bluuebunny/crossref_metadata_2025 huggingface dataset:
Plastic Bragg Cell in far-infrared region
Authors: Saito T. , Hamada Y. , Yamashita T. , Ikeda M. , Tanaka S.
Published: February 2003

Photoacoustic diffraction is first observed in far-infrared (FIR) range. A cell made of TPX (4-methyl-pentene-1) is employed as a Bragg Cell in both visible and FIR regions. It is experimentally demonstrated that the TPX Bragg Cell is a very convenient tool as a plasma simulator in the FIR laser scattering apparatus.
Microstructure and properties of rf-sputtered amorphous hydrogenated silicon films
Authors: Ross R. C. , Messier R.
Published: February 2003

The effect of both total gas pressure (Ar+H2) and partial pressure of H2 during the rf-sputtering of amorphous hydrogenated silicon films was investigated. It is shown that decreasing the total gas pressure (PT) leads to a number of consistent and desirable film characteristics including no post-deposition oxidation, essentially zero etch rate, no resolvable microstructure, predominant monohydride bonding, and low optical band gap. These lowest PT films contain ∼17 at. % H and 4 at. % Ar, have reasonable deposition rates (60–70 Å/min) and are in a high state of compressive stress. The relations between the deposition variables and the more fundamental surface reaction processes are discussed. Specifically, we demonstrate that Ar ion bombardment effects, due to high negative substrate self-biases, are dominant at low PT.
On the carrier collection efficiency of amorphous silicon hydride Schottky barrier solar cells: Effects of recombination
Authors: Gutkowicz-Krusin Dina
Published: February 2003

Exact solutions for the photogenerated carrier densities and the carrier collection efficiency have been found for amorphous silicon hydride (a-SiHx ) Schottky barrier solar cells. The dependence of the collection efficiency η on the nature of the contacts, and on the four characteristic lengthscales (thickness of a-SiHx film, hole diffusion length, absorption length, and width of the depletion region) is determined. Strong dependence of η on the width of the depletion region at very short wavelengths and on the hole diffusion length at long wavelengths suggests that the theory presented here can be used for the determination of these parameters from the experimental measurements of η in solar cells with intimate metal/semiconductor contacts.
High-temperature degradation of InGaAsP/InP light emitting diodes
Authors: Temkin H. , Zipfel C. L. , Keramidas V. G.
Published: February 2003

The results of accelerated aging study of high radiance double heterostructure InGaAsP/InP light emitting diodes (LED’s) are reported. Under a forward bias of 5 kA/cm2 and a junction temperature of 140° C, these devices show a gradual degradation of ∼5% after 5000 h of aging. However, at temperatures above ≊190° C, a new mechanism is observed, resulting in rapid degradation, down to ∼20% of the initial power output in 300 h at 200 °C, even without bias. Electron beam induced current and transmission cathodoluminescence analysis show formation of 〈110〉 dark line defects in the InP buffer layer originating at microscopic inclusionlike defects. While it is not clear that this mechanism is relevant for normal LED operation, its presence greatly complicates interpretation of the accelerated aging experiments.
Efficient injection locking of an e-beam-excited XeF laser
Authors: West John B. , Komine Hiroshi , Stappaerts Eddy A.
Published: February 2003

Narrowband ultraviolet radiation from a frequency-doubled dye laser has been used to control the linewidth and polarization of a long pulse length, electron-beam-excited XeF laser. Linewidths of 0.004 nm have been achieved in the 353-nm band of the XeF B→X laser transition. Over 90% of the energy in the free-running laser pulse has been extracted in the narrowband injection-locked pulse. Ratios of injection signal power to output laser power on the order of 1:5000 are adequate for efficient injection-locking to occur.
Gold gettering in silicon by phosphorous diffusion and argon implantation: Mechanisms and limitations
Authors: Lecrosnier D. , Paugam J. , Pelous G. , Richou F. , Salvi M.
Published: February 2003

The ability of phosphorus diffusion or argon implantation to remove gold from a silicon wafer has been studied. Both the gettering layer and the gettered substrate have been analyzed for their gold content by complementary techniques such as Rutherford backscattering, neutron activation analysis, and deep level transient spectroscopy. Phosphorus diffusion allows a very efficient gold removal when surface concentration CS and temperature T are kept in a well-defined domain (high CS , low T). On the contrary, the gettering is ineffective in the low CS , high T domain. The boundary between these two domains is found to be an iso-Fermi level curve corresponding to Ec −EF = 0.15 eV. These results are explained by the formation of a negatively charged (P, Au) pair. Argon implantation induces a damaged layer which is found to accomodate large amounts of metal. However, at annealing temperatures higher than 800 °C, gold is found to remain in the bulk at noticeable concentrations which increase with temperature. Such a behavior is attributed to a weak binding energy between gold atoms and the implantation-induced defects. Finally, as low temperatures are found to prevail in both cases, it is emphasized that the duration of the gettering step must be long enough so that gold can travel across the wafer. For example, in the case of argon implantation, a quite efficient gold removal is obtained at 800 °C only after 10 h.
Silicide surface phases on gold
Authors: Green A. K. , Bauer E.
Published: February 2003

