bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of a source term on forced boundary diffusion
Authors: Zee R. H. , Lee-Whiting G. E.
Published: July 2002

The partial differential equation governing the one-dimensional driven diffusion of a step boundary is solved analytically for a finite system and an infinite system both with either a constant source or a concentration-proportional source. The solutions for the two infinite systems are in the form of error functions. The analytical solutions for the two finite systems each includes an infinite series which vanishes at long times. Effects of the source term on the electrotransport of oxygen in zirconium and the time required to reach the quasi steady-state condition are discussed. Small-time approximations for the two finite systems are also derived. These approximations are useful for small times when the two infinite series converge very slowly.
Pressure dependence of AlxGa1−xAs light emitting diodes near the direct-indirect transition
Authors: Kaliski R. W. , Epler J. E. , Holonyak N. , Peanasky M. J. , Herrmannsfeldt G. A. , Drickamer H. G. , Tsai M. J. , Camras M. D. , Kellert F. G. , Wu C. H. , Craford M. G.
Published: July 2002

High-pressure studies on high quality AlxGa1−xAs double heterostructure light emitting diodes (LEDs) grown by liquid phase epitaxy (LPE) are presented. The AlxGa1−xAs active region varies in composition from x∼0.25 to x∼0.53, i.e., through the important region of the direct-indirect crossover (x≡xc≊0.45). The pressure coefficient of the Γ conduction band is observed to decrease (∼1 meV/kbar for x∼0.25 to x∼0.53) with increasing Al concentration, which is in accord with alloy disorder and band-edge bowing. Indirect-gap (X) recombination radiation of significant intensity is observed and provides evidence for the high quality of the LPE diodes. High-pressure measurements, and the corresponding increase in energy of the direct band edge and decrease in the indirect band edge, show that the light emission is a strong function of the carrier distribution in the Γ and X conduction-band minima. Comparison LEDs fabricated from a crystal (x∼0.37) grown by metalorganic chemical vapor deposition exhibit nearly similar behavior as the LPE LEDs with application of pressure but with an order of magnitude lower light emission.
Representation of the vapor-phase axial deposition helical layer structure through a ‘‘spiral transformation’’
Authors: Potkay E.
Published: July 2002

A general transformation representative of the helical nature of the VAD (vapor-phase axial deposition) process is presented which provides the basis for a general 3D characterization of the helical layer structure and associated properties throughout the VAD boule based upon rpm, axial growth rate, shape, and properties of the deposition surface. Graphical representations provide an illustration of the basic concept and dependencies. An analytical function for the 3D VAD refractive index profile based on completely invariant steady-state deposition conditions is presented which properly exhibits both azimuthal and longitudinal phase dependencies; the VAD refractive index representation utilized by Okamoto et al. [Appl. Opt. 20, 2314 (1981)] to predict VAD transmission characteristics is shown to be a subset of this general form. Preliminary experimental substantiation of the transformations validity for the representation of (VAD) helical layer structure is provided in the ripple characteristics of preform profiles as well as cross-polarizer photographs. A practical application exists in extending the characterization of the deposition process such that the resultant VAD helical structure in the boule/preform/fiber is predictable and controllable. The distribution of the helical structure in the preform/fiber in fact fingerprints several aspects of the deposition process.
Effects of stress on magnetically induced velocity changes for ultrasonic longitudinal waves in steels
Authors: Kwun H.
Published: July 2002

Effects of both uniaxial tensile and compressive stresses on the magnetically induced velocity changes for 10-MHz ultrasonic longitudinal waves were investigated in specimens of ASTM A-36, SAE 4340, and HY-80 steels. The magnetically induced ultrasonic velocity changes were found to exhibit characteristically different stress effects depending on the magnitude and sign, i.e., tensile or compressive, of the stress and the relative orientation between the stress and applied magnetic field . The effects of a compressive stress were particularly distinctive producing a prominent minimum in the velocity changes as a function of the applied magnetic field. The observed stress dependence of the magnetically induced velocity changes is qualitatively explained considering the effect of the stress and the magnetic field on the rotational motion of the domain magnetization caused by the propagating ultrasonic waves due to the magnetoelastic coupling.
Interfacial strain in AlxGa1−xAs layers on GaAs
Authors: Speriosu V. S. , Nicolet M-A. , Tandon J. L. , Yeh Y. C. M.
Published: July 2002

Detailed analysis of x-ray rocking curves was used to determine the depth profile of strain and composition in a 2500-Å-thick layer of AlxGa1−xAs grown by metalorganic chemical vapor deposition on 〈100〉 GaAs. The x value and layer thickness were in good agreement with the values expected from growth parameters. The presence of a transition region, 280 Å thick, was detected by the rocking curve. In this region, the Al concentration varies smoothly from 0 to 0.87. Measurement and control of the sharpness of such interfaces has important implications for heterojunction devices.
Magnetization and nuclear magnetic resonance (spin-echo) studies on an amorphous Co-Fe-Mn-B-Si alloy
Authors: Krishnan R. , LeDang K. , Veillet P. , Ramanan V. R. V.
Published: July 2002

