bluuebunny/crossref_metadata_2025 huggingface dataset:
Scales and kinetics of granular flows
Authors: Goldhirsch I.
Published: July 2002

When a granular material experiences strong forcing, as may be the case, e.g., for coal or gravel flowing down a chute or snow (or rocks) avalanching down a mountain slope, the individual grains interact by nearly instantaneous collisions, much like in the classical model of a gas. The dissipative nature of the particle collisions renders this analogy incomplete and is the source of a number of phenomena which are peculiar to “granular gases,” such as clustering and collapse. In addition, the inelasticity of the collisions is the reason that granular gases, unlike atomic ones, lack temporal and spatial scale separation, a fact manifested by macroscopic mean free paths, scale dependent stresses, “macroscopic measurability” of “microscopic fluctuations” and observability of the effects of the Burnett and super-Burnett “corrections.” The latter features may also exist in atomic fluids but they are observable there only under extreme conditions. Clustering, collapse and a kinetic theory for rapid flows of dilute granular systems, including a derivation of boundary conditions, are described alongside the mesoscopic properties of these systems with emphasis on the effects, theoretical conclusions and restrictions imposed by the lack of scale separation.
Curve fitting by Lagrange interpolation
Authors: Bäckström G.
Published: July 2002

It is demonstrated that interpolation by quadratic polynomials using the Lagrange formula may compete in accuracy with cubic spline interpolation, while being simpler to implement. It is also shown that Lagrange interpolation may easily be used to fit an almost arbitrary function to experimental data. FORTRAN routines for Lagrange interpolation as well as Lagrange fitting are supplied separately.
Dielectric relaxation and the Davidson–Cole distribution function
Authors: Gross Bernhard
Published: July 2002

The relation between the distribution functions of relaxation times of equivalent Maxwell and Wagner systems is discussed. The distribution function of a Wagner system is calculated under the assumption that the distribution of the equivalent Maxwell system is given by the Davidson–Cole function.
Monte Carlo simulation of channeling tails formation under heavy-dose ion bombardment
Authors: Mazzone A. M.
Published: July 2002

This work presents a Monte Carlo simulation of the ion distribution and of the damage growth in phosphorous-implanted silicon. The calculation shows that channeling tails may form at doses well above the threshold for the formation of a continuous amorphous layer.
Room-temperature oxidation of Ni, Pd, and Pt silicides
Authors: Cros A. , Pollak R. A. , Tu K. N.
Published: July 2002

The room-temperature oxidation of Ni, Pd, and Pt silicides has been studied using electron spectroscopy for chemical analysis. It has been found that (1) Si atoms oxidize predominantly, (2) the oxidation of Si is enhanced in the metal-rich silicides, and (3) the growth of the surface oxide layer leaves behind a phase enriched with metal.
Photoemission measurements of graded barrier in thin silicon oxynitride films
Authors: Emanuel M. , Faigon A. , Shappir J.
Published: July 2002

Photoemission measurements were performed on metal-insulator-silicon structures having thin thermal oxynitride films as the insulator. The results for the sample with the least oxidized nitride film, yield for the energy intervals from the insulator conduction band to the Fermi level of the aluminum and to the valence band of the silicon, the values of 3.3 and 3.6 eV, respectively. The affinity of the insulator as deduced from these values is larger at the silicon interface than at the aluminum interface by 0.8 eV, indicating that the film exhibits a graded energy barrier for electron injection from the electrodes.
Effect of solar-cell junction geometry on open-circuit voltage
Authors: Weizer V. G. , Godlewski M. P.
Published: July 2002

Simple analytical models have been found that adequately describe the voltage behavior of both the stripe junction and the dot junction grating cells as a function of junction area. While the voltage in the former case is found to be insensitive to junction area reduction, significant voltage increases are shown to be possible for the dot junction cell. With regard to cells in which the junction area has been increased in a quest for better performance, it was found that (1) texturation does not affect the average saturation current density J0, indicating that the texturation process is equivalent to a simple extension of junction area by a factor of (3)1/2 and (2) the vertical junction cell geometry produces a sizable decrease in J0 that, unfortunately, is more than offset by the effects of attendant areal increases.
Small signal time-of-flight transients
Authors: Grunwald H. P.
Published: July 2002

The behavior of a pulse shaped charge disturbance injected into a low-conductivity semiconductor in the presence of traps is investigated. The statistical moments are used to characterize the charge distribution curve as a function of position and time under the condition of a constant electric field. In the limit when the first and second moments are sufficient to characterize the charge distribution an explicit expression for the small signal transient waveform is given and discussed.
Effects of H2O on the SiO2-HgCdTe interface
Authors: Wilson J. A. , Cotton V. A.
Published: July 2002