The crystalline silicide layers formed on (111) and (100) surfaces of Au films on various Si single-crystal substrates are studied by LEED and AES in conjunction with sputter-depth profiling as a function of annealing temperature. On the (111) surface, three basic silicide structures are obtained corresponding to layers of various thicknesses as obtained by different preparation conditions. The (100) surface shows only two different structures. None of the structures is compatible with the various bulk silicide structures deduced from x-ray diffraction. Using LEED as a criterion for the presence or absence of silicide on the surface, smaller layer thicknesses are obtained than reported previously on the basis of AES studies.
Laser annealing to produce ferroelectric-phase PbTiO3 thin films
Authors: Matsui Yasushi , Okuyama Masanori , Fujita Nobuhiko , Hamakawa Yoshihiro
Published: February 2003

PbTiO3 thin films with good ferroelectric properties have been prepared by rf sputtering at relatively low temperatures of ∼350 °C and subsequent laser annealing. The annealing has been done by cw CO2 laser irradiation at 10∼40 W for 0.1∼10 sec. A distinct phase change from the paraelectric Pyrochlore phase to the ferroelectric perovskite phase is induced by means of a solid-state reaction in the irradiated region without temperature rise of peripheral regions. The observed effect increases feasibility of producing new functional electronic devices employing ferroelectric thin films such as nonvolatile memory field-effect transistors, infrared optical field-effect transistors, and imaging devices with a ferroelectric layer.
Evaluation of hyperfine field distributions from Mössbauer spectra using Window’s Fourier method
Authors: Keller H.
Published: February 2003

The Fourier expansion method developed by Window for the evaluation of hyperfine field distributions has been tested on simulated Mössbauer spectra. In the case of a distribution with a low-field tail this method may lead to erroneous results if the intrinsic Mössbauer parameters characterizing the component spectra are not chosen properly.
An efficient singlet oxygen generator for chemically pumped iodine lasers
Authors: Richardson R. J. , Wiswall C. E. , Carr P. A. G. , Hovis F. E. , Lilenfeld H. V.
Published: February 2003

The results of a study on improved methods for generating O2(1Δ) are presented. A wetted-column reactor utilizing C12 and a mixed H2O2-NaOH solution as reactants was found to produce 70–80 mmole/s of O2, [50% as O2(1Δ)], with a C12 input of 90–100 mmole/s.
Temperature dependence of the reflectance of solid and liquid silicon
Authors: Lampert M. O. , Koebel J. M. , Siffert P.
Published: February 2003

The reflectivity of silicon plays an important role in laser annealing. Results from literature are limited either to 225 °C in the solid phase or to 1410 °C in the liquid phase. Measurements, at 633 nm wavelength in a large temperature range near melting point, are reported here.
Transverse electric fields guided by doubly periodic structures
Authors: Chen Chin-Lin
Published: February 2003

An exact and analytic description for the transverse electric waves propagating in dielectric structures periodic in two directions is presented. It is shown, through simple physical consideration, that when relations involving the geometry and electromagnetic properties of doubly periodic structures (DPS) are satisfied, fields in DPS can be expressed in terms of four plane waves. The dispersion relations for this type of structures are then derived. Also obtained are the expressions for field distributions for various Bloch modes. The properties of the DPS and its possible applications as focusing components (or lenses), are also discussed.
On the surface recombination current of metal-insulator semiconductor inversion layer solar cells
Authors: Nielsen Otto M.
Published: February 2003

Current voltage characteristics have been obtained under dark and illuminated conditions for Al-SiO2-pSi metal-insulator semiconductor inversion layer solar cells. The cells were fabricated on <100≳ and <111≳ oriented substrates with resistivities in the range of 8–15 Ω cm. For <111≳ cells the open circuit voltages Voc were found to be lower than for <100≳ cells. The measured differences in Voc were higher than expected from the dark characteristics which is explained as a difference in the surface recombination current due to a higher interface state density Nss of <111≳ cells.
Mechanisms of bubble-wall radial motion deduced from chirality switching and collapse experiments using fast-rise bias field pulse.
Authors: Honda Shigeo , Fukuda Nobuo , Kusuda Tetsuzo
Published: February 2003

The statistical probabilities of chirality switching and collapse of unichiral bubbles subjected to fast rise time (∼2 ns) bias field pulses with variable duration τ or amplitude hp are investigated. The results are interpreted in terms of transient oscillations in wall position related to existing models for a rapidly moving domain wall. The ’’2π-mode’’ oscillation was confirmed in the wall displacement or the apparent wall velocity during collapse of both χ+ and χ− bubbles stabilized near the static collapse field Hco. A corresponding behavior was observed in the collapse probability versus τ or hp for fixed bias field near Hco. For instance, periodic valleys appearing in the collapse probability curve versus τ have separations consistent with the 2π-mode period. Also, several uncollapsed χ bubbles with states opposite to their initial states are left mainly for pulse conditions corresponding to the valleys. These phenomena are discussed based on the coherent precession model. It was also found that the mode of wall motion changes from the coherent precession mode to the horizontal Bloch line (HBL) mode with decreasing static bias field. The apparent saturation velocity due to the HBL mode was also detected by setting the static bias field far from Hco.
On the transient space-charge-limited current problem—a solution in Lagrangian mass variables
Authors: Johnson Stevens F. , Lonngren Karl E.
Published: February 2003

Using a one-dimensional unipolar ion conduction model of the type originally studied by Many and Rakavy, the transient behavior of the electric field and space-charge distribution is studied in planar, cylindrical, and spherical geometries. A general solution in Lagrangian mass variables is obtained. We are able to recover the recent results of Hensen in planar geometry.
A phase analysis in pseudobinary Pb(Fe1/2Nb1/2)O3−Pb(Mg1/2W1/2)O3 solid solution
Authors: Lee Moon Ho , Choo Woong Kil
Published: February 2003

