bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress anisotropy in opposed anvil high−pressure cells
Authors: Ruoff Arthur L.
Published: February 2003

When materials such as sodium chloride are introduced into a piston−cylinder (or other) chamber it is commonly assumed that the state of stress for small loads is nonhydrostatic; as the load is increased, and the mean normal pressure greatly exceeds the yield stress (at zero pressure), it is commonly assumed that the state of stress approaches hydrostatic pressure. In other words it is assumed that as the mean normal pressure becomes arbitrarily large, the deviatoric stresses become negligible. It is shown in the present paper that this is an erroneous assumption. Specifically it is shown that as the mean normal pressure becomes arbitrarily large, the ratios of the deviatoric stresses to the mean normal pressure approach finite values. The present analysis also shows that as the mean normal pressure is increased, the difference of pressure deduced from interplanar spacing measurements (on a cubic crystal) for planes lying normal to the piston motion to the pressure deduced from interplanar spacing measurements for planes lying parallel to the direction of piston motion, divided by the mean normal pressure, approaches a constant value. Lattice parameter measurements with the incident beam normal to the direction for piston motion underestimate the mean normal pressure, the error decreasing to a constant value as the mean normal pressure is increased. More importantly, this analysis leads to a method of measuring yield stresses as a function of pressure at high pressures using x−ray measurement of lattice spacings of planes of the appropriate orientation.
Influence of AlxGa1−xAs layer thickness on threshold current density and differential quantum efficiency for GaAs−AlxGa1−xAs DH lasers
Authors: Casey H. C. , Panish M. B.
Published: February 2003

Measurements of the threshold current density Jth and differential quantum efficiency ηd havd been made on GaAs−Al0.3Ga0.7As double−heterostructure (DH) lasers to determine the effect of AlxGa1−xAs layer thickness on Jth and ηd. For DH lasers with active layer thicknesses near 0.12 μ, Jth increases and ηd decreases drastically for p−type Al0.3Ga0.7As layers less than ∼0.8 μ in thickness. This effect is also considered for other values of active layer thickness d, and AlAs mole fraction x.
Poole−Frenkel conduction and the neutral trap
Authors: Arnett P. C. , Klein N.
Published: February 2003

The potential φ of a neutral trap may, in approximation, be represented by an inverse power law φ ∝ r−n, where r is the distance and n varies from 1 to ∞. The field lowering of the potential barrier is then proportional to Em. E is the field and m=0.5 for n=1 and m→1 for n→∞. This lowering may explain high−field conduction results in which the logarithm of the current density was found to be proportional to Em.
WKB approximation for optical guide modes in a medium with exponentially varying index
Authors: Conwell Esther M.
Published: February 2003

Although the WKB has been shown to be a good approximation in situations where a medium with exponentially varying index of refraction supports more than one optical mode, it might be expected to be poor near cutoff. There the index difference between the surface and interior that supports guiding has decreased by the factor 1/e at a depth that may be as small as a fraction of a wavelength. We show that, despite this, the WKB does provide a good approximation near cutoff.
Runaway of fast electrons penetrating a thick absorber under the influence of an electric field
Authors: Bowden C. M. , Perkins J. F. , Raiford M. T. , Shatas R. A.
Published: February 2003

In connection with electron−beam−preionized electrical−discharge−pumped gas lasers, we have performed Monte Carlo calculations of transport of fast electrons in an absorber subject to an externally applied electric field which tends to add energy to the fast electrons. It was found that when the magnitude of the field (in suitable units) substantially exceeds the stopping power of the absorber at the incident energy, an appreciable fraction of the fast electrons undergo a net increase of energy which can be quite large for thick absorbers. Results are presented for 0.1 MeV incident energy, an absorber thickness of 0.2 g cm−2, and several values of electric field. For the larger values of applied field, the distribution of energies of emergent electrons tends to bunch toward the maximum possible energy.
Narrow−bandwidth (Al,Ga)As : Si double−heterostructure LED’s
Authors: Lauer R. B. , Zucker J.
Published: February 2003

The spontaneous emission spectrum of AlxGa1−x As−AlyGa1−yAs : Si double−heterostructure (DH) LED’s is reported. LED’s are grown and fabricated which have spontaneous emission spectra with widths at half−maximum as small as 34 nm. This is a substantially smaller value of half−width than previously reported for DH LED’s with Si−doped active layers. The reduction in half−widths is attributed primarily to the reduction in growth temperature of the epitaxial layers.
Experimental properties of injection lasers. VI. Mode powering in narrow−stripe and wide sawed lasers
Authors: Sommers H. S.
Published: February 2003

The modal power distribution is measured at full power for a 10−μm−wide oxide stripe laser and compared with a 100−μm−wide laser with sawed sides prepared from the same (AlGa)As double heterojunction wafer. Simple scaling of the results according to cavity width reveals a striking similarity in their modal power distributions. the critical power per mode describing the lasing nonlinearity is found to be 10 mW and independent of type of mode, of internal structure of cavity, of lateral current confinement, and of facet area.
Experiments on the origin of process−induced recombination centers in silicon
Authors: Sah C. T. , Wang C. T.
Published: February 2003

