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  • 1
    Electronic Resource
    Electronic Resource
    Arsenic cluster dynamics in doped GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3509-3513 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the formation of As precipitates in doped GaAs structures that were grown by molecular beam epitaxy at low substrate temperatures and subsequently annealed. We find that the As precipitates form preferentially on the n side of such fabricated GaAs pn junctions. As the coarsening process proceeds, there is a gradual increase in the amount of As in precipitates in the n-GaAs region and a decrease in the p-GaAs region; the depletion region between the pn junction becomes free of As precipitates. These observations can be understood qualitatively based on the charge states of the As interstitial and using thermodynamic arguments in which the crystal attempts to minimize the chemical potential during the anneal. The presence of the excess As results in a stable Be profile even to anneals of 950 °C. Finally, a temperature cycling technique to grow arbitrarily thick GaAs epilayers containing As precipitates was demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352326
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  • 2
    Electronic Resource
    Electronic Resource
    Transient laser-induced voltages in room-temperature films of YBa2Cu3O7−x (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4375-4376 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transient laser-induced electrical signals with peak voltages of ∼50 mV and 〈20 ns duration (full width half-maximum) have been observed in room-temperature thin films of YBa2Cu3O7−x in the absence of an applied current. It is demonstrated that the signal polarity is reversed when the films are illuminated through the substrate rather than at the air/film interface. The mechanism for this effect has yet to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344907
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  • 3
    Electronic Resource
    Electronic Resource
    Spectroscopic ellipsometry studies of YBa2Cu3O7−δ deposited on SrTiO3 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 8272-8276 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric function ε=ε1−iε2 of the YBa2Cu3O7−δ high-Tc superconducting films grown on (100) SrTiO3 (c-axis oriented) and (110) SrTiO3 (ab-oriented) substrate was measured by spectroscopic polarization modulation ellipsometry (SPME) and changes in film orientation were studied by comparing films of various thicknesses. The films deposited on SrTiO3 (100) substrates demonstrated an isotropic ε1 that changed with film thickness. It is observed that the decrease in the metallic dielectric behavior associated with the increase in the thickness of the films grown on (100) SrTiO3 substrates is mainly due to a change in the orientation of the films. The films deposited on SrTiO3 (110) showed anisotropic dielectric behavior when the plane of polarization is parallel and perpendicular to the c-axis of the film. These studies show that for this high-temperature superconductor with anisotropic dielectric behavior, SPME is a highly sensitive technique capable of measuring small changes in the film orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347435
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  • 4
    Electronic Resource
    Electronic Resource
    Electronmagnetohydrodynamic response of a plasma to an external current pulse (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1484-1494 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we examine the dynamic response of a magnetoplasma to an external time-dependent current source in the context of electronmagnetohydrodynamics (EMHD). A combined analytic and numerical technique is developed to address this problem. The set of cold electron plasma and Maxwell's equations are first solved analytically in the (k,ω) space. Inverse Laplace and three-dimensional complex Fast Fourier Transform techniques are used subsequently to numerically transform the radiation fields and plasma currents from the (k,ω) space to the (r,t) space. The results show that the electron plasma responds to a time-varying current source imposed across the magnetic field by exciting whistler/helicon waves and forming an expanding local current loop, driven by field-aligned plasma currents. The current loop consists of two antiparallel field-aligned current channels concentrated at the ends of the imposed current and a cross-field Hall current region connecting these channels. The characteristics of the current closure region are determined by the background plasma density, the magnetic field, and the time scale of the current source. The results are applied to the ionospheric generation of extremely low-frequency (ELF) and very low-frequency (VLF) radiation using amplitude modulated high-frequency heating. It is found that contrary to previous suggestions the dominant radiating moment of the ELF/VLF ionospheric source is an equivalent horizontal magnetic dipole. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872009
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  • 5
    Electronic Resource
    Electronic Resource
    Electromagnetic stability of high-power ion diodes (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1258-1267 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of high-power magnetically insulated ion diodes is investigated. Interactions between the fields, the electron flow, and the ion beam in the diode gap lead to instabilities. These instabilities are (i) low-frequency (below electron plasma frequency) instabilities that include a two-stream type instability at ω≈0 and ion transit time instabilities at finite frequency, and (ii) high-frequency instabilities (also called "magnetron instabilities'') at a frequency above the electron plasma frequency. Under certain experimental conditions, one of the ion transit time instabilities is found to be broadbanded and may become absolutely unstable. Analysis based on realistic parameters shows the elimination of this broadband instability at diode operation close to insulation threshold, and implications of this finding are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865874
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  • 6
    Electronic Resource
    Electronic Resource
    Linear stability of obliquely propagating electromagnetic waves in magnetically insulated gaps (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 3851-3857 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linear stability analysis for obliquely propagating electromagnetic waves in a magnetically insulated planar anode–cathode gap is presented. Previously published work [Phys. Fluids 24, 1821 (1981)] considered propagation perpendicular and parallel to the insulating magnetic field. Here the effect of propagation at oblique angles to the insulating field is considered. In general, growth rates decrease monotonically when the propagation angle becomes more parallel to B, and this effect is more pronounced for shorter-wavelength waves for which analytic asymptotic results are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865768
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  • 7
    Electronic Resource
    Electronic Resource
    Parametric scaling of the stability of relativistic laminar flow magnetic insulation (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 2878-2881 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The short wavelength limit of the magnetron instability of a relativistic sharp boundary electron sheath is examined. For short wavelengths the mode is localized to the sheath edge. This localization leads to a simple relationship (essentially a Lorentz transformation) between the relativistic and nonrelativistic growth rates. This relationship involves only equilibrium quantities evaluated at the sheath edge and explains previously noted trends that have been observed numerically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865208
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  • 8
    Electronic Resource
    Electronic Resource
    Stability of magnetically insulated ion diodes (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 1948-1955 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetically insulated ion diodes are examined for instability using analytical and numerical techniques. Two basic sources which drive instability are found: one due to a two-stream-type interaction between electrons and ions and the other due to ion transit time effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.864939
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic stability theory of space-charge-limited flow (1989)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1728-1737 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of a spread in energy of the emitted beam on the stability of the space-charge-limited diode is investigated. It is found that for small thermal spreads the so-called emittron or transit time instability persists and is correctly described by cold fluid equations. Thermal effects become important when ωT∼ε−1/4T, where ω is the mode frequency, T is a typical particle transit time, and εT is the ratio of the thermal energy of the beam to potential energy associated with the applied voltage. For modes with frequencies above this value, phase mixing of the particles causes a dramatic reduction in growth rate, such that other damping mechanisms will be able to stabilize the high-frequency modes. The analysis presented here applies specifically to transverse electromagnetic (TEM) modes. However, the results can be expected to qualitatively describe other modes as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858900
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  • 10
    Electronic Resource
    Electronic Resource
    Valence state of CeAl2 nanoparticles studied by Ce L3-edge x-ray absorption spectroscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3349-3350 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the Ce L3-edge x-ray absorption near-edge structure on CeAl2 nanoparticles with average diameters of 80 Å. The Ce exhibits a mixed valence with a small amount of tetravalent Ce, which is in contrast to the purely trivalent Ce observed in bulk CeAl2. A shift in the absorption edge to higher energy and a narrower linewidth are also observed in the nanoparticle samples. These spectral differences are attributed to surface effects caused by the small particle size, including a lower coordination number and higher surface pressure. The observation of nonmagnetic tetravalent Ce with the 4f0 configuration is in good agreement with the small values of magnetic entropy seen in low temperature specific heat measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372347
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