Magnetization and nuclear magnetic resonance spin-echo studies were carried out on an amorphous Co-Fe-Mn-B-Si alloy ribbon. The high-field susceptibility is negligible and saturation is attained at H ∼1.6 MA/m. This would indicate that the alloy is a strong ferromagnet. At 4.2 K, the magnetic moment of the alloy corresponds to 1.13 μB per atom. From the usual values of Co and Fe moments, and based on the charge transfer model, the Mn moment is estimated to be 3.7 μB. Nuclear magnetic resonance studies also give a hyperfine field for Mn corresponding to a moment of about 3.5μB, in agreement with the magnetization values. Such a moment for Mn is indeed high and is reported for the first time in amorphous alloys. The effects of annealing and crystallization on the nuclear magnetic resonance spectra are also reported. For instance, the crystalline phase Co3B contains Mn as an impurity, a fact which is indicated by the still high value of the Mn moment. Finally, the Co-Mn coupling is shown to be ferromagnetic in both the amorphous and crystalline states.
Analyses of metalorganic chemical-vapor-deposition-grown AlxGa1−xAs/GaAs strained superlattice structures by backscattering spectrometry and x-ray rocking curves
Authors: Hamdi A. H. , Speriosu V. S. , Nicolet M-A. , Tandon J. L. , Yeh Y. C. M.
Published: July 2002

Backscattering spectrometry with channeling and x-ray rocking curves have been employed to analyze metalorganic chemical-vapor-deposition-grown AlxGa1−xAs/GaAs strained superlattice structures in significant detail. Both techniques complement each other in the precise determination of composition, thickness, and strain in the individual layers of the superlattices. In addition, the sensitivity of the two techniques allows quantitative measurements of transition regions at the interfaces of various layers. Such fine probing into thin layered superlattice structures provides essential feedback in controlling their growth.
Anisotropic phonon scattering in γ-irradiated LiF
Authors: Soltis R. , Trivisonno J. , Hauenstein R. J.
Published: July 2002

A heat-pulse technique was used to study phonon scattering in γ-irradiated LiF as a function of polarization, input power, and propagation direction. The results provide direct experimental evidence of a strong, anisotropic, polarization-dependent scattering by γ-induced defects with a frequency-dependent absorption of transverse phonons for propagation in the [111] direction.
Scattering of lateral waves by buried or submerged objects. II. The electric field on the surface above a buried insulated wire
Authors: King Ronold W. P.
Published: July 2002

The electric field on the surface of the earth in an area above a buried insulated conductor is determined when the active source is a horizontal dipole also on the surface of the earth at some distance away. This is accomplished by first evaluating the current induced in the wire by the lateral-wave field incident from the transmitter and then calculating the reradiated field just above the surface. Two orientations are considered. The field at the center of the buried conductor is (1) parallel to E1ρ(ρ,0,z) and (2) parallel to E1φ(ρ,π/2,z). In an area above the conductor, the incident, scattered and total fields are evaluated for the conditions of a laboratory model. It is concluded that the method is potentially useful for locating buried or submerged regions with significantly different wave numbers from that of the surrounding earth.
Shallow boron-doped junctions in silicon
Authors: Cohen S. S. , Norton J. F. , Koch E. F. , Weisel G. J.
Published: July 2002

Shallow boron-doped junctions in silicon have been investigated by means of secondary ion mass spectrometry, scanning electron microscopy, transmission electron microscopy, spreading resistance profiling, and four-point probe techniques. The junctions were formed by implanting BF+2 ions into n-type Si at the dose range of 1–5×1015 ions/cm2, through a thin (25-nm) screen layer of silicon dioxide. We have emphasized the higher dose range (3–5×1015 ions/cm2) as it is more relevant to processes in the current level of device integration. The use of BF+2 species and the screen oxide layer is necessary in order to form junctions whose depths xj≤0.4 μm, when conventional annealing techniques are employed. We have also examined junctions that were activated in a rapid thermal annealing system that utilizes an incoherent light source. One of the main objectives of this study is to compare conventional and rapid thermal annealing techniques. We thus evaluate the results obtained by these two methods of annealing for both the junction depth xj and the sheet resistivity Rs. Other relevant variables such as a low-temperature (77-K) implantation, surface amorphization by Si implantation, and preactivation annealing have also been examined and their effects are discussed. Based on the results of the present study, a mechanism for boron activation in silicon is discussed.
Distribution of the number of electrons in electron avalanches at voltages in excess of the sparking value
Authors: Kondo Y.
Published: July 2002

For times greater than the electron transit time, a suitable statistical theory of the total number of electrons in avalanches is presented, and compared with the results simulated by the Monte Carlo method.
Thermal characteristics of matrix-addressed liquid-crystal display
Authors: Lee M. H. , Depp S. W. , Juliana A. , Moore J. O. , Koepcke R. W.
Published: July 2002

The thermal characteristics of matrix-addressed smectic liquid-crystal cells are studied using the temperature dependence of the resistance of the heater and detector lines and compared to analytic solutions. The cell behavior is most strongly affected by the thermal properties of the substrate near the liquid crystal if the heater is at that interface. Cell features further away from the heater have a smaller influence. The cell power efficiency improves if the thermal flow through the substrate is reduced relative to the liquid crystal. The cell addressing speed can be increased if the substrate has two layers composed of a thin insulator on a conducting layer. Increasing the insulator thickness improves efficiency but reduces speed.
Phase transformations in ion-irradiated silicides
Authors: Hewett C. A. , Lau S. S. , Suni I. , Hung L. S.
Published: July 2002

