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  • 1
    Electronic Resource
    Electronic Resource
    Spin-polarized photoemission study of epitaxial Gd(0001) films on W(110) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6769-6771 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface magnetic properties of epitaxial Gd(0001) films grown on W(110) were studied with spin-polarized resonant 4f photoemission. Films grown at room temperature and subsequently annealed to 550 °C show 66% polarization at 150 K, whereas films grown at 400 °C show only 46% polarization. Both types of films exhibit surface enhanced magnetic order, with the highest observed surface critical temperature exceeding the bulk value by as much as 60 K. For the first time, a rich variety of novel surface magnetic phenomena, i.e., sizeable perpendicular polarization component and unusual temperature hysteresis in the spin polarization, are observed, demonstrating that surface magnetic reconstruction is present in Gd(0001) films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352480
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  • 2
    Electronic Resource
    Electronic Resource
    Degradation and failure of MEH-PPV light-emitting diodes (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2745-2751 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Light-emitting diodes made with poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) (MEH- PPV) using indium-tin-oxide (ITO) as anode and Ca as cathode have been examined as they age during operation in a dry inert atmosphere. Two primary modes of degradation are identified. First, oxidation of the polymer leads to the formation of aromatic aldehyde, i.e., carbonyl which quenches the fluorescence. The concomitant chain scission results in reduced carrier mobility. ITO is identified as a likely source of oxygen. The second process involves the formation of localized electrical shorts which do not necessarily cause immediate complete failure because they can be isolated by self-induced melting of the surrounding cathode metal. We have not identified the origin of the shorts, but once they are initiated, thermal runaway appears to accelerate their development. The ultimate failure of many MEH-PPV devices occurs when the regions of damaged cathode start to coalesce. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361096
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  • 3
    Electronic Resource
    Electronic Resource
    Hole limited recombination in polymer light-emitting diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1510-1512 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By comparing the quantum efficiencies of light emission in a series of poly[2-methoxy-5(2′ethyl)hexoxy-phenylenevinylene] diodes with calcium cathodes and various anode metals, we show that, in all cases electrons are the majority carrier and recombination is limited by hole injection. These conclusions are confirmed by the examination of a second series of samples in which alkanethiol barrier layers of varying thickness, are deposited on a gold anode. The highest external quantum efficiency was achieved in these experiments using a clean, semitransparent gold anode. We suggest that electron and hole injection rates play the primary role in determining current balance and that mobilities play a minor role. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123599
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  • 4
    Electronic Resource
    Electronic Resource
    Photovoltaic measurement of the built-in potential in organic light emitting diodes and photodiodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1583-1587 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measure the voltage at which the current under illumination in poly[2-methoxy, 5-(2-ethylhexoxy)-1,4-phenylene vinylene] based light emitting diodes is equal to the dark current. At low temperatures, this voltage, which we term the "compensation" voltage, is found to be equal to the built-in potential, as measured with electroabsorption on the same diode. Diffusion of thermally injected charges at room temperature, however, shifts the compensation voltage to lower values. A model explaining this behavior is developed and its implications for the operation of organic light emitting diodes and photovoltaic cells are briefly discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368227
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  • 5
    Electronic Resource
    Electronic Resource
    Bipolar charge and current distributions in organic light-emitting diodes (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1454-1460 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron and hole charge distributions and the luminance profile in organic light-emitting diodes (OLEDs) depend upon the bulk properties of the emissive layer, as well as on the injection characteristics at the anode and cathode interfaces. We address the problem of separating the relative contributions of hole injection, electron injection, and recombination to the overall performance of single layer OLED devices. Using the approach of Parmenter and Ruppel [J. Appl. Phys. 30, 1548 (1959)], and including Langevin recombination, expressions are derived for the current–voltage and radiance–current dependencies in terms of electron and hole mobility, luminescence yield, and a "current balance" factor. When one carrier dominates the current flow, as in many practical cases, it is possible to obtain a simple asymptotic relationship which permits a test of the assumptions required to obtain the analytic solution. Experimental data from poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) diodes fabricated with various anode and cathode materials are evaluated in the context of this analytical approach. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365923
