bluuebunny/crossref_metadata_2025 huggingface dataset:
Comment on ‘‘A study of cathode edge emission’’
Authors: Hasker J.
Published: February 2003

In a recent paper, Yong-xiang Zhao ascribed the perveance increase with decreasing accelerating potential —as found experimentally for klystrons— to ‘‘cathode edge emission.’’ It is shown in the present ‘‘Comment’’ that this treatment is subject to serious doubt and that the perveance increase must be due to the fact that both cathode temperature and cathode saturation current density are kept constant when decreasing the accelerating potential. The magnitude of the increase is demonstrated by means of some approximate calculations.
Mechanism of catastrophic degradation in 1.3-μm V-grooved substrate buried-heterostructure lasers with the application of large pulsed currents
Authors: Ueda Osamu , Imai Hajime , Yamaguchi Akio , Komiya Satoshi , Umebu Itsuo , Kotani Tsuyoshi
Published: February 2003

Catastrophic degradation of V-grooved substrate buried-heterostructure InGaAsP/InP lasers (λ=1.3 μm), by large pulsed currents, has been investigated using scanning electron microscopy, etching technique, energy dispersive x-ray spectroscopy, and spatially resolved photoluminescence topography. After the degradation, the diode stops lasing and becomes ohmic. These are associated with the following phenomena: (i) facet erosion inside or outside the stripe region; (ii) penetration of the electrode-metals into the epitaxial layer. These phenomena are presumably caused by the abrupt passage of large current along the facet or by local heating at the contact region outside the stripe region. Catastrophic optical damage, which frequently occurs in GaAlAs/GaAs double-heterostructure lasers, is not observed in any part of the degraded diodes.
Two-dimensional mode analysis of the Raman-type free-electron laser
Authors: Shiozawa T. , Nakashima T.
Published: February 2003

The effects of an arbitrary beam thickness and a conducting wall in the Raman-type free-electron laser are investigated. To simplify the problem, a two-dimensional model of a solid nonmagnetized relativistic electron beam enclosed with a parallel plate waveguide is considered. With the aid of the fluid theory for electron beams, the coupled mode equation relating the scattered wave (TE mode) and the electron plasma wave (TM mode) under the influence of the pump wave (TE mode) is derived. By using the solution to the coupled mode equation, together with the boundary conditions on the beam surface, the dispersion relation and the spatial growth rate for the coupled scattered and electron plasma waves are found. From detailed numerical analysis for the properties of the scattered wave, several interesting results are obtained. First, in order to get an appreciable magnitude of the growth rate, the beam width and the separation between the conducting walls of a parallel plate waveguide are required to be considerably greater than the wavelength of the scattered wave. Second, the growth rate becomes maximum for particular values of the ratio of the beam thickness to the separation between the conducting walls. Third, the growth rate can be greater for the pump and scattered waves with even symmetry than for those with odd symmetry.
Control of OH catalyst in a CO2 laser via NbHx-H2 equilibrium
Authors: Karube N. , Iehisa N. , Yamadaya T.
Published: February 2003

The partial pressure of H2 in a sealed-off CO2 laser was controlled by changing the temperature of a Pd-plated NbHx specimen placed in the laser tube. It was shown that the pressure control could be performed uniquely even in the presence of H2 adsorption or outgassing, provided the quantity of Nb exceeded a certain amount. Controlling the H2 pressure led to varying the concentration of OH radicals in the CO2 laser plasma, the catalytic activity of which was monitored as the change of laser output power.
Stripe geometry lead-telluride diode lasers grown by molecular beam epitaxy
Authors: Partin D. L. , Majkowski R. F. , Thrush C. M.
Published: February 2003

Lead-telluride homojunction diode lasers suitable for ultrahigh resolution spectroscopy have been fabricated using molecular-beam epitaxial (MBE) growth and a mesa stripe geometry. A low-MBE substrate growth temperature of 260 °C was used to minimize interdiffusion during growth. These lasers operate up to 115 K cw with emission in the 6.5–5.0-μm wavelength range. The threshold current density follows the relation J=J0 exp(T/T0) up to 100 K, with J0=110 A/cm2 and T0=26.0 K. Thermal resistance effects cause a departure from this relationship at higher temperatures. The current-voltage relationship as a function of temperature indicates that tunneling currents contribute significantly to the threshold current density. Single-fundamental mode emission is obtained from 20-μm-wide mesa stripes at high temperature, whereas a higher order mode is observed with 35-μm-wide stripes. Analysis of the near and far field patterns indicates that the lasing mode is index guided at high temperatures, and gain guided at low temperatures. Single-mode output powers of over 1 mW/facet are obtained in 90–100 K with high-external differential quantum efficiencies (5%–6%/facet).
Third harmonic generation efficiency at higher powers in a collisional plasma
Authors: Sharma A. K.
Published: February 2003

A high amplitude electromagnetic wave propagating through a collisional plasma heats the electrons, modulates their collision frequency and generates a third harmonic electromagnetic wave. In the steady state the oscillatory component of electron temperature is electron to ion mass ratio times smaller than the nonoscillatory part. Consequently the harmonic generation efficiency even at very high powers is very small (≲10−5%). In a pulsed operation, when the duration of the pulse is much shorter than the energy relaxation time, the ratio of oscillatory to nonoscillatory components of electron temperature could attain values of the order of unity at high powers and power conversion efficiency of the order of 1% can be obtained.
Perturbing conductor effects on wave studies in a double plasma device
Authors: Bulson Jeffry M. , Huynh Khoa , Gabl Edward F. , Lonngren Karl E.
Published: February 2003

