Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T−1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

Fabrication and characterisation of YBCO step-edge Josephson junction arrays in a series configuration are reported. The junction arrays were fabricated using CSIRO YBCO step-edge junction technology, which, owing to the flexibility of locating the junctions anywhere on the chip, makes it very attractive for implementation of multiple HTS devices and circuits. Arrays of 50 junctions in series were fabricated, and the DC current-voltage (I-V) characterisations were studied at temperatures ranging from 15 to 77 K; temperatures were obtained via either placing the samples in the vent gas of a liquid He cryostat or use of a commercial cryocooler. Eight fabricated and tested arrays, totalling 400 junctions, showed no electrically open or shorted junctions (i.e., a 100% yield of working Josephson junctions), demonstrating good fabrication reliability. Large junction normal resistances (several hundred Ωs) were obtained from the series junction arrays, making them suitable for a range of high-frequency applications. A study of the junction critical current spread within an array, magnetic field dependence of the critical current, and microwave responses of the arrays is also described.

The dc transport properties of high-temperature superconducting Josephson junction arrays were investigated. Each array had the same design of 50 junctions in series, with each junction formed from a YBa 2 Cu 3 O 7−x (YBCO) grain boundary grown on an engineered MgO step-edge substrate. The variation of critical current was analysed and modelled. Comparisons were made on the average and one sigma standard deviation, σ , of I c values for arrays fabricated both on the same chip and a different chip. For arrays containing 2 µm wide junctions, the typical values of σ were 20-35%. Increasing the junction width reduces σ to 8-15% in arrays with 4 µm wide junctions, qualitatively consistent with the prediction using a model of multiple channels across the width of the junction.

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