bluuebunny/crossref_metadata_2025 huggingface dataset:
Point-defect generation during oxidation of silicon in dry oxygen. I. Theory
Authors: Dunham Scott T. , Plummer James D.
Published: July 2002

In this paper, we consider how oxidation in dry O2 influences the point-defect densities in silicon. By using relationships based on the continuity equations in the oxide and applying a proposed set of boundary conditions to the oxidizing Si-SiO2 system, we derive an analytic expression for the supersaturation of interstitials during oxidation. The analysis results in an expression having the experimentally observed sublinear dependence on oxidation rate without requiring any assumptions of nonlinearity. In addition, through observations of the dependence of the linear rate constant in the linear-parabolic model of oxidation on ambient oxygen pressure, it is possible to predict how the interstitial supersaturation will vary with oxidation rate at a given temperature. A companion paper [J. Appl. Phys. 59, 2551 (1986)] compares the predictions of the model with experimental results.
Impurity bands and band tailing in n-type GaAs
Authors: Lowney Jeremiah R.
Published: July 2002

The density of states of the valence and conduction bands of n-type GaAs has been calculated for a donor density of 1017 cm−3 at 300 and 20 K. Both the donor-carrier and carrier-carrier interactions have been included. Band tails appear on both bands and the energy gap is narrowed. Calculations were also performed for a donor density of 1015 cm−3 at 300 and 20 K. These results show the formation of an impurity band at 20 K, whereas a band tail exists at 300 K.
Tandem deposition of small metal particle composites
Authors: Logothetis E. M. , Kaiser W. J. , Plummer H. K. , Shinozaki S. S.
Published: July 2002

A new method for preparing small metal particle composites (cermets) is described. It consists of many sequential depositions on a substrate of small amounts of a metal and an insulator from separate deposition sources. Under certain conditions, this method provides composites which, for metal volume fractions of less than about 0.5, consist of metal spheres with a very narrow size distribution embedded uniformly in the insulating matrix. In addition to the improved morphology of the composites, the new method also allows, for the first time, for control of metal particle size independent of metal volume fraction.
‘‘New donors’’ in silicon: An interface effect due to internal oxidation
Authors: Henry A. , Pautrat J. L. , Saminadayar K.
Published: July 2002

The analysis of Czochralski-silicon annealed in the range 500–800 °C is performed using infrared transmission, electron paramagnetic resonance and admittance spectroscopy measurements. It is shown that the experimental data and especially, new original data obtained with the pulsed admittance spectroscopy technique are consistent with a new model. The ‘‘new donors’’ effect would in fact be the result of the inversion layer around silica precipitates. This model is demonstrated taking in account the known properties of the Si/SiO2 interface (between precipitates and the silicon crystal). The electrical conduction is shown to be a percolation process through an inhomogeneously conducting material.
Analysis of superconducting-base transistor characteristics
Authors: Tamura Hirotaka , Fujimaki Norio , Hasuo Shinya
Published: July 2002

The characteristics of a superconducting-base transistor are derived. The device is similar to a bipolar transistor but uses quasiparticles in a superconductor as minority carriers. Injection, transport, recombination, and extraction of quasiparticles are discussed. Analytic expressions for the characteristics of the transistor are obtained.
Influence of grain size on the transformation temperature of C49 TiSi2 to C54 TiSi2
Authors: van Houtum H. J. W. , Raaijmakers I. J. M. M. , Menting T. J. M.
Published: July 2002

Titanium disilicide exists in two possible crystallographic structures: the C49 (ZrSi2) structure and the C54 structure. At low annealing temperatures (400–650 °C), the C49 TiSi2 phase is formed. It transforms to the C54 phase at annealing temperatures between 650–800 °C. The transformation temperature (Ttr), however, appears to be influenced by the microstructure of the C49 phase. This is concluded from the observed difference in Ttr for TiSi2 thin films with varying average grain sizes.
Production of the midgap electron trap (EL2) in molecular-beam-epitaxial GaAs by rapid thermal processing
Authors: Kitagawa Akio , Usami Akira , Wada Takao , Tokuda Yutaka , Kano Hiroyuki
Published: July 2002

Rapid thermal processing (RTP) using halogen lamps for molecular-beam-epitaxial (MBE) n-GaAs layers was investigated by deep-level transient spectroscopy. RTP was performed at 800 °C for 6 s with proximity capping method. It was found that the Ec −0.82 eV electron trap (EL2) was produced by RTP. The depth profile of EL2 was flat. The spatial variations of EL2 produced by RTP were observed across the MBE layers. The EL2 concentration increased by about two orders of magnitude toward the edge from the center of the samples (∼18×16 mm2). It was thought that the spatial distribution of EL2 corresponded to that of thermal stress induced by RTP.
Structural and magnetic properties of some Co(AlMn) alloys
Authors: Saleh A. S. , Mankikar R. M. , Booth J. G. , Kepa H. , Hicks T. J.
Published: July 2002