A phase analysis in pseudobinary (1−x)Pb(F1/2Nb1/2)O3−xPb(Mg1/2W1/2)O3 system is conducted by measuring its dielectric properties, E-P hysteresis, and dc resistivity at x = 0.1 interval. Lattice parameters and ordering of ions are analyzed by the x-ray diffraction method, and the temperature-composition phase diagram is determined. The system is found to form a solid solution of perovskite structure throughout the entire composition range, but the nature of its phase transitions changes from ferroelectric-paraelectric for the composition range of 0.0⩽x⩽0.5 to antiferroelectric-paraelectric for the composition range of 0.6⩽x⩽1.0. The ferroelectric-paraelectric transition is relativity sharp for 0.0⩽x⩽0.1 and becomes diffuse for 0.2⩽x⩽0.5, and the antiferroelectric-paraelectric is diffuse for 0.6⩽x⩽0.8 and becomes sharp for 0.9⩽x⩽1.0.
Neutron transmutation as a method to calibrate the infrared absorption of indium in silicon
Authors: Pajot B. , Débarre D. , Roche D.
Published: February 2003

The integrated intensity of selected absorption lines of indium in silicon can be used to obtain an infrared calibration factor for this impurity. Infrared calibration factors obtained with different electrical methods for measuring the In concentration are given. We have used the comparison of the In absorption in samples before and after partial compensation of In by neutron transmutation to correlate the difference between the integrated intensities of the In lines and the In concentration compensated by P, independently of the electrical measurements. The coefficient obtained gives slightly higher In concentrations than those using the resistivity and capacitance-voltage measurements as ’’primary standards.’’
Iron in heat-treated gallium arsenide
Authors: Yu Phil Won
Published: February 2003

The GaAs substrate materials heat treated under several different conditions have been studied by the photoluminescence method. Observations of the 0.37-eV emission due to Fe2+ intra-center transition show the accumulation of Fe at the near-surface region. Secondary-ion mass spectrometry indicates that the accumulation of Fe (≳1017 cm−3) is primarily due to the out-diffusion of unintentionally doped Fe present in the substrate materials. The accumulation of Fe explains the presence of Fe in epitaxial layers and the moderate p-type thermal conversion in heat-treated substrates. Heat-treatment effects on the 1.36-, 1.40-, 0.81-, 0.63-, and 0.57-eV bands, respectively, due to Cu, Mn, Cr, O, and Cr are also described.
Thermalization of sputtered atoms
Authors: Meyer Kevin , Schuller Ivan K. , Falco Charles M.
Published: February 2003

We have calculated the energy distributions of sputtered Nb and Cu atoms ejected from amorphous targets under low-energy Ar bombardment. A formula based on elementary kinetic gas theory is used to calculate the subsequent energy loss of the ejected atoms due to collisions in the sputtering gas. The energy distributions of the sputtered atoms arriving at the substrate is compared with the distributions obtained using thermal evaporation techniques. This comparison indicates that the preparation of epitaxial metallic films, such as Layered Ultrathin Coherent Structures using sputtering techniques may have fundamental advantages over thermal evaporation.
Formation of Al-nitride films at room temperature by nitrogen ion implantation into aluminum
Authors: Lieske N. , Hezel R.
Published: February 2003

A new method is demonstrated for the preparation of thin aluminum nitride layers using the direct nitridation aluminum by low-energy nitrogen ion implantation in the ion energy range 0.5-5 keV. The Al-nitride films were obtained at room temperature without any thermal annealing. For the first time Al-nitride was studied with Auger electron spectroscopy (AES) and low-energy electron-loss spectroscopy (ELS) and the corresponding spectra, together with those of Al and Al2O3, are presented. An electron energy-level scheme for Al-nitride was derived from the AlLvv Auger spectra, from the valence electron excitation spectra, and from the Al(2p) and N(ls) core electron excitation spectra measured by ELS.
Long-pulse, broadband-Xe*2 -fluorescence excitation of OCSe: Initiation of the Se(1S→3P) laser and implications for large-system design
Authors: Trott W. M. , Woodworth J. R. , Rice J. K. , Miller C. K.
Published: February 2003

The formation and loss of Se(1S) excited states have been examined using long-pulse (0.7–1.0 μsec), broadband (13 nm FWHM)-Xe*2- fluorescence photodissociation of carbonyl selenide. Experimental data are compared to results of a computer code that models the Xe*2 radiation transport and Se(1S) kinetics. The effective quantum yield for Se(1S) production over the wavelength interval 160–180 nm has been found to be near 0.6. The observed Se(1S) decay rates have been used in conjunction with the code to predict the effects of excitation pulse length on the efficiency of the selenium laser system. Laser oscillation has been demonstrated for the Se(1S0→3P1) transition in a long-active-length (54 cm) optical cavity. Oscillator performance was characterized as a function of OCSe pressure. The optimized laser output was 1.3 mJ, a value consistent with the Se(1S) kinetics and laser cavity conditions.
11% efficient single-crystal solar cells and 10% efficient polycrystalline cells made from refined metallurgical silicon
Authors: Hanoka J. I. , Strock H. B. , Kotval P. S.
Published: February 2003