The effects of water on the electrical and mechanical properties of the PhotoxTM-HgCdTe interface were investigated using capacitance-voltage techniques (1 MHz an quasi-static) and a simple scratch test, in conjunction with Fourier spectroscopy to monitor actual water content. PhotoxTuM is a form of SiO2 deposited by a low-temperature (<100 °C) chemical vapor reaction. The water which is available as a byproduct of the deposition reaction becomes incorporated in the layer, with the amounts depending on deposition rate, as SiOH, H2O, and SiH...O It is seen that SiH increases with rate while SiOH and H2O decrease. After long periods (1 year) of atmospheric exposure, the SiH concentration goes to zero. In fact, layers deposited at higher rates in some ways come to spectrally resemble the lower deposition rate layers. The increased SiOH concentrations of the lower deposition rate layers result in better mechanical integrity of the interface. These rate-dependent concentrations do not affect interface electrical properties. However, it was seen that water absorbed after the layer was deposited strongly affected electronic structure, increasing interface state density between the valence band and midgap and increasing the net interface charge by up to +1×1011 cm−2. These effects are reversible with the initial interface structure recovered after a low-temperature vacuum bake.
Impurity scattering effects on electron transport in short GaAs channels
Authors: Singh Jasprit , Bajaj K. K.
Published: July 2002

As high-speed requirements for field-effect transistors (FETs) force the active channel regions to become shorter, the doping in the channel is expected to be increased to maintain a high aspect ratio and gate voltage control in the device. In this paper we have examined electron transport in submicron GaAs FET channels with varying degrees of doping. We find that impurity scattering has a strong effect on electron transport, not only at low electric fields but also at high fields when the channel length is less than a micron. These results are different from those in long channels where at high fields (≥4 kV/cm) impurity scattering is relatively unimportant. We find, for example, that for a 0.25 μm channel, the peak velocity decreases from 4.9×107 cm sec−1 for undoped channel to 3.7×107 cm sec−1 for a doping of 8×1017 cm−3. Results are presented for 0.25- and 0.5-μm channels and compared to those for a 2-μm channel.
Hole injection into single- and polycrystalline silicon electrodes
Authors: Sears W. M.
Published: July 2002

The purpose of this paper is to examine hole injection into either the valence band of single-crystal silicon or into the grain-boundary levels of polycrystalline silicon from various oxidizing ions in solution. The results for single crystals did not follow the simple picture one gets from comparing the redox potentials to the position of the silicon valence band edge. It is concluded that the band edges are shifted up by a hydride layer on the silicon surface. A solution of ferric EDTA (ethylene diamine tetraacetic acid) and 1% HF did not exhibit injection into the valence band and was used to test for hole injection into grain-boundary levels. This grain-boundary injection was definitely observed but exhibited a marked time dependence (decay). This is best interpreted as a form of hydrogen passivation (by the cathodic injection of protons).
Channel doping profile of silicon-on-sapphire transistors
Authors: Lin Alice L. , Maddox Roy L. , Mee Jack E.
Published: July 2002

Dopant profiles of low-dose channel implant in silicon-on-sapphire (SOS) field-effect transistors are investigated by comparing results from various techniques, including theoretical calculation by the Stanford University integrated-circuit process simulation program (suprem) and experimental measurements by secondary ion mass spectrometry (SIMS), capacitance-voltage (C-V), spreading resistance and metal-oxide-semiconductor Hall effect. It is shown that, for both phosphorus- and boron-implanted SOS films having constant doping profile at a level close to 1×1016 cm−3, as predicted by suprem and measured by SIMS, the charge density measured by C-V technique and free carrier concentration obtained from spreading resistance technique decrease with increasing distance from the Si surface. For SOS films implanted to a level greater than 1× 1017 cm−3 boron, the dopant profile obtained by SIMS analysis coincides with the charge density profile, measured by C-V technique, and the free carrier concentration profile, deduced from spreading resistance, and the actual mobility in SOS films.
Consequences of anion vacancy nearest-neighbor hopping in III-V compound semiconductors: Drift in InP metal-insulator-semiconductor field-effect transistors
Authors: Van Vechten J. A. , Wager J. F.
Published: July 2002

Diffusion experiments of Zn doped III-V superlattice structures have given strong evidence that the hopping of anion vacancies to nearest-neighbor sites, on the cation sublattice, is an important mode of atomic diffusion. A consequence of such hopping is the conversion of a donor state of the anion vacancy to multiple acceptor states of the cation vacancy-antisite defect complex that results. When a device is switched from depletion to accumulation, such hopping allows the material to adjust its defect distribution to a new equilibrium in the presence of the field. We show that observations of drift in InP metal-insulator-semiconductor field effect transistors, MISFETs, are consistent with this origin.
Effect of material strength on the relationship between the principal Hugoniot and quasi-isentrope of beryllium and 6061-T6 aluminum below 35 GPa
Authors: Moss William C.
Published: July 2002

Quasi-isentropic (QI) compression can be achieved by loading a specimen with a low strain rate, long rise time uniaxial strain wave. Recent experimental data show that the quasi-isentrope of 6061-T6 aluminum lies a few percent above the principal Hugoniot, that is, at a given specific volume, the QI stress exceeds the principal Hugoniot stress. It has been suggested that this effect is due to material strength. Using Hugoniot data, shock-reshock, and shock-unload data for beryllium and 6061-T6 aluminum, we have constructed the quasi-isentropes as functions of specific volume. Our results show that the QI stress exceeds the principal Hugoniot stress above a Hugoniot stress of 8.4 GPa in beryllium, and between Hugoniot stresses of 3.8 and 21.4 GPa in aluminum. The effect is due to strength and implies that the QI yield strength can be large. Our calculations show that the QI yield strength is 0.9 GPa in aluminum at a QI stress of 9 GPa, and 5.2 GPa in beryllium at a QI stress of 35 GPa.
Visible and ultraviolet reflectivity of Hg1−xCdxTe
Authors: Koppel P.
Published: July 2002