Densities of recombination centers obtained by the transient capacitance technique in diffused p+n junctions and Al−nSi Schottky barriers are correlated with process variables of more than 70 diffusion and heat−treatment experiments. Results show that the two process−induced donor defect centers reported previously are generated at the strained and disordered silicon surface layers either from high−surface concentration phosphorus or boron diffusion or from mechanical lapping. Chemically polished surfaces appear to act neither as a source nor a sink of these defect centers. The defects are not related to oxygen in the original silicon nor oxygen introduced during oxidation or diffusion. The effects of phosphorus and boron surface concentrations, phosphosilicate surface glass layers, and diffusion temperatures on the concentrations of these two centers are investigated. Nearly constant defect concentration profiles at depth more than 50 μ from the surfaces are observed, suggesting an L−shaped defect concnetration profile in samples with one−sided surface defect source and U−shaped profile for two−sided surface defect sources. These characteristics suggest that the defect centers are vacancies or vacancy complexes formed by vacancies diffused into silicon from the surface sources.
Experimental and theoretical study of energy dissipation profiles of keV electrons in polymethylmethacrylate
Authors: Shimizu R. , Ikuta T. , Everhart T. E. , DeVore W. J.
Published: February 2003

Energy dissipation profiles of keV electron beams in polymethylmethacrylate (PMM) were investigated both in theory and experiment. The results measured using a scanning electron microscope as a source of the electron beam were followed by the Monte Carlo calculations which were performed for the same conditions as the experiment. Good agreement was obtained not only for equidissipation profiles but also for absolute values of the energy dissipation between the experiment and the calculation. This encourages us to apply the Monte Carlo calculations to problems of electron resist exposure important for microelectronics.
Scanning electron microscopy studies of GaN
Authors: Pankove J. I. , Levin E. R.
Published: February 2003

The surface of vapor−deposited GaN and the cross section of GaN light−emitting diodes were examined using secondary electron emission, cathodoluminescence, beam−induced conductivity, and beam−induced voltage. The GaN layer is an assemblage of identically oriented microcrystals. The Zn distribution in the insulating layer is usually not uniform. High built−in fields occur at the two edges of the insulating layer.
Impurity profiles of GaAs epitaxial layers doped with Sn, Si, and Ge grown with molecular beam epitaxy
Authors: Cho A. Y.
Published: February 2003

Molecular beam epitaxy (MBE) n−type GaAs layers are commonly doped with Sn, Si, and Ge. The abrupt doping profiles resulting from these three dopants differed significantly when the epitaxy was carried out between temperatures ranging from 550 to 615 °C. The abrupt doped profile of Sn−doped GaAs layers when grown above 550 °C did not follow the time−intensity profile of the dopant beam, while layers doped with Si or Ge did. In the case of Sn, the effect is attributed to surface segregation during deposition.
Analysis of the electrical and luminescent properties of CuInSe2
Authors: Migliorato P. , Shay J. L. , Kasper H. M. , Wagner Sigurd
Published: February 2003

We discuss the electrical properties and the luminescence spectra of CuInSe2 melt−grown single crystals as a function of the growth and annealing conditions, and the presence of extrinsic dopants such as Zn or Cd. We find that crystals grown from melts containing a slight Se excess or annealed under maximum Se pressure are p type, whereas crystals grown from excess In melts or annealed under minimum Se pressure (vacuum) are n type. The low−temperature photoluminescence spectra of crystals as−grown or annealed between 400 and 700 °C are characteristic of the conductivity type. At 77 °K, p−type crystals emit in a band peaked at 1.00 eV (type A spectrum), whereas the emission of n−type crystals peaks at 0.93 eV (type B spectrum). Types A and B spectra can be interchanged by alternate anneals in minimum or maximum Se pressure. Type B emission dominates the electroluminescence spectrum of p−n junctions. A sharp band−to−band emission at 1.04 eV is present in the 77 °K photoluminescence spectrum of some high−resistivity samples, confirming that the material has a direct band gap. We find that Zn and Cd are donors. Crystals doped with these impurities have electron concentrations above 1018 cm−3. Zn−doped samples exhibit a very broad photoluminescence band below the band gap at both 77 and 300 °K.
Relationship between impact yield stress and indentation hardness
Authors: Gilman J. J.
Published: February 2003

Impact yield stresses for hard brittle substances can be related quantitatively to indentation hardnesses if it is assumed that both are governed by a critical shear stress criterion for the onset of rapid plastic flow. The critical shear stress τgp is related to the shear stiffness on the glide plane by τgp?0.043Ggp. Therefore, hardness measurements can be used to obtain low−temperature yield stresses for these materials and to estimate impact yield stresses.
Analysis of the thermal desorption spectra of inert−gas ions implanted into a nickel (100) crystal
Authors: Edwards D.
Published: February 2003

