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  • 11
    Electronic Resource
    Electronic Resource
    Power and magnetic field-induced microwave absorption in Tl-based high Tc superconducting films (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 307-309 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The increase in the microwave surface resistance Rs of high Tc superconductors at elevated microwave power levels is reported for both oriented and unoriented Tl-based films as a function of rf magnetic field at 820 MHz and 18 GHz. The application of dc magnetic fields produces qualitatively similar increases in Rs and in the surface reactance Xs. The increase in Rs with dc field is shown to arise from simple decoupling of grains by intergranular magnetic flux. The increase in Rs with microwave power, on the other hand, is a consequence of hysteretic intergranular processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104670
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  • 12
    Electronic Resource
    Electronic Resource
    Novel far-infrared-photoconductor based on photon-induced interedge channel scattering (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2231-2233 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate experimentally that the far-infrared photoresponse of GaAs/AlGaAs heterostructures at photon energies corresponding to cyclotron resonance absorption is strongly enhanced in the adiabatic transport regime of the quantum Hall effect (QHE). Ideal adiabatic transport is characterized within the edge channel picture of the QHE by the absence of interedge channel scattering. We realize adiabatic transport by the means of a multiple gate finger structure, which is used for a selective population of the edge channels. The cyclotron resonance absorption is interpreted as an additional interchannel scattering process increasing the magnetoresistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104935
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  • 13
    Electronic Resource
    Electronic Resource
    Neutron-induced microwave loss in ceramic YBa2Cu3O7−δ (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2462-2464 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An increase by over three orders of magnitude from 0.58 mΩ to 1.17 Ω was observed at 4.0 K in the 3 GHz microwave surface resistance of ceramic YBa2Cu3O7−δ following exposure to neutrons. The transport resistivity of an unirradiated pellet was linear in temperature down to Tc with a room-temperature value of 2.13 mΩ cm and a resistivity extrapolated to 4.0 K of 0.53 mΩ cm. Following irradiation, the resistivity rose with decreasing temperature from a room-temperature value of 1.5 Ω cm to a maximum at around 45 K with little change evident at Tc . These results, in conjunction with eddy current, susceptibility, iodometric titration, and thermally stimulated luminescence measurements on irradiated and unirradiated samples, collectively suggest that the effect of neutron irradiation has been to decrease intergranular coupling without the development of an insulating phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103256
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  • 14
    Electronic Resource
    Electronic Resource
    Observation of enhanced infrared photoresponse in forward-biased amorphous silicon p-i-n diodes (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 956-957 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photoconductive response of hydrogenated amorphous silicon (a-Si:H) p-i-n diodes has been investigated under conditions of low-temperature operation. We show that cooled p-i-n diodes exhibit an enhanced infrared response when operated under forward bias conditions. The induced IR response is of the order of 10−3A/W, extending out to wavelengths of about 2–3 μm with the long wavelength cutoff being determined by the properties of the glass/indium–tin–oxide entrance window. We propose that the IR photoeffect is due to the re-excitation of band-tail trapped excess carriers injected into the localized conduction and valence band tail states in the vicinity of the n+- and p+-contact regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106313
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  • 15
    Electronic Resource
    Electronic Resource
    Writing electronically active nanometer-scale structures with a scanning tunneling microscope (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2136-2138 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A scanning tunneling microscope (STM) is used to locally modify p-n junctions on a scale of a few tens of nanometers. The p-n junction is composed of a phosphorus-doped, hydrogenated amorphous Si [a-Si:H(P)] layer deposited on heavily doped p-type crystalline Si(111). Under conditions of high current densities, with the p-n junction biased in forward direction, the a-Si:H layer is structurally changed leading to a decrease of the junction barrier height. The resulting exponential increase of hole injection into the modified amorphous layer leads to electronically active structures. They are detected by STM owing to their differing electronic properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106104
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  • 16
    Electronic Resource
    Electronic Resource
