bluuebunny/crossref_metadata_2025 huggingface dataset:
Soft magnetism of high-nitrogen-concentration FeTaN films
Authors: Ishiwata Nobuyuki , Wakabayashi Chizuko , Urai Haruo
Published: July 2002

High-nitrogen-concentration FeTaN films have been newly developed as a high performance magnetic head core material. 10.5–14.5 (at. %) N, 8–13 Ta, and balance Fe composition films, prepared by a nitrogen reactive sputtering method followed by appropriate annealing (500–550 °C), have high saturation flux density (14–17 kG) and excellent soft magnetic properties: such as low coercivity (∼0.1 Oe), high relative permeability (3000 at 20 MHz), and small saturation magnetostriction ( < 0.5 × 10−6). Fine crystal structure is one of the most essential origins for the soft magnetism of FeTaN films. The FeTaN films are expected to realize recording density increases and rubbing noise reduction with high durability and high reliability due to their high Vickers hardness (1000) and their higher corrosion resistance than Sendust film.
Magnetic phase transitions in UNi2Si2
Authors: Rebelsky L. , Lin H. , Collins M. F. , Garrett J. B. , Buyers W. J. L. , McElfresh M. W. , Torikachvili M. S.
Published: July 2002

We report neutron diffraction measurements on a single crystal of UNi2 Si2. Three magnetically ordering phases are observed below 123 K with the magnetic moment parallel to the c-axis in all three phases. The low temperature (T<53 K) phase is a superposition of a commensurate spin density wave with wave vector q = (0 0 0.667±0.002) and a ferromagnetic ordered moment of 1.1±0.3μB, the intermediate (53 K<T<103 K) is a simple body-centered tetragonal antiferromagnet with an ordered magnetic moment of 1.8±0.2μB and the high-temperature phase is an incommensurate spin density wave with wave vector q = (0 0  0.744±0.002) at 110 K. The phase transitions at 53 and 103 K are first order.
Recording properties of Co-Ni obliquely evaporated tape
Authors: Naruse Hiroji , Tateno Yasuo , Sato Takanori , Sato Kenichi , Chiba Kazunobu , Sasaki Toshikazu
Published: July 2002

This paper describes the recording properties of Co-Ni obliquely evaporated tape (ME tape) when a ring head is used. Since an isolated playback pulse identifies the magnetization transition region, we investigated the variation of phase characteristics of isolated pulses with tape-transport direction and with the magnetic motive force (MMF) of the recording head. Fast Fourier transformation is used to make a quantitative analysis of the phase distortion. It was found that the phase distortion of ME tape depends on the tape-transport direction during recording, but not during playback. The degree of inclination of the magnetization vector was estimated from the phase distortion in the low-frequency region. When recording was performed in the normal direction, the inclination of the magnetization vector was estimated to be 20°, and 25° in the reverse direction. In normal-direction recording, the phase distortion of the isolated pulse was independent of MMF and remained constant. That is to say, the magnetization vector in the normal direction is very stable. An analysis of recording properties which assumed the magnetization of uniaxial anisotropy particulates suggested that the magnetization vector should be oriented near the easy-axis direction.
Influence of the magnetic interactions on the reversal mode of magnetic recording particles
Authors: Bottoni G.
Published: July 2002

In an assembly of particles, as used in magnetic recording media, there are always magnetic interactions. The magnetic properties of the media are modified as a consequence of the effect of such interactions on the magnetic behavior of the particles. In this work an attempt is made to find an experimental correlation between the presence and strength of the interactions and the magnetization reversal of the particles. The reversal mode is investigated by rotational hysteresis measurements and by the evolution of the angular dependence of the coercivity in samples of iron oxides at different dilution degrees. The magnetic interactions are evaluated with measurements of the remanence curves. It is found that when the magnetic interactions among the particles increase, the parameters used to study the reversal mode evolve from the behavior typical of the incoherent magnetization processes to behaviors which can be considered as intermediate between coherent and incoherent reversal modes. This evolution can be attributed to the tendency of the magnetic interactions to increase the percentage of particles in the aggregate, which reverse with coherent rotation, particularly in the agglomerates often present in closely packed assemblies.
The Meyer–Neldel rule in hydrogenated amorphous silicon n
i
n devices
Authors: Oversluizen G. , van Kessel R. P. , Nieuwesteeg K. J. , Boogaard J.
Published: July 2002

Conductivity measurements on hydrogenated amorphous silicon (a-Si:H) nin devices with several i-layer thicknesses are reported. The ohmic conductivity (σ) is found to follow the Meyer–Neldel rule (MNR): σ=σ00  exp(Ea/kT0) exp(−Ea/kT), where Ea is the conductivity activation energy, k is Boltzmann’s constant, and T is the temperature. It is shown that the MNR arises because of the form of the a-Si:H gap state distribution that induces a statistical shift of the Fermi energy with the required functional form and magnitude. The characteristic temperature T0 is related to the slope G=1/kTc of the exponential conduction-band tail state distribution according to kT0≂1.7kTc. The conductivity prefactor can be expressed as σ00=CNceμ, where Nc is the density of states (DOS) above the mobility edge, e is the electron charge, μ is the microscopic electronic mobility, and C is a constant of the order of 10−6 eV. Evaluation of the data gives σ00=10−2.9 (Ω cm)−1, and T0=570 K, i. e., Tc=340 K. This σ00 value corresponds to realistic values of Nc≂1021 cm−3 eV−1 and μ≂10 cm2/V s. DOS data are also deduced from the space-charge-limited conduction (SCLC) of the nin’s at higher voltages. In this way a consistent DOS distribution for the upper half of the a-Si:H band gap is obtained. SCLC analysis indicates a minimum gap state density N0=4×1016 cm−3 eV−1. UFAIPXR
Particle generation and behavior in a silane-argon low-pressure discharge under continuous or pulsed radio-frequency excitation
Authors: Bouchoule A. , Plain A. , Boufendi L. , Blondeau J. Ph. , Laure C.
Published: July 2002