A multisweep type of experiment has been used to obtain activation energies for the first−order desorption transients of inert−gas ions implanted into a nickel (100) crystal without assumption concerning preexponential factors. In addition, a method is described in which the substitutional inert−gas diffusion energies may be estimated (to within 10%) from thermal desorption spectra and applied to the present experiments. The diffusion energies obtained are ENe=2.44±0.24 eV, EAr=1.83±0.18 eV, and EKr=2.11±0.21 eV. The analysis has also allowed the neon ion implantation depth to be estimated from the thermal desorption experiments. In particular it is found that 7−keV neon has a 50% range of ∼124 Å in the nickel sample.
Obtaining subsurface profiles from surface−acoustic−wave velocity dispersion
Authors: Szabo T. L.
Published: February 2003

Surface acoustic waves can be used to probe nondestructively subsurface gradients (caused by physical processes) by changing their penetration depth with frequency. A perturbation−theory integral equation that describes the influence of a known gradient on the velocity dispersion is reviewed. The experimental situation requires solution of the ’’inverse problem’’: obtaining the profile from measured velocity data. The inverse problem is solved exactly by the use of Laplace transforms for gradients of the general form F (z). The nature of the solution allows observations about the gradient−dispersion relationship, the physical interpretation of dispersion curves, and the representation and measurement of gradients to be made. Six commonly occurring gradient functions and their dispersion curves are compared by use of an equivalent−area parameter formulation. The solution agrees well with published experimental results for residual stress in an aluminum block and for damaged layers on YZ LiNbO3 substrates. For cases in which the analytic form of neither the dispersion nor the gradient is known, a method is presented for obtaining the gradient from raw data. This technique is applied to published results for quench−hardened−steel cylinders, and the experimental implications of gradient determination are discussed.
Electron diffraction study of the epitaxy of Cu2O on the (001) face of copper
Authors: Homma Teiichi , Yoneoka Toshiaki
Published: February 2003

The epitaxy of Cu2O crystal formed on the (001) face of copper during oxidation has been investigated with reflection HEED and electron microscope techniques. Carefully prepared Cu single crystals were used as substrates. A transitional epitaxial orientation of the oxide was found before completely developed twin oriented (111) epitaxy. For oxides formed in the early stage of oxidation, the (221) and the (332) epitaxies have been found. The misorientation of the surface affected these epitaxial aspects. The observed aspects may be explained being based on surface morphological structures as facets composed of (001), (111), and (113).
Effects of surface films and film edges on dislocation movement in silicon
Authors: Hu S. M.
Published: February 2003

We report the observation of two effects of surface films on the movement of dislocations in silicon substrates. One is the retarded movement of dislocations near the film−covered surface. The second effect is associated with the discontinuities in the surface films on continuous substrates and is either a blocking or an enhancement of the movement of dislocation loops in the vicinity of the discontinuities—depending on the direction of the movement. We conceive a model to explain that the second effect is the result of differential contraction between the film−substrate composite, giving rise to a nonvanishing shear stress component τzx, which peaks in the vicinity of the film discontinuity. These two effects are demonstrated by the observation of the consequent response of the shape and the size of indentation dislocation rosettes and the distribution of dislocation loops in the rosettes.
Structure of thin lead oxide layers as determined by x−ray diffraction
Authors: Light T. B. , Eldridge J. M. , Matthews J. W. , Greiner J. H.
Published: February 2003

Thin lead oxide layers (30−80 Å thick) %were grown on evaporated lead films using both thermal oxidation and rf oxygen plasma oxidation. These layers were characterized structurally, using x−ray diffraction in the standard Bragg−Brentano configuration. The layers were crystalline orthorhombic PbO with a very strongly preferred (001) orientation parallel to the {111} preferred orientation in the evaporated Pb films. Thickness and strain were determined from line broadening and peak shift, and the strain as a function of thickness is explained using a simple dislocation model for the structure of the lead−lead oxide interface. The high−temperature orthorhomic phase observed may be stabilized by epitaxial forces.
Evaporation of solids by laser pulses. I. Iron
Authors: Olstad R. A. , Olander D. R.
Published: February 2003

The laser−induced vaporization of iron was studied using a quadrupole mass spectrometer detector. Neutral atoms emitted by thermal processes at the surface were of interest; energetic ions produced by a plasma near the surface were not. Conventional mode laser pulses served as a heat source and the characteristics of the pulses of vaporized atoms reaching the mass spectrometer were determined by time−of−flight analysis of the output signal from this device. The data agreed reasonably well with the predictions of an equilibrium model, in which transient surface vaporization is treated as a sequence of equilibrium stages at each of which Langmuir vaporization with unit condensation coefficient occurs. Agreement between theory and experiment failed at high laser energies because of the outward flow of molten iron from the spot struck by the laser. This cratering phenomenon invalidated the temperature calculation from which the vaporization rate was calculated.
Photoelectron emission from aluminum and nickel measured in air
Authors: Smith Tennyson
Published: February 2003

Photoelectron emission from Al and Ni has been performed under atmospheric condtions. Measurements of photoemission current Ip as a function of oxide thickness yield attenuation lengths of 28 Å for Al2O3/Al and 71 Å for NiO/Ni for λ=2500 Å (∼5 eV). Photoemission from Al2O3/Al originates at the metal and is only attenuated by the oxide unless the oxide is bombarded with Ar+. After ion bombardment the oxide also emits electrons. Photoemission from NiO/Ni originates from the oxide for λ=2500 Å. Estimates of oxide film thickness can be made for very thin films (0∼200 Å) by very simple photoemission measurments in air.
Optoelectronic measurements of prebreakdown current in an air gap
Authors: Murooka Y. , Hirano T. , Kishi K.
Published: February 2003