The reflectivity and wavelength-modulated reflectivity of Hg1−xCdxTe samples were measured in the 2.0–8.8 eV energy range to determine the dependence of the spectral features E1, E1+Δ1,A, and B on composition and on temperature. Spectral features of mechanically polished surfaces and sputter-etched surfaces were broadened, decreased in magnitude, and shifted to lower energies than those features of Br2-etched surfaces. At low temperatures, the spectral features of chemically etched surfaces narrow appreciably more than polished or sputter-etched surfaces, indicating that at room temperature there is a large thermal contribution to the width of the spectral features of chemically etched surfaces.
Field electron emission properties of TiC single crystals
Authors: Fujii Kiyoshi , Zaima Shigeaki , Shibata Yukio , Adachi Hiroshi , Otani Shigeki
Published: July 2002

Very stable field electron emission from TiC single crystals was observed. No current fluctuations were included in an emission current of 10 μA in a vacuum of 10−8 Pa. Step- and spike-like current fluctuations were slightly included when the emission current was large. The frequency and the amplitude of the current fluctuations were largely dependent on the sorts of the residual gas molecules. For instance, when the total emission current was 10 μA, no current fluctuation was included in 10−6 Pa of H2; on the other hand, fluctuations of several percents were included in 10−7 Pa of O2.
Fabrication and measurement of cylindrical Nb3Ge rf SQUIDs
Authors: Kuriki S. , Suehiro M. , Konishi H.
Published: July 2002

Nb3Ge thin-film microbridges are fabricated on a cylindrical substrate to form rf SQUIDs. High temperature operations well above 10 K (up to 17.5 K) are obtained. An intrinsic flux noise of the order of 10−4 Φ0/(Hz)1/2 is estimated from the step rise parameter. Comparison with a theoretical noise indicates a nonsinusoidal current phase relation of the microbridge.
Electronic contribution to the elastic constants of niobium with hydrogen impurity
Authors: Kim Chul Koo , Nahm Kyun
Published: July 2002

The change in the electronic contribution to the elastic constants of Nb due to hydrogen impurity has been evaluated using a distance-dependent tight-binding parametrization scheme. The good agreement between the calculated results and the experimental data clearly demonstrates that the positive change of C44 observed in niobium with hydrogen impurity originates from the electronic contribution.
Correlation between intensity noise and longitudinal modes of a semiconductor laser coupled to an external cavity
Authors: Fujita T. , Ohya J. , Serizawa H. , Sato H. , Fujito K.
Published: July 2002

Correlation between intensity noise and fine structures of longitudinal modes in a semiconductor laser coupled to an external cavity has been investigated. It is experimentally shown that the intensity noise is perfectly suppressed when the laser oscillates in ‘‘pure’’ single frequency oscillation even with strong optical feedback. Intensity noise, which arises only when several external cavity modes exist, is interpreted in terms of the time-dependent refractive index in the semiconductor cavity caused by the light beatings among the lasing modes.
Crystallography and optical energy gap values for AgGa(Se1−zTez)2 alloys
Authors: Chatraphorn Sompong , Panmatarite Tongchai , Pramatus Supanich , Prichavudhi Achara , Kritayakirana Rungsri , Berananda Jong-Orn , Sa-yakanit Virulh , Woolley John C.
Published: July 2002

Polycrystalline samples of AgGa(Se1−zTez)2 alloys were prepared by a melt-and-anneal technique, annealing at 650 °C for up to 4 months being required to give good equilibrium conditions. It was confirmed that single phase solid solution occurs at all values of z and values of lattice parameters a, c, and c/a were determined from Guinier–Haegg powder photographs. Line intensities were obtained from diffractometer measurements and, hence, values of the anion displacement u determined as a function of z. Comparison of these experimental data has been made with the expressions proposed by Abrahams and Bernstein and by Jaffe and Zunger. The values of u from the former equation show rather poor agreement, particularly at the AgGaSe2 end of the composition range. However, the equations of Jaffe and Zunger, used with Phillips radii, give very good agreement for both u and a but poorer agreement for c and c/a. The optical energy gap E0 is found to show a parabolic variation with z. Comparison with seven similar alloy systems shows that the E0 versus composition curve is bowed for mixed-anion alloys but practically linear for mixed-cation alloys.
Theoretical investigation of the traveling wave excitation in a TE N2 laser
Authors: Chang S. H. , Teii S.
Published: July 2002

Theoretical investigation of traveling wave excitation using the property of photon addition has been carried out in a 50-cm-long TE N2 laser tube with ten separated discharge sections. The laser power outputs under traveling wave excitation have been calculated numerically with varying gas pressures from 30 to 85 Torr and applied voltages from 14 to 21 kV, and compared with those of simultaneous excitation. Theoretical results show that the laser peak power increases with increasing applied voltage, and has a maximum value at gas pressure P≂60 Torr. The laser pulse width is narrowed and the laser power is doubled under the traveling wave excitation, compared with simultaneous excitation. Experimental confirmation also has been conducted. Experimentally observed gas presssure dependence of output power agrees qualitatively well with theoretical results. The maximum discrepancy in the absolute values between theory and experiment is approximately 50%.
A potential representation of the differential equations of C∞ anisotropic elastic bodies
Authors: Obata Tsunehiro , Chiba Jiro
Published: July 2002

