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  • Artikel: DFG Deutsche Nationallizenzen  (260)
  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 84 (1980), S. 1206-1211 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of organic chemistry 57 (1992), S. 6687-6689 
    ISSN: 1520-6904
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 400-406 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The critical points of (AlxGa1−x)0.5In0.5P semiconductor alloys grown by metal-organic chemical vapor deposition and lattice matched to GaAs have been measured at room temperature in the 1.5–6.2 eV spectral region using spectroscopic ellipsometry. We have performed standard lineshape analysis of the second derivatives of pseudodielectric function data to obtain the standard critical point parameters (peak position, broadening parameter, amplitude, and excitonic phase angle) as a function of x. The properties of the E1 and the E1+Δ1 spectral structures have been observed for the first time. The anomalously small amplitude of the contribution of E1+Δ1 spectral feature relative to that of E1 is attributed to the k-linear interaction between the Λ4,5v and Λ6v valence bands, which is large in III-P alloys due to the very small spin-orbit splitting. The bowing parameter of Δ1 is determined and discussed. The critical point parameters smoothly interpolate between those of the two ternary endpoints, Ga0.5In0.5P and Al0.5In0.5P. These parameters are discussed and compared with those of AlxGa1−xAs, (AlxGa1−x)0.5In0.5As/InP, and InxGa1−xAsyP1−y /InP.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 4901-4905 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Steady-state beam coupling is used to measure the concentration of empty traps, the sign of the dominant photocarrier, and the effective electro-optic coefficient in seven crystals of BaTiO3. The measured value of the effective electro-optic coefficient gives the product of the fractional poling of the crystal, the relative conductivity of the crystal, and the electro-optic coefficient. Anomalously low beam coupling gain measured in an eighth crystal suggests that this crystal is nearly perfectly compensated; i.e., the photoconductivities due to electrons and holes are nearly equal.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1245-1250 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have investigated by reflectance anisotropy spectroscopy the arsenic desorption from GaAs (001) at various temperatures in metal–organic vapor-phase epitaxy to obtain reaction orders and activation energies. The highest arsenic coverage, found at low temperatures with arsine stabilization, corresponds to a (4×3) reconstruction. Without arsine, arsenic starts to desorb and less arsenic-rich reconstructions are observed, depending on temperature: c(4×4) (below 800 K), β2(2×4) (below 920 K), α(2×4), and only with hydrogen carrier gas finally (4×2) (above 950 K). Above 920 K the reaction order differs in hydrogen and nitrogen atmosphere, probably due to an etching effect of hydrogen radicals. The five different desorption processes show either a first- or zero-order time dependence. First order is related to the desorption from the terraces and zero order to desorption from the steps (or kinks) on the surfaces. The activation energies for all processes are around 2.5 eV. This energy is, therefore, assumed to be the activation energy for the removal of an arsenic dimer from the surface. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 2015-2018 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We present a very efficient 90° sector magnet mass spectrometer detector, based on electron impact ionization, especially adapted for the use with atomic and molecular beams. In this setup, a cylindrically symmetric magnetic field compresses electrons emitted from a large filament into a long, narrow volume containing primarily the molecular beam. This has the advantage of both producing as little as possible background from residual gases and increasing the interaction region between beam and ionizer. Experimental tests using thermal He atoms show that the detector's efficiency and sensitivity are very high, amounting to η≥0.70±0.04% and S=0.22±0.03 A mbar−1, respectively. The unconventionally long ionization volume, however, may restrict the use of this mass spectrometer to experiments with no, or only moderate timing requirements. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3099-3103 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A superior lamellae etching drop-off technique is described for the preparation of W tips without the use of CCl4. Sharp tips with an apex of 25 nm or less can be produced routinely. In the case of Pt/Ir wire, the chemical inertness of the material means that it has to be reduced in diameter before being etched to yield a tip. In order to accomplish this, a capillary diameter reduction technique has also been developed for use in combination with the lamellae etching drop-off technique. The apparatus does not require the use of micromanipulators or micromovers. The shapes of tips with apexes as small as 25 nm can be investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This low cost method of producing sharp tips scanning tunneling microscopy is very effective and it would probably be feasible to develop an automatic tip preparation with a little more technical effort. Since it is possible to produce well shaped W tips almost every time after acquiring a little skill, it is not usually necessary to check their shape by TEM or SEM before use. In contrast, the success rate with Pt/Ir tips is only up to 70%, so that it is advisable to check their shapes by TEM. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 91 (1969), S. 7526-7528 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The optical properties of InxGa1−xP/GaAs and InxGa1−xP/graded InGaP/GaP (0.25≤x≤0.8) epitaxial layers have been studied using spectroscopic ellipsometry and Raman spectroscopy. The (E1,E1+Δ1) critical points and the first-order phonon frequencies were determined as a function of In composition. The general behavior of the peak shifts and broadenings of both the E1 gaps and the optical phonons of InxGa1−xP/GaAs can be explained in terms of biaxial strain and strain relaxation caused by lattice-mismatch. The near-cancellation of E1 gap change due to the compensation effect between alloy composition and misfit strain is observed. As misfit strain increases, the E1 gap broadens whereas the phonon line shape does not change. In strain relaxed samples of InxGa1−xP/(GaAs, graded GaP) (0.3≤x≤0.8), the E1 gap linewidth shows upward bowing as a function of In composition.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 951-953 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have observed two-beam coupling gain (0.273 cm−1) that exceeds absorption (0.145 cm−1) in InP:Fe without applying an external field at λ=1.32 μm. Measurements of the gain coefficient as a function of grating spacing fit the photorefractive theory for simultaneous electron-hole transport, with the effective density of traps NE = (3.86 ± 1.1)NE=(3.86±1.1)× 1015 cm−3 and ξ, the factor that accounts for competition between electrons and holes, equaling −0.729±0.026. Absorption measurements, combined with the photoionization cross sections of electrons and holes, confirm these results. The agreement between theory and experiment suggests how to choose impurity concentrations that optimize net gain.
    Materialart: Digitale Medien
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