bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropy energy for the ordered Ni3Al crystal
Authors: Matsuzawa K. , Ukai T. , Ohtsuka S. , Mori N.
Published: July 2002

The approximate d bands for the ordered Ni3Al crystal are formulated by Deegan’s prescription and Slater and Koster’s formulas in the tight binding approximation. The electronic energies of this crystal with the spin direction parallel to [100] and 110] directions are calculated by using Gilat and Raubenheimer’s method. Then, the anisotropy constant K1 is estimated, which is in agreement with the experimental result. The temperature dependence of K1 is also discussed. It is found that the temperature variation of the Fermi level for these two states is appreciably different with each other by analyzing the experimental result, and this can be explained by the d-band structure of this crystal.
Two-band model and ground state of heavy fermion compounds
Authors: Jaccard D. , Flouquet J. , Sierro J.
Published: July 2002

Thermoelectric power (TEP) experiments on 4f  instability compounds are described down to very low temperatures. Above 1 K, the data are analyzed in a two-band model; major features are the electron-hole symmetry between cerium and ytterbium and the change of the sign on approaching the trivalent state. At very low temperature, for the trivalent heavy fermion compound CeAl3, a new inversion of the sign of the TEP is observed which is connected with the entrance in the Kondo lattice regime.
Measurement of the induced moment magnetic form factor of a heavy fermion superconductor
Authors: Stassis C. , Axe J. D. , Majkrzak C. F. , Batlogg B. , Remeika J.
Published: July 2002

Polarized neutron scattering techniques have been used to study the spatial distribution and temperature dependence of the magnetization induced in a single crystal sample of CeCu2Si2 by a magnetic field of 50 kOe. We find that at 4.2 K (>Tc), the induced magnetization is predominantly of 4f electronic character. No evidence was found of any change in the magnetic form factor between 300 and 4.2 K.
The theory of ferromagnetic superconductors (invited)
Authors: Whitehead J. P. , Matsumoto H. , Umezawa H.
Published: July 2002

Since their discovery in 1977 the rare earth ternary superconductors have provided a number of unusual phenomena regarding the interplay of magnetism and superconductivity. In the case of the reentrant superconductors ErRh4B4 and HoMo6S8 the importance of the electromagnetic interaction, in determining the physical properties of these materials, was realized shortly after their discovery. More recent single crystal data indicate that in addition to the electromagnetic interaction the d–f interaction, although weak, gives rise to a number of dramatic properties notably the appearance of a first order transition at the upper critical field Hc2. In this paper we outline a formalism which successfully incorporates both the electromagnetic interaction together with the d–f interaction in a mutually consistent manner. The results of our analysis based on this formalism are presented for the case of ErRh4B4 together with a comparison with the recent monocrystalline data.
Small-angle neutron scattering of (Er0.8Ho0.2)Rh4B4
Authors: Pringle O. A. , Mook H. A. , Maple M. B.
Published: July 2002

The (Er1−xHox)Rh4B4 pseudoternary alloy system has a minimum in the phase boundary between the superconducting and ferromagnetic phases near x=0.3. This minimum has been identified as due to the competing magnetic anisotropies of Er and Ho. It has also been suggested that there could be a Lifschitz point near the minimum. Using the 30-m SANS camera at the National Center for Small-Angle Scattering Research at ORNL, we have observed a peak in the SANS pattern for (Er0.8Ho0.2)Rh4B4 at Q=0.065 Å−1. This peak appears for temperatures between Tc2, measured upon cooling, and Tm, and corresponds to a modulation of the magnetic moment with a wavelength of about 100 Å, demonstrating that the modulated moment phase exists away from the ErRh4B4 end of the phase diagram. The wavelength of the modulation is the same as was previously observed in ErRh4B4. The fact that the wavelength of the modulation remains finite near x=0.3 appears to rule out the possibility of Lifschitz behavior near this point.
Itinerant ferromagnetism and superconductivity in bct ErRh4B4
Authors: Chaussy J. , Genicon J. L. , Lejay P. , Odin J. , Shao L. Q. , Sulpice A. , Tournier R. , Chevalier B. , Etourneau J.
Published: July 2002

The body centered tetragonal ErRh4B4 compound undergoes an itinerant ferromagnetic transition at Tm=21 K characterized by a susceptibility equal to the inverse of the demagnetizing coefficient. The itinerant ferromagnetism does not prevent the simultaneous presence of the superconductivity from 7.7 K down to 0 K. The diamagnetic ac susceptibility can be calculated from the ferromagnetic one. The coexistence of itinerant ferromagnetism and superconductivity among d electrons would be one of the most convincing arguments in favor of ‘‘odd-parity’’ superconductivity.
Anisotropic magnetic and superconducting properties of single crystals of RERh4B4 compounds
Authors: Zhou H. , Chen J. W. , Lambert S. E. , Maple M. B.
Published: July 2002

We report the synthesis of small single crystals of several RERh4B4 compounds where RE=Sm, Gd, Tb, Dy, Ho, Er, and Tm using a flux-growth technique. Measurements of the ac electrical resistance R in zero and applied magnetic fields and dc magnetic susceptibility are reported. The upper critical magnetic field Hc2(T) determined from the resistance measurements for RE=Sm, Er, and Tm are also presented. Considerable anisotropy of Hc2(T) is observed for Er and Tm, while very little is found for Sm.
Low temperature properties of CeOs2 in the C14 and C15 crystallographic Laves phases
Authors: Torikachvili M. S. , Yang K. N. , Maple M. B. , Meisner G. P.
Published: July 2002

