance.
Observation of Lamb dip for an HF chemical laser
Authors: Bonczyk P. A.
Published: February 2004

Lamb dips are observed for ν=1−0, P(4)−P(10) and ν=2−1, P(4)−P(8) HF laser lines. The dip shape is strongly dependent upon molecular rotation.
Universal stain/etchant for interfaces in III-V compounds
Authors: Olsen G. H. , Ettenberg M.
Published: February 2004

The application of the A-B dislocation etch to the delineation of interfaces in III-V compounds is described. The etchant is easy to use and has worked on all III-V compounds tested to date.
Electro-optically induced deflection in liquid-crystal waveguides
Authors: Sheridan J. P. , Giallorenzi T. G.
Published: February 2004

This paper describes electro-optically induced tunable deflection in the plane of a waveguide structure by utilizing the liquid-crystal property of tunable birefringence together with appropriately designed electrodes. The magnitude of tunable deflection achieved in this experiment (>20°) had only been demonstrated in passive structures in the past. Furthermore, by changing the device parameters slightly, electrically controlled total internal reflection or refraction in the plane of the waveguide structure was demonstrated. This allowed operation of the device as a switch where the guided beam was deflected or ``switched'' through a very large angle (>70°) in the plane of the guide.
Study of an electron-beam discharge into a vacuum diode with polyethylene anode
Authors: Kerns J.R. , Johnson D.J.
Published: February 2004

A 40-nsec-duration 2.5-MV 25-kA electron-beam discharge into a vacuum diode with polyethylene anode has been studied with time-resolved optical photography and soft x-ray diagnostics. The beam was observed to be initially uniform but to filament at 15 nsec and form a single powerful pinch at 25 nsec. The interaction of the pinched beam and the anode produces a plasma ≤ 75 μm in diameter with a temperature of ∼ 50 eV. Neutron and deuteron emission from the diode were observed and the intensity ratios are consistent with a beam target neutron production mechanism.
Hot-spot model of K-line emission from laser-heated plasmas
Authors: Whitney K. G. , Davis J.
Published: February 2004

A nonhydrodynamic model is developed to describe x-ray emission from laser-heated plasmas on a subnanosecond time scale. The model is first correlated with the experiment and then is used to study the conversion efficiency of laser energy to K-line x rays in carbon, fluorine, and aluminum plasmas as a function of incident laser intensity. It is found that these conversion efficiencies peak at well-defined values of input energy per area for laser pulse widths smaller than the pumping times for K-line emission. In this case, the degree and not the rate of plasma heating is important in determining the peak conversion efficiency. It is also found that peak conversion to K radiation in excess of roughly 10 or 20% occurs only when the C, F, and Al plasmas are optically thick to the Ka lines.
Photoconductivity in solution-grown copper-doped GaP
Authors: Schulze R. G. , Petersen P. E.
Published: February 2004

High-resistivity copper-doped GaP has been prepared by solution growth from a copper-doped gallium melt. Photoconductive effects have been studied in these crystals. Compared to previously reported results these crystals are characterized by (i) high sensitivity at lower light levels, (ii) faster response time, and (iii) extended short-wavelength spectral response.
Quantum oscillations of the Hall effect in pyrrhotite
Authors: Sakkopoulos S. , Theodossiou A.
Published: February 2004

This is a report of measurements of the Hall resistivity on natural single crystals of pyrrhotite. When the applied magnetic field is normal to the c axis (ferrimagnetic sample) the Hall resistivity exhibits oscillations with an increasing magnetic field. Such oscillations were detected when the sample was kept at 77°K. The period and the damping of the oscillations permit the calculations of the cross section of the Fermi surface, normal to the field, the cyclotron effective mass of the carriers, and also the Fermi energy. The same sample at room temperature does not exhibit oscillations. In the paramagnetic sample, cut so that the applied field is parallel to the c axis, no oscillations are detected.
The motion of 180° domain walls in uniform dc magnetic fields
Authors: Schryer N. L. , Walker L. R.
Published: February 2004

The equations of motion of a 180° domain wall in an infinite uniaxially anisotropic medium which is exposed to an instantaneously applied uniform dc magnetic field H0 have been integrated numerically. Below the critical field Hc =2παM0 (α is the Gilbert loss parameter and M0 the saturation magnetization), where a steady-state solution is known to exist, it is shown that the wall motion tends smoothly to this solution. Above Hc, the magnetization precesses about the field and a periodic component appears in the forward motion of the wall. Analytic solutions for the wall motion have been found based upon approximations suggested by the computed behavior; these reproduce the computer results very accurately.
Effects on interface barrier energies of metal-aluminum oxide-semiconductor (MAS) structures as a function of metal electrode material, charge trapping, and annealing
Authors: DiMaria D. J.
Published: February 2004