The phase transformations in a number of ion-implanted and subsequently annealed silicides have been investigated. The electrical resistance change as a function of 28Si+ ion implantation has been found to correlate with the presence of a disordered state in the silicide. Epitaxial silicides such as CoSi2 were found to regrow in a layer by layer manner when implanted such that the top region was amorphous but with a single-crystal seed remaining at the bottom of the original layer. Recrystallization temperatures (defined as the temperature at which one half of the silicide has transformed) were determined by in situ electrical measurements as well as by x-ray diffraction studies. Recrystallization temperatures were found to be approximately 1/3 of the silicide melting point. Both cosputtered and implanted refractory metal silicides were also found to be governed by this rule. Under the assumption that recrystallization can be described by the Avrami equation, it was found that n, the mode of transformation index, was equal to or less than 3 for a number of crystalline silicides. We interpret this as possible evidence that a crystalline silicide is not completely amorphized by ion implantation, although the size of the crystalline nuclei may be below the conventional transmission electron microscopy resolution limit.
A new method for measuring ambipolar mobility and its implementation in p-type HgCdTe
Authors: Schacham S. E. , Finkman E.
Published: July 2002

A new method for measuring the ambipolar mobility is described. It is based on the determination of the travel time of excess carriers between two probes. Maintaining the device under a constant voltage, the travel time is depicted as the separation between two zeros on the output trace. Using this technique the ambipolar mobility of electrons in p-type Hg 0.71Cd0.29Te was measured for the temperature range of 78–256 K.
A model for the plasma-activated chemical vapor deposition process
Authors: Weling Fredy
Published: July 2002

This paper presents the results of a theoretical study of the plasma-activated chemical vapor deposition (PCVD) process used for the preparation of optical fibers. We show how the static deposition profile of silica can be computed by taking into account convection, reaction, and diffusion processes inside the glass tube. The parameters describing these processes are estimated. We examine how the deposition profile depends on the gas velocity, the reaction, and the diffusion constants. Theory and experiment are in good agreement. The calculations confirm the idea that in the PCVD process the deposit is formed from single molecules and not from clusters.
Output power and saturation parameter of an air-breathing electric discharge CO2 laser
Authors: Hara Hiroshi , Sugii Masakatsu
Published: July 2002

The output power and saturation parameter of an air-breathing electric discharge CO2 laser are reported. An output power of 79 W was obtained with an energy-conversion efficiency of 5.1% and a specific power of 12.5 J/g. The saturation parameter of ∼30 W/cm2 was determined by measuring the gain with and without lasing. We also discuss the influence of He- and Ar-gas addition on the output power of the present laser.
Stimulated Raman scattering from a relativistic electron beam
Authors: Schill Robert A. , Seshadri S. R.
Published: July 2002

A plane transverse electromagnetic wave propagating antiparallel to a cold relativistic electron beam extending over all space is backscattered from a negative energy space-charge wave into a frequency up-converted plane transverse electromagnetic wave. Parametric and nonlinear three-wave interactions are analytically examined in a systematic manner taking account of all the nonlinearities. With the inclusion of appropriate phenomenological collision terms, and frequency and wave-number mismatches, the amplitude threshold, the growth rate, and the saturation values are determined. A heuristic estimation reveals wave amplification to be limited by the beam velocity. An expression for maximum amplification is obtained. Representative numerical results are presented to display the characteristics of the nonlinear three-wave interaction.
Pressure-dependent electron attachment and breakdown strengths of unary gases and synergism of binary gas mixtures: A relationship
Authors: Hunter S. R. , Christophorou L. G.
Published: July 2002

The relationship between the pressure-dependent electron attachment rate constants which have been observed in 1-C3F6 and in several perfluoroalkanes and the uniform field breakdown strengths (E/N)lim in these gases is discussed. Also discussed are the various types of synergistic behavior in (E/N)lim which have been observed in binary dielectric gas mixtures. For the latter, a new mechanism is outlined which explains the synergism observed in several gas mixtures where the (E/N)lim values of the mixtures are greater than those of the individual gas constituents, which we call positive synergism. Model calculations are presented which support this mechanism and can be used to explain the pressure-dependent synergistic effects which have been reported in 1-C3F6/SF6 and other gas mixtures. Experimentally observed ion–molecule reaction processes for several gases are discussed which support the proposed mechanism. Based on this mechanism, we outline several conditions which must be fulfilled in order to observe positive synergistic behavior in dielectric gas mixtures.
Temperature dependence of the critical magnetic field in polycrystalline ferrites
Authors: Baca Gloria , Valenzuela R. , Escobar M. A. , Magaña L. F.
Published: July 2002

The critical magnetic field Hcr which separates the low-field reversible magnetization range from the irreversible, hysteretic part of the ferromagnetic B-H diagram is conveniently described by the Globus model, by attributing a reversible bowing mechanism of magnetic domain walls to the former range, and a depinning and displacement for the latter one. A simple calculation led Globus to expressions for Hcr and initial (reversible) magnetic permeability μ. In this paper, we show that the thermal dependence of the critical magnetic field can be given in terms of the saturation magnetization and the initial magnetic permeability. We use experimental results of saturation magnetization and initial permeability of NiFe2O4 and compare to experimental results of critical magnetic field as a funciton of temperature. A remarkable agreement is observed when we use a more exact approximation for the initial permeability expression than Globus’.
Effect of impurity concentration in calculation of coercivity (abstract)
Authors: Torfeh-Isfahani M. , Della Torre E.
Published: July 2002

