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  • American Institute of Physics (AIP)  (26)
  • Oxford University Press  (20)
  • American Physical Society (APS)  (11)
  • Wiley  (3)
  • Cambridge University Press
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6536-6538 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Following a method proposed by Divin and Modovets [Sov. Tech. Phys. Lett. 9, 108 (1983)], we have measured at millimeter waveband the intrinsic noise temperatures TN of YBa2Cu3O7−δ Josephson junctions or dc superconducting quantum interference devices (SQUIDs) fabricated on SrTiO3, yttria-stabilized ZrO2, or Si bicrystal substrates. Over wide ranges of physical temperatures TP and the junction's normal resistance RN, it was found that TN follows TP pretty well. This indicates that the intrinsic noise in the devices is dominated by Johnson noise. TN was also measured in cases where there is external magnetic field applied, or where there is another microwave radiation like the local oscillator in a mixer. The magnetic field or microwave radiation does not seem to affect TN in any appreciable way. To estimate the high frequency performance of the junctions on Si bicrystal substrates, direct irradiation by a far infrared laser at 1.81 THz is carried out and the clear first Shapiro step is observed. © 1996 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4977-4979 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magneto-optical Kerr spectra of ultrathin Co films grown on Cu(001) surfaces have been measured in situ. The growth mode and the crystal structure have been investigating by reflection high-energy electron diffraction observation. A 20-A(ring)-thick fcc Co grown on Cu(001) had a lateral lattice constant of 3.59±0.01 A(ring), which was about 1.4% expanded compared with that of the bulk fcc Co. There was a remarkable difference above 4 eV in ωσyz spectra between 20- and 1000-A(ring)-thick films. ωσyz spectra for 20-A(ring)-thick Co film showed a resonance-type structure at around 5 eV. It is considered that the structure is caused by the lower energy shift of the 1→6 interband transitions due to the narrowing of the 3d bands. © 1996 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1895-1898 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied low frequency (1/f) noise of YBa2Cu3O7−δ dc superconducting quantum interference devices (SQUIDs) on SrTiO3 bicrystal substrates. 1/f flux noise, either measured at different temperatures for optimized bias current or measured at 77 K for different bias currents, is almost constant. These facts imply that 1/f noise mainly comes from fluctuations of the critical current of the Josephson junction that form the SQUID. Also, we explain the critical current fluctuations in the junction by an equilibrium temperature fluctuation model.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 949-955 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present experimental results on elementary phase-mode Josephson circuits whose combinations enable us to construct a total data processing system which is expected to be superior to the ordinary voltage-mode Josephson computer in several respects. In the phase-mode system a device depends for its operation on the existence of many stable states differing from one another by integer multiples of 2π in the phase plane. The total system is considered to be a prototype of quantum computer systems where physical quantum states are employed as logic states of information processing. By using the fabricated elementary circuits composed of SQUIDs and two types of branching points we have experimentally confirmed and, fan-out, fan-in operations, etc. We have also proposed an inhibit circuit, and presented the experimental results on the inhibit circuit.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 1961-1963 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Admittance spectroscopy is applied to the analysis of the thermal properties of the Mn acceptor-doped InP grown by liquid-phase epitaxy. The thermal activation energy and capture cross section are determined as ΔET=183 meV and σp=1.8×10−13 cm2, respectively. The cutoff frequency of the emission of holes from the Mn acceptor is 1 GHz at 300 K. It is shown that the small signal frequency characteristic of a buried heterostructure laser is improved at frequencies f〉1 GHz by using the Mn-doped p-InP layer for the current blocking region.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3786-3788 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current waveforms of the self-resetting oscillation in a dc superconducting quantum interference device (SQUID) are observed by means of a Josephson sampling system. The frequency of the oscillation is around 60 GHz. The time period of the self-resetting oscillation is experimentally measured as a function of the bias current to the SQUID. Theoretical and numerical analyses are presented for the self-resetting oscillation in the dc SQUID.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3740-3744 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using c-axis-oriented oxygen-deficient YBa2Cu3O7−δ film deposited across a low-angle step on a SrTiO3 substrate, we successfully demonstrated intrinsic Josephson effects. In addition to several voltage jumps of large amplitudes (a few millivolts) and remarkable hysteresis on the dc current–voltage curves, we observed upturns on the current–voltage curves under microwave irradiation which appeared at increasingly high voltages with increasing microwave power. We proposed to explain this observation in terms of high-order microwave-induced Shapiro steps. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6064-6066 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimum junction resistance and minimum tunnel magnetoresistance (TMR) ratio required for high density and high performance magnetoresistive random access memory (MRAM) devices with a TMR cell plus field effect transistor (FET) switch architecture are discussed by taking into account the variation of FET resistance causing noise. This implies that a TMR ratio over 25% at a 400 mV bias voltage and junction resistance of several tens of kilo-ohms for TMR cells are required with a signal voltage of 30 mV and a sense current of 10 μA, which leads to about 10 ns read time. This large magnetoresistance ratio at the elevated bias voltage requires low bias voltage dependence of TMR for the MRAM devices. In order to try to meet this requirement, double tunnel junctions were fabricated which possess the central ferromagnetic layer consisting of a thin discontinuous layer of hard ferromagnetic Co80Pt20 nanoparticles and insulating Al2O3 prepared by alternate sputtering of Co80Pt20 and Al2O3 targets. The maximum TMR obtained was 20.5% at room temperature for FeCo top and bottom electrodes without annealing. Bias voltage dependence of the (NiFe/CoFe)/1.5 nm Al2O3/discontinuous CoPt/2.6 nm Al2O3/(CoFe/NiFe) double tunnel junctions were revealed to be small compared to that of single junctions, the barrier of which was also fabricated by sputtering of an Al2O3 target. © 2000 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3933-3936 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectral dependence of the photoionization cross section of Fe doped in InP is determined by photocapacitance spectroscopy. The optical process of the carrier emission from the deep acceptor level of Fe is discussed from the results. For the crystal-field-split level of Fe2+:5E, the photoionization cross sections for the fundamental transitions of 5E→Γ1 and Γ15→5E are adequately described by the Lucovsky model. Those optical thresholds are 0.63 and 0.78 eV, respectively, at 77 K. In comparison with the deep-level transient spectroscopy measurements, the following conclusions are obtained. The energy separation between the Fe acceptor level and the conduction-band edge is constant, but that between the Fe level and the valence-band edge varies correspondingly to the temperature variation of the InP band-gap energy. The fact that there is no difference between the optical and thermal activation energies for the 5E→Γ1 transition indicates that the Fe acceptor level is not perturbed by the InP lattice vibration.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4946-4949 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied nonradiative recombination centers in undoped (AlxGa1−x)0.5In0.5Pgrown by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. We found three deep energy levels, including a mid-gap level. We drew an equation to get a capture cross section for minority carriers, and obtained it using isothermal capacitance transient spectroscopy measurement. The mid-gap level had an electron capture cross section of 2 × 10−10 cm2 and a hole capture cross section of 1 × 10−15 cm2. The time constant of nonradiative recombination through the mid-gap level was found to be comparable to that of radiative recombination. We concluded that the mid-gap level is an effective nonradiative recombination center that reduces photoluminescence intensity.
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