Energy barrier heights at the interfaces of metal-aluminum oxide-silicon structures have been measured via internal photoemission as a function of metal electrode material, premetallization annealing treatment, and charge trapping. Barrier heights at the Si–Al2O3 interface were insensitive to gate metal, annealing treatment, and charge trapping. Zero-field energy barriers for the Au, Ni, Al, or Mg and Al2O3 interfaces were found to be 4.1±0.1, 3.7±0.1, 3.2±0.1, and 2.5±0.1 eV, respectively. Effects of charge trapping on the barrier height were measurable only for the Mg–Al2O3 interface. Annealing treatments had no effects on barrier heights within the accuracy of the measurement technique.
On the Γ-Γ and Γ-X transitions of the GaxIn1−xP alloys
Authors: Joullie A. M. , Alibert C.
Published: February 2004

The temperature dependence of EΓΓ=Γ6c−Γ8ν is studied by piezoreflectance from 8 to 300°K. The variation is linear from 100 to 300°K with a temperature coefficient β=(−4.6±0.4) × 10−4 eV/°K for x =0.51. At low temperature the bowing parameter of the parabolic variation of EΓΓ vs x is 0.42 eV. At room temperature, electroreflectance measurements give 0.49 eV. The X6c−Γ8ν indirect gap is measured by electrotransmission. At room temperature the Γ-X crossover composition is xc =0.63±0.02 and the corresponding energy EΓΓ= EΓx=2.14±0.01 eV. For T < 10°K, xc =0.69±0.02 and EΓΓ=EΓx=2.32±0.01 eV.
E-I characteristic of stable free-burning arcs at high currents
Authors: Ramakrishnan S. , Stokes A. D.
Published: February 2004

Stable free-burning arcs have been obtained for currents ranging from 4 to 17 kA with the use of specially shaped electrodes. The E-I characteristic of the arc has been measured by the arc-lengthening procedure and by use of electrostatic probes. The arc exhibits a flat E-I characteristic in the current range considered.
Effects of cesiation on secondary-electron emission from MgO/Au cermets
Authors: Henrich Victor E. , Fan John C. C.
Published: February 2004

The effect of Cs adsorption on secondary-electron emission from MgO/Au cermets has been studied by both a rapid yield measurement technique and Auger electron spectroscopy. The presence of Cs enhances the emission from these materials, but the Cs is weakly bound and is easily removed by electron bombardment. The emission is not adversely affected by the possible alloying of Cs with Au.
Lattice location of low-Z impurities in medium-Z targets using ion-induced x rays. I. Analytical technique
Authors: Chemin J. F. , Mitchell I. V. , Saris F. W.
Published: February 2004

The usefulness of ion-induced x-ray yields to detect low-Z impurity atoms at low concentration in medium-Z targets and to locate their lattice sites in single crystals is established in this and the paper that follows. In paper I we describe the technique used with specific reference to phosphorus and sulfur implants in germanium crystals. Particular attention was given to the origin of the different components that constitute the backgrounds in the x-ray energy spectrum. Peak-to-background ratios for these two impurity signals were then determined for H and He ions in the energy region from 0.5 to 2.0 MeV. Some results for N and Ar ions were also obtained. A beam of 0.5-MeV H+ gave optimum conditions for foreign atom location studies.
Lattice location of low-Z impurities in medium-Z targets using ion-induced x rays. II. Phosphorus and sulfur implants in germanium single crystals
Authors: Chemin J. F. , Mitchell I. V. , Saris F. W.
Published: February 2004

In the preceding paper, Paper I, we described an analytical technique, based on ion-induced x-ray yields, for detecting low-Z impurities in medium-Z targets. In this paper, Paper II, we report the application of this method to the lattice location of impurity atoms. Two systems have been examined to test the method, viz., P and S implants in Ge single crystals. The channeling effect was applied to the phosphorus and sulfur K x-ray yields excited by 0.5-MeV protons. Some 93% of implanted 31P (0.7 × 1015 atoms cm−2, room-temperature implant, 450°C anneal), were found to occupy substitutional sites; the fraction dropped to [inverted lazy s] 63% for an implant dose of 2.7 × 1015 atoms cm−2. Channeling effect results in 〈110〉, 〈111〉, and 〈100〉 directions for Ge(S), implanted at room temperature and annealed at 450°C, prescribe a preferred off-lattice (> 0.3 Å) site for the sulfur, necessarily different from the regular tetrahedral or hexagonal interstitial sites. For hot (220°C) implantation conditions, poorer crystal annealing and weaker channeling effects were observed.
Induction coils coaxial with an arbitrary number of cylindrical conductors
Authors: Dodd C. V. , Cheng C. C. , Deeds W. E.
Published: February 2004

