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17 Aug 1998

Volume 73, Issue 7, pp. 865-1010

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Microwave electric-field imaging using a high-Tc scanning superconducting quantum interference device

S. Chatraphorn, E. F. Fleet, R. C. Black, and F. C. Wellstood

Appl. Phys. Lett. 73, 984 (1998); http://dx.doi.org/10.1063/1.122060 (3 pages) | Cited 5 times

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We have used a 77 K thin-film YBa2Cu3O7 superconducting quantum interference device (SQUID) in a scanning SQUID microscope to image room-temperature sources of high-frequency electric field. We find that time-varying electric fields capacitively induce currents in the SQUID, which in turn are rectified by the nonlinearity of the SQUID current–voltage characteristics, leading to changes in the quasistatic voltage across the SQUID. By observing changes in the voltage modulation depth ΔV of the SQUID as a sample is scanned past the SQUID, we obtain electric-field images in the 1–15 GHz frequency range with a SQUID-to-sample separation of about 80 μm. © 1998 American Institute of Physics.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
74.50.+r Tunneling phenomena; Josephson effects

Influence of the number of deposited atoms per shuttering cycle on surface morphology of sequentially deposited Pb2Sr2EuCu3Oy films

Yuichi Motoi and Sumio Ikegawa

Appl. Phys. Lett. 73, 987 (1998); http://dx.doi.org/10.1063/1.122061 (3 pages) | Cited 3 times

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The relation between surface morphology and growth conditions on Pb2Sr2EuCu3Oy (Pb-3212) thin films has been studied. The Pb-3212 thin films were grown by the molecular beam epitaxy method with monolayer-by-monolayer deposition. It was found that the surface morphology depends on the amounts of atoms deposited per unit area during one cycle of deposition sequence to form the Pb-3212 unit cell. The Cu2O precipitates were observed when the amount for Cu is larger than the ideal value or that for Sr is less than the ideal value. The averaged roughness of the smoothest film grown under Sr-rich and Cu-deficient conditions is less than 0.30 nm. © 1998 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.72.-h Cuprate superconductors
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology

High-performance (Hg, Re)Ba2CaCu2Oy grain-boundary Josephson junctions and dc superconducting quantum interference devices

A. Tsukamoto, K. Takagi, Y. Moriwaki, T. Sugano, S. Adachi, and K. Tanabe

Appl. Phys. Lett. 73, 990 (1998); http://dx.doi.org/10.1063/1.122062 (3 pages) | Cited 10 times

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High-performance grain-boundary Josephson junctions and dc superconducting quantum interference devices (SQUIDs) have been fabricated using c-axis oriented (Hg, Re)Ba2CaCu2Oy thin films grown on bicrystal SrTiO3 substrates with a 24° misorientation angle. The junctions exhibit supercurrent up to a temperature close to the film Tc and resistively shunted junctionlike current–voltage characteristics. A rather high IcRn product of 400–460 μV is observed at 77 K in some junctions. The dc SQUIDs show a field-induced periodic voltage up to 111 K. They also exhibit a voltage modulation depth as large as 90, 27, and 1–2 μV at 77, 97, and 111 K, respectively. © 1998 American Institute of Physics.
Show PACS
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
85.25.Cp Josephson devices
74.50.+r Tunneling phenomena; Josephson effects
61.72.Mm Grain and twin boundaries
74.10.+v Occurrence, potential candidates
81.65.Cf Surface cleaning, etching, patterning
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Field-dependent microsusceptometry on magnetic crystallites with integrated dc SQUIDs

L. R. Narasimhan, C. K. N. Patel, and M. B. Ketchen

Appl. Phys. Lett. 73, 993 (1998); http://dx.doi.org/10.1063/1.122063 (3 pages) | Cited 2 times

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We report the use of unshielded planar low-Tc dc SQUIDs for temperature-dependent ac and dc magnetic susceptibility measurements on small particles in magnetic fields of up to 300 G. These measurements were made with integrated microsusceptometers which can operate in such fields when applied in the plane of the device. We show paramagnetic, antiferromagnetic, and superconducting behavior on various samples of order 20–50 μm from 0.3 to 4 K and discuss the effect of sample placement on the magnitude of the signal. © 1998 American Institute of Physics.
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07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements
85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
75.50.Tt Fine-particle systems; nanocrystalline materials
85.25.Dq Superconducting quantum interference devices (SQUIDs)
75.30.Cr Saturation moments and magnetic susceptibilities

Nb/Al/AlOx/AlOx/Al/Nb Josephson junctions for programmable voltage standards

H. Schulze, R. Behr, F. Müller, and J. Niemeyer

Appl. Phys. Lett. 73, 996 (1998); http://dx.doi.org/10.1063/1.122064 (3 pages) | Cited 60 times

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We present a study of the microwave characteristics of Josephson junctions based on a superconductor–insulator–normal–insulator–superconductor sandwich, fabricated in Nb/Al/AlOx technology. With the nonhysteretic Shapiro steps and the small parameter spread observed, the junctions are suitable for programmable Josephson voltage standards. Their characteristic voltage Vc ≈ 100 μV enables operation at microwave frequencies up to 100 GHz. © 1998 American Institute of Physics.
Show PACS
74.50.+r Tunneling phenomena; Josephson effects
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
85.25.Cp Josephson devices
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
06.20.F- Units and standards
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