Magnetization, magnetic susceptibility, and neutron diffraction measurements have been made on the alloy series CoAl1−xMnx over a wide range of temperature for 0<x<0.4. In this range of concentration the alloys retain the singly ordered B2 (CsCl) structure and neutron diffraction results suggest that the Mn atoms predominantly enter Al sites. However, at concentrations less than x=0.15 about 1% of Mn atoms may possibly enter Co sites with consequent displacement of Co atoms to Al sites. All the alloys show ferromagnetic behavior with Curie temperatures up to 675 K. Evidence for the coexistence of superparamagnetism is found indicating some clusters may not be coupled to the infinite cluster. The superparamagnetism persists to a limited extent above the Curie temperatures for most of the alloys and conventional analysis suggests cluster moments of ∼1000μB for x=0.1 for example. At high temperatures Curie–Weiss behavior is consistent with a moment of ∼0.4μB per formula unit with a composition independent Curie constant suggesting an itinerant origin for the ferromagnetism. Low field (10 Oe or less) magnetization measurements have also been performed for x=0.1 and 0.2. There is a significant difference between zero-field cooled and field-cooled curves at low temperatures indicating a freezing at ∼80 K for x=0.1 and ∼15 K for x=0.2.
Magnetic properties of [100] oriented Cu-Ni superlattices
Authors: Xiao Gang , Chien C. L.
Published: July 2002

We have fabricated Cu-Ni superlattices with exclusive [100] modulating orientation by using a dc magnetron sputtering system. The layer thicknesses of both Cu and Ni range from 5 to 125 Å. The high quality of the samples is confirmed by the intense satellite peaks in the x-ray diffraction. The spontaneous magnetization at 5 K, which is found to be inversely proportional to the Ni layer thickness, vanishes at two Ni atomic planes. A very large difference in magnetic surface anisotropy has been found between [100] and [111] textured Cu-Ni superlattices, displaying the important role of modulating orientation on the magnetic properties of superlattice.
Influence of substrate texture on recording parameters for CoNiCr rigid disk media
Authors: Seagle D. J. , Fernelius Nils C. , Khan Mahbub R.
Published: July 2002

CoNiCr films, 2–3 μin. thick, have been prepared by dc magnetron sputtering on aluminum alloy based Ni-P substrates. This study is a comparison of recording and magnetic properties of two types of substrates: polished and circumferentially texturized. Measurements made include recording parameters (RMS signal, modulation noise, signal to noise, track average amplitude, overwrite, and bit shift), magnetic parameters from hysteresis loops as obtained by VSM, and film thickness by x-ray fluorescence. Surface profiles were obtained by a stylus profilometer. We report that the texturized disks have a 12% average improvement in signal to noise and approximately 1-ns improvement in bit shift compared to the polished-substrate disks. An anisotropy in the magnetic parameters was observed and related to substrate texture and asymmetry in the sputtering process. Typical differences in coercivity between radial and circumferential directons are on the order of 100 Oe for a 1000-Oe disk.
Magneto-optical properties of Fe-B-F films
Authors: Sugawara E. , Shirakawa K. , Masumoto T. , Suzuki K.
Published: July 2002

Films have been preprared by sputtering over a wide range of compositions in the Fe-B-F system. Fluorine was supplied by rf sputtering from an FeF3 target, and Fe-B by dc sputtering from arc-melted targets. Most of the samples were amorphous, although some contained a relatively small fraction of crystalline FeF2. The films were ferromagnetic, with Curie temperatures above room temperature and with room-temperature saturation magnetizations of 60 to 150 emu/g. Large Faraday coefficients, up to 105 deg/cm at 633 nm and fairly large Kerr rotations were observed.
High aspect ratio hole filling by tungsten chemical vapor deposition combined with a silicon sidewall and barrier metal for multilevel interconnection
Authors: Suguro K. , Nakasaki Y. , Shima S. , Yoshii T. , Moriya T. , Tango H.
Published: July 2002

A newly developed processing for high aspect ratio hole filling by tungsten chemical vapor deposition, combined with a Si sidewall technique and resist etch back is proposed. A high aspect ratio hole (around 3) was completely filled with W and W-Si alloy without voids. It is also proposed to interpose a TiN/TiSi2 layer between W and Si, in order to suppress rapid silicidation of W at high temperatures above 800 °C. Silicidation rates for W/TiN/TiSi2/Si systems were 2–2.5 orders of magnitude lower than W/Si systems. Electrical contact resistivity was kept to be lower than 1×10−5 Ω cm2 even after 900 °C annealing by suppressing rapid silicidation of W.
First-order field-induced magnetization transitions in single-crystal Nd2Fe14B
Authors: Bolzoni F. , Moze O. , Pareti L.
Published: July 2002

Magnetization measurements in high-pulsed magnetic fields have revealed the presence of magnetic anisotropy in the hard basal plane of a single crystal of Nd2Fe14B. A discontinuity in the magnetization occurs when the magnetic field is applied along the [100] direction in the hard basal plane below 220 K while there is a regular approach to saturation magnetization along the [110] direction. This discontinuity has been interpreted as a first-order magnetization process. High-order terms in the free energy are required to account for the spin reorientation transition from easy axis to easy cone and first-order magnetization process. The temperature dependence of the uniaxial and planar anisotropy energy constants has been determined.
Transmission electron microscopy of gold-silicon interactions on the backside of silicon wafers
Authors: Chang P.-H. , Berman G. , Shen C. C.
Published: July 2002

The Au-Si interactions on the backside of 〈111〉 silicon wafers have been studied over the temperature range of 275–400 °C by transmission electron microscopy. The Au films annealed at temperatures below the Au-Si eutectic temperature (363 °C) all have similar structure—columnar Au grains of small size (∼450 Å). An orthorhombic gold silicide, Au3Si, forms at the Au/Si interface below the eutectic temperature due to the migration of Au into the silicon substrate. The Au3Si grains are of much larger size (∼2000 Å) than Au and contain twins. Annealing at 400 °C, which is above the eutectic temperature, results in a completely different structure. It consists of numerous small Si islands protruded and dispersed throughout a continuous, large grain (>2.8 μm), polycrystalline gold film. Gold silicide was not observed at 400 °C. Many Au grains are found to grow epitaxially on the silicon substrate. The silicon islands are also found to grow epitaxially on silicon substrate. The structure after 400 °C annealing is interpreted as the result of the eutectic reaction between the substrate Si and the overlaying Au film.
Nitridation-enhanced conductivity behavior and current transport mechanism in thin thermally nitrided SiO2
Authors: Cheng X. R. , Cheng Y. C. , Liu B. Y.
Published: July 2002