Refined metallurgical silicon has been utilized as a feedstock material both for Czochralski-pulled single crystal and for cast polycrystalline silicon solar cells. Using a phosphorous diffused junction for an n on p structure, the single-crystal cells have yielded AM1 efficiencies up to 11.1%, open circuit voltages up to 596 mV, and fill factors as high as 81% (not all on the same cell). The cast polycrystalline substrates have produced cells up to 10.1% efficient (AM1) with fill factors of 79% and Voc = 585 mV. Properties of the single-crystal and polycrystalline cells are quite similar, with the principal limiting factor being Jsc, which is typically 20–23 mA/cm2. Spectral response and EBIC data indicate that a considerable amount of the recombination is due to impurities. For the cast polycrystalline cells, the electron beam induced current data shows that grain boundary recombination is significant.
An n-In0.53Ga0.47As/n-InP rectifier
Authors: Forrest S. R. , Kim O. K.
Published: February 2003

We report the current-voltage (I-V), capacitance-voltage (C-V), and photoresponse characteristics of n-In0.53Ga0.47 As/n-InP heterobarrier diodes. We find the conduction-band barrier is Δεc = 0.22±0.02 eV. We find thermionic emission is the dominant mechanism for carrier transport across the heterobarrier. Also, to the level of sensitivity of our measurement techniques, no interface states have been detected.
InGaAsP/InP buried-heterostructure lasers (λ = 1.5 μm) with chemically etched mirrors
Authors: Adachi S. , Kawaguchi H. , Takahei K. , Noguchi Y.
Published: February 2003

Buried-heterostructure InGaAsP/InP lasers with chemically etched mirrors are fabricated successfully. The lasers emit light at ∼1.5 μm. The threshold current of these lasers is nearly the same as that of conventionally fabricated cleaved-mirror lasers. This fabrication procedure enables us to obtain low-threshold-current devices and allows a much wide variety of device design and fabrication compared with the conventional cleaving technique.
Comparison of two equation-of-state models for partially ionized aluminum: Zel’dovich and Raizer’s model versus the activity expansion code
Authors: Harrach Robert J. , Rogers Forest J.
Published: February 2003

Two equation-of-state (EOS) models for multipy ionized matter are evaluated for the case of an aluminum plasma in the temperature range from about one eV to several hundred eV, spanning conditions of weak to strong ionization. Specifically, the simple analytical mode of Zel’dovich and Raizer and the more comprehensive model comprised by Rogers’ plasma physics avtivity expansion code (ACTEX) are used to calculate the specific internal energy ε and average degree of ionization Z̄*, as functons of temperature T and density ρ. In the absence of experimental data, these results are compared against each other, covering almost five orders-of-magnitude variation in ε and the full range of Z̄* We find generally good agreement between the two sets of results, especially for low densities and for temperatures near the upper end of the rage. Calculated values of ε(T) agree to within ±30% over nearly the full range in T for densities below about 1 g/cm3. Similarly, the two models predict values of Z̄*(T) which track each other fairly well; above 20 eV the discrepancy is less than ±20% fpr ρ≲1 g/cm3. Where the calculations disagree, we expect the ACTEX code to be more accurate than Zel’dovich and Raizer’s model, by virtue of its more detailed physics content.
A method of determining minority carrier lifetime and doping level profiles of low-doped metal-oxide-semiconductor structures using pulsed photoinjection
Authors: Efron U. , Grinberg J.
Published: February 2003

This method. aimed at determining doping level and minority carrier lifetime of low-doped semiconductors (<1014/cm3 in silicon) is based on pulsing the metal-oxide-semiconductor device into deep depletion. A delayed photopulse is then applied to the sample, which causes partial collapse of the depletion region. The changes in fill time and in capacitance versus collected photocharge are measured. The minority carrier lifetime is computed through the dependence of fill time on the magnitude of the photoinjected charge. The doping level is determined by the change in capacitance following the photoinjection. The method is advantageous in (a) independently supplying the doping level and lifetime, (b) being insensitive to edge injection, and (c) enabling the determination of the diffusion length.
Effect of background doping on the electron mobility of (Al,Ga)As/GaAs heterostructures
Authors: Drummond T. J. , Kopp W. , Morkoç H. , Hess K. , Cho A. Y. , Streetman B. G.
Published: February 2003

Selectively doped single period (Al,Ga)As/GaAs heterostructures have been grown by molecular beam epitaxy and characterized by Van der Pauw-Hall measurements. The mobility of the two-dimensional electron gas localized at the heterojunction interface has been examined as a function of background charge concentration in the GaAs layer. The electron mobility has been found to decrease monotonically with increasing background concentration, as predicted by calculations based on a two-dimensional screening factor and remote donor-electron interaction.
Reduction of electron trapping in silicon dioxide by high-temperature nitrogen anneal
Authors: Lai S. K. , Young D. R. , Calise J. A. , Feigl F. J.
Published: February 2003

Electron trapping in silicon dioxide is reduced by nitrogen annealing in a furnace system with very low moisture content and special cooling techniques. The flatband voltage shift resulting from injected hot electrons is significantly reduced by the annealing together with the interface states generated. The trapped charge is laterally nonuniform when the oxide is not annealed. From photo I-V measurement, the density of electrons trapped in the bulk of the oxide is reduced by this treatment. The distribution of the trapped charge changes from a uniform distribution in the bulk for a 1-h anneal to a distorted U shape distribution, with a larger build-up on the aluminum-silicon dioxide side for a 17-h anneal. The density of trapped charge close to the silicon-silicon dioxide interface is reduced and thus the smaller flatband voltage shift. With the reduction in bulk change, interface state charge beomes important.
Generation of strong time compressed light ion beams
Authors: Quon Bill H. , DiVergilio William F. , Gekelman Walter , Guiragossian Zaven G. T. , Stenzel Reiner L.
Published: February 2003