The generation and behavior of particles in a low-pressure silane-argon discharge have been analyzed under continuous and pulsed radio-frequency (rf) excitation conditions. In the continuous rf excitation regime, the influence of parameters such as gas temperature and silane partial pressure are determined. By using rf pulsed excitation, it is shown that gas-flow effects play a predominant role for particle dynamics when the excitation is stopped. Radio-frequency regimes with short and adjustable rf off sequences are used to study both the inhibition of particle formation and the elimination of particles from the dusty plasmas. The electrical properties of the discharge are shown to be sensitive to the presence of the particles. Simple models for particle trapping in the plasma edge and for particle dynamics when the discharge is turned off are presented.
High resolution electron beam lithography with a polydiacetylene negative resist at 50 kV
Authors: Dobisz E. A. , Marrian C. R. K. , Colton R. J.
Published: July 2002

A polydiacetylene with urethane substituents is shown to have high resolution, when used as a negative electron beam resist. The resist has a wide process latitude and can be developed in chloroform. The minimum feature size, distinguishable point-to-point spacing, linewidth, and line spacing are addressed through exposure test patterns of single pass line and pixel arrays. For a Gaussian probe with a 1/e radius of 8.3 nm, minimum feature sizes of 80 nm and minimum array period of 200 nm can be achieved in the resist. The resist exhibits line and isolated pixel sensitivities of ≊4.2 nC/cm and 3.4 fC, respectively, at 50 kV, which are comparable to those of polymethylmethacrylate. The results are analyzed through electron scattering calculations and exposure chemistry.
Galvanomagnetic behavior of semiconducting FeSi2 films
Authors: Valassiades O. , Dimitriadis C. A. , Werner J. H.
Published: July 2002

Hall-effect measurements in magnetic fields up to 1.5 T are performed on β-FeSi2 films between 20 and 300 K. An anomalous low-field Hall coefficient R1 in addition to the normal high-field Hall coefficient R0 is detected at temperatures below 250 K. The temperature dependence of R0 is explained by a two valence-band model and an impurity level located close to the upper valence-band edge. The temperature dependence of R1 indicates that β-FeSi2 behaves as ferromagnetic below 100 K. Correlation between the coefficient Rs=R1−R0 and the electrical resistivity ρ indicates a drastic change in magnetic ordering at about 70 K.
Interaction of Cs with the GaAs(100) surface
Authors: Kamaratos M. , Bauer E.
Published: July 2002

The Cs/GaAs(100) system is studied by Auger electron spectroscopy, electron energy-loss spectroscopy, work function change measurements, low-energy electron diffraction, and thermal desorption spectroscopy at 200 K and at room temperature. At room temperature the Cs layer is nonmetallic; at low temperature there is clear evidence for metallization after completion of the first monolayer.
Magnetic properties of Cr overlayers on Fe (invited)
Authors: Jungblut R. , Roth Ch. , Hillebrecht F. U. , Kisker E.
Published: July 2002

The magnetic properties of Cr overlayers deposited on Fe(100) were investigated by spin-resolved photoemission. Valence band spectra show a reduction of the overall polarization after deposition of Cr. Data of the Cr 3p core level show for Cr coverages up to about 2 monolayers a polarization opposite to that of the Fe 3p core level. Both findings are evidence for an orientation of the Cr moments antiparallel to the Fe moments. The core level as well as the valence band results are consistent with an average moment of about 1 μB per Cr atom, which is significantly smaller than calculated for a monolayer of Cr on Fe.
Ion transport in an electron cyclotron resonance plasma
Authors: Sadeghi Nader , Nakano Toshiki , Trevor Dennis J. , Gottscho Richard A.
Published: July 2002

Electron cyclotron resonance (ECR) plasma reactors are being developed for etching and deposition of thin films during integrated circuit fabrication. To control critical parameters such as the flux and energy distribution of ions impacting surfaces, it is necessary to understand how these parameters are influenced by physical construction, electromagnetic design, and chemical kinetics. In this work, we report detailed measurements of ion velocity distributions in both the source and reactor regions of an ECR system using mixtures of Ar and He. Using Doppler-shifted laser-induced fluorescence spectroscopy, we measure metastable Ar-ion velocity distributions parallel and perpendicular to the magnetic field direction as a function of magnetic field amplitude, pressure, rf bias voltage, and microwave power. The measurements, in turn, are used to estimate the magnitude of electrostatic potentials and fields parallel and perpendicular to the magnetic field. Indicative of ion trapping, we find nearly isotropic ion velocity distributions when the source is operated as a magnetic mirror and the He partial pressure is low; higher He pressures tend to cool the parallel velocity distribution. Downstream, we consistently observe bimodal ion velocity distributions: the fast component, created in the source, follows magnetic flux lines into the reactor; the slow component, created mostly where the plasma expands from the source into the reaction chamber, is more isotropic. The relative amplitudes of these two components, the average ion energy, and the ion energy distribution are easily controlled by changing pressure and magnetic field.
Liquid-phase epitaxial growth of GaInAsSb with application to GaInAsSb/GaSb heterostructure diodes
Authors: Wu Meng-Chyi , Chen Chi-Ching
Published: July 2002

