bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR and magnetic susceptibility study of melt spun (Ni0.20Pt0.80)100−xPx metallic glasses
Authors: Hines W. A. , Modzelewski C. U. , Paolino R. N. , Chen H. S.
Published: February 2003

In order to investigate the electronic structure of the melt spun metallic glass system (Ni0.20Pt0.80)100−xPx (23⩽x⩽30), nuclear magnetic resonance (pulse and continuous wave) and magnetic susceptibility measurements have been carried out for temperatures 4.2 °K⩽T⩽295 °K and for magnetic fields H⩽20 kOe. The 31P Knight shift and relaxation rate, as well as the magnetic susceptibility, decrease as the P concentration increases in a manner similar to that observed for (Ni0.50Pd0.50)100−xPx and Ni100−xPx in earlier work where a rigid two-band model was invoked. On the other hand, the 195Pt Knight shift remains essentially unchanged at +0.03%±0.03% for 23⩽x⩽30. These results, along with earlier work on Ni-Pd-P, Ni-Pt-P and Ni-P metallic glass systems, indicate that the transition metal d-states are being filled by a transfer of charge from the metalloid atoms and, furthermore, the d-states associated with Pt are lower in energy than those associated with Pd which, in turn, are lower than those associated with Ni.
Some experimental facts that indicate the elimination of astigmatism in ion beams with separators using crossed electric and magnetic fields
Authors: Quirós Edbertho Leal
Published: February 2003

In the present work two types of crossed field separators are described. The first separator has parallel rectangular magnetic poles and the second has tilted poles. The spectra of equal-energy electrons are compared for each of the separators. The same is done for protons. Indications of astigmatism elimination are observed at the mass focus using the tilted poles configuration for both the electrons and protons.
Geometrical effects on the beamlet optics of a two-stage ion accelerator
Authors: Meixner C. N. , Menon M. M. , Tsai C. C. , Whealton J. H.
Published: February 2003

The effects of geometrical parameters (aspect ratio, aperture size, gaps) and electrical parameters (voltage distribution, beam energy) on single-beamlet profiles are investigated theoretically and experimentally on a two-stage ion accelerator over both a broad range of beam conditions and a wide range of angles (0 to ±11.5°). In general, the intensity distribution is non-Gaussian. Under optimum conditions, divergence angles half-width at half maximum less than 0.5° could be achieved even with large holes (0.9 mm). Shaping the plasma grid reduced the non-Gaussian wings and improved the beam transmission efficiency.
Continuous slowing-down approximation range of 50-keV–100-MeV electrons
Authors: Gupta Subodh Kumar , Gupta Dharmandra Kumar
Published: February 2003

The Wilson theory has been modified for the calculation of the continuous slowing-down approximation (CSDA) range of 50-keV–100-MeV electrons in the absorbers of atomic numbers from 1 to 92 and in some detector materials, minerals, organic compounds, and gaseous compounds. A correction factor which depends on energy as well as on atomic number is evaluated. Values of the CSDA range obtained by the present approach have shown an agreement with reported values within a discrepancy of 6–7%. An attempt has also been made to correlate the CSDA range with the available experimentally measured projected range. Calculated projected range and experimentally measured projected range are found to be in good agreement.
The minimization of the spherical aberration of symmetrical electrostatic round two-foil lenses
Authors: van der Merwe J. P.
Published: February 2003

The spherical aberration of electrostatic two-foil lenses which are round and symmetrical about the center of the lens, are investigated. Functional relationships between A, a measure of the aberration, and Bn, the coefficients of the Fourier series representing the axial potential distribution, are illustrated graphically, and a local minimum is indicated. This minimum can be used as a starting point for a steepest descent minimization procedure. The two-dimensional hyperfaces of A = A(−1, B3, B5, B7) resemble intersecting valleys, of which the faces are plane near the local minimum. The plane faces and their rectilinear intersections allow analytical methods to increase the efficiency of the search for a minimum. It is also shown that if the axial potential distribution is perturbed by functions of high spatial frequency but small amplitude (1 part in 107), large (for example, nine fold) increases in the spherical aberration can occur.
Transmission and reflection of electromagnetic waves by an obstacle inside a waveguide
Authors: Boström Anders , Olsson Peter
Published: February 2003

We consider the transmission and reflection of electromagnetic waves by an obstacle inside a waveguide. The method employed is an adaptation of the null-field approach (T-matrix method). The geometry is more or less arbitrary, but only for a waveguide with constant cross section can we obtain the scattered field in a not too formal way. For a circular cross section we derive comparatively explicit expressions for the transmission and reflection coefficients of the obstacle, and we give numerical results for spherical and spheroidal obstacles in rotationally symmetric geometries. As an important part of the theory, we have derived some apparently new transformations between the cylindrical and spherical vector waves and also expansions of the free-space Green’s dyadic in cylindrical vector waves.
Sheath expansion of plane probe by ion-beam reflection
Authors: Nakamura Y. , Nomura Y. , Stenzel R. L.
Published: February 2003