We give a potential representation to the differential equations of elastic waves propagating along the symmetric direction of C∞ anisotropic elastic bodies. The potential representation is a generalization of Lamb’s potential representation of the differential equations of isotropic elastic bodies. The generalized Lamb’s potential representation reduces the equations of motion to some two-dimensional Helmholtz equations and constraint equations. Moreover, using the potential representation, we briefly prove the completeness of Mirsky’s solutions of C∞ anisotropic solid and hollow circular cylinders.
The reflex switch: A new vacuum opening switch for use with magnetic energy storge
Authors: Creedon J. M. , Demeter L. J. , Ecker B. , Eichenberger C. , Glidden S. , Helava H. , Proulx G. A.
Published: July 2002

A new type of high-power, high-voltage vacuum opening switch is described. This switch has been used in a magnetic energy storage system with a peak current of 340 kA to produce a 2.7-MV pulse with a risetime of ∼15 ns.
Collision frequencies between charged and neutral particles in a magnetic field
Authors: Imazu Shingo
Published: July 2002

It is shown theoretically how much the magnetic field influences the collision frequencies between charged and neutral particles. The magnetic field B for the usual field strength does not affect the collision cross section. However, the respective charged particles gyrate around the field lines, and then the relative velocity between charged and neutral particles changes with B. Consequently, it is shown that, when the mean free path λ is large compared with 2πrL, the velocity component contribution to the collision is the velocity component due to the motion along the field axis and not that due to the gyration. Here, rL is a Larmor radius.
Fixed pattern noise in the solid-state imagers due to the striations in Czochralski silicon crystals
Authors: Senda K. , Hiroshima Y. , Matsumoto S. , Kuriyama T. , Susa M. , Terakawa S. , Kunii T.
Published: July 2002

The concentric circle pattern of growth striations in Czochralski (CZ) silicon wafer has been found to cause the fixed pattern noise in the reproduced image by solid-state imagers with the p-well structure. The microgrowth striations of dopant impurities in 4-in. n-type CZ silicon wafers have been examined in terms of noise video signals of p-well Charge Priming Device imagers. Striation periods as narrow as 10 μm can be revealed, which may be overlooked by the conventional spreading resistance method.
Effects of plastic deformation on magnetically induced ultrasonic wave velocity changes in steel
Authors: Kwun H.
Published: July 2002

Effects of a uniaxial tensile plastic deformation on magnetically induced velocity changes for 10-MHz ultrasonic longitudinal waves in a specimen of SAE 4340 steel were investigated. The velocity change as a function of the applied magnetic field, measured after plastic deformation under uniaxial tension, was found to be similar to that obtained under uniaxial compression before deformation, suggesting the presence of a residual compressive stress in the plastically deformed specimen. This finding agrees with other reported results.
The critical field for donor-acceptor twins in silicon
Authors: Cerofolini G. F. , Polignano M. L. , Savoini E.
Published: July 2002

Donor-acceptor twins in silicon can exist only in zones where the electric field exceeds a critical value. This hypothesis removes some anomalies in the description of current-voltage characteristics of almost ideal silicon p-n junctions. The critical field seems to depend upon the final anneal temperature—about 2×104 V/cm for an anneal at 950 °C and of the order of 4×103 V/cm for anneals at 800 and 650 °C.
Influence of hydrogen implantation on the resistivity of polycrystalline silicon
Authors: Chen D. L. , Greve D. W. , Guzman A. M.
Published: July 2002

The grain boundary passivation effect in polycrystalline silicon (polysilicon) thin films by hydrogen implantation has been studied. Boron-doped polysilicon was implanted with low-energy ions followed by low-temperature annealing. Resistivity measurements show that the change in resistivity after implantation depends on the boron concentration in polysilicon. At low boron concentration (<1×1019 cm−3), three orders of magnitude decrease in resistivity has been achieved. However, at higher boron concentration (>1×1019 cm−3), the resistivity increased after hydrogen implantation. This increase is ascribed to implant-induced damage which cannot be totally recovered by low-temperature annealing.
Receiver sensitivities of Ga0.47In0.53As photoconductive detectors
Authors: Chen C. Y.
Published: July 2002

Photoconductive detectors have emerged to beome an important technology for lightwave communication since the recent demonstration of a Ga0.47In0.53As detector having a receiver sensitivity better than that of a Ga0.47In0.53As p-i-n photodiode. This study shows that the receiver sensitivity of a photoconductive detector compares fairly well with that of a p-i-n photodiode (CT=1.0 pF) in the multigigabit rate regime. The calculated result is within 1.4 dB of our measurement data at 1 Gb/s, λ=1.3 μm for a bit error rate of 10−9. This study further illustrates that noise in an undoped GaInAs photoconductive detector/field effect transistor front end system is dominated by the detector for bit rates less than 3 Gb/s.
Infrared photoionization of interface states in Cr-SiO2-(n,p)Si structures
Authors: Sharma Umesh , Dahlke Walter E.
Published: July 2002