The vector potential has been obtained for a coil coaxial with an arbitrary number of cylindrical conductors. The derivation is quite general and employs an iterative process that has been adapted to computer programs. After the vector potential has been obtained, it is used to calculate the mutual and self-impedance of multiple and single coils, the effect of defects in the conductors on the mutual and self-impedances, and the induction heating density in the conductors.
Application of acoustic surface waves to the study of surface properties of ion-exchanged glass
Authors: Bucaro J. A. , Flax L.
Published: February 2004

Surface acoustic waves have been used successfully in the present work to study the mechanical properties of ion-exchanged glass surfaces. The surface wave velocity was measured as a function of frequency on an alkali-aluminosilicate glass before and after sodium for lithium ion exchange. The exchange was carried out at temperatures both above and below the transformation range of the glass and for various treatment times. The surface wave dispersion is explained in terms of depth-dependent changes in the density and modulus resulting from the concentration gradient caused by the ion exchange. An independent measurement of the density change has allowed a quantitative measurement of shear modulus change in the ion-exchanged layer. The experimentally determined dispersion curve agrees well with theoretical calculations at frequencies for which the latter are available. The presence of surface stresses has been detected by means of these measurements which has allowed a determination of their time dependence.
Circuit theory for a class of anisotropic and gyrotropic thin-film optical waveguides and design of nonreciprocal devices for integrated optics
Authors: Yamamoto Sadahiko , Makimoto Toshio
Published: February 2004

A circuit-theoretic treatment is presented for thin-film optical waveguides using a class of real anisotropic and gyrotropic materials. The analysis is based on the two-mode approximation in normal-mode theory. The terminal behavior of those guides is described by the 2 × 2 transmission matrix and expressions for matrix elements of six systems that are introduced as canonical elements in circuit synthesis are derived. Properties of canonical elements are discussed with particular attention on their reciprocity. Using the transmission matrix, we can treat the design of thin-film optical devices by a simple matrix operation familiar in conventional transmission-line circuit synthesis. As a typical application the design of various nonreciprocal integrated-optical devices is treated in detail. The desired response is synthesized by cascading selected canonical elements in an appropriate order. Examples include the gyrator, unidirectional mode converter, differential phase shifter, isolator, and circulator.
ac loss in a twisted filamentary superconducting wire. I
Authors: Carr W. J.
Published: February 2004

Calculations are made for the ac losses in a twisted filamentary superconductor by assuming a continuum model with anisotropic conductivity. The Maxwell equations are solved for a long wire of radius R0 and twist length L. In terms of the classical skin depth δ, appropriate for the conductivity perpendicular to the filaments, the losses are calculated for an applied magnetic field transverse to the wire axis in the case of (i) a uniform field (2 R0/δ≪1, L/2πδ≪1), (ii) shielding from surface currents (2 R0/δ≪1, L/2πδ≫1), and (iii) skin effect (2 R0/δ≫1). Losses are also calculated for the case of a transport current in no applied field. The model can be used in more general cases and has the virtue of giving precise results with a minimum of auxiliary postulates.
Electronic structure changes with room-temperature aging in supersaturated alloys of cadmium in zinc
Authors: Park J. K. , Gordon W. L.
Published: February 2004

The de Haas-van Alphen effect is used to determine the change of the Zn Fermi surface parameters in dilute Zn Cd alloys containing up to 1.2 at.% Cd. Its application in observing the change of the matrix band structure during room-temperature aging is demonstrated. The presence of local concentration gradients and strain fields in the matrix during precipitation produce strong phase-smearing effects.
Carrier concentration of Hg1−xCdxTe
Authors: Leonard W. F. , Michael M. E.
Published: February 2004

A comparison between commonly used expressions for the electron density in the nonparabolic conduction band of Hg1−xCdxTe is made. Calculations are carried out for compositions in the range 0.16≤x≤0.8 and a temperature of 80°K. The effect of the spin-orbit splitting Δ on electron density is examined.
Room-temperature grain growth in potassium chloride
Authors: Koepke B. G. , Anderson R. H. , Bernal G., E. , Stokes R. J.
Published: February 2004