Positive light ions (He4) are extracted from a pulsed plasma source and accelerated in two states, first at constant potential and subsequently by a time varying voltage which is programmed to generate a time compressed beam bunch, downstream at a defined distance form the accelerator. Time compression of a 1-μs extracted beam pulse into an 8-ns bunched pulse at a distance of 66 cm from the source has been achieved. The technique provides useful applications for concentrated energy deposition on targets and is part of a proposed Light Ion Fusion Experiment (LIFE) accelerator system where 20:1 axial pulse compression would be programmed to occur during the ballistically focused and neutralized transport of intense ion beams.
High resistance mode in a modified Penning discharge
Authors: Sen Chitra
Published: February 2003

The high-resistance mode of a modified Penning discharge has been studied under different operating conditions both experimentally and theoretically. The experiment reveals the conditions for the existence of different modes and their properties. A theory of non-neutral plasma gives the insight of the physics of mode transitions and the properties of different modes.
The analysis of strained surface layers on single crystals utilizing divergent-beam x-ray patterns
Authors: Schutz R. J. , Testardi L. R. , Weissmann S.
Published: February 2003

We describe techniques for determining the strain matrix and rotation matrix of a homogeneously strained surface layer on a single-crystal flat surface. The surface layer must retain the basic structure of the underlying undistorted crystal but may be anisotropically strained or rotated with respect to it. The technique utilizes back-reflection divergent-beam patterns (pseudo-Kossel patterns) and relies on the fact that diffraction patterns from both the strained surface layer and the underlying crystal are observed. This is accomplished through the proper combination of layer thickness and x-ray penetration depth. The analysis is not dependent on the cause of the strain, thereby making it applicable to many experimental conditions, such as high-energy ion damage, surface diffusion, and epitaxial growth. The error in the three principal strains determined by this technique is about 12% of the largest principal strain. The lower limit of strain detectable is estimated to be 0.05%.
1H nuclear magnetic resonance studies of domain structures in polymers
Authors: Cheung T. T. P. , Gerstein B. C.
Published: February 2003

The structures of amorphous (noncrystalline) domains in polyethylene, conditioned (at 150 °C for 15 min) and unconditioned polypropylene films and a vitrain portion of Kentucky No. 6 coal have been investigated using the Goldman-Shen NMR pulse sequence which monitors the transfer of 1H magnetization from the amorphous to the crystalline domains. The diffusion equation is solved with respect to such transfer. The size and shape of the amorphous domain is inferred by fitting the theoretical results to the experimental data. It seems that the layer-like configuration is a poor description for the polyethylene and polypropylene films unless the spatial orientation of the amorphous domain is isotropic. However the spherical configuration is inadequate for Kentucky No. 6 vitrain. The average width b̄ of the amorphous domain is 90–150 Å for polyethylene, 20–30 Å for uncontinued polypropylene film, and 30–50 Å for the conditioned films. The diffusion of magnetization in the amorphous domain of Kentucky No. 6 is faster than that of the polymers, though the dipolar interaction is much weaker in the former. A transfer process due to tranlational motion of small mobile chemical species is suggested.
Determination of the H distribution in reactively sputtered amorphous silicon-hydrogen alloys by proton nuclear magnetic resonance
Authors: Jeffrey F. R. , Lowry M. E.
Published: February 2003

Data are presented for a series of samples of varying H content which show a-Si:H to contain both a random, dilute distribution of H and a form of clustering. The dilute phase is shown to have a local H density of approximately 3.5×1021 cm−3 regardless of the overall H content of the film. This phase appears to exist in up to 88% of the film’s volume. The clustered form appears to also have a configuration which is independent of sample-wide average H density. Several possible models for the clusters which could explain the data are explored.
Pole figure measurements of drawn and rolled PVF2 films
Authors: Brasen D. , Wang T. T.
Published: February 2003

The alignment of crystallites in fims of PVF2 prepared by a drawing and rolling technique developed previously for obtaining a single-crystal-like orientation, has been examined using x-ray pole figures. Comparison of the pole figures for the drawn-rolled film with those obtained from a drawn-only film shows that the β-phase crystals, initially arranged in a cylindrically symmetrical pattern in the drawn-only film, have been transformed into a (310)[002] texture upon rolling and annealing. Additionally, the pole figures reveal residual α-phase crystals exhibiting an (020)[002] orientation.
Spatial characteristics of displacement cascades in metals
Authors: Benedek R.
Published: February 2003

The binary-collision simulation code marlowe has been applied to study spatial characteristics of displacement cascades in fcc metals, particularly Cu. Mean densities of vacancies and interstitials 〈Cv〉 and 〈Ci〉 expressed in terms of radii of gyration of the defect configurations, have been determined as functions of cascade energy. In Cu, 〈Cv〉 decreases from ∼6×10−2 to ∼4×10−4 for energies between 1 and 150 keV, whereas 〈Ci〉∼3×10−3 is roughly constant at energies below 20 keV and approaches 〈Cv〉 asymptotically at higher energies. Although 〈Cv〉/〈Ci〉 decreases with energy, the mean vacancy-interstitial separation Riv is relatively constant. This result supports the classical picture of depleted zones in which increasing numbers of vacancy clusters surrounded by clouds of interstitials are formed as the energy is increased. Perspective plots of the defect configurations in individual cascades presented here also support this picture. Channeling is concluded to have a small effect on 〈Cv〉, but strongly influences the skewness of damage depth profiles. Results are presented for the cascade contraction factor δ. The tendency to form defect clusters and subcascades is discussed.
Surface crystallization and magnetic anisotropy in amorphous Fe40Ni38Mo4B18 ribbons
Authors: Nam Ok Hang , Morrish A. H.
Published: February 2003