The effects on ion-acoustic wave propagation caused by the introduction of a large biased metal plate close to and parallel to the separation grid in the target chamber of a double plasma machine are experimentally examined. It is found that the biased plate can re-excite ion-acoustic waves and can act as an externally controlled phase shifter.
Computer simulation of gas transport in a magnetically stabilized glow discharge
Authors: Antoniuk D. M. , Capjack C. E. , Seguin H. J. J.
Published: February 2003

Gas flow in a magnetically stabilized glow discharge is analyzed by using a single fluid magnetogasdynamic model. The resulting system of time dependent, nonlinear, coupled partial differential equations is solved numerically on an Eulerian mesh by using an iterative alternating direction implicit finite difference method. The numerical results reveal the importance of considering the secondary flows that are driven by the strongly sheared rotational flow within the discharge volume. The numerical results are confirmed experimentally.
Formative processes of cold-cathode Penning discharges at low pressures
Authors: Kageyama Katsuhiro
Published: February 2003

Formative times td, the time intervals between application of stepped discharge voltages and appearance of discharge currents, for cold-cathode Penning discharges were investigated to reveal their formative processes. Experimentally, a spontaneous discharge initiation belongs to either of two distinct patterns, in that td values (1) scatter over a broad time range and are distributed exponentially, or (2) concentrate in a short time range where the difference between the maximum and the minimum is far smaller than the mean. Low discharge voltages result in initiation in pattern (1), while high voltages result in initiation in (2). Magnetic field and pressure do not explicitly affect an initiation-pattern decision. A thin pin fixed on a cathode plate is effective in causing initiation in pattern (2). The discharge was revealed to be triggered by an electron extracted from the cathode by a strong electric field. Two models for the formative processes were presented. Every electron extracted from the cathode is assumed to be, in one model, reabsorbed by the cathode after a flight unless it collides with gas molecules, or in the other model, captured in the Penning trap. Discharge-formative properties were formulated from those models. They include discharge-current waveforms, dependence on discharge conditions of means, dispersion-to-mean ratios, and distribution patterns of td values. The experimental results agree quantitatively with theoretical results derived from either of the two models. This agreement shows that both the models are valid. For an actual discharge, in which model its formation proceeds is decided by the condition for the discharge.
Optical and electrical properties of ion-beam-irradiated films of organic molecular solids and polymers
Authors: Kaplan M. L. , Forrest S. R. , Schmidt P. H. , Venkatesan T.
Published: February 2003

Thin films of several nonpolymeric and polymeric organic compounds become optically dark and electrically conducting on irradiation with energetic particle beams. Using 2-MeV Ar+ ion beam irradiation, we have generated conducting patterns in otherwise high-resistivity, organic thin films among which are 3, 4, 9, 10-perylenetetracarboxylic dianhydride, 1, 4, 5, 8-napthalenetetracarboxylic dianhydride, and Ni phthalocyanine. The room-temperature resistivity of the films changes by 14 orders of magnitude from its as-deposited value of ρ>1010 Ω cm to ρ=5×10−4 Ω cm at ion doses of 1017 cm−2. The temperature (T) dependence of the resistivity follows ρ(T)∝exp(+(T0/T)1/2 ) over a wide range of dose and temperature. The characteristic temperature T0 is found to be a function of dose. The observed behavior of ρ(T) is consistent with charge transport due to hopping between isolated, conducting islands. The dependence on ion energy, ion species, and ion dose rate has been examined. The effectiveness of an ionic species in increasing a film conductivity increases with electronic energy loss of the ion in the film. Compound specific sensitivity towards ion irradiation was demonstrated. Nonlinear effects of ion dose rate were also observed. The final carbon-rich product has some characteristics similar to those of amorphous carbon; however, the conductivity is higher and the electrical behavior is different.
New theory of electrical discharge and breakdown in low-mobility condensed insulators
Authors: Kao Kwan C.
Published: February 2003

Electrical discharge and breakdown in low-mobility insulating liquids and solids involve the creation of low-density domains or channels in the bulk by carrier injection from electrical contacts and subsequently dissociative trapping and recombination as a necessary prelude. Internal discharge such as electrical treeing and breakdown are initiated by impact ionization within such low-density domains or channels and then followed by an indefinite increase in carrier multiplication in the conduction level that extends the channels and finally destroys the material inside them.
Vacuum ultraviolet optical properties of squalane and squalene
Authors: Painter L. R. , Attrey J. S. , Hubbell H. H. , Birkhoff R. D.
Published: February 2003

The reflectance of liquids squalane and squalene between 2 and 25 eV have been determined by closed cell double ionization chamber methods. Kramers–Kronig analysis of the data gives optical functions from which are calculated the dielectric functions, energy loss functions, and mean free path for photons and electrons. Values of yield predicted from a theoretical model of photoemission are found to be about 11% at 16 eV declining to 4% at 25 eV. However, no photoemission was observed over this energy range.
Laser-induced bulk damage in SiO2 at 1.064, 0.532, and 0.355 μm
Authors: Merkle Larry D. , Koumvakalis N. , Bass M.
Published: February 2003

