bluuebunny/crossref_metadata_2025 huggingface dataset:
Differentiated electron-beam-induced current (DEBIC): Quantitative characterization of semiconductor heterostructure lasers
Authors: Parsons R. R. , Dyment J. C. , Smith G.
Published: February 2003

Differentiated electron-beam-induced current (DEBIC) is shown to be well suited for the study of semiconductor heterostructure lasers. The DEBIC signal, unlike the standard EBIC signal, is rich in fine-structure information in the vicinity of the active region. A simple model is introduced to explain the characteristic DEBIC signal. As a result of the anisotropy of the carrier distribution, higher spatial resolution (≲0.2 μm) is achieved with DEBIC than with the standard technique, EBIC (?1 μm). The DEBIC can be used to obtain diffusion lengths of the minority carriers and to evaluate the quality and uniformity of the device fabrication.
Magnetic analysis of an amorphous alloy magnet by electron diffraction
Authors: Yamaguchi S.
Published: February 2003

Magnetic analysis of an amorphous alloy magnet with high permeability and with low remanence was made in terms of electron diffraction. This alloy was composed of Co (66), Si (15), B (10), and Fe (9). The surface of the specimen was embedded with alumina particles which were able to give rise to distinct reflections. According to the analysis of the diffraction patterns obtained, the saturation induction of the specimen amounted to about 103 G, and its remanence proved to be negligibly small.
Solute-induced jump correlations during diffusive processes
Authors: Stark J. P.
Published: February 2003

Correlation effects which arise during self-diffusion are normally associated with a tracer-defect mechanism. It is not widely appreciated that diffusive mechanisms, which are not normally considered to be correlated, may become so as a consequence of crystal contamination. Two examples are given to illustrate the establishment of diffusive correlations by solute element contamination. The examples are interstitial diffusion in a dilute fcc ternary alloy and vacancy migration in a dilute binary fcc alloy.
Numerical analysis of electrical response: Statics and dynamics of space-charge regions at blocking electrodes
Authors: Franceschetti Donald R. , Ross Macdonald J.
Published: February 2003

The steady-state and transient electrical properties of a material containing one or two species of mobile charge carrier in contact with blocking electrodes are examined. The systems treated are 2, 20, and 40 Debye lengths in extent and exemplify the transition from thin-film or membranelike behavior to the more usual case in which well-defined space-charge layers form at each electrode. The static capacitance of the electrode/material/electrode system is examined and the response of the system to a step-function applied potential difference is obtained by numerical simulation. The simulation results show clearly the role of the system length and charge carrier mobilities in determining the system response. The decay of total current following the potential step is numerically fitted to a sum of exponential decays. The nonlinear character of system response becomes apparent when the transient current associated with the formation of space-charge layers in response to a potential step is compared with that which accompanies the decay of the space-charge layers following the sudden restoration of zero potential difference between the electrodes. The redistribution of charge carriers and the electrostatic potential both in the steady state and at representative times during the transient response are presented and discussed.
Particle charges and particle-substrate forces by optical transients
Authors: Novotny V.
Published: February 2003

A novel optical technique based on the observation of time-dependent changes in the intensity of light scattered from particles during their motion in a liquid containing contrasting medium is outlined. Principles of the method and theoretical models are presented for sweepout and transit experiments which permit determination of particle sizes, mobilities, charges, particle-substrate interaction forces, and also the removal times of particles from the substrates. Average values and at least the second moments of these quantities are determined. The method was tested on several nonaqueous dispersions with particular attention being paid to titanium dioxide particles in a hydrocarbon fluid. Particle mobilities were measured over a wide range of electric fields and found to increase with field. Particle charges were found roughly proportional to particle size and the average particle-substrate interaction forces were found to be ∼1.4×10−10 N in reasonable agreement with a theoretical estimate of the electrostatic interaction forces. Dynamics of charged particles subject to high-frequency fields was also investigated.
Photoinduced charge-transfer process in PLZT ceramics
Authors: Houlier B. , Micheron F.
Published: February 2003

The photoinduced charge-transfer process in PLZT ceramics is studied by measuring the refractive-index changes during hologram recording at λ=488 nm. From the measured values of the photoinduced space-charge fields, it is concluded that the photocarrier drift lengths are comparable with the fringe spacing (a few μm); the photorefractive sensitivity is limited by the low photoexcitation quantum efficiency (10−4) and is not influenced by oxidoreduction treatments.
Electronic properties of chemically deposited polycrystalline silicon
Authors: Hirose M. , Taniguchi M. , Osaka Y.
Published: February 2003

For the systematic understanding of polycrystalline silicon, the conduction mechanisms, optical absorption processes, and recombination kinetics have been investigated. Tailing states as well as deep levels in the energy gap are found in activation energies of photoconductivity, high densities of ESR centers, and optical absorption tails at photon energies below the energy gap. A new model of electronic density-of-states distribution including the influence of the grain boundary has been constructed for the consistent interpretation of the observed characteristics. A substantial difference between the present model and a Schottky barrier model is also discussed.
Improved weak-field magnetoresistance analysis for (001) -oriented thin films and surface layers with cubic or tetragonal symmetry
Authors: Allgaier Robert S. , Restorff J. B.
Published: February 2003