The magnetic anisotropy in amorphous Fe40Ni38Mo4B18 (METGLASR 2826MB) has been studied by the determination of both surface and bulk properties using Mössbauer, x-ray, and density measurements. The onset of bulk crystallization is preceded by surface crystallization in conjunction with which magnetic anisotropies with easy directions perpendicular and parallel to the ribbon plane develop in the ribbon bulk and surface layers, respectively. It is proposed that the anisotropies, also observed for other amorphous ribbons, originate from compressive and tensile stresses appearing in the bulk portion and surface layers, respectively, as a result of the formation of higher-density crystalline surface-layers. The compressive and tensile stresses produce the perpendicular and parallel anisotropies in the ribbon bulk and surface layers, respectively, through positive magnetostriction.
Magnetostriction of Co80−xTxB20 (T = Fe, Mn, Cr, or V) glasses
Authors: O’Handley R. C. , Sullivan M. O.
Published: February 2003

Magnetostriction measurements as a function of temperature and composition are reported in non-crystalline Co80−xTxB20 alloys (T = Fe, Mn, Cr or V with 0⩽x⩽12 at. %). The room temperature saturation magnetostriction λs changes sign with the substitution of Fe, Mn or Cr for Co in Co80B20 glass. These results are well described by the virtual-bound-states (VBSs) introduced above the 3d band by the light T solutes. The positions of 3d↑ (3d majority spin) VBS with respect to the Fermi energy is established. The magnetostrictions of Co72Mn8B20 and Co70Cr10B20 glasses (negative at 295 K) also change sign with increasing temperature. This is the first direct observation of magnetostriction-compensation temperatures in non-crystalline metals. The existence of these magnetostriction compensation temperatures is interpreted to be a consequence of the different temperature dependences of single-ion and two-ion contributions to λs.
Magnetic properties of glassy Fe-Be-B alloys
Authors: Hasegawa Ryusuke
Published: February 2003

Fully noncrystalline Fe80BexB20−x (0⩽x⩽12) and Fe82−yBeyB18 (0⩽y⩽10) alloys have been synthesized by liquid-quenching from the melt. Based on the mass density, thermomagnetization, magnetostriction, x-ray diffraction and differential scanning calorimetry data, it is suggested that Be atoms can occupy Fe sites up to 2–4 at.%, beyond which they apparently replace B atoms. The effects of Be addition to the glassy Fe-B system are significant, including a large reduction of the magnetostriction.
Magnetic and crystallization behavior of Be-substituted Fe82B18 metallic glasses
Authors: Severin C. S. , Chen C. W. , Bevolo A. J. , Lin M. C.
Published: February 2003

Substitution of Be for B in the amorphous binary alloy Fe82B18 was observed to cause an initial increase in saturation magnetization (Ms) to a maximum of 200 emu/g at 4.2K, followed by a decrease for alloys with more than 4 at.% Be. Meanwhile, the Curie temperature of the Fe82B18−y Bey alloys decreased progressively with the Be content. These changes in Ms and TC differ from those observed in the Fe-B-M′ metallic glasses, where M′ is another metalloid (P, C, Si or Ge). Results from Auger electron spectroscopy and Mössbauer experiments confirmed the reversal trend detected in the magnetization measurements. Combining all these results enables us to attribute the initial increase in Ms to a smaller charge transfer from the Be atoms than that from the B atoms to Fe and the subsequent decrease in Ms to a possible clustering of the Be atoms at higher concentrations. The annealing behavior for the present alloys is described in terms of crystallization stages and the phases formed.
The temperature dependence of magnetization of amorphous Fe5Co70Si15B10 ribbons
Authors: Mei L. M. , Zhang W. X. , Kuo Y. C.
Published: February 2003

We have measured the temperature dependence of magnetization and coercive force of amorphous Fe5Co70Si15B10 ribbons in the intermediate temperature region below the Curie point. The M(T) curves manifest a plateau in the temperature region between 220 and 300 C in relatively low fields of technical saturation, i.e., M(T) is nearly constant. The plateau of M(T) curves from d.c. measurements disappears in higher fields. The M(T) curves have been analyzed by the use of a modified molecular field theory. They suggest the coexistence of a ferrimagnetic phase with a ferromagnetic phase. The ferrimagnetic phase has a TN at 513K, and TC at 640K, which is experimentally indistinguishable from TC of the ferromagnetic phase. On the Hc(T) curves, the coercivity decreases slightly with increasing temperature at first, then increases sharply up to a maximum value near 563K.
Micromagnetism and microstructure of amorphous alloys (invited)
Authors: Kronmüller H.
Published: February 2003

In amorphous ferromagnetic alloys the characteristic properties of magnetization processes and of the hysteresis loop are sensitively influenced by fluctuations of material properties and defect structures. A detailed analysis of experimental results on the basis of the theory of micromagnetism for inhomogeneous systems shows clearly that the ferromagnetic phase transition is mainly influenced by intrinsic exchange fluctuations whereas the characteristic properties of the magnetization curve are governed predominantely by defect structures. The defect structures are identified as agglomerates of the free volume which are formed during the rapid quenching process.
Kinetics of low temperature structural relaxation in two (Fe-Ni)-based metallic glasses
Authors: Chen H. S.
Published: February 2003