Transient photocurrents caused by subband-gap illumination of n- and p-Si metal-oxide-semiconductor structures were measured and analyzed. The obtained interface state density distribution Dit did agree with that from electrical measurements. Electron and hole photoionization cross sections, σ0n,p ≂10−18 cm2, increased monotonically with rising photon energy, hν<EG, and with trap energy approaching the corresponding silicon band edge. Optical occupancy, relaxation time of, and electron-hole pair generation in interface states, calculated for high illumination as functions of photon and trap energy, are sufficient to model the photocurrent.
Explaining the saturation of potential drop on the high side of a grossly asymmetric junction
Authors: Warner R. M. , Schrimpf R. D. , Wang P. D.
Published: July 2002

It is shown that electric field at a strongly inverted or accumulated surface is uniquely related to surface potential, and is independent of other variables such as substrate doping and (in the metal-oxide-semiconductor context) insulator thickness or permittivity. Equivalently, junction potential is a sufficient determinant of the analogous electric-field value in a grossly asymmetric junction, and this value is unaffected by forward bias and modest reverse bias. The field value in question is exponentially related to junction (or surface) potential, and this fact combined with the field-continuity requirement and analytic treatment of high-side field explains the saturated high-side potential drop of kT/q.
Modulation-doped structures with graded heterointerfaces
Authors: Grinberg A. A. , Shur M. S.
Published: July 2002

The energy subbands of the two-dimensional electron gas in the potential well at the heterointerface of the AlGaAs/GaAs heterostructures are calculated for different grading of AlGaAs composition. The concentration nso of the two-dimensional gas in the AlGaAs/GaAs modulation-doped structures with graded heterointerface is shown to increase with the increase in the grading length WGR at small values of WGR. At large values of WGR nso starts to decrease because of the diminishing interface peak of the conduction-band edge. Depending on composition and doping of the AlGaAs layer, the maximum value of nso is achieved for WGR between 20 and 70 Å. An increase in the concentration of the 2-D gas may lead to a larger device transconductance and to a large current swing. The obtained results indicate that extremely sharp heterointerfaces are not required for modulation-doped devices.
Determination of aluminum-silicon dioxide and silicon-silicon dioxide barrier heights in a metal-tunnel insulator-silicon system
Authors: Duong A. K. , Nassibian A. G.
Published: July 2002

Using the switching characteristic of a metal-tunnel oxide-semiconductor thyristor, a new method is developed to determine the tunneling transmission coefficient through a thin oxide layer and the aluminum-silicon dioxide and silicon-silicon dioxide potential barrier heights in the metal-tunnel insulator-silicon system. The effects of the surface state charge and large bias voltage on the tunneling transmission coefficient are discussed. It is found that the tunneling transmission coefficient and the aluminum-silicon dioxide and silicon-silicon dioxide potential barrier heights are very sensitive to the oxide thickness.
Detection of magnetite particles in coal by ferromagnetic resonance
Authors: Malhotra V. M. , Graham W. R. M.
Published: July 2002

The techniques of ferromagnetic (FMR) and electron paramagnetic resonance have been applied in studies of a specimen of Pittsburgh No. 8 bituminous coal. The specimen has been found to be magnetically very heterogeneous, with paramagnetic Mn2+ and Fe3+, free radicals, and at least one ferromagnetic specie which is identified and characterized in the present paper. The temperature dependence of the spectral line shapes indicates the occurrence of a phase transition at 123 K for a finely ground powder sample and at 121 K for a hand-picked fragment; these temperatures are characteristic of the Verwey transition magnetite, and confirm its presence in both samples. Linewidth data provide an upper limit of 0.07 μm on the particle size in the powdered sample. The chemical composition of the magnetite in the powdered sample is estimated, on the basis of the observed transition temperature, to be between Fe2.988O4 and Fe2.997O4. Spectra of the residue and the glass extract obtained after treatment of the powdered sample with HCl confirm the identification of magnetite, and indicate that it is not embedded in the organic matter in the coal, but should be easily removed either by acid treatment or magnetic separation. The results of this study suggest the potential usefulness of the FMR technique in the identification and physical and chemical characterization of ferro- and ferrimagnetic minerals in coals.
High-resolution luminescence studies of indium phosphide under ohmic contacts
Authors: Graham R. J. , Myhajlenko S. , Steeds J. W.
Published: July 2002

Cathodoluminescence (CL) has been used to investigate the nature of n-type InP directly underneath AuGeNi ohmic contacts subjected to various heat treatments. The study of this contact system by CL has shown directly that the quality of the underlying InP is significantly modified up to distances of several microns from the contact interface. These changes are brought about by the interaction of the contact components with the semiconductor. Contrary to the widely accepted view, no evidence of n+ doping of the InP by Ge was observed in any of the contacts examined. Possible explanations for the observed reduction in CL efficiency obtained from the InP close to the contact interface are discussed.
Detection sensitivity and spatial resolution of reverse-bias pulsed deep-level transient spectroscopy for studying electric field-enhanced carrier emission
Authors: Li G. P. , Wang K. L.
Published: July 2002