A coercivity model for iron when corrected for micromagnetic effects yielded a value of approximately 2.5 mOe for 100 Å impurities in concentrations of 1016/m3. This reasonable result gave impetus to explore this model further. This paper studies the variation in calculated coercivity with impurity concentration for iron and magnetic garnets. The result of this computation shows a great increase in the coercive force as the density increases. Results are compared with recent experimental data on garnets.
Factors affecting core losses in oriented electrical steels at moderate inductions (invited)
Authors: Foster K. , Littmann M. F.
Published: July 2002

The effects of sheet thickness, orientation, grain size, silicon content, stress, domain control, and surface condition on core losses of both regular grain oriented (RGO) and high permeability (HGO) silicon steels in the induction range of 1.0 to 1.5 T were reviewed. Where possible, the effects of these factors were discussed in terms of total loss PT hysteresis loss Ph eddy current loss Pe and eddy current loss anomaly factor η. The effect of decreasing sheet thickness t is dependent on Pe∼t, while for increased silicon content, Pe∼1/ρ. Improvements in orientation are shown mainly to decrease Ph, with the effect being larger at 1.5 T and above than at lower inductions. Grain size reductions, applied tensile stress, and other domain control methods are mainly aimed at reducing the 180° domain wall spacing 2L which in turn decreases η. Improved surface condition decreases both Ph and Pe, but mainly above 1.5 T.
Inductive observation of transitions from [100] magnetic domains to [010] and [001] in silicon-iron
Authors: da Cruz S. P. , Livi F. P.
Published: July 2002

Transitions of the magnetization from the [100] to [010] and [001] directions were observed by inductive methods. Enhancement of the signals was obtained by a crossed excitation-signal windings arrangement. The results are interpreted in terms of the internal [010], [001] domains.
Dependence of the anhysteretic magnetization on uniaxial stress in steel
Authors: Dobranski L. G. , Jiles D. C. , Atherton D. L.
Published: July 2002

As part of an investigation into the effects of stress on magnetic properties, the stress dependence of the anhysteretic magnetization of three samples of ferromagnetic constructional steel was measured. Measurements were taken using a specially designed apparatus which enabled small samples to be subjected to uniaxial stresses of up to 3.2×108 Pa while held between the pole pieces of a conventional 2T laboratory electromagnet with a pole gap of 70 mm. In each case, the anhysteretic magnetization decreased under compressive stress but increased slightly under tensile stress at low fields. Compared with hysteresis curves, the anhysteretic has a particularly simple form which can be modeled using an equation given previously. The results allowed the stress dependence of three of the four parameters governing hysteresis to be determined.
Magnetic and mechanical properties of rapidly quenched microcrystalline Alfer ribbons
Authors: Yamashiro Y. , Teshima N. , Narita K.
Published: July 2002

Ribbon-form 13% Al–Fe alloy was prepared by a rapid quenching single roller method. The ribbon obtained had dimensions of 50–60 μm thick, 1–3 mm wide, and a few meters long. The annealing temperature dependence of magnetic, electrical, and mechanical properties were examined from 900 to 1200 °C. After annealing at 1000 °C for one hour in vacuum of 1×10−5 Torr, the best magnetic properties were obtained: the saturation magnetostriction was 52×10−6, the coercive force was 0.8 Oe, and the initial permeability was about 500. The electric resistivity was as high as 105–110 μΩ cm. The ribbon was notably flexible and could be wound around a rod of 0.5 mm diameter.
Mössbauer effect in R2Fe14B compounds
Authors: Pinkerton F. E. , Dunham W. R.
Published: July 2002

We report room temperature Mössbauer spectra for R2Fe14B compounds with R=Y, Ce, Pr, Nd, Gd, Dy and Ho. The hyperfine fields are obtained for the six inequivalent iron sublattices in the R2Fe14B crystal structure. The internal magnetic fields scale with the Curie temperature, but the spectra are otherwise virtually independent of the rare-earth component. These results indicate that the electronic configurations of the iron atoms are nearly the same for all these compounds, and that the iron 3d shell dominates the conduction electron polarization contribution to the internal fields.
Densification and magnetization of rare earth magnets
Authors: Narasimhan K. S. V. L. , Lizzi T.
Published: July 2002

Hot isostatic pressing of SmCo5 magnets has been evaluated as a means for increasing the density, remanence, and energy product of rare earth magnets. The results indicate 99% density can be achieved without loss in the magnetic properties. Magnetization studies up to 100 kOe were conducted on SmCo5 magnets and the results indicate that fields in excess of 60 kOe are required to achieve maximum values of remanence in a magnetically demagnetized magnet as is produced by running a hysteresis loop. Thermally demagnetized magnets, however, require less than 15 kOe to realize the full potential for all practical applications.
Effects of a finitely permeable back layer on auxiliary pole reproduction of perpendicular recording
Authors: Monson J. E. , Iwasaki S.
Published: July 2002

Addition of a highly permeable back layer to anisotropic Co-Cr magnetic media has produced very high density digital recording performance in perpendicular recording systems using main pole/auxiliary pole heads. Direct calculations of the reproduce flux sensed by the auxiliary pole are presented as a function of back layer permeability and thickness. Calculated results show a slight shielding of the reproduce flux by the back layer and are in good agreement with experimental data. Simple reluctance models are developed which show the function of the back layer in improving reproduce performance.
Noise characteristics in Co-Cr perpendicular recording media
Authors: Aoyama M. , Tagami K.
Published: July 2002