High quality Ga0.82In0.18As0.17Sb0.83 layers lattice matched to GaSb substrates were grown by liquid-phase epitaxy using a supercooling technique. By selection of the optimum growth condition, we can obtain the undoped layer with a low hole concentration of 1.2×1016 cm−3 and a narrow full width at half maximum of 12 K photoluminescence spectrum of 11.6 meV. The temperature dependence of near band gap energy in Ga0.82In0.18As0.17Sb0.83 layers, determined from the photoluminescence peak energy, varies as 0.62–[5.2×10−4T2/(T+163)] eV. In order to obtain the low electron concentration layer, the Te-doped polycrystalline GaSb (n=4×1017 cm−3) is used to replace some of the undoped GaSb starting material in the growth solution for the purpose of compensation. The lowest hole concentration of 4–7×1015 cm−3 can be achieved when the GaSb starting material in the growth solution consists of 10% Te-doped polycrystalline. With increasing percentage, the layer conduction changes to n type, and it reaches an electron concentration of 2×1017 cm−3 by using only the Te-doped GaSb polycrystalline in the growth solution. On the other hand, the peak wavelength of 12 K photoluminescence spectrum decreases with increasing electron concentration because of the Burstein–Moss effect. Finally, an n-GaInAsSb/p-GaSb heterostructure diode was fabricated, which exhibits a forward-bias turn-on voltage of 1.8 V and an ideality factor of 1.86.
Preferred orientation in Cr- and Co-based thin films and its effects on the read/write performance of the media
Authors: Tsai Hsiao-chu , Lal Brij B. , Eltoukhy Atef
Published: July 2002

This work investigates the formation of preferred crystallographic orientation (PO) in Cr underlayer as well as CoCrTa and CoCrPtTa thin films and its effects on the recording performance of longitudinal media. The results show that the thin-film media with comparable coercivity but different crystalline PO as measured by x-ray diffraction exhibit significant difference in high-frequency signal amplitude, pulse width, and signal-to-noise ratio. To illustrate the effect of PO on parametric performance, CoCrTa/Cr and CoCrPtTa/Cr media were sputtered on different substrates and/or using special sputtering processes to achieve comparable coercivity but different PO in the films. A PO of Cr(200), which normally occurs on the NiP/Al substrates under adequate sputtering conditions, is found to be the key to obtaining a PO of Co(11.0) in Co-alloy media. The consequence of preferred in-plane c-axis orientation is a higher coercivity and better parametric performance of the medium. The formation of PO in the Cr underlayer is found to be related to the substrate material and the oxygen content in the sputtered films. The nonmetallic canasite substrates tend to promote PO of more stable Cr(110) rather than Cr(200). Consequently, this leads to a PO of out-of-plane c axis on the following Co films. The PO of magnetic layer appears to be an important factor in determining the parametric performance of the media.
Magnetic levitation and stiffness in melt-textured Y-Ba-Cu-O
Authors: Hull J. R. , Mulcahy T. M. , Salama K. , Selvamanickam V. , Weinberger B. R. , Lynds L.
Published: July 2002

Magnetic levitation and stiffness have been measured in several systems composed of a permanent magnet elastically suspended above a stationary melt-textured sample of Y-Ba-Cu-O. The levitation force and vertical stiffness have been calculated on the basis of magnetization measurements of the same system, and the calculated results showed excellent agreement with the experimental measurements. Based on the force and magnetization measurements, it is predicted that the same Y-Ba-Cu-O material configured in a geometry suitable for magnetic bearings could produce a levitation pressure of 100–400 kPa at 20 K.
Autler–Townes effect of the photoexcited diamond nitrogen-vacancy center in its triplet ground state
Authors: He Xing-Fei , Fisk Peter T. H. , Manson Neil B.
Published: July 2002

The Autler–Townes effect in nuclear magnetic resonance (NMR) and electron paramagnetic resonance has been observed using recently developed Raman heterodyne techniques. The measurements were carried out on the nitrogen-vacancy color center in diamond, where the 3A↔3E optical transition was driven by a single mode dye laser at 638 nm while the magnetic transitions in the 3A ground state were driven by two rf fields. The measured splittings in the NMR lines were found to be in good agreement with theoretical predictions. Using the Autler–Townes effect, the magnitude of the dipole moments of the mI=0↔±1 (mS=0) transitions in the ground state was determined, and found to be the same. Comparison of this latter result with the NMR spectra shows that Raman heterodyne signal intensities are determined by population factors.
Microstructural analyses of amorphic diamond, i-C, and amorphous carbon
Authors: Collins C. B. , Davanloo F. , Jander D. R. , Lee T. J. , You J. H. , Park H. , Pivin J. C. , Glejbo/l K. , Thölén A. R.
Published: July 2002