The compound CeOs2 has been prepared in both cubic C15 and hexagonal C14 Laves phases. Measurements of ac and dc magnetic susceptibility, electrical resistivity, and specific heat have been performed on samples of both phases. The C14 phase has been found to exhibit superconductivity with a superconducting transition temperature Tc of 1.1 K, while the C15 phase does not display superconductivity above 70 mK. The curves of resistivity vs temperature for both phases exhibit strong negative curvature which are reminiscent of valence fluctuation compounds.
Suppression of ferromagnetic order in pseudobinary U1−xLaxTe compounds
Authors: Schoenes J. , Frick B. , Vogt O.
Published: July 2002

We report first magnetic, electrical, and optical measurements on UTe diluted with lanthanum. With the substitution of 10% and 20% U by La, a decrease of TC by ≊30 and ≊60 K, respectively, is observed. From an extrapolation of these data a vanishing of ferromagnetic ordering is predicted to occur in U1−xLaxTe for x≊0.25. The electrical resistivity of all compounds shows a −log T term at higher temperatures and a maximum which shifts from 140 K for x=0–90 K for x=0.2. It is concluded that the dilution with nonmagnetic lanthanum weakens the interatomic exchange between uranium atoms and that the Kondo effect suppresses magnetic ordering.
Thermodynamics of Ce and Yb impurities from the Bethe–ansatz equations of the Anderson model (invited)
Authors: Schlottmann P.
Published: July 2002

We review the Bethe–ansatz solution, the groundstate properties and the thermodynamics of the degenerate Anderson model for a magnetic impurity. The results are discussed and compared with experimental data for CeSn3.
Effects of preferential sputtering and enhanced diffusion processes on the evolution of La-implanted profile in Ni
Authors: Kulkarni V. N. , Miotello A.
Published: July 2002

An experimental profile of  La implanted in a Ni crystal is theoretically described on the basis of a continuity equation for the La concentration, which includes a diffusive relocation of the implanted atoms and the matrix erosion velocity. The La sputtering process is explicitly considered by an appropriate boundary condition. The shape of the experimental La profile as well as the measured retained La dose has been well reproduced. It is shown that the erosion velocity of La atoms is greater than that of Ni atoms by a factor of 2.
Observations on the phase transformation and its effect on the resistivity of WSi2 films prepared by low-pressure chemical vapor deposition
Authors: Fang Y. K. , Hsu S. L.
Published: July 2002

WSi2 films prepared by low-pressure chemical vapor deposition were analyzed by backscattering, x-ray diffraction, and transmission electron microscopy (TEM). The backscattering results indicate that the composition of as-deposited WSi2 films does not change during low-temperature annealing. Crystallographic observations with x-ray diffraction and TEM on similar samples before and after various heat treatments provide evidence for the low temperature of hexagonal structure of the WSi2 films. It is transformed into the usual tetragonal structure during low-temperature annealing. Through x-ray diffraction examination, the transition temperature is found to be close to 600 °C. This phase transition is correlated to changes of the film resistivity.
Magnetic phase diagrams for the dilute Cr-Sn and Cr-Sb systems
Authors: Okpalugo D. E. , Booth J. G. , Costa M. M. R. , Ziebeck K. R. A.
Published: July 2002

Magnetic phase diagrams defining the regions over which the transverse incommensurate AF1 and the longitudinal incommensurate AF2 phases occur for dilute Sn and Sb alloys of chromium have been determined using neutron diffraction techniques. The purely magnetic (100), (111), and (210) peaks have been examined over a wide range of temperature and normalized to the (110) nuclear peak. Wavelengths of 1.22 and 2.52 Å have been employed using the D2 and D1B instruments at ILL, Grenoble. In both systems the boundary between the AF0 and AF1 phases (Tco) and that between the AF1 and AF2 phases (Tsf) initially decreases as the impurity content increases, in agreement with recent resistivity results. Beyond certain concentrations no further decrease is observed, however, and this is probably associated with the formation of a second phase in these systems. The compositions examined cover the reported range of solid solutions although these are somewhat uncertain. The values of the magnetic moment, spin-density wave vector Q, and the fraction of electrons in Eg orbitals have also been determined and compared with previous results in related systems.
Magnetism in the two-dimensional Hubbard model (abstract)
Authors: Hirsch J. E. , Lin H. Q.
Published: July 2002

The Hubbard model has been widely used to describe magnetism due to itinerant electrons. However, except for the one-dimensional case, no exact solution of the model exists. We have studied the two-dimensional Hubbard model on a square lattice using a Monte Carlo simulation technique. Simulations were performed on lattices of up to 8×8 in spatial size. We will discuss results for thermodynamic properties and correlation functions as a function of temperature and interaction strength. For the half-filled band case, our results indicate that the system exhibits long-range antiferromagnetic order in the ground state for any nonzero interaction, although substantially reduced from the classical Néel state due to both charge and spin fluctuations. For the non-half-filled band case, our results suggest that no long-range magnetic order exists. We also don’t find any indication of short-ranged ferromagnetic correlations in the parameter range studied. We have also studied the predictions of various approximate treatments for this model, particularly the static approximation and the coherent potential approximation (CPA). By comparison with the Monte Carlo results, we discuss the validity of these schemes. Finally, we discuss the effect of changing the band structure on the magnetic properties of the system.
Valence band XPS study of Fe at finite temperatures
Authors: Kisker E. , Kirby R. E. , King F. K. , Garwin E. L.
Published: July 2002