Conduction enhancement characteristics and the conduction mechanism in nitroxide are reported in this paper. Thermally grown oxides with various thicknesses were nitrided in pure ammonia for different nitridation times. Conduction in thick oxide after short-time nitridation is dominated by Fowler–Nordheim tunneling with lowered barrier height. A trap-assisted tunneling model was used to explain the effect of the degree of nitridation on current enhancement in heavily nitrided films. A theoretical calculation was carried out to fit the theory to the experimental results, and the trap density and trap energy level were found to be in the ranges of 1.2×1019–7.2×1020 cm−3 and 2.46–2.56 eV, respectively. These results are explained satisfactorily by the Auger spectroscopic data.
Film-edge-induced dislocation generation in silicon substrates. III. High voltage transmission electron microscopy observations and theoretical results for (1̄11) and (011) silicon substrates
Authors: Vanhellemont J. , Claeys C.
Published: July 2002

The defect generation induced in the silicon substrate at nitride film edges during a local oxidation process is studied as a function of the film-edge orientation on (1̄11) and (011) wafers. The dislocations are characterized by high voltage transmission electron microscopy. A theoretical model which allows us to predict the defect types for arbitrarily oriented film edges and substrates is applied. Excellent agreement between experiment and theoretical calculations is obtained.
Magnetic properties of molecular-beam epitaxial grown (100) iron films
Authors: Lottis D. K. , Florczak J. , Dahlberg E. Dan , Batra S. , Wowchak A. M. , Cohen P. I.
Published: July 2002

The magnetic properties of epitaxial iron films have been studied. The iron films were grown on {100} GaAs and GaInAs substrates. Both the magnitude of the anisotropy energies and direction of the easy axes were studied using a SQUID magnetometer. In particular, measurements were made of the magnetization in the plane of the film along the 〈100〉 and 〈110〉 directions. From these measurements the magnitude of the anisotropy energy and the direction of the easy axis were determined. Also measurements of the coercivity of the films were made using a magneto-optic Kerr effect system. These results are compared with those determined previously for iron films grown on GaAs.
Ferromagnetic order at Tb surfaces above the bulk Curie temperature
Authors: Rau C. , Jin C. , Robert M.
Published: July 2002

The magnetic order at surfaces of the 4f rare-earth metal terbium is investigated using electron capture spectroscopy (ECS), which probes the electron spin polarization (ESP) of the topmost surface layer. In ECS, the capture of spin-polarized electrons during grazing-angle ion-surface interaction is used to determine the ESP due to long- and short-ranged surface magnetic order. It is found that long-ranged ferromagnetic order exists far above the bulk Curie temperature, measured to be TCb =220 K. At 140 K, the long-ranged ESP amounts to 24%. With increasing temperature, the ESP first decreases montonically up to the bulk Néel temperature TNb=228 K, then exhibits a pronounced maximum at T=238 K, and ultimately vanishes at the surface Curie temperature TCs =248 K. These striking results on enhanced magnetic order at Tb surfaces suggest the presence of very large surface anisotropies.
Magnetic properties of YCo12B6 and GdCo12B6 intermetallics
Authors: Rosenberg M. , Mittag M. , Buschow K. H. J.
Published: July 2002

The magnetic properties of polycrystalline intermetallics YCo12B6 and GdCo12B6 which crystallize in the hexagonal SrNi12B6 structure have been studied in dependence on temperature and magnetic field. YCo12B6 is ferromagnetic with Tc=151.5 K and an average Co moment of 0.44μB, whereas GdCo12B6 is a ferrimagnet with Tc=161 K and a compensation point at 47.8 K, with an average Co moment of 0.43μB.
A study of the H
c2 enhancement due to the addition of Ti to the matrix of bronze-processed Nb3Sn superconductors
Authors: Sekine H. , Itoh K. , Tachikawa K.
Published: July 2002

The measurements of ρn (the normal state resistivity), Tc, Hc2, and (dHc2/dt)T=Tc have been made for bronze-processed Nb3Sn wires with addition of Ti to the Cu-Sn matrix in order to study the mechanism of Hc2 enhancement due to the addition of Ti. The coefficient of electron specific heat, γ, has been derived by two independent methods: one using the Ginzburg–Landau–Abrikosov–Gor’kov (GLAG) theory and the measured values of ρn, Tc, and (dHc2/dT)T=Tc, and the other using the Kramer pinning theory and the gradient of J1/2cH1/4 -H curves. The ratios of γ/γ0 which have been derived by these two methods are in good agreement with each other. (γ0 is the value of γ for the specimen to which Ti is not added.) The upper critical fields given by the GLAG theory, H*c2 and Hc2, at 0 K increase rapidly with Ti concentration in the Nb3Sn layer up to 2 at. % and decrease slightly above 2 at. %. The rapid increase in ρnγTc caused by the addition of Ti is sufficient to explain the enhancement in Hc2, and among ρn, γ and Tc, only ρn shows a significant increase with increasing amounts of additional Ti, indicating that the main reason for the Hc2 enhancement is the increase in ρn.
On the effects of Auger recombination and energetic carrier leakage in GaInAsP/InP light emitting diodes
Authors: Chik K. D.
Published: July 2002

