bluuebunny/crossref_metadata_2025 huggingface dataset:
Boundary-value problem for a counterrotating electrical discharge in an axial magnetic field
Authors: Hong S. H. , Wilhelm H. E.
Published: February 2003

An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 106 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.
Temperature dependence of helium blistering in nickel monocrystals
Authors: Sinha M. K. , Das S. K. , Kaminsky M.
Published: February 2003

The (110) and (111) planes of monocrystalline nickel targets have been bombarded with 500-keV 4He+ ions under channeling conditions for a total dose of 6×1018 ions/cm2 and for target temperatures ranging from room temperature to 950 °C. The results indicate a decrease in average blister diameter with increase in target temperature. Large-scale exfoliation of blister skin occurs at 300 °C, and, above 850 °C, holes are observed on the surface.
Defects in InP homoepitaxial layers
Authors: Mahajan S. , Bachmann K. J. , Brasen D. , Buehler E.
Published: February 2003

Defect structures in n-type (001) and (1̄1̄1̄) homoepitaxial layers, grown by liquid phase epitaxy (LPE) on p-type InP substrates, have been evaluated by transmission electron microscopy. It is shown that, even under ideal conditions of lattice match, defect structures are observed in epilayers. The (001) layer exhibits slip structure consisting of screw dislocations. It is argued that this structure could not have evolved to accommodate either the lattice parameter difference or twist that may have been inadvertently introduced during LPE. On the other hand, the (1̄1̄1̄) layer shows isolated faults and fault clusters consisting predominantly of intrinsic faults.
Electro-optic and piezo-optic tuning of second-order nonlinear processes in crystals
Authors: Hon David T.
Published: February 2003

The power-handling capability of crystals utilized for second harmonic generation (SHG) and other nonlinear frequency conversions has until recently been limited to a few watts of average output power, chiefly because of two conditions, namely, thermal instability and thermal gradients. Now, techniques have been invented that correct these conditions with a resulting order of magnitude increase in the average output power produced by SHG. This paper presents the theory for two techniques that solve the problem of thermal instability, namely, electro-optical tuning (EOT) and piezo-optical tuning (POT). Beam shaping, which prevents thermal gradients, will be treated in a separate paper. In this paper, the general physical theory is discussed both for EOT and POT. The equation for the phase-match condition is given. Interactive effects of temperature change ΔT, the applied electric field (E), and the stress field σ on a fixed-position crystal are treated. The general equations for EOT and POT are developed. Examples of the effect on SHG in cesium dideuterium arsenate (CD*A) are given. Using these techniques, with beam shaping to be described in a separate paper, 35 W of average output power at 0.53 μ has already been demonstrated.
Temperature dependence of critical stress in oxygen-free silicon
Authors: Hu S. M.
Published: February 2003

The temperature dependence of the critical resolved shear stress in oxygen-free silicon was determined in the temperature range 800–1050 °C, using the method of indentation dislocation rosettes. We found the stress to vary only about 30% in the temperature range studied, that is, from about 4.3×107 to about 3.2×107 dyn/cm2. The implications on the phenomenon of thermal slip in silicon-wafer processing are discussed.
The effect of elastic strain on energy band gap and lattice parameter in III-V compounds
Authors: Olsen G. H. , Nuese C. J. , Smith R. T.
Published: February 2003

The elastic and misfit strain in vapor-grown InGaP/GaAs crystals was determined by measuring the lattice parameter of the InGaP before and after removal of the GaAs substrate. The energy-band-gap shift as a function of strain was measured in a similar manner using photoluminescence. Up to 70% of the misfit strain was found to be accommodated elastically. The critical resolved shear stress for dislocation motion was found to be ∼2×109 dyn/cm2. The rather low band-gap shift with applied stress of ∼3×10−9 meV/dyn cm−2 was attributed to the Poisson effect. Photoluminescence was found to be a very accurate means to measure composition (and therefore lattice parameter), and empirical expressions were determined for the variation of photoluminescence wavelength with composition, lattice parameter, and energy band gap.
Bandfilling in metalorganic chemical vapor deposited AlxGa1−xAs-GaAs-AlxGa1−xAs quantum-well heterostructure lasers
Authors: Holonyak N. , Kolbas R. M. , Rezek E. A. , Chin R. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

Data are presented showing that quantum-well (Lz∼200 Å) AlxGa1−xAs-GaAs-AlxGa1−xAs heterostructures, grown by metalorganic chemical vapor deposition, can be operated as lasers on confined-particle transitions over an unusually large range (Δλ≳1000 Å). The bandfilling properties of these quantum-well heterostructures, which can easily be excited to carrier densities as high as n≳1019/cm3, are described. Quantum-well laser diodes (x∼0.5) are described that operate (300 K) from the Γ band edge to wavelengths as short as 7700 Å (ΔE∼185 meV). Narrow photopumped samples (15–30 μm) are shown to operate (77 K) as lasers on clearly defined confined-particle transitions from the band edge to 6980 Å (ΔE∼270 meV). On samples from another wafer, laser operation has been observed to 6885 Å (ΔE≡hν−Eg=293 meV). The photoluminescence spectra of these heterostructures extend well into the region of the recently determined L band minima of GaAs.
CdS/InP and CdS/GaAs heterojunctions by chemical-vapor deposition of CdS
Authors: Bettini M. , Bachmann K. J. , Shay J. L.
Published: February 2003