Noise characteristics in Co-Cr and Co-Cr/Ni-Fe perpendicular recording media were theoretically analyzed, based on an uncorrelated particle magnetization model. The analyzed results were compared with experimental results. Marked differences in noise spectra were found between single layer and double layer media, especially in the long wavelength region. The measured noise and signal spectra in a Co-Cr/Ni-Fe double layer medium were close to the numerically analyzed values for perpendicular magnetization, rather than for longitudinal magnetization. This indicates that the magnetization in the Co-Cr layer is directed almost perpendicularly. Furthermore, the measured noise power decreased with increasing the medium perpendicular anisotropy, which is closely related to the medium crystal orientation. As a conclusion, noise from Co-Cr perpendicular recording media is attributed to the medium grain magnetization direction dispersion, where the magnetizations are almost perpendicular to the medium surface.
Effects of helium ion double implantation on CD bubble device
Authors: Zhang S. J. , Humphrey F. B.
Published: July 2002

Effects of helium ion double implantation on contiguous disk (CD) bubble devices have been examined by x-ray diffraction, FMR, and annealing techniques. The results were compared with static and dynamic performance of CD devices. Samples had a composition of Sm0.29Lu0.40Y1.42Ca0.89Fe 4.11Ge0.89O12 with stripe width 3 μm, Hc=143 Oe and were implanted with 190-keV helium at 4.5×1015 He+/cm2 and 100-keV helium at 3 ×1015 He+/cm2. X-ray diffraction curves show that He ion double implantation gives a more uniform strain profile with a main strain of 0.84% and a strain induced anisotropy field of 3100 Oe. FMR spectrum results show an implantation induced anisotropy field of 3185 Oe which is in good agreement with x-ray diffraction result. The main strain decreases linearly with the annealing temperature Ta extrapolating to zero at l000 °C. The implantation induced anisotropy field also decreases with Ta, but exhibits an excess of 600 Oe over the strain anisotropy field. This excess is attributed to the suppression of growth induced anisotropy by He ion implantation. The measurements of the bubble collapse field and propagation margin on a CD track with 12-μm period at 100 kHz show that annealing at temperatures higher than 300 °C causes the performance of CD devices to degrade very rapidly. The margin becomes narrow and the minimum drive field increases. Annealing above 500 °C will kill the device.
A three-dimensional computer simulation of a translating magnetic bubble
Authors: Ronan G. , Konishi S.
Published: July 2002

The dynamic characteristics of a translating magnetic bubble are studied by a three-dimensional numerical solution of the equations of motion for a twisted domain wall structure. The azimuthal angle of magnetization φ and wall center position q for a bubble of radius 3 μm are defined at 3552 points distributed regularly on the domain wall. Demagnetizing and stray in-plane fields are calculated by assuming a circulating current density of 2M emu/cm flowing on the domain wall and integrating Biot–Savart’s Law over the wall surface. A typical (YSmLuCa)3(GeFe)5O12 garnet of film thickness 4.27 μm is assumed. Instantaneous bubble skew angle and velocity are illustrated at drive fields from 0.5 to 4.0 Oe/μm. Bubble dynamics are seen to fall into three categories, transport without Bloch curve nucleation, with Bloch curve propagation, and with Bloch curve punch through. At low drive field both skew angle and velocity are in good agreement with earlier theory. At high drive field the time averaged velocity saturates as the instantaneous velocity oscillates due to Bloch curve punch through. A comparatively high saturation velocity of 35 m/s and an instantaneous peak velocity of 54 m/s are observed.
A new multicolor electroluminescent device
Authors: Hirate Takashi , Ito Takahiro , Hikasa Mitsutoshi
Published: July 2002

A new multicolor ac thin-film electroluminescent device is hereby proposed. This device differs from usual devices in the structure of its active layer, i.e., the additional layer (‘‘gate layer’’) is buried in ZnS active layers. Thus, the structure of the device is a glass substrate: SnOx-Y2O3-ZnS:SmF3-gate layer-ZnS:ErF3-Y2O3-Al. In particular, when the gate layer is a thin SmF3 film (approximately 500 Å) or an extremely thin Al film (approximately 100 Å), the emission color of the device continuously varies between red and green with the driving voltage or frequency.
Influence of thermal ions on the n
d3/2-n
f5/2 and n
d3/2-n
g7/2 microwave transition of sodium
Authors: van Linden van den Heuvell H. B. , Tran N. H. , Kachru R. , Gallagher T. F.
Published: July 2002

We have studied the dipole-allowed nd3/2-nf5/2 and the dipole-forbidden nd3/2-ng7/2 transitions of sodium in the presence of thermal ions for n=15–17. Although the cross sections for the relevant ion–Rydberg atom collisons are too small to influence the observed transitions, these microwave resonance measurements indicate that there is a remarkable influence of even very low densities, 105 cm−3, of ions on the atoms. For instance, the d-g transition can be easily driven with a single photon, and the d-f and d-g transitions are shifted and broadened. Furthermore, the thermal sodium ions destroy the interference fringes obtained with the Ramsey method of separated oscillatory fields. Although these results are incompatible with reasonable estimates of ion-atom collision cross sections, they may be explained quantitatively in terms of the time-averaged charge of the ions.
Three-mode coupling in a dielectric slab waveguide with doubly periodic surface corrugations
Authors: Yasumoto K.
Published: July 2002