Single- and multiple-pulse laser-induced bulk damage of fused and crystalline SiO2 has been investigated. We studied the dependence of the intensity required to produce macroscopic damage upon wavelength, focal spot size, pulse duration, and pulse repetition frequency. It is found that the material must undergo some undetected microscopic change prior to macroscopic damage which increases the probability of damage with increasing number of pulses. The multiple pulse damage depends strongly on spot size, occurring in far fewer pulses at larger spot sizes than at small ones, and displays a significant dependence on pulse length and repetition frequency. Possible mechanisms are discussed.
The equation of state of the gold calibration standard
Authors: Heinz Dion L. , Jeanloz Raymond
Published: February 2003

The compression of Au has been measured at room temperature to 70 GPa (700 kbar) using x-ray diffraction through a diamond-anvil cell and the ruby-fluorescence pressure scale. Based on these data, the isothermal bulk modulus and its pressure derivative at zero pressure are K0T =167 (±11) GPa, and K′0T=5.5 (±0.8). These results are in excellent agreement with ultrasonic measurements of the elastic constants as well as an equation of state based on shock-wave data. Hence, this study represents an independent experimental confirmation of both the ruby fluorescence pressure scale, and the predicted equation of state of the proposed Au pressure calibration standard. We derive a thermal equation of state for gold by inverting all equation-of-state data simultaneously. From this, we extend the gold pressure-calibration standard to cover the range 0–200 GPa in pressure and 300–3000 K in temperature.
Stoichiometric determination of SbCl5-graphite intercalation compounds using Rutherford backscattering spectrometry
Authors: Elman B. S. , Salamanca-Riba L. , Dresselhaus M. S. , Venkatesan T.
Published: February 2003

Rutherford backscattering spectrometry (RBS) is used for the first time to characterize the stoichiometry of a graphite intercalation compound (GIC). This technique provides direct information about the depth and lateral distribution of intercalant, which is of particular importance for this class of materials. Such information is difficult to obtain by other techniques. In this work, explicit application is made to the SbCl5-GIC system. Results for the stoichiometry of Cξn SbClm are reported in terms of values of ξ and m for cleaved and as grown (uncleaved) samples. Because of the depth sensitivity of the RBS technique, we are able to show that the stoichiometry at the surface of as-prepared intercalated graphite samples may differ significantly from the Cl:Sb ratio of 5:1 and need not be similar to that of the bulk. However, within experimental error, the RBS results on the cleaved samples are consistent with those obtained by analysis of (00l) x-ray diffraction spectra.
Stress evolution and point defect generation during oxidation of silicon
Authors: Charitat G. , Martinez A.
Published: February 2003

The oxidation enhanced diffusion and oxidation stacking faults are assumed to be brought about by a self-interstitial supersaturation in the silicon. In such a case, supersaturation is related to the stresses present in the oxide and in the silicon during oxidation. The detailed analysis of the evolution of these stresses is conducted in relation to time, temperature and the nature of the oxidizing atmosphere, taking into account the viscous relaxation in the oxide. The silicon interstitial concentration during oxidation is directly linked with the stress in the silicon. This stress, which is a function of the stress evolution in the oxide enables us to describe qualitatively the experimental behavior of OED and OSF. However, quantitative analysis of stresses in silicon gives values insufficient to lead to a non-negligible self-interstitials concentration.
Phase separation and layer sequence reversal during silicide formation with Ni-Cr alloys and Ni-Cr bilayers
Authors: Appelbaum A. , Eizenberg M. , Brener R.
Published: February 2003

Solid-state reactions of thin films of Ni–Cr alloys, and Ni–Cr bilayers, with Si have been studied by Auger electron spectroscopy and x-ray diffraction. Silicide formation for the alloys which starts at ∼400 °C is completed (after 30 min anneal) for Cr-rich and Ni-rich compositions at 500 and 600 °C, respectively, with phase separation into a NiSi layer near the substrate and a CrSi2 rich layer outside. For the Cr/Ni/Si structure each of the layers reacts independently with Si; structures of Cr/Ni2Si/Si, Cr/NiSi/Si, CrSi2/NiSi/Si, and CrSi2/NiSi2/Si are obtained following 30-min anneals at 300, 400, 500, and 850 °C, respectively. For the Ni/Cr/Si structure for annealing temperatures in the range of 500–750 °C, the inner part of the Cr layer reacts with the substrate to form CrSi2, while the outer part forms a solid solution with Ni; the interaction of this solution with Si results in the inward formation of NiSi and the outward formation of CrSi2. After 850 °C anneal layer sequence reversal is observed, when a NiSi2 layer is formed adjacent to the Si substrate.
Reversal in the growth or dissolution of III-V heterostructures by liquid phase epitaxy
Authors: Small M. B. , Ghez R.
Published: February 2003