The mechanism of the appearance of a knee on the voltage-current curve of a plane Langmuir probe with an incident ion beam is investigated experimentally. The two-dimensional shape of the sheath formed in front of the probe is measured by an emissive probe. The knee is found to be due to the enhanced expansion of an electron sheath by beam reflection, which increases the effective area of the probe. A potential profile similar to a double layer is formed in front of the probe. A weak axial magnetic field, which reduces a radial electron flow and which makes inverted V-shaped two-dimensional potential contours, quenches the knee.
A new experimental approach for studying the gain broadening mechanism in semiconductor lasers
Authors: Kawaguchi H.
Published: February 2003

The gain broadening mechanism in semiconductor lasers has not been clearly understood. This paper reports a new experimental approach for studying this mechanism. In this approach, the intensity of TE oscillating mode is reduced by a Glan-Thomson prism, and the amplified spontaneous emission of TM mode is spectrally resolved for InGaAsP/InP lasers. The gain broadening mechanism is considered by the measured intensity of transmitted power for constructive interference of TM mode. It is concluded that the homogeneous gain broadening mechanism is by far dominant in InGaAsP/InP lasers with undoped active region.
Depolarization of the scattered light on internal reflection from surface acoustic waves on fused quartz. I. Theory
Authors: Lee J. , Zucker J.
Published: February 2003

The theory of light scattering on internal reflection from surface acoustic waves (SAW’s) for the geometry where the incident plane is perpendicular to the SAW propagation direction is described. The surface corrugation and the acoustically induced optical polarized fields are calculated and the appropriate polarization driven wave equation is solved. The scattering of both s- and p-polarized incident light is discussed. In this theory, we predict that the intensity of light on internal reflection from SAW on fused quartz is very strong near the grazing angles for both s- and p-polarizations of the incident light and the scattering light is depolarized. Furthermore, we predict that the scattered light is left elliptically polarized if the incident light is s-polarized and right elliptically polarized if the incident light is p-polarized. A simple physical model is proposed to explain the depolarization effect.
Thermal properties of a solid-state laser crystal LiNdP4O12
Authors: Nakano Jun’ichi
Published: February 2003

The thermal expansion coefficient and the thermal coefficient of refactive index of a stoichiometric laser crystal LiNdP4012 have been measured from room temperature to 250 °C. The thermal coefficient of refractive index of the crystal is negative and its average value over three crystallographic axes is about −2×10−6 deg. The diffusivity and heat capacity of the crystal have been measured by laser flash method from room temperature to 300 °C. Using this information, thermal conductivity of the crystal has been calculated. The largest thermal conductivity of the crystal was 3.3×10−2 J/cm s deg along crystallographic b axis. The temperature distribution observed in a 300-mm-thick crystal plate irradiated by Ar laser light is explained by the thermal conductivity obtained through these experiments.
Pressure and electron temperature dependence of H− density in a hydrogen plasma
Authors: Bacal M. , Bruneteau A. M. , Graham W. G. , Hamilton G. W. , Nachman M.
Published: February 2003

The density of negative ions in a low-pressure hydrogen plasma has been investigated as a function of neutral gas pressure, plasma density, and electron temperature. The comparison of the experimental data, obtained by the photodetachment technique, with theoretical results derived from computed reaction rates, seems to indicate that hydrogen negative-ion production occurs mainly through the process of electron attachment on vibrationally excited hydrogen molecules.
Spectroscopic diagnostics of CF4-O2 plasmas during Si and SiO2 etching processes
Authors: d’Agostino Riccardo , Cramarossa Francesco , De Benedictis Santolo , Ferraro Giovanni
Published: February 2003

The emission intensities in the range of 2000–8000 Å of CF, CF2, O, F, CO, CO+, and CO2 produced in CF4/O2 radio-frequency discharges, operated at 1 Torr of pressure and 50 W of power input, have been used to follow the etching process of Si and SiO2, as a function of the CF4/O2 feed composition. The addition of small amounts of nitrogen or argon to the plasma mixtures has permitted the determination of the effect of the oxygen addition to the gas feed on the electron densities of the plasma for a wide range of electron energies. The relative concentration profiles of F and O, as well as of CO and CO2, have been determined with this technique, as a function of the oxygen content in the feed. The important role played by atomic F as active etchant for both Si and SiO2 substrates has been confirmed.
Thermal properties and heat flow in the laser addressed liquid-crystal display
Authors: Armitage David
Published: February 2003

The heat capacity and thermal conductivity coefficients, describing heat flow in the laser thermally addressed liquid-crystal device, have been measured or derived from literature data. Analytic approximations to the heat and temperature distributions are presented. The significance of heat loss in the substrate and absorber are examined.
The connection between light output of light-emitting diodes and their rise and fall times
Authors: Zaeschmar G.
Published: February 2003

Empirical observations on many light-emitting diodes demonstrate a linear relation between light output (degradation) and their rise and fall times. Using a simple two-path model, the phenomenon can be explained theoretically. As a consequence, the radiative and nonradiative recombination times can be expressed in terms of measurable quantitites. Experimental examples are given.
Normal-state resistivity of i
n s
i
t
u–formed ultrafine filamentary Cu-Nb composites
Authors: Karasek Keith R. , Bevk J.
Published: February 2003