The prebreakdown current in the development of the corona streamer and the following leader stroke has been studied by use of an optoelectronic technique with high response characteristics. The prebreakdown currents flowing at both the high−potential and the earth−potential electrodes were simultaneously measured using rod electrodes arranged in parallel. The shape of the end face of each electrode was either needlelike or hemispherical. Except for the charging current, the observed current pulses flowing at the relatively positive electrode were always larger than those of the negative, despite the shape of the end face of the rod electrodes. From the results, it is suggested that the final spark path on the parallel electrode geometry will be dominantly decided by the development of the positive streamer or the positive leader corresponding to the current pulses observed at the relatively positive electrode.
Injection of ions into glass from a glow discharge
Authors: Carlson D. E. , Tracy C. E.
Published: February 2003

Glow discharges have been used to inject singly charged ions into soda−lime−silicate glass at ∼300 °C. Ion injection has been confirmed for ions such as Ni+, Nb+, Mo+, Ta+, etc., using x−ray fluorescence analysis, Auger spectroscopy, and ion scattering spectroscopy. A model based on the band structure of SiO2 predicts that ∼80% of all elements (those with ionization energies less than ∼10 eV) can be injected into a silicate glass from a glow discharge.
Flux pinning centers in superconducting Nb3Sn
Authors: Scanlan R. M. , Fietz W. A. , Koch E. F.
Published: February 2003

Very high critical current densities (Jc=8×105 A/cm2 at 4.2 K and 6 T) have been achieved in commercial Nb3Sn tape and more recently in multifilamentary Nb3Sn superconductors. The relative contributions of two types of pinning centers, grain boundaries and second phase particles, to flux pinning have been determined by correlating Jc with microstructure. It was found that grain boundaries were the only defect present in sufficient density to account for flux pinning in the multifilamentary Nb3Sn material. The dependence of Jc on grain size was measured, and the relationship between pinning force and grain size is discussed in terms of current theories for flux pinning in type-II superconductors.
Low noise parametric upconversion with a self-pumped Josephson junction
Authors: Kanter H.
Published: February 2003

Experimental results are reported on a Josephson parametric upconverting amplifier which is self-pumped via the internal Josephson oscillations derived from a dc bias voltage. A niobium point-contact SQUID is simultaneously coupled to a 115-MHz tank circuit and a 9-GHz cavity. Josephson oscillations at 9 GHz produce parametric upconversion of power in the 115-MHz circuit to sidebands at 9±0.115 GHz with measured power gain of 25. The amplifier noise temperature, referred to the input at 115 MHz, was established to be <15 K by varying the temperature of an input termination from 4.2 to 300 K. This result establishes the behavior of self-pumped SQUID upconverters at microwave frequencies and demonstrates that the achievable noise performance is not greatly in excess of the thermal limit.
Scanning electron microscopy of charging effect on silicon
Authors: Kato T. , Matsukawa T. , Koyama H. , Fujikawa K. , Shimizu R.
Published: February 2003

Charging effect induced by an analyzing electron beam of a SEM has been observed on the cleaved surface of a silicon wafer. It was ensured that this is due to the formation of an oxide layer on the silicon surface. Using this effect, two new applications of the electron-beam-induced-current (EBIC) mode are performed. One of them is a distinction between n− and n+ regions in an EBIC image of SEM with high contrast. The other is a new observation of the defects located at the surface as an EBIC image.
Electromagnetic wave propagation in a moving magnetoplasma medium in the presence of a boundary
Authors: Mukherjee P. K.
Published: February 2003

Some specific features of electromagnetic wave propagation in a moving magnetoplasma, bounded by a plane, are studied. Expressions are obtained for the modified Snell’s law of refraction, the critical angle for total reflection, the refractive indices, and the phase and the group velocities of the waves supported by the moving medium. Analytic conditions for the total reflection of H-polarized incident wave (with the electric vector in the plane of incidence) are also discussed.
Impedance probe and dc probe studies on a collisional plasma in an arc discharge
Authors: Basu J. , Sen C.
Published: February 2003

The collision-dominated plasma of a hot-cathode arc discharge in argon has been studied by a plane probe acting simultaneously as a rf impedance probe and a dc probe. Measurements carried out under different discharge conditions show that the electron temperatures, as given by the rf and dc methods, are in excellent agreement and that the corresponding electron densities agree fairly well, the agreement being better than that mentioned earlier for the plasma of a glow discharge. The thickness of the probe sheath as a function of the sheath voltage, as measured by the rf
Switching and polarity-dependent memory effects in Se-SnO2 and Se-In2O3 thin-film devices
Authors: Purkiss S. , Collins R. A. , Temple B. K.
Published: February 2003

