bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray yields of plasmas heated by 8-nsec neodymium laser pulses
Authors: Glibert K. M. , Anthes J. P. , Gusinow M. A. , Palmer M. A. , Whitlock R. R. , Nagel D. J.
Published: February 2003

36 elemental targets, beryllium through uranium, were irradiated with 8-nsec FWHM Nd : glass laser pulses focused to ∼4×1013 W/cm2. X-ray spectra were recorded with a convex-crystal spectrograph and with a 22-channel PIN-diode spectrometer. Line and continuum spectra indicated temperatures of 36589 eV. Total x-ray irradiances in the energy range 0.7–20 keV showed strong peaking as a function of atomic number with a maximum conversion efficiency of 9.6% relative to the incident laser energy. An indication of enhanced N-shell x-ray emission near U is reported here for the first time.
Comment on ’’Anisotropy study of electrical conduction in oriented polymers. I. Analysis of bulk electrical conduction parallel to the surface of film’’
Authors: Wintle H. J. , Chapman T. C.
Published: February 2003

We examine the field pattern produced by the four-electrode system attached symmetrically to both sides of a film which was investigated by Hirota. We provide a conformal transformation which ensures that an electric field line is coincident with the film surface. The conductivity in the film is calculated and compared with experimental results.
Threshold switching in chalcogenide-glass thin films
Authors: Adler D. , Shur M. S. , Silver M. , Ovshinsky S. R.
Published: February 2003

We discuss bias-induced threshold switching in chalcogenide-glass thin films, with an emphasis on the unique aspects of this phenomenon. The electronic nature of both the ON state and the recovery process is now clear. In this paper, we also establish the fundamentally electronic origin of the initiation process. An isothermal model is presented and analyzed for filamentary ON-state solutions via a set of phenomenological kinetic equations consistent with recent advances in our understanding of the electronic structure of chalcogenide glasses. The predictions of this model compare favorably with a variety of experimental results. The model is basically that the switching transition develops when a critical electric field is reached somewhere in the sample, usually near an electrode. Field-induced carrier generation then causes the charged traps in the bulk to fill (neutralize). When all the traps are filled, carriers can transit the sample with an enhanced mobility and the generation rate required to keep the traps filled is reduced from its threshold value.
Electron density distributions in gas discharge columns with electron production and loss rates linear and quadratic in electron density
Authors: Rogoff Gerald L.
Published: February 2003

Previously, a simple yet exact characteristic equation was derived for steady-state longitudinally uniform positive columns in which the electron density ne is given by the continuity equation D∇2ne+νne +kn2e =0 with the coefficients independent of position and with ne =0 at the boundaries, which can be of arbitrary cross-sectional shape. The effective coefficients ν and k may be positive or negative and can each represent the net effect of various electron production and loss processes. The general characteristic equation contains a dimensionless quantity S (the integral of −∇2ne/ne over the cross section) which provides information about the shape of the electron density distribution. The S integral has been evaluated numerically for circular and rectangular column cross sections. For the case of a circular cross section the variation of the density profile and S have been determined for all possible relative magnitudes and combinations of signs of ν and k. The results provide a generalized parameter map which indicates steady-state operating conditions for a large class of discharge columns. S varies from large positive values for diffuse columns (for k<0, i.e., with electron loss by volume recombination) to large negative values for constricted columns (for ν<0, i.e., with loss by attachment). For ν<0, the results indicate that no steady-state distributions exist with attachment-dominated loss at the location of maximum ne.
Doping of semi-insulating and n-type GaAs by neutron transmutation
Authors: Mueller J.-E. , Kellner W. , Kniepkamp H. , Haas E. W. , Fischer G.
Published: February 2003

By bombarding GaAs wafers with thermal neutrons it has been possible to introduce a specific constant donor concentration. The radiation damage caused by bombardment can be annealed at temperatures below 800 °C. A room temperature electron mobility of 3900 cm2/Vs has been achieved at an impurity concentration of 5×1017 cm−3. The doping of n−-type layers shows, in addition to the expected doping effect, that the n−-type layer is compensated near the semi-insulating substrate.
Shallow junctions by high-dose As implants in Si: experiments and modeling
Authors: Tsai M. Y. , Morehead F. F. , Baglin J. E. E. , Michel A. E.
Published: February 2003

Shallow (<0.2 μm) n+ layers in Si with high conductivity (<40 Ω/⧠) have been formed by high-dose (2×1016 cm−2) As implants. Experimental observations of As distributions and carrier concentrations are successfully simulated by a computer program which accounts for both the concentration dependent diffusion and As clustering effects. Reduction of electrical carriers in high-dose As implanted Si during moderate temperature (∼800 ° C) heat treatments is readily explained by the kinetics of As clustering. Physical limitations on the conductivity which can be achieved by thermally annealed As implants in Si are also discussed.
Traveling wave excitation of the nitrogen ion laser
Authors: Collins C. B. , Carroll J. M.
Published: February 2003

A repetitively pulsed, traveling-wave laser has been operated with a front-to-back ratio exceeding 1000 : 1 when producing peak powers in excess of 3 MW.
Experiments on cylindrically converging blast waves in atmospheric air
Authors: Matsuo Hideo , Nakamura Yuichi
Published: February 2003