Normal-state electrical resistivity has been studied in Cu-Nb composites containing 7.5, 10.0, and 15.0 vol% niobium filaments formed by an in situ process. The resistivity of the as-drawn and annealed composite wires was measured at temperatures between 300 and 825 K and just above the superconducting transition (∼9 K). The electron scattering from dislocations and interfaces was particularly pronounced in composites with submicron filaments and rapidly increased when the filament thickness decreased to a few hundred angstroms. The magnitude of the boundary scattering contribution in the smallest wires (25 mm in diameter) was found to be comparable to the predicted surface scattering in homogeneous copper wires of only 100 nm in diameter. In contrast to the bulk materials, dislocation scattering in highly reduced in situ composites can be the dominant scattering mechanism up to at least 300 K. These results imply a maximum dislocation density of about 1013 cm/cm3. The experimental findings are compared to theoretical predictions of electron scattering from one- and two-dimensional defects and correlated to the observed mechanical behavior.
Dependence of electron mobility on spatial separation of electrons and donors in AlxGa1−xAs/GaAs heterostructures
Authors: Drummond T. J. , Morkoç H. , Cho A. Y.
Published: February 2003

Single-period modulation doped A1xGa1−x As/GaAs heterojunctions have been prepared by molecular beam epitaxy (MBE). Heterojunctions with a Si-doped A1xGa1−x As layer grown on an unintentionally doped GaAs layer have exhibited enhanced mobility at 78 ° and 300 °K. The A1xGa1−x As, grown with x = 0.25 or x = 0.33, was doped to a level ND?3×1017 cm−3 resulting in a sheet-charge density of about 8×1011 cm−2. Maximum mobilities of 74 200 cm2/V s at 78 °K and 6930 cm2/V s at 300 °K were observed in different structures. This represents an improvement of more than a factor of 2 over the best previously reported results at 78 °K. These structures, if used for normally off and/or psuedonormally off FET channel layers in high-speed integrated circuits, can provide improved performance. These extremely high mobilities can lead to a power delay product improvement of about a factor of 2 at room temperature and a factor of more than 12 at liquid-nitrogen temperature as compared to conventional structures. This increase in mobility is the result of the virtual elimination of electron scattering by spacially separating the donors from the heterojunction interface.
Josephson tunnel junction time-dependence calculations based on the Bardeen-Cooper-Schrieffer theory
Authors: Gayley Robert I.
Published: February 2003

The feasibility and the importance of using the full BCS theory for numerical calculations of the time-dependent behavior of a Josephson tunnel junction is examined by investigating switching from the zero to the finite voltage state. The calculation can be done, but only if the RC time constant is not too long. The results differ appreciably from those obtained with the crude but frequently used ’’resistively shunted junction’’ model. Artifical rounding of the energy-gap edge, in the form of ’’memory reduction,’’ is introduced and shown to reduce computational difficulties appreciably without significantly altering any results. This should make many more situations amenable to accurate digital simulation.
The effects of oxygen on superconducting A15 NbSi
Authors: Feldman R. D. , Hammond R. H.
Published: February 2003

The addition of oxygen during electron-beam evaporation of NbSi enhances the stability of the A15 phase and increases the onset of the superconducting transition from 6 to 8.3 K. Phase diagrams have been prepared for films evaporated with and without oxygen. Films of up to 600-Å thickness have also been studied to learn the effects of oxygen on the early stages of film growth. A comparison of the role of oxygen in NbSi with the roles suggested for oxygen in NbGe is made, and additional models for the role of oxygen are presented.
Magnetic properties of some rare-earth magnesium compounds RMg2
Authors: Loidl A. , Knorr K. , Müllner M. , Buschow K. H. J.
Published: February 2003

The magnetic properties of the compounds PrMg2, NdMg2, DyMg2, and ErMg2 were studied by means of neutron diffraction at various temperatures. All these compounds give rise to ferromagnetic ordering. The absolute values of the magnetic moments in the magnetically ordered state are lower than the free-ion values. Inelastic neutron scattering at several temperatures was studied in PrMg2 and NdMg2. Analysis of the scattering data in conjunction with the results of specific-heat and magnetization measurements shows that PrMg2 is an induced-moment system (G3 ground state), where quadrupolar effects carry a large weight in determining the magnetic properties. The values found for the crystal-field parameters in PrMg2 (x = 0.671 and W = −0.345) are consistent with the results obtained with CeMg2 and NdMg2 (A4≳0, A6<0).
Transverse closure domains and the behavior of the magnetization in grain-oriented polycrystalline magnetic sheets
Authors: Allia P. , Celasco M. , Ferro A. , Masoero A. , Stepanescu A.
Published: February 2003

A theory is proposed to explain the behavior of the initial magnetization curves I(H) of polycrystalline grain-oriented ferromagnetic materials by taking into account the properties of transverse closure domains lowering the magnetostatic energy of samples. The effects due to the collapse of these domain structures with increasing H are shown to be of relevance in determining the actual shape of the I(H) curve in the intermediate field region 5×102 A/m≲H≲104 A/m, both in the absence and in the presence of applied stresses. The results of measurements of I(H) in Fe-Si sheets with high texture perfections are reported. These results are in very good agreement with the present theory. Finally, a new method is proposed to obtain information on either the grains dispersion in grain-oriented materials or on the volume of the transverse domains by performing only magnetic measurements.
Cathodoluminescence of InP
Authors: Gatos C. H. , Vaughan J. J. , Lagowski J. , Gatos H. C.
Published: February 2003