Weak-field magnetoresistance (WFMR) behavior is described for (001) -oriented films and surface layers in which the sample current lies along a nonspecial direction in the plane. It is shown that four independent WFMR measurements may be made on one sample in this configuration. For cubic crystals, this permits the Seitz-Pearson-Suhl WFMR coefficients b, c, and d to be determined and to be checked for internal consistency. If for any reason, the symmetry of the environment becomes tetragonal (that is, the symmetry axis normal to the film plane becomes distinguishable from the in-plane symmetry axes), then the four coefficients b, b′, c, and d appropriate for this case may be obtained. In either event, the data are more convenient to measure and are more reliable since they are extracted from a single sample. This new approach seems potentially useful as a sensitive indicator of electronic anisotropy over a broad range of environments, including cubically symmetric transport at one extreme and quantized two-dimensional conductivity at the other.
Magnetic flux pinning in proton-irradiated thick Nb samples
Authors: Anjaneyulu Y. , Rollins R. W.
Published: February 2003

Very pure annealed Nb samples having a resistivity ratio, Γ≡ρ296/ρ4.2, in the range 1300–1700 were irradiated with 3–8-MeV protons to fluences of 6.8×1016 and 3.4×1016 protons/cm2. Local magnetic induction profiles, when the samples were in the superconducting mixed state, were obtained using the ac technique of Rollins, Küpfer, and Gey. Electron micrographs of the irradiated samples show that the damage caused by proton irradiation was inthe form of dislocation loops. The volume pinning force Fv, calculated for the dislocation loops using flux pinning models and theories for b=0.7 and T=4.2 K, is compared with the experimentally obtained Fv. The Fv calculated from direct summation law is an order of magnitude higher than the experimental result and the Fv calculated from models, which use Labusch quadratic summation law, is two to three orders of magnitude smaller than the experimental value. Our experimental pinning force per dislocation loop is in agreement with a master curve obtained by Kramer as an empirical solution to the summation problem. Experimentally obtained Fv, for temperatures lying betweeen 2 and 7 K obey a scaling law. If the temperature dependence is written as Fv∝Hnc, then we found n to be slightly dependent on depth x from the sample surface. At x=20 μm, n=3.2±0.2; while at x=84 μm, n=2.7±0.2. The experimental scaling law is compared with the scaling laws obtained from the Labusch model for point pinning centers and Kramer’s model for line pinning centers. Irradiated samples were observed to have a region at the surface with no apparent pinning. This observation is discussed in terms of two different effects: (i) reversible motion of flux lines and (ii) a threshold for flux pinning.
Superconductivity in filamentary CuNb composites produced by powder metallurgy
Authors: Schultz Ludwig , Bormann Rüdiger
Published: February 2003

Composite wires with discontinuous Nb filaments embedded in a Cu matrix are produced by hot extrusion of a powder mixture and subsequent wire drawing. The specimens exhibit superconductivity with critical current densities in zero field up to 4×104 A/cm2 at 4.2 K (after a reduction of the cross-section area of 5×104 by wire drawing). The origin of resistanceless currents in these materials with only 10 wt% Nb is due to superconducting bridges between the filaments which are formed by the proximity effect. The critical currents are drastically enhanced by a final heat treatment, by which additional Nb precipitates are produced in the Cu marix.
The concentration profiles of projectiles and recoiled nitrogen in Si after ion implantation through Si3N4 films
Authors: Hirao T. , Inoue K. , Takayanagi S. , Yaegashi Y.
Published: February 2003

The concentration profiles of ion-implanted boron, phosphorus, and arsenic, and recoil-implanted nitrogen atoms after ion implantation through Si3N4 films on Si have been measured using secondary ion mass spectrometry. The concentration profiles of the implanted ions in Si after ion implantation through Si3N4 films were found to agree with those implanted into bare Si within experimental errors, with the exception of a shifting of the concentration peak position. The concentration profiles of recoil-implanted nitrogen in Si are generally composed of high-concentration regions with steeply decaying distributions near the silicon surface and the exponential tails whose slopes are independent of ion mass, energy, dose, and film thickness. The concentration level of recoil-implanted nitrogen and maximum penetration range relative to the implanted ion range depend strongly on ion mass, film thickness, and ion energy. It was demonstrated that the concentration profiles for recoiled nitrogen in Si calculated using the Thomas-Fermi interaction potential agree better with the measured profiles than those calculated using 1/r2 potential, such as presented in the theory by Moline et al.
Ultrasonic assessment of cumulative internal damage in filled polymers
Authors: Knollman G. C. , Martinson R. H. , Bellin J. L
Published: February 2003

A new ultrasonic technique for studying dewetting and cumulative internal damage in filled polymers such as solid rocket propellants has been developed. The ultrasonic measurements correlate well with volume-dilatation data in tension. Ultrasonic assessment of damage has also been performed for uniaxial compression and shear strain fields. Experimental results show that for a filled polymer a universal relation exists between acoustic measures of damage and the maximum principal strain for fairly general states of strain. A quantitative physical model relating the observed ultrasonic effects to specific damage events is presented. Estimates of the vacuole size and number density, arising from dewetting, obtained by applying this model to experimental data are in excellent agreement with independent microscopic observations. Time-dependent void growth at constant strain has also been monitored by means of the ultrasonic technique.
Photoionization of excited atoms in dc gas discharges by low-intensity light and its analogy to gas-breakdown with high-intensity lasers
Authors: Kopeika N. S. , Eytan G. , Kushelevsky A. P.
Published: February 2003

