Abstract
Binary-divided 1 V arrays were fabricated for programmable Josephson voltage standards inclose cooperation between INRIM and PTB. The arrays, consisting of 8192 overdampedNb/Al–AlOxNb SNIS Josephson junctions, were successfully operated at microwave frequenciesaround 70 GHz. While the characteristic voltage of the junctions ranged from0.25 to 0.6 mV, the current margins were larger than 1 mA for the Shapiro stepn = 1. In addition, flat Shapiro steps of higher order (n = 3 and 4) were generated at increased microwave power levels due to the large characteristicvoltage, demonstrating the small parameter spread of the SNIS junctions. Operation attemperatures up to 6–7 K has also been verified, measuring quantized voltages up to 1.25 V on then = 1 step.
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