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  • 2000-2004  (23)
  • 1990-1994  (90)
  • 1955-1959  (13)
  • 1945-1949  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Raman studies of plasmon modes in a drifting two-dimensional electron gas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1701-1705 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the first Raman-scattering studies of the behavior of the intrasubband plasmon mode of a two-dimensional electron gas which is undergoing lateral drift in an applied electric field. The data clearly show the expected Doppler shifts of the modes traveling up- and downstream, together with the expected dependence on the wave vector, but at higher drift velocities, the expected linear shift is distorted because of electron heating effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357684
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Poly-alpha-methylstyrene (1956)
    s.l. : American Chemical Society
    Industrial & engineering chemistry 48 (1956), S. 2123-2131 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie50564a026
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of anisotropy fields in recording media (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5711-5713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work describes an experimental study which reviews the various techniques that can be used for determination of anisotropy fields in recording media. At the present time this topic is of considerable importance due to the need to understand the detailed mechanisms of magnetization reversal and the factors that control the switching field distribution in recording media. We have used a metal-particle-based tape material and have employed various magnetic techniques for the determination of the apparent anisotropy field, HK. The techniques included hysteresis loops measured in a direction transverse to the texture direction of the tapes, single-point detection in the successive derivatives of the magnetization with respect to the field, transverse susceptibility measurement, and the variation of the bulk coercivity with temperature. We find the temperature variation of coercivity produces values of HK far smaller than values determined by other methods due to orientation effects. General agreement is seen for the other techniques mentioned and results for samples with differing degrees of texture show that the apparent anisotropy field of the grains as measured by these techniques is influenced greatly by orientation effects. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372498
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    rf ion source development for neutron generation and for material modification : Papers from the Ninth International Conference on Ion Sources (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 934-936 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: rf driven multicusp ion sources have been successfully used in various different applications. Lately the Plasma and Ion Source Technology Group at Lawrence Berkeley National Laboratory has been developing a rf ion source for neutron production and a high current density cw-operated ion source for SIMOX (Separation by Implantation of Oxygen)-application. The group has developed a small ion source, which consists of a quartz plasma chamber, an external rf-antenna, an extraction electrode, and a target assembly, all in a tube that is approximately 25 cm in length and 5 cm in diameter. Another neutron generator currently under development is a multiaperture, high power generator. The neutron generator currently operates at 1% duty cycle, 80 kV, and 150 mA of deuterium beam. The neutron yield measured from the generator is 1.6×107 n/s. For oxygen implantation, the group has been developing a source which could provide a high percentage of O+ at high current density using cw operation. A dual-antenna has been developed for the source to ensure reliable long life operation. The development of these sources will be discussed in this article. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430519
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Low-frequency measurements of cyclotron resonance in a high-mobility 2D electron gas in GaAs/AlGaAs heterostructures (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4736-4738 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cyclotron resonance in GaAs/AlGaAs heterostructures, containing a high-mobility two-dimensional electron gas (2DEG), has been investigated with the help of a resonator technique over the frequency range 26–34 GHz. Heterostructures with mobilities from 2×105 to 1.6×106 cm2/V s have been measured. The microwave conductivity of the 2DEG is well described by the Drude model and momentum relaxation time values are found to be close to dc values. The cyclotron mass was found to be 0.068±0.002m0.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352081
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  • 6
    Electronic Resource
    Electronic Resource
    Plasmon excitation and self-coupling in a bi-periodically modulated two-dimensional electron gas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 6049-6061 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report far infrared (FIR) studies of plasmons in spatially modulated two-dimensional electron gases (2DEGs) in AlGaAs/GaAs heterostructures using biased overlaid metal gratings, including interdigitated gratings, both as optical couplers and as spatially modulating gates. Comparison of the experimental results with the predictions of scattering matrix calculations of the FIR response of a modulated 2DEG in the presence of a perfectly conducting lamellar grating allow us to deduce the spatial variation of the number density distribution in the 2DEG as a function of grating bias. For the interdigitated grating gates, the 2DEG can be modulated at a period of twice that of the grating fingers by differentially biasing alternate fingers; 2D plasmon resonances have been observed at half-integral values of the grating wave vector G, corresponding to the electrically induced periodicity of the 2DEG modulation itself acting as an optical coupler in addition to the metal grating. The observed G/2 plasmon frequencies decrease with increasing amplitude of the 2DEG number density modulation, in quantitative agreement with those obtained from scattering matrix calculations of the optical response of a modulated 2DEG under a perfectly conducting lamellar grating; calculations of the oscillating charge density profiles show that this occurs because, as the modulation amplitude increases, the oscillation becomes localized in regions of low 2DEG number density which are also under one of the sets of grating fingers, and is therefore better screened.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350462