Cylindrically converging blast waves have been produced in normal atmospheric conditions by the detonation of the explosives, pentaerythritoltetranitrate, (PETN), over cylindrical surfaces. The shocks generated in this way are so strong that the fronts propagating through the air become luminous of themselves. The production and the propagation of the shocks have been monitored with a framing camera and a streak camera, and the time-space relations of the shock propagations have been determined using an electrical ionization probing system. The results have shown that the trajectory of the shock fronts near the axis of the cylinder can be approximately represented by the Guderley’s formula.
Practical application of the thermal pulsing technique to the study of electrets
Authors: Collins R. E.
Published: February 2003

The thermal pulsing technique gives information about the spatial distribution of charge and polarization through the thickness of electrets. This paper discusses methods by which this technique is applied in practice to the problem of determining these distributions. Several possible sources of systematic error in the experimental data are identified, and methods are discussed for eliminating these errors. A physical approach to data analysis is discussed which is complementary to a previously published mathematical analysis. Examples are given where this approach has yielded useful information about the charge or polarization distribution in insulators.
The nonlinear theory of efficiency enhancement in the electron cyclotron maser (gyrotron)
Authors: Sprangle P. , Smith Robert A.
Published: February 2003

We present a nonlinear analysis of the single-particle dynamics in an electron cyclotron maser oscillator and show that the efficiency can be dramatically enhanced by appropriately contouring the system parameters. The beam electrons can be prebunched in phase to form a macroparticle in phase space such that beam kinetic energy is not extracted. After forming a phase-bunched electron beam, either the applied magnetic field or the cavity electromagnetic field can be spatially varied in such a way as to extract virtually all the electron transverse kinetic energy. Without such contouring, the transverse efficiency is typically ?40%. An example is presented in which the transverse efficiency is increased from 36% (in uniform fields) to 75% by increasing the applied magnetic field by ∼6%. The present analysis can readily be extended to the case of a maser amplifier.
Optical extraction characteristics of homogeneously broadened cw lasers with nonsaturating lasers
Authors: Eimerl D.
Published: February 2003

The optical extraction characteristics of homogeneously broadened cw lasers with nonsaturating losses are calculated exactly and compared with previous analytic approximations. The extraction efficiency as a function of the output coupling is discussed in detail for medium parameters appropriate to high-gain rare-gas-halide lasers. It is found that contrary to expectations, the output is comparatively insensitive to the medium parameters and output coupling, and that it is a poor diagnostic tool for laser medium characterization.
Attenuated total reflectance study of silicon-rich silicon dioxide films
Authors: Hartstein A. , DiMaria D. J. , Dong D. W. , Kucza J. A.
Published: February 2003

The infrared absorption of Si-rich SiO2 films has been measured using the attenuated total reflection technique. Absorption lines attributed to SiOH, H2O, and SiH groups have been observed in the as-deposited films. The concentrations of the SiOH and H2O impurities were found to be in the low 1021 cm−3 range, and the concentration of the SiH impurity was found to be 1018 cm−3. Following a 1000 C anneal 1019 cm−3 and 1016 cm−3 ranges, respectively.
Electronic properties of selenium-doped silicon
Authors: Grimmeiss H. G. , Janzén E. , Skarstam B.
Published: February 2003

Two dominant selenium-related defects in silicon have been studied by transient capacitance and current techniques. For one of the centers, the A center, Arrhenius plots of thermal emission rates for electrons and holes (log et−1/T) give ’’thermal activation energies’’ of EC −ET =0.52 eV and ET −EV =0.62 eV, respectively. Although the electron-capture cross section of the center is too large to be measured with our equipment, a conservative estimate gives a value larger than 10−14 cm2. The electron-capture cross section σtnB of the other center, the B center, showed a T−3.2 temperature dependence and has a value of 3×10−15 cm2 at 100 K. From the measured data for σtnB and etnB a value of 0.30 eV for the Gibbs free energy of the B center is obtained. This energy value is constant and equal to the enthalpy in the temperature range investigated. Plotting log T2σtnB versus 1/T, an activation energy of 14 meV is obtained. This is interpreted as the energy separation between the lowest state accessible in a cascade capture process and the conduction band. In all samples, the concentrations of the A and B centers are found to be equal.
Plasma polymerized methyl-methacrylate as an electron-beam resist
Authors: Morita Shinzo , Tamano Junji , Hattori Shuzo , Ieda Masayuki
Published: February 2003

Plasma polymerized methyl-methacrylate thin film was formed on a glass substrate coated with chromium as a resist for electron-beam lithography. The polymerizations were conducted at two discharge frequencies of 13.56 MHz and 5 KHz using a capacitively coupled discharge electrode system in a bell-jar-type reactor. Delineations were carried out using an electron beam whose diameter and acceleration voltage were 0.5 μm and 20 kV, respectively. As a test pattern, 25 pairs of parallel lines and spaces each having a 10-μm width were delineated in a rectangular area of 0.5×0.5 mm2. Each line of 10-μm width was depicted by sweeping over using the electron beam with 20 repetitions. The patterns were developed on the chromium by CCl4 plasma etching.
Lifetime comparisons between 8- and 12-μm-wide stripe-geometry proton-bombarded double heterostructure (Al,Ga)As lasers
Authors: Hartman R. L. , Dixon R. W.
Published: February 2003