Recent experiments have identified the microstructure of amorphic diamond with a model of packed nodules of amorphous diamond expected theoretically. However, this success has left in doubt the relationship of amorphic diamond to other noncrystalline forms of carbon. This work reports the comparative examinations of the microstructures of samples of amorphic diamond, i-C, and amorphous carbon. Four distinct morphologies were found that correlated closely with the energy densities used in preparing the different materials.
Substrate orientation effects on dopant incorporation in InP grown by metalorganic chemical vapor deposition
Authors: Berger Paul R. , Chu S. N. G. , Logan R. A. , Byrne Erin , Coblentz D. , Lee James , Ha Nhan T. , Dutta N. K.
Published: July 2002

We have investigated the doping incorporation and activation of InP growth using metalorganic chemical vapor deposition on <100≳, <311≳B, and <110≳ InP substrates. Effects of orientation, growth temperature, and V/III fluxes were studied. The dopants used were Zn from dimethylzinc [(CH3)2Zn] and diethylzinc [(C2H5)2Zn], S from hydrogen sulfide [H2S], Si from silane [SiH4], and Sn from tetraethyltin [(C2H5)4Sn]. The incorporation and activation of the p-type dopant Zn are elevated on the <311≳B and <110≳ planes, while the incorporation is suppressed for the n-type dopants (S, Si, and Sn). The n-type dopant Sn has similar incorporation and activation on the various substrate orientations studied. Anomalous Zn doping on the higher order planes <311≳B and <110≳ lead to the Zn incorporation exceeding the solubility limit in InP. Incorporated Zn levels as high as 1.0×1019 cm−3 were measured, and the corresponding activated Zn level was as high as 5.4×1018 cm−3 on a <110≳ InP substrate. Interdiffusion of the p-type dopant Zn into the S-doped n-type InP substrate is inhibited by a high S-doping level and segregates at the substrate–epilayer interface. If the S-doping level is lower than the Zn concentration, then Zn diffuses deep into the substrate at a uniform level.
Temperature dependent mobility in single-crystal and chemical vapor-deposited diamond
Authors: Pan L. S. , Kania D. R. , Pianetta P. , Ager J. W. , Landstrass M. I. , Han S.
Published: July 2002

The combined electron and hole mobility of a single-crystal type IIa natural diamond and a polycrystalline diamond film deposited by chemical vapor deposition (CVD) were measured using transient photoconductivity as a function of excitation density (1013–1017 cm−3) and temperature (120–410 K). In natural diamond the temperature dependence suggests that the mobility is limited by phonon scattering at low free carrier densities, and by electron-hole scattering at high densities. The combined electron and hole phonon-limited mobility at room temperature is 3000 (±500) cm2/V s. In the CVD film, the mobility at room temperature was estimated to be 50 cm2/V s at low excitation densities. The temperature dependence of the mobility-lifetime product at low excitation densities is different from that of natural diamond, and suggests that charged center scattering, rather than acoustic phonon scattering, is the dominant effect. High densities of nitrogen and dislocations are known to be present in the natural diamond, and these appear to be the dominant recombination sites which limit the carrier lifetime. In the polycrystalline film a variety of structural defects and impurities are believed to exist, but it is unknown which of these dominates the transport and recombination properties.
Structural modification in reactive-ion-etched i-InP and n+-InP studied by Raman scattering
Authors: Maslar J. E. , Bohn P. W. , Ballegeer D. G. , Andideh E. , Adesida I. , Caneau C. , Bhat R.
Published: July 2002

Structural and electrical property modifications in i-InP and n+-InP by reactive ion etching have been characterized by using Raman scattering to observe changes in the positions and intensities of intrinsic phonons and coupled phonon-plasmon bands. Different etch gas compositions (Ar, He, CH4/H2, CH4/Ar, CH4/He, and CH4/H2/Ar), bias potentials (0–500 V), and etch times were examined. Electrical property changes were followed by correlating results with a one-sided abrupt junction model. Ar and He, which interact with the material by physical sputtering processes, were found to induce the greatest structural and electrical modifications. Ar-etched samples exhibited the greatest structural modification, with evidence of structural damage coming from far beyond the calculated penetration depth of low-energy Ar+, while samples etched in methane-based plasmas showed very little structural perturbation. Etching in all of the gas mixtures used produced some degree of electrical modification in n+-InP, with He plasmas causing the most significant changes. In general, samples etched with lower ion energies and sputter components exhibited the least structural and electrical modification.
Oxidation of silicon in plasma afterglows: New model of oxide growth including recombination of diffusing O atoms
Authors: Peeters Jozef , Li Li
Published: July 2002

The mechanism of plasma afterglow oxidation of silicon by atomic oxygen is discussed in terms of a physical model that includes recombination of the oxidant atoms during their diffusion through the SiO2 layer. Inclusion of a first-order O loss term in the continuity equation that governs the unbound O atoms leads to a biexponential concentration profile in the oxide. The corresponding time-dependent O flux across the SiO2/Si interface results in an oxide growth equation that is a more general form of the classical Deal–Grove model. Confrontation with available experimental data shows that the general expression can be abbreviated for oxide widths w≥0.1 nm as t= (A2/B)[exp(w/A)+exp(−w/A)−exp(wi/A)−exp(−wi/A)], where wi is the native oxide width. The two model parameters are A≡√D/k and B≡2HD[O]g/nb, with D being the diffusivity and k the first-order loss rate constant of unbound O atoms in SiO2, H the SiO2/gas Henry equilibrium ratio of free O atoms, [O]g=the gas-phase O atom concentration, and nb=the bound-O number density in SiO2. The two-parameter model provides excellent fits (σ≂2% of final w) to the available data on both n- and p-type Si, strikingly better than fits obtained by the Deal–Grove equation in particular for p-type Si. The values deduced for the model parameters A and B provide proof for the controlling importance of the O-atom recombination process, especially for p-type Si. The model parameters also allow values to be derived for other pertaining physical constants; e.g., the product HD is deduced to be 2.4×10−9 cm2 s−1 at T≂850 K, in close agreement with the known HD value for neon atoms in SiO2, equal to 5.2×10−9 cm2 s−1.
Characterization of compositionally graded Si1−xGex alloy layers by photoluminescence spectroscopy and by cathodoluminescence spectroscopy and imaging
Authors: Higgs V. , Lightowlers E. C. , Fitzgerald E. A. , Xie Y. H. , Silverman P. J.
Published: July 2002