CdS/InP and CdS/GaAs heterojunctions were prepared by an in situ H2S/H2 etching process and H2 transport of CdS onto the InP and GaAs substrates. The etching involves a reaction of the III-V compound surface to the corresponding sesquisulfides and simultaneous or subsequent removal by reduction in H2 gas. The etching process changes the junction characteristics considerably. The junction on p-GaAs shows a pinning of the Fermi level at the interface approximately 0.75 eV above the GaAs valence band. The junction on n-GaAs is Ohmic.
Pulse nonlinearity measurements on thin conducting films
Authors: English A. T. , Miller G. L. , Robinson D. A. H. , Dodd L. V. , Chynoweth T.
Published: February 2003

A new pulsed nonlinearity measurement is described and applied to the characterization of thin-film conductor stripes. The method is based on the phenomenon of ’’baseline shift’’, and is substantially simpler than the already familiar third-harmonic method yet, at least potentially, just as sensitive. A model is proposed in which the observed nonlinearity is attributed to the temperature rise accompanying current in conductors and the associated resistance change. Good quantitative agreement has been obtained with predictions based on the model. A specific application of this method to reliability testing has been found in magnetic bubble memories, the lifetime of which correlated closely with pulse nonlinearity measurements.
Laser interferometry by induced modulation of cavity field
Authors: Donati S.
Published: February 2003

The field backscattered from a remote surface into the laser cavity induces an efficient modulation, both in amplitude and frequency, of the cavity field. The modulating signals are the interferometric components (sin and cos) of object optical path length, which can be recovered by heterodyne detection through a separate reference-frequency mode. Using a dual polarization Zeeman stabilized He-Ne laser, a compact self-aligning interferometer is developed.
Mean field analysis of the magnetic properties of vapor deposited amorphous Fe-Gd thin films
Authors: Gangulee A. , Taylor R. C.
Published: February 2003

The temperature dependence of the saturation magnetization of vapor deposited amorphous Fe-Gd thin films have been analyzed in terms of the mean field theory. This analysis yielded values of the Fe spin, and the Fe-Fe and Fe-Gd exchange interaction energies, which were then correlated to composition. The temperature and composition dependence of other magnetic properties can be calculated from these mean field parameters, and the temperature sensitivity of the saturation magnetization of amorphous Fe-Gd alloys is shown to be less than that of amorphous Co-Gd alloys.
Potential of amorphous alloys for application in magnetic devices
Authors: Luborsky F. E. , Becker J. J. , Frischmann P. G. , Johnson L. A.
Published: February 2003

Amorphous alloys have potential applications in all types of magnetic devices, in both the electronic and power areas of application. For electronic devices, the properties are comparable to those of commercial alloys and the materials offer potentially much lower cost. In power applications such as transformers, losses are far lower than in materials used at present. This results in a potential favorable trade-off between first cost and a substantial energy savings throughout the life of the device. Although power applications have not been emphasized up to now, they appear to hold great promise, especially as wider amorphous tapes become available.
Application studies of injection moldable bonded ferrites
Authors: Badner J. J.
Published: February 2003

Until recently, bonded ferrites have been available only in elastomeric matrices which limited fabrication techniques to calandering and extrusion. This has confined the magnets to parts that could be punched from calandered sheet or cut from extruded profiles. Both of these methods severely limit the shape of the finished magnet. Recent developments in compounding, molding, and orienting techniques have opened up entirely new application areas to bonded ferrites. The shape versatility and economies inherent to injection molding have had a major impact on many applications, and this paper details the effect in several. The features common to all of the applications are that each uses an injection molded magnet of a shape either impossible or uneconomical to duplicate in other magnetic materials, and several functions are combined into one molded part. By reducing both secondary operations and scrap losses, significant savings are being realized.
Structural and magnetic properties in FexSi1−x amorphous alloys
Authors: Mangin Ph. , Marchal G.
Published: February 2003

FexSi1−x amorphous alloys were obtained by the vapor quenching technique. Magnetization measurements and Mössbauer spectroscopy data showed there is a critical composition (xc=0.4) for the appearance of magnetic order which starts with the formation of giant moments; then, an increasing homogeneous behaviour is initiated by percolation of these giant moments. Diffraction studies gave evidences that the magnetic transformation occurs without major structural changes. As a first approximation, Si and Fe atoms can be considered as randomly distributed in a dense random packing of hard spheres.
A high permeability Fe-Ni base glassy alloy containing Mo
Authors: Hasegawa R. , Narasimhan M. C. , DeCristofaro N.
Published: February 2003