The 70 °C dry nitrogen ambient, continuously operating, lasing lifetimes of 8- and 12-μm stripe width proton-bombardment-delineated double heterostructure (Al,Ga)As lasers are compared. The different stripe-width lasers are found not to exhibit significant lifetime differences for (slice dependent) median lifetimes less than about 1000 h at 70 °C. However, for median lifetimes greater than this the wider stripe lasers are statistically longer lived. In companion experiments the lasing lifetimes of devices with deep and shallow proton bombardment (protons penetrating, and not penetrating the active volume) have been found to be similar, with the possible exception of very long-lived devices. In the latter case shallow bombarded devices may be superior. More experiments will be required to establish a causal relationship, if it exists, between proton damage in or near the active volume and laser lifetime.
Influence of oxygen on silicon resistivity
Authors: Cazcarra V. , Zunino P.
Published: February 2003

The influence of oxygen on the resistivity of dislocation-free silicon wafers was studied after annealing at various temperatures under a nitrogen ambient. Significant resistivity shifts were observed in the temperature range 600–900 °C and related to oxygen precipitation. This phenomenon is independent of the well-known donor generation observed around 450 °C and is more difficult to cure.
Deep sulfur-related centers in silicon
Authors: Grimmeiss H. G. , Janzén E. , Skarstam B.
Published: February 2003

The electronic properties of two dominant sulfur-related deep donor levels in silicon have been investigated using capacitance and dark current transient techniques. One of the centers, the B center, has an enthalpy ΔHn of 0.32 eV and an electron-capture cross section σtnB of 2×10−15 cm2 at 100 K. σtnB varies with temperature as T−3.3. A plot of log etnA vs 1/T for the other center, the A center, shows a ’’thermal activation energy’’ of 0.59 eV. σtnA is estimated to be larger than 10−14 cm2. The nature of the A and B centers is discussed.
Magnetostatic spinwave modes of a ferromagnetic double layer
Authors: Grünberg P.
Published: February 2003

The theory for the spinwave modes of a ferromagnetic single layer by Damon and Eshbach [J. Phys. Chem. Solids 19, 308 (1961)] has been extended to double layer systems. A restriction is made with respect to inplane magnetization and transverse propagation of the spinwaves. For this situation a formula is derived which predicts two surfaces modes for large film separation and one volume and one surface mode when the films are combined to a single one.
Oblique incidence reflection acoustic imaging
Authors: Yeack C. E. , Chodorow M.
Published: February 2003

The authors report here recent advances in reflection acoustic microscopy using an obliquely incident focused acoustic beam. Results show that, in addition to exaggerated surface contouring on objects such as integrated circuits and blood cells, a contrast enhancement is observed which facilitates the study of thin-film polymers such as MylarX (Dupont). A theoretical explanation is presented which describes these results and provides a means of predicting which objects are best studied in the normal incidence and oblique incidence reflection acoustic microscopes.
Temperature dependence of the lasing threshold current of double heterostructure injection lasers due to drift current loss
Authors: Anthony P. J. , Schumaker N. E.
Published: February 2003

Contact-limited, ambipolar transport, which describes the drift current behavior of minority carriers not confined to the active layer of double heterostructure injection lasers, is used to predict different behavior than previous calculations for the temperature dependence of the threshold current for lasing. The high-temperature coefficients of some lasers may more easily be explained using the model.
Towards a high-temperature solar electric converter
Authors: Dunning G. J. , Palmer A. J.
Published: February 2003

The results of an experimental and theoretical study aimed at developing a novel high-temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high-temperature collector of solar radiation as well as the working fluid for a high-temperature working cycle. The envisioned working cycle is a simple magnetohydrodynamic Rankine cycle. The motivation for developing this type of solar electric converter is based primarily on the cost and weight reduction premiums for operating a space solar electric generator at the maximum possible temperature. We report on the construction of a theoretical model for coupling sunlight into a cesium plasma and on the experimental demonstration of cesium heating with a solar simulator that is in good agreement with the theory.
Generalized diffusion, mobility, and the velocity autocorrelation function for high-field transport in semiconductors
Authors: Ferry D. K. , Barker J. R.
Published: February 2003

A general study of the velocity autocorrelation function for high electric field transport in Si is presented. Calculations have been carried out using a Monte Carlo technique for calculating the transport parameters. Additionally, a generalized model for defining diffusion and mobility in terms of a transport equation is presented. A detailed Shockley model is used to evaluate these equations for the velocity autocorrelation function. It is found that f′(t) initially relaxes exponentially, due to momentum relaxation, goes negative and displays a local minimum, then relaxes to zero at a slower rate due to energy relaxation.
Comment on ’’Capacitance-voltage measurements in amorphous Schottky barriers’’
Authors: Powell M. J. , Döhler G. H.
Published: February 2003

The band-bending potential profile V(x) in the space-charge region of an amorphous semiconductor moves regidly in the x direction, with increased bias, irrespective of the form of the density of localized states N(E). A recent paper by Singh and Cohen [J. Appl. Phys. 51, 413 (1980)] which suggest this is not true is incorrect in this point. This property leads to simplified schemes for the analysis of C-V measurements and field-effect conductance measurements.
Metastable As-concentrations in Si achieved by ion implantation and rapid thermal annealing
Authors: Lietoila A. , Gold R. B. , Gibbons J. F. , Sigmon T. W. , Scovell P. D. , Young J. M.
Published: February 2003