It is shown, by simulation, that two classes of system exist in the formation of heterostructures by liquid phase epitaxy which we had not previously considered fully. In these, the initial tendency of the system of solid and solution to either grow (due to a supersaturated solution) or dissolve (due to an undersaturated solution) is reversed, if the tendency for the combination of nonequilibrium solid and the saturated solution is either to dissolve or grow, respectively. In particular, a simulation is applied to the case of an undersaturated solution in the Ga-In-As system in contact with a GaAs wafer to show that the resulting solution becomes supersaturated; this is in agreement with experimental observations.
Evaluation of the statistical distribution of fracture strength: Discussion of some recent contributions
Authors: Rosenfield A. R. , Shetty D. K. , Duckworth W. H.
Published: February 2003

Several recent statistical analyses of ceramic strength have concentrated on the form of the distribution function associated with a set of uniform specimens. It is pointed out that prediction of the effect of specimen size is an integral part of current statistical strength theory, and can be used to discriminate among alternative distribution functions.
Ion beam irradiated via-connect through an insulating polymer layer
Authors: Venkatesan T. , Feldman M. , Wilkens B. J. , Willenbrock W. E.
Published: February 2003

Ion beams can render a polymer film conductive (ρ∼3×10−3 Ω cm measured by a four-probe technique). Using this effect we show that an insulating polymer layer used as an isolating layer between two conducting layers can be electrically shorted by heavy ion beam irradiation. This technique, besides enabling a measurement of the resistivity in the orthogonal direction, demonstrates the feasibility of using a polymer as an insulating layer with a direct via-connect produced across it by ion beam irradiation. The measured resistivities perpendicular (ρ⊥ ) and parallel (ρ∥ ) to the film plane within experimental measurements show that ion-beam induced conductivity in these films is isotropic. The isotropy of the conductivity suggests nonspecular scattering of the carriers in these disordered films.
Depth profiles of interstitial oxygen concentrations in silicon subjected to three-step annealing
Authors: Isomae Seiichi , Aoki Shigeru , Watanabe Kikuo
Published: February 2003

In relation to intrinsic gettering, the dependence of denuded zone width and thermally induced microdefect density on thermal conditions are investigated in a three-step annealing procedure consisting of high temperature annealing, low temperature, and dry O2 oxidation at 1000 °C. Additionally, depth profiles of interstitial oxygen concentrations are studied using thermal conversion. The obtained results show that at least an initial interstitial oxygen concentration above 8×1017 cm−3 is required to achieve efficient intrinsic gettering. The depth profile obtained after the third annealing is not the simple out-diffusion profile approximated by an error function, but one with a peak in the denuded zone. The dependence of depth profiles on a third annealing condition indicates that the formation of the peak in the depth profile can be ascribed to a reduction of interstitial oxygen resulting from precipitation in the bulk region. In order to explain the obtained profiles, we propose a simple diffusion model which takes into consideration the oxygen precipitation in the bulk region. By comparing the calculated profiles with the experimental ones, it is proved that this model can be used to estimate depth profiles under various annealing conditions.
Contribution of the spreading resistance to high-frequency rectification in metal-metal point contacts
Authors: van der Heijden R. W. , Swartjes H. M. , Wyder P.
Published: February 2003

High-frequency radiation detection by metal-metal point contacts is investigated as a function of bias voltage at far-infrared frequencies. Detection occurs through rectification due to a nonlinearity of the current-voltage characteristic. The relative contribution to the rectification due to an electron phonon scattering mechanism occurring in the bulk material (‘‘spreading resistance’’) is compared with other mechanisms. The spreading resistance nonlinearity was identified by measurements at liquid helium temperatures. For low contact resistances (≲50 Ω) this nonlinearity was generally dominant, for higher resistances it may occur in addition to and independently of the other mechanisms.
Hole traps in p-type electrochemically deposited CdTe thin films
Authors: Ou S. S. , Bindal A. , Stafsudd O. M. , Wang K. L. , Basol B. M.
Published: February 2003

Deep level transient spectroscopy and photoluminescence measurements were performed for the first time on electrodeposited n-CdS/p-CdTe thin film solar cells. The observed levels were hole traps located at 0.2, 0.35, and 0.54 eV above the valence band. The nature of these hole traps can be attributed to the generation of Cd vacancies during the heat treatment step, which was used in device fabrication, to convert the as-deposited n-type films into p-type layers.
Improvement of linewidth control with antireflective coating in optical lithography
Authors: Lin Yi-Ching , Purdes Andrew J. , Saller Steve A. , Hunter William R.
Published: February 2003

Antireflective (AR) coating less than 5000 Å has been investigated to eliminate the light reflection from layers under resist and to reduce the linewidth variation over topographical features. Theoretical calculations based on simulation results using the sample program indicate that more than 50% of the variations at the step crossover can be reduced by eliminating the standing wave effects for a step of height less than 0.8 μm. Several types of AR coating, including TiW, V, polysilicon films, and spun-on layer incorporated with an absorbing dye will be presented and compared. The exposure latitude can be widely extended by the AR coating. Both the standing wave effect and the linewidth change with respect to variation in exposure dose can also be reduced significantly. With the spun-on AR coating, which can be applied, patterned, developed, and stripped with the photoresist, the only steps added to the standard photoresist process are coating and baking the AR layer. Using a 10 : 1 reduction GCA Mann stepper to expose, linewidth variation of the order of 0.3 μm (total range) for 1.2-μm-thick aluminum over 0.5-μm steps, resulting from polysilicon gate patterning, has been demonstrated. There is no adverse undercutting due to the AR layer during the resist development and plasma aluminum etch. This simple and convenient technique can be effectively applied to wafers with topographical steps less than 0.8-μm height.
Growth of Cr doped GaAs single crystals by the gradient freeze method
Authors: Orito Fumio , Tsujikawa Yoshinobu , Tajima Michio
Published: February 2003

