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  • Artikel: DFG Deutsche Nationallizenzen  (47)
  • 1
    Digitale Medien
    Digitale Medien
    Cluster motion on metals: Ir on Ir(111) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6535-6536 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Diffusivities have for the first time been quantitatively measured for two-dimensional clusters of iridium atoms on a metal surface, Ir(111). As cluster size increases from two to seven atoms, the diffusivity generally diminishes, but tetramers are an exception. It is shown that their high mobility comes about because of weak interatomic binding, and a low activation energy for diffusion, rather than from a change in the mechanism of motion, which involves displacements of individual adatoms independent of cluster size.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457658
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  • 2
    Digitale Medien
    Digitale Medien
    Atomic jump lengths in surface diffusion: Re, Mo, Ir, and Rh on W(211) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5087-5096 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Measurements with the field ion microscope have been made of the distribution function governing the displacements of a single metal atom diffusing on W(211). It is shown that by comparing such measurements with the predictions of random walk models, the contributions of jumps of different lengths to the overall diffusion can be ascertained, even if diffusion is dominated by transitions between adjacent sites. Extensive observations for rhenium, as well as for molybdenum atoms on W(211) are best represented by a symmetric random walk between nearest-neighbor sites, without any contribution from longer jumps. For iridium and rhodium atoms, however, double jumps do appear to participate in the diffusion, but amount to only ≈3% of the total.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457600
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  • 3
    Digitale Medien
    Digitale Medien
    Electrical and optical properties of beryllium-implanted Mg-doped GaN (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1881-1887 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We investigated the electrical and optical characteristics of beryllium implanted Mg-doped GaN materials. The Mg-doped GaN samples were grown by metalorganic chemical vapor deposition system and implanted with Be ions at two different energies of 50 and 150 keV and two different doses of about 1013 and 1014 cm−2. The implanted samples were subsequently rapidly thermal annealed at 900, 1000, and 1100 °C for various periods. The annealed samples showed an increase of hole concentration by three orders of magnitude from nonimplanted value of 5.5×1016 to 8.1×1019 cm−3 as obtained by Hall measurement. The high hole concentration samples also showed low specific resistance ohmic contact of about 10−3 Ω cm2 and 10−6 Ω cm2 using Ni/Au and Ni/Pd/Au metallization, respectively, without any further annealing process. It is also found from the temperature dependent photoluminescence that the activation energy of Mg dopants of the Be implanted samples has an estimated value of about 170 meV, which is nearly 30% lower than the as-grown samples of about 250 meV. The crystal quality and surface morphology of the Be implanted samples measured by x-ray diffraction and atomic force microscopy show no obvious degradation in the crystal quality and surface morphology. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1494110
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  • 4
    Digitale Medien
    Digitale Medien
    Atom condensation on an atomically smooth surface: Ir, Re, W, and Pd on Ir(111) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4071-4074 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The distribution of condensing metal atoms over the two types of sites present on an atomically smooth Ir(111) has been measured in a field ion microscope. For Ir, Re, W, and Pd from a thermal source, condensing on Ir(111) at ≈20 K, the atoms are randomly distributed, as expected if they condense at the first site struck.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460657
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  • 5
    Digitale Medien
    Digitale Medien
    The Synthesis of DL-Aspartic Acid-4-C14 1 (1951)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 73 (1951), S. 2390-2390 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja01149a546
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  • 6
    Digitale Medien
    Digitale Medien
    The Synthesis of Thyroxine-1-C14 1 (1952)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 74 (1952), S. 2445-2445 
    Details
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ja01129a538
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  • 7
    Digitale Medien
    Digitale Medien
    Low-threshold operation of a GaAs single quantum well mushroom structure surface-emitting laser (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1780-1782 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Room-temperature continuous-wave (cw) lasing operation with a threshold current (Ith) of 3 mA and a pulsed Ith as low as 1.5 mA were achieved in mushroom structure surface- emitting lasers utilizing a 300 A(ring) GaAs single quantum well as an active layer and an AlAs/Al0.1Ga0.9As multilayer as the top and the bottom distributed Bragg reflectors. A series resistance of 250 Ω was obtained on devices with an 8×8 μm2 active region using selective zinc diffusion. A differential quantum efficiency of 12%–20% and a maximum cw light output power exceeding 1 mW were achieved. The emission wavelength was 860 nm with a spectral linewidth of ∼0.5 A(ring).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105089
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  • 8
    Digitale Medien
    Digitale Medien
    5 GHz modulation of a mushroom mesa surface emitting laser (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1147-1149 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A modulation bandwidth approaching 5 GHz in a GaAs quantum well vertical cavity surface emitting laser with a mushroom mesa structure is reported. The modulation speed and the maximum power of 1.5 mW were limited by device heating. The second harmonic distortion as a function of frequency was measured at an injection current twice threshold and an optical modulation index of 10%, and a peak distortion of about −25 dBc was obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105539
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  • 9
    Digitale Medien
    Digitale Medien
    Submilliampere continuous-wave room-temperature lasing operation of a GaAs mushroom structure surface-emitting laser (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1839-1840 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report a GaAs mushroom structure surface-emitting laser at 900 nm with submilliampere (0.2–0.5 mA) threshold under room-temperature cw operation for the first time. The very low threshold current was achieved on devices which consisted of a 2–4 μm diameter active region formed by chemical selective etching, and sandwiched between two Al0.05Ga0.95 As/ Al0.53Ga0.47 As distributed Bragg reflectors of very high reflectivity (98–99%) grown by metalorganic chemical vapor deposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103063
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  • 10
    Digitale Medien
    Digitale Medien
    Semiconductor waveguide phase comparator (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1297-1298 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A phase comparator based on two cascaded semiconductor electroabsorption waveguide modulators is demonstrated for the first time. The operation principle of this device is derived and experimentally confirmed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.100002
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