This paper reports some of the low field magnetic properties, and their stability, obtained for a glassy Fe40Ni38Mo4B18 (METGLAS- Alloy 2826MB) alloy, which has a Curie temperature of 626 K, room temperature saturation induction of 8.8 kG and a linear magnetostriction of about 9 ppm. When optimally field-annealed, the toroidally wound material shows a coercivity of about 7 mOe, remanence of 7.5 kG and a dc permeability (at B=100 G) of about 45 000. The material’s ac core loss at B=1 kG and f=104 Hz is close to that (∼1.3 watts/kg) of a tape-wound crystalline 4-79 Mo Permalloy core of similar size. The high frequency effective permeability is ∼700 at f=5×105 Hz. This is a factor of ∼7 greater than for 4-79 Permalloy. The thermal stability of these properties is found to be excellent. The improved thermal and magnetic properties of the present material over Fe-Ni-P-B glassy alloys significantly enhance the opportunity to apply these materials in various magnetic applications.
Relation in the Ising model of the Lee-Yang branch point and critical behavior
Authors: Baker George A. , Moussa P.
Published: February 2003

In general for an Ising model, the end point of the distribution of zeros of the grand partition function along the unit circle in the activity plane is thought to be a branch point. In the case of the Bethe-lattice, this point is of the square-root type. We point out that for models which exactly satisfy scaling, the coefficients of the partial differential approximants introduced by Fisher are independent of the location and nature of this singularity. Thus, the use of these approximants effectively separates the analysis of the critical properties from those of the Lee-Yang branch point. This branch point is reflected in this approach through the boundary conditions for the partial differential equation. These boundary conditions determine the scaling function. We show this boundary condition problem to be equivalent to the monomer-dimer problem, and prove that there is no phase transition in that problem in any dimension.
Band magnetism in the spin-density-functional formalism
Authors: Gunnarsson O.
Published: February 2003

A band model of magnetism is obtained from the Hohenberg-Kohn-Sham spin-density-functional (SDF) formalism. The equations of this scheme have the simple independent particle form, and correlation effects are included via an effective potential. Usually, this potential is calculated in the local-spin-density (LSD) approximation. This approximation is discussed and reasons for its success are shown. Its accuracy is illustrated by a few applications related to magnetism. The independent particle form of the SDF equations can be used to derive a first principles Stoner model. Results for transition metals obtained using this model as well as using band calculational methods are reviewed. The LSD-Stoner model gives far too high results for the Curie temperature Tc. The reason is probably the neglect of spin fluctuations above Tc in this model. In a calculation for iron dimer it is shown that there is a strong tendency to form local moments in the LSD approximation. The Heisenberg type coupling constant between the moments is discussed. The calculation suggests that spin fluctuations are important.
X-ray line emission and plasma conditions in exploded Fe wires
Authors: Burkhalter P. G. , Dozier C. M. , Stallings C. , Cowan Robert D.
Published: February 2003

Single-wire Fe spectra collected from two different exploded-wire generators (Gamble II and Owl II) were analyzed to determined the ionization stages produced in the plasmas. The temperature for the hot-plasma pinches for both generators was 1.4±0.2 keV at which an abundance of Fe XXIV transitions is produced. The Fe K spectra from exploded wires are basically similar to those produced in the pinched plasma generated randomly in the vacuum spark; however, the exploded wires have lower plasma temperatures than the hottest pinches produced in the vacuum spark. A detailed interpretation of the Fe L spectra formed in the exploded wires permitted line and ionization stage identifications in the 7–12-Å region. Such spectroscopic data is useful for analysis of complex Fe spectra generated in multitemperature plasma devices like Tokamaks.
Measurements of high-energy deuterons in the plasma-focus device
Authors: Gullickson R. L. , Sahlin H. L.
Published: February 2003

Nuclear activation techniques have been used to measure the fluence of high-energy deuterons in a plasma-focus device. Substantial activation of carbon and aluminum targets was observed on most shots where the deuterium pressure was less than 3 Torr. Carbon activation indicates more than 1015 deuterons above 330 keV on some high-intensity shots. These deuterons are strongly forward directed with 0° to 90° ratios exceeding 104 on high-yield shots. Ratios of 13N to 28Al, foil-stack activation measurements, and neutron time of flight all consistently show some deuterons have energies above 2 MeV. Measured 13N/28Al ratios also indicate more than 1012 deuterons of energy greater than 5 MeV, but this result has not been verified by an independent threshold-activation measurement. These measurements illustrate that the plasma-focus device can be operated in two distinctly different modes, with low-pressure operation resulting in the acceleration of ions and electrons to many times the capacitor-bank charging voltage. Most of the neutron emission in low-pressure operation may come from beam-target reactions.
New high-pressure phases of Nb3Si produced by recrystallization of metastable sputter deposits
Authors: Waterstrat R. M. , Haenssler F. , Müller J. , Dahlgren S. D. , Willis J. O.
Published: February 2003

Threee new phases of the alloy Nb3Si have been produced by a relatively low-temperature (∼800 °C) recrystallization anneal under pressures of up to 100 kbars. The new phases are apparently formed only when the Nb3Si starting material has a metastable body-centered-cubic structure which is prepared by sputtering. They are not formed when the Nb3Si starting material has the Ti3P-type structure. One of the new high-pressure phases has a superconducting transition temperature Tc of 5.45 K, but its crystal structure has not yet been identified. The phase formed at 60 and 100 kbars has a tetragonal Ni3P-type structure, but the structure of the 80-kbar phase is not known.
Surface effects on the low-energy cathodoluminescence of zinc oxide
Authors: Bylander E. G.
Published: February 2003

