RF Properties of Overdamped SIS Junctions

Abstract

A new type of nonhysteretic Josephson junction suitable for applications in voltage metrology has been developed. These junctions derive from the Nb Al AlO Nb SIS junctions using a relatively thick Al layer oxidized at a low value of oxygen exposure. This produces junctions with reproducible and spatially homogeneous -characteristics, having current densities ranging from 10 3 to more than 2 10 4 A cm 2 and characteristic voltages up to 0.40 mV. The authors report here the rf response of these junctions at 70 GHz. The authors have measured the dependence of the rf-induced steps on the microwave power and the stability of the steps, in view of a future application of these junctions to an ac Josephson voltage standard.

Advancements in quantum voltage standards for time-dependent signals

“…Such arrays are generally subdivided in sub-circuits with series-connected junctions generating voltages following a power-of-two rule: combining the voltage across all sections it is thus possible to source binary programmed voltages equivalent to the technique used in electronic digital-to-analog converters. Many approaches to junction fabrication have been developed, and several different technologies have proven successful in generating voltages up to 10 V, with good metrological properties: SINIS [5], SNIS [6], [7] with respectively Nb, Al and AlO x as superconducting (S), normal (N) and insulating (I) elements, and the more recent SNS junctions with Nb x Si 1-x barriers [8], and NbN/TiN x /NbN junctions for higher temperature operation [9]. The most relevant limitation of PJVS devices is to be found in the time for step switching, when junctions are not operating in a quantized state.…”

Recent advancements and perspectives of INRiM’s time-dependent Josephson voltage standards

“…This rapid and easy programmability of novel Josephson voltage standards is exploited also outside the electrical metrology field, e.g. in Kibble balances [5] for the quantum traceability of the kg unit to the SI through h e e, in conjunction with the quantum Hall resistance standards.Many approaches to junction fabrication have been developed, and several different technologies have proven successful in generating voltages up to 10 V, with good metrological properties: SINIS [6], SNIS [7], [8] with respectively Nb, Al and AlOx as superconducting (S), normal (N) and insulating (I) elements, the more recent SNS junctions with NbxSi1-x barriers [9], and NbN/TiNx/NbN junctions for higher temperature operation [10]. The most relevant limitation of PJVS devices is to be found in the time for step switching, when junctions are not operating in a quantized state.…”

“…Many approaches to junction fabrication have been developed, and several different technologies have proven successful in generating voltages up to 10 V, with good metrological properties: SINIS [6], SNIS [7], [8] with respectively Nb, Al and AlOx as superconducting (S), normal (N) and insulating (I) elements, the more recent SNS junctions with NbxSi1-x barriers [9], and NbN/TiNx/NbN junctions for higher temperature operation [10]. The most relevant limitation of PJVS devices is to be found in the time for step switching, when junctions are not operating in a quantized state.…”