Spectral effects and nonlinearities that characterize illumination of dc discharges by low-intensity light and illumination of gas cells by high-intensity lasers are described. The similarities suggest an analogy between both cases. This analogy can be used to deepen the understanding of the low-intensity EM radiation interaction with gas discharges and as a possible tool for further study of gas breakdown by high-intensity lasers, including further investigation of the ’’effective photon’’ concept.
Cyclotron resonant gas breakdown with a 1.22-mm 13CH3F laser
Authors: Hacker M. P. , Lax B. , Metz R. N. , Temkin R. J.
Published: February 2003

Cyclotron-resonant laser-induced gas breakdown has been studied for the first time in the transverse geometry, using 1.222-mm 13CH3F laser radiation propagating perpendicular to the magnetic field axis. The line shape of absorbed laser radiation versus magnetic field near electron cyclotron resonance (87.75 kG) indicates a strong dependence of the line shape on the focused laser intensity. This dependence is not predicted by the standard equilibrium theory of high-frequency gas breakdown in a magnetic field. We have developed an analytic theory to explain the observed line shapes. The theory takes into account the laser propagation characteristics, in particular that there is nonuniform ionization due to strong resonant absorption of the laser radiation in a length comparable to or shorter than that of the laser focal volume. The transverse geometry simplifies the theoretical analysis because the observed line shapes are not significantly affected by Doppler broadening. Extensive data have been obtained on the fraction of laser pulse energy absorbed in the gas breakdown volume as a function of magnetic field, helium gas pressure, and incident laser pulse energy. Good quantitative agreement is obtained between the observed laser pulse absorption line shapes and the nonuniform ionization theory.
A model of the streamer-induced spark formation based on neutral dynamics
Authors: Marode E. , Bastien F. , Bakker M.
Published: February 2003

The breakdown of a positive point to plane gap in air near atmospheric pressure begins with the formation of a low-conductivity filament by the space-charge-controlled streamer process. Within the filament, the rate of electron attachment exceeds that of ionization, and the external current decreases. However, a sudden rise of current leading to spark breakdown can be observed. The following explanation is proposed. Owing to the current flow the temperature increases within the discharge. A radial flow of neutral species will thus appear, which decreases the neutral density near the discharge axis. In turn E/N increases until the ionization rate becomes greater than that of attachment, leading to the final current growth.
Electronic cooling of resonant gravity gradiometers
Authors: Forward Robert L.
Published: February 2003

Electronic cooling for improving the signal-to-noise (S/N) performance of sensors was applied to the mechanically resonant Hughes rotating gravity gradiometer (RGG). An 8.3-dB improvement in the S/N was obtained. The electronic cooling technique uses a negative feedback damping circuit between the two RGG transducers. The feedback circuit is electrically equivalent to a high-impedance resistor cooled to cryogenic temperatures.
Introduction of a calibration line for composition determination of a binary alloy by Auger electron spectroscopy (quantitative formalism)
Authors: Tokutaka H. , Nishimori K. , Takashima K.
Published: February 2003

In a complete uniform solid solution of a binary alloy, a theoretical method for constructing a very quantitative calibration line for an AES experiment has been developed. In the method, the following are considered: (i) attenuation of a primary beam, (ii) the effects of backscattered electrons and forwardscattered electrons both from solute and base metals, and (iii) true escape lengths of any electrons. Results of calculations are applied for Ag-Au, Mo-W, and Be-Cu systems.
Resonance Raman studies of annealing in He-, Na-, Cd-implanted cuprous oxide
Authors: Hesse J. F. , Compaan A.
Published: February 2003

The 488.0- and 476.5-nm Ar laser lines have been used to obtain Raman spectra near resonance with the ’’blue’’ and ’’violet’’ excitons in Cu2O implanted with helium, sodium, or cadmium ions. The dose dependence of the Raman spectra was obtained for Cd doses ranging from 1.5×1011 to 1.5×1015 ions/cm2 and was then used for monitoring the repair of implantation-produced damage during anneal treatments. All samples showed a strong anneal stage near 270°C, well below the melting temperature of 1050°C, during which at least 99% of the implantation-produced damage was removed. The Na-implanted sample showed a prominent extrinsic luminescence band near 483 nm after annealing. This first study of annealing in ion-implanted Cu2O demonstrates that resonance Raman scattering is a particularly sensitive probe of damage in semiconductors. The technique exploits the high damage sensitivity of the exciton states with the detailed information on short-range order displayed in the damage dependence of the phonon Raman spectra.
Dimensional variations in Newtonian-quenched metal ribbons formed by melt spinning and melt extraction
Authors: Anthony T. R. , Cline H. E.
Published: February 2003

The wavelengths and directions of dimensional variations in metal ribbons quenched by Newtonian cooling from the melt are estimated for the melt-spinning and the melt-extraction processes. The main sources of dimensional variation are the vibration and distortion of the melt puddle from which the ribbon is solidified and the variation of the Newtonian coefficient of cooling along the ribbon-roller interface. Puddle vibration and distortion can be controlled by using the melt-extraction process or a melt-constrained melt-spinning process. Variation of the Newtonian coefficient of cooling along the ribbon-roller interface can be diminished by operating under vacuum or in a low-atomic-number rare-gas atmosphere and by using a smooth roller that is cleaned during each roller revolution.
Structure transitions in amorphous silicon under laser irradiation
Authors: Bertolotti M. , Vitali G. , Rimini E. , Foti G.
Published: February 2003