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  • 6
    Electronic Resource
    Electronic Resource
    The roles of injection and mobility in organic light emitting diodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5399-5403 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical methods have been used to solve the bipolar current problem for a single emitting layer between electrodes with explicit injection characteristics. We consider ohmic and tunneling contacts at the anode and/or cathode for various ratios of hole to electron mobility. Diffusion is included and found to have minimal effect on the recombination efficiency. The recombination profile is dictated mainly by the ratio of mobilities, less so by contacts. Maximum efficiency is obtained for two ohmic contacts. When the injection is imbalanced, higher efficiencies are achieved when the majority carrier has the lower mobility. At sufficiently high voltages, the current tends towards balance, allowing for maximum efficiency. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367369
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  • 7
    Electronic Resource
    Electronic Resource
    C60 sensitization of a photorefractive polymer (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2967-2969 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fullerene molecule C60 is shown to act as a useful sensitizer of a recently discovered photorefractive polymer. Measurements of the steady-state diffraction efficiency, grating growth rate, and other photorefractive properties are presented as a function of C60 concentration, writing intensity, and applied electric field. The dc photoconductivity, grating growth rate, and steady-state diffraction efficiency all increase by as much as a factor of 20 upon doping with up to 0.2 wt % C60. The sensitization appears to result from a small increase in the carrier generation efficiency and a larger increase in the useful optical absorption at the operating wavelength, 647 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108033
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  • 8
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance studies in the bilayer system Ni0.80Fe0.20/Mn0.50Fe0.50B: Exchange anisotropy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3681-3683 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance of Permalloy in the bilayer system Ni0.80Fe0.20/Mn0.50Fe0.50 has been used as a probe of the exchange anisotropy at the interface between the ferromagnetic Permalloy layer and the antiferromagnetic manganese iron. For rotation of the applied magnetic field in the plane of the film, the resonance condition exhibits a unidirectional anisotropy which relates directly to the exchange bias field, as measured, for example, by the shift of the hysteresis loop. In the perpendicular orientation, and for Permalloy layer thicknesses greater than about 400 A(ring), one or more standing spin wave modes are seen in addition to the uniform FMR. The indexing of these modes permit an evaluation of the boundary condition at the ferromagnet/antiferromagnet interface, in terms of partial spin pinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334987
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  • 9
    Electronic Resource
    Electronic Resource
    Numerical simulations of the electrical characteristics and the efficiencies of single-layer organic light emitting diodes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7426-7432 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used numerical methods to calculate the current and the efficiency of single-layer organic light emitting diodes, taking into account field-dependent mobilities, diffusion, and thermionic injection at the metal/organic interfaces. It is shown that when the barrier for charge injection from the metal to the organic is lower than 0.3 eV, the contact is, for practical purposes Ohmic, supplying the bulk of the organic layer with a space charge limited current. Determination of the carrier mobility by fitting experimental current–voltage data is discussed and the voltage dependence of the current and the efficiency are analyzed. The recombination profile is shown to evolve with voltage, shifting towards the electrode which injects the carrier with the lower mobility. The numerical results are compared with experimental data from poly[2-methoxy,5-(2-ethylhexoxy)-1,4-phenylene vinylene] (MEH-PPV) based devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369373
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  • 10
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    Optically isolated, 2 kHz repetition rate, 4 kV solid-state pulse trigger generator (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-03-06
    Description: This paper presents the design and operation characteristics of a solid-state high voltage pulse generator. Its primary utilization is aimed at triggering a gaseous spark gap with high repeatability. Specifically, the trigger generator is designed to achieve a risetime on the order of 0.1 kV/ns to trigger the first stage, trigatron spark gap of a 10-stage, 500 kV Marx generator. The major design components are comprised of a 60 W constant current DC-DC converter for high voltage charging, a single 4 kV thyristor, a step-up pulse transformer, and magnetic switch for pulse steepening. A risetime of
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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