A model that unifies energetic carrier leakage with the Auger recombination theory has been applied to different designs of light emitting diodes (LEDs) to reconcile the discrepancies between results experimentally measured and theoretically predicted from Auger recombination theory alone. It is found that by applying this unified theory, theoretically calculated results are in excellent agreement with experimental measurements for a variety of LED designs in a wide range of injection currents.
Exciton photoluminescence linewidths in very narrow AlGaAs/GaAs and GaAs/InGaAs quantum wells
Authors: Bertolet Daniel C. , Hsu Jung-Kuei , Lau Kei May , Koteles Emil S. , Owens Douglas
Published: July 2002

A study of the low-temperature photoluminescence characteristics of very narrow one-dimensional quantum-well structures, grown by atmospheric pressure organometallic chemical vapor deposition, is presented. Theoretically predicted narrowing of photoluminescence peaks as quantum-well widths approach zero was experimentally observed in both AlGaAs/GaAs and strained GaAs/InGaAs samples. The role of such data in determining interface microstructure is discussed.
Redistribution of H and Be in GaAs/AlAs multilayer structures with post-implantation annealing
Authors: Zavada J. M. , Wilson R. G. , Comas J.
Published: July 2002

The redistribution of implanted atoms within GaAs/AlAs multilayer structures due to post-implantation furnace annealing is reported. The structures were grown using molecular-beam epitaxy on GaAs substrates and implanted with either hydrogen or beryllium ions. After furnace annealing at temperatures up to 700 °C, these samples were examined using secondary ion mass spectrometry. The measurements show that the hydrogen and the beryllium atoms redistribute with post-implantation annealing and that both species accumulate at the buffer layer-substrate interface. The concentration of atoms at this interface can exceed 1×1019 cm−3 and may be related to the crystal imperfections created during the inital stages of epitaxy. The significant redistribution of implanted ions may also alter the optoelectronics properties of multilayer semiconductor structures processed in this manner.
Physics of real-space transfer transistors
Authors: Kizilyalli I. C. , Hess K.
Published: July 2002

The physics of real-space transfer transistors has been studied by self-consistent particle Monte Carlo methods. Results of our simulations reproduce all experimentally known features of these devices. In particular, we study and explain the reasons of negative differential resistance, saturation of drain and substrate currents, the negative transconductance [gm=(ΔId,sat/ΔVsub)<0] effect, the importance of the subsidiary minima (L-X valleys) in GaAs and of interface barrier heights, and the switching characteristics of these devices.
Fe implantation in In0.53Ga0.47As/InP
Authors: Rao Mulpuri V. , Keshavarz-Nia N. R. , Simons David S. , Amirtharaj P. M. , Thompson Phillip E. , Chang Tao Y. , Kuo Jenn Ming
Published: July 2002

Single and multiple energy Fe+ implants are performed in n-type InGaAs. Rapid thermal and furnace annealings are used to activate the implanted material. Surface Fe accumulation, multiple Fe peaks, and deep in-diffusion of Fe are observed in the secondary ion mass spectrometry profiles of the implanted material. The crystal lattice perfection of the annealed material is evaluated qualitatively by photoreflectance measurements. A maximum resistivity of 4750 Ω cm is measured in the implanted material.
Kinetic and steady-state effects of illumination on defects in hydrogenated amorphous silicon
Authors: Bube Richard H. , Redfield David
Published: July 2002

Nine recombination-driven mechanisms are possible in principle for the kinetics and steady-state effects of illumination on defects in hydrogenated amorphous silicon. By comparing the different mechanisms, and making choices based on the experimental observation that the carrier lifetime varies inversely with the metastable defect (dangling bond) density, these nine are reduced to three. They correspond to recombination that generates metastable defects (1) taking place at metastable defects, (2) being associated with direct electron-hole recombination, or (3) taking place at other specific defect sites in the material. Each of these three models is considered under the assumptions that (a) the rate constants involved are not functions of time, and (b) the rate constants involved are functions of time in a way similar to that observed for the decay of thermally induced defects, described by a stretched exponential formulation. Comparison with experimental data on kinetics as a function of time and light intensity indicates that both models 2a and 1b are capable of describing the reported results. If, however, it is maintained that all defect-related kinetics in amorphous silicon should exhibit the dispersive behavior leading to the stretched exponential description, then only model 1b is acceptable. Experiments for distinguishing between models 2a and 1b are suggested.
Temperature distributions produced in an N-layer film structure by static or scanning laser or electron beam with application to magneto-optical media
Authors: Madison M. R. , McDaniel T. W.
Published: July 2002

The classic problem of heat flow in multilayer film structures has been revisited from the perspective of engineering applications for fields such as optical storage media design, laser annealing of semiconductor materials, electron beam lithography, and ion implantation. A compact recursive structure N-layer Green’s function is developed from the coupled partial differential equations of thermal conduction. Temperature profiles are calculated for the absorption of normally incident continuous and pulsed-Gaussian-beam irradiation, on both static and moving media, with variable absorption across the source layer. General beam, amplitude-time dependencies can be calculated with this formalism; however, only simple rectangular pulses are treated in the text. General N-layer solutions are developed, and compact, recursive-integral formulas, whose evaluation is enhanced with modern computer languages such as c and apl, are derived. In addition, we offer a clear physical interpretation of the results expressed by the mathematics, which is a key element that aids successful application of the results to engineering design problems. The physics illuminated by the mathematics suggests a path toward optimal design of the media for enhanced performance, irrespective of the specific application.
On the thermal dissociation of hydrogen
Authors: Jansen F. , Chen I. , Machonkin M. A.
Published: July 2002