Structural relaxation processes below the glass transition temperature have been investigated calorimetrically via isothermal annealing and the time shift method for (Fe.5Ni.5)75P16B6Al3 and Fe40Ni40P14B6 glasses. The relaxation spectra are described by broad distributions in both activation energies and frequency factors. The low temperature anneals stabilize a portion of the relaxation spectrum and the annealed sample upon heating shows an endothermic reaction above the annealing temperature. The effects of successive annealing are additive provided that the anneals are followed by a lower temperature one. The results may account for many aging behaviors, such as the wide variation in activation energies, ’’reversibility’’ in Curie temperature and the cross-over phenomenon.
Magnetoelastic waves in amorphous tape cores carrying electric current
Authors: Dalpadado R. N. G. , Shirae K.
Published: February 2003

Magnetoelastic effects in amorphous tape cores carrying electric current were studied. A sample is Metglas 2826 MB Fe40Ni38Mo4B18 (55cm×12mm×50μm) transverse field annealed at 3000 °C. The experimental arrangement consists of a transmitter coil that is dc-biased and a receiver coil magnet-biased for maximum gain. Excited by sinusoidal current in standing-wave mode, the peak resonant frequency is typically 45 kHz. The following main phenomena are observed for dc or low frequency currents (Iz) through the core, where fz≪fex: (a) an increase in the resonance peak output voltage compared with Iz = 0, (b) an increase in the Q-factor, (c) a hysteresis in the output voltage, (d) a hysteresis in the phase, (e) a hysteresis in the resonant frequency. In the above, the continuously varying phase and amplitude were recorded simultaneously for Iz. Additionally, the application of mechanical stress, by making the tape core circular at the transmitter end, gives improved output amplitude and Q. The enhancements in Q and amplitude occur in the region of hysteresis in amplitude, phase, and frequency. The applied core-current and mechanical bias fields constitute useful parameters in the study and application of magnetoelastic phenomena.
Field-induced magnetic phase transitions in FeCl3
Authors: Johnson P. B. , Friedberg S. A. , Rayne J. A.
Published: February 2003

The ac susceptibility of FeCl3 along the c-axis has been measured as a function of temperature for static magnetic fields Hc up to 57 kG in the same direction. Temperature sweeps from 4.2 K to 12 K for fixed values of Hc reveal a line of antiferromagnetic-paramagnetic transition points in the Hc-T plane, rising rapidly from TN(0) = 8.83±0.05 K with increasing field. Isothermal field sweeps above 1.1 K show susceptibility peaks whose locus resembles the spin-flop boundary of a simple low-anisotropy antiferromagnet. The spin-flop field increases from 39.6 kG at 1.1 K to 44.5 kG at an apparent bicritical point near 8.2 K. A portion of a spin-flop paramagnetic phase boundary up to 57 kG has also been observed. These results are consistent with previous Mössbauer data.
New magnetic and structural results for uniformly spaced, alternatingly spaced, and ladder-like copper (II) linear chain compounds (invited)
Authors: Hatfield William E.
Published: February 2003

Results of recent synthetic, structural, and magnetic work on exchange coupled copper (II) ions bridged by nonmagnetic ligands are discussed, including the quasi-linear chain compound bis (dimethyldithiocarbamato) copper (II) in which the copper (II) ions are antiferromagnetically exchange coupled. An unusual correlation exists in the structural and magnetic data for [Cu(dmtc)2]∞ and other known sulfur bridged copper compounds. Data are presented for the alternatingly spaced linear chain compounds di-μ-chlorobis-(4-methylpyridine)copper (II), and a series of dionebis-(thiosemicarbazato)copper (II) compounds. Exchange coupling constants and alternation parameters were obtained from expressions which were empirically generated from calculations on rings of ten S = 1/2 ions for kT/‖J‖≳0.5 and J<0. Finally, new results for recently discovered spin ladder systems are presented.
Neutron diffraction studies of the modulated magnetic structures of CeSb and Nd metal (invited)
Authors: Lebech Bente
Published: February 2003

The magnetic phase diagram of CeSb, which has been determined by neutron diffraction and other experimental techniques, is briefly reviewed and related to some of the theoretical models that have been developed to account for it. The results of neutron diffraction studies of Nd metal are also summarized. The data is shown to be consistent with the theoretical prediction that between 9 K and TN there exist two magnetic phases (TN = 19.9 K; T2 = 19.3 K). A discussion is given of some of the difficulties that arise when trying to design a model of the magnetic structure that fully explains all the experimental data. Attention is paid to the prediction of renormalization-group theory that two dimensionally modulated magnetic structures exist in Nd. It is suggested that although there is no direct experimental evidence for the existence of such structures in Nd, none of the existing experimental data preclude this possibility.
Magnetic phase transitions in the Pd2−xCuxMnIn system
Authors: Webster P. J.
Published: February 2003

The Heusler alloys have the L21 structure and occur at the compoistion X2MnZ. The majority, such as Cu2MnIn, are ferromagnetic with a moment of about 4 μB at the Mn sites but some, such as Pd2MnIn, are antiferromagnetic. The Pd2MnIn1−xSnx and Pd2MnIn1−ySby [1,2] series have magnetic structures that change from antiferromagnetic fcc type 2 to type 3A to ferromagnetism as the proportions of the Z site atoms In/Sn/Sb are varied. Recently two models have been proposed to explain the 3d exchange interactions in Heusler alloys. Stearns [3] suggests a model with three interactions and the X atoms playing a dominant role. Price [4] proposes a single interaction dependent only upon the average conduction electron concentration. Results are presented of magnetic and neutron diffraction measurements made on the new series Pd2−xCuxMnIn, in which the conduction electron concentration is varied via the X rather than the Z sites. The changes in magnetic structure observed are similar to those that occur in the series Pd2MnIn/Sn/Sb. The implications of the results are discussed.
Magnetic structures of Y6(Fe1−xMnx)23 compounds
Authors: Hardman K. , Rhyne J. J. , James W. J.
Published: February 2003