Photoluminescence (PL) spectroscopy, cathodoluminescence (CL) spectroscopy and imaging, and preferential defect etching and optical microscopy have been used to characterize compositionally graded Si1−xGex alloy layers grown by molecular beam epitaxy. Si1−xGex capping layers grown on the compositionally graded layers have low threading dislocation densities, and both PL and low-beam energy CL spectra show bound exciton luminescence features identical with those observed in bulk Si1−xGex alloys and relatively weak dislocation related D-band features. Increasing the beam energy increases the relative strength of the D bands in the CL spectra, indicating that they are associated with the misfit dislocations in the compositionally graded layer. This has been confirmed by combined chemical etching and PL spectroscopy measurements. The misfit dislocations can be observed by monochromatic CL imaging at a high-beam energy using a narrow band pass filter centerd on the D4 band.
Valence energy-band structure for strained group-IV semiconductors
Authors: Manku T. , Nathan A.
Published: July 2002

A generic expression is presented for the valence-band structure of strained group-IV semiconductors (Si, Ge, and Si1−xGex alloys) that takes into account spin-orbit coupling. The valence band is obtained using k⋅p perturbation theory coupled with deformation potential theory. The band-structure equation is put into a simplified form that can be readily used, viz., ∑i=03 ∑j=03−iaijEkjk2i=0, where k is the wave-vector magnitude, Ek is the energy at k, and the coefficients aij are functions of band parameters and strain components. The band structure of strained silicon is qualitatively analyzed in relation to the well-established piezoresistivity coefficients. Furthermore, a new coefficient is introduced that describes the first-order change in carrier concentration effective mass per unit applied stress for different stress directions.
Substrate temperature effect on the structural anisotropy in amorphous Tb–Fe films
Authors: Harris V. G. , Hellman F. , Elam W. T. , Koon N. C.
Published: July 2002

Using extended x-ray absorption fine structures (EXAFS) measurements we have investigated the atomic environment around the Fe atom in a series of amorphous Tb0.26Fe0.74 films having different magnetic anisotropy energies owing to different deposition temperatures. The polarization properties of synchrotron radiation allowed the separate study of structure parallel and perpendicular to the sample plane. An anisotropy between these two structures was observed. Modeling results indicate this anisotropy is due to anisotropic pair correlations where the Fe–Fe pairs are statistically preferred in-plane and the Fe–Tb pairs out-of-plane. The amplitude of this anisotropy scales with both the substrate temperature and the magnetic anisotropy energy. A ≊1% in-plane compression of the Fe–Fe distance was measured between the in-plane and out-of-plane structure of the sample grown at 77 K. This sample had no detectable local chemical anisotropy suggesting that intrinsic stress plays an important role in determining its magnetic anisotropy.
Magnescope: Applications in nondestructive evaluation
Authors: Devine M. K. , Jiles D. C. , Eichmann A. R. , Kaminski D. A. , Hardwick S.
Published: July 2002

This paper describes recent results obtained with the Magnescope, which has been used on location in industrial environments and has successfully detected impending fatigue failure, creep damage, applied stress, and microstructural differences. It is concluded that the device provides a useful nondestructive method for evaluating the mechanical properties of materials through the measurement of their structure sensitive magnetic properties.
Crystallographic structure of CoPtCr/CrV thin films as revealed by cross-section TEM and x-ray pole-figure analysis and its relevance to magnetic properties
Authors: Parker M. A. , Howard J. K. , Ahlert R. , Coffey K. R.
Published: July 2002

The crystallographic structure and coercive force of Co75Pt12Cr13/CrVx bilayer films sputter deposited on NiP/AlMg disks used in longitudinal magnetic recording were characterized as a function of varying V content from pure Cr through pure V. The coercive force of the CoPtCr peaked at an intermediate composition of the CrVx sublayer. The origin of this effect was elucidated by x-ray diffraction, x-ray pole-figure analysis, cross-section TEM, and elongated probe microdiffraction. The improving degree of epitaxy between the CoPtCr and the CrVx sublayer, the increasing fraction of Cr grains favoring the growth of (112̄0) Co grains with c axis in-plane, a narrowing of the mosaic spread in the orientation of Co grains, and an increasing size of Co regions with the <112̄0≳ fiber axis orientation as CrVx composition approaches values between 80/20 and 50/50 Cr/V content account for the observed coercivity increase.
Multiple oscillation of whispering-gallery-mode dye lasers in green and orange regions using mixed-dye-doped solid microspheres
Authors: Taniguchi Hiroshi , Tanosaki Shinji , Yamada Hiroshi , Fujiwara Tamiya , Baba Mamoru
Published: July 2002