Chromium doped GaAs single crystals are grown by a new technique, in which the growth rate is initially high and lowered automatically by a preprogrammed furnace cooling rate in the conventional gradient freeze method. It is shown that Si and Cr distribution in Cr doped GaAs single crystals along the growth direction depends on crystal growth rate. The effect of growth rate on resistivity and leakage current distribution of Cr doped GaAs single crystals is also reported. Distribution of deep levels in the crystal grown by the new technique and the relation to impurity distribution are investigated by photoluminescence spectroscopy.
Dry development of resists exposed to low-energy focused gallium ion beam
Authors: Kuwano Hiroki
Published: February 2003

This paper proposes a new lithography method employing focused ion beam exposure and subsequent dry development. It is shown that the O2 plasma etching or reactive ion etching rate for resists exposed to gallium ions is much lower than that for resists not exposed. A comparison is made between plasma development and reactive ion development. An improvement in the resist sensitivity and contrast value γ using a CF4+O2 mixture gas for reactive ion development is discussed. It is possible to fabricate 0.5-μm-width lines and spaces in 0.6-μm-thick PMMA film at 1×10−4-C/cm2 gallium ion exposure.
Theoretical analysis of amorphous silicon solar cells: Effects of interface recombination
Authors: Sichanugrist Porponth , Konagai Makoto , Takahashi Kiyoshi
Published: February 2003

The carrier continuity equations for both holes and electrons have been solved in amorphous Si (a-Si) p-i-n solar cells, including the diffusion term, hole-electron recombination term represented by a Shockley–Read model, and the interface recombination effect. Furthermore, the characteristics illuminated through the p and n layers have been calculated and compared. It is shown that when the i layer is intrinsic, the fill factors obtained by illuminating through the p and n layer are almost the same and both are more than 0.6. Furthermore, we found that the fill factor strongly depends on the interface recombination and a fill factor of more than 0.7 can be obtained by using heterojunction such as a-SiC:H/a-Si:H to decrease the interface recombination effect.
Electromagnetic particle simulations of self-magnetic-field-enhanced ion diodes
Authors: Seidel D. B. , Olsen J. N. , Rosenthal S. E.
Published: February 2003

Electromagnetic particle simulations of equatorial self-magnetic-field-enhanced ion diodes have been performed. These simulations complement recent experiments on the particle beam fusion accelerator using the pinch ion diode (pid) and the Obi diode. Those experiments are detailed in a companion paper. The simulations have provided useful information concerning the operation of the diode. This paper will describe many of the simulation findings in such areas as current and charge neutralization, virtual cathode formation, diode impedance, ion divergence, and electron temperatures. In addition, a model for ion efficiency has been obtained that is based upon the simulation results. This model is compared to various other efficiency models.
Experimental study of the lasing P/N junction as an electro-optical transducer
Authors: Sommers H. S.
Published: February 2003

An experimental study of the small signal equivalent circuit of the lasing P/N junction itself is presented. The usual study examines the behavior of the packaged device through measurement of the dependence on dc current and on frequency of the modulus of the transfer function relating the stimulated power to the drive current. The present work features the study of the P/N junction itself through a new technique, the direct measurement of the modulus, and the argument of the ratio of the modulation of the stimulated power to the modulation of the spontaneous emission. The frequency modulation of the optical power is also studied, and the results compared with deductions from the present study of the spontaneous emission and from a published study of the amplitude and frequency transfer functions of a similar laser. All the studies support the new finding that the modulations of the junction voltage and the power are in phase with each other for frequencies up to the gigahertz range. The experimental values of the circuit elements show that the damping of the response is due to dissipation in the resistance representing the change in voltage with stimulated power. Comparison of the values of the circuit elements to the solutions of the multimode rate equations gives insight about the utility and limitations of existing formalism, in particular about the extent to which the formalism yields a single set of circuit elements which describes the transient response of all observables and about whether the observed responses are better modelled as those of a classical noise amplifier or a free running oscillator.
An electrically triggered 200 kV rail-gap switch for wide aperture excimer lasers
Authors: Endoh A. , Watanabe S. , Watanabe M.
Published: February 2003

A wide aperture (7×7 cm2), high output energy (5 J in KrF and 13.8 J in XeC1), UV preionized excimer laser is described. A self-breakdown rail gap was employed as an output switch with the maximum voltage and current up to 230 kV and 300 kA, respectively. To solve the switching jitter problem associated with the self-breakdown, an electrical triggering was investigated. The measured minimum switching time delay and gap closing time were 40 and 10 ns, respectively. The number of channels up to 50 was observed with a uniform distribution over the 80-cm electrode length. The triggering jitter was measured to be less than a nanosecond. The maximum operation voltage of the triggered rail gap was 200 kV. The successful trigger operation was obtained in the range 30%–98% of the self-breakdown voltage.
Deformation-induced work function changes in Cu single crystals. I. Experiment
Authors: Chow Robert , Tiller William A.
Published: February 2003

