[en] Using niobium edge junctions and electron beam lithography (EBL) the authors have made direct coupled logic (DCL) OR gates with 1 μm minimum line widths. The gate cell, containing an isolator and a buffer section, fits into an area of approximately 25 by 30 μm². Our computer simulations show that these gates can have switching times of less than 10 ps. We have simulated the DCL circuit with several values of the most space-consuming element, an inductor. This paper describes the results of these simulations and presents a detailed description of the 7-level fabrication process. The mix of optical and electron-beam lithography used relies heavily on an inexpensive, yet powerful, circuit layout program

[en] We have fabricated and tested thin film, niobium edge junction, double transformer, dc superconducting quantum interference devices (SQUID's) that were stable under room-temperature storage and thermal cycling and that had very good noise performance. The input inductance, approximately 1.7 μH, was large enough to facilitate good matching to many experiments. When the SQUID was operated as a small-signal amplifier, the minimum detectable energy per unit bandwidth (S/sub e/) was 5 x 10^-33 J/Hz at 100 kHz, referred to the SQUID loop (uncoupled). The minimum detectable energy per unit bandwidth was 1.8 x 10^-31 J/Hz at 100 kHz, referred to the input coil. The SQUID's had good characteristics for flux-locked operation since the small signal S/sub e/ was low over a substantial range of bias current and magnetic flux. For operation in a flux-locked feedback circuit, S/sub e/ was 6 x 10^-32 J/Hz at 1 kHz

[en] We report harmonic generation from a bicrystal Josephson junction fabricated in the middle of a 50 Ω coplanar waveguide (CPW). Microwave radiation was injected at one end of the CPW transmission line, and the fundamental and third-harmonic powers were measured. A decrease of the fundamental transmitted power related to thermal breakdown was observed. The third-harmonic output power from the junctions was a complicated function of the input power, showing many non-third order-effects. (author)

[en] The authors have designed, fabricated, and tested a Double Transformer (DT) coupled dc SQUID (Superconducting Quantum Interference Device) with low noise, an input inductance of 1μH and a smooth input-output characteristic. A transmission line model is presented to explain a resonance in the input-output characteristic of early versions of this device. Guided by the results of numerical simulations a new version of this device has been built and tested. Experimental results are presented that show that the resonance can be moved to a higher voltage by reducing the area of the SQUID loop. The voltage-external flux characteristic of some of these new devices agrees to within 10% with computer simulations. The minimum detectable energy per unit bandwidth (MDE) referred to the SQUID loop, is 10h, where h is Planck's constant. Computer simulations indicate an MDE of 6h

[en] A process combining hydrofluoric acid (HF) and Ar⁺ ion milling has been used to make YBa₂Cu₃O_x/SrTiO₃/YBa₂Cu₃O_x(YBCO/STO/YBCO) multilayer test circuits. Low-angle steps can be readily etched in STO and YBCO films with this process. YBCO lines crossing 5 degree steps have about the same critical temperature T_c (89 endash 90 K) and critical current density J_c (approx-gt 1x10⁶ A/cm² at 86 K) as lines on planar surfaces. Via connections have the same T_c as other circuit components and adequate critical currents for most circuit designs. copyright 1996 American Institute of Physics

[en] Single-target RF magnetron sputtering was used to deposit superconducting thin films of Bi-Sr-Ca-Cu-O with a T/sub c/₀ above 80 K. Varying P/sub =/ modified the concentrations of Bi, Cu, and O in the films by 10%--20%. Higher annealing temperatures, especially with brief melting, favored the formation of the higher T/sub c/ phases. Tetragonal phases (6- and 75-K T/sub c/ ), with a = 3.8097 A, c = 24.607 A, and Bi₂ Sr₂ CuO₆ composition, and a = 3.812 A, c = 30.66 A, and Bi₂ Sr/sub 2-//sub x/ Ca/sub 1+//sub x/ Cu₂ O₈ composition, were identified. 70--84 K films contained large proportions of a new tetragonal phase, with a = 3.81 A and c = 55.23 A

[en] Using an in-situ, self-aligned deposition scheme, arrays of variable length SNS junctions in the range of 0.05 μm to 1 μm have been fabricated. Arrays of SNS microbridges of lead-copper and niobium-copper fabricated using this technique have been used to study the length dependence, at constant temperature, of the critical current I and bridge resistance R /SUB d/ . For bridges with lengths pounds greater than the normal metal coherence length xi /SUB n/ (T), the dependence of I /SUB c/ on L is consistent with an exponential dependence on the reduced length l=L/xi /SUB n/ (T). For shorter bridges, deviations from this behavior is seen. It was also found that the bridge resistance R /SUB d/ does not vary linearly with the geometric bridge length but appears to approach a finite value as L→O

[en] The technology of Josephson voltage standards has been extended to an array of 14 184 junctions which is capable of generating over 150 000 quantized voltage levels spanning the range from -12 to +12V. This makes possible the direct calibration of 10-V Zener reference standards without the use of a voltage divider

[en] We have used the squeezable electron tunneling junction technique for testing the electrical properties of the surfaces of YBa₂Cu₃O/sub x/ (YBCO) thin-film electrodes. As deposited and annealed, the surfaces of the electrodes were insulating at 4 K. Several methods were used to improve the electrical properties of the electrodes' surfaces including rapid thermal annealing, oxygen sputter etching, and thin Ag coating treatments. The greatest improvement occurred after a deposition of a 5 nm Ag coating and subsequent rapid thermal anneal of one set of YBCO films. Under these conditions it was possible to make a superconducting Josephson point contact between the surfaces of the electrodes. We think that the Ag acts as a normal-metal proximity layer effectively shunting the degraded electrodes' surfaces

[en] We have measured the transport critical current density (J_c) in epitaxial quality films of YBa₂Cu₃O_7-δ some of which were covered by thin (10 nm) Ag films. The films, both with and without Ag, had J_c values greater than 10⁶ A/cm² in liquid nitrogen. The effect of the Ag was to greatly reduce the dependence of J_c on external magnetic fields in the case where the field was oriented in the plane of the film, that is, perpendicular to the c axis. It is unlikely that the effect is simply due to altered surface pinning, although qualitative agreement with critical state models is observed