A memory switching effect has been observed in MO/Se/M thin-film structures where MO may be either SnO2 or In2O3 and M may be Au, Fe, or Cu. The devices exhibit a symmetrical threshold switching behavior from which a memory state may be derived by holding the device in the forward on state for a short time. The original threshold state may be restored by subjecting the device to a suitable bias.
Alteration of the Hugoniots by bubble flow
Authors: Leiber C. O.
Published: February 2003

Voids small in respect to the rise length of a shock obtain at most a threefold particle velocity in respect to the surrounding medium if viscous forces of the matrix are overcome by shock attack. It is possible, therefore, that bubbles obtain velocities greater than the shock velocity, penetrate the shock zone, and expand ahead of the shock simultaneously, consequently leading to an alteration of compressibility and shock velocity. If 3up≳us in porous medias, alterations of the Hugoniots are almost always observable.
An analysis of the superinjection phenomenon in heterostructure devices
Authors: Cheung D. T. , Pearson G. L.
Published: February 2003

The principles of superinjection are elucidated through an analysis of the injection properties of p (GaAs) -p (AlGaAs) -n (AlGaAs) heterostructure devices. It is shown that under forward bias, the quasi-Fermi level is discontinuous at the heterojunction interface. The threshold currents above which superinjection takes place for different device parameters are calculated. The results are useful in designing heterojunction lasers and related devices.
Coupled lateral modes in narrow stripe injection lasers
Authors: Sommers H. S. , Butler J. K.
Published: February 2003

The paper concerns the modal description of lasers having a facet intensity distribution with deep central minimum and beam profile in the junction plane with strong forward maximum, such as have been observed in various types of narrow stripe lasers. The difference in symmetry between near and far field prevents analysis in terms of either simple Hermite-Gaussian or simple box modes. Simultaneous resolution in wavelength and beam angle shows that the longtudinal mode groups are doublets of which one member radiates a beam of even and the other odd symmetry. The observations are interpreted in terms of the theory of a pair of strongly coupled dielectric waveguides, one located under each edge of the metal stripe contact. A model calculation of a thin double-heterojunction wafer enclosing a pair of dielectric waveguides formed by small abrupt discontinuities, with parameters adjusted to reproduce the observed intensity distribution along the junction plane, gave a frequency splitting of about 0.1 Å compared to the observed splitting of 0.6 Å.
Spreading of a viscous drop on a smooth surface—Extension of Strella’s analysis
Authors: Markworth Alan J. , Glasser M. Lawrence
Published: February 2003

An apparently complex integral has been derived by Strella to describe the spreading of a viscous drop on a smooth planar surface. In this work, we show that Strella’s integral can be reduced to an elementary form which can be integrated analytically. We then obtain a relatively simple transcendental relation describing the temporal variation of the contact angle between the drop and the surface. In addition, we find that our approximation for the integral, corresponding to the earliest stages of spreading, differs from Strella’s result by a factor of 2.
Discharge spatial nonuniformity in e-beam-sustainer CO2 lasers
Authors: Theophanis George A. , Jacob Jonah H. , Sackett Steven J.
Published: February 2003

The discharge in an electron-beam-sustainer atmospheric pressure CO2 laser is investigated. An arbitrary two-dimensional geometry is employed in calculating the electric field. The conductivity is a function of the local electric field, the loss rate, and the ionization rate, the third of which is proportional to the energy deposition by high-energy electrons. The predicted discharge nonuniformities are compared with experimental results. Experimental evidence indicates that the discharge is recombination dominated.
Low-Reynolds-number flow of a second-order fluid past a porous sphere
Authors: Verma P. D. , Sacheti N. C.
Published: February 2003

The conversion of energy from a laser-generated heat pulse to an acoustic wave in a liquid is considered in detail. In particular, the development of finite and large amplitude pressure waves is treated with the help of a table of state functions for the liquid. Optical saturation is included in the numerical computation and shown to produce increased depth of heating in the dye. Saturation generally decreases the peak pressure and increases the pulse width. An exception is the case when the optical wave saturates the dye and penetrates it with a velocity near Mach one. In this case, pressure amplitude grows with increasing laser pulse penetration. Calculations are carried out for plane, cylindrical, and spherical geometries. Experimental comparisons with calculations are made for the free-surface boundary condition and there is a good agreement.
Steady-wave profiles in a Stokesian fluid
Authors: Swan G. W.
Published: February 2003

The motivation for the present work was as follows. No experiments, as of yet, support the existence of the Stokesian fluid. Perhaps by the experimental examination of steady-wave profiles it may be possible to demonstrate their existence. Before trying such experiments it is worthwhile to construct the mathematical details of the profiles. The general constitutive relation for the Stokesian fluid has been derived by Reiner and others. In this paper this relation is used to analyze steady-wave profiles. It is shown that the profiles are given by complicated implicit expressions, in contrast to the simple profiles arising from the Burgers equation, which occurs in the paper as a special case of the general theory. One other special profile is also obtained.
Laser-generated thermoelastic shock wave in liquids
Authors: Bushanam Gangadaran Siva
Published: February 2003