The important role atomic hydrogen plays in the low-temperature and pressure deposition of diamond has renewed interest in the dissociation processes of hydrogen. Following a method originally developed by Langmuir and co-workers, the voltage-current characteristics of refractory filaments in vacuum and reduced-pressure gaseous environments are analyzed. Using hydrogen, deuterium, and helium, it is concluded that the difference in the power consumption by the filament in hydrogen and in vacuum is a good measure for the rate of hydrogen dissociation. This rate is shown by experiments and mathematical modeling to depend on the geometry of the refractory heater element. Relatively high dissociation rates, normalized per heater area, are obtained for small-diameter wires, and it is argued that this is indicative of a nonequilibrium dissociation process.
Zn-induced impurity levels in layer semiconductor InSe
Authors: Shigetomi S. , Ohkubo H. , Ikari T. , Nakashima H.
Published: July 2002

The impurity levels in Zn-doped InSe have been investigated by photoluminescence (PL), Hall effect (HE), and deep-level transient spectroscopy (DLTS). Previous analysis by PL spectra shows that the radiative transition is dominated by donor-Zn acceptor pairs. In the present work, a search was made for the deep acceptor level using the combined data from HE and DLTS measurements. We find that the deep acceptor level, which is associated with defects or defect complexes formed by Zn atoms in the interlayer, is located about 0.6 eV above the valence band.
A rotational vector Preisach model for unoriented media
Authors: Wiesen K. C. , Charap S. H. , Krafft C. S.
Published: July 2002

Heretofore, vector Preisach models have consisted of angularly distributed scalar models. We postulate adding rotational capability to the binary response of the Preisach elements to obtain vector behavior using a single density function. A rotating field H divides the Preisach density function, which is obtained from scalar measurements, into regions associated with magnetization directions dependent on the applied field history. The magnetizations of elements with h*<‖H‖, where h* is the larger of the switching field magnitudes, follow exactly the direction of the rotating field. Those with h*>α‖H‖ (1<α<2 and is experimentally determined) are not oriented by H, but may be switched by the parallel component of H. Elements with intermediate values of h* rotate irreversibly at an angle which lags the field. The model has the same scalar properties in all directions and has performed well in simulating measurements made on a barium ferrite floppy disk with a vector vibrating sample magnetometer.
Magnetic phase diagrams of UCu2Si2 and UNi2Si2
Authors: McElfresh M. W. , Rebelsky L. , Torikachvili M. S. , Borges H. , Reilly K. , Horn S. , Maple M. B.
Published: July 2002

Magnetization measurements performed on UCu2Si2 and UNi2Si2 are reported. The compound UCu2Si2 appears to undergo both an antiferromagnetic (AFM) transition at T≊107 K and a ferromagnetic (FM) transition at Tc≊103 K. While the second transition at Tc has already been reported, the AFM phase was apparently overlooked in earlier studies. The compound UNi2Si2 undergoes a transition at T≊97 K, which was previously shown to be AFM by neutron scattering; we present evidence for the occurrence of a FM state below the AFM transition.
Epitaxial growth and magnetic properties of Fe16N2 films with high saturation magnetic flux density (invited)
Authors: Komuro Matahiro , Kozono Yuzoo , Hanazono Masanobu , Sugita Yutaka
Published: July 2002

Fe-N films with thicknesses of 70–1000 Å were deposited by MBE onto Fe films which were epitaxially grown onto GaAs(100) substrates. Without the Fe layer, epitaxially grown Fe-N films could not be obtained due to a reaction between Fe-N and GaAs. TEM observations and x-ray diffraction patterns showed that the epitaxially grown Fe-N films consist of Fe16N2 and Fe, and that crystal orientation is Fe16N2 (001)//Fe(110). It was found that the saturation magnetic flux density (Bs) increases as the thickness of the Fe-N films decreases. This is because the volume ratio of Fe16N2 in the Fe-N films increases with decreasing Fe-N film thickness. The maximum value for Bs is 2.66 T, and the volume ratio is 85%. These results indicate that Fe16N2 has a high saturation magnetic flux density of 2.8–3.0 T.
Examination of eddy current influence on the behavior of a giant magnetostrictive functional unit
Authors: Kvarnsjö L. , Engdahl G.
Published: July 2002

Current simulation models for the magnetoelastic behavior of giant magnetostrictive materials have been successfully used in designing low-frequency functional units based on magnetostrictive effects. At higher frequencies, however, the precision of these models decreases due to eddy currents inside the material. In a specially designed setup, a functional unit was electrically feeded with sinusoidal currents of different amplitudes and frequencies and mechanically loaded with different mechanical forces. The experimental data obtained were used in an extended simulation model able to include eddy current effects into the magnetomechanical process. The extended model has been verified experimentally for sinusoidal magnetizations at different frequencies and mechanical loads. A comparison between this experimentally extended model and a corresponding analytically extended model is also done. The comparison gives an indication of the interaction between mechanical stresses and magnetic field penetration inside the magnetostrictive material.
Study of the growth characteristics of sputtered Cr thin films
Authors: Duan S. L. , Artman J. O. , Wong B. , Laughlin D. E.
Published: July 2002