An amorphous to a polycrystal or a single-crystal transition by ruby-laser irradiation of amorphous Si, obtained through ion implantation, is discussed. Both free-generation and Q-switched laser mode operation are used. Under a free-generation operation only the amorphous to polycrystal transition is obtained, which is attributed to nonthermal effects. In the Q-switched mode both transitions are obtained. The single-crystal transition is interpreted as due mainly to the melting of the amorphous layer.
The development of a self-contained instant-display erasable electrophoretic x-ray imager
Authors: Swank R. K. , Sears A. R. , Yang K. H.
Published: February 2003

We report the construction and operation of a self-contained electrophoretic x-ray image cell which, between two transparent-electrode coated glass plates, has an electrophoretic liquid in direct contact with radioconductive amorphous selenium. The image cell has a built-in memory which holds the x-ray image after a transitory x-ray exposure. The x-ray image can be developed and erased, without handling the liquid toner or radioconductive material. Potential applications include radiography, mammography, and x-ray inspection of baggages, mail, industrial products, and machines.
Transient field distribution in a multilayer waveguide
Authors: Traganitis A. , Kriezis E. E. , Hagouel P. I.
Published: February 2003

In this paper we consider the field distribution in time and at the origin of the propagation direction of a multilayer lossless dielectric-loaded waveguide. A general expression is given for the distribution due to applied source at the origin. The analytical technique is also presented.
Positive large linear magnetostriction in Fe-Pd crystalline alloys
Authors: Fukamichi K.
Published: February 2003

Conventional magnetostriction materials have some practical disadvantages. In order to develop a new magnetostriction alloy having no such disadvantages, the Fe-Pd alloy system has been investigated. The value of longitudinal linear magnetostriction λ depends sensitively on the heat-treatment conditions. In the cooled state from 900 °C, the concentration dependence of λ at room temperature takes a pronounced maximum at 33% Pd, indicating about 85×10−6 at 500 Oe. Cold working such as swaging has been easily performed.
Growth of polymer films on compound semiconductors and dry etching process
Authors: Aktik M. , Segui Y. , Ai Bui
Published: February 2003

This paper gives some results on the formation of plasma-polymerized polysiloxane films on GaAs substrate in order to improve the dielectric-semiconductor interface properties. Growth rate of polymer films is studied as a function of monomer pressure and time. A dry etching process allowing a good engraving of the polymer film is reported.
Analysis of capacitance-voltage measurements on heat-treated Cu2−xS/CdS heterojunctions
Authors: Hall R. B. , Singh V. P.
Published: February 2003

The capacitance-voltage characteristics of a p-type (metalllike)/n-type semiconductor junction are described in terms of a simple three-region space charge in the semiconductor. The assumed space charge consists of a narrow (∼100 Å) high-density space charge at the interface, followed by an extended low-density space charge (insulating layer), and finally the bulk space charge. The calculations assume that the equilibrium space-charge density does not change with applied reverse voltage. The electric field at the junction is calculated analytically, and the electrostatic potential is calculated for the case of abrupt junctions between the various space-charge regions. The results indicate effective barrier-height lowering as a consequence of interface charges, even in the presence of the insulating layer which dominates capacitance-voltage measurements. An interpretation is given to the slope and voltage-axis intercept of (1/C)2-vs-V plots for a variety of special cases of the general space-charge distribution. Dark-capacitance–voltage data gathered on Cu2−xS/CdS photovoltaic cells are interpreted in terms of the proposed space-charge distribution. The change in junction capacitance with the air-heat treatments of this heterojunction is qualitatively explained by this model.
Properties of niobium superconducting bridges prepared by electron-beam lithography and ion implantation
Authors: Gu Jyongsil , Cha Wongoon , Gamo Kenji , Namba Susumu
Published: February 2003

Niobium superconducting bridges having a variable-thickness geometry consisting of a thin narrow implanted region joining two much thicker bulk films have been fabricated. The temperature dependence of the critical current is described well by the static theory of Likharev and Yakobson. The direct current and alternate current Josephson effects were observed at temperatures above the transition temperature T′c of the bridge. The magnetic field period of the ’’diffraction pattern’’ dependence on magnetic field is analyzed taking into account demagnetizing effects in an approximate way. This field period Hp is found as a function of the bridge width w and the length L for wide bridges (w/L≫1), i.e., Hp= (Φ0/μ0)/ 22/3w5/3L1/3.
Analysis of thermally stimulated currents using activation energy spectra
Authors: Ikeda Susumu , Matsuda Kazuo
Published: February 2003

A method of obtaining activation energy spectra from thermally stimulated currents is described. It is based on Primak’s analysis for the relaxation in a system distributed in activation energy and based on an interpretation of the initial rises of thermally stimulated currents using the distribution of activation energy. The method is applied to the thermally stimulated current of polycarbonate.
Properties of VPE-grown GaN doped with Al and some iron-group metals
Authors: Monemar B. , Lagerstedt O.
Published: February 2003

