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  • 1995-1999  (7)
  • 1995  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Poly(p-phenylene vinylene)/tris(8-hydroxy) quinoline aluminum heterostructure light emitting diode (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 653-655 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are presented from polymer/molecular organic heterostructure light emitting diodes composed of a layer of the conjugated conducting polymer poly(p-phenylene vinylene) (PPV), and a layer of fluorescent molecular compound tris(8-hydroxy) quinoline aluminum (Alq). The external quantum efficiency of these heterostructure LEDs is ∼0.1%, which is over one order of magnitude higher than that of simple PPV LEDs. The electroluminescence (EL) spectra indicate that both materials in the device emit comparable amounts of light. The dependence of the EL spectra on the layer thicknesses and its independence on bias suggest that neutral excitons are formed in the Alq, far from the PPV/Alq interface, and subsequently diffuse into the PPV layer. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114119
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Tunable, long-wavelength PtSi/SiGe/Si Schottky diode infrared detectors (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 506-508 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated p-type PtSi/SiGe/Si Schottky diodes with barrier heights (from photoresponse) that are lowered (relative to PtSi/Si) and highly dependent on the applied bias. The variability in the barrier height is obtained by using the SiGe/Si valence band offset as an additional barrier. When placed in close proximity to the PtSi/SiGe Schottky barrier, the total effective barrier can be altered dramatically by adjusting the applied reverse bias. The voltage sensitivity of the total barrier height can be controlled by the SiGe layer thickness. The voltage-variable barrier heights range, for example, from 0.30 eV at zero bias to 0.12 eV at 2.4 V reverse bias for a 20%, 450 A(ring) thick SiGe layer. This lowest barrier height corresponds to a cutoff wavelength of 10 μm, extending the detection range of PtSi infrared detectors to the long-wavelength range. The quantum efficiency coefficients C1 are normal at this long-wavelength end, but reduced over the rest of the tunable range, because hot carriers have to traverse the entire SiGe thickness in order to be detected. The hot carriers' energy losses from quasielastic scattering in the SiGe are taken into account in a theoretical model that gives good agreement with data. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114551
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Defect-free band-edge photoluminescence and band gap measurement of pseudomorphic Si1−x−yGexCy alloy layers on Si (100) (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3915-3917 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic Si1−x−yGexCy alloy layers on Si (100) with band-edge photoluminescence and without defect-related luminescence have been achieved. The photoluminescence was measured from 2 to 77 K and was used to make a direct measurement of the band gap shift as a function of strain reduction as C was added. Compared to the effect of just reducing Ge content, results show that as C is added, strain is reduced more efficiently than the band gap is increased. Furthermore, results imply that a fully strain-compensated Si1−x−yGexCy layer on Si (100) would have a band gap much less than that of Si, and suggest that initial C incorporation reduces the band gap of relaxed, unstrained Si1−x−yGexCy alloys. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115316
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric and optical properties of C60 material studied by ellipsometry and quantitative IR and UV/VIS spectroscopy (1995)
    Springer
    Applied physics 61 (1995), S. 163-170 
    Details
    ISSN: 1432-0630
    Keywords: 78.40 ; 78.30 ; 73.60 ; 78.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Optical properties in the spectral range from 0.06 to 5.5 eV of fullerite films on different substrates, C60 powder, and dissolved fullerene material are investigated by spectroscopic ellipsometry and optical transmission and reflection measurements. Depolarization effects are taken into account during determination of the dielectric function of fullerite films by ellipsometry. The optical gap for C60 films is found to be 1.63 eV. Three optical absorption bands are observed at 2.69, 3.53, and 4.49 eV. The dielectric function in the infrared shows the four characteristic infrared vibrational modes. The interference pattern seen in UV/VIS reflection measurements are used for high-precision thickness determination of the films. The Clausius-Mossotti formula is successfully applied to reproduce the experimental optical data measured in C60/dichlormethane solutions. Deviations between theory and experiments provide interesting information about the intermolecular interaction of the C60 molecules. A tentative interpretation of the measured absorption bands is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538384
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Dielectric and optical properties of C60 material studied by ellipsometry and quantitative IR and UV/VIS spectroscopy (1995)
    Springer
    Applied physics 61 (1995), S. 163-170 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 78.40; 78.30; 73.60; 78.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Optical properties in the spectral range from 0.06 to 5.5 eV of fullerite films on different substrates, C60 powder, and dissolved fullerene material are investigated by spectroscopic ellipsometry and optical transmission and reflection measurements. Depolarization effects are taken into account during determination of the dielectric function of fullerite films by ellipsometry. The optical gap for C60 films is found to be 1.63 eV. Three optical absorption bands are observed at 2.69, 3.53, and 4.49 eV. The dielectric function in the infrared shows the four characteristic infrared vibrational modes. The interference pattern seen in UV/VIS reflection measurements are used for high-precision thickness determination of the films. The Clausius-Mossotti formula is successfully applied to reproduce the experimental optical data measured in C60/dichlormethane solutions. Deviations between theory and experiments provide interesting information about the intermolecular interaction of the C60 molecules. A tentative interpretation of the measured absorption bands is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050185
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical simulation of the temperature dependence of photoluminescence in strained-Si1−xGex/Si heterostructures (1995)
    Springer
    Journal of materials science 6 (1995), S. 350-355 
    Details
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In previous work it has been shown that the decay in photoluminescence from Si/strained-Si1−xGex/Si quantum wells at temperatures over 100 K is controlled by surface recombination and that the photoluminescence intensity can be increased by over an order of magnitude by surface passivation. These results had been explained only by a simple phenomenological model, which could not explain why at high pump power density the observed luminescence was constant from 77 to 250 K. This paper uses a two-carrier heterojunction device simulator to determine the carrier profiles during optical pumping. The profiles are used to understand quantitatively luminescence as a function of temperature and pump power density without making the over-simplifying assumptions required for analytical modeling. Surface recombination velocities over 103 cm/s drastically affect the results, and Auger recombination plays an important role at high pump power density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125891
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Potential reduction method for harmonically convex programming (1995)
    Springer
    Journal of optimization theory and applications 84 (1995), S. 181-205 
    Details
    ISSN: 1573-2878
    Keywords: Convex programming ; harmonic convexity ; potential reduction methods ; polynomiality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we introduce a potential reduction method for harmonically convex programming. We show that, if the objective function and them constraint functions are allk-harmonically convex in the feasible set, then the number of iterations needed to find an ε-optimal solution is bounded by a polynomial inm, k, and log(1/ε). The method requires either the optimal objective value of the problem or an upper bound of the harmonic constantk as a working parameter. Moreover, we discuss the relation between the harmonic convexity condition used in this paper and some other convexity and smoothness conditions used in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02191742
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