A rapid initial brightness slump and occasional subsequent recovery observed for the zinc-doped zinc oxide phosphor undergoing cathodoluminescence is shown to depend on the surface work function. A quantitative model leads to an explanation of the dependence on surface potential in terms of field-aided or retarded surface recombination. Evidence is given that temporarily recovered surfaces result from dynamic surface adsorption of barium.
A configuration and circuit analysis for one-port SAW resonators
Authors: Tanski William J.
Published: February 2003

One-port SAW resonators fabricated on ST-quartz with recessed electrode transducers and grooved reflector have been found to yield excellent device response characteristics. This configuration is superior to all others tested and is usable over a wide frequency range. The device structure and experimental data are presented. Also, an accurate and easy-to-use calculation scheme is presented to derive the resonance equivalent circuit parameters from experimental data.
Surface effects affecting ac losses of Nb3Sn
Authors: Bussière J. F. , Kovachev V. T.
Published: February 2003

60-Hz losses of Nb3Sn were found to be considerably reduced by anodizing. Anodizing followed by etching in dilute HF was also studied and found to be less effective because of increased surface roughness and hydrogen inclusion after prolonged contact with the acid. The increase of ac losses from contact with the bronze at the surface of Nb3Sn made by solid-state diffusion was investigated. Both a surface effect (proximity?) and thermal stress were found to contribute to the increased losses.
The fundamental solution in the theory of eddy currents and forces for conductors in steady motion
Authors: Boulnois Jean-Luc , Giovachini Jean-Luc
Published: February 2003

A closed-form solution to the central problem of the steady linear motion of an arbitrary current distribution past materials of constant permeability is presented. The application of the Green’s function technique to the field equations yields integral representations of the induction, eddy currents, and electromagnetic forces. Due to interface coupling of the boundary conditions along the surface of the conductor, Green’s functions are shown to satisfy integral equations. In the case of a conducting slab, explicit solutions for the Green’s functions are derived. Application to magnetic levitation and the calculations of forces on moving coils are developed. Results are compared with experimental drag measurements.
Cation distribution and valence state of copper ferrites Cu1−δFe2+δO4
Authors: Nanba N.
Published: February 2003

The equilibrium cation distribution and the valence state on tetrahedral or octahedral sites in copper ferrites Cu1−δFe2+δO4 have been derived by taking account of site exchange not only of cationic nuclei but also of valence electrons. The calculated cation distribution has shown satisfactory agreement with experimental results for the composition range δ?0.5. Two nonequilibrium valence states accompanied by the transposition of valence electrons from the equilibrium sites were expected and they corresponded well to the positive and negative regions in the observed Seebeck coefficient of quenched Cu1−δFe2+δO4.
Controlled texture of reactively rf-sputtered ZnO thin films
Authors: Maniv S. , Zangvil A.
Published: February 2003

Detailed analysis by reflection electron diffraction (RED), x-ray diffraction (XRD), and scanning electron microscopy (SEM) was performed on thin ZnO layers which were formed under reactive and nonreactive rf-sputtering conditions. A variety of textures and morphologies were observed. 100% reproducible piezoelectric layers, preferred oriented with [002] perpendicular to the layer within 7°, could be obtained by reactive sputtering from a zinc target at rf power of 150 W, oxygen-argon atmosphere of 8×10−3 Torr with 35% O2, and with the glass substrate being kept at room temperature by a cooling device. No differences in the surface-acoustic-wave properties were found between reactively and nonreactively sputtered ZnO layers which had similar texture and morphology. SEM techniques proved to be extremely misleading in the study of this type of layer; there is no relationship between an observed columnar structure and the texture of the layer which is determined by RED, and also between the column thickness (∼1 μm) and the actual crystallite size (∼200 Å) which is determined by XRD. It is shown that the observed columns must be polycrystalline.
Magnetic properties of amorphous neodymium–transition-metal films
Authors: Taylor R. C. , McGuire T. R. , Coey J. M. D. , Gangulee A.
Published: February 2003

Amorphous thin films of NdxCo1−x and NdxFe1−x alloys were prepared over the compositional range 0.08⩽x⩽0.71 by e-beam evaporation. Magnetization and anisotropy of the samples were studied over a wide temperature range with the aid of a force balance magnetometer, Hall effect measurements, and Mössbauer spectroscopy. It was found that the magnetization of the alloys could not be accounted for by a completely collinear alignment (ferromagnetic) of the Nd and transition-metal subnetworks. Mean field analysis of the magnetization data showed a large reduction of the Nd–transition-metal exchange coupling as compared to their Gd analogs. A model was developed which requires that Nd be dispersed in a cone whose axis is parallel to that of the transition-metal subnetwork by strong coupling to randomly oriented local crystal field axes. This dispersion reduces the Nd net moment to 77% of its free-ion moment in NdxCo1−x alloys and to 25% of its free-ion moment in NdxFe1−x alloys. There is evidence that some dispersion also occurs in the Fe subnetwork. Anisotropy in NdxCo1−x alloys was found to be proportional to the square of the Nd subnetwork magnetization, Ku=CM2Nd. C was exponentially dependent on concentration according to the relation C=6 exp(−10x).
Analysis of grain-boundary electromigration
Authors: Ho P. S.
Published: February 2003