Rapid thermal annealing (4 min at 560 °C) of implanted As in Si can electrically activate concentrations up to 5×1020 cm−3, which exceeds the solubility at that temperature. Prolonged thermal annealing at the same temperature causes deactivation of such metastable concentrations. The results suggest that when the amorphous-crystalline interface is moving during solid phase epitaxial regrowth, dopants go to substitutional sites even in concentrations exceeding solubility. If solubility is exceeded, deactivation takes place after the material has recrystallized.
Directionally solidified thin-film eutectic alloys
Authors: Cline Harvey E.
Published: February 2003

A natural, submicron-size periodic structure was fabricated by directional solidification of Pb-Sn eutectic thin films. Eutectic alloy films between 1 and 8 μm thick were deposited on glass and directionally solidified at rates between 0.5 and 12.6 mm/min that yielded fault-free lamellar structures. A mechanism that involves the propagation of bent plates was observed to adjust the spacing without forming faults. Below a critical thickness comparable to the periodic spacing, the structure was observed to become irregular. The spacing control and stability of the lamellar eutectic thin films are discussed.
Conductivity and p-n type control of fluorinated amorphous silicon (a-Si:F) without incorporating hydrogen
Authors: Matsumura Hideki , Nakagome Yoshinobu , Furukawa Seijiro
Published: February 2003

A fluorinated amorphous-silicon alloy (a-Si:F) is produced by the radio frequency sputtering of silicon in mixtures of Ar and SiF4 gases. Fluorine content, infrared absorption, and temperature dependence of dark conductivity are measured and the results are interpreted in terms of the reduction of dangling bonds due to the incorporation of fluorine. n- and p-type doping of this a-Si:F is achieved by the addition of BF3 and PF5 in the sputtering gas, without incorporating hydrogen at all.
High-impedance ion-diode experiment on the Aurora pulser
Authors: Meger R. A. , Young F. C. , Drobot A. T. , Cooperstein G. , Goldstein Shyke A. , Mosher D. , Graybill S. E. , Huttlin G. A. , Kerris K. G. , Stewart A. G.
Published: February 2003

Proton beams with currents ⩾50 kA at 5 MeV in a ≲160-ns FWHM pulse have been extracted from an ion diode operated on the Aurora pulser. This current corresponds to an efficiency (proton currrent/total current) of 20%, which compares favorably with numerical simulation. The simulation indicates that the ion current is enhanced over the Child-Langmuir value due to increased electron lifetime in the diode. The proton beam directed onto a LiCl target provides a source of 1.8×1012 neutrons/sr/pulse in the forward direction from the 7Li(p,n) 7Be reaction.
Effects of avalanche injection of electrons into silicon dioxide—generation of fast and slow interface states
Authors: Lai S. K. , Young D. R.
Published: February 2003

In the process of avalanche injection of electrons into silicon dioxide, besides electron trapping in the bulk of the oxide, there are slow and fast interface states generated. The slow states are donors and positively charged when empty. Together with positive charge in the interface states, they compensate the negative bulk charge to give the turn-around effect. The final C-V curve is due to a complex sum of different charge components. The slow states can be discharged when heated under +5 V or higher biases at 160 °C or above. The final charge state is only semipermanent. Fast interface states are also annealed in the process, and the anneal is enhanced by a positive bias. Bulk trapped electrons are minimally perturbed by the anneal. It is postulated that the slow states may communicate with silicon through the fast interface states in a thermally activated process. In order to study bulk electron trapping, avalanche injection should be carried out at elevated temperatures.
Electron mobility and minority-carrier lifetime of n-InP single crystals grown by liquid-encapsulated Czochralski method
Authors: Yamaguchi Masafumi , Shinoyama Seiji , Uemura Chikao
Published: February 2003

Correlations between electron mobility, minority-carrier lifetime, impurity concentration, and dislocation density have been studied in LEC (liquid-encapsulated Czochralski)-grown InP single crystals. Mobilities approaching 30 000 cm2/V s at 77 K, which correspond to compensation ratios of 0.2–0.4, have been obtained. Hole lifetimes as high as 3 μs have been obtained in dislocation-free single crystals. The experimental results for lifetimes can be explained by a simple model in which dislocation and impurity are considered as recombination centers.
Dark-field study of rear-side density structure in laser-accelerated foils
Authors: Stamper J. A. , Gold S. H. , Obenschain S. P. , McLean E. A. , Sica L.
Published: February 2003

A dark-field, laser-probing diagnostic has produced the first high-resolution photographs of density structure on the rear side of laser-accelerated foils. This diagnostic allows the preferential sampling of the steep-gradient region of an expanding plasma and permits two-dimensional, multiple-time recordings on a single photograph. The studies are aimed at understanding the early-time physics of target implosions for inertial confinement fusion. Both long (500-ps) and short (150-ps) probe pulses were used to study the rear-side plasmas of thin foils accelerated by the rocketlike reaction to a hot plasma ablated from the front side by the laser radiation. The longer pulse results, both for angular scatter and the lifetime of small, transverse structure, imply a relatively cold (∼1 eV) rear-side plasma. The short pulses provide high-resolution photographs of the complete structure. These observations are relevant to two of the basic requirements of inertial confinement fusion: cold fuel isentrope and implosion symmetry.
Electron paramagnetic resonance study on the annealing behavior of vacuum deposited amorphous silicon on crystalline silicon
Authors: Ohdomari Iwao , Kakumu Masakazu , Sugahara Hirohiko , Hori Masaru , Saito Toshio , Yonehara Takao , Hajimoto Yoshioki
Published: February 2003