Measuring the valence band density of states (DOS) of Fe provides a stringent test of models of metallic ferromagnetism at finite temperatures. The density of states of Fe above the Curie temperature TC, as obtained by self-consistent calculations in the disordered local moment (DLM) picture by Oguchi et al. and Pindor et al. differs strongly from the T=0 DOS calculated by Moruzzi et al. between the Fermi energy and 2-eV binding energy, i.e., the relatively broad peak in the T=0 DOS around 1-eV binding energy is of much smaller amplitude in the T≳TC DOS. This effect should be observable by valence band XPS on Fe as a 30% decrease of intensity at about 1-eV binding energy with a typical energy resolution of about 0.8 eV. We have measured the valence band XPS of Fe(100) at room temperature and temperatures above TC. The predicted intensity decrease has not been observed.
Spin fluctuations and superconductivity in UPt3 (invited)
Authors: Stewart G. R.
Published: July 2002

Of the three known high effective mass (‘‘heavy fermion’’) superconductors, UPt3 has quite different properties from the rather similar CeCu2Si2 and UBe13. In particular, UPt3 has a much different temperature dependence of its resistivity below 300 K, a much lower initial slope of the superconducting critical field, H′c2(Tc), a much greater dependence of the superconducting transition temperature, Tc, on lattice perfection (proportional to resistivity ratio), and a much different temperature dependence of the low temperature normal state specific heat, Cn. This temperature dependence of Cn in fact includes a T3 ln T term for UPt3, compared to approximately a T−2 dependence for UBe13 and CeCu2Si2 at low temperatures. The presence of a T3 ln T term in Cn for UPt3, coupled with the extreme dependence of Tc on lattice perfection, has led to speculation that the pairing of the superconducting electrons in UPt3 may not be between opposite spins, but between parallel spins, i.e., p-wave instead of s-wave pairing. Recently, further experimental and theoretical evidence has been found supporting this speculation that UPt3 may be a p-wave superconductor. The present work surveys the properties of UPt3, including new results on the spin fluctuation behavior in the normal state of UPt3.
Single-crystal experiments on EuMo6S8 and EuMo5WS8
Authors: Holtzberg F. , Flouquet J. , Konczykowski M. , Sulpice A. , Tournier R.
Published: July 2002

Resistivity measurements have been made on EuMo6S8 and EuMo5WS8 single crystals in the temperature range 1.5–300 K under pressures between ambient and 20 kbar. In contrast to the recently reported results on sintered or melted material, the resistivity has a metallic behavior. No semiconductor behavior is observed in either type single crystal. The strong scattering effects lead to an electronic mean free path equal to the interatomic Mo-Mo distance. The possibility of spin fluctuations associated with the molybdenum atoms is discussed. The superconductivity appears in either type crystal at about the same pressure (10 kbar).
Recombination of carriers at n-Si/SiO2 interface via mobile centers in the oxide
Authors: Kamieniecki Emil
Published: July 2002

A theory of the ac surface photovoltage is presented for the case of surface recombination of carriers via mobile centers located in the insulator in the region adjacent to the interface. The surface photovoltage relaxation time for this recombination mechanism is shown to be strongly dependent on the modulation frequency of the incident light, while the relaxation time is frequency independent if the recombination of carriers occurs via conventional, spatially fixed, surface states. The dependence of the ac surface photovoltage on the modulation frequency of the incident light was measured for n-Si/native oxide and n-GaAs/native oxide systems. The strong frequency dependence of the surface photovoltage relaxation time observed for an n-Si/native oxide system under depletion conditions indicated that the carrier recombination at this interface occurs mainly via mobile oxide centers. The relaxation time in n-GaAs/ native oxide system was found to be frequency independent, confirming previous conclusions that surface states in GaAs are associated with defects located on the semiconductor side of the interface.
Photoluminescence of AlGaAs:Ge and GaAs:Ge and Sn grown by liquid-phase epitaxy
Authors: Yuan Y. R. , Mohammed Khalid , Merz James L.
Published: July 2002

The photoluminescence of Ge-doped AlxGa1−xAs and Sn-doped GaAs were investigated at 1.4 K. The ionization energy of Ge is strongly dependent on the Al composition in AlGaAs, and is in very poor agreement with the effective mass value. The ionization energy of Sn was found to be 110 meV in contrast with previously reported values. We also report a Sn acceptor bound excitation line at 1.507 eV in Sn-doped GaAs, and a broad luminescence band peaking at ∼1.5 eV in Ge-doped AlGaAs.
Effects of indium diffusion on the properties of ZnSe:Mn dc thin-film electroluminescent devices
Authors: Kobayashi Masakazu , Mino Naoki , Konagai Makoto , Takahashi Kiyoshi
Published: July 2002

ZnSe:Mn dc thin-film electroluminescent (EL) devices were prepared by a molecular beam growth method on glass substrates coated with transparent conductive oxide. We found that the EL properties were affected by the grade of the oxide. The EL properties were found to depend on the range of indium diffusion from the oxide to the ZnSe:Mn host layer. The effective thickness of the host layer was varied by the In diffusion. Based upon these results, we have proposed a new type of dc thin-film EL cell, namely an Al/ZnSe:Mn/ZnSe:In/oxide structure. A ZnSe:In layer was prepared as a buffer layer that would improve the crystallinity of the ZnSe:Mn host layer.
Schottky-barrier heights at granular-metal/Si interface
Authors: Masaki S. , Iwase M. , Morisaki H.
Published: July 2002