A general analysis for grain-boundary electromigration applicable for type-A, -B, and -C diffusion kinetics is presented. Following Whipple’s approach in analyzing grain-boundary diffusion, solutions for composition profiles have been derived for isolated boundaries (for type-B and -C kinetics) and for interacting boundaries (for type-A kinetics). Asymptotic expressions for the exact solution have been obtained using the method of steepest descents and conditions for their validity are specified. The asymptotic solutions with opposite driving forces can be linearly combined into two relationships which relate the slopes of the composition profiles directly to the grain-boundary diffusivity and the effective charge. These relationships provide useful formulas to analyze the edge profiles measured in cross-stripe experiments. Martin’s solution was found to provide a reasonable approximation for the composition profile within the valid range of the asymptotic solutions.
Flexible boundary conditions and nonlinear geometric effects in atomic dislocation modeling
Authors: Sinclair J. E. , Gehlen P. C. , Hoagland R. G. , Hirth J. P.
Published: February 2003

A technique is described for applying flexible boundaries to an atomic region in computer simulation of dislocations or other line defects. The method results in continuity of equilibrium, under the chosen interatomic potential, across the interface between the atomic region and the outer region described in terms of anisotropic elastic continuum solutions. The technique has high numerical efficiency. It is shown that when the crystal is initially dislocated according to the Volterra solution for displacements, the finite strains give rise to geometrical nonlinear effects, usually disregarded in linear elasticity, which contribute to a volume change of the crystal. Allowance for this effect, and for elastic nonlinearity in the crystal beyond the boundary region, allows the overall dilatation of a finite body due to the dislocation to be rigorously computed. For illustration of the geometric nonlinear effect, and for comparison with earlier modeling methods, examples of computations are given for the [100] edge dislocation in α iron.
Investigation of compensation in implanted n-GaAs
Authors: Rao E. V. K. , Duhamel N. , Favennec P. N. , L’Haridon H.
Published: February 2003

n-GaAs substrates of varying doping levels were implanted with presumably electrically inactive ions like H, B, and As, and then annealed at high temperatures. Several experimental techniques were employed to detect and estimate the compensation in the implanted layers. We found the compensation in the proton-implanted layers is alone dependent on the initial doping level of the substrate, while it is related to the ion introduced in the boron- and arsenic-implanted layers. Along with these results, we present and discuss the preliminary results of the photoluminescence measurements performed to investigate the nature of the defects responsible for compensation.
Effect of nonlinear absorption on self-focusing of a laser beam in a plasma
Authors: Sodha M. S. , Patel L. A. , Sharma R. P.
Published: February 2003

Considering both the real and imaginary parts of the dielectric constant to be intensity dependent, we have investigated the self-focusing of a Gaussian laser beam in a plasma. The mechanism or nonlinearity considered herein is the ponderomotive force or heating mainly determined by collisions of electrons with heavier particles. An equation for the beamwidth parameter and an expression of the axial intensity have been obtained in the WKB(J) and paraxial approximations. It is seen that the effect of nonlinear absorption on self-focusing is significant. Consideration of nonlinearity in absorption predicts focusing of a laser beam (under certain conditions) even when the linear-absorption approximation would predict defocusing of the beam. The results reduce to the corresponding analytical results reported earlier, when the intensity dependence of the dielectric constant is neglected. The technique adopted in the present investigation for solving the wave equation in the presence of nonlinear absorption is equally applicable to media other than a plasma.
Piezoelectricity and pyroelectricity in polyvinylidene fluoride
Authors: Kepler R. G. , Anderson R. A.
Published: February 2003

The piezoelectric, thermal expansion, and elastic coefficients of two different types of polyvinylidene fluoride film have been measured and used to calculate the secondary pyroelectric coefficient. It is found that secondary pyroelectricity can account for about half the pyroelectricity observed.
Thermoluminescence of LiF TLD-100: Emission-spectra measurements
Authors: Fairchild R. G. , Mattern P. L. , Lengweiler K. , Levy P. W.
Published: February 2003