Structure of amorphous silicon (a-Si) vacuum deposited on single-crystal (100) silicon (c-Si) with and without clean surfaces achieved by ion sputtering and annealing has been examined by using electron paramagnetic resonance (EPR) and transmission electron microscopy (TEM) as a function of annealing temperature. Annealing behavior of EPR signal can be explained well on the basis of TEM observation that there are void networks in a-Si film deposited on c-Si with native oxide but no such structure in a-Si film on c-Si with clean surface. Structure of a-Si, where solid phase epitaxial growth occurs at a high rate, is compared with that of ion bombarded a-Si.
Transverse acoustoelectric effect in the separated-medium surface-wave configuration
Authors: Fritz I. J.
Published: February 2003

The transverse acoustoelectric voltage (TAV) produced in an ideal semiconductor by a surface acoustic wave propagating along an adjacent piezoelectric has been recalculated following a procedure similar to that in the original calculation of Gulyaev et al. [Yu. V. Gulyaev, A. Yu. Karabanov, A. M. Kmita, A. V. Medved′, and Sh. S. Tursunov, Fiz. Tverd. Tela 12, 2595 (1970)]. It appears that the original calculation contains an algebraic error, which results in an incorrect functional form for the TAV. In particular, it is shown here that the TAV undergoes a reversal of sign as function of frequency (or resistivity), even under flatband conditions and with only a single carrier type being involved in the interaction. At low frequencies (or low resistivities) the sign of the transverse effect is such that the surface of the semiconductor is accumulated, in agreement with experiments on low-resistivity materials. The present calculations agree (in the appropriate limits) with the more complicated formal calculation of Morita et al. [S. Morita, K. Tsubouchi, and N. Mikoshiba, Jpn. J. Appl. Phys. 15, 1019 (1976)]. It is suggested that a number of experimental results in the literature, which appear contradictory and somewhat confusing, can be reinterpreted in a reasonable manner if the inversion of the TAV with resistivity is accounted for.
Electromagnetic implosions of cylindrical gas ’’shells’’
Authors: Degnan James H. , Reinovsky Robert E. , Honea David L. , Bengtson Roger D.
Published: February 2003

Electromagnetic implosions of 20-cm radius, 2-cm tall, few centimeter thick gas ’’shells’’ using a 2-MA, 80-kV, 0.8-μsec capacitor bank have been conducted. Implosion velocities ≳100 cm/μsec and implosion kinetic energies as high as ∼12 kJ, which is ∼17% of the 70-kJ stored energy in the capacitor bank, have been achieved. Photon yields ≳ 1 kJ above 150 eV and neutron yields ∼107 have been obtained. Gas injection and preionization, current and voltage data, and fast photography data are discussed. Comparison with higher energy foil implosion experiments is briefly discussed.
Optical properties of phosphorus-doped polycrystalline silicon layers
Authors: Lubberts G. , Burkey B. C. , Moser F. , Trabka E. A.
Published: February 2003

The index of refraction and the absorption coefficient of low-pressure chemical vapor deposited polycrystalline silicon (poly Si) implanted with various doses of phosphorus were obtained by means of transmittance and reflectance measurements. The refractive index of poly Si is relatively insensitive to doping in the visible region of the spectrum and agrees quite well with published values for single-crystal Si. The absorption coefficient of these films decreases with doping in the visible. Nevertheless, the absorption coefficient corresponding to the highest-doped film (N≊3×1020/cm3) is almost twice the published values for lightly doped single-crystal Si. In the infrared, the index of refraction decreases systematically and the absorption coefficient increases systematically with doping. This dependence of the optical parameters on doping is attributed to the presence of free carriers. A free-carrier dispersion/absorption model is applied to the measured refractive index in the region 1.2–1.8 μm and to the reflectance measurements in the region 2.5–7.5 μm. The model gives carrier concentrations for the two types of measurements which differ by 50%. Possible explanations for this difference are discussed. The carrier concentrations and mobilities obtained from optical and Hall-effect measurements are compared.
Optical properties and transport in microcrystalline silicon prepared at temperatures below 400 °C
Authors: Richter H. , Ley L.
Published: February 2003

Microcrystalline silicon (grain size ∼100 Å) films have been prepared at temperatures below 400 °C through an H2-plasma assisted transport process. The films contain an average of ∼2 at. % of hydrogen which is predominantly situated in the grain boundary regions in the form of Si-H2. The optical absorption coefficient of these films exceeds that of crystalline Si by up to two orders of magnitude below 3.0 eV. The films can be doped by adding PH3 to the hydrogen plasma. The highest room-temperature conductivity so achieved was ∼1 (Ω−1 cm−1). From an analysis of the activation energies vs dopant concentration we deduce that the high-temperature transport (T≳330 °K) is barrier limited. The upper limit for the density of trapping states in the grain boundaries is 1×1013 cm−2.
Near-band gap absorption and photoluminescence of In0.53Ga0.47As semiconductor alloy
Authors: Chen Yu-Ssu , Kim O. K.
Published: February 2003