In the present investigation the procedure of matched asymptotic expansion has been applied to obtain a higher approximation for the flow of an incompressible second-order fluid past a porous sphere. The boundary conditions have been satisfied by matching Stokes (inner) and Oseen (outer) solutions of the stream function. The terms in the inner expansion are the solutions of nonlinear partial differential equations which have been solved approximately by expanding in terms of a non-Newtonian parameter S, which is small. The drag experienced by the sphere has been obtained and is discussed for a few particular cases.
Stress-generation and unloading properties of pulse-heated porous carbon determined by a side gauging technique
Authors: Benson D. A.
Published: February 2003

Measurement of the thermomechanical response of a porous carbon induced by a pulsed electron beam and the associated relief-wave velocities for the stress pulse unloading are described. These measurements are sufficient to determine an effective Grüneisen coefficient for energy inputs to 500 cal/g. The measurements are accomplished with a new side gauging technique which does not require wave propagation out of the heated region of the sample. A laser interferometer system is used to detect the lateral displacement of a target free surface vs time for the microsecond time duration immediately following deposition. The displacement-time measurement also permits detection of the unloading wave velocity in the heated material. Through use of a porous-solid collapse model (the P-α model), comparisons of the present results to computer calculations of the displacement-time profile show significant differences from the observed wave profiles.
Growth of fine holes in polyethyleneterephthalate film irradiated by fission fragments
Authors: Komaki Yoshihide , Tsujimura Shigeo
Published: February 2003

Growth of fine holes by chemical etching in polyethyleneterephthalate films exposed to fission fragments were followed by measuring gas flow through films. The etching rate along tracks and the radial etching rate were determined at hole diameters of 100–3000 Å and hole densities of 106–108/cm2.
(GaAl)As-GaAs heterojunction transistors with high injection efficiency
Authors: Konagai Makoto , Takahashi Kiyoshi
Published: February 2003

n (GaAl)As-pGaAs-nGaAs heterojunction transistors were fabricated by the liquid-phase epitaxial technique, where two kinds of etchants were used to expose the pGaAs base region. The characteristics of the heterojunction transistors are examined as functions of the injection current density and the temperature. Electrical measurements showed that the transistors have a common emitter current gain β of up to 350. The defect current component in the emitter heterojunction is the recombination current in the depletion region.
Thallium-doped silicon ionization and excitation levels by infrared absorption
Authors: Nevin Joseph H. , Henderson H. Thurman
Published: February 2003

The thallium ionization level in silicon is the lone group-III acceptor (of the classical outer s2p atomic configuration) remaining heretofore imprecisely defined. Thallium is also the only such impurity not previously defined as to its bound-hole (inverse hydrogenic) excitation levels within the energy gap. From room-temperature infrared absorption data the thallium level is here located at 0.255 eV above the top of the valence band in silicon. This compares with previously reported ionization values of 0.22, 0.26, and 0.30±0.03 eV, all determined by nonoptical methods. Six thallium hydrogenic bound-hole excitation levels were identified within the energy gap.
Reduced degradation in InxGa1−xAs electroluminescent diodes
Authors: Ettenberg M. , Nuese C. J.
Published: February 2003

Lifetests at 1000 A/cm2 have been carried out on InxGa1−xAs (0<x<0.25) electroluminescent diodes prepared by vapor-phase and liquid-phase epitaxy. As the InAs content of the alloys is increased from 0 to 25 mole%, the junction emission energy shifts from 1.4 to 1.05 eV and the degradation rate decreases by about three orders of magnitude. Consequently, diodes emitting near 1.06 μm at room temperature show little or no degradation after 1000 h at 1000 A/cm2 bias. In addition, lifetest results for a few vapor-grown GaAs1−xPx and InxGa1−xP electroluminescent diodes are consistent with the strong exponential dependence of degradation rate on emission energy observed for the InxGa1−xAs diodes. This effect has been found to be independent of large differences in growth technique, dislocation density, and initial electroluminescence efficiency. Moreover, p-n junctions of InxGa1−xAs have been found to be relatively insensitive to fabrication and device-mounting procedures that are known to be deleterious to similarly prepared diodes of GaAs. Finally, a study of the I-V characteristics and minority-carrier lifetime shows that the observed degradation is a bulk phenomenon.
Preferentially etched diffraction gratings in silicon
Authors: Tsang Won-Tien , Wang Shyh
Published: February 2003

Here, we describe the fabrication of diffraction gratings in the {100} surfaces of silicon by preferential etching. The gratings thus made have grooves with well-defined geometric shape and bounded by nearly perfect reflecting walls. Meanwhile, the importance of utilizing this technique in integrated optics is also discussed.
Comparison of leakage currents in ion-implanted and diffused p-n junctions
Authors: Kircher C. J.
Published: February 2003