The influence of doping with Al and some iron-group metals on optical and electrical properties of GaN epitaxially grown from the vapor phase is reported. These impurities are the main inadvertent contaminants in GaN growth, and details on the transport of these elements to the deposition area during growth are discussed. Detailed studies are performed by the SIMS technique on impurity concentration in layers grown under different conditions of contamination. Variations in doping over the area of the grown wafers, as well as with depth into the layer, are investigated, and shown to be significant for Al and N2. These investigations are complemented by SEM cathodoluminescence topographs. Photoluminescence data strongly indicate the existence of a shallow bound exciton (binding energy 12 meV) to isoelectronic Al on Ga sites in GaN. No radiative states are observed from the iron-group contaminants. These (notably Fe and Cr) cause deep states efficient in electrical compensation of the material, which is easily made highly resistive with Fe or Cr.
X-ray sensitivity of selenium
Authors: Donovan John L.
Published: February 2003

The charge-generation energy for commerical selenium xeroradiographic plates has been measured. A new technique based on x-ray-induced photocurrents was used as well as conventional xeroradiographic discharge measurements. Using x-ray spectra typical of medical x-ray irradiations at a conventional applied field of 10 V/μm, a charge-generation energy of 30–40 eV per pair was determined. Theoretical estimates related to the band gap predict a pair-creation energy of 7 eV per pair for selenium.
Copper ion laser: Line broadening studies
Authors: McNeil J. R. , Collins G. J. , DeHoog F. J.
Published: February 2003

We present results of intensity and line broadening investigations of spontaneous emission from atoms excited in a copper hollow-cathode discharge. These measurements indicate a group of electrons exists in the discharge with a density of ≲1014 e−/cm3 and an effective electron temperature of 0.1 to 0.2 eV. The temperatures of atomic species present in the He-Cu discharge have been measured. Finally, the Lorentz width of spontaneous emission from Cu II laser transitions is observed to be a large fraction of the Doppler width and is consistent with the observed homogeneouslike operation of the copper ion laser.
Measurement of Townsend ionization coefficients and the breakdown potentials for the Penning mixtures of Ne and Kr
Authors: Bhattacharya Ashok K.
Published: February 2003

The Townsend primary (α) and secondary (γ) coefficients and Paschen curves for neon, krypton, and their mixtures are reported. The primary coefficient was determined by measuring the variation in the luminous flux in a self-sustained Townsend discharge between two parallel-plate nickel electrodes spaced 21.5 mm apart. The values for the reduced primary coefficient α/p0 for Ne and Kr are about 10–20% lower than the published values obtained by the classical method of Townsend. The α/p0 values for Ne agree with results of previous work using the same luminous-flux method. The ionization efficiency function η (η=α/E, where E is the electric field) for a Ne-Kr gas mixture has a maximum value (0.0040 V−1) for Ne admixed with 0.1% Kr.
Reaction of fluorine atoms with SiO2
Authors: Flamm D. L. , Mogab C. J. , Sklaver E. R.
Published: February 2003

The heterogeneous reaction of F atoms with SiO2 (thermal oxide) has been measured using a discharge-flow tube technique. The reaction probability for F atoms is εF= (1.63±0.15) ×10−2 exp(−0.163 eV/kT) for 250<T<365 K.
Growth of a Gaussian ripple on a uniform-plane wave front in plasmas
Authors: Sodha M. S. , Sharma J. K. , Tewari D. P. , Sharma R. P. , Kaushik S. C.
Published: February 2003

This paper presents an investigation of the growth of a Guassian ripple on a uniform-plane electromagnetic wave front in plasmas. The redistribution of electron density in a plasma because of nonuniform intensity distribution along an electromagnetic wave front gives rise to a nonlinear dependence of the effective dielectric constant on the intensity. The redistribution in collisionless plasmas takes place because of ponderomotive force; this is also true in collisional plasmas for periods less than the energy relaxation time τε. The redistribution in collisional plasmas for periods greater than the energy relaxation time τε is on account of the nonuniform heating of electrons along the wave front. This nonlinearity in the effective dielectric constant makes a ripple of a given radius to self-focus, when the initial power of the ripple (P) is between two critical powers (Pcr1<P<Pcr2). When P≳Pcr2 or P<Pcr1, respectively, oscillatory and monotonic defocusing of the ripple occurs. For powers P lying between Pcr1<P<Pcr2, oscillatory self-focusing of the ripple takes place. The critical power for self-focusing of the ripple and the nature of self-focusing is highly dependent on the power of the main beam, the phase difference between the electric vector of the ripple and main beam, and the absorption. The analysis is also valid for a weakly inhomogeneous plasma within the WKB approximation.
Deposition of crystals from the plasmas of ZrO2, HfO2, ThO2, and CeO2
Authors: Kawabuchi Katsuhiro , Magari Saburo
Published: February 2003

