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28 Dec 1998

Volume 73, Issue 26, pp. 3803-3961

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Performance of high-Tc superconducting quantum interference devices with resistively shunted inductances

D. J. Kang, W. E. Booij, M. G. Blamire, and E. J. Tarte

Appl. Phys. Lett. 73, 3929 (1998); http://dx.doi.org/10.1063/1.122939 (3 pages) | Cited 4 times

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The voltage modulation depths, ΔV of high-Tc direct current superconducting quantum interference devices (SQUIDs) with resistors connected in parallel with their inductances were investigated. Both the junctions and resistors in the SQUIDs were fabricated using focused electron-beam irradiation. The effect of varying the resistor value (using focused ion-beam trimming) and the screening parameter βL (by varying the temperature and hence the junction critical current) were studied. Significant enhancement of ΔV relative to an equivalent unshunted SQUID for βL values up to 50 was observed, and the most effective shunt resistor value was found to be approximately equal to the junction resistance. © 1998 American Institute of Physics.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors

Direct current voltage increment due to ac coupling in a high Tc superconducting coil

N. Shaked, I. A. Al-Omari, A. Friedman, Y. Wolfus, M. Sinvani, A. Shaulov, and Y. Yeshurun

Appl. Phys. Lett. 73, 3932 (1998); http://dx.doi.org/10.1063/1.122940 (3 pages) | Cited 3 times

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The voltage–current characteristics of a superconducting coil, made of multifilamentary silver-sheathed Bi2Sr2Ca2Cu3O10+δ tape, are investigated. We find that a small ac current Iac superimposed on a relatively large dc current Idc causes a significant increase in the coil dc voltage, approximately proportional to Idc, Iac2, and the ac frequency. We attribute this effect to the nonlinear magnetoresistance of the coil, and discuss its significance in power applications of high Tc superconducting coils, such as fault current limiters and superconducting magnetic energy storage devices. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.F- Transport properties
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
84.60.Ve Energy storage systems, including capacitor banks

Enhancement of transport critical current densities in Bi2Sr2Ca2Cu3Ox tapes by fission tracks

G. W. Schulz, C. Klein, H. W. Weber, S. Moss, R. Zeng, S. X. Dou, R. Sawh, Y. Ren, and R. Weinstein

Appl. Phys. Lett. 73, 3935 (1998); http://dx.doi.org/10.1063/1.122941 (3 pages) | Cited 14 times

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Bi2Sr2Ca2Cu3Ox (Bi-2223) tapes were processed by the standard powder-in-tube technique, but small amounts of UO4 were added prior to processing. Both U-doped and undoped tapes were subsequently exposed to a reactor spectrum of neutrons. Whereas the undoped materials show moderate enhancements of the critical current densities Jc due to the pinning action of the fast-neutron-induced collision cascades, Jc in the U-doped tapes increases by factors of 10–20 due to thermal-neutron-induced fission of 235U and the subsequent formation of fission tracks. Since the enhancements are particularly pronounced, when the magnetic field is applied perpendicular to the tape surface, the characteristic Jc anisotropy is strongly reduced in a certain field range. At the same time, the irreversibility field at 77 K is doubled for both field orientations. © 1998 American Institute of Physics.
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74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.62.Dh Effects of crystal defects, doping and substitution

Ultimate quantum efficiency of a superconducting hot-electron photodetector

K. S. Il’in, I. I. Milostnaya, A. A. Verevkin, G. N. Gol’tsman, E. M. Gershenzon, and Roman Sobolewski

Appl. Phys. Lett. 73, 3938 (1998); http://dx.doi.org/10.1063/1.122942 (3 pages) | Cited 23 times

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The quantum efficiency and current and voltage responsivities of fast hot-electron photodetectors, fabricated from superconducting NbN thin films and biased in the resistive state, have been shown to reach values of 340, 220 A/W, and 4×104 V/W, respectively, for infrared radiation with a wavelength of 0.79 μm. The characteristics of the photodetectors are presented within the general model, based on relaxation processes in the nonequilibrium electron heating of a superconducting thin film. The observed, very high efficiency and sensitivity of the superconductor absorbing the photon are explained by the high multiplication rate of quasiparticles during the avalanche breaking of Cooper pairs. © 1998 American Institute of Physics.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
74.78.-w Superconducting films and low-dimensional structures
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.N- Response to electromagnetic fields
74.25.Kc Phonons

Growth of highly oriented Pb(Zr, Ti)O3 films on MgO-buffered oxidized Si substrates and its application to ferroelectric nonvolatile memory field-effect transistors

Nasir Abdul Basit, Hong Koo Kim, and Jean Blachere

Appl. Phys. Lett. 73, 3941 (1998); http://dx.doi.org/10.1063/1.122943 (3 pages) | Cited 27 times

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We have grown highly oriented lead zirconate titanate [Pb(Zr, Ti)O3 or PZT] films on oxidized silicon substrates using a thin MgO buffer layer (7–70 nm thick). Ferroelectric nonvolatile memory field-effect transistors (FETs) were successfully fabricated using the metal/PZT/MgO/SiO2/Si structure in conjunction with radio-frequency sputter deposition of PZT and MgO films. The fabricated devices show excellent performance in ferroelectric polarization switching and memory retention. The results indicate that a thin MgO buffer serves well not only as a template layer for the growth of oriented PZT films on amorphous substrates, but also as a diffusion barrier between a ferroelectric and a substrate during device fabrication, protecting the SiO2/Si interface and the FET channel region. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Fm Switching phenomena
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
81.15.Cd Deposition by sputtering
77.55.-g Dielectric thin films
85.30.Tv Field effect devices
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