The thermoluminescence of LiF TLD-100 dosimeter crystals has been studied using recently developed equipment for determining simultaneously the emission intensity and the emission spectrum as a function of sample temperature. Measurements were made on numerous samples exposed to 60Co irradiations at room temperature and at exposures varying from 500 to 3×107 R. Spectra were obtained at 1.38 and 5.5 °C intervals over the temperature range 20–350 °C. Below 105 R the thermoluminescent emission can be described by a single Gaussian-shaped band whose peak energy and full width vary irregularly with temperature and not in accord with the well-known expressions, given in the text, relating the emission-spectra peak energy and full width at half-maximum to the sample temperature. However, the emission is accurately described by three Gaussian-shaped bands whose approximate peak energies and full widths are 3.01, 0.90; 2.90, 0.72; and 2.71, 0.96 eV. The peak energies and full widths of these three bands vary with temperature in the expected manner. In addition to these bands, comparatively low-intensity bands are observed at exposures above 105 R at approximately 4.0, 2.98, 2.50, and 2.3 eV, with the possibility of another band at roughly 1.5 eV. The recorded data for each emission band was subjected to all corrections required to obtain glow curves which are strictly proportional to the number of processes occurring per unit time. In other words, the corrected glow curves are as free as possible of the systematic errors which might render them unsuitable for determining the kinetics. The glow curves extend from room temperature to 350 °C and contain nine prominent glow peaks. Below approximately 80 °C, the emission is confined to the 2.71-eV band. Above approximately 200 °C, the emission is confined to the 3.01-eV band. All three prominent emission bands contribute to the intermediate-temperature glow peaks. With increasing dose, the low-temperature peaks progressively diminish in intensity and the emission shifts to the higher-temperature peaks.
Role of diffused Ga vacancy in the degradation of vapor-grown GaAs
Authors: Kasano Hiroyuki
Published: February 2003

Electron mobility, minority-carrier lifetime, and misfit-dislocation density are measured along the layer thickness direction near the interfacial regions of GaAs crystals grown on GaAs and Ge substrates by vapor phase epitaxy. It is observed that the mobility and lifetime decrease, while the dislocation density increases exponentially, as the layer thickness is decreased. These phenomena are found to be consistently caused by out-diffusion of interstitial Ga vacancies introduced at the epitaxial layer/substrate interface in the stage prior to growth or in the first stage of growth. The diffusion coefficient of the interstitial Ga vacancy (off-centered Ga atom) is estimated to be 3.6×10−5 exp(−11800/T) cm2/sec based on the experimental results.
Incorporation of implanted In and Sb in silicon during amorphous layer regrowth
Authors: Blood P. , Brown W. L. , Miller G. L.
Published: February 2003

Annealing of indium and antimony implanted into silicon at doses sufficient to produce an amorphous layer (1014–1015 ions cm−2) has been studied using high-energy Rutherford backscattering. Annealing of these amorphous layers followed the behavior reported for layers formed by silicon ion bombardment and has a pronounced influence on both the retention and lattice-site location of the impurities, with marked differences between substrates of (111) and (100) orientation. Following epitaxial regrowth on both orientations at 550 °C substitutional concentrations in excess of the solid solubility were observed. Impurity redistribution was not detected at this annealing temperature nor for 940 °C annealing of (100) and (110) substrates, but migration toward the surface was observed after high-temperature annealing of (111) material. This resulted in a loss of ∼60% of implanted In after 1 h annealing, whereas antimony accumulated behind the native thermal oxide. Impurity atoms continued to migrate after lattice annealing had ceased, and it is proposed that the extended defect structure, which is unique to amorphous layers on (111) substrates annealed at high temperatures, provided the means for this out-diffusion. Two-step annealing of (111) material at 550 and 940 °C resulted in a stable impurity distribution, consistent with the absence of this defect structure.
The magnetostatic field of a periodic cylindrical array of perfect conductors of arbitrary x-y cross section
Authors: Waisman Eduardo M.
Published: February 2003

The magnetic field in an imploding wire array is studied. After the initial explosion of the wires the array starts imploding. The process can be considered quasistatic electromagnetically and the assumption of perfect conduction is made. Under these conditions the driving magnetostatic forces generated by the wires need to be calculated in a series of snapshots, which are stages of the magnetohydrodynamics process. For that purpose a Green’s function technique is developed to solve for the magnetostatic field generated by an array of perfectly conducting wires of arbitrary x-y cross section, carrying current in the z direction. The wires are enclosed in an outer cylinder, inside of which they are arranged with angular periodicity. This outer cylinder carries all the returning current, and ideally does not permit any magnetic lines to escape from its enclosure. The resulting equations for the magnetic vector potential (A=A?,∇2A=0 in vacuum, A=0 on the outer cylinder, A=const≠0 on the inner conductors) are implicitly solved by writing the potential as a linear superposition of point (z lines) current densities around the boundaries of the inner conductors. The point current densities are determined by imposition of the boundary conditions. For the case of small round wires not overlapping and sufficiently far from the center, an explicit solution is found in the form of an angular Fourier series, having as expansion parameter the ratio between the radius of the inner conductors and the distance to the center, times the number of wires periodically arranged. For the general case the problem is discretized by considering the boundary of each of the inner conductors as a connected set of segments of either circumferences or straight lines, each segment carrying a different amount of current. This procedure yields a set of N linear equations with N unknowns; the N unknowns are the currents carried by each of the N segments by which the boundary is approximated. Knowledge of these currents solves the problem completely because with them and using the Green’s function and its complex derivative, the vector potential and magnetic field, respectively, can be obtained anywhere in the region of interest. In particular the magnitude of the magnetic field just on the boundary of each of the inner conductors is related to the magnitude of the segment currents through a proportionality constant. An algorithm to solve the linear equations is discussed and representative cases shown. The method is seen to be accurate and fast.
Optical properties of Zn3P2
Authors: Fagen E. A.
Published: February 2003