Deposition occurs onto a cathode from an oxide plasma generated inside a hollow oxide anode by the mechanism called the electrolysis of plasma. The temperature of the cathode is usually over 2000 °C during deposition. Deposits attain fairly large crystalline sizes (about 0.3 mm) in spite of their high deposition rates. And besides, some unusual crystals are formed. For the deposition from ZrO2, HfO2, and ThO2 plasmas, the deposition rate, growth rate, and the current efficiency increase with the plasma current (0.4–8 A) and with feeding O2 gas into the plasmas. On the other hand, heating a cathode externally or feeding Ar gas into them leads to the reduction of those rates, the current efficiency, and yield. The maximum growth rate from the ThO2 plasma is 8.4 μm/sec. Yields exceed 90% in general. Mass-spectrometric analyses showed that the main depositing ion species is ZrO+ for the deposition from the ZrO2 plasma. Deposits obtained are usually black oxides, whose O/M (M=Zr, Hf, and Th) ratios are 1.95, 1.95, and 1.64, respectively. The deposits from ZrO2, HfO2, and ThO2 plasmas are monoclinic ZrO2 with precipitates of metallic α-Zr, monoclinic HfO2 with a small amount of unknown hexagonal crystals (whose lattice parameters are a=3.17 and c=5.02 Å), and a mixture of fcc ThO2 and Th, respectively. When O2 gas is fed into those plasmas, transparent oxide crystals of stoichiometric composition are formed. The deposits from a CeO2 plasma are the black oxides whose O/Ce ratios are 1.53 on the average. Contrary to the phase diagram of the Ce-O system, they show x-ray structures of fcc crystals whose lattice parameter varies from 5.506 to 5.411 Å.
Piezoelectric potentials of dislocations in insulating crystals
Authors: Hutson A. R. , Walker L. R.
Published: February 2003

The electric potential produced by the strain field surrounding a dislocation in a piezoelectric crystal was calculated by the ’’exact’’ plane-strain method. The results are in close agreement with those of the earliest approximate calculation. A major discrepancy between previous calculations has been traced to a sign error in the exact formulation. The most recent approximate calculation is shown to be incorrect in principle.
EPR determination of the concentration of chromium charge states in semi-insulating GaAs : Cr
Authors: Stauss G. H. , Krebs J. J. , Lee S. H. , Swiggard E. M.
Published: February 2003

Chromium can assume three different charge states in semi-insulating GaAs :Cr. An EPR-optical method is described which allows the Cr concentration in each of these states to be quantitatively determined. Typical results are given for a number of Cr-doped GaAs samples.
An x-ray diffraction study on the microstructure of vapor-deposited fcc lead films: normal and oblique incidences
Authors: Nandi R. K. , Sen Gupta S. P.
Published: February 2003

Detailed x-ray diffraction investigations, based on precise measurements of the position, asymmetry, broadening, and shape of x-ray diffraction profiles 111, 200, 220, 311, 222, and 400 recorded in a counter diffractometer, have been performed on vacuum-evaporated fcc lead films in the range of thickness ∼300–6500 Å. The films are deposited on glass substrates at a residual air pressure ∼5×10−5 Torr for both normal and oblique vapor directions. The complete analyses have revealed clearly the microstructural features in these vapor-deposited films. Near-isotropy in the domain size and rms strain values with a relatively less size effect has been observed. The magnitudes of the respective compound fault parameters, close to the error limits, indicate the total absence of intrinsic (α′), extrinsic (α″), and even growth twin (β) stacking faults in the films. The dislocation density (ρ) is typical for thin films and is ∼1011 cm/cm3. The residual internal stresses (σ), compressive in nature, are small, and the small lattice parameter changes show a contraction in the plane of the film. The films are found to be highly oriented along [111] irrespective of the source position. It has been observed that the microstructural parameters exhibit more or less a regular variation with film thickness and are less influenced by the source position.
Ferrobielastic hysteresis in α-quartz
Authors: Bertagnolli Emmerich , Kittinger Erwin , Tichý Jan
Published: February 2003

The ferrobielastic behavior of α-quartz crystals under compressive stress has been investigated making use of the piezoelectric and piezo-optic effects. The direction of mechanical stress was so chosen that secondary twinning is favored. Above a threshold of approximately 0.5 GPa, ferrobielastic switching results in a complete orientation reversal. Unexpectedly the mere removal of the mechanical constraint leads to a complete restoration of the original orientation. This retrotransition occurs between 0.1 and 0.025 GPa. This effect is discussed in terms of a simple thermodynamical model.
The sulfur-related trap in GaAs1−xPx
Authors: Craven R. A. , Finn D.
Published: February 2003

A systematic study has been made of the deep level introduced into GaAs1−xPx alloy material by S doping. Conclusive documentation of the linear relationship between S concentration and the deep-level trap concentration is presented for x?0.4. The dynamic properties of this trap measured at x=0.38 show a temperature activation energy for emission and electron capture of 0.35 and 0.15±0.03 eV, respectively. It exhibits a very large hole-capture cross section at a site occupied by an electron. A very sharp drop in the ability to populate the trap below x=0.35 is consistent with the trap being energetically tied to the X band minimum and having a depth of 0.17 eV below this band minimum. The dependence of the thermal-emission activation energy on alloy composition is ascribed to the necessity to capture electrons from the indirect minima below x?0.4. Photoionization experiments indicate that a much greater photoenergy than the thermal energy is required to ionize an electron trapped at this site (1.1 compared to 0.17 eV). Electron capture followed by a large lattice relaxation is consistent with the data and the phenomenon of persistent photoconductivity at low temperature associated with the S center. The S center in GaAs1−xPx provides an efficient nonradiative recombination path for minority carriers.
Piezoelectricity in β-phase poly(vinylidene fluoride) having a ’’single-crystal’’ orientation
Authors: Wang T. T.
Published: February 2003