In this paper, the near-band-gap absorption and photoluminescence (PL) spectra of In0.53Ga0.47As liquid-phase epitaxial layers are reported. We observed, for the first time, the free exciton absorption peak in the transmission spectra and determined the exciton binding energy of 2±1 meV at 5 K for this alloy system. In low temperature PL spectra, a sharp peak (FWHM = 3∼16 meV) observed for all n-type (undoped, Si-doped, or Sn-doped) samples was assigned to be a donor-to valence band transition. The donor ionization energy was determined to be ∼10 meV. A weak second peak at ∼20 meV below the donor-to-band transition with FWHM = 15∼20 meV was also seen in these samples. It is likely to be a donor-to-acceptor pair transition. For undoped samples, the intensity of this peak relative to that of the donor-to-band transition decreased as the doping density decreased and was negligible for samples with residual doping less than 2×1015cm−3. A broad acceptor-to-donor pair transition PL peak was observed for Zn-doped samples.
Theoretical and experimental study of the Lamb wave eigenmodes of vibration in terms of the transducer thickness-to-width ratio
Authors: Delannoy B. , Bruneel C. , Lasota H. , Ghazaleh M.
Published: February 2003

In order to improve ultrasonic systems, like imagers, it is more probably necessary to get a better understanding of the transducer behavior, rather than refine the associated electronic parts. For the completion of this study of transducer behavior, the mathematical finite element model may be used, and then the transducer vibration may be analyzed at a particular frequency. Here, the simpler method of modal analysis has been chosen, since it gives a clearer physical insight. It is shown that a Lamb waves model describes well the propagating modes along the three principal directions of the transducer. Among these modes, those which resonate along the width W have been observed experimentally. The particular interest in these modes arise from the fact that they induce severe distortions in the acoustic radiation pattern and must therefore be suppressed. Moreover, the modes which resonate along the thickness t must be retained, since their contribution to the radiation pattern is essential. Then an optimal geometry may be found for a transducer operating at a given nominal frequency.
Growth of tungsten single-crystal films deposited on MgO(100) substrate
Authors: Igarashi Yuichiro , Kanayama Michio
Published: February 2003

The growth of tungsten single-crystal films on MgO(100) substrate has been achieved by means of the newly developed ’’ultrahigh vacuum arc evaporation’’ method. The necessary conditions for the growth were found through the so-called ’’design of experiments’’ method. From the experimental results, the levels of effective factors for single-crystal growth are discussed. Epitaxy temperatures were observed starting from about 250 °C, which is a relatively low temperature in spite of the high melting point of tungsten.
Characteristics of ion-induced supersaturated Au-Ni alloy films
Authors: Tsaur B. Y. , Mäenpää M.
Published: February 2003

Supersaturated metastable Au-Ni solid solutions have been obtained by ion-beam mixing of thin deposited Au and Ni layers of compositions Au75Ni25,Au50Ni50, and Au25Ni75. The alloys so obtained were studied by MeV 4He+ backscattering, x-ray diffraction, electrical resistivity, and transmission electron microscope measurements. X-ray diffraction analysis showed that the lattice parameters of the ion-induced alloys varied almost linearly with the composition with a slight positive deviation from Vegard’s law for ideal solid solutions. A pronounced increase of grain size in the films was observed as a result of ion-beam mixing along with a change of microstructure from a weak (111) texture to a strong (111) texture. The stability of those ion-induced Au-Ni alloy films has been examined by isothermal annealing at temperatures up to 550 °C. Decomposition of the alloys occurred at temperatures above 300 °C as indicated by resistivity and x-ray diffraction measurements. For dilute alloys (Au75Ni25 and Au25Ni75), decomposition proceeded by a discontinuous reaction where simultaneous presence of the equilibrium Au-rich phase, Ni-rich phase, and the original metastable phase was found. The composition of the metastable phase remained nearly constant during the decomposition. However, the concentrated alloy (Au50Ni50) displayed a continuous precipitation mechanism where a concentration gradient varying from Au50Ni50 to a Au-rich composition was present in the parent phase during decomposition. The precipitation kinetics of Au50Ni50 alloys have been studied by transmission electron microscopy. The possible origins for the occurrence of continuous precipitation phenomenon in the ion-induced Au50Ni50 alloy are discussed.
ZnO varistors for protection against nuclear electromagnetic pulses
Authors: Philipp Herbert R. , Levinson Lionel M.
Published: February 2003

The use of ZnO-based metal-oxide-varistor materials in a transient protection device for communications circuits against the effects of nuclear electromagnetic pulses (NEMP) is discussed. The guidelines for such devices call for subnanosecond response time to NEMP and an insertion loss of less than 0.4 dB at 100 MHz. We have measured the response of varistor materials to ∼500-ps rise time pulses of various amplitudes and durations. No varistor ’’turn on’’ time is evident in these data indicating that the initiation of the highly nonlinear conduction process takes place in less than 5×10−10 s. The insertion loss is calculated from the known high-frequency electrical properties and found to agree quite closely with the experimentally determined value of 0.1 dB at 100 MHz for varistor chips of cross section 0.025×0.025 cm and thickness 0.01 cm. A packaging configuration for these chips is also described. We conclude that ZnO varistors have application in an NEMP protective device.
Theory of magnetic levitation for biaxial systems
Authors: Bird J. F.
Published: February 2003