Diode characteristics of granular-metal (GM)/n-Si interfaces were investigated. The granular metal film (Pd or Pt/SiO2) was deposited by the ion-beam sputtering technique. The diode characteristics were found to be influenced not only by the metal fraction in GM but also by the GM film thickness. Saturation current density Js of the diodes under reverse bias condition showed a notable peak at the metal fraction in the range between 0.1 and 0.25, the maximum value being several orders of magnitude greater than Js of a Pd-Si Schottky barrier. Assuming that the increase in Js is fully caused by the barrier-height lowering at the GM/Si interfaces, the amounts of barrier-height lowerings were found to be 0.18 eV for 150-Å-thick GM films and 0.22 eV for 600-Å-thick GM films. Possible mechanisms for the barrier-height lowering as well as the reason that the barrier height depends upon the GM films’s thickness were considered.
Epitaxial growth of silicon with Hg-Xe lamp light irradiation
Authors: Ishitani Akihiko , Kanamori Masaru , Tsuya Hideki
Published: July 2002

An epitaxial silicon film was successfully grown on a Si {100} substrate at the susceptor temperature of 730 °C in the SiH2Cl2/H2 system. Irradiation with a mercury-xenon (Hg-Xe) lamp during deposition appeared to be essential for obtaining the epitaxial film. Surface cleaning in the experiment was done by preannealing the substrate in H2 at 730 °C with Hg-Xe lamp light irradiation. The film was characterized by etching, electron channeling pattern observation, Raman scattering spectroscopy, and spreading resistance measurement.
Electron-beam-induced current measurements: Comparison of barrier:beam parallel and perpendicular geometries
Authors: Dixon A. E. , Williams D. F. , Das S. R. , Webb J. B.
Published: July 2002

Minority-carrier diffusion lengths have been measured in electron-beam-induced current experiments with the electron beam of the scanning electron microscope both parallel and perpendicular to a Schottky barrier on single-crystal silicon. Results from the two geometries are compared. The usefulness of the top surface geometry (beam perpendicular to the barrier) has been extended by measuring both the short-circuit current and its derivative as a function of position, allowing the diffusion length to be calculated without knowing the exact position of the Schottky-barrier edge. This is particularly useful when the barrier edge is indistinct, as often occurs for evaporated or sputtered barrier layers. Measurement of the derivative signal has been accomplished by position modulation of the scanning electron beam combined with a lock-in amplifier for signal detection.
Comment on ‘‘Kinetics of anisothermal phase transformations’’
Authors: Louis E. , García-Cordovilla C.
Published: July 2002

In a recent paper, Markworth and Glasser [J. Appl. Phys. 54, 3508 (1983)] claimed to have generalized the Johnson–Mehl–Avrami [W. A. Johnson and R. F. Mehl, Trans. Am. Inst. Min. Metall. Eng. 135, 416 (1939), and M. Avrami, J. Chem. Phys. 7, 1103 (1939)] equation for the anisothermal case. It is argued that these authors did in fact use different rate equations for iso- and anisothermal kinetics. This procedure could lead to large errors in the kinetic parameters. A correct solution of the problem might be found in Henderson’s paper [J. Non-Cryst. Solids 30, 301 (1979)].
Simple method of pulsed plasma discharge current analysis
Authors: Wong C. S. , Lee S.
Published: July 2002

A simple method is proposed to analyze the current waveform of a pulsed plasma discharge from which the voltage waveform and hence the temporal evolution of the plasma inductance can be deduced. As an example, the application of the method to a typical plasma focus discharge is illustrated.
Stochastic model for grain size versus dose in implanted and annealed polycrystalline silicon films on SiO2
Authors: Iverson R. B. , Reif R.
Published: July 2002

160-nm polycrystalline silicon films were implanted at room temperature with 100-keV silicon ions and subsequently annealed. The final grain size was found to increase with implant dose. A model is presented here to account for the dose dependence of the grain size. Three mechanisms were presumed to account for the final grain size: statistical variations of area coverage by the implanted ions, ion channeling, and spontaneous nucleation. Model parameters were successfully fit to the experimental data.
Radiation-induced transient acoustic loss in quartz crystals
Authors: Koehler D. R. , Martin J. J.
Published: July 2002

When exposed to pulsed ionizing radiation, quartz oscillator crystals can exhibit transient acoustic losses (a decrease in Q) and transient frequency shifts. Although these changes are usually most pronounced in unswept quartz, they have also been seen in swept quartz. We have directly measured the transient acoustic loss in both synthetic and natural quartz. The synthetic quartz samples included hydrogen and lithium swept units. Irradiations were accomplished at REBA, a flash x-ray facility at Sandia Laboratories. Log decrement acoustic loss measurements were made over the 110–400 K temperature range and show a time dependence similar to a t−1/2 behavior characteristic of one-dimensional diffusion. The transient loss showed a broad temperature dependence ascribed to alkali ions moving along the Z-axis channels. Peaks at 360 and 380 K in the transient loss temperature spectra are thought to be due to an unstable defect which momentarily traps the alkali ion.
Titanium silicidation by halogen lamp annealing
Authors: Okamoto Tatsuo , Tsukamoto Katsuhiro , Shimizu Masahiro , Matsukawa Takayuki
Published: July 2002