The crystallographic texture of Cr film deposited on glass substrates is found to depend on the film thickness dCr and the substrate temperature Ts. Without substrate preheating, only the Cr {110} peak was observed in the x-ray diffraction spectra for films between 60 and 400 nm in thickness. With increasing Ts (by substrate preheating), the Cr{200} peak became observable at progressively increasing intensity, whereas the intensity of the {110} peak decreased. Consequently the 170-nm-thick films deposited at Ts ≥200 °C are predominantly {100} textured. However, even for these high Ts values (≥200 °C), the {110} peak intensity increases with increasing film thickness. Larger film thickness values are required at higher Ts for the {110} texture to overcome the {100} texture. The grain size of the Cr films deposited on glass increases with film thickness and with substrate temperature.
Characterization of the EL2 center in GaAs by optical admittance spectroscopy
Authors: Dueñas S. , Castán E. , de Dios A. , Bailón L. , Barbolla J. , Pérez A.
Published: July 2002

We have measured the electron optical capture cross section, σ0n(hν), of EL2 (the most important native center in GaAs) using a new technique which we have recently developed: optical admittance spectroscopy. This is a spectroscopic technique based on the measurement of the capacitance and conductance of a junction under monochromatic light of energy hν. This technique allows the measurement of the spectrum σ0n(hν) of each center located in the band gap. We have measured the electron photoionization cross section of the EL2 center, σ0n(hν), at three different temperatures within a range limited at high temperature by thermal emission and at low temperature by photoquenching (a feature characteristic of EL2 below 140 K). The study of the experimental data reveals that this center has a more complex nature than that of a simple defect. It seems to behave like a family of very close levels corresponding to similar atomic structures and located near the midgap. These results also reveal the existence of a shallow level close to the valence band and associated with EL2.
Minority electron transport property in p-GaAs under high electric field
Authors: Furuta T. , Taniyama H. , Tomizawa M.
Published: July 2002

Time-of-flight and photoluminescence measurements are performed for p-GaAs samples at room temperature to investigate minority electron transport properties under high electric field. Reduction of drift velocity, absence of negative differential resistance, and thermally nonequilibrium states between electrons and holes were observed. These features were different from those for majority electrons and indicate strong dependence on hole concentration. Through studies of the energy loss rate and energy and momentum relaxation times, and by performing Monte Carlo calculations including electron-hole interaction, it is clarified that the energy and momentum transfers by electron-hole interaction have significant effects on minority electron transport property.
Pt/Ti Ohmic contact to p++-InGaAsP (1.3 μm) formed by rapid thermal processing
Authors: Katz A. , Thomas P. M. , Chu S. N. G. , Dautremont-Smith W. C. , Sobers R. G. , Napholtz S. G.
Published: July 2002

Nonalloyed Ohmic contacts of evaporated Pt/Ti to p-InGaAsP (λg=1.3 μm) with different Zn doping levels ranging 5×1018–2×1019 cm−3 have been fabricated by rapid thermal processing. These contacts showed Ohmic behavior prior to any heat treatment with a specific contact resistance of 4×10−3 Ω cm2 for the lowest doping level and 1×10−4 Ω cm2 for the highest level. A decrease in the specific resistance was achieved by supplying rapid thermal processing to the contacts, while the lowest values were observed on all the contacts as a result of heating at 450 °C for 30 sec. The lowest resistance of 1×10−6 Ω cm2 was achieved at the contact that was formed on the 2×1019 cm−3 Zn-doped InGaAsP layer. Measurements of the conduction activation energy yields a good linear dependence of the specific resistance on temperature in all the contacts as deposited and after the different heat treatments. The higher the doping level and the rapid thermal processing temperature up to 450 °C, the lower the activation energy, which may suggest an increase in the tunneling carrier transport mechanism contribution at the expense of the thermionic-emission one. The morphology and microstructure of these contacts were not influenced by the variations in the Zn doping concentration.
Analysis of finite-element matrices arising from discretizations of helicity functionals
Authors: Kotiuga P. R.
Published: July 2002

This paper examines the discretized helicity functional in order to demonstrate the invariance under discrete gauge transformations and to obtain a direct physical interpretation of the finite element equations. A simple analysis then yields a rigorous comparison between the amount of work required to implement a semidirect (e.g., conjugate gradient) equation solver for unpreconditioned stiffness matrix equations associated with the helicity functional and conventional functionals.
Fabrication and magnetic properties of granular alloys
Authors: Gavrin A. , Chien C. L.
Published: July 2002

Granular alloys of iron with other transition metals have been fabricated in both Al2O3 and SiO2 matrices. Both stable (Fe-Ni, Fe-Co) and metastable (Fe-Cu) alloys have been achieved. Under appropriate deposition conditions, the grains are single-phase alloys ranging in size from 15 to 50 Å. Superparamagnetism and enhanced coercivity have been observed, and the effect of grain size on these phenomena has been investigated. We have also studied the effects of the different insulating matrices.
Thermomagnetic analysis of compositional separation in sputtered Co-Cr films
Authors: Maeda Yasushi , Takahashi Masaya
Published: July 2002

The change in compositional distribution of sputtered Co-21 at. % Cr films is investigated as a function of substrate temperature using thermomagnetic analysis. As the substrate temperature increases from 50 to 400 °C, the compositional inhomogeneity progresses causing compositional separation through two stages: in stage I (substrate temperature = 50–200 °C), there occurs a drastic compositional separation into a ferromagnetic Co-rich component (10–13 at. % Cr, 45–50 vol %) and a paramagnetic Cr-rich component (30–40 at. % Cr, 30–40 vol %) in a hcp structure; in stage II (substrate temperature =300–400 °C), σ phase precipitation seems to proceed competing with homogenization while the compositionally separated state still exists. At both stages, components with a total volume fraction of 10%–25% and compositions close to that of the film average are observed to remain. The compositional separation is recognized in compositional microstructures revealed by selective chemical etching. A two-phase separation due to the effect of magnetic transition is discussed as a possible origin of this compositional separation.
Optical and magneto-optical tensor spectra of bismuth-substituted yttrium-iron-garnet films
Authors: Doormann Volker , Krumme Jens-Peter , Lenz Horst
Published: July 2002