The magnetic suspension system consisting of a metallic cylindrical shell encircling an alternating-current filament is analyzed by vector field methods for arbitrary relative orientations of shell and current axes. The induced magnetic field and resulting force-torque system, and associated eddy-currents, are calculated for a variety of shell constructions: homogeneous shells, shells with annular hollow space, and shells composed of annular layers of different metals. End effects neglected in the computations are analyzed in a companion paper. The biaxial shell-filament systems treated model the magnetic suspension in ’’disturbance compensation systems’’ for Navy navigational satellites.
Phonon anomalies in intermediate valent TmXSe and TmSe1−yTey
Authors: Boppart H. , Treindl A. , Wachter P.
Published: February 2003

In TmxSe and TmSe1−yTey the degree of valence mixing can be adjusted between nearly 3+ for Tm0.87Se and 2.55+ for TmSe0.7Te0.3. The measurement of sound velocities vL, vTl and vT2 and the evaluation of the Raman effect for various compositions permit the derivation of LA [111] phonon dispersion at critical points in the Brillouin zone. vL decreases with increasing valence mixing. Near the middle of the zone the LA branch gets a dip for intermediate valent compositions, resulting in a characteristic peak in the Ramn spectrum at about 60 cm−1. The elastic constant c12 has been found negative for Tm0.99Se, also at 4.2 K. For uniaxial pressures c12 exhibits strong nonlinearities and even changes sign with pressure in an intermediate valent composition. The optical phonon frequencies, LO (L) also soften proportional with the degree of valence mixing.
Dynamic behavior of small bits written by laser irradiation on GdFe films
Authors: Honda Shigeo , Ueda Koso , Kusuda Tetsuzo
Published: February 2003

Field nucleation and collapse of small bits have been investigated under a laser beam irradiation on an amorphous GdFe sputtered film by means of the photometric method. The writing process of a bit consists of the motion of the ’’head-on wall’’ along the film thickness and then the radial motion of the ’’side wall.’’ Small bits are stable at higher temperature during beam irradiation, but they collapse during cooling to room temperature near the compensation point after cutting off the laser beam, because the wall energy tension overcomes the coercive field near the compensation point. The conventional thermomagnetic writing was also carried out by pulse laser irradiation of non-coated and Ni-coated GdFe films. It was found that the small bits can be stabilized by coating a Ni-layer thicker than 200 Å.
Atomic hydrogen: A weakly interacting, magnetic Bose gas (invited)
Authors: Berlinsky A. J.
Published: February 2003

Spin-polarized, atomic hydrogen at temperatures below 1K shows promise of becoming the first physically realizable example of a degenerate, weakly interacting Bose gas. Because of the hyperfine structure of the hydrogen atom the Bose condensed state is expected to exhibit novel magnetic properties such as spin wave excitations of the superfluid and possibly a coherent precessing, spontaneous magnetization. This paper discusses a variety of theoretical problems which arise in the study of atomic hydrogen gas. Theories are presented for spin relaxation of the hyperfine levels and for the recombination of H-atoms into H2 molecules. The problem of the binding of H atoms to a surface of superfluid 4He is reviewed together with the theory of surface superfluidity in the hydrogen film proposed by Edwards and Mantz. Finally we consider the problem of superfluidity in the bulk atomic hydrogen gas. We describe the theory of Siggia and Ruckenstein of double Bose condensation into the two lowest hyperfine states and speculate about the possible observable consequences of this phenomenon.
Triangular propagation patterns for contiguous-disk magnetic bubble devices
Authors: Shir C. C.
Published: February 2003

Triangular propagation patterns1 are proposed for contiguous-disk magnetic bubble devices in ion-implanted garnet films with tridirectional crystalline inplane anisotropy. These patterns offer superior results in bias field margins (53 Oe or 15%), and allow decreases in inplane drive field as well as high frequency operations (up to 700 kHz). The underlying theory for designing the propagation pattern based on the three-vetex critical curves and micromagnetic structures is discussed. A simple design rule for pattern geometry and orientation to optimize the bias margin and minimum drive is presented.
Transient solution of the diffusion equation by the finite element method
Authors: Tandon S. C. , Chari M. V. K.
Published: February 2003

This paper describes the application of the finite element method for solving transient electromagnetic field problems. Galerkin’s procedure is used to derive the element equations and first order triangular elements are used to discretize the field region. An implicit tie step integration technique is employed to convert the resulting discrete differential equations into a set of nonlinear algebraic equations which are then solved at each time step. The method is applied to a one-dimensional field problem and to an electrical machine under transient operating condition.
Induced magnetic anisotropy of Co-based amorphous alloys
Authors: Makino Y. , Aso K. , Uedaira S. , Hayakawa M. , Ochiai Y. , Hotai H.
Published: February 2003

The effect of the rotating magnetic field annealing on high magnetic induction amorphous alloy Fe5Co75Si4B16 (TC≳Tx) was studied. Experimental results and the theoretical analysis gave the following conclusions. 1) Induced magnetic anisotropy is dispersed by the rotating magnetic field annealing. 2) The relationship between magnetic permeability μ and number of rotations R is given by the formula 3) The rotating field annealing is useful to eliminate the induced magnetic anisotropy, especially for the amorphous materials with TC≳Tx.
Recovery characteristic of exploding wire fuses in air and vacuum
Authors: Vitkovitsky I. M. , Scherrer V. E.
Published: February 2003

