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  • 1990-1994  (180)
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  • 1
    Schriftenreihen ausleihbar
    Schriftenreihen ausleihbar
    Leipzig : Dt. Verl. für Grundstoffindustrie
    Dazugehörige Bände
    Signatur: S 99.0015(452)
    In: Paläontologie, Stratigraphie, Fazies
    In: Freiberger Forschungshefte
    Materialart: Schriftenreihen ausleihbar
    Seiten: 162 S.
    ISBN: 3342009675
    Serie: 452 : Geowissenschaften, Paläontologie
    Sprache: Deutsch
    Standort: Kompaktmagazin unten
    Zweigbibliothek: GFZ Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Schriftenreihen ausleihbar
    Schriftenreihen ausleihbar
    Leipzig : Dt. Verl. für Grundstoffindustrie
    Dazugehörige Bände
    Signatur: S 99.0015(450)
    In: Paläontologie, Stratigraphie, Fazies
    In: Freiberger Forschungshefte
    Materialart: Schriftenreihen ausleihbar
    Seiten: 160 S.
    ISBN: 3342009659
    Serie: 450 : Geowissenschaften, Paläontologie
    Sprache: Deutsch
    Standort: Kompaktmagazin unten
    Zweigbibliothek: GFZ Bibliothek
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2230-2233 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The upper critical field of YBa2(Cu1−xFex)3O7−δ with x=0 and 0.05 is determined over the whole temperature range from 4.2 K to Tc. The data behave according to the theory of Werthamer, Helfand, and Hohenberg [N. R. Werthamer, E. Helfand, and P. C. Hohenberg, Phys. Rev. 147, 295 (1966)]. However, at low temperatures the upper critical field is larger than expected from the original expressions of Werthamer and co-workers. Generalized equations, which take into account the anisotropy of the Fermi surface, yield values for the upper critical field, which are in excellent agreement with the experimental data.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1276-1280 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present the first in situ measurement of the evolution of strain fields due to oxygen precipitation in silicon single crystals by means of high-resolution neutron backscattering. The integrated reflecting power R and the lattice parameter variations Δd/d which are directly related to the strain fields have been measured as a function of temperature and annealing time. In the temperature range from 300 to 1185 K, high purity float zone crystals maintain the R-values characteristic for perfect crystals. In contrast, Czochralski-grown crystals which contain on the order of 1018 oxygen atoms cm−3 (20 ppm), show a steep increase in reflectivity starting at 1160 K, and which goes through a maximum at 1350 K. At 1456 K, partial annealing occurs with a time constant of several hours.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2176-2180 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The crystal-field splittings recently observed in the Er-related optical absorption spectra of ErAs films grown on GaAs by molecular-beam epitaxy are further investigated with respect to their applicability in characterizing strain accommodation in ErAs/GaAs multilayer structures. Rutherford backscattering axial channeling measurements are used to directly assess strain accommodation in the epitaxial films. The crystal-field splittings observed in room-temperature absorption spectra of samples containing thick strain-relieved ErAs layers are consistent with the cubic (Oh) symmetry expected for the Er lattice site in unstrained ErAs. In sharp contrast, a multilayer structure containing two-monolayer-thick, coherently strained ErAs layers shows pronounced changes in the energies, linewidths, and relative intensities of the crystal-field-split spectral lines, as well as the appearance of additional weak absorption lines. This behavior is attributed to strain-induced distortion of the crystal field in which the rare-earth ions reside. The relative influence of hydrostatic and uniaxial strain components on the optical spectra is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3680-3684 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A three-crystal diffractometer for synchrotron radiation with energies of 100 keV and higher has been used in a nondispersive setting to map out the distribution of Bragg scattered intensity in the scattering plane with very high resolution. By using perfect silicon crystals in symmetrical Laue geometry for reflection 220 as monochromator and analyzer, respectively, a resolution of ≈2×10−4 A(ring)−1 in the direction parallel to the reciprocal lattice vector G220 and of ≈10−5 A(ring)−1 in the direction perpendicular to G220 has been achieved at high counting rates. As a first example the mosaic structure of a plastically deformed silicon crystal has been characterized with respect to its mosaic distribution and lattice parameter fluctuations. Second, the study of a silicon-germanium gradient crystal, produced by means of the chemical vapor deposition technique, demonstrated that the substrate peak could be well separated from the intensity distribution of the gradient crystal. A two-dimensional contour plot of the intensity distribution in the vicinity of 220 shows the variation of the lattice parameters in the gradient crystal, as well as the lattice plane tilts of the substrate and the silicon-germanium layers.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In the past γ-ray Compton scattering experiments proved their value for the investigation of many-body effects in the electronic structure of solids by measuring the projection of the electron momentum density onto the scattering vector, the so-called Compton profile. Due to the availability of modern synchrotron radiation facilities the momentum resolution of the technique was improved substantially and, by using circular polarized photons, "magnetic'' Compton profiles could be determined in ferromagnetic materials. A new approach, where the Compton scattered photon is measured in coincidence with the recoiling electron, allows for a direct determination of electron momentum densities in solids. This (γ,eγ) scattering technique will reach its full potential once synchrotron radiation from undulators in electron storage rings operating at energies above 10 GeV will be available.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2307-2313 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Using optical spectroscopy we study the spatial and temporal distributions of the Hα, Cs i(4555 A(ring)), Cs ii(4604 A(ring)), and Mo i(3903 A(ring)) emission lines in a Penning surface-plasma source (SPS). A diagnostic slit exposes the entire SPS discharge gap either parallel or perpendicular to the magnetic field. The spatial and temporal distributions of the emitting species are recorded using a 1-m monochromator. In addition, the visible light and the Hα and Cs ii(4604 A(ring)) spatial distributions are recorded with a video camera. The cesium atomic and ionic light, and the molybdenum atomic light, is strongly concentrated near the cathodes; the visible light and the Hα light is almost uniform in both directions. Electron-impact ionization of atoms sputtered from the cathodes and the return of the ions to the cathodes by residual plasma fields is probably the mechanism which concentrates cesium near the cathodes. The Cs0 mean free path is estimated to be 16 and 0.43 mm for 2 and 400 A discharges, respectively.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1176-1178 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: After developing a pulsed 8X source for H− beams, we are now testing a cooled, dc version. The design dc power density on the cathode surface is 900 W/cm2, much higher than achieved in any previously reported Penning surface-plasma source. The source is designed to accommodate dc arc power levels up to 30 kW by cooling the electrode surfaces with pressurized, hot water. After striking the arc using a 600-V pulser, a 350-V dc power supply is switched in to sustain the 100-V discharge. Now our tests are concentrating on arc pulse lengths ≤1 s. Ultimately, the discharge will be operated dc. The source is described and the initial arc test results are presented.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 2890-2893 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We present a new method for measuring time-resolved photoluminescence on a time scale of microseconds and milliseconds using correlational analysis, and we demonstrate it to work on porous silicon and GaP:Fe. We modulate the pumping laser with a pseudorandom binary sequence which yields correlational properties similar to white noise. The photoluminescence decay is computed via cross correlation of the detector signal with the pumping sequence. The presented method is highly sensitive, simple in application, and inexpensive.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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