Reverse-bias pulsed deep-level transient spectroscopy (RDLTS) has recently been used for studies of electric field-enhanced emission from a deep-level defect. The sensitivity, spatial, and temperature resolutions of this technique are investigated and compared with those of DLTS. The electric field strength in a narrow region, where the transient capacitance signal comes from, can be accurately controlled by using RDLTS. The calculated results indicate that there is an optimal operating condition given by a range of emission pulse widths and heights. This operating condition is given for the best compromise of the temperature and spatial resolutions.
Effects of divalent anionic impurities on space charge in AgBr microspheres
Authors: Hunter J. E. , Hoyen H. A. , Tan Y. T.
Published: July 2002

The model of the space-charge layer in AgBr microcrystals containing divalent cationic impurities has been extended to divalent anionic dopants. Results of calculations for both mobile and immobile impurities are reported. Increasing the impurity concentration leads to a change in the potential difference between the interior and the surface, which in some cases may reverse the sign of the space-charge layer and the compensating surface charge. The point at which this occurs is dependent on the binding energy of the impurity-interstitial complex and on the temperature.
Enhanced high-field current carrying capacities and pinning behavior of NbTi-based superconducting alloys
Authors: Wada H. , Itoh K. , Tachikawa K. , Yamada Y. , Murase S.
Published: July 2002

High-field critical current densities Jc and pinning behavior are discussed for Nb-63a/oTi, Nb-61.7a/oTi-3a/oHf, and Nb-64.7a/oTi-7.2a/oTa superconducting alloys. Jc properties for 8–12 T in these alloy superconductors under superfluid helium environments can be even superior to those in Nb3Sn at 4.2 K, when they are heavily cold-worked after final heat treatments. A temperature scaling law of the flux pinning force Fp is found to hold for these alloys in the form of FP=K [Bc2(T)]nbp(1−b)q, where Bc2 is the upper critical field and b≡B/Bc2. The peak reduced field, bm, in the Fp−b curve depends upon how the alloys have been processed. The origins of n, p, and q are discussed in terms of the processing condition.
Measurement of the deuterium concentration profile in a deuterium-exchanged LiNbO3 crystal
Authors: Rice C. E. , Jackel J. L. , Brown W. L.
Published: July 2002

We have measured the concentration of deuterium as a function of depth in a deuterium-exchanged LiNbO3 sample using nuclear analysis. From the shape of the concentration profile we calculate the concentration dependent effective diffusion coefficient for deuterium-lithium counterdiffusion. Comparison of the concentration and refractive index profiles for this waveguide confirms that the index increase in exchanged material is a nonlinear function of concentration. We discuss implications of these results for optical waveguide fabrication.
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K-cut quartz resonators
Authors: Kahan Alfred , Euler Ferdinand K.
Published: July 2002

We calculated the turnover temperatures Tto of crystallographically doubly rotated quartz plates vibrating in the thickness mode. In addition to the known cuts situated along the loci of zero value of the first-order temperature coefficient of frequency, there is another family of orientations, with Tto≥75 °C, which, compared to other singly or doubly rotated cuts, are relatively insensitive to crystallographic orientations. We designate these orientations as the AK cut. We report experimental static frequency as a function of temperature characteristics f(T) for 14 AK-cut orientations, with angular combinations 30°≤φ≤46.1° and 21° ≤θ≤28.44°. Tto values are between 80 and 150 °C, in good agreement with computations. The f(T) curves have been fitted with third-order polynomials. Compared to the fundamental mode of vibrations, the 3rd overtone shows a larger number of modes, and resonance amplitudes are weaker. The frequencies of the harmonic and anharmonic modes are in fairly good agreement with calculations based on a trapped energy resonator model, including effects of coupled thickness shear and thickness twist.
Photoacoustic cell for use as an optical power meter
Authors: Guthrie R. W. , Medina F. D.
Published: July 2002

A new photoacoustic cell has been constructed to measure laser beam power. The sample, a thin brass disk, is on the front of the cell in place of the conventional window. For the thickest sample used (127 μm), the cell response was found to be linear with laser beam power up to 1.8 W, the maximum power delivered by the laser.
Agglomeration of magnetic fine particles in fluid dispersion
Authors: Vogelgesang P. J. , Charap S. H. , Bortz A. B.
Published: July 2002

Agglomeration of γ-Fe2O3 acicular magnetic particles in concentrations of approximately 0.005% by weight in water was studied by measuring light transmission through the dispersions while they were subjected to a stepwise rotating magnetic field of 15-Oe magnitude. Transmitted light intensity varies synchronously with rotation, having its minimum when particles are aligned with their long axes parallel to the light and its maximum when particles are perpendicular to the beam. With time, the minimum light level diminishes, whereas the maximum light condition remains constant. This behavior is attributed to the formation and growth of particle chains. The chaining idea is supported by the observation that the response time of particles to the changing field increases with time and by other optical effects which are observed in high-speed rotation of the field. The effect of milling time on particle mobility is also observed. The observations are discussed in terms of a model of the attraction and attachment behavior of dilutely dispersed magnetic particles in a fluid.
Contribution of interparticle forces to the buildup of ultrafine colloidal particles around a magnetized fiber
Authors: Fletcher D. , Parker M. R.
Published: July 2002

