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We have fabricated and characterized direct-injection High Temperature Superconducting (HTS) SQUIDs using a six-epitaxial-layer process which integrates edge geometry superconductor-normal-superconductor (SNS) junctions with an HTS ground plane. The period of the SQUID threshold curves was used to infer microstrip inductances of approximately 1 pH//spl square/ at 65 K. Total SQUID inductances as low as /spl ap/5 pH were inferred from the measured critical current modulation depth. A novel junction geometry was used in some devices to reduce the parasitic inductances of the junction leads by approximately 1 pH. Maintaining such low inductances is particularly important for Single Flux Quantum digital circuits. [ABSTRACT FROM PUBLISHER]

We have fabricated high-T/sub c/ SNS weak links in an edge geometry with integrated YBa/sub 2/Cu/sub 3/O/sub x/ (YBCO) groundplanes and SrTiO/sub 3/ insulators, using a process which incorporates six epitaxial layers, including a Co-doped-YBCO normal-metal interlayer. The SNS edge junctions were produced using films deposited by both off-axis sputtering and pulsed laser deposition. These devices exhibit tight J/sub c/ spreads and high I/sub c/R/sub n/ products in a current density regime well-suited for SFQ circuit fabrication. We also describe results on SNS junctions fabricated in a novel "slot" geometry, designed to reduce junction and interconnect inductances. [ABSTRACT FROM PUBLISHER]

We have developed a process for fabrication of HTS single-flux-quantum logic circuits based on edge SNS junctions which requires six epitaxial film layers and six mask levels. The process was successfully applied to fabrication of small-scale circuits (/spl les/10 junctions). This paper examines the materials properties affecting the reproducibility of YBCO-based SNS junctions, the low inductance provided by an integrated YBCO ground plane, and electrical isolation by SrTiO/sub 3/, or Sr/sub 2/AlTaO/sub 6/, ground-plane and junction insulator layers. Some of the critical processing parameters identified by electrical measurements, TEM, SEM, and AFM were control of second-phase precipitates in YBCO, oxygen diffusion, Ar ion-milling parameters, and preparation of surfaces for subsequent high-temperature depositions. [ABSTRACT FROM PUBLISHER]

We have fabricated and measured high T/sub c/ superconductor single flux quantum 1-bit flux-counting analog-to-digital converters (ADCs). The ADCs were made with a multilayer all-epitaxial process which incorporates 10 edge SNS (superconductor-normal-superconductor) or step-edge grain boundary (SEGB) Josephson junctions with a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// groundplane. The ADC consists of a quantizer connected to a Toggle flip-flop through a buffer-like stage. Direct readout of the flux state of the T flip-flop was made with a Read SQUID inductively coupled through a hole in the groundplane. The circuits were operated at 65 K and low speeds. The SNS circuits outperformed the SEGB circuits because of their higher readout voltages and tighter critical current spreads. [ABSTRACT FROM PUBLISHER]

Contiguous 7-pole filters centred at 7.97 and 8.00 GHz have been made by co-evaporation of YBa/sub 2/Cu/sub 3/O/sub x/ thin films on MgO substrates. The 0.3% bandwidth filters make stringent demands on the design and fabrication processes. Good control of the centre frequency and bandwidth, sharp cut-offs and high linearity have been achieved. A pair of filters has been assembled as a layer of a combiner circuit, and its characteristics studied. Although the individual filters have been successfully made to high accuracy, the extreme precision required by a combiner circuit would require some tuning for high performance, at least at the present state of the technology. [ABSTRACT FROM PUBLISHER]

Superconductor-Normal-Superconductor (SNS) edge Josephson Junctions (JJs) continue to be a focus of high-T/sub c/ superconductor (HTS) electronics development. The ability to form clean edges in HTS materials is essential for successful SNS edge JJs as well as crossovers and via contacts. We report a novel SNS JJ fabrication process in which a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta///SrTiO/sub 3/ base electrode/insulator bilayer coated with a polyimide passivation layer is rotated during Ar ion milling through a reflowed photoresist mask to form omnidirectional edges. No sample cooling is used during milling. YBa/sub 2/Cu/sub 2.8/Co/sub 0.2/O/sub 7-/spl delta// normal layers and YLa/sub 0.05/Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// counter-electrodes completed the SNS JJ's. Devices fabricated using this polyimide passivation layer have significantly smaller spreads in critical current and resistance than those processed without it. [ABSTRACT FROM PUBLISHER]