The characteristics of a three-mode coupling in a dielectric slab waveguide attached doubly periodic surface corrugations are investigated. The coupled-mode equations governing the first-order Bragg interactions of three TE modes are systematically derived with the help of perturbation procedure. For the case where the waveguide is symmetric and the three TE modes are lowest even modes, the coupled-mode equations are solved to obtain the reflection and transmission characteristics of the periodic waveguide of finite length. The results are compared with those of the two related two-mode couplings in a dielectric slab waveguide with a singly periodic surface corrugation.
Effective gettering of gold in silicon at 900 °C by low-current corona discharge
Authors: Falster R. J. , Modlin D. N. , Tiller W. A. , Gibbons J. F.
Published: July 2002

The application of microampere level corona generated currents at elevated temperatures in an argon atmosphere was found to indicate a rapid segregation of dissolved Au impurities out of the bulk of intentionally Au-doped silicon wafers into the near surface regions on both sides of the wafers. Complete removal of the Au occurred in less than 15 min with a current of 5 μA at 900 °C. A ‘‘kick-out’’ mechanism due to the generation of Si interstitials is considered as a possible explanation for these results.
A mechanism for radiation-induced degradation in GaAs field-effect transistors
Authors: Buot F. A. , Anderson W. T. , Christou A. , Campbell A. B. , Knudson A. R.
Published: July 2002

GaAs field-effect transistors (FETs) exposed to 40 α/sec for about 60 sec in the gate region revealed burnout from under the gate to both the drain and source. To explain this result, we show by using a 2D numerical FET simulation that a single event, particularly normal to the gate, has all the harmful electrical and thermal transients as that of a reverse gate-voltage pulse or positive drain-voltage pulse. The latter two are well known to initiate burnout failure mechanisms in GaAs FETs, depending on duty cycle and peak power applied. The onset of burnout due to a succeeding single event may be further aided by the ionization-enhanced outdiffusion of deep-level traps to the active channel during a series of single events. The experimental data, principally from SEM analysis and degradation of I-V characteristics, seem to support the thermal runaway burnout mechanism proposed in this paper. Other mechanisms previously suggested are either ruled out or deemed inadequate. A high-fluence radiation-hardened structural FET design is suggested.
Lattice excitations during laser annealing of semiconductors
Authors: Paranjape V. V. , Panat P. V.
Published: July 2002

During laser annealing of a semiconductor, lattice vibrations of the material are excited. It is shown in this paper that these excitations occur in a restricted range of the vibrational spectrum. The excitation number for the spectrum is derived. It is demonstrated that the effective temperature for each mode can be defined and that the temperature varies over the spectrum from its undisturbed equilibrium value TL to a value as high as T, the temperature of the laser-induced electron-hole plasma.
Tunneling and zero-point vibrations of 180°-domain walls in ferromagnetic materials
Authors: Riehemann Werner , Nembach Eckhard
Published: July 2002

The experimentally established dependence of the velocity v of 180°-domain walls in four ferromagnetic Ni-base alloys on the applied magnetic field H and on temperature T is analyzed. T ranges from 1.3 to 5 K. The relation v(H,T) is governed by the interaction of the domain walls with obstacles. The temperature dependence of the walls’ release from these obstacles is derived from Gibbs’ formula. Below 2 K, quantum-mechanical effects noticeably enhance the release of domain walls from obstacles. This is analyzed in two alternative models: (i) tunneling of the domain wall is allowed for; (ii) the wall is treated as a harmonic oscillator, whose eigenstates are calculated quantum-mechanically. Zero-point vibrations are included in this model. These models lead to two alternative functions v(H,T). Both of them represent the experimental data nearly equally well, though the agreement for model (i) (tunneling) is slightly better. Fitting the two functions to the data yields two sets of adjustable parameters. An analysis of their magnitude favors model (i), indicating that in the investigated nickel-base alloys tunneling may be more important than zero-point vibrations for the mobility of 180°-domain walls.
Unified theory of kink dragging with a special reference to the flow stress and the Snoek–Köster relaxation in anisotropic body-centered-cubic metals with heavy interstitials
Authors: Ogurtani Tarik Ö. , Seeger Alfred K.
Published: July 2002

The drag force acting on a kink moving rigidly and uniformly along the dislocation line and in the atmosphere of mobile octahedral (heavy) interstitials is investigated numerically in anisotropic body-centered-cubic metals. It is shown by extensive computer modeling experiments that the drag force versus normalized kink velocity plot goes through a maximum which is composed of three subpeaks, one acoustic and two optical in character. The acoustic part and the optical mode-2 are strongly and selectively associated with the isotropic and the pure shear parts of the elastic dipole tensor of the interstitial species, respectively. An extremely accurate and the concise analytical expression is deduced for the linear viscosity regime which exhibits the behavior of Navier–Stokes fluids, which can be used directly in Snoek–Köster relaxation. The flow stress theory of Seeger for the ultrahigh-purity body-centered-cubic metals is extended and coupled with the present treatment of the kink dragging which yields an excellent agreement with the dynamical strain aging experiments in Fe-C and Fe-N alloys.
Pulsed proton-beam annealing of Ir and IrxV100−x thin films on silicon
Authors: Brat T. , Eizenberg M. , Fastow R. , Palmstrom C. J. , Mayer J. W.
Published: July 2002