The influence of interparticle double-layer and dipole-dipole forces on the buildup of ultrafine colloidal particles around a magnetized collection center in a static colloid is considered. Expressions are given and developed, respectively, that describe the double layer and dipole-dipole interparticle effects in a one-dimensional particle number gradient. These expressions lend themselves to a description of the effects by a double-layer diffusion and a dipole-dipole flocculation coefficient. The size of these coefficients and of the normal thermal diffusion coefficient is compared over a wide range of colloidal particle radius, and ranges of radius are identified in which each coefficient can be dominant. Steady-state solutions of the transport equation including these coefficients are computed and show that this inclusion can be justified, and is indeed necessary, for significant ranges of particle radius.
An advanced kinetic model of electron-beam-excited KrF lasers including the vibrational relaxation in KrF*(B) and collisional mixing of KrF*(B,C)
Authors: Kannari Fumihiko , Obara Minoru , Fujioka Tomoo
Published: July 2002

Computer models developed so far on electron-beam-excited KrF(B–X, 248 nm) lasers that include the vibrational relaxation process in the upper lasing B level at the finite rate could not predict the high intrinsic laser efficiency which was experimentally reported. This is attributed to the reduction of the laser extraction efficiency. We have developed a four-level KrF laser model that includes the vibrational relaxation process and also the collisional mixing of the KrF*(B) and the KrF*(C) levels. The collisional quenching rates for KrF*(B,C) that we used and the vibrational relaxation rate were carefully estimated by using the effective spontaneous lifetimes for KrF*(B,C). As a result, the model prediction was in quite good agreement with many experimental results for a saturation behavior of KrF*(B–X) fluorescence, for small-signal gains, for small-signal absorptions, and for intrinsic efficiencies. Estimated rate constants in this model for the vibrational relaxation and the KrF*(B,C) mixing are 4×10−11 and 5×10−10 cm3/s, respectively, for a two-body collision rate with argon gas.
Theory for shot noise in submicron semiconductor diodes using two-point correlations of noise sources
Authors: Chatterjee A. , Das P.
Published: July 2002

In this paper the shot noise process is reformulated in terms of spatial correlation functions. In ‘‘ballistic’’ devices local noise sources remain correlated for separation distances on the order of device dimensions. The effect of randomizing collisions, is introduced as a decay of this correlation. The velocity distribution of carriers is taken into account. The effect of parameters such as injection velocity, scattering probability, and device length on noise in near-ballistic devices could be calculated using this method.
Domain wall dynamics and relaxation through the frequency dependence of hysteresis loops
Authors: Guyot M. , Merceron T. , Cagan V.
Published: July 2002

The frequency dependence of hysteresis loops of high purity yttrium iron garnet (YIG) polycrystals has been measured over the range of temperature and frequency where the permeability spectrum has evidenced significant dispersion. Very close to Tc, the effect of domain wall damping results in elliptical loops when the wall relaxation frequency is approached. The observed increase in losses with frequency implies values of the wall damping parameter β which agree with previous determinations from permeability data. In the 150 K range, migrating electrons due to the voluntary slight iron deficiency of the studied sample cannot follow fast wall motions and relax, which in turn produce more rectangular loops for frequencies above the diffusion relaxation frequency. The corresponding increase in hysteresis losses is due to an increase in the wall energy γ and possible dynamical changes of the domain wall configuration in the sample.
Coercivity, structure, and stoichiometry of Permalloy/alumina multilayers
Authors: Jubb N. J. , Davis R. E. , Reith T. M. , Kolar H. R. , Leavitt J. A.
Published: July 2002

A series of permalloy/alumina multilayers were examined to determine their structure, composition, and magnetic performance. The conditions of permalloy and alumina-layer thickness, and substrate bias necessary to minimize the coercivity have been shown. Multilayer structures with alumina-layer thicknesses of less than 100 Å and permalloy-layer thicknesses between 400 and 500 Å had the lowest coercivities. Structures were examined by RBS, TEM, AES, and XRD to study the effect of bias sputtering on the structure and composition of the multilayers. It was found that sputtering multilayers at high biases did not affect the coercivity, but did cause significant physical and chemical changes.
The effects of forsterite film on total loss of grain-oriented 3% silicon iron
Authors: Konno T. , Suga Y. , Nozawa T. , Honma K.
Published: July 2002

Two types of mill glass, one of which is conventional and the other is characterized by its irregular surface morphology and stronger tension, were prepared on the surface of high permeability 3%Si-Fe sheets in order to clarify the effects of the mill glass on core loss and domain structure. The results are twofold. Firstly, the mill glass of the latter type was, by itself, found to reduce the total loss in the induction range of 1.7 T. Secondly, considerable change in magnetization, characterized by its heavily constricted curve occurred, and corresponding change in the domain structure was observed.
Effect of aluminum content and processing on texture and permeability of lamination steels
Authors: Lyudkovsky G. , Shapiro J. M.
Published: July 2002