Mixed-dye-doped solid microspheres are excited by a transversely excited-atmospheric ultraviolet N2 laser to obtain a multiple oscillation of a whispering-gallery-mode (WGM) dye laser in both green and orange regions. The multiple oscillation exhibits separate modes of WGMs in both spectral regions.
Angular distribution of the sputtered atoms from TbFeCo targets
Authors: Chao Shiuh , Jeng Tzuan-Ren , Lo Vien-Shien , Huang Der-Ray , Hsiao Tsai-Chu
Published: July 2002

The angular distribution of the sputtered Tb, Fe, and Co atoms from the elemental targets could be described by cosn θ distribution with n=1.90, 0.54, and 1.01 for Tb, Fe, and Co, respectively. For TbFeCo composite targets with mixed elemental and intermetallic compound phases, the overall angular distribution of the sputtered Tb, Fe, and Co atoms from the mixed phases could also be described by the cosn θ distribution function, and the values of the n’s were related to the volume percentage of the intermetallic compound content in the composite target. This was not true of the Tb distribution for a target containing high intermetallic compound content. In that sample, an off-normal term has to be added to the cosn θ distribution function. It was found that a composite target with about 23 vol % intermetallic compound would produce a uniform composition distribution of TbFeCo film on the substrate.
Optical power handling properties of polymeric nonlinear optical waveguides
Authors: Mortazavi M. A. , Yoon H. N. , Teng C. C.
Published: July 2002

Polymeric nonlinear optical waveguides of a copolymer of 4-(N′-2-methacroyloxyethyl-N- methyl-amino)-4′-nitrostilbene and methyl methacrylate were tested for optical power handling capability at near-infrared wavelengths. When exposed to about 5×105 W/cm2 optical power density at 1325 nm wavelength laser light, the waveguide showed a rapid decay of optical transmission on the order of about 3 dB/h. Operation of the waveguides in an oxygen-free environment significantly reduced the decay rate to greater than 0.25 dB/h. The decay was a result of spatially inhomogeneous change of refractive index distributed along the length of the waveguides. Micrographs showing the photoinduced local variations of refractive index and the resulting loss of optical confinement of the waveguides are presented.
Nucleation and growth in the initial stage of metastable titanium disilicide formation
Authors: Ma Z. , Xu Y. , Allen L. H. , Lee S.
Published: July 2002

Initial stage of the C49–TiSi2 formation was investigated at 530 °C and at a rate of 10 °C/m using transmission electron microscopy. Morphological studies reveal that the C49 phase first separately nucleates at the interface between amorphous silicide and crystalline silicon, then followed by simultaneous lateral and vertical growth. The growth proceeds very fast until the formation of a continuous layer of C49–TiSi2. Local chemical analysis shows that the composition range of the amorphous silicide is narrowed due to the C49 formation. For isothermal annealing, a linear density of the C49 nuclei is about 6.7×10−3/Å, and remains the same upon prolonged annealing. In the case of annealing at 10 °C/m, the linear density depends on temperature, reaching a maximum of 7.2×10−3/Å at around 575 °C.
On the current mechanism in reverse-biased amorphous-silicon Schottky contacts. I. Zero bias barrier heights and current transport mechanism
Authors: Nieuwesteeg K. J. B. M. , van der Veen M. , Vink T. J.
Published: July 2002

A study of the zero-bias barrier heights of hydrogenated amorphous-silicon-based Schottky diodes and the prevailing current transport mechanisms in these structures is made using electrical and electro-optical techniques. Several series of devices were made using Cr, Mo, W, and Pt as Schottky metals. The current-voltage characteristics of the devices were obtained with their temperature dependence. The barrier heights were determined independently using internal photoemission experiments at three temperatures between 270 and 380 K. In devices where the Schottky barrier is deposited on top of the semiconductor material, the saturation current density is found to be most likely determined by combined drift and diffusion of the carriers. In devices where the Schottky barrier is formed at the bottom of the diode, the transport mechanism tends towards thermionic (field) emission, but only slight effects of the prevailing transport mechanism on the electrical performance of these diodes were observed. Also, in these devices a relatively defect-rich a-Si:H layer at the bottom (Schottky) contact could be detected opto-electronically, which prohibited barrier height determination using internal photoemission. For the influence of the metal work function φm on the electron-barrier height φb we obtain φb=(0.10±0.02)φm+(0.48±0.12), which is in good agreement with a previous determination of the dependence of the barrier for holes on φm.
Experimental considerations concerning the velocity measurement of the relativistic electron beam in a gyrotron by means of Thomson scattering
Authors: Siegrist M. R. , Soumagne G. , Tran M. Q.
Published: July 2002

The feasibility of Thomson scattering to determine the beam velocity in a gyrotron has been analyzed and preliminary experiments to implement such a system on our 100 GHz quasi-optical gyrotron are reported. Although the project had to be abandoned due to technical problems, the conclusions are that for the 90° scattering arrangement discussed it should be possible to determine at least one velocity component with an acceptable signal-to-noise ratio.
Modeling of refractive index profiles of He+ ion-implanted KNbO3 waveguides based on the irradiation parameters
Authors: Fluck D. , Jundt D. H. , Günter P. , Fleuster M. , Buchal Ch.
Published: July 2002