β-phase PVF2 films having a ’’single-crystal’’ orientation (single-crystal analog) were prepared by a combination of drawing, rolling, and annealing, applied in sequence. X-ray diffraction patterns revealed that the polar b axis was preferentially oriented normal to the surface of the film while the a and c axes were in the plane of the film, lying along two mutually orthogonal axes. Piezoelectric outputs (d13) of the films were compared with those of drawn-only films under the same poling conditions (about 500 kV/cm) and found to be on average about 25% higher than the latter. X-ray and dynamic mechanical data showed that the improvement depends primarily on the preferred alignment of the a and b axes in the plane normal to the draw and rolling direction.
Piezoelectric activity and field-induced crystal structure transitions in poled poly(vinylidene fluoride) films
Authors: Newman B. A. , Yoon C. H. , Pae K. D. , Scheinbeim J. I.
Published: February 2003

Unoriented and biaxially oriented phase-II poly(vinylidene fluoride) films were poled at very high fields up to 4.0×106 V/cm at room temperature. Changes in molecular orientation and crystal structure induced by the high-field poling were studied using x-ray and DSC methods. The piezoelectric coefficients d31 and e31 together with the dielectric response (ε′ and ε″) were determined using a Piezotron Model U (Toyo Seiki, Tokyo) for the poled films. The piezoelectric activity did not increase steadily with poling field, but showed four distinct regions depending on poling field. At low fields (Ep<106 V/cm), when x-ray and DSC data indicated that the films were predominantly in the phase-II structure, the piezoelectric activity was small (e31<2×10−3 C/m2). For poling fields between 1×106 and 2×106 V/cm the piezoelectric activity was observed to rise rapidly with poling field until a value of e31∼14.5 C/m2 was observed. In this region the x-ray scans indicated that phase-II crystallites were being transformed to a polar phase. At poling fields from 2 ×106 to 3.2×106 V/cm a plateau region was observed with very little change in the value of the piezoelectric coefficient. X-ray and DSC data showed that very little change in the structure and molecular orientation occurred in this region. At the very highest poling field applied (4×106 V/cm) the piezoelectric data indicated the commencement of a very rapid increase in piezoelectric activity (e31∼19.5×10−3 C/m2). At this poling field the x-ray and DSC data indicated that a crystal transformation to phase I had occurred. The piezoelectric coefficients of the unoriented films was not measured. X-ray diffraction data indicated that, in addition to the structural and orientation changes occurring in the biaxially oriented film, an x-ray reflection, which could not be indexed using phase I, II, or III unit cells, increased in intensity with poling field. The DSC data showed the appearance of a new endothermic peak which also increased with poling field. These data indicated that molecular chains oriented perpendicular to the plane of the films transformed to some new structure under the action of the high applied fields.
Efficient ion beam extraction from a flowing plasma
Authors: Dembinski M. , John P. K.
Published: February 2003

A moving plasma with directed flow velocities v larger than the ion acoustic speed cs is used as a source of high-current ion beams in the 10–20-keV range of energies. Current densities up to 3 A/cm2 are obtained at the plasma boundary which is an order of magnitude larger than the limiting value of Bohm current in a stationary plasma. The observed current densities were proportional to v, unlike the Bohm current densities which are proportional to ion acoustic speed. Total ion currents up to ∼100 A were extracted from the plasma through a two electrode extraction system. Simple geometric shaping of the electrodes enabled an 8-cm-diam beam to be focused to ∼7 mm.
Laser-induced phosphorescence-excitation spectra of various vibrational bands of the SO2  (3B1) -SO2  (X, 1A1) transition
Authors: Wampler F. B. , Oldenborg R. C. , Rice W. W.
Published: February 2003

A N2-pumped tunable dye laser has been used to obtain the phosphorescence-excitation spectra at 1.00 Torr and room temperature of the 000-000, 010-000, 020-000, 100-000, and 110-000 vibrational bands of the 3B1→1A1 transition of sulfur dioxide. These spectra support earlier absorption studies regarding perturbations of the 3B1 state. The results of perturbations in the 110-000 band from K′=15 upwards are especially pronounced in the emission studies presented here.
Energy exchange between free electrons and light in vacuum
Authors: Edighoffer J. A. , Pantell R. H.
Published: February 2003

Momentum is exchanged between free electrons and light when the interaction length is limited. An analysis and a computer simulation determine the characteristics of this energy transfer. Possible experimental schemes at optical and infrared wavelengths are explored.
Striations in high-current annular electron beams
Authors: Kutty A. P. G.
Published: February 2003

The electron density distribution in electron beams produced in high-current field-emission diodes often shows striations in the form of periodic maxima and minima. The nature of the striations depends on the shape of the cathode. A theory of these striations applicable to cylindrical cathodes is given. The current is taken to be flowing through the cathode flare plasma formed in the diode during the course of beam emission and the stability of such a current-carrying plasma is studied. For certain wavelengths of perturbation, the perturbation grows exponentially and leads to an instability which manifests itself as striations in the current distribution. The unstable wavelengths are related to the characteristic dimensions of the cathode.
Electro-optic multimode waveguide modulator or switch
Authors: Campbell J. C. , Li Tingye
Published: February 2003