The optical properties of bulk and thin-film Zn3P2 have been measured at room temperature over the range 0.5–5.0 eV, with emphasis on the region of the interband absorption edge. The bulk absorption edge is found to be exponential in energy for values of absorption coefficient less than about 1500 cm−1. The thin-film absorption edge, when freed of spurious absorptance due to scattering, is also found to be exponential over this range although shallower in slope. Analysis of the thin-film data at higher values of absorption coefficient is inconclusive with respect to the nature of the edge. Nevertheless, indirect evidence suggests that the optical gap is probably direct and lies in the neighborhood of 1.6 eV. Measurements of refractive index in the near-infrared yield n=3.3±0.1 in the long-wavelength limit. The ultraviolet reflectivity spectrum is redetermined, and found to differ substantially from earlier reports. Results are discussed in terms of the Dow-Redfield model of exponential absorption edges, the effects of spin-orbit and crystal-field splittings, and effects arising from the equilibrium distribution of bond lengths peculiar to this material. It is concluded that the optical properties of Zn3P2 thin films are suitable for use in photovoltaic cells, provided antireflection coatings are employed.
Effects of hydrostatic pressure up to 25 kbars on zinc oxide varistors—Static loading
Authors: Schoutens Jacques E. , Senesac Steven L.
Published: February 2003

To date, zinc oxide varistors have been subjected to uniaxial compression to 5 kbars and hydrostatic pressures to 10 kbars. These results show a behavior between current and pressure empirically described by IL∼P7. This paper presents results of experiments in which zinc oxide varistors were subjected to hydrostatic compression up to 25 kbars. Results show a significant departure from previously reported results. The leakage current remains constant at first until a pressure of 6–7 kbars is attained. It then rises sharply and nonlinearly to a maximum value of about 55 μA at a pressure of 15 kbars, and subsequently the leakage current decreases by about two orders of magnitude as the pressure increases from 15 to 25 kbars. The limit of 25 kbars is determined by the pressure cell design and materials used. The results presented here also suggest that the varistor behavior with pressure depends on thermal annealing and strain-induced damage processes.
Deep emission centers in Ge-implanted GaAs
Authors: Yu Phil Won
Published: February 2003

Photoluminescence emission spectra from Ge-implanted layers in GaAs were studied with respect to changes of exciting wavelength, excitation intensity, temperature, and the depth of the implanted layers. Deeper emissions are dominant in the near-surface region because vacancies and their complexes with Ge play important roles in the radiative processes. Emission due to donor-acceptor pair transition involving the Ge acceptor is present in all Ge-implanted layers. The binding energy of the Ge acceptor is estimated to be 40±3 meV from the temperature dependence of the emission due to conduction-band–to–Ge-acceptor transitions. High-temperature annealing at 900–950 °C with a Si3N4 cap is needed to increase the Ge activation which produces p-type conduction.
Young’s modulus measurements of thin films using micromechanics
Authors: Petersen Kurt E. , Guarnieri C. R.
Published: February 2003

Electrostatically deflectable cantilever beams (1000–9000 Å thick, 120–8.3 μm long) have been fabricated from a number of thin insulating films prepared by a variety of deposition methods. Measurements of the transverse mechanical resonant frequencies of these beams have been used to calculate Young’s modulus of the insulating thin films. This new technique is relatively simple and accurate and is applicable to a wide range of materials and deposition procedures.
Chalcogenide thin films for laser-beam recordings by thermal creation of holes
Authors: Terao Motoyasu , Shigematsu Kazuo , Ojima Masahiro , Taniguchi Yoshio , Horigome Shinkichi , Yonezawa Seiji
Published: February 2003

The shapes of holes thermally created by a laser beam in thin films of wide range of materials are studied. The most cleanly shaped holes, which measure up to recent requirements for direct-read-after-write video recordings by submicron dots, are obtained in some compositions of amorphous chalcogenide thin films such as As-Te system, Ge-Te system, As-Se system, Ge-Se system, and Sb-S system thin films. The experiments clarify several important conditions helpful in obtaining cleanly shaped holes. The most important condition is that the viscosity of the material in liquid or softened state should be high. The required incident laser-beam power for recording in an As-Te system thin film on a polymethyl methacrylate substrate rotating at 1800 min−1 is about 10 mW. Addition of Se to the As-Te system thin films greatly increases film stability. A signal-to-noise ratio of about 45 dB is obtained in reproduced color video signals.
Mode coupling between slab-type optical waveguides via dichroic absorption of M centers
Authors: Sasaki K. , Kamimura T. , Kaneko H. , Watanabe H. , Hamano O.
Published: February 2003

Guided wave coupling in slab-type optical waveguides covered with an NaF crystal containing oriented M centers is analyzed with the complex propagation constant. In this treatment the complex coupling coefficient is also introduced. An additional experiment supports this analysis. This conception is useful in designing optical waveguide functional devices.
Radiative-transfer theory for the remote sensing of layered random media
Authors: Djermakoye B. , Kong J. A.
Published: February 2003