The fine-grained structures produced in KCl crystals by press forging and rolling at elevated temperatures have been shown to be unstable at room temperature; large grains appear in the structures and grow at the expense of the fine-grained matrix. Some observations pertaining to the grain morphology, boundary migration rate, and suppression of the phenomenon are presented.
Computer simulations of vacancy and interstitial interactions with the (a/2) 〈110〉 edge dislocation in copper
Authors: Schiffgens J. O. , Ashton D. H.
Published: February 2004

All simulations are performed with a single interatomic potential, the general features of which are outlined in a paper by Johnson. Analyses of a vacancy, an interstitial, and a stable (a/2) 〈110〉 edge dislocation in copper are presented, along with calculations each describing a vacancy and an interstitial in static equilibrium at the edge of the dislocation. Vacancy and interstitial formation energies and associated strain patterns are calculated. The 〈100〉 split interstitial configuration is stable with a formation energy of 3.060 eV. The vacancy formation energy is 1.165 eV. The strain patterns agree well with those obtained by others. The (a/2) 〈110〉 edge dislocation on the {111} plane is positioned in the lattice according to a previously devised procedure which results in complete agreement between atomistic and continuum treatments in regions of small strain. Atomic displacements parallel to the dislocation line are analyzed and their variation with distance from the line is shown to be oscillatory and to damp out within about 9 Å of the line. The over-all significance of such displacements to dislocation core simulation is discussed. The core radius and energy are calculated to be 4.8 Å and 0.278 eV per (112) plane, respectively, and the core configuration is shown to be consistent with the short-range character of the potential. A lattice with 4080 atoms on 24 (112) planes is used to analyze the point-defect-dislocation interactions. With regard to a vacancy or an interstitial at the edge of the dislocation, each is bound to the dislocation having binding energies 0.247 and 0.800 eV, respectively. The atomic configuration and strain pattern associated with each bound defect are presented.
Defect centers in oxygen-deficient rf-sputtered SiO2 films. II. Thermoluminescence
Authors: Hickmott T. W.
Published: February 2004

Thermoluminescent (TL) glow curves of rf-sputtered SiO2 films deposited on silicon have been measured and correlated with two new defect centers detected by electron spin resonance (ESR) of the films, the HX and HY centers. As-sputtered films have low optical absorption and ESR absorption is dominated by the HY center. TL intensity is low after x irradiation. Annealing at 400°C in hydrogen, or at 550°C in nitrogen or oxygen, converts the HY center to the HX centers. TL intensity increases with annealing and goes through a maximum after annealing at 550°C in hydrogen or 650°C in nitrogen or oxygen. A characteristic TL glow curve pattern is associated with the HX centers. Trapping centers with energies of 0.74, 0.96, 1.04, and 1.20 eV are found. The complexity of TL glow curves is due primarily to variations in s, the frequency factor, rather than to a range of trap energies. It is proposed that trapping centers are associated with oxygen vacancies, and with Si–H bonds, in oxygen-deficient SiO2 films, while the recombination center is associated with bonding oxygens.
Solutions of the classical Boltzmann equation for He and Ne gas breakdown
Authors: Chan C. H. , Moody C. D.
Published: February 2004

A theoretical study of gas breakdown induced by intensive CO2 laser radiation is given. The basic assumption is that the gas breakdown is due to the process of cascade ionization. The Boltzmann equation for the electron energy distribution function is solved. Details of the numerical method and breakdown thresholds for He and Ne gases are given. The results are in reasonable agreement with the experimental results and are rather sensitive to the gas pressure.
Preflashover phenomena and electron-stimulated desorption in high electric fields
Authors: Panitz J. A.
Published: February 2004

The effect of high electric fields on the electron-stimulated desorption (ESD) of positive ions from metal surfaces has been studied at fields between 103 and 105 V/cm for electron energies between 1 and 20 kV. Adsorbed gases characteristic of the residual vacuum (10−9 Torr) were detected under all conditions, but ions characteristic of the substrate were only detected for fields approaching 105 V/cm. These observations confirm that previously reported preflashover anode metal ion species in an ultrahigh-vacuum diode originate at anode protrusions by a field evaporation process and that only residual gas species are produced prior to flashover by ESD. It is suggested that, if field emission processes at the cathode could be completely suppressed, electrical flashover would still occur, initiated and sustained by field-evaporated anode ions.
Electrogasdynamic generation using solid-gas suspension in turbulent pipe flow
Authors: Ho Kit-Fun , Coffee R. A.
Published: February 2004