Planar optical waveguides were fabricated by He+ ion implantation in KNbO3 crystals with doses from 2.5×1014 to 1×1016 cm−2 and energies from 1 to 3.5 MeV, and the index profiles were analyzed. A comparison with theoretical radiation damage profiles calculated by the trim code indicates that the index change is mainly caused by nuclear collisions. However, at higher implantation doses the influence of the electronic excitation on the refractive index profiles cannot be neglected. A method is derived to predict the index profile of nb from the He+ implantation parameters energy and dose. The measured mode spectra of waveguides produced by single and dual energy implantation are in excellent agreement with the predicted spectra.
Effect of cobalt substitution on magnetic properties of R2Fe17 silicides (R=Y, Gd, Tb, Er, and Tm)
Authors: Pourarian F. , Obermyer R. T. , Sankar S. G.
Published: July 2002

Magnetic characteristics and unit-cell dimensions of the (off-stoichiometric) R2Fe17-type alloys based on R2Fe14−xCoxSi2, where R=Gd, Tb, Er, Tm, and Y and x=4 were determined. Partial substitution of Fe by Co slightly increases the saturation magnetization of the alloys and produces an average increase in the Curie temperature (Tc) of 55 K per Co atom. The enhancement of the Curie temperature with the addition of cobalt is attributed to the strengthening of the average 3d-3d exchange interaction. For Er- and Tm-containing compounds, replacement of Fe by Co has a remarkable effect in shifting the observed spin reorientation temperature toward higher temperatures. These results are discussed in terms of the influence of the interaction of the 4f electrons of the rare-earth ions with the 3d electrons of the transition-metal ions, which modifies the overall anisotropy of the alloys.
Effect of duct bias on transport of vacuum arc plasmas through curved magnetic filters
Authors: Anders André , Anders Simone , Brown Ian G.
Published: July 2002

The plasma output of a 90° magnetic macroparticle filter of vacuum arc plasma was monitored by a Langmuir probe as a function of bias of the duct wall and guiding magnetic field. Maximum plasma transport through the filter was found at a positive bias of about 20 V. A relatively small magnetic field of 10–30 mT is sufficient for effective guiding of the plasma, and further increase of the guiding field improves the filter efficiency only gradually. The potential of a floating duct changes from negative to positive when the guiding field is increased. This can be explained by the balance of electron and ion flux transverse to the magnetic field. Saturation in the plasma output at high guiding field (≳120 mT) is observed for carbon but not for heavy elements. The transport of plasma through bent ducts is made possible by the magnetic pressure of the guiding field, and by sheath and space-charge electric fields.
Optical spectroscopy on implanted and annealed silicon wafers: Plasma resonance wavelength
Authors: Christofides Constantinos , Othonos Andreas , Bisson Michel , Boussey-Said Joumana
Published: July 2002

A study of the effects of annealing temperature on phosphorus-implanted silicon films is carried out. Fourier transform infrared spectroscopy has been performed with two different instruments in the spectral ranges of 0.75–4 μm and 3–25 μm. In the first spectrum range special attention was given to the influence of implantation dose on reflectivity. The minimum reflectivity associated with plasma resonance has been fully employed for estimation of the electrical activation of implanted impurities. Other conclusions concerning the activation of free carriers (implanted impurities) with implantation dose and annealing temperature have been reached.
Effects of additive elements on electrical properties of tantalum oxide films
Authors: Fujikawa Hisayoshi , Taga Yasunori
Published: July 2002

Ta2O5-based composite films prepared by magnetron sputtering have been investigated with respect to their dielectric properties. As additive third oxides, Y2O3 and WO3 were found to be effective materials for improving insulating properties. In these composite films, the dielectric constant remained unchanged. The maximum storage charge of the composite films was twice that of Ta2O5 films. The main reason for improving the insulating properties could be explained by the charge compensation of excess oxygen by these additive oxides.
Photoluminescence of Mg-ion implantation in low-temperature grown GaAs
Authors: Yu P. W. , Yen M. Y. , Stutz C. E.
Published: July 2002

Photoluminescence properties of Mg-ion implanted layers of low-temperature (179–400 °C) grown molecular beam epitaxial GaAs are reported. The Mg incorporation into the Ga site mainly produces the Mg-related donor-acceptor pair transition. The Mg incorporation depends strongly on the growth temperature of the layers. Mg trapping at defect centers formed by the excess As increases exponentially with the increase of the reciprocal growth temperature and is the dominant mechanism for the failure of Mg to incorporate into the Ga site. The possibility of the trapping center for Mg being the Asin-related defect originating from As-rich growth of low temperature GaAs is discussed.
Oxide and interface degradation resulting from substrate hot-hole injection in metal-oxide-semiconductor field-effect transistors at 295 and 77 K
Authors: Van den bosch Geert , Groeseneken Guido , Maes Herman E. , Klein Richard B. , Saks Nelson S.
Published: July 2002

Substrate hot-hole injection (SHI) induced hole trapping and interface trap generation have been characterized at 295 and 77 K. At both temperatures, the trapping is independent of the injection conditions in the silicon, and is fairly insensitive to the oxide field. Initial trapping efficiencies are about 2.5 times higher at 77 K. The experiments show that essentially the same traps are being filled at the two temperatures, and that the increase in trapping efficiency can be attributed to a larger effective cross section of the traps at 77 K. Hot-hole induced interface trap generation is observed to be independent of the injection conditions in the silicon, and to decrease with increasing oxide field magnitude. More interface traps are generated at 77 K for the same injected fluence. This is in contrast to the characteristics of irradiation-induced interface trap generation. The presence of holes at the Si-SiO2 interface is the key factor in the direct interface trap generation process acting during hot-hole injection. Following low-temperature SHI, an additional temperature-activated generation mechanism, attributed to the migration of H+, is observed in isochronal anneal experiments. This delayed mechanism is identical to the one that accounts for most of the irradiation-induced interface trap generation.
Electric field forced phase switching in La-modified lead zirconate titanate stannate thin films
Authors: Brooks K. G. , Chen J. , Udayakumar K. R. , Cross L. E.
Published: July 2002