Increasing aluminum content from 0.02 to 0.10%, lower reheat temperature, higher coiling temperature, and hot band annealing all promote a reduced proportion of the (111) texture component and higher permeability in box annealed, semiprocessed lamination steel. These results are consistent with observations of  a greater degree of precipitation of AlN in the hot band.
A NMR and Mössbauer study of Nd2Fe14B
Authors: Rosenberg M. , Deppe P. , Wójcik M. , Stadelmeier H.
Published: July 2002

Mössbauer spectroscopy and spin echos nuclear magnetic resonance were used in order to study the hyperfine fields (HF) at the six Fe sites and the B site in Nd2Fe14B. At 4.2 K hyperfine fields and Fe magnetic moments for the different sites in the range 307–372 kOe and respectively 2.05–2.48 μB have been found. The transferred HF of 31.25 kOe at the B site has a strong local character, being determined by the six next-nearest Fe atoms in the corner of the trigonal prism in which B atoms are located.
Application of the recursion method to calculation of the local moments in Nd2Fe14B
Authors: Szpunar B. , Szpunar J. A.
Published: July 2002

The recursion method has been used to calculate the local magnetic moment on eight different sites in Nd2Fe14B. The origin of the ferromagnetic arrangement between Nd and Fe moments has been explained. The results are discussed in the light of previous calculations for intermetallic compounds.
Mössbauer studies in rapidly quenched rare-earth iron boron alloys (abstract)
Authors: Niarchos D. G. , Dunlap B. D. , Hadjipanayis G. C. , Jones D. R.
Published: July 2002

Rapidly quenched rare-earth (R)-iron boron alloys show large magnetic hysteresis when annealed around 700 °C. The hard magnetic properties of these alloys have been attributed to the presence of an anisotropic tetragonal phase with composition R2Fe14B. However, it is not yet clear when this phase is formed and how it affects the hard magnetic properties. Thermal analysis data, show a crystallization temperature around 400 °C which is much lower than the annealing temperature for the optimum properties. X-ray diffraction data do not show any significant changes after crystallization. In the present study we have used the Mössbauer effect to probe the products of crystallization and their changes during further annealing. Analysis of the 57Fe Mössbauer data has been performed considering a distribution of hyperfine magnetic fields. It is found that the average field changes from 250 kG for the amorphous alloy to 285 kG for the alloy annealed at 450 °C to 240 kG for the alloy annealed at 700 °C. The distribution is narrowed on increasing the annealing temperature and the Mössbauer spectra are indicative of phase segregation.
The temperature dependence of the magnetic properties of commercial magnets of greater than 25 MGOe energy product
Authors: Potenziani II E. , Leupold H. A. , Clarke J. P. , Tauber A.
Published: July 2002

The hysteresis loops of three commercial magnets with room temperature energy products greater than 25 MGOe were obtained over the temperature range 4.2–700 K in applied magnetic fields extending to ±90 kOe. Two of the samples are of the Sm2Co17 type and the other of Nd2Fe14B. The magnetic parameters extracted from the hysteresis loops are compared with each other and with those of a previously measured 2-17 specimen. The temperature dependencies of intrinsic coercivities and remanences of the 2-17’s are similar, as are the magnitudes of the remanences. However, the magnitudes of the intrinsic coercivities differ greatly. For example, at 300 K they are 6.4, 13.4, and 24 kOe, a ratio of approximately 1:2:4. The value for Nd2Fe14B is 11.3 kOe at 300 K. The temperature coefficient of coercivity ranges from −0.225%/K to −0.405%/K for the 2-17’s and −1.09%/K for Nd2Fe14B. The room temperature energy products are 26 and 27 MGOe for the 2-17’s and 32 MGOe for Nd2Fe14B. The temperature coefficients of energy product are −0.080%/K and −0.073%/K for the 2-17’s and −0.398%/K for Nd2Fe14B. The merits of the two classes of material are compared for different applications and operating conditions.
Magnetic properties of Pr-Co and Nd-Co thin films deposited by ion beam sputtering
Authors: Terada N. , Naoe M. , Hoshi Y.
Published: July 2002

Pr-Co (0–20 at. % Pr) and Nd-Co (0–20 at. % Nd) thin films have been deposited by means of ion beam sputtering. Both films deposited at substrate temperature Ts about 70 °C have amorphous crystal structure and small coercive force Hc (Pr-Co: <70 Oe, Nd-Co: <4 Oe). The amorphous Pr-Co film is crystallized by the annealing at a temperature of 600 °C and becomes to have large Hc above 2 kOe, though it should be coated with SiO thin films to prevent the oxidation of the film even if the annealing were performed in a vacuum (∼10−6 Torr). On the other hand, the Pr-Co film deposited at Ts in the range from 200 to 300 °C is a mixture of an amorphous phase with low Hc (<100 Oe) and the crystalline one with large Hc (>2 kOe). The volume fraction of the amorphous phase decreases as Ts increases, and the amorphous phase disappears in the film deposited at Ts above 300 °C. Hc of these films depends on film composition and takes a maximum value at the composition around PrCo5. Nd-Co films deposited at Ts above 250 °C have crystalline phase and show similar dependence of Hc (<300 Oe) as the Pr-Co film does, although they do not have so large Hc as the Pr-Co film has.