Tensile deformation-induced work function change experiments were conducted in the elastic and plastic regimes on Cu single crystals. Simultaneous measurements of load, displacement, and contact potential difference changes were made on the samples in an ultrahigh vacuum. The work function change to deformation modulus may be as large as 24 μV/MPa in the elastic regime and varied from +1.7 to −11.8 mV/% strain in the plastic regime for different surface orientations.
Cluster center formation in neutron-damaged silicon
Authors: Yousif H. N. , Cowan D. L. , Meese J. M.
Published: February 2003

The production of vacancy clusters in neutron-damaged silicon has been investigated by electron spin resonance. It is found that the production of P3 four vacancies and P6 di-interstitials is independent of oxygen concentration, suggesting that these defects are formed in the primary cascade. Approximately two P3 centers were formed per primary cascade independent of the primary mean recoil energy for irradiations in varying fast neutron spectra. This suggests that these defects are associated with the Brinkman spike which terminates the cascade. Low energy primaries from thermal neutron capture and subsequent gamma recoil are very inefficient in producing these centers.
Evolution towards thermalization, and diffusion, of sputtered particle fluxes: Spatial profiles
Authors: Valles-Abarca J. A. , Gras-Marti A.
Published: February 2003

Particles sputtered from solid targets in plasma deposition systems, under typical vacuum conditions, slow down in collisions with the gas phase. The spatial profiles of particle fluxes at given instantaneous energy are calculated with a simple model of a particle slowing down along straight-line trajectories, subject to a continuous energy-loss process. In particular, the profiles of flux thermalization are given. Model distributions in energy and direction of sputtered fluxes, with a reasonable physical basis, are used. The accumulation and diffusion of thermalized material in the gas phase is studied also, and the stationary spatial profiles are obtained. Diffusion particle currents back to the source, or towards the substrate, can then be estimated. Scaling laws are obtained that allow the analysis of any specific deposition conditions through the masses of the sputtering and sputtered particles, the binding energy of the target, and the working pressure. Because of the simplifying assumptions of the analytical model, predictions in the particular case of light targets sputtered in a comparatively heavier atmosphere should be only regarded on an orientative basis.
Characterization of fiber orientation in short-fiber composites
Authors: McGee S. H. , McCullough R. L.
Published: February 2003

A method for measuring intermediate states of fiber orientation in short-fiber composites is described. The technique is based on the observation that a representative fiber distribution, for example, the negative of a photomicrograph from a specimen, resembles a collection of diffraction apertures. Diffraction masks for a Fraunhofer diffractometer made from the representative fiber distributions produce diffraction patterns characteristic of the state of orientation. Analyses are presented which relate the features of the diffraction pattern to (i) the orientation distribution, (ii) shape, and (iii) aspect ratio of the fibers. The results from these analyses are in good agreement with experimental diffraction patterns from masks made from simulated fiber distribution patterns.
Compact coaxially excited high energy density KrF laser
Authors: Peters P. J. M. , Bastiaens H. M. J. , Witteman W. J.
Published: February 2003

A coaxial electron beam generator is described operating without a pulse-shortening line. It delivers pumping pulses with a length ranging from 150 up to 500 ns (FWHM). For a laser volume of 0.6 ℓ, a pulse duration of 250 ns and a current density of about 50 A/cm2, a maximum output of 13 J is obtained. The present experiments show that this relatively high current regime is also applicable to long pulses.
Influence of a modulated bias field on dynamic conversion in a rotating gradient experiment
Authors: Nyenhuis J. A. , Friedlaender F. J. , Matsumoto S.
Published: February 2003

In the rotating gradient experiment, a magnetic bubble is in steady state circular motion. The modulation of the dc bias field by a small sinusoidal component, the tickle field, has been found effective in reducing the static coercivity, resulting in stable bubble motion. In this study, the influence of the tickle field on Bloch curve punch-through velocity is investigated. A bubble is circulated both in the presence and absence of the tickle field. For low amplitude tickle fields, Hzt≤0.25 Oe, the translational velocity at which punch-through occurs, ≂3.5 m/s, is the same both in the presence and absence of the tickle field. However, the minimum velocity at which a bubble can be propagated is lower in the presence of the tickle field. For larger Hzt, the punch-through velocity is reduced, with the extent of the reduction depending on the tickle field frequency. The amplitude and frequency of the tickle field affect the apparent dynamic coercivity.
Colloidal crystals in magnetic fluid
Authors: Skjeltorp A. T.
Published: February 2003

Monodispersed polystyrene spheres with diameters in the μm range are mixed with magnetic fluid and confined to thin layers between two glass plates. In an external magnetic field H, polarization of the magnetic fluid produces an apparent magnetic moment Mv associated with each sphere due to the displaced volume V. For low fields, Mv=−VχeffH, where χeff is the effective volume susceptibility of the fluid. For fields parallel to the layer, there is an apparent attractive dipolar interaction between the spheres producing long chains. By applying fields normal to the layer, the spheres behave as repulsive dipoles forming triangular lattices. This offers a novel model system for studies of phase transition phenomena. The direct visual observation of the collective behavior of such spheres will be presented.
Particle capture by an assemblage of spheres in high-gradient magnetic separation
Authors: Moyer C. , Natenapit M. , Arajs Sigurds
Published: February 2003