The dielectric strength of exploded wire fuses during the vaporization and after recovery period and fuse resistivity are functions of time and depend on the medium surrounding the fuse channel. When fuses are used as opening switches in inductive storage systems, the above parameters determine the efficiency of power flow from the storage to the load. Specifically, design of experiments using loads with variable impedance, such as imploding plasma, requires detailed information on the fuse characteristics during the time when the load impedance is changing. To provide data that determine the interaction between fuses and variable impedance loads, inductive and recovery electric fields and fuse resistance in air and vacuum were studied. The results show that inductive field amplitude follows the dependence on time needed to vaporize the fuse in a manner similar to that established for fuses in other media. The characteristics of recovery rates of fuses in air and vacuum differ drastically due to the early onset of ionization in fuse channels in vacuum.
Ion extraction from a plasma
Authors: Aston G. , Wilbur P. J.
Published: February 2003

An experimental investigation of the physical processes governing ion extraction from a plasma is presented. The screen hole plasma sheath of a multiaperture ion accelerator system is defined by equipotential plots for a variety of accelerator system geometries and operating conditions. A sheath thickness of at least 15 Debye lengths is shown to be typical. The electron density variation within the sheath satisfies a Maxwell-Boltzmann density distribution at an effective electron temperature dependent on the discharge plasma primary-to-Maxwellian electron density ratio. Plasma ion flow up to and through the sheath is predominately one dimensional and the ions enter the sheath with a modified Bohm velocity. Low values of the screen grid thickness to screen hole diameter ratio give good ion focusing and high extracted ion currents because of the effect of screen webbing on ion focusing.
Directional coupling of magnetostatic surface waves in a layered structure of YIG films
Authors: Sasaki Hiroshi , Mikoshiba Nobuo
Published: February 2003

The directional coupling of magnetostatic surface waves propagating in a layered structure where two YIG films are located in parallel with a small gap between them are theoretically investigated. Due to strong dispersion of magnetostatic surface waves, this directional coupler shows frequency filtering and frequency demultiplexing characteristics which can be tuned by an applied magnetic field.
Torque measurements of induced anisotropy in amorphous Fe80−xB20+x alloys
Authors: Allia P. , Luborsky F. E. , Soardo G. P. , Vinai F.
Published: February 2003

Torque magnetometer measurements were used to obtain the anisotropy energy ku induced by magnetic annealing (up to 6 h at temperatures from 50 to 70 °C below crystallization) on special patchwork samples of amorphous Fe80−xB20+x ribbons (−6⩽x⩽+6). The dependence of ku on annealing time and temperature tends to show that the directional ordering processes are characterized by a very wide distribution of activation energies. At a constant temperature and time ku is independent of composition, as was also found in results on stress relaxation but not in results on crystallization. Thus different atomic processes control ku than control crystallization.
The mobility of gold in silver chloride
Authors: Tan Y. T. , Marchetti A. P.
Published: February 2003

The distribution depth profile of an Au-doped AgCl single crystal was measured with ion-scattering spectrometry. The results indicate that Au is mobile at room temperature and has a tendency to segregate towards the surface.
InGaAsP-InP planar-stripe lasers fabricated by wet chemical etching
Authors: Adachi S. , Kawaguchi H.
Published: February 2003

InGaAsP-InP planar-stripe lasers are fabricated monolithically, in which cavity mirrors are formed by wet chemical etching and planar stripes are aligned along the [100] direction. The lasers emit light at ∼1.5 μm. The lowest threshold current density of these lasers is almost the same as that of conventionally fabricated cleaved-mirror lasers.
A derivation of Warburg’s law for point to plane coronas
Authors: Henson Bob L.
Published: February 2003

Warburg’s law, which describes the distribution of the current density over the plane electrode for a point to plane steady corona discharge, is derived. The derivation is based on a model using hyperboloid point to plane geometry with a constant charge carrier mobility model and a time independent potential. The derived relation is shown to be in exact agreement with the empirical law when the calculations are done for an infinite plane electrode.
The effect of sea level cosmic rays on electronic devices
Authors: Ziegler J. F. , Lanford W. A.
Published: February 2003

Calculations are made of the rates at which bursts of electronic charge are created in silicon by cosmic rays at sea level. These rates are reduced to two types: point charge bursts and distributed ionization wake bursts. A procedure is shown to evaluate the soft fail rates of simple devices caused by cosmic rays. It is shown that an 8-M byte semiconductor memory made of 10×10 μm diodes will have a soft fail rate of about one per day.
Ultraviolet photoelectron spectroscopy study of the adsorption of oxygen on reduced SrTiO3 surfaces
Authors: Ferrer S. , Somorjai G. S.
Published: February 2003

The adsorption of oxygen on a reduced SrTiO3 (111) surface occurs in two distinct phases. At low exposures (less than 1 L), the adsorption leads to the incorporation of O = ions into the vacant lattice oxygen sites. At higher exposures a second different oxygen species adsorbs.
Numerical simulation of oscillating magnetrons
Authors: Palevsky A. , Bekefi G. , Drobot A. T.
Published: February 2003

The temporal evolution of the current, voltage, and rf fields in magnetron-type devices has been simulated numerically by a two-dimensional, electromagnetic, fully relativistic particle-in-cell code. The simulation allows for the complete geometry of the anode vane structure, space-charge-limited cathode emission, and the external power source. The code has been applied to magnetrons operating in the relativistic energy regime.