Cathodoluminescence studies were carried out on p-type InP having carrier concentrations ranging from 7.2×1016 to 7.4×1018 cm3 in the temperature range of 80–580 K. It was found that low-temperature spectra exhibited peaks at 1.41 and 1.38 eV. These peaks were attributed to band-to-band and band-acceptor transitions, respectively. The dependence of the band-to-band peak on temperature was used to extend knowledge of the temperature dependence of the energy gap of InP to 550 K. It was shown that the half-width of the cathodoluminescence peak can be used for the determination of carrier concentration and carrier-concentration inhomogeneities in the material. The variations of the cathodoluminescence peak height with temperature indicated the possibility of Auger recombination for high carrier concentrations (7.4×1018 cm3) at temperatures above 450 K.
Enhancement of third-order susceptibility due to electronic transitions in rare-earth ions
Authors: Shand M. L.
Published: February 2003

Three-wave mixing experiments demonstrate resonance enhancement of the third-order susceptibility due to electronic transitions in rare-earth ions. The position, width, and strength of eight resonances in the 2100–2500-cm−1 range in terbium aluminum garnet (TbAlG) are determined. These resonances are due to 7F5→7F6 intermanifold transitions of terbium. In addition, the nonresonant susceptibility has been measured for TbAlG :  xNRxxxx = (12.4±2.5)×10−14 m3/J and xNRxyyx = (3.8±0.8)×10−14 m3/J.
Secondary ion emission from binary alloy systems. Part I: O+2 bombardment
Authors: Yu Ming L. , Reuter Wilhad
Published: February 2003

We have studied the emission of positive atomic ions from five binary alloys: Cr-Ni, Fe-Ni, Cu-Ni, Pd-Ni, and Ag-Pd, all under O+ 2 bombardment. Significant enhancement and suppression of ionization probabilities due to the presence of the second alloy component were observed. The alloying effect follows two general rules. The first rule states that for an alloy A-B, where A forms a stronger oxide bond than B, the presence of A enhances the emission of B+, while the presence of B suppresses the emission of A+. The second rule states that the presence of A sharpens the energy distribution of B+, while the presence of B broadens the energy distribution of A+. X-ray photoemission studies of the O+ 2 bombarded alloy surfaces connect the general rules with the enhanced oxidation of B and the suppressed oxidation of A in the alloys. All the cases that deviate from the rules originate from insufficient oxygen for oxidation resulting from the self-limiting nature of oxidation by O+ 2 bombardment.
Secondary ion emission from binary alloy systems. Part II: Ar1 bombardment with O2 absorption
Authors: Yu Ming L. , Reuter Wilhad
Published: February 2003

The emission of positive atomic ions from Cu-Ni, Pd-Ni, and Ag-Pd alloys was studied under Ar+ bombardment with saturated O2 adsoprtion. In line with other published data on Cr-Fe, Cr-Ni, and Fe-Ni alloys, these studies all agree well with two general rules porposed previously for O+2 bombardment. The first rule states that for an alloy A-B, where A forms a stronger oxide bond than B, the presence of A enhances the emission of B+, and the presence of B suppresses the emission of A+. The second rule states that the presence of A sharpens the energy distribution of B+ while the presence of B broadens the energy distribution of A+. The experimental data fit the rules with better consistency than for the case of O+2 bombardment except in cases of low oxygen sticking coefficients on the alloy surfaces. The success of the general rules is linked with the enhanced oxidation of B and the suppressed oxidation of A in the alloy. X-ray photoemission studies of the oxidized surfces support this explanation. Further evidence of an energy-dependent ionization probability of Ni+ from pure Ni provides a consistent explanation of the second general rule.
Performance and characterization of GaAs-(GaAl)As double heterojunction lasers grown by metalorganic chemical vapor deposition
Authors: Whiteaway J. E. A. , Thrush E. J.
Published: February 2003

Double heterojunction GaAs-(GaAl)As lasers have been fabricated from material grown by metalorganic chemical vapor deposition (MOCVD) with active layer thicknesses between 0.08 and 0.33 mm. They had threshold current densities as low as or lower than the best liquid phase epitaxy (LPE) devices. The lowest measured threshold current density was 560 A cm−2. The measured gain-current density characteristic of MOCVD-grown GaAs was comparable to that of our best LPE-grown GaAs. The dimensional uniformity of multilayer structures over a growth area of 17 cm2 is typically 10%. Further cw reliability measurements on oxide-insulated stripe geometry lasers indicate no fundamental obstacles to obtaining room-temperature degradation rates as low as 0.8% per 1000 h over a 6000-h period.
Efficient narrowband electron beam pumped KrF laser for pulse-compression studies
Authors: Swingle J. C. , Schlitt L. G. , Rapoport W. R. , Goldhar J. , Ewing J. J.
Published: February 2003

A 25-J, 50-ns laser pumped by opposed electron beams is described. Experiments with this device demonstrated a 9% intrinsic laser efficiency at power deposition rates of about 1 MW/cm3. Parasitic control and narrowband output required for Raman-compression experiments were demonstrated by injection locking the laser. Experiments showing an angle-encoded extraction of energy from the medium (pulse stacking) with three pulses using a high-gain three-pass amplifier configuration are also described. The device utilizes triggering schemes of very low jitter suitable for synchronization to other components for optical pulse-compression experiments.
A two-Gaussian model for stabilized filament formation in nonlinear media
Authors: Abbi S. C. , Kothari Nitin C.
Published: February 2003