The paper describes a study of the charge transfer of a solid-gas suspension in turbulent pipe flow. Using hollow glass spheres as the particulate phase, nitrogen and saturated air respectively as the gaseous phase, experiments were performed at flow rates of Reynolds number 5000–16000. Experimental results reveal that along a dielectric pipe there is strong electrification of the suspension, with particle electrification per pipe-diameter displacement of the order of - 10−5 C/kg, while along a conductor pipe the charge decay of the electrified suspension is of an empirical form (q/m)0 exp(−αl1/2), where l is the suspension displacement from the pipe entrance and α is a constant. In each case the pipe length was approximately 1 m, and the internal diameter approximately 1 cm. The process of charge transfer through particle-pipe impact is discussed, and an experimental EGD generator setup is described.
Study of the x-ray production mechanism of a dense plasma focus
Authors: Johnson David J.
Published: February 2004

The x-ray emission from a 375-kJ plasma focus is reported as measured on a time-resolved basis with Ross filters and silicon diode detectors. Thick-target electron beam spectra are calculated with a Monte Carlo electron beam transport program and fit to the experimental time-integrated x-ray spectra. A good fit is obtained with a 2-MA E−2 power law electron beam, with cutoff energies at 8 and 200 keV, incident normal to a thick tungsten target. The source of the beam is judged to be electrons which are accelerated under the influence of strong electric fields. A 20-nsec Q-switched ruby laser pulse injected tungsten ions via laser ablation prior to the initial dense pinch, and the x-ray emission below 4 keV was enhanced and that above 10 keV was reduced. The enhanced low-energy x-ray emission is in agreement with calculated radiation for collisional M-shell excitation of highly stripped tungsten in a 1.5-keV thermal plasma. A 900- μsec ruby laser pulse injected sufficient tungsten ions to degrade greatly the initial dense plasma pinch and reduce the beam target x-ray emission. The time-resolved x-ray emission from this configuration appeared as a smooth Gaussian function in time with FWHM∼200 nsec.
Injection of small macroscopic particles into plasmas as a diagnostic technique
Authors: Anestos T. C. , Hendricks C. D.
Published: February 2004

A method is presented for the determination of electron temperature of plasma by the measurement of the charge acquired by a small spherical macroscopic particle of the order of 20–25 μ in diameter as it travels through the plasma. The particles are generated by the electromechanical breakup of a liquid jet. A theoretical relation between the electron temperature and the particle charge is derived which allows the determination of the electron temperature after the charge of the particle is measured experimentally. Measurements of the electron temperature in argon and helium plasmas are done, and comparisons with Langmuir probe measurements show good agreement.
Two- and three-electron group models for low-pressure gas discharges
Authors: Vriens L.
Published: February 2004

In energy-balance calculations on low-pressure gas discharges it is often necessary to account for large deviations from Maxwellian electron-energy distributions. A method recently introduced for this purpose is extended here and is applied to Cs–Ar and Ar discharges. While the two-electron group model is still most satisfactory in describing excitation processes, the three-electron group model developed here makes it possible to deal more accurately with ionization processes.
Monitoring the moduli of polymers with ultrasound
Authors: Papadakis Emmanuel P.
Published: February 2004

Two ultrasonic methods are presented for the measurement and monitoring of the elastic moduli of polymers and other liquids undergoing solidification. The methods are thought to be most sensitive to the buildup of the real component of the modulus of rigidity of the material. Ultrasonic traveling waves are used to interrogate a boundary between the solid body transmitting the wave and the sample under test. Data on epoxy resins are given. During the hardening process, the measured modulus includes contributions from viscoelastic and glass transition effects which are not separated from the total modulus by the measurement methods.
Acousto-optic figure of merit of TeO2 for circularly polarized light
Authors: Yano T. , Watanabe A.
Published: February 2004

The intensity of the diffracted light in an optically active crystal by anisotropic Bragg diffraction has been observed to depend strongly on the polarization condition of the incident light. The acousto-optic figure of merit for this type of crystal, therefore, should be measured under careful selection of the polarization and geometrical condition of the incident light. The figure of merit Me(p2n6/ρv3) of a TeO2 crystal for the slowest shear sound wave propagation using circularly polarized incident light was found to be 1200 × 10−18 sec3/g at 6328 Å rather than 793 × 10−18 sec3/g, as was previously reported by using arbitrarily polarized light. The previous measurement does not give a correct value of Me, according to the theory given above.
Hot carriers in silicon surface inversion layers
Authors: Hess Karl , Sah C. T.
Published: February 2004