Silicidation of titanium (Ti) thin films sputter-deposited onto silicon (Si) was performed by the halogen lamp annealing method. This method was found to be quite effective in forming oxide-free and homogeneous titanium disilicide (TiSi2). Temperature dependence of silicidation was investigated by using Rutherford backscattering spectroscopy, x-ray diffraction, and sheet resistance measurements. It was found that the dominant crystal phase of silicide formed during annealing at 600 and 625 °C for 90 sec was titanium monosilicide (TiSi), and that a homogeneous TiSi2 with resistivity of ∼15 μΩ cm was formed at 700 °C. Self-aligned TiSi2 with low resistivity can be obtained with two-step annealing: the first-step annealing was carried out below 600 °C and followed by removal of unreacted Ti on silicon dioxide (SiO2), and the second-step annealing was carried out above 650 °C.
Superconducting beryllium thin films prepared by ion-beam sputtering
Authors: Takei Koji , Nakamura Kiko , Maeda Yasushi
Published: July 2002

Beryllium (Be) thin films with superconducting transition temperature (Tc’s) up to about 6 K can be grown on room-temperature substrates using ion-beam sputtering. In contrast to the evaporation-deposited Be grown on a liquid-helium-cooled substrate, which is also a superconductor, the ion-beam-sputtered Be films show such high thermal stability that the Tc’s exhibit no change by room-temperature annealing for three months.
Frequency shift of the band gap of the surface polaritons on a grating
Authors: Seshadri S. R.
Published: July 2002

The reflectivity of the surface polaritons incident normally on a grating of finite length is investigated without assuming that the amplitude of the grating is small. The maximum reflectivity is found to be essentially the same as that obtained from a small-amplitude grating theory, but there is an upward shift in the center frequency of the band gap, with the shift increasing with the increase of the amplitude of the grating. A physical explanation for the shift of the band gap is provided.
Out-of-plane scattering from ion-exchanged optical waveguides
Authors: Imai M. , Ohtsuka Y. , Haneda N.
Published: July 2002

The light scattered out of multimode optical waveguides formed by ion exchange from molten salts of silver nitrate was measured in order to clarify the mechanism producing scattering loss. The angular distributions of the scattered light can be explained by the loss originating not only from surface roughness but also from silver ion concentration diffused in the glass. For a relatively thick waveguide of diffusion depth greater than 4.5 μm which was obtained by diffusion time longer than 7 h at 300 °C, it was found that the effect of bulk inhomogeneities is predominant in the air radiation. The correlation length in the direction of beam propogation was estimated to be the order of a wavelength of light.
Manganese as a p-type dopant for liquid-phase-epitaxial In0.53Ga0.47As
Authors: Whitney Peter S. , Fonstad Clifton G.
Published: July 2002

p-type In0.53Ga0.47As doped with manganese has been grown lattice matched to (100) InP substrates by liquid-phase epitaxy (LPE) at 604 and 550 °C. The electrical properties of the layers at room temperature and at 77 K are reported and compared to previously available data. Hole concentrations in the range from 4×1016 to 3×1018 cm−3 were obtained without difficulty. From these measurements, an activation energy for manganese acceptors of 52.3 ± 1.8 meV, and an effective distribution coefficient of unity are estimated. In addition, the effect of manganese doping on the phase equilibrium of the In-Ga-As system was investigated in the region of interest for LPE growth on InP, and the information necessary to grow p-type layers of In0.53Ga0.47As on InP with controlled supercooling and precise lattice matching is presented.
Origin of deep levels in the depletion region of p-ZnTe/n+-CdTe heterojunction determined by DLTS
Authors: Khan Mohammad Rezaul Huque , Saji Manabu
Published: July 2002

Deep level transient spectroscopy (DLTS) studies of the depletion region of p-ZnTe/n+-CdTe heterojunction have been done. Three deep hole trap levels were observed: one with activation energy of 0.14 eV (L1), another with 0.98 eV (L3), and the rest (L2) show a complex behavior possibly resulting from a continuous distribution of states occupying a certain width of energy level rather than a discrete one. The origin of these three levels have also been studied. From the bias-dependent DLTS, DLTS of heat treated samples, and DLTS of a p/n+ CdTe homojunction, it has been inferred that the trap level L1 is due to a thermal effect of the ZnTe film, L3 is due to a state in the ZnTe side of junction, and the complex L2 is due to the interface states resulting from dangling bonds caused by lattice mismatch.
Demagnetizing fields in magnetic measurements. I. Thin discs
Authors: Brug J. A. , Wolf W. P.
Published: July 2002

The long-range nature of magnetic dipole interactions leads to a shape dependence of all magnetic properties. In homogeneous ellipsoids, this dependence can be characterized in terms of a simple demagnetizing factor, which depends only on the shape of the body. In all other situations the demagnetizing fields depend on position within the body, and in most cases, also on the magnetic properties of the material. We present calculations on various thin disc-shaped samples, for four different model equations of state, from which demagnetizing corrections in a wide variety of situations can be estimated. The results show that the corrections are generally field and temperature dependent, in contrast to the usual approximation of a constant effective demagnetizing factor. These effects can be quite significant in the analysis of high-resolution magnetic measurements, especially near phase transitions.
Modulation-doped ZnSe:Mn dc thin-film electroluminescent devices
Authors: Kobayashi Masakazu , Mino Naoki , Inuzuka Hajime , Konagai Makoto , Takahashi Kiyoshi
Published: July 2002