We describe the effects of energy conservation on the growth of a Gaussian perturbation superimposed on a Gaussian profile laser beam. Using a simple two-step energy conservation criterion, we obtain a relationship between the self-focal distance zff for the smooth Gaussian profile laser beam and the distance Dt at which the growth in the Gaussian spike terminates. For a very intense laser beam, with appreciable amplitude of the perturbation, the growth of the perturbation is studied using a continuous energy-conservation criterion. The results explain the stabilization of intensity in the perturbation at a certain distance inside the medium. Our model explains formation of bright stabilized filaments and gives reasonable estimates for the distance of the first appearance of filaments.
Magnetic interaction between ion-implanted liquid phase epitaxially grown magnetic garnet films and patterned thin metallic films
Authors: Gill H. S.
Published: February 2003

Our investigations on composites of ion-implanted liquid phase epitaxially (LPE) grown magnetic bubble garnets and patterned thin metallic films have shown that bubble-collapse field modulation occurs owing to metallization for ion-implanted LPE films. No such interaction was observed for un-implanted LPE films. The collapse field change due to metallization is a strong function of the ion dosage and ion energy. Furthermore, we found that this interaction is proportional to the flux keeper effect (or to the loss of collapse field under the action of an in-plane magnetic dc field). This interaction can be minimized by overdamaging the ion-implanted layer (converting the layer to an amorphous form), or can be eliminated by avoiding the ion-implanted magnetically soft layer with planar anisotropy by choosing an alternative means of hard bubble suppression.
Sample-gas thermal contact resistance and the photoacoustic signal generation
Authors: Lima C. A. S. , Miranda L. C. M. , Santos R.
Published: February 2003

By invoking long standing results from studies on heat transfer across a two-media interface, the claim for the non-negligeable character of the effects of the solid-gas thermal contact resistance on the photoacoustic signals is amply discussed. Existing experimental evidences are presented which result in strong support for such a claim.
Burstein-Moss shift in heavily In-doped evaporated CdS layers
Authors: Jäger H. , Seipp E.
Published: February 2003

CdS layers on glass substrates show different colors from deep to light yellow depending on the evaporation conditions. We found that the shorter the absorption edge wavelength, the higher the carrier density in the layer. The correlation shows typical features of the Burstein-Moss shift well known from narrow-gap III-V compound semiconductors.
Surface rippling induced in thin films by a scanning laser
Authors: Cline Harvey E.
Published: February 2003

The variation in the thickness of thin films produced by a scanning laser was calculated and compared with experiment. Fluid flow in the molten-metal film was induced by surface-tension gradients generated by the local heating of the laser beam. The surface of the film became rippled, limited by capillary effects and the constraint of the solid substrate. A Nd:YAG scanning laser was used to melt and alloy 2-μm-thick films consisting of Pb and Sn layers. The shape of the thickness profile measured with a two-beam interferometer agreed with the calculated shape. Measurements of the surface composition indicated that alloying occured and influenced the magnitude of the surface relief. The surface topography of laser alloying and recrystallizing thin films as discussed in the recent literature, is reviewed on terms of the surface-tension-gradient mechanism.
Influence of charge carrier scattering on the exact form of the Hall curve
Authors: Rijks H. J. , Giling L. J. , Bloem J.
Published: February 2003

Hall measurements on high-Ohmic n-type float zone and Czochralski silicon which had received various heat treatments have been carried out as a function of temperature. An anomalous decrease in the Hall coefficient upon cooling was observed for all as-grown crystals in case the measurements were performed in low magnetic fields (B=0.5 T). In order to investigate the origin of this behavior, both the influence of oxygen and the possibility of a change in the Hall scattering factor were studied. To this end Hall measurements were performed as a function of magnetic field strength up to B=14 T. From the ratio of the low and high magnetic induction limits of the Hall coefficient the Hall scattering factor r has been obtained. In addition, from the high magnetic induction limit for the Hall coefficient the charge carrier density has been obtained without interference from scattering effects. On the basis of these results the anomalous transport phenomena reported in the literature could be attributed to a change in the Hall scattering factor.
cw laser annealing of hydrogenated amorphous silicon obtained by rf sputtering
Authors: Thomas J.P. , Fallavier M. , Affolter K. , Lüthy W. , Dupuy M.
Published: February 2003

Hydrogenated amorphous silicon obtained by rf sputtering has been annealed using cw lasers (Ar or Kr ion). The annealed films have been microanalyzed for quantitative profiling of hydrogen and argon. TEM analysis was used for structure determination. The release of hydrogen and argon as well as the grain size of the polycrystalline material obtained are related to the deposited laser energy. Comparison with other production methods of such material from the amorphous state is discussed.
Decomposition and product formation in CF4-O2 plasma etching silicon in the afterglow
Authors: Beenakker C. I. M. , van Dommelen J. H. J. , van de Poll R. P. J.
Published: February 2003