Details of an investigation of a new type of electro-optic multimode waveguide modulator or switch are reported. The device makes use of the concept of imaging in a multimode waveguide. Simultaneous switching of a few low-order modes is obtained electro-optically by nonuniform modulation of the refractive-index profile of the active waveguide section. Small fabrication tolerances can be compensated for by electrical means and the device can be realized in various sizes and configurations for easy and efficient coupling to lasers, fibers, and other components. Modulation, switching, and power division have been demonstrated in waveguide devices of various widths and lengths fabricated on Ti-diffused LiNbO3. Coupling losses as low as 0.5 dB have been observed and extinction ratios of 13–20 dB with 20–80 V drive have been obtained.
A high-gain CO chemical laser
Authors: Wakabayashi Satoshi , Arai Tsunenori , Fujioka Tomoo
Published: February 2003

The operation of a new type CO chemical laser has been demonstrated in which a chain reaction is initiated by ac discharge through O2 discharge tubes and the laser cavity. The chain reaction with CS/O2 as the fuel/oxidizer,and O and S atoms as the chain carriers, is thought to be the basis of the operation. Gain and power measurements have been made and small-signal gains of 1.1%/cm for both P8(18) and P6(17) have been observed 7.5 mm downstream from the CS2 transverse injectors. Laser oscillation has been observed directly below the CS2 transverse injectors.
Laser system for boring and sampling in coated-particle fuel
Authors: Allelein H. J. , Hecker R. , Max A. , Overhoff Th. , Stöver D.
Published: February 2003

A pulsed four-level solid-state laser (Nd3+ : yttrium-aluminum-garnet) was developed to determine concentration profiles of the fission product cesium in multilayered spherical coated-particle fuel. In addition, the system can be used for the simulation of cracked coatings by radial borings. The laser system with a Fabry-Perot-type resonator fulfills the requirements of small pulse width, absence of higher modes, and consistency of pulse energy. Control and timing is maintained with a ’’Q switch’’ and a ’’Brewster polarisator’’. Single-bore holes are ? 10 μm in diameter, and hole depths range up to 200 μm. The evaporated radioactive material is sampled with an efficiency ≳ 95% on a glass plate which is used for γ and β counting. The formation of ’’deep’’ holes is theoretically explained by a self-channeling mechanism and briefly discussed. Techniques used for radial-distribution measurements for the fission product 137Cs in different irradiated coated particles are presented. Radially bored particles simulating cracked coatings are heat treated and fractional releases are measured.
Dynamic properties of semiconductor lasers
Authors: Ito Minoru , Ito Takeshi , Kimura Tatsuya
Published: February 2003

The dependence of relaxation oscillation on carrier diffusion length in AlGaAs lasers is analyzed using multimode rate equations containing carrier diffusion and spontaneous emission terms. A parameter representing coupling between carrier and light field distribution is introduced. The carrier diffusion shortens the delay time, the relaxation oscillation period, and the decay time constant and also makes spectral narrowing faster. The damping factor is enlarged and relaxation oscillation is suppressed as the carrier diffusion length becomes large. The diffusion length, normalized by stripe width LD/W, is estimated to be about 0.6 by comparing the numerical results with the experimental tendency of transient response. Furthermore, relaxation oscillation is suppressed as the oscillation beam spot size becomes smaller.
Effect of hole injection on γ-ray-induced conduction in polystyrene and poly-monochloro-p
a
r
a-xylylene
Authors: Maeda H. , Kurashige M. , Nakakita T.
Published: February 2003

The γ-ray-induced conduction of polystyrene and poly-monochloro-para-xylylene at high electric fields exhibits a slowly increasing component whose magnitude depends upon the nature of the metal used for the anode, but not that used for the cathode. This phenomenon is interpreted as hole-injection current, enhanced by the accumulation of negative space charges during the irradiation.
Infrared spectra of new acceptor levels in boron-doped and gallium-doped silicon
Authors: Scott Walter , Jones Colin E.
Published: February 2003

Infrared-absorption measurements have shown the existence of shallower acceptor levels associated with both boron and gallium in silicon. The new spectra correspond to effective-mass-like acceptors with optical ionization energies of 37.1±0.3 meV in boron-doped silicon and 57.0±0.3 meV in gallium-doped silicon. Similar centers have been previously identified in indium- and aluminum-doped silicon so the defect structure involved seems to be common to the group-IIIA acceptors in silicon. The presence of this defect explains some of the early discrepancies between the thermally and optically measured activation energies for boron and gallium in silicon.
Recoil implantation and ion-beam-induced composition changes in alloys and compounds
Authors: Sigmund Peter
Published: February 2003

Recoil implantation of an homogeneous alloy results in distinctly different composition changes after low- and high-fluence ion bombardment. An enrichment is found near the surface in the heavier component at low fluence and in the lighter component at high fluence. In the absence of preferential sputtering, recoil implantation leads to a sputtered flux that is enriched in the heavier component. The estimated net transport of matter by recoil implantation is shown to be consistent with recent experimental observations.
AlGaAs tunnel diode
Authors: Bedair S. M.
Published: February 2003

An AlGaAs tunnel diode with a band gap of 1.6 eV has been fabricated. This diode provides a suitable connecting junction between the high- and low-band gap cells of a cascade solar-cell structure operating at several hundred suns concentration without causing any appreciable loss in efficiency.