Calculations of the carrier mobility of electrons and holes vs the electrical field strength E are presented. The calculations have been performed based on a Maxwellian distribution and taking into account a repopulation of carriers among different valleys in the case of n-channel silicon inversion layers. The energy loss of the carriers to the lattice and the drift velocity or mobility are treated as two dimensional. Formulas for the energy loss are presented for both high and very low temperatures considering scattering by optical and acoustical phonons. The calculations are compared with experimental values given by Fang and Fowler and by Sato et al. Good agreement is found for the high-temperature case using coupling constants as given by Sah et al. Quite large differences between theory and experiment appear at very low temperatures. The origin of these differences is discussed in a final section.
An improved high-frequency MOS capacitance formula
Authors: Brews J. R.
Published: February 2004

Minority carriers within the inversion layer of an inverted MOS capacitor can move in response to a high-frequency ac signal even though the total minority-carrier charge is fixed at the value set by the dc bias. In this paper a simple explicit formula for the high-frequency capacitance which includes this ac inversion layer polarization effect is derived. The derivation is based upon the assumption that the distribution of minority carriers within the inversion layer is governed by a constant quasi-Fermi level, independent of position within the inversion layer. Hence, the resulting capacitance formula is restricted to the case where minority-carrier trapping by defects in the inversion layer or at the interface do not significantly hinder the ac response of the minority carriers. Comparison of the new formula with the calculations of Sah, Pierret, and Tole, which have as their main approximation the neglect of the ac minority-carrier movement, shows that the neglect of this effect leads to a 7% error in strong inversion at 1013/cm3. Comparison with the commonly used formulas of Lindner and of Grove, which contain approximations in addition to the neglect of inversion layer polarization, shows that these formulas are in error by 9% and 4%, respectively, in strong inversion at a doping level of 1013/cm3. Although more accurate than these other calculations in strong inversion, the Grove model is less accurate in depletion and weak inversion. Figures illustrating the error involved in all three earlier approaches as a function of bias with doping level as a parameter are presented.
Frequency shifts of self-oscillating magnetometer with cesium vapor
Authors: Yabuzaki Tsutomu , Ogawa Toru
Published: February 2004

The frequency shifts of a self-oscillating magnetometer with cesium vapor are studied quantitatively by solving rate equations for cesium atoms undergoing the action of a circularly polarized pumping light beam. Particular attention is given to the frequency shifts due to the line asymmetry of the rf spectrum in the light transmitted through the vapor. The line asymmetry varies with the orientation of the light beam relative to the field to be measured, the intensity of the light, and the temperature of the absorption cell. As an effect of a buffer gas, two extreme cases are considered, i.e., the optically excited state is in the complete mixing state and in the nonmixing state. The results show the fact that the frequency shifts depend largely on the collisional mixing in the excited state and on the sense of the circular polarization of the light. In order to reduce the frequency shifts, a new type of magnetometer, called the symmetrized spectrum magnetometer, is discussed, in which two circularly polarized light beams with opposite sense are simultaneously applied to a partitioned absorption cell.
Some superconducting properties of multifilamentary niobium carbonitride
Authors: Ohmer Melvin C. , Frederick William G. D.
Published: February 2004

Superconducting properties of multifilamentary 10-μ niobium carbonitride fibers have been investigated. Niobium carbonitride has Tc's to 18 K and Hc2's to 120 kOe. Critical current densities and their temperature dependence and the magnetic field dependence of the hysteretic loss have been determined from magnetization measurements. The fibers had Jc's in the range of 104 A/cm2 for fields less than 50 kOe at 4.2 K. No flux jumping was observed, indicating that the fibers were intrinsically stable without a stabilizing matrix. The field dependence of the hysteretic loss was ∝ H2.4 for partial penetration.
Polarization fluctuations in capacitive bolometers
Authors: Singh V. P. , van der Ziel A.
Published: February 2004

The noise resistance Rn of an ac open-circuited capacitive bolometer is measured as a function of the dc bias. It is found that the noise is larger than thermal noise and that the ratio Rn/Rs, where Rs is the loss series resistance of the device, increases with increasing bias and saturates for large bias. The observations are discussed in terms of spontaneous polarization fluctuations for a bias field.