The decomposition of CF4 and of O2 and the formation of the plasma product molecules CO2 and COF2 have been determined by mass spectrometry for a 2450-MHz CF4 plasma to which variable amounts of oxygen were added. In addition, the SiF4 production resulting from the interaction of the plasma effluent with a silicon wafer was monitored. It was found that up to its maximum the decomposition of CF4 is twice the amount of decomposed oxygen. This result, combined with those of experiments in which CO2 was used instead of oxygen, and experiments in which CF4 and O2 were discharged separately, leads to the conclusion that after decomposition of O2 to O atoms and of CF4 to CF3 fragments and F atoms, one oxygen atom reacts with one short-lived CF3 fragment to form the primary products COF2 and atomic fluorine. At higher oxygen concentrations, excess O(1D) atoms are formed. These atoms rapidly react with the COF2 to form CO2 and F2. Consequently, the COF2 production strongly decreases with the simultaneous formation of carbon dioxide. At these higher oxygen concentrations it is also found that excess molecular oxygen reacts with the atomic fluorine produced, eventually forming molecular fluorine. As a result, the production of SiF4 decreases much more strongly than expected on the basis of the decomposition of CF4.
Channeling of implanted 75As+ through Mo films
Authors: Kudoh O. , Murao Y. , Kobayashi K.
Published: February 2003

The negative shifts of the threshold voltages of 75As+-implanted Mo-gate metal-oxide semiconductor (MOS) transistors were observed under some fabrication conditions of high-energy or high-dose 75As+ implantation, or thin-Mo-film deposition. These phenomena are attributed to 75As atoms entering Si through Mo-film and -gate oxide by measuring C-V characteristics and observing the stain-etched cross sections of the samples directly. The present threshold voltage shifts can be almost perfectly suppressed by covering Mo-gate electrodes with 2000-Å plasma-CVD silicon-nitride films during 75As+ implantation.
Comments on ’’Nuclear-pumped cw lasing of the 3He-Ne system’’
Authors: Prelas M. A. , Schlapper G. A.
Published: February 2003

The recent report of cw nuclear-pumped lasing and of the measurement of gain on the 3s2-2p4 transition of Ne in mixtures of 3He-Ne by Carter, Rowe, and Schneider has some fundamental problems which lead one to conclude that the oscillation observed was not from the 6328-Å line of Ne. Specifically, calculations using a very optimistic model of the He-Ne laser at the reported conditions do not support the conclusions of Carter et al. The maximum possible small signal gain for the idealized system, which is the upper limit on this quantity, is an order of magnitude smaller that that reported. Additionally, due to the unusually high single-pass cavity losses reported (≳50%), the idealized system could not achieve oscillation.
Studies of elastic constants of oriented poly(ethylene terephthalate) films using Brillouin scattering
Authors: Cavanaugh David B. , Wang C. H.
Published: February 2003

Brillouin scattering is used to study the elastic behavior of oriented poly(ethylene terephthalate) films. The elastic constants C11, C13, C33, and C44 are determined by measurements of the quasilongitudinal and quasitransverse hypersonic velocities at different angles in the film. The total orientational parameter is calculated for the three draw ratios from the Brillouin hypersonic velocities and are found to be similar to the orientational parameter in the amorphous phase obtained with a different technique.
Dynamics of electrowetting displays
Authors: Beni G. , Tenan M. A.
Published: February 2003

In this paper we analyze the dynamics of a model electrowetting display (EWD) system, derive the operating parameters, and discuss the device performance. To discuss the problem we generalize the Washburn-Yarnold treatment for the motion of a liquid slug in a capillary tube. It is shown that EWD’s have both memory and voltage threshold, and thus intrinsic matrix addressability. These properties are intimately related to the frictional surface tension forces developed between the metal and the electrolyte. Finally we present a model voltage-driving scheme for matrix-addressable EWD’s.
Statistical distribution analysis of rubber fatigue data
Authors: DeRudder J. L.
Published: February 2003

A v e r a g e rubber fatigue resistance has previously been related to such factors as elastomer type, cure system, cure temperature, and stress history. This paper extends this treatment to a full statistical analysis of rubber fatigue data. Analyses of laboratory fatigue data are used to predict service life. Particular emphasis is given to the prediction of early tire splice failures, and to adaptations of statistical fatigue analysis for the particular service conditions of the rubber industry.
Use of a theoretical equation of state to interpret time-dependent free volume in polymer glasses
Authors: Curro J. G. , Lagasse R. R. , Simha R.
Published: February 2003

Many physical properties of polymer glasses change spontaneously during isothermal aging by a process commonly modeled as collapse of free volume. The model has not been verified rigorously because free volume cannot be unambiguously measured. In the present investigation we tentatively identify the free-volume fraction with the fraction of empty sites in the equation of state of Simha and Somcynsky. With this theory, volume recovery measurements can be analyzed to yield directly the time-dependent, free-volume fraction. Using this approach, recent volume measurements on poly(methyl methacrylate) are analyzed. The resulting free-volume fractions are then used in the Doolittle equation to predict the shift in stress relaxation curves at 23 °C. These predicted shift factors agree with the experimental measurements of Cizmecioglu et al. In addition, it is shown that previous assumptions concerning temperature dependence of free volume are inconsistent with the theory.
Temperature dependence of broadline NMR spectra of water-soaked, epoxy-graphite composites
Authors: Lawing David , Fornes R. E. , Gilbert R. D. , Memory J. D.
Published: February 2003