    Piezoelectric constant of InP (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 352-353 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The piezoelectric modulus d14 of InP was not determined experimentally up to now. By doping InP with Fe now high compensated bulk material is available by liquid-encapsulated Czochralski crystals with a conductivity lower than 10−8 (Ω cm)−1. Excitation of vibration modes leads to a set of closely spaced resonance lines. These data were used to calculate a set of parameters for an electrical equivalent circuit with which the impedance behavior can be described successfully. From this the piezoelectric modulus of InP was derived to be −1.8 pC/N at room temperature. The sign of the constant was determined by qualitative static measurements of the piezovoltage by compressing the crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109619
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  • 17
    Electronic Resource
    Electronic Resource
    The effective microwave surface impedance of high Tc thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6940-6945 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependence of the effective surface impedance Zeff=Reff+iXeff of superconducting thin films on the film thickness d, on the magnetic field penetration depth λ, and on the dielectric properties of the substrate material is investigated theoretically by means of impedance transformations. It was found that the effective surface resistance Reff can be expressed by RSf(d/λ)+Rtrans where RS is the intrinsic surface resistance of the superconductor. The function f(d/λ) describes the altered current density distribution in the film. Rtrans arises from power transmission through the film. It depends on d and λ as well as on the dielectric properties of the substrate material and is significantly altered in the case of a resonant background. The effective surface reactance Xeff of a superconducting thin film can be expressed by XS cosh(d/λ) where XS=ωμ0λ is the intrinsic surface reactance. Measurements of Zeff at 87 GHz have been performed for YBa2Cu3O7−δ thin films grown epitaxially by laser ablation on SrTiO3, MgO, and LaAlO3. With the best films, Reff (77 K) values of 21 mΩ and RS (77 K) values of 8 mΩ were achieved. The temperature dependence of λ was found to be in good agreement to both weak-coupling BCS theory in the clean limit and the empirical two-fluid model relation with λ (0 K) values ranging from 140 to 170 nm and 205 to 250 nm, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345037
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  • 18
    Electronic Resource
    Electronic Resource
    Quantitative study of the contribution of deep and shallow levels to the compensation mechanisms in annealed InP (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5538-5545 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effects of heat treatment under phosphorus atmosphere on the balance of electronic levels by capacitance-voltage and deep level transient spectroscopy measurements. A series of special samples was annealed under the conditions which we are normally using for the processing of nominally undoped semi-insulating (S.I.) InP. It is shown explicitly that in this annealing process the reduction of the free-carrier concentration is predominantly caused by a reduction of the net concentration of defects related to shallow levels. Furthermore, we have identified in the annealed material two defects related to electron traps with activation energies of 400 and 600 meV, which are created or incorporated during the annealing with limited concentrations of about (0.5–1)×1015 cm−3. On the basis of these results we conclude that for the compensation mechanism in the annealed nominally undoped S.I. InP only a concentration below 1015 cm−3 of defects with a midgap energy level is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354212
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  • 19
    Electronic Resource
    Electronic Resource
    Erratum: "The use of magnetohydrodynamic effects to investigate fluid flow in electrically conducting melts'' [Phys. Fluids A 5, 3280 (1993)] (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 2551-2551 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868450
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  • 20
    Electronic Resource
    Electronic Resource
    The use of magnetohydrodynamic effects to investigate fluid flow in electrically conducting melts (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3280-3289 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A measurement method is introduced which can detect steady and unsteady flow in electrically conducting fluids. In this method, the flow region is subjected to an externally applied weak magnetic field B0. The induced magnetic field b generated by fluid flow across the field lines of B0 is used for the flow investigations. It can be measured outside the flow region with the advantage that neither electrical nor mechanical connections with the fluid are necessary. The results obtained by the experiment are confirmed by a time-dependent three-dimensional numerical simulation. It is indicated how fluid flow configurations could be deduced by an appropriate measurement of the induced field b.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858685
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