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  • 1
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1383577
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  • 2
    Digitale Medien
    Digitale Medien
    Erratum: "Ion-channeling analysis of boron clusters in silicon" [J. Appl. Phys. 90, 4741 (2001)] (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5507-5507 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1463446
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  • 3
    Digitale Medien
    Digitale Medien
    Ion-channeling analysis of boron clusters in silicon (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 4741-4747 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have measured axially channeled Rutherford backscattering spectra of Si1−xGex nanofilms in silicon(001). A step in the yield of the host crystal was found for off-normal axes at the depth of the nanofilm. The step was measured as a function of the angle between the incoming beam and the [011] axis and shows two maxima. It is found that Monte Carlo simulations assuming tetragonal distortion reproduce the experimental results. A universal curve was derived which enables determination of the tetragonal distortion from ion-channeling experiments, for a given film thickness. The results are compared with XRD measurements. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1405838
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  • 4
    Digitale Medien
    Digitale Medien
    Channeling on boron clusters in silicon (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5032-5037 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Low energy ion implantation at high doses of boron (〉1015 cm−2) in Si is necessary for the fabrication of ultrashallow junctions but can result in the undesirable presence of boron clusters. Values for the dimensions of the lattice distortions in the implanted Si are obtained by comparing the enhanced dechanneling and the direct scattering peak in the region with clusters in a channeled Rutherford backscattering spectrometry spectrum to those from Monte Carlo calculations on a curved crystal structure. Values of about 0.17 and 65 nm are found for the maximum deformation and the length of the distortions in the crystal, respectively, which implies that the lattice distortions extend significantly outside the layer in which the B clusters are supposed to be present. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1406968
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  • 5
    Digitale Medien
    Digitale Medien
    A mass spectrometer system for analysis of polar stratospheric aerosols (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 446-452 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A balloon-borne mass spectrometer system has been flown successfully to determine the chemical composition of polar stratospheric aerosols over northern Scandinavia. The experiment combines an aerodynamic lens which collimates the aerosols into a narrow beam, a small sphere in which they evaporate, and a mass spectrometer for gas analysis. High-speed differential pumping by two liquid helium pumps effectively lowers the presence of ambient gases without affecting the particles of the beam. Field measurements and aerosol studies inside a large cryo-chamber have shown that the concept of particle focusing, evaporation and subsequent mass spectrometric gas analysis is a reliable technique to determine the molecular composition of aerosols especially in polar stratospheric clouds. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1430732
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  • 6
    Digitale Medien
    Digitale Medien
    Two-photon excited photon echo in CdS (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 4181-4183 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Time-resolved and integrated degenerated four-wave mixing experiments with two-photon excitation at a wavelength of 600–710 nm on a 30–40 μm thick cadmium sulfide crystal are presented for a temperature range from 5 to 300 K. A photon echo is observed showing quantum beats both at positive and negative delay times τ with a period of 0.7–0.8 ps. The signal decays exponentially with time constants of (approximate)170 fs at τ〉0 and half as large at τ〈0, independent of temperature. The results are discussed in terms of the decay of a high-density gas of e–h pairs, excitons and excitonic molecules highly out of equilibrium. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1335847
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  • 7
    Digitale Medien
    Digitale Medien
    Stability of the interface between indium-tin-oxide and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) in polymer light-emitting diodes (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2255-2257 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A cause for degradation of polymer light-emitting diodes is the oxidation of the polymer by oxygen diffusing out of the indium-tin-oxide (ITO) anode. This problem can be solved by the introduction of an organic hole-injecting film, poly-(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS), between the ITO and the emissive polymer. Indeed, a dramatic improvement of the lifetime and also the luminous efficiency has been observed. However, our Rutherford backscattering (RBS) studies show that the ITO/PEDOT:PSS interface is not stable. In as prepared glass/ITO/PEDOT:PSS samples 0.02 at. % indium was found in the PEDOT:PSS film. Annealing in a nitrogen atmosphere at 100 °C during 2500 h increased the indium concentration to 0.2 at. %. Upon exposure to air much faster degradation of the ITO/PEDOT:PSS interface was observed; after several days in air the amount of indium reached a saturation concentration of 1.2 at. %. The degradation of the interface can be explained by etching of the ITO due to the strong acidic nature of PEDOT:PSS. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1315344
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  • 8
    Digitale Medien
    Digitale Medien
    Direct-Write Fabrication of Zinc Oxide Varistors (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Zinc oxide (ZnO)-based pastes with tailored rheological properties have been developed for direct-write fabrication of thick-film varistor elements in highly integrated, multifunctional electroceramic devices. Such pastes exhibited pseudoplastic behavior with a low shear apparent viscosity of roughly 1 × 104 Pa·s. Upon aging, the pastes attained printable, steady-state viscosities of approximately 3 × 102 Pa·s at 10 s−1. Square and rectangular elements were patterned on dense alumina substrates and sintered at varying temperatures between 800° and 1250°C. Varistor elements fired at 900°C exhibited nonlinearity coefficients (α= 30) that were equivalent to high-density (〉95%) varistors formed by cold isostatic pressing at 100 MPa (15 ksi) of a similar chemically derived powder heat-treated under analogous conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00052.x
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  • 9
    Digitale Medien
    Digitale Medien
    Pressure-Induced Phase Transformation of Controlled-Porosity Pb(Zr0.95Ti0.05)O3 Ceramics (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Chemically prepared Pb(Zr0.95Ti0.05)O3 (PZT 95/5) ceramics were fabricated with a range of different porosity levels, while grain size was held constant, by systematic additions of added organic pore former (Avicel). Use of Avicel in amounts ranging from 0 to 4.0 wt% resulted in fired ceramic densities that ranged from 97.3% to 82.3%. Hydrostatic-pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transformations were substantially more diffuse and occurred at lower hydrostatic pressures with increasing porosity. An ∼12 MPa decrease in hydrostatic transformation pressure per volume percent added porosity was observed. The decrease in transformation pressure with decreasing density was quantitatively consistent with the calculated macroscopic stress required to achieve a specific volumetric macrostrain (0.40%). This strain was equivalent to experimentally measured macrostrain for FE-to-AFE transformation. The macroscopic stress levels were calculated using measured bulk modulus values that decreased from 84 to 46 GPa as density decreased from 97.3% to 82.3%. Good agreement between calculated and measured values of FE-to-AFE transformation stress was obtained for ceramics fired at 1275° and 1345°C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00826.x
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  • 10
    Digitale Medien
    Digitale Medien
    Robocast Pb(Zr0.95Ti0.05)O3 Ceramic Monoliths and Composites (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Maschinenbau , Physik
    Notizen: Robocasting, which is a computer-controlled slurry-deposition technique, was used to fabricate ceramic monoliths and composites of chemically prepared Pb(Zr0.95Ti0.05)O3 ceramics. The densities and electrical properties of the robocast samples were equivalent to those obtained for cold isostatically pressed parts formed under a pressure of 200 MPa. Three-layer robocast composites that consisted of alternating layers of different sintered densities—93.9%/96.1%/93.9%—were fabricated using different levels of organic pore-former additions. Modification from a single-material to a multiple-material deposition robocaster was essential for the fabrication of composites that could withstand repeated cycles of saturated polarization switching under fields of 30 kV/cm. Furthermore, these composites withstood a poled ferroelectric-to-antiferroelectric phase transformation that was induced by a hydrostatic pressure of 500 MPa, during which strain differences on the order of 0.8% occurred between the composite elements.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00756.x
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