Water-soaked, epoxy resin-graphite fiber composites show a waterline in their broadline proton NMR spectrum which indicates a state of intermediate mobility between the solid and free water liquid states. The line is still present at −42 °C, but shows a reversible decrease in amplitude with decreasing temperature. The line is isotropic upon rotation of the fiber axis with respect to the external magnetic field.
Sub-T
g annealing studies of advanced epoxy-matrix graphite- fiber- reinforced composites
Authors: Kong Eric S. W.
Published: February 2003

Selected mechanical properties of symmetrically (±45°) reinforced 16-lamina graphite/epoxy composites have been found to be affected by sub-Tg annealing. Postcured specimens of Thornel 300 graphite/Narmco 5208 epoxy were sub-Tg annealed at 140 °C for ca. 10, 102, 103, 104, and 105 min, with a prior quenching from above Tg. The ultimate tensile strength strain-to-break, and static toughness of the composite materials were found to decrease as a function of sub-Tg annealing time. No weight loss was observed during the sub-Tg annealing. The time-dependent change in properties can be explained on the basis of physical aging which is related to free volume decrease in the non-equilibrium glassy state of network epoxies. The results imply possible changes in composite properties with service time.
Elastic wave scattering by a flaw in an isotropic, homogeneous solid
Authors: Baker George A. , Gammel J. L.
Published: February 2003

In a framework where a flaw is regarded as the spatial variation of the density and the elastic constants of the host medium, we derive a matrix scattering formalism. We introduce a bivariational principle for the scattering amplitude and use it to develop an optimal-type approximation scheme. We consider the implications of reflection-plane symmetry and show that when the incident and scattered waves lie in this plane, certain polarized, scattering amplitudes are zero. We develop a ’’partial-wave’’ expansion for any flaw of spherical symmetry and reduce this scattering problem to a feasible numerical computation.
Power considerations in the operation of a piston fitted inside a cylinder containing a dynamically heated working fluid
Authors: Aizenbud Boris M. , Band Yehuda B.
Published: February 2003

We determine the optimal motion of a piston fitted in a cylinder containing a gas, pumped with a given time-dependent rate of heating and coupled to a heat bath, in order to maximize the power obtained. The dependence of the optimal power, and the corresponding optimal operating time, on the form of the heating function is studied. Furthermore, we determine the maximum work production obtainable from the system for a given specific power output.
Experimental investigations of micellar systems
Authors: Bohidar H. , Chopra S.
Published: February 2003

In this article we report an investigation of micellar systems by photon correlation technique for the first time. The systems investigated are two very commonly occurring Directo dyes (Congored and Benzopurpurine 4B) in aqueous solutions. From these studies, we are able to exploit their aggregation trends at different dye and salt concentrations and to also compare with available data from other conventional techniques used so far. The conventional methods (microdiffusion cells, ultracentrifuge methods, etc.) often produce controversial results unlike the present technique which is consistent, accurate, and very fast.
Electron momentum distribution, velocity space instability, and angular momentum in relativistic large aspect ratio diodes
Authors: Hazak G. , Zarmi Y. , Zinamon Z.
Published: February 2003

The detailed structure of electron momentum distribution in relativistic diodes is studied. It is proven that in most of the diode region the momentum distribution is isotropic in fluid rest frame, with azymuthal temperature which, in general, is much larger than the cathode temperature. A diode model based on these conclusions is presented. The model allows for a continuum of electron trajectories at each point. In various limits the results are reduced to well-known cold fluid model results.
Optical oscillator strengths for the chlorine isoelectronic sequence
Authors: Ganas P. S.
Published: February 2003

An analytic atomic independent particle model potential adjusted to experimental single-particle energy levels is used to generate wave functions for the valence and excited states of Cl, Ar+1, K+2, Ca+3, Sc+4, these wave functions in conjunction with the Born approximation and the LS-coupling scheme, we calculate optical oscillator strengths for excitations from the 1s22s22p63s23p5(2P3/2) ground state. Reasonable agreement is obtained with available experimental and theoretical data.
The picosecond ultrashort cavity dye laser: Giant pulse analogy and active étalon model
Authors: Duncanson John A. , Struve Walter S.
Published: February 2003

The evolution of a tunable dye laser (TDL) pulse in an ultrashort cavity pumped by a monochromatic picosecond light pulse is described using the appropriate laser rate equations. The ultrashort duration of the excitation pulse typically reduces the treatment into one which is directly analogous to the giant pulse model of Wagner and Lengyel, applied previously to Q-switching dynamics in solid-state lasers. The spectral properties of the TDL pulse are calculated using an active étalon model, in which the bandwidth narrowing of the cavity axial modes is governed by the time-dependent gain derived from the giant pulse model. Theoretical conditions are obtained for achieving operating regimes which correspond to extraction of high pump→TDL conversion efficiencies, to the minimization of TDL pulse durations, or to shot-to-shot stabilization of output properties. The feasibility of extracting ∼45% conversion of 531-nm SHG pulses from the mode-locked Nd3+ : glass oscillator using a 54-nm rhodamine 6G cavity is confirmed experimentally.
Assignment of the 7Li2 optically pumped laser transitions pumped by Ar+ and Kr+ laser lines
Authors: Verma K. K. , Stwalley W. C. , Zemke W. T.
Published: February 2003