Phosphorous diffused and arsenic ion-implanted p-n junctions have been prepared in 0.5- and 2-Ω cm p-type 〈100〉 Si wafers. Leakage currents have been measured on gated diode structures of various geometries as a function of bias voltage and temperature. From these measurements the relative importance of the surface, depletion layer, and bulk carrier generation to junction leakage have been determined. The leakage current levels measured on the ion-implanted junctions are comparable to those measured on the diffused junctions. The surface generation leakage component is the largest, ranging from 5×10−15–10−13 A/mil2 at 25 °C. This sufficiently large to dominate the leakage current for junctions with areas less than approximately 103 mil2. The depletion-layer generation current IDB is much smaller than would be expected. It is only comparable to the diffusion current at 25 °C where IDB?IDIFF?10−16 A/mil2 for defect-free junctions. IDIFF becomes the largest for large-area diodes or for junctions of any area at higher temperatures. The dependence of the leakage current on junction reverse bias and gate bias voltage is stronger than would be predicted for growth in the depletion-layer thickness with bias. We observe IL∼Vn with n∼1–2. This enhanced leakage occurs at the junction perimeter and is associated with increased perimeter electric fields.
Rotational temperature in a high-pressure pulsed CO2 laser
Authors: Leland W. T. , Kircher M. J. , Nutter M. J. , Schappert G. T.
Published: February 2003

Small-signal gain at line center for a group of lines has been utilized to deduce the time dependence of rotational tempreature in pulsed high-pressure CO2 laser systems. Attempts to extract additional information on excited-state population densities is compromised by uncertainties in the vibration-rotation interaction. Anomalies in the small-signal gain for the P20, P28, and R14 lines of the 10.4-μ band are observed.
Optical waveguiding in LiNbO3 single-crystal film grown by the EGM technique
Authors: Miyazawa Shintaro , Sugii Kiyomasa , Uchida Naoya
Published: February 2003

We report optical waveguiding in LiNbO3 single-crystal film grown onto a LiTaO3 substrate by the epitaxial-growth-by-melting (EGM) technique. Studies on the x-ray rocking curve and waveguide mode indices have indicated that the film has a graded refractive-index distribution. We have estimated the index profile on the basis of the WKB method, and have found that the index profile is approximated by a linear distribution. Light propagation loss has been measured to be about 1 dB/cm for the film with the surface flatness of λ/10. Poling of the film has been achieved by the field-cooling technique using a newly developed setup.
Disorder resistivity of gadolinium-dysprosium alloys at T=0 °K
Authors: Yang Jan Jan , Yang Tien Tsai
Published: February 2003

The experimental spin-disorder resistivity of Gd-Dy alloys at temperatures above the magnetic transition point has been compared with Dekker’s theoretical expression. The inter-Coulomb potential and the exchange coupling constants obtained from this comparison have been used to calculate the disorder resistivity of Gd-Dy alloys at T=0 °K. The agreement between calculated results and experimental data is reasonably good.
Ion migration in titanium dioxide films
Authors: Schrager M. , Collins F. C.
Published: February 2003

This paper describes a study of ion migration in polycrystalline rutile (TiO2) films making use of a new MOOS device of the form metal electrode/TiO2/SiO2/Si. Ion migration in rutile films has been monitored through the use of temperature-bias treatments, followed by capacitance-vs-dc bias (C-V) measurements. Field-induced ion migration is induced at considerably lower temperatures in rutile than in SiO2. Large horizontal negative shifts in the C-V curve occur following biasing at elevated temperatures when the metal electrode has been positively biased. The temperature dependence of these shifts, and therfore, the ionic surface-charge density in rutile films, appears to obey an Arrhenius-type equation, with an activation energy of 0.46 eV. The relaxation time for these shifts is of the order of 17 min at 90 °C. The ions involved in these shifts may arise as a result of field-enhanced production of anion vacancies and mobile Ti+3 ions, or of introduction of protons from chemisorbed water, or of the presence of predominantly alkali metal-type ions.
Ion-induced migration of Cu into Si
Authors: Hart R. R. , Dunlap H. L. , Marsh O. J.
Published: February 2003

Ion bombardment of Cu-contaminated Si surfaces with either 20-keV Ne+ or 800-eV Ar+ ions leads to enhanced migration of Cu into the bulk of the Si to depths comparable to the projected range of the incident ions. The migration proceeds sufficiently rapidly to prevent sputter removal of submonolayer amounts of Cu even though as much as 100 Å of the substrate is sputtered away. The enhanced migration is probably caused by defect production during the slowing down of the incident ions. The depth distribution of the Cu following Ne+ or Ar+ bombardments was determined from backscattered energy spectra of 280-keV α particles.
On the phonon contribution to dislocation dynamics in anharmonic crystals
Authors: Boffi S. , Caglioti G. , Cortellazzi G. , Rossitto F.
Published: February 2003

The phonon contribution σph to the stress-velocity relationship for a uniformly moving edge dislocation is studied by a lattice dynamics approach. For this purpose the power expended by the applied local stress to sustain the uniform motion of the dislocation is equaled to the rate of the dissipated energy into the anharmonic crystal during the motion itself. The dissipated power is calculated as the response of the crystal to this steady motion. A discussion of the general temperature and velocity dependence of σph is presented and qualitative conclusions are attempted.
Piezoelectric current from shunted and shorted guard-ring quartz gauges
Authors: Graham R. A.
Published: February 2003