Two types of ZnSe:Mn dc thin-film electroluminescent (EL) devices were prepared by molecular beam growth: a Au/ZnSe:Mn/GaAs cell with a single-crystal ZnSe:Mn host layer and an Al/ZnSe:Mn/ITO cell with a polycrystal ZnSe:Mn host layer. Modulation doping was used to investigate the active region in the ZnSe:Mn layer. It was found that threshold voltage characteristics of the Au/ZnSe:Mn/GaAs cell were influenced by the Mn doping position in the ZnSe host layer, but in the Al/ZnSe:Mn/ITO cell, there was no dependence of threshold voltage on the Mn doping position. The dependence of luminescence intensity-injection current characteristics on the Mn doping position showed that the excitation probability of Mn luminescence centers by injected electrons increased in the region close to the negative electrode for both types of EL cells.
Optical studies during pulsed CO2 laser irradiation of ion-implanted silicon
Authors: James R. B. , Narayan J. , Wood R. F. , Ottesen D. K. , Siegfriedt K. F.
Published: July 2002

The time-resolved optical reflectivity (at 633-nm wavelength) of ion-implanted silicon is measured during and immediately after CO2 laser irradiation [λ=10.6 μm, pulse duration (FWHM)=70 ns] as a function of the energy density of the laser. For a heavily doped sample and incident energy densities greater than 2.9 J/cm2, the reflectivity of the probe beam is found to rapidly jump to 70%, which is consistent with the reflectivity of liquid silicon. The high-reflectivity phase lasts for up to 1 μs, indicating a relatively deep molten layer as compared to similar annealing experiments with a visible or ultraviolet laser. The transmittance and reflectance (at 10.6-μm wavelength) of ion-implanted silicon are also reported as a function of the energy density of the CO2 laser. For energy densities slightly exceeding a threshold value, the transmittance (reflectance) of the tailing edge of the pulse is found to greatly decrease (increase). The interpretation of the optical measurements is based on a thermal model in which surface melting occurs for incident energy densities exceeding a threshold value.
Pressure and temperature dependence of the dielectric breakdown of polyethylene used in submarine power cables
Authors: Guerin P. , Hoang-the-Giam  , Ai Bui , Destruel P. , Deschamps L. , Perret J.
Published: July 2002

The dielectric strength of low-density polyethylene is measured under high hydrostatic pressure (25–800 bars) at temperature of 20, 45, and 70 °C. First results show that the breakdown field Eb decreases at 20 °C and increases with pressure in the range 45–70 °C for short-time tests. The significant variations of Eb are noted for 70 °C; for example, Eb=3.2 and 4.48 MV/cm for P=25 and 300 bars, respectively.
Annealing effects on electron drift mobility in hydrogenated amorphous silicon
Authors: Yoon Jong-Hwan , Lee Choochon
Published: July 2002

Annealing effects on electron drift mobility are investigated using time-of-flight photocurrent measurements in hydrogenated amorphous silicon. It is found that at room temperature the electron drift mobility and dispersion parameters decrease as annealing temperature is increased, but mobility activation energy remains unchanged by annealing treatments. These results can be explained by the broadening of exponential band tail due to the annealing process.
Theory of twisted nematic layers with weak boundary coupling
Authors: Becker M. E. , Nehring J. , Scheffer T. J.
Published: July 2002

Expressions for the threshold and saturation voltages are derived for twisted chiral nematic layers with weak boundary coupling and arbitrary elastic constant ratios. A general discussion is given of the stability of the various states which may occur in such layers.
Crystalline film quality in reduced pressure silicon epitaxy at low temperature
Authors: Nagao S. , Higashitani K. , Akasaka Y. , Nakata H.
Published: July 2002

The influence of deposition pressure on epitaxial crystalline film quality has been investigated with respect to vapor-phase silicon epitaxial growth (SiH2Cl2-H2 system). It is shown that the crystalline film quality has been improved by reducing the deposition pressure. In addition, a prebaking process at reduced pressure has been found to be effective for obtaining single-crystalline silicon films with atmospheric pressure deposition as well as reduced pressure deposition. The deposition temperature can be lowered down to 930 °C with perfect crystalline film by reducing the deposition pressure. The crystalline quality of epitaxial films grown at a low temperature of 930 °C using the reduced pressure technique has been verified to be excellent by fabricating bipolar transistors with an oxide isolation technique.
Comparison of magnetic field and electric potential produced by frog heart muscle
Authors: Burstein Deborah , Cohen David
Published: July 2002

A comparison is made here between the magnetic field and electric potential produced by a thin strip of frog heart muscle. An experimental test is made of the theory which states that the wave front of a single fiber (or parallel bundle of fibers as in this strip) can be represented, for both the magnetic field and electric potential, by the same single-current dipole. First, an experimental measurement is made of the ratio of magnetic field/electric potential produced by an actual current dipole in an electrolytic tank. Then the dipole is replaced by the muscle strip and a measurement is again made of the ratio; this is done for three muscle strips at eight different source-to-detector distances ranging from 1 to 5 cm. It is found, in all cases, that the muscle ratios are equal to those of the actual dipole to within the experimental uncertainty of ±10%. Therefore, to this extent the theory is verified for this case of a thin strip of frog heart tissue.
Two-line operation of a CO2 transversely excited atmospheric-pressure laser by means of a bifurcating cavity
Authors: Ruschin S. , Zelingher R. , Gover A.
Published: July 2002

By means of an intracavity grating that splits the paths of two different transition lines, a CO2 transversely excited atmospheric-pressure laser was operated at two wavelengths. The scheme provides control of the wavelengths and pulse delays. The two lines belonged to different vibrational bands.
High-pressure studies of interface states induced in CdS by Ag and Cu
Authors: Zurawsky W. P. , Stolt Kaj , Drickamer H. G.
Published: July 2002