In an attempt to determine the assignments for the wavelengths observed in the line tunable lithium dimer laser [H. Welling and B. Wellegehausen, Laser Spectroscopy III (Springer-Verlag, New York, 1977), p. 365] pumped by the Kr+ 6471-Å laser, we have examined the corresponding fluorescence spectrum of the 7Li2 molecules. Unlike the Ar+ laser fluorescences which have previously been assigned, the Kr+ laser fluorescence of Li2 has not been previously studied. Here we present the assigned fluorescence spectrum which consists of two series of the A-X system (v′ = 9, J′ = 11, v′ = 12, J′ = 60) along with the line frequencies and their calculated absolute radiative transition probabilities. The optically-pumped laser lines are identified and additional wavelengths are listed which may lase when pumped at 6471 Å or at various Ar+ laser wavelengths.
Helium breakdown by DF laser radiation
Authors: Nichols D. B. , Hall R. B.
Published: February 2003

Thresholds have been measured for the breakdown of helium by laser radiation near 3.8 μm in wavelength. Four-μsec chemical laser pulses were focused to a well-defined spot 100 μm in diameter. Values of the instantaneous irradiance qt and the accumulated fluence et occurring at time of breakdown were observed as a function of helium pressure in the range 0.12–0.99 atm. The measured qt was 2.3 ×1010 W/cm2 at 1 atm, in good agreement with results scaled from other wavelengths.
UV sustained CO laser discharge I. Photoionization studies
Authors: Suhre D. R.
Published: February 2003

The photoionization process for UV-initiated and UV-sustained CO laser operation was investigated by measuring the photoion density produced by a single spark source using charge collection. C2H4 and NO were studied as potential low-temperature additives for enhancing photoion production, both of which photoionized by a single-step process with a conversion efficiency of spark energy into photoionization of about 1%. The photoionization was also found to increase linearly with dissipated spark energy, was independent of the spark circuit parameters, and at constant gas and additive density was also independent of temperature.
Al0.48In0.52 As/Ga0.47In0.53 As/Al0.48In0.52As double-heterostructure lasers grown by molecular-beam epitaxy with lasing wavelength at 1.65 μm
Authors: Tsang W. T.
Published: February 2003

The preparation and operation of lattice-matched Al0.48Ga0.52As/Ga0.47In0.52As/Al0.48In0 .52As double-heterostructure lasers lasing at 1.65 μm grown on InP substrates by molecular-beam epitaxy are described. The present result represents the first current injection semiconductor laser ever fabricated from the Al0.48In0.52As/Ga0.47In0.53As/Al0.48In0 .52As double heterostructure. Broad-area Fabry-Perot laser (0.15-μm-thick Ga0.47In0.53As active layer) with pulsed current threshold density as low as 3.3 kA/cm2 has been obtained at room temperature and operated at heat-sink temperatures as high as 115 °C studied. The threshold-current temperature dependence has a characteristic temperature T0 of 70 °C in the temperature range of 25°–115 °C.
Optical fiber interferometers with [3×3] directional couplers: Analysis
Authors: Sheem Sang K.
Published: February 2003

All-guided wave interferometers using [3×3] directional couplers as beam splitters are analyzed in detail. The characteristics of such interferometers are compared with those of conventional interferometers using [2×2] beam splitters. It is shown that there are advantages in using [3×3] couplers instead of [2×2] couplers in the Mach-Zehnder interferometric sensors and the Sagnac rotation sensors (gyroscopes).
Extremely low-loss glass thin-film optical waveguides utilizing surface coating and laser annealing
Authors: Dutta Subhadra , Jackson Howard E. , Boyd J. T.
Published: February 2003

Application of a surface coating to Corning 7059 glass thin-film optical waveguides has been shown to significantly reduce their scattering loss. Combining the technique of CO2 laser annealing of glass waveguides with surface coating, we measure waveguide loss as low as 0.01 dB/cm. By attributing the decrease in attenuation to elimination of the effects of surface irregularities, we were able to identify surface and bulk contributions to scattering losses in the original waveguide. By making such an identification before and after laser annealing, we confirm that CO2 laser annealing of glass waveguides reduces both surface and bulk contributions to scattering losses.
Linear electro-optic effect in tellurium dioxide
Authors: Ewbank M. D. , Newman P. R.
Published: February 2003

The only non-zero dc electro-optic (or Pockel’s) coefficient in tellurium dioxide was measured at constant stress. The result was rT41 = −0.76 (±0.19)×10−12m/V. The secondary electro-optic effect, due to the converse piezoelectric and photoelastic effects, is approximately twice the observed electro-optic response.
The impedance of the near ballistic electron transport device in n-GaAs
Authors: Lee Johnson , Vassell M. O.
Published: February 2003

The ac impedance of a two-terminal near-ballistic electron device is calculated by solving the equation of motion, Poisson’s equation, and the equation for current density. The influences of diffusion and collision drag are discussed. Our calculations show that this particular device has an equivalent circuit characterized by an antiresonance whose frequency shifts with increasing collision effect away from the plasma frequency towards lower values, and that diffusion and collision effects reduce substantially the magnitude and phase of the impedance. Even so, the impedance appears to be measurable.