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  • 7
    Electronic Resource
    Electronic Resource
    Electron transport across a wide AlGaAs barrier (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5606-5621 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An experimental and theoretical study has been made of electron transport over a wide AlGaAs barrier with graded interfaces sandwiched between GaAs contact layers. The width of the central barrier region was varied between 700 and 2100 A(ring). Two series of samples with nominally identical structures but from different sources were investigated. Extensive measurements of both the voltage and temperature dependence of the current were made, as well as measurements of capacitance and magnetoresistance. Drift-diffusion thermionic emission theory has been used to interpret the data. Both numerical and analytical solutions of the model have been developed and were found to be in good agreement with each other. The presence of space charge in the barrier region, which has the effect of increasing the barrier height, was seen to be crucial to an understanding of the data. When the effect of space charge was included in the model good agreement was obtained between theory and experiment for electric fields up to 10 kV cm−1. The numerical solution required only one adjustable parameter, namely the value of the space-charge density. The parameters used in the analytical model were all derived from the experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354222
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of ion energy on Sn donor activation and defect production in molecular beam epitaxy GaAs doped with Sn ions during growth (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4375-4381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The production of electrically active defect centers in molecular beam epitaxy (MBE) GaAs irradiated with low energy (50–500 eV) Sn ions during growth has been investigated as a function of ion energy. GaAs was doped n type during growth with a specially designed Sn focused ion beam column mounted on a MBE growth chamber. The 77 and 300 K Hall mobility and carrier concentration of the GaAs depended strongly on the ion energy, thus providing a sensitive measure of the concentration of ion-induced acceptorlike defect centers. The material was found to be nonconducting for ion energies greater than 200 eV, while a systematic decrease in the acceptor concentration, and consequent increase in the mobility, was observed as the ion energy was decreased below this value. A peak mobility of 90 000 cm2 V−1 s−1 at a carrier concentration of 1×1014 cm−3 was achieved (at 60 K) which is in excess of that obtained in other reports of ion-doped GaAs. A similar dependence on ion energy was found in the 4.2 K photoluminescence spectra of the ion-doped GaAs, characterized by the appearance of a broad acceptor level peak and a decrease in the overall luminescent intensity with increasing ion energy. The lowest energy doped samples provided high quality spectra with narrow linewidths comparable with thermal (Si) doped material. Using the above data, a mechanism is proposed for the production of acceptor centers in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354405
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Domain structure of as-cast and annealed FeSiB amorphous wires : 35th annual conference on magnetism and magnetic materials San Diego, California (USA) 29 Oct − 1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5331-5333 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The domain structures of amorphous FeSiB wires have been studied as a function of applied field. The main features of as-cast wires are: the proliferation of surface closure domains; a distinction between core and sheath domain behavior; and a reproducible switching behavior. Transverse magnetically annealed wires have larger domains, show little sign of a sheath and a greater variety of domain displacement mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348069
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  • 10
    Electronic Resource
    Electronic Resource
    Site-selective laser spectroscopy of deuterated SrF2:Er3+ (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2166-2177 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Laser selective excitation and optical absorption of deuterated SrF2:0.05% Er3+ crystals have revealed eight Er3+ ion centers involving D− ion charge compensation, nine new Er3+–F− centers not associated with D− ions and several approximately cubic symmetry Er3+ centers. In contrast to the trigonal symmetry of the principal F− center, the dominant arrangements in the D− ion charge compensation case are derived from a tetragonal symmetry center. Detailed spectroscopic results for the new centers are presented. Fluorescence polarization ratios are listed for three centers ( J, B, and G1) present in either SrF2:Er3+ or CaF2:Er3+ and crystal-field analyses of these, based on assumed trigonal symmetry, are also reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458008
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