Ag and Cu interfaces with chemically prepared CdS surfaces have been studied under hydrostatic pressures to 10 kbar. These interfaces exhibit a photovoltaic spectrum at photon energies less than Eg due to the existence of new states bound at the interface. We find that the pressure coefficient of the interface-state subband is sensitive to the preparation of the interface even through the atmospheric pressure photovoltaic spectra of the various interfaces studies are very similar.
A stretched betatron
Authors: Blaugrund A. E. , Fisher A. , Prohaska R. , Rostoker N.
Published: July 2002

We have demonstrated trapping, confinement, acceleration, and dumping of electrons in a betatron which has a geometry similar to the Astron. 76±22 nC were accelerated to 800±100 keV. This corresponds to a circulating electron current of 60 A. The betatron has a 6-cm orbit radius and is 1 m long. Electrons are injected tangentially from a 70-kV, 15-A field emission diode. A toroidal field roughly equal to the betatron field is used.
Plasma properties and thin-film formation in a pulsed electromagnetic inductive silane discharge
Authors: Ebihara Kenji , Maeda Sadao
Published: July 2002

A new approach to prepare thin films in a pulsed inductive silane discharge is attemped. The time-resolved spectral lines qualitatively clarified dynamics of decomposition process in the pulsed silane discharge and the local thermodynamic equilibrium in this discharge was investigated by the population density distribution estimated from excitation temperature measurement. The films had peculiar deposition patterns with good adhesion due to electromagnetic effects and main group of infrared spectra was the SiH3 complex.
Arc expansion in xenon flashlamps
Authors: Kushner M. J.
Published: July 2002

Plasma arcs in large diameter (d>1 cm) xenon flashlamps often do not completely fill the bore of the discharge tube. The arc is usually initiated on one side of the discharge tube, adjacent to the ground plane, and the fraction of the discharge tube filled with plasma varies as a function of axial location. A model is presented that describes, from first principles, arc expansion in xenon flashlamps. The model simultaneously solves a coupled set of one-dimensional transport equations in different regions of the discharge tube to simulate two-dimensional effects in hydrodynamics, electron kinetics, and radiation transport. Using this method, expansion of arcs initiated at arbitrary locations within the discharge tube can be studied. Arc filling fractions are found to decrease with increasing filling pressure of xenon, increasing diameter of the discharge tube, and decreasing stored energy in the discharge circuit. The arc filling fraction also decreases as the breakdown filament moves away from the axis of the discharge tube and towards the wall. Arc expansion is slowed and ultimately halted by a lowered E/N (electric field/gas density) in the gas exterior to the arc, rapid conversion of atomic ions to molecular ions and their subsequent recombination, and by the efficient manner in which radiation dissipates energy which might otherwise be available for thermodynamic expansion of the arc. The asymmetric expansion of the plasma arc results in asymmetric heating of the inside wall of the discharge tube, also calculated in the model. The growth of the plasma arc is also found to be in part responsible for changes in the spectrum of radiation emitted from the arc for various angles of observation. This effect results from wavelength-dependent absorption coefficients in the plasma.
A new design concept for field distortion trigger spark gaps
Authors: Schaefer G. , Pashaie B. , Williams P. F. , Schoenbach K. H. , Krompholz H.
Published: July 2002

A common field distortion triggered spark gap utilizing geometric field enhancement at sharp edges usually operates in a cascade mode via the trigger electrode. A new trigger concept is proposed allowing strong field enhancement and direct breakdown between the two main electrodes. A test setup was designed to prove the feasibility of this concept. Experimental results on delay and jitter depending on percent breakdown voltage are presented. Best results achieved are a delay of 9 ns and a jitter of 2 ns at a self-breakdown voltage of 15 kV.
Experimental study of the current penetration in a dense Z pinch
Authors: Skowronek M. , Romeas P.
Published: July 2002

We study the oscillations superimposed on an intense discharge feeding a dense Z pinch. The periods, measured in different conditions, allow the measurement of the plasma inductance. We show that the variation of this inductance is related to the current penetration in the plasma, the anomalous current distribution, and the superconductive behavior of a dense turbulent plasma.
High-precision refractive index measurements revealing order parameter fluctuations in KMnF3 and NiO
Authors: Schäfer F. J. , Kleemann W.
Published: July 2002

The temperature dependence of the refractive index n of cubic crystals undergoing phase transitions (PT) is measured with an accuracy of the order δn=10−6 at temperatures between 3.5 and 1000 K with a computer-controlled Jamin–Lebedeff interferometer. Microscopic monitoring for in situ sample orientation and single domain work is provided. Results are presented for KMnF3 (antiferrodistortive PT) and NiO (antiferromagnetic PT) and discussed within the framework of a generalized phenomenological indicatrix perturbation theory. It predicts the proportionality between the order parameter autocorrelation function 〈δη2〉 and the refractive index anomaly preceding the PT. Comparison with recent theoretical predictions is performed.
Microwave absorption of conductive powders and its application to the study of bulk transport properties
Authors: Watanabe Y.
Published: July 2002