We present a theory for the capture of magnetic particles by a bed of spheres in high-gradient magnetic separation. The inviscid approximation to fluid flow is used in conjunction with an effective medium treatment to obtain the fluid velocity profile near a representative collector sphere in the assemblage. A similar idea is used to model the magnetic field, thus taking into account the effects of neighboring spheres. Results are reported for the capture of both paramagnetic and diamagnetic particulates by a filter operating either in the longitudinal or transverse design mode.
Magnetic-field analysis of ferrofluidic seals for optimum design
Authors: Sarma Mulukutla S. , Stahl P. , Ward A.
Published: February 2003

Ferrofluidic devices have found applications in laser systems, high-vacuum equipment, computers, loudspeakers, inertia dampers, and motors. With the technique of magnetic-fluid sealing, one is called upon to produce custom solutions for complex and diverse seal problems, many of which may be characterized by very hostile environments, wide temperature ranges, and intense radioactive conditions. In designing a magnetic circuit for a magnetic-liquid seal, a number of factors, such as the size of the available envelope, pressure differential across the seal, chemical compatibility with various environments, and proper selection of permanent and soft magnetic materials need to be considered for achieving the most cost-effective solution while meeting the entire range of requirements for any specific application. In order to evaluate flux leakage and fringing while accounting for nonlinear characteristics of magnetic materials, it becomes necessary to resort to numerical techniques to determine the effect caused by varying the significant parameters and to achieve an optimized design for the device. This paper presents modeling techniques for simulating ferrofluidic seals, and methods to deal with various geometries including inherent symmetry. By numerically analyzing the model, detailed flux distribution plots have been obtained by means of a computer.
Magnetic sensors using Fe-Cr-Ni alloys with square hysteresis loops
Authors: Jin S. , van Dover R. B. , Sherwood R. C. , Tiefel T. H.
Published: February 2003

Voltage-generating magnetic sensors using new square-loop Fe-Cr-Ni magnetic alloy wires are described. Typical magnetic properties of the sensor wire are Br ∼15 kG, Br/Bs ∼0.99, and Hc ∼2–30 Oe. These alloys are corrosion resistant, easy to manufacture into desired wire shape and sensor geometry, and are of low material and processing cost. One exemplary sensor consists of an Fe-20%Cr-4%Ni alloy wire of 0.1–0.5 mm in diameter, 3.7 cm in length, and a sense coil of 1000–2000 turns wound around the alloy wire. With an external ac drive field of 20–200 Oe at various frequencies, voltage pulses with a peak amplitude in excess of 30 V are generated. This sensor may be used as a proximity/displacement sensor, current sensor, rotation/frequency sensor, and other triggering, switching, and security devices.
Uniformity of amorphous GdTbFe films sputter-deposited on rotating substrates
Authors: Taki K. , Mizutani S.
Published: February 2003

Spacial uniformity has been investigated for ternary GdTbFe alloy films as magneto-optical memory media. These amorphous GdTbFe films have been sputter deposited on the outer half of rotating disks 5 in. in diameter, through a mask with a fan-shaped aperture. The circumferential variation of film thickness is less than 10% and that of coercive force is 5% over the recording area. Radial uniformity is affected by the shape of the mask aperture and the constitution of the composit target.
Propagation of intermediate frequency waves in a bounded magnetoplasma
Authors: Das S. K. , Basu J.
Published: February 2003

The paper presents a study of the propagation of intermediate frequency waves in a plasma column magnetized axially and enclosed in a conducting cylinder. The general dispersion relation for the waves, obtained by the dynamic method, is found to reduce to four distinct equations associated with different forms of the field components. The ω-β plane is divided into several regions of four types so that within each region only one of the above four equations would apply. Dispersion characteristics are obtained for all possible types of intermediate frequency modes in a hydrogen plasma for a typical set of ωce/ωpe and aωpe/c, where ωce is the electron cyclotron frequency, ωpe is the electron plasma frequency, a is the plasma radius, and c is the velocity of light in free space. It is discussed how the dispersion characteristics of the different modes would change with variations in the plasma parameters. The investigations show that, contrary to the predictions of the usual quasistatic approximation, propagation of all intermediate frequency modes is possible at frequencies below the lower hybrid frequency ωlh. Moreover, the I−n1 modes with n≠0 and the superscript indicating the polarization form a special category of modes in the sense that they have a resonance at the ion cyclotron frequency ωci and that their propagation below the frequency ωlh is confined to the domain 0<ω<ωci. In the case of all other modes the phase coefficient β increases gradually to a finite value as ω increases from its cutoff value to ωlh ; this value of β lies within two specified limits, β1 and β2 ( β2>β1), which are functions of ωpe, ωce, and ωci. The dispersion characteristic of each of these modes has a sharp discontinuity at ω=ωlh. If ω is increased beyond ωlh, the characteristic of the I01 mode starts off from the point (ωlh,0), while the corresponding point for all other modes is given by (ωlh, β1) . However, all the modes have a resonance at ωpe(ωpe<ωce). It is interesting to note that if the mode number is increased or the plasma radius is reduced, keeping the other parameters fixed, the phase coefficient β at any given frequency increases in the frequency domain ωlh<ω<ωpe, while in the domain 0<ω<ωlh it falls until it becomes zero. Finally, it is shown that there is considerable discrepancy between the results given by the quasistatic approximation and those by the dynamic analysis even in the most favorable case of the I01 mode in the frequency domain ωlh<ω<ωpe if the plasma radius a is relatively large, compared to c/ωpe.
Ion dynamics of rf plasmas and plasma sheaths: A time-resolved spectroscopic study
Authors: Gottscho Richard A. , Burton Randolph H. , Flamm Daniel L. , Donnelly Vincent M. , Davis Glenn P.
Published: February 2003