A pulsed proton beam was used to anneal Ir and IrxV100−x thin films deposited on Si single crystals. Compound phases were produced by local melting of the metal-Si interface. Phase identification was carried out by x-ray diffraction; while component distribution was determined by Auger electron spectroscopy and Rutherford backscattering spectrometry. The morphology of the silicide layers was examined using transmission electron microscopy; and Schottky barrier heights were determined by current-voltage measurements. At intermediate deposited energy densities (∼0.5 J/cm2) a controlled interfacial reaction was observed. In the case of Ir/Si, amorphous IrSi as well as polycrystalline IrSi and Ir2Si3 was detected in the reacted region. For the codeposited IrxV100−x film, with x=80 and 50, the interfacial layer reacting with the Si substrate maintained the Ir : V ratio of the as-deposited film. This is in contrast to the case of furnace annealing where preferred accumulation of Ir is observed.
Preparation of platinum silicides by reactive sputtering of Pt in SiH4 plasma
Authors: Budhani R. C. , O’Brien B. P. , Doerr H. J. , Deshpandey C. V. , Bunshah R. F.
Published: July 2002

Platinum-silicon alloys have been prepared over a wide composition range by reactive magnetron sputtering of platinum in a SiH4 plasma. Studies on the stoichiometry of the films show that it depends sensitively on the silane partial pressure and the cathode potential. An analysis of the intensities of the emission lines of platinum and hydrogen present in the plasma indicates that at lower silicon concentrations the stoichiometry of the film bears a one-to-one correspondence with the stoichiometry of the plasma. X-ray diffraction studies on the films deposited at room temperature show metastable products such as extended solid solutions on either side of the equilibrium phase field and the formation of a bcc phase (a=4.169 Å) for the Pt67Si33 alloy. Stoichiometric intermetallic phases Pt2Si, PtSi, and PtSi2 have been synthesized by depositing the films at 100, 300, and 500 °C, respectively.
Donor-induced disorder-defined buried-heterostructure AlxGa1−xAs-GaAs quantum-well lasers
Authors: Meehan K. , Gavrilovic P. , Epler J. E. , Hsieh K. C. , Holonyak N. , Burnham R. D. , Thornton R. L. , Streifer W.
Published: July 2002

A simple form of a buried heterostructure AlxGa1−xAs-GaAs quantum-well laser is described that is realized by impurity-induced layer disordering (donor-induced disordering). The layer disordering [and the resulting band-gap shift to higher energy (and lower index)] is accomplished by Si diffusion in a stripe pattern defined by a Si3N4 mask. Single-mode lasers of stripe width 3 and 6 μm are demonstrated that operate continuously at 300 K in the threshold current range of 10–25 mA and with single-facet power levels as high as 10–20 mW.
Electron mobility limits of two-dimensional electron gas in N-AlGaAs/GaAs at low temperature
Authors: Tsubaki Kotaro , Sugimura Akira , Kumabe Kenji
Published: July 2002

Using the warm electron coefficient, the electron mobility, μinel, limited only by inelastic scattering was studied for two-dimensional electron gas confined to the GaAs side of an N-AlGaAs/GaAs heterojunction. The warm electron coefficient β was measured to be 0.1–3×10−3 cm2/V2 at the temperature 4.2–30 K. The electron mobility μinel is interpreted as the upper limit obtained in the condition free of ionized impurity scattering. The relation between β and electron mobility μinel for two-dimensional electron gas is obtained as β∝μinel, when ionized impurity scattering is predominant. Combining the theoretical relations and experimental results, the electron mobility limit of a two-dimensional electron gas at 4.2 K is found to be about 9.0×106 cm2/V sec at sheet electron concentration of 8×1010 cm−2. The exponent of its temperature dependence is −1.28.
Optical detection of the magnetic resonance of color centers
Authors: Tippins H. H.
Published: July 2002

Optical detection of magnetic resonance applied to the F center in KCl is presented. The advantages and the theoretical basis of the technique of optical detection of magnetic resonance are discussed, and a description of the details of the actual spectrometer designed for the study of color centers is given. The successful observation of the optical detection of the resonance of the KCl F center is reported.
Dielectric properties of ‘‘diamondlike’’ carbon prepared by rf plasma deposition
Authors: Lamb Joel D. , Woollam John A.
Published: July 2002

Metal-carbon-metal structures were fabricated using either gold or aluminum evaporated electrodes and rf plasma (methane) deposited ‘‘diamondlike’’ carbon films. ac-conductance and capacitance versus voltage and frequency (10 Hz to 13 MHz) data were taken to determine the dielectric properties of these films. Conductance versus frequency data fit a generalized power law, consistent with both dc and hopping conduction components. The capacitance versus frequency data are well matched to the conductance versus frequency data, as predicted by a Kramers-Kronig analysis. The dielectric loss tangent is nearly constant at 0.5 to 1.0% over the frequency range from 1 to 100 kHz. The dc resistivity is above 1013 Ω cm, and the dc breakdown strength is above 8×106 V/cm in properly prepared samples.
Measurement of intrinsic signal to noise ratios for high performance rigid recording media (abstract)
Authors: Belk N. R. , George P. K. , Mowry G. S.
Published: July 2002