The microwave eddy current loss in a powder sample has been examined both theoretically and experimentally. It is shown that under certain conditions, the absorption power of the conductive powder inserted in the region of the maximum microwave magnetic field in the cavity is proportional to the bulk conductivity, and therefore the temperature dependence of the bulk conductivity can be easily deduced from experiments on powders. The method is applicable to resistivities ranging from 10−1 to 10−6 Ω m. Examples of measurements at 9.4 GHz are given for Si, Fe3O4, and VSe2.
Mössbauer isomer shift studies of the β-Ti(Fe) solid solution
Authors: Galvão da Silva E. , Preston R. S. , Gonser U.
Published: July 2002

The present study reports the experimental results and a theoretical model, based on short-range order and electronic charge transfer from Ti to Fe, to explain the dependence of the isomer shift on the iron content in  β-Ti(Fe) solid solution. The theoretical expression reported here for the isomer shift depends on three different fitting parameters which take into account the electronic-charge transfer, and has been fitted with the experimental data for samples containing 3–18 at. % Fe.
Random-field critical scattering
Authors: Jaccarino V. , King A. R. , Belanger D. P.
Published: July 2002

The quasielastic scattering of neutrons in d=3 (Fe0.6Zn0.4F2) and d=2 (Rb2Co0.85Mg0.15F4) random-field Ising model (RFIM) systems in the critical region has been studied. A sharp phase transition at Tc(H) with new critical behavior is observed at d=3 whereas the phase transition is destroyed at d=2 in the presence of a random field. At d=3 the antiferromagnetic state is stable for all T and H below Tc(H) whereas the field-cooled domain state shows irreversible behavior. Hence the lower critical dimensionality dl of the RFIM 2≤dl<3 in agreement with earlier birefringence experiments. The marked differences between the properties of the d=2 and d=3 RFIM system are elucidated. Our work strongly suggests that all previous neutron studies of similar systems have been incorrectly interpreted as regards dl.
Detection of defect-free zones in annealed Czochralski silicon with synchrotron section topography
Authors: Tuomi T. , Tilli M. , Anttila O.
Published: July 2002

High-resolution, rapid synchrotron x-ray topography is used to study oxygen-induced microdefects and their spatial distribution in a large number of (100) n-type silicon wafers, which had undergone different two-stage thermal anneals. Section topographs reveal a 40–60-μm-thick defect-free zone on the surface of a wafer annealed first at 800 °C for 20 h and then at 1150 °C for 4 h.
Temperature dependence of the effective permeability of the resin-molded Sendust alloys
Authors: Tanaka T. , Mino M. , Okada M. , Homma M.
Published: July 2002

The effective permeability ( μeff) of the ring Sendust alloys (Fe-9–10 wt. % Si-5–7 wt. %Al), molded with Epoxy resin, was measured in the temperature range of −10 to 70 °C. The μeff of the alloys in molded condition measured at 20 °C is smaller than that in unmolded condition. The high values of the μeff at 20 °C of the molded alloys were obtained from the alloys in which magnetostriction constants (λs) were close to zero. The temperature dependencies of the μeff for the studied alloys in the unmolded condition are very similar, but after molding they are classified into four variations depending on the value of λs. When the alloys have large positive or negative values of λs, the μeff increases or decreases monotonically with increasing temperatures, but for the alloy with λs ≂0, the μeff temperature dependence is complex. These behaviors of the μeff with temperature are interpreted on the basis of the induced stress, initiating from the differences in thermal expansion between alloys and Epoxy resin. The μeff of the molded alloys was mainly dominated by the induced uniaxial magnetic anisotropy (Ku) by the tangential and axial compressive stresses in the molded ring alloys.
Temperature dependence of electromagnetically excited sound in single crystals of Fe
Authors: Dewar G. , Alexandrakis G. C.
Published: July 2002

The temperature dependence of the transmission of 9.4-GHz longitudinal sound through an (110)-oriented iron single crystal has been measured over the temperature range 4.2–310 K. The ∼19-μm-thick crystal formed part of the common wall between two microwave cavities. A static magnetic field was maintained along the [111] direction in the plane of the sample and parallel to the incident rf magnetic field. The sound was generated through the Lorentz force on the rf currents associated with the incident microwaves. The transmission signal was ∼10−13 W for incident microwave power of 200 mW. Calibration of the temperature dependence of the sensitivity of the microwave system revealed that the amplitude of the transmission signal increased by a factor of ∼4 between 4.2 and 300 K. In this particular crystal orientation the longitudinal sound wave is coupled to the rf magnetization via the magnetoelastic coupling. The modest residual resistivity ratio (15) of our sample ruled out geometric resonance absorptions. None were observed.
Effect of Au additions on the rotational hysteresis of Cu0.85Mn0.15
Authors: Gyorgy E. M. , Walker L. R.
Published: July 2002

We have investigated the rotational hysteresis of zero-field cooled samples in the compositional series Cu0.85−xMn0.15Aux. The rotational hysteresis can be expressed as aH2m+bH4m where Hm is the measuring field. For 0<x<0.01 the constant a is, within 10%, independent of x while b increases by a factor of 2.5 as x increases from zero to 0.01. To characterize the material further, the behavior of the remanent magnetization (Mr), the unidirectional anisotropy constant (K1), the dc and ac susceptibility (χ) were studied. As has been previously reported, K1 increases linearly with x. For x<0.01, χdc=(1.5±0.1)×10−3 and is independent of x. For x=0.02, χdc increases to 2.0×10−3. The cusp in the small-signal ac susceptibility increases linearly at the rate of 5.5° per 1% Au. The value of Mr increases with Au content, the fractional change increasing as the applied field decreases. A simple model is presented that rationalizes some of these findings.