A new plasma diagnostic technique, time-resolved laser-induced fluorescence (TRLIF) spectroscopy, has been developed to monitor ion dynamics in rf glow discharges. Time-dependent ion concentrations are measured by pulsing a dye laser synchronously with the applied rf potential and then detecting laser-induced fluorescence. In this initial work, Cl2/N2 plasmas have been investigated. In the electrode sheaths, the ion response to the applied potential was measured directly. This response governs ion transport to microelectronic device surfaces in plasma etching and deposition. At frequencies below the ion plasma frequency (∼1 MHz), we found that the electrode sheaths expand and contract with period f−1. The sheath front travels at a speed which depends linearly upon both frequency and sheath thickness, but the sheath expansion begins only after a critical voltage is applied. Characterization of the sheath in terms of its thickness, expansion speed, and critical expansion voltage promises to be a useful means by which ion transport can be modeled. In the discharge center, TRLIF was used to measure ground-state ionic lifetimes, which are essential input for kinetic models of plasma reactors. In pure N2 discharges the N+2 loss rate increases linearly with pressure but the loss mechanism is not clear. In N2/Cl2 plasma mixtures, N+2 rapidly charge exchanges with Cl2 (k≥6×106 sec−1 Torr−1) to form Cl+2 .
Measurement of electron loss rates in high-pressure mercury
Authors: Moody S. E. , Center R. E.
Published: February 2003

The rates of electron decay in high-pressure mercury/helium discharges have been measured using a novel two-photon ionization technique. The rate coefficient of electron loss in this system was found to be well characterized by a two-body rate coefficient of kd=1.05(±0.25)×10−8 cm3 sec−1, assuming dissociative electron-ion recombination. The electron temperature during these measurements is calculated to be 0.4(±0.1) eV. We also report a free-bound optical absorption coefficient at 222 nm of σ̂A=(2.0±0.5)×10−39 cm5.
Dielectric results of polymeric glasses formed under hydrostatic pressure: Is the densified sample closer to thermodynamic equilibrium?
Authors: Destruel P. , Ai Bui , Hoang-The-Giam
Published: February 2003

The energy state of densified polymeric glasses is examined by using the Lennard–Jones model. We question the proposal that densified glasses are closer to equilibrium than glasses formed at the same cooling rate at atmospheric pressure. The origin of an internal stress quenched into the sample during densification treatment is shown. Some dielectric results on polyethylene terephthalate, polyvinyl chloride, and polystyrene are discussed in terms of the free volume decrease or the quenched energy. Our conclusion is that the densification treatment induces two concurrent phenomena: (1) a decrease of fractional free volume, which is preponderant on the energy state of the material when the densification pressure is small; (2) an internal stress which increases the internal energy and develops quickly for high pressures.
Space-charge-Cerenkov and cyclotron-Cerenkov instabilities in an electron-beam dielectric system
Authors: Case William B. , Kaplan Robert D. , Golub John E. , Walsh John E.
Published: February 2003

A relativistic electron beam propagating along a constant magnetic field has four normal modes: the slow and fast space charge and the slow and fast cyclotron modes. When propagating through a dielectric where the beam velocity is greater than the velocity of light in the dielectric, the slow modes may become unstable. We call these the space-charge-Cerenkov and cyclotron-Cerenkov instabilities. In this paper we use the cold fluid model in the small signal limit to obtain a general dispersion relation for propagation at an arbitrary direction with respect to the magnetic guide field. This describes both of the above instabilities as special cases. This result is then generalized to include the effects of a thermal spread. Implications for possible application for generation or amplification of microwaves, where the beam passes near the dielectric, are also considered. We conclude that the cyclotron-Cerenkov instability is a strong candidate for the short wavelength microwave regime.
Dynamics of defect creation by ion implantation in thermal SiO2
Authors: Devine R. A. B. , Golanski A.
Published: February 2003

E ′ 1 (bridging oxygen vacancy) defect densities have been measured in thermal SiO2 films implanted with ions having various energies and masses. From a plot of the defect production per unit volume versus energy deposited into elastic processes per unit volume we observe a linear slope yielding one E1 defect per 2000 eV deposited in displacement energy. Comparison with the measured average displacement energy per ion of 4 eV suggests that up to 500 defects of other forms might be created for every E′1. The predictions of a simple model for E1 creation/annihilation are further tested and the magnitude of the microscopic creation and annihilation cross sections found to be of the order of 10−13 cm2 per ion in both cases. The ratio of the creation and annihilation cross sections is found to decrease monotonically with decreasing implant ion mass.