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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2570-2573 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The x-ray transmission properties of a very thin polyimide window in the range 7–310 A(ring) have been investigated. The window is nominally 0.24 μm thick and is supported by a hexagonal polyimide grid. Transmission of over 60% and 80% at the oxygen Kα and carbon Kα lines, respectively, have been achieved. The use of such windows as the entrance window of a gas scintillation counter (GSPC) operating as a broadband spectrometer at XUV wavelengths is discussed. Overall detector efficiencies of greater than 10% for wavelengths less than 150 A(ring) are possible to achieve. © 1995 American Institute of Physics.
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2248-2250 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: At the radiometry laboratory of the Physikalisch-Technische Bundesanstalt (PTB) a reflectometer for the soft x-ray spectral region has been operated for several years utilizing monochromatic radiation of a toroidal grating monochromator or a high-resolution plane grating monochromator. The monochromators cover the photon energy region from 35 to 1500 eV. New challenges due to the development of soft x-ray optical components led to the design of a second reflectometer with advanced capabilities. Samples with a diameter of up to 250 mm can be accommodated. The time required for sample exchange is reduced by using a lock chamber. The feasibility of sample positioning with high precision has been improved. Typical uncertainties of about 1%–2%, e.g., for the reflectance of multilayer mirrors, can be achieved. A detailed description of the reflectometer as well as some typical results showing the performance are presented. © 1995 American Institute of Physics.
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  • 13
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3229-3232 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new beamline for radiometric applications (e.g., detector calibration and reflectometry) has been installed and characterized at the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY. The beamline is equipped with a SX700 type plane grating monochromator and a toroidal mirror behind the exit slit of the monochromator for collimating the radiation to allow angle resolved reflectometry. A divergence of 0.1 mrad has been achieved. The beamline has been optimized for high spectral purity of the radiation. Within the photon energy range from 40 to about 1500 eV the total amount of stray light and higher order radiation stays below 1%. A photon flux of up to 1011 s−1 has been measured in the focal point of the toroidal mirror. It corresponds to a radiant power of a few μW and thus allows use of a cryogenic radiometer for detector calibration. The details of the beamline layout and the results of the performance characterization are presented.
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  • 14
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7362-7369 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric and insulating properties of epitaxial SrTiO3(STO) thin film capacitors were studied. The films were grown by inverted cylindrical magnetron sputtering in the radio frequency mode on (100) STO substrates which were covered with a (001)-oriented YBa2Cu3O7−x (YBCO) layer as a ground electrode. As a top electrode we used YBCO or Au thin films. A high dielectric constant, ε, of up to 5000 was observed at T=80 K. The capacitors revealed a large tunability, i.e., a nonlinear ε(E) dependence, with respect to voltage biasing. By applying 3 V, ε decreased to 1000 which was 20% of its maximum value. The frequency dependence of ε, the temperature dependence of the dielectric loss factor, tan δ, and the direct currency conductivity reflected that variable range hopping via localized states was present and dominated the conduction process in the STO films at low temperatures. The field strength for the electrical breakdown amounted to 300 kV/cm even for rather thin films with a thickness of about 40 nm. Below T=90 K, the STO films were ferroelectric with a high polarization of up to 30 μC/cm2 at T=4.2 K. The ferroelectric phase transition was found to be of second order and of the displacive type. © 1999 American Institute of Physics.
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  • 15
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1844-1850 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ti-deficient SrTixO3−δ films, x〈1, were grown on 〈100〉 oriented SrTiO3 single crystal substrates by radio frequency magnetron sputtering from stoichiometric targets. The Ti-deficiency was adjusted by the sputtering gas pressure. The Ti/Sr cation ratio, x, was determined by Rutherford backscattering and energy dispersive x-ray analysis in a scanning electron microscope. To obtain information on the Ti/O ratio, x-ray absorption spectroscopy was carried out as well. We investigated SrTixO3−δ films with x=0.98, 0.95, and 0.89. The epitaxial growth and lattice imperfections were characterized by x-ray diffraction, electron diffraction, and high resolution transmission electron microscopy. The films crystallized in a tetragonal structure with a maximum mosaic spread of about 0.1°. The c axis was oriented perpendicular to the substrate surface where the c-lattice parameter was increasing with decreasing x. For x〉0.89, the Ti deficiency was primarily compensated by a change of the site occupation on the cation sublattices in combination with oxygen vacancies, i.e., the formation of SrTi and VO point defects, whereas for x〈0.95 the intergrowth of homologs series of the Ruddlesden–Popper phases, Srn+1TinO3n+1, was observed. The dielectric properties of the films are briefly discussed in terms of (SrTiVO) defect complexes. © 2000 American Institute of Physics.
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5288-5295 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dielectric LaAlO3 and SrTiO3 thin films and LaAlO3/SrTiO3 multilayers were grown epitaxially by pulsed laser deposition on (001) oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates. Their structural characterization was carried out by x-ray diffraction and cross section transmission electron microscopy, which allowed us to determine the degree of strain in the dielectric material. For a film thickness of 200 nm we observed significant structural relaxation of the LaAlO3 and SrTiO3 single layers toward their single crystal lattice parameters in contrast to LaAlO3/SrTiO3 multilayer structures, where the dielectric material remained coherently strained. The influence of strain on the dielectric properties was studied by impedance spectroscopy in the frequency range of 40 Hz–10 MHz at room temperature. The measurements were performed on parallel plate capacitors, using epitaxial La0.4Sr0.6CoO3 films as bottom and top electrodes. The dielectric constant ε of partially relaxed and coherently strained material was nearly the same. However, the dielectric tunability, i.e., the influence of a direct current bias voltage on ε, was found to be significantly larger for coherently strained dielectrics. For [LaAlO3(30 Å)/SrTiO3(60 Å)]20 multilayers we observed a tunability of nearly 20% at room temperature for a bias voltage of only 1 V, corresponding to an electric field strength of 50 kV/cm. The total dielectric loss of the multilayer capacitors is below 1% for frequencies above 1 MHz and depends only slightly on the bias voltage. © 2002 American Institute of Physics.
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  • 17
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 733-735 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Transverse spin lifetimes of spin-polarized photogenerated carriers in InAs self-assembled quantum dots are extracted from the depolarization of their photoluminescence in a magnetic field perpendicular to the spin (the Hanle effect). Hanle measurements on a series of samples reveal that the dot dimensions influence the spin lifetime and its dependence on temperature. The spin lifetime as a function of excitation intensity is qualitatively distinct for carrier spins created in the GaAs host as compared to in the InAs wetting layer. © 2001 American Institute of Physics.
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  • 18
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 290 (1990), S. 606-612 
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 19
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 345 (1994), S. 549-560 
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 20
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Molecular Cell Research 1012 (1989), S. 140-147 
    ISSN: 0167-4889
    Keywords: (Human cell culture) ; Indoleamine ; Interferon ; Tryptophan metabolism ; Tumor cell line
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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