Measurement of the noise spectrum of high performance oxide, thin-film longitudinal and perpendicular rigid recording media have been made in order to establish the frequency dependence of the noise, the intrinsic media signal-to-noise ratio, and the practical recording density limit set by error rate considerations. For the oxide media tested, the noise spectrum was flat with frequency at 0.7 μV rms/100 μV rms signal indicating it was close to the particle size determined noise limit. For plated Co-P and sputtered Co-Re thin-film longitudinal media the noise spectrum increases with frequency. At D70 (18 KFCI) the noise was 1.25 and 1 μV per 100 μV rms signal, respectively. For the vertical media the noise contribution came from shouldering around the fundamental frequency and was 2.5 μV/10 μV rms signal at D70 (22 KFCI) and increased with frequency. The measurements were made with both inductive and magnetoresistive heads (improved sensitivity) at 900 TPI and over a 20-MHz bandwidth. D70 for the oxide media was 13 KFCI. The flying height was maintained at 9μ in. Measurements were made at narrower trackwidths to confirm the square root dependence of S/N on trackwidth. Comparisons of both dc erase and high-frequency noise spectrums are presented and contrasted for oxide and metallic media. Evidence supporting proposed theories for the source of the media noise is discussed and the implications with respect to maximum achievable areal densities (without error correction) are presented.
Read efficiency measurements for thin film heads
Authors: Maruyama T. , Ito S.
Published: July 2002

Read efficiency values for thin film heads have been measured using a readback voltage integration method. Read efficiency η can be expressed by η=Φh/Φm, where Φh is the magnetic flux linking coil turns in the head and Φm is the magnetic flux emanating from the recorded region in the media. Readback voltages were integrated digitally and converted into integrated waveforms, which correspond to Φh. High read efficiency values, 87 and 91%, were measured for a thin film head and a MnZn ferrite head, respectively, using 8-in. CoNiP plated disks at below 0.19 μm flying height and at below 5-kFRPI recording densities. Integrated waveforms for thin film heads had square shapes with overshoots and undershoots. The peak values for these overshoots and undershoots reflect pole piece configurations and/or their magnetic properties. This readback voltage integration method is efficient for evaluating thin film head performance experimentally.
Measurements of surface magnetic fields in contact perpendicular recording using a high-resolution magnetoresistive transducer
Authors: Lin C.-J. , Stukey F. W. , Sargent F. D. , Best J. S. , Bullock D. C.
Published: July 2002

A high-resolution vertical magnetoresistive transducer has been used to measure the magnetic field at the surface of rigid CoCr(Ta)/NiFe perpendicular recording media. Very sharp magnetic transitions achieved by contact recording were observed at the edges of the main pole of a single-sided main-pole-driven perpendicular head, both along and across the recording track, with transition widths (10–90%) of 240 and 390 nm, respectively.
Direct observation of magnetically distinct regions in Co-Cr perpendicular recording media using ferromagnetic resonance
Authors: Mitchell P. V. , Layadi A. , VanderVen N. S. , Artman J. O.
Published: July 2002

We have used a 30-GHz resonant cavity spectrometer to record the ferromagnetic resonance (FMR) spectra characterizing several Co-Cr films. These films, 18–22 at. % Cr in composition, were characterized by net mean anisotropy K̄ extending from negative to positive in range. K̄ and M̄S are measured by a torque magnetometer (TM) and a vibrating sample magnetometer (VSM). FMR was used to measure the relative amounts and the corresponding 2K/MS and γ values of each of the magnetic constituents in a given specimen. Using integrated FMR intensities and corresponding 2K/MS, a reasonable correlation between the TM/VSM data and FMR was achieved. An initial study on four films indicates that poorly aligned specimens (Δθ50≂8°) are composed of several distinct magnetic constituents; well-aligned specimens (Δθ50≂2°) are characterized by a single constituent. Further, samples with larger Δθ50 all seem to be characterized by at least two constituents in common: one at 2K/MS≂0, the other at 2K/MS ≂−4πMS. This research, we believe, represents the first known confirmation by FMR of positive anisotropy in such Co-Cr films.
Field of probe heads with ideal windings
Authors: Minuhin V. B.
Published: July 2002

Analytical expressions have been derived for the field of a two-dimensional electromagnet with infinitesimally thin winding located at an arbitrary distance from the pole tips. This model corresponds to a probe head with winding in the presence of vertical recording media with a highly permeable underlayer. The calculations indicate that the readback resolution of a probe head is quite inferior to the resolution of a ring head.
Three-dimensional nonlinear analysis of a permanent magnet machine by a hybrid finite-element method
Authors: Chari M. V. K. , D’Angelo J. , Neumann T. W.
Published: July 2002

Design of modern electrical machinery to operate at high power densities and optimal efficiency requires accurate performance prediction. To accomplish this objective, magnetic field analysis must be performed taking full account of three-dimensional effects and iron saturation. In this paper, a three-dimensional magnetostatic analysis using a hybrid finite-element formulation is presented. The method employs a combined vector and scalar formulation for representing the magnetic field. The analysis developed in the paper is applied to a permanent-magnet synchronous machine for evaluating the field distribution on no-load, in the body of the machine and the end region. Since the operating regime of this particular machine is in the unsaturated region, it was sufficient to implement a finite permeability case. The method described could be easily extended for the full-load case and the nonlinear algorithm implemented.