Electric field forced antiferroelectric to ferroelectric phase switching has been demonstrated in thin films of Pb0.97La0.02(Zr,Ti,Sn)O3 perovskites for the first time. Several compositions in the tetragonal antiferroelectric phase field of this system were prepared in thin film form by a sol-gel technique. Forward and reverse switching threshold fields of 27–103 kV/cm and 18–62 kV/cm, respectively, were determined from polarization-electric field hysteresis and incremental capacitance data. Switching times as fast as 300 ns were recorded for one of the antiferroelectric compositions. An electric field induced longitudinal strain of 0.16% was measured for a film of composition (Pb0.97La0.02)(Zr0.60Ti0.10Sn0.30)O3 using a laser ultradilatometer. These films are candidate materials for high charge storage integrated capacitors and microelectromechanical devices requiring large nonlinear strain response.
High-resolution x-ray scattering studies of epitaxial GdBa2Cu3O7−δ thin films
Authors: Cox U. J. , Crain J. , Hatton P. D. , Green G. S. , Dai D. Y.
Published: July 2002

High-resolution triple-crystal x-ray scattering techniques have been used to study high-temperature superconducting thin films of Gd-Ba-Cu-O grown in situ by dc magnetron sputtering onto substrates of (001) LaAlO3 and SrTiO3. The measurements suggest that the thin films are single crystal. Evidence is found for both c- and a-axis-oriented films on the LaAlO3 samples. In particular, no strain is observed in the films except at the interface between films of different relative orientation. No low-temperature structural transitions are observed in the films.
Evidence for field enhanced electron capture by EL2 centers in semi-insulating GaAs and the effect on GaAs radiation detectors
Authors: McGregor Douglas S. , Rojeski Ronald A. , Knoll Glenn F. , Terry Fred L. , East Jack , Eisen Yosef
Published: July 2002

The performance of Schottky contact semiconductor radiation detectors fabricated from semi-insulating GaAs is highly sensitive to charged impurities and defects in the material. The observed behavior of semi-insulating GaAs Schottky barrier alpha particle detectors does not match well with models that treat the semi-insulating material as either perfectly intrinsic or as material with deep donors (EL2) of constant capture cross section compensated with shallow acceptors. We propose an explanation for the discrepancy based on enhanced capture of electrons by EL2 centers at high electric fields and the resulting formation of a quasineutral region in the GaAs. Presented is a simple model including field enhanced electron capture which shows good agreement with experimental alpha particle pulse height measurements.
Estimation of fatigue exposure from magnetic coercivity
Authors: Chen Z. J. , Jiles D. C. , Kameda J.
Published: July 2002

An investigation of the effects of fatigue on A533B steel under constant load amplitude is reported in this paper. It was found that the plastic strain of the sample accumulated logarithmically with the number of stress cycles after initial fatigue softening. Based on the fact that plastic strain is often linearly related to the coercivity of material, at least for small changes of Hc, a phenomenological relationship has been developed and tested to correlate the number of stress cycles to this magnetic parameter. This result represents the first successful attempt to relate the fatigue exposure directly to a magnetic parameter.
Bolometers for infrared and millimeter waves
Authors: Richards P. L.
Published: July 2002

This review describes bolometric detectors for infrared and millimeter waves. The introduction sketches the history of modern bolometers, indicates how they fit into the more general class of thermal detectors, and describes the types of applications for which they are the optimum solution. Section I is a tutorial introduction to the elementary theories of bolometer response, of thermal radiation, and of bolometer noise. Important results are derived from the laws of thermal physics in the simplest possible way. The more rigorous theories of bolometer response and noise that are required for quantitative understanding and optimization are then summarized. This material is intended to provide the background required by workers who wish to choose the appropriate bolometer technology for a given measurement, or to evaluate a novel technology. Section II, then describes the various components of an efficient bolometer and gives details of the fabrication and performance of modern bolometers. This discussion focuses on composite bolometers with semiconducting thermometers for operation at and below liquid helium temperatures. The tradeoffs involved in using superconducting thermometers at low temperatures are discussed. Finally, a discussion is given of bolometers for operation at liquid nitrogen temperature which use the new high-Tc superconductors as thermometers.
Calculation of the transport matrix for the coupled diffusion of dopants and vacancies
Authors: List S. , Pichler P. , Ryssel H.
Published: July 2002

A new approach is used for the calculation of transport coefficients for dopants and vacancies from atomic jump frequencies in the presence of dopant and vacancy gradients. The atomistic model involves seven different jump frequencies depending on the coordination numbers of the vacancy with respect to the dopant before and after the jump. With this approach, an interaction potential between the dopant and the point defect is taken into account with a maximum range up to the third coordination site. Results are shown for different types of attractive potentials with rectangular well shape and for Coulomb potentials. It is demonstrated that the fluxes of dopants and vacancies caused by a vacancy gradient may be in the same or opposite direction, depending only on the range of the potential.