We report on the complete dielectric tensor spectra of Y3−xBixFe5O12 with 0≤x≤1.42 in the photon energy range 1≤ℏω(eV)≤4.8, i.e., 1240–248 nm wavelength. In an attempt to identify the involved optical transitions we have (i) parametrized these spectra in terms of Gaussian (ε″11 spectra) and diamagnetic or paramagnetic (ε′12 and ε″12 spectra) line shapes, and (ii) come up with a set of coefficients of a cubic interpolation polynomial for each spectral ‘‘line’’ from which any of the n, α, ΘF, εF, ΘK, εK, ε′11, ε″11, ε′12, ε″12 spectra can be calculated for any bismuth substitution in the above compositional and spectral range. It is found that such a line-shape analysis is not unique and requires physical knowledge on the optical excitations involved which, however, is still incomplete for iron garnets.
Two-band modeling of narrow band gap and interband tunneling devices
Authors: Söderström J. R. , Yu E. T. , Jackson M. K. , Rajakarunanayake Y. , McGill T. C.
Published: July 2002

A two-band transfer matrix method has been developed to study tunneling currents in narrow gap and interband tunnel structures. This relatively simple model gives good agreement with recently reported experimental results for InAs/AlSb/InAs/AlSb/InAs double-barrier heterostructures and InAs/AlSb/GaSb/AlSb/InAs resonant interband tunneling devices, and should be useful in the design of new interband tunneling devices.
The effect of air shear on the flow of a thin liquid film over a rough rotating disk
Authors: Ma F. , Hwang J. H.
Published: July 2002

The depletion of thin liquid films due to the combined effect of centrifugation, surface roughness, and air shear is addressed. As a liquid film flows on a horizontal rotating solid surface, it is thinned by both inertial forces as well as by shearing forces at the liquid-air interface. The equations describing the flow of a thin viscous film over a rough rotating disk are solved by numerical techniques. Depletion histories of the thin film are given for several cases involving both deterministic and random surface asperities. It is noted that surface roughness of a rotating disk markedly enhances the retention of the thin liquid film. The thinner the liquid layer, the more significant is the effect of surface roughness. On the other hand, shearing forces between the free liquid surface and ambient air increase the depletion of the liquid film at a rate that is dependent on the speed of rotation. In general, inertial forces play a secondary role in the depletion of very thin films; the asymptotic limits of liquid retention are strongly influenced by the topographic structures of the surface roughness and the air shear.
Characterization and growth mechanisms of boron nitride films synthesized by ion-beam-assisted deposition
Authors: Burat O. , Bouchier D. , Stambouli V. , Gautherin G.
Published: July 2002

We have studied boron nitride films deposited at room temperature by ion-beam-assisted deposition in an ultrahigh vacuum apparatus, with ion accelerating voltages ranging between 0.25 and 2 kV. By using complementarily in situ Auger electron spectrometry and ex situ nuclear analyses to determine the respective surface and bulk N concentrations in the deposited films, we were able to identify the different phases of the mechanism leading to the nitridation of evaporated boron by nitrogen ions. For low nitrogen/boron flux ratios, the incorporation of nitrogen seems to be only governed by ion implantation, and, with respect to the depth of the deposit, the surface is found largely depleted in nitrogen, while the N-incorporation yield remains close to one whatever the ion energy. Such a behavior is well verified as long as a critical bulk nitrogen concentration close to 5.5×1022 cm−3 has not been achieved. For concentrations greater than this, superstoichiometric material is obtained up to a saturation which corresponds to a bulk N incorporation ranging from 6 to 7×1022 cm−3. Further increase of the N/B flux ratio induces a strong diffusion process from N-rich bulk to N-depleted surface, which results in the nitridation of surface boron atoms and a loss of nitrogen by sputtering or desorption. The density measurements seem to indicate that the synthesized phase is close to h-BN. However, the density of B-rich layers ([N]/[B]≊0.2–0.3) is found to be very close to that calculated for a mixture of pure boron and c-BN. The transparency and microhardness of the synthesized BN have satisfying values for its application as a wear-resistant optical coating, but it is not c-BN.
Control of gold concentration profiles in silicon by ion implantation
Authors: Coffa S. , Calcagno L. , Campisano S. U. , Ferla G.
Published: July 2002

Diffusion of ion-implanted gold in a silicon single crystal has been studied by the spreading resistance technique. In this work we investigate both unidimensional and bidimensional diffusion across the wafer and along the wafer surface, respectively, by using limited or unlimited gold sources. We will show that by using ion implantation of gold it is possible to produce unique concentration profiles through the fine control of the amount of gold atoms in the diffusion source; both depth and surface profiles can be tailored. All the measured profiles are in good agreement with the theoretical prediction of the kick-out mechanism for gold diffusion in silicon.
Quantitative assessment of Be acceptors in GaAs by local vibrational mode spectroscopy
Authors: Wagner J. , Maier M. , Murray R. , Newman R. C. , Beall R. B. , Harris J. J.
Published: July 2002