Current from quartz disks in guard-ring configurations is widely used to sense stress pulse profiles resulting from impact or explosive loading. Normally, the guard ring is loaded with a low-impedance resistive shunt selected to maintain voltage balance between electrodes. A similar configuration in which the guard ring is electrically shorted to the ground electrode with a vapor-plated metallic conductor along the periphery of the disk has also been used to sense stress pulses. An experimental investigation of the current pulses produced when these shorted guard-ring quartz gauges are subjected to impact loading has been conducted to compare the responses of shorted and shunted guard-ring quartz gauges. Gauge configurations with guard-ring widths which vary from 0.5 to 3.0 times the thickness of the disk were investigated. It is found that, unlike the behavior of the shunted gauges, shorted gauges do not exhibit a universal response characteristic, i.e., each shorted gauge configuration has a different response to impact loading. Furthermore, the input stresses at which shock-induced conductivity affects the current pulses is found to be lower for shorted gauges than for the shunted gauges and to depend upon the specific shorted gauge configuration. The effects of the width of the insulating gap which separates the guard-ring electrode from the inner electrode are shown to be detectable. Physical mechanisms responsible for the observed differences between the shunted and shorted guard-ring gauges are identified.
An electron synchrotron maser based on an intense relativistic electron beam
Authors: Granatstein V. L. , Sprangle P. , Parker R. K. , Herndon M.
Published: February 2003

An electron cyclotron maser has been operated with an output of ∼50 MW of coherent radiation at a frequency ∼8 GHz. A magnetic field configuration is described which effectively converts streaming electron energy into energy transverse to the streaming direction. The redistribution of beam energy makes available a source of free energy to be converted, via an instability, into radiation at the Doppler-shifted relativistic electron cyclotron frequency. A nonlinear theoretical analysis shows that the coherent synchrotron radiation is a relativistic negative mass type instability reflecting the fact that the cyclotron frequency is a function of the electron energy. The emission was narrow band with a coherence time ≳50 nsec, and was also spatially coherent being primarily radiated into the TE01 circular waveguide mode. The potential for making a frequency tunable maser by employing a tapered drift tube has also been demonstrated.
Analysis of a magnetic double sheath for ion beam acceleration and deceleration
Authors: Forrester A. Theodore
Published: February 2003

It appears feasible to accelerate or decelerate an intense ion beam without using material grids. Instead, a virtual grid can be established by the use of a crossed field flow of electrons using a uniform magnetic field perpendicular to the ion flow direction. The problem of the magnetic double sheath formed by the intense ion beam and a crossed electron flow has been analytically solved and can readily be applied to any given ion beam situation. The required electron current densities and magnetic fields appear to be moderate in all cases and some examples are presented.
Analytical aspects of electroabsorption modulators
Authors: Bottka N. , Hutcheson L. D.
Published: February 2003

The analytical aspects of a Franz-Keldysh electroabsorption modulator are presented for two geometries, one in which light is propagating in a waveguide junction (in particular a GaAs double heterostructure) and one in wihch light is transverse to the junction. Optimum transmission and electroabsorption attenuation of radiation through a double-heterostructure waveguide will occur for net donor concentrations 1015/cm3 or less. Electroabsorption light attenuation 20 dB or larger with reverse-bias voltages less than 10 V can be achieved. For net donor concentrations 1015 cm−3 or larger, large light attenuation in the transverse geometry can only occur under avalanche conditions within the junction.
Theory and interpretation of the field-effect conductance experiment in amorphous silicon
Authors: Neudeck G. W. , Malhotra A. K.
Published: February 2003

The field-effect conductance modulation experiment, performed on vacuum-evaporated amorphous silicon films, yielded better than three orders of magnitude change in current for both positive and negative gate voltages. The near symmetry of the plots and their change with deposition rate are interpreted in terms of a Cohen-Fritzsche-Ovshinsky-type density-of-states model. Calculations are presented for the model that includes the mobile charge and the mobility ratio of the carriers. Results are presented for room as well as for elevated temperatures. The Fermi energy is near the center of the mobility gap and the density of localized states is nearly uniform for ±0.4 eV above and below EF. At energies greater than 0.4 eV away from the Fermi energy, the density of the localized states is modeled by an increasing exponential out to the limit of the experimental data at about ±0.455 eV. The theory and experiment agree at room temperature and over a range of temperatures and sample preparation conditions. The localized states near EF decrease as the deposition rate decreases. A lower limit of from 6×1019 to 2×1020/cm3 eV remains and is sample preparation dependent.
Role of trap states in the insulator region for MIM characteristics
Authors: Gupta H. M. , Van Overstraeten R. J.
Published: February 2003

A theoretical study of the trap-assisted charge injection in a blocking contact metal-insulator-metal (MIM) structure is made. In this mechanism a charge first tunnels to the vacant trap states in the insulator and is subsequently thermally excited or is tunneled to the conduction band of the insulator. A comparison is made between different contact current mechanisms for such sturctures and it is found that this mechanism is very important for the insulators containing trap states of the order of 1018 cm−3 and more, at low contact voltages. Finally we compare the current-voltage characteristics of various devices containing different density of trap states in the insulator region, with reference to the present theory. We find that the I-V characteristics of solid-state devices strongly depend on the trap density of the insulator region near the cathode