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  • 1
    Electronic Resource
    Electronic Resource
    A microcomputer-based solid-state nuclear track image analyzer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 771-778 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microcomputer-based image processing system has been developed to use with solid-state nuclear track detectors for number counting, area measurement, and location identification. The image digitizer is designed to interface with a microcomputer and a standard black and white TV camera for data acquisition. A spatial dependent segmentation algorithm is proposed for track identification under nonuniform illumination and the low track-pixel population conditions. The system has been tested using Lexan samples irradiated by a Cf-252 spontaneous fission source. The counting accuracy is approximately 3% with a long term stability of 5%. Efficiency calibration was performed using samples with track densities up to 104/mm2. Results indicate that the proposed track identification scheme tends to reduce the track overlap effect and the system behaves as a nonparalyzable counting system. For track densities below 3000/mm2, either a paralyzable or a nonparalyzable counter model can be established with an accuracy better than 0.5%. For track densities below 1500/mm2, the track registration efficiency is in good agreement with manual counting results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141017
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A compact, bipolar, constant–current-voltage source for superconducting junction characterization (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 3822-3824 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile, compact, constant current-voltage, bipolar power source for quasi-static or derivative measurements of the characteristics of superconducting junctions has been developed. The circuitry is based on a negative feedback strategy that is effective in maintaining constant current-voltage behavior at the junction itself and all lead resistances are included in the feedback loop. Constant currents and voltages can be delivered of up to ±0.5 A and ±0.75 V, respectively. Both fast and slow sweeps, as well as a single sweep mode, are available in variable ranges. The single sweep feature is used to avoid heating effects in low resistance junctions which are not in good thermal contact with a thermal reservoir (e.g., liquid 4 He).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140449
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Shubnikov–de Haas effect in thin epitaxial films of gray tin (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2643-2645 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transverse magnetoresistance and Hall effect have been studied for n-type gray tin epilayers grown on (001)CdTe substrates by the molecular beam epitaxy technique. Shubnikov–de Haas oscillations were observed in samples having Hall mobilities ≥104 cm2 /V s at low temperatures. Measurements were carried out using both the dc method and field modulation techniques in the temperature range from 1.2 to 10 K and in magnetic fields up to 10 T. Beat patterns were observed in the Shubnikov–de Haas spectra which we ascribe either to inhomogeneous doping, arising from the diffusion of Cd and Te from the substrate, or to quantization of the motion in the direction parallel to the film normal. The Shubnikov–de Haas carrier concentration of a 1210 A(ring) film was determined to be nSdH =2.3×1017 cm−3, in good agreement with the Hall density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101961
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic hysteresis of p+ and 3He++ irradiated melt-textured YBa2Cu3O7−δ (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4240-4246 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O7−δ samples before and after p+ and 3He++ irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper 3He++ fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence Jc(T,B)=J0(T)/(1+B/B0)n with n=1/2; after the irradiation, the best fit has been achieved by using an exponential form such as Jc(T,B)=J0(T)exp(−B/B0), where B0 is a model dependent parameter. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352236
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  • 5
    Electronic Resource
    Electronic Resource
    Oriented thin films of YBaCu(F)O with high Tc and Jc prepared by electron beam multilayer evaporation (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1573-1575 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of YBaCu(F)O were deposited on SrTiO3(100) substrates by multilayer deposition from three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. The films were later annealed in a separate chamber under a flowing O2-H2O atmosphere. X-ray diffraction studies reveal that the resulting structure is highly oriented with the a axis perpendicular to the substrate. Scanning electron micrographs show a morphology consisting of an array of orthogonal, interconnecting bars with well-developed junctions. High-resolution electron microscopy and electron diffraction patterns show that these junctions are atomically abrupt and that the associated c axes are mutually perpendicular. These epitaxial films show a sharp resistive transition with Tc(R=0) as high as 90 K. The zero field critical current density, determined from magnetization measurements, is 2.9×106 A/cm2 at 4.2 K and 5.0×104 A/cm2 at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101317
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Superconducting YBa2Cu3O7−δ thin films with three different orientations (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4217-4220 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of YBaCuO have been prepared with (1) the a axis perpendicular to (100) SrTiO3 ; (2) the c axis perpendicular to (100) SrTiO3 ; and (3) the [110] axis perpendicular to (110) SrTiO3. Films were fabricated using a multilayer deposition technique involving three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. As deposited films, which contained polycrystalline and amorphous regions, were later annealed in a furnace under a flowing O2-H2 O atmosphere. X-ray diffraction patterns as well as scanning electron microscopy and high-resolution electron microscopy images confirm that the films are highly oriented, essentially epitaxial. The a-axis oriented film exhibits zero resistance at 90 K and a critical current density of 2.9×106 A/cm2 at 4.2 K while the c-axis oriented film exhibits a Tc of 88 K and a Jc of 0.9×107 A/cm2 at 4.2K; the Jc values were determined magnetically. The [110]-orientation film shows the sharpest transition with a transition width of 1 K and zero resistance at 85 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344932
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  • 7
    Electronic Resource
    Electronic Resource
    Structural studies of artificial Si/Nb superlattice films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5360-5366 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Amorphous Si/Nb superlattices with modulation wavelengths ranging from 20–200 A(ring) have been grown on sapphire substrates at 100–150 °C by dual e-beam evaporation in an ultra-high-vacuum (UHV) system. The low-angle x-ray diffraction data can be accounted for by a symmetric trapezoidal composition profile model. The intermixing at the layer interfaces is estimated to be 6–12 A(ring), depending on the substrate temperatures. In the film growth direction, the coherent domain size of the polycrystalline Nb layers scales with the Nb layer thickness. High-resolution transmission electron microscopy reveals the existence of microcrystallites in the 20-A(ring)-thick amorphous Nb layers; also resolved are the microstructure of the substrate/superlattice and superlattice/thick-Nb layer interfaces. In addition, Auger depth profiling results are also consistent with the expected composition modulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343730
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetization of sinter-forged YBa2Cu3O7−δ (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1376-1378 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization and critical magnetization current densities of sinter-forged YBa2Cu3O7−δ samples of nearly theoretical density have been studied. The magnetization curves can be well fitted by Kim's critical state equation Jc(B)=α/(B0+B) with a flat plate geometry. The results revealed an anisotropy in the lower critical field and the critical current density with respect to the forging axis. The deduced critical current density in the favorable direction is larger than the value of isotropic polycrystalline samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99000
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation of Y-Ba-Cu-O thin films on MgO by dc magnetron sputtering from a stoichiometric Y1Ba2Cu3O7−δ target (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1194-1196 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Y-Ba-Cu-O thin films have been deposited on MgO substrates by dc magnetron sputtering from a stoichiometric YBa2Cu3O7−δ target, after which they are subjected to a short heat treatment. Zero resistance is routinely achieved near 60 K, and one film shows zero resistance at 68.0 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98730
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  • 10
    Electronic Resource
    Electronic Resource
    Transport properties in n-type InSb films grown by metalorganic chemical vapor deposition (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 964-966 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the temperature and magnetic field dependence of the Hall mobility and transverse magnetoresistance in n-type InSb films epitaxially grown on GaAs substrates by metalorganic chemical vapor deposition. The films show a giant magnetoresistance: e.g., at 240 K the resistivity increases over 20 times at a magnetic field of 5 T; the low field coefficient of resistivity at 77 K is as high as 47.5 μΩ cm/G. The Hall mobility decreases with magnetic field and saturates at higher fields. By taking the interface carrier transport into account, the observed field dependence of the Hall mobility and magnetoresistance may be understood based on a two-layer model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109859
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