The radiative-transfer theory for the remote sensing of layered media has been developed with the use of random permittivities to account for scattering effects. Analytical solutions for a three-layer model are discussed for applications to both active and passive remote sensing. Various numerical results are illustrated to show the dependence of the brightness temperature variations on the layer thickness, the variance, the correlation length, and the permittivities. Usually the brightness temperature increases when the loss tangents increase and decreases when the variances and the correlation lengths increase. We also illustrate the case of a homogeneous layer on top of a scattering layer where the brightness temperature increases as a function of frequency and the case of only a scattering layer where brightness temperature decreases as a function of frequency.
Relationship between total arsenic and electrically active arsenic concentrations in silicon produced by the diffusion process
Authors: Murota Junichi , Arai Eisuke , Kobayashi Kenji , Kudo Kiyoshi
Published: February 2003

The dependences of diffusion coefficient of As, DAs, upon total As concentration, CT, and the relationships between CT and resistivity ρ for several diffusion temperatures are experimentally obtained for the As diffusion into p-type Si from doped polycrystalline-Si sources in the temperature range 850–1050 °C. It is found that the relationship between CT and ρ is dependent upon diffusion temperature for CT above 1020 cm−3. The relationship between CT and electrically active As concentration at diffusion temperature, CA, i.e., CT=CA+(3.2×10−6/n3i) C4A can be obtained, assuming that only electrically active As is mobile and is diffused by the single-level vacancy mechanism, and using the experimental result that the dependence of DAs/Di (Di is the intrinsic diffusion coefficient of As) upon CT/ni (ni is the intrinsic electron concentration) is not influenced by diffusion temperature. Using the above equation, it is found that the relationship between CA and ρ is independent of diffusion temperature, even for CA above 1020 cm−3, and can be approximated for CA above 1020 cm−3 by an empirical equation: ρ=8.7×104 C−2/5A.
High-field properties and scaling in CVD-prepared Nb3Ge
Authors: Thompson J. D. , Maley M. P. , Newkirk L. R. , Bartlett R. J.
Published: February 2003

The upper critical field Hc2 and the field-dependent critical current density Jc(H) have been determined for high-Tc Nb3Ge prepared by the chemical vapor deposition (CVD) process. Measurements were performed on short samples taken from long lengths (∼10 m) of Nb3Ge deposited under various conditions onto metallic substrates. Using the theory of Hohenberg and Werthamer for dirty type-II superconductors, values of Hc2(0) were extrapolated from resistive measurements of Hc2 near Tc. Values of Hc2(0) ranged from 32.2 to 33.1 T, the highest upper critical field reported for bulk Nb3Ge. From measurements of Jc(H), pinning force densities Fp were calculated and compared to the Kramer model of flux pinning which predicts certain scaling laws for Fp. We have tested for these scaling laws and have found qualitative agreement with the model of Kramer. This represents the first demonstration of such scaling in bulk high-Tc Nb3Ge. In addition, values of the flux line lattice shearing parameter Ks have been extracted from our data and are found to be in quantitative agreement with Kramer’s predictions.
A melting model for pulsing-laser annealing of implanted semiconductors
Authors: Baeri P. , Campisano S. U. , Foti G. , Rimini E.
Published: February 2003

The transition to single crystal of ion-implanted amorphous Si and Ge layers is described in terms of a liquid-phase epitaxy occurring during pulsing-laser irradiation. A standard heat equations including laser light absorption was solved numerically to give the time evolution of temperature and melting as a function of the pulse energy density and its duration. The structure dependence of the absorption coefficient and the temperature dependence of the thermal conductivity were accounted for in the calculations. In this model the transition to single crystal occurs above a well-defined threshold energy density at which the liquid layer wets the underlying single-crystal substrate. Experiments were performed in ion-implanted amorphous layers of thicknesses ranging between 500 and 9000 Å. The energy densities of the Q-switched ruby laser ranged between 0.2 and 3.5 J/cm2; time durations of 20 and 50 ns were used. The experimental data are in good agreement with the calculated values for the amorphous thickness–energy−density threshold. The model deals mainly with plausibility arguments and does not account for processes occuring in the near-threshold region or below the melting temperature.
The short-wavelength response of MIS solar cells
Authors: Green Martin A.
Published: February 2003

With certain combinations of insulator thickness, surface-state density, and barrier height, it is shown that a dead layer can extend up to 750 Å into the semiconductor in metal-insulator-semiconductor (MIS) and Schottky solar cells. This can cause a fall off in short-wavelength response of the cell. Recombination at surface states can cause an additional fall off in spectral response at all wavelengths. By ensuring that the semiconductor surface is strongly inverted, these effects can be minimized and all carriers optically generated near the surface collected. This is confirmed by experimental measurements on Al/SiOx/p-Si MIS cells with particular attention focused on the 330–500-nm wavelength range.
On total reflection at the interface between relatively moving media
Authors: Shrivastava R. K.
Published: February 2003

A set of curves is given from which the velocity range for total reflection at the interface between relatively moving media and the critical angle corresponding to any medium velocity in this range can be easily predicted. Other relevant conclusions are also drawn.