Neutron diffraction studies of eleven compounds across the compositional range of the Y6(Fe1−xMnx)23 system reveal the presence of substantial preferential atomic ordering of Fe and Mn atoms on the four transition metal crystallographic sites. Throughout the entire compositional range, Mn atoms prefer to occupy the f2 site and Fe atoms the f1 site. Neutron diffraction profile refinements show no long range magnetic ordering occurring in the compositional range from x = 0.4 to 0.75 as a consequence of the sharply reduced exchange interactions in the ternary compounds. The average Fe moments on each of the sites are reduced in the Fe-rich ternaries. The manganese atoms are nonmagnetic. In the Mn-rich ternaries the Fe atoms have no spontaneous moments and the Mn moments are decreased dramatically from Y6Mn23.
Co energy and magnetization anisotropies in RCo5 intermetallics between 4.2 K and 300 K
Authors: Alameda J. M. , Givord D. , Lemaire R. , Lu Q.
Published: February 2003

The magnetocrystalline anisotropy has been known for a long time to be very large in the RCo5 intermetallics. The recent availability of high D.C. magnetic fields up to 200 kOe has enabled us to carry out an extensive experimental study of the energy and magnetization anisotropies in YCo5 from 4.2 K to 300 K. The magnetization anisotropy reaches 4% at 4.2 K. From a polarized neutron study on NdCo5 we find that this anisotropy of magnetization originates mainly from the 2c site. Previous measurements on YCo5 had shown that the orbital contribution to the 2c moment is large. Hence, we conclude that the Co magnetization anisotropy in RCo5 comes from a large orbital contribution to the magnetic moment. Finally, we account for the observed discontinuity in the magnetization at its reorientation in RCo5 ferrimagnets, and for the absence of a similar discontinuity in NdCo5 which is a ferromagnet.
Ferromagnetism in metallic intercalated compounds FexTaS2 (0.20⩽x⩽0.34)
Authors: Eibschütz M. , Mahajan S. , DiSalvo F. J. , Hull G. W. , Waszczak J. V.
Published: February 2003

Magnetic susceptibility, electrical resistivity, Mössbauer effect (ME) and transmission electron microscopy measurements in single crystals of the metal intercalated layer compounds FexTaS2 (0.20⩽x⩽0.34) are reported. The compounds are metallic, ferromagnetic and have large coercive force. ME measurements show the iron to be high-spin Fe2+, with a distribution of hyperfine fields at low temperatures. Transmission electron microscopy suggests the existence of clusters. These results may explain the diversity of magnetic preperties on nonstoichiometric intercalated compounds such as FexTaS2.
Low threshold current lead-telluride diode lasers grown by molecular beam epitaxy
Authors: Partin Dale L. , Lo Wayne
Published: February 2003

We have grown homojunction PbTe diode lasers by molecular beam epitaxy with cw threshold current densities as low as 40 A/cm2. The low current tuning rate of 1.2 cm−1/A implies good frequency stability against power supply variations. These diodes also exhibited high-temperature operation (85-K cw, 150-K pulsed), high cw output power (up to 3.5 mW), and a wide cw tuning range (280 cm−1).
Ionic equilibria and decay times of neutral water clusters in moist air
Authors: Carlon Hugh R.
Published: February 2003

Ambient air humidified by boiling water can contain high concentrations (106–107/cm3) of small hydrated ions for an hour or more after water vapor generation by boiling has ceased. Recent studies have shown that these high residual concentrations probably can be explained by the decomposition of molecular complexes of water (water clusters) generated by boiling, e.g., HX(H2O)c⇋(H+H2O)c+X− where X− may be a negative ion on an electron. Infrared absorption studies show that enormous populations of neutral water clusters like HX(H2O)c exist in moist air or steam (1012–1015/cm3). Thus the lifetimes of these populations can be estimated by electrical conductivity measurements of the ions in equilibrium with them. Typical data and decay curves are presented which show mean lifetimes for neutral clusters on the order of 15 min. It is shown that these neutral clusters are present in peaked statistical distributions and, in cloud-chamber operation, can serve as condensation centers for atmospheric water vapor, probably serving as nuclei for the ’’cloudlike’’ condensation first observed by Wilson.
Stainless-steel elastic constants at low temperatures
Authors: Ledbetter H. M.
Published: February 2003

For stainless steels 304, 310, and 316, longitudinal and transverse ultrasonic velocities were measured by a pulse-echo method between 295 and 4 K. From these velocities were computed five elastic constants: longitudinal modulus, shear modulus, Young’s modulus, bulk modulus, and Poisson’s ratio. All three steels show low-temperature elastic-constant anomalies, which arise from magnetic phase transitions.
Gamma-ray Compton profiles of glassy carbon and graphite
Authors: Felsteiner J. , Gertner I.
Published: February 2003

Compton profiles of glassy carbon and polycrystalline graphite were measured with 60-keV 241Am gamma rays. The difference between the two profiles was found to be much smaller than a recently reported measurement with Ag Ka fluorescence radiation. A probable source for this discrepancy is the underestimation of multiple scattering effects in the Ag Ka measurement.