Be-doped epitaxial layers of GaAs grown by molecular beam epitaxy have been studied by local vibrational mode spectroscopy combining infrared absorption and Raman scattering. Calibration factors for both experimental techniques have been derived which enable quantitative assessments to be made of the concentrations of Be acceptors in GaAs. In Raman spectroscopy the detection limit is ≊ 3×1018 cm−3 for as-grown layers only 10 nm in thickness.
Magnetocrystalline anisotropy and magnetostriction of FeRuGaSi single crystals: SOFMAX
Authors: Okamoto T. , Hayashi K. , Hayakawa M. , Aso K.
Published: July 2002

The magnetocrystalline anisotropy constant, K1 and the magnetostriction constants, λ100 and λ111 for recently found soft magnetic FeGaSi and FeRuGaSi alloys were determined in the composition region, 0–8 at. % Ru, 5–15 at. % Ga, 10–22 at. % Si, and bal. Fe. The Ru 4–8 at. %-added FeRuGaSi alloys have the intersectional points, where λ100, λ111, and K1 simultaneously become zero, at the compositions around Fe67Ru4Ga11Si18 and Fe65Ru8Ga8Si19 (at. %), whereas in the FeGaSi alloy the K1=0 line and the two zero magnetostrictive lines are apart from one another.
Fe[S2CNC4H8]2I: A quasi-two-dimensional XY antiferromagnet
Authors: Harlan E. W. , Chamberlain R. V. , DeFotis G. C.
Published: July 2002

The magnetic properties of Fe[S2CNC4H8]2I have been studied, the first pentacoordinate Fe(III) system of this type with a cyclic terminal group, rather than an alkyl group, to be examined in detail. The susceptibility of a polycrystalline sample is of Curie–Weiss form above 30 K, with ḡ=2.16 ±0.02 and S=3/2 and with θ=−0.75±1.0 K. Thus the unusual intermediate spin state occurs here as in earlier examples. The susceptibility can be fit quite well down to about 6 K assuming that axial and rhombic crystal field distortions occur, represented by D[Ŝ2z − S(S + 1)/3] and E[Ŝ2x − Ŝ2y] terms in the spin Hamiltonian, and incorporating exchange interactions in a mean-field approximation. Fitted parameters are D/k=9.3± 0.5 K, E/k=−0.6±0.2 K, gx=2.23± 0.05, gy= 2.19 ± 0.05, gz=2.04 ± 0.05, and zJ/k=−0.235 ±0.02 K. At low temperatures the susceptibility exhibits a broad maximum with T(χmax)=3.23± 0.04 K and χmax =0.376±0.004 emu/mol. An antiferromagnetic transition at Tc=2.21±0.01 K is inferred from the position of a maximum in (∂χ/∂T), an ordering temperature in reasonable agreement with earlier Mössbauer results. The ratio Tc/T(χmax) =0.68±0.01 is suggestive of quasi-two-dimensionality. In the region of the maximum an acceptable fit according to a 2D- XY model with plausible parameter values can be achieved, but only with a ferromagnetic interlayer exchange interaction about 28% as strong as the leading antiferromagnetic intralayer interaction. Isotherms of M vs H show somewhat unusual curvature, the explanation of which is unclear.
Investigation of the helimagnetic phases of holmium in a c-axis magnetic field
Authors: Tindall D. A. , Steinitz M. O. , Kahrizi M. , Noakes D. R. , Ali N.
Published: July 2002

Neutron diffraction measurements have been made in the (h0l) plane of holmium in a c-axis magnetic field of 3 T. Thermal expansivity measurements have also been made by capacitance dilatometry. The main focus of our investigation has been a region about 2 K wide near 96 K, where the helimagnetic structure locks into a commensurate state. We have also been able to observe the ‘‘2-τ’’ satellites (at twice the fundamental magnetic ordering q vector) at temperatures as high as 3 K below the Néel transition. In the region between the lock-in transition and the Néel point, the intensities of these satellites show interesting behavior with temperature and may be showing effects due to the anomalies which have been identified in our magnetization measurements.
Nitrogen-doped iron-film-based laminated materials for thin-film recording heads
Authors: Wang S. , Kryder M. H.
Published: July 2002

We have systematically studied nitrogen-doped iron (FeN) multilayer films aiming to achieve very small coercivity and near-zero magnetostriction simultaneously by varying the multilayer structure and sputtering parameters used to deposit the FeN layers. Multilayers using SiO2, NiFe, and CoZrRe have been studied. Films with a saturation magnetization of above 20 kG, a coercivity of 0.4 Oe, a magnetostriction constant of less than 5 × 10−7, and a hard-axis dc permeability of 4000 have been obtained.
Domain structures and dynamics near the backgap closure of thin-film heads
Authors: Liu F. H. , Schultz M. D. , Kryder M. H.
Published: July 2002

Statically unstable spikelike reversed magnetic domains emanating from the backgap closure of thin-film heads have been observed with high-frequency (1–20 MHz) and high-current amplitude (20–80 mA p-p) drive fields by using a wide-field magneto-optic domain observation system with a 10-nsec exposure time. The spikelike domains are repeatedly nucleated and annihilated within the drive cycle and do not remain after removal of the excitation. The formation of spikelike domains is due to the magnetization rotation back to the nearest easy directions after fanning out near the backgap closure to carry the spreading flux out of (or converging flux into) the backgap closure. The spikelike domains block the flux flow into and out of the backgap closure at excitation frequencies above 10 MHz due to the slow domain annihilation process. It is speculated that occasional failure of these spikelike domains to annihilate after a write pulse could lead to noise when they suddenly collapse during read out.