Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Conference on Precision Electromagnetic Measurements

Development and Fabrication of Improved Josephson Series Arrays with NbSi Barrier for AC Voltage Standards

J. Kohlmann, Oliver Kieler, Ruediger Wendisch, B. Egeling, Ralf Behr

Published Jul 1, 2018• 2 citations
Publisher

Abstract

Series arrays of overdamped Josephson junctions compose the basis of AC Josephson voltage standards. Presently, an advanced technology is based on Josephson junctions consisting of an NbxSi1-xbarrier. Using junction stacks containing five Josephson junctions, series arrays of 15,000 junctions have been successfully fabricated at PTB for the pulse-driven Josephson Arbitrary Waveform Synthesizer (JAWS). The operation of eight arrays simultaneously enable spectrally pure waveforms with output voltages above 1 V to be synthesized.

DOI
10.1109/cpem.2018.8500887

Related papers

Series Arrays of NbSi Barrier Junctions with RF Power Dividers for AC Josephson Voltage Standards

J. Kohlmann, Hao Tian, Oliver Kieler +3 more

Overdamped Josephson junctions for AC voltage standards are realized with NbxSi1-xbarrier junctions at PTB. The characteristic parameters of the junctions can be tuned over a wide range by adjusting the Nb content and the thickness of the barrier. For the pulse-driven Josephson Arbitrary Waveform Synthesizer (JAWS), series arrays of up to 15,000 Josephson junctions have been fabricated using junction stacks containing five Josephson junctions. In addition, two types of on-chip power dividers have been investigated at PTB, namely Wilkinson and serial-parallel power dividers, respectively. These developments aim for further increasing the number of Josephson junctions on a single chip and thus for increasing the output voltage.

Conference on Precision Electromagnetic Measurements•Aug 1, 2020•0 citations

Series arrays of NbSi barrier Josephson junctions for AC voltage standards

J. Kohlmann, Oliver Kieler, Thomas Scheller +3 more

AC Josephson voltage standards are typically based on series arrays of overdamped Josephson junctions, which are presently realized using an NbxSi1-xbarrier at PTB. The characteristic parameters of these SNS-like junctions can be tuned by the Nb content and the thickness of the barrier over a wide range for operation from 10 GHz to 70 GHz. Based on these junctions, we developed binary-divided 10 V arrays as well as pulse-driven arrays for 1 V output voltages.

Conference on Precision Electromagnetic Measurements•Jul 1, 2016•2 citations

Stacked Josