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  • 1
    Electronic Resource
    Electronic Resource
    Influence of a partially oxidized calcium cathode on the performance of polymeric light emitting diodes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1376-1382 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the influence of the presence of oxygen during the deposition of the calcium cathode on the structure and on the performance of polymeric light emitting diodes (pLEDs). The oxygen background pressure during deposition of the calcium cathode of polymeric LEDs was varied. Subsequently, the oxygen depth distribution was measured and correlated with the performance of the pLEDs. The devices have been fabricated in a recently built ultraclean setup. The polymer layers of the pLEDs have been spincoated in a dry nitrogen atmosphere and transported directly into an ultrahigh vacuum chamber where the metal electrodes have been deposited by evaporation. We used indium–tin–oxide as anode, OC1C10 PPV as electroluminescent polymer, calcium as cathode, and aluminum as protecting layer. We achieved reproducibility of about 15% in current and brightness for devices fabricated in an oxygen atmosphere of (very-much-less-than)10−9 mbar. For further investigations the calcium deposition was carried out in an oxygen atmosphere from 10−8 to 10−5 mbar. We determined the amount of oxygen in the different layers of the current–voltage-light characterized pLEDs with elastic recoil detection analysis and correlated it with the characteristics of the devices. The external efficiency of the pLEDs decreases continuously with increasing oxygen pressure, the current shows a pronounced minimum. The brightness mostly decreases with increasing oxygen with an indication of a slight minimum. PLEDs with completely oxidized calcium are not operational. The first contact of the pLEDs with the dry glove box environment leads to an immediate reduction of current and brightness which is caused by the cooling of the devices by several degrees. Determining reproducible characteristics of pLEDs in the vacuum requires the measurement of their temperature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383577
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  • 2
    Electronic Resource
    Electronic Resource
    A combined time-of-flight and electrostatic analyzer for low-energy ion scattering (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3910-3914 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new instrument for low-energy ion scattering (LEIS) is presented which employs a combination of electrostatic and time-of-flight analysis. In this instrument, electrostatic analysis is used to determine the kinetic energy of the ions, and flight-time analysis is used to select the mass of the ions. The combination allows us to discriminate the signals resulting from particles with a different mass than the primary ions, resulting in a very efficient suppression of signals caused by sputtered particles. The suppression of signals from sputtered particles enables more accurate determination of LEIS signals, especially for light elements. This technique is especially suited for the study of polymers and oxides, but can also be valuable for determination of low concentration of heavier elements. In this article the design of the instrument is presented and the method is demonstrated by some examples of LEIS spectra. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150011
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal stability of thin-film amorphous W-Ru, W-Re, and Ta-Ir alloys (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1212-1215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallization behavior of self-supporting thin-film amorphous W-Ru, W-Re, and Ta-Ir alloys has been studied with transmission electron microscopy. Crystallization temperatures have been observed which are much lower than the temperatures predicted by a semiempirical model: the highest observed temperatures are 775 °C for W-Ru and W-Re alloys, and 900 °C for the Ta-Ir alloys. All three systems show maximum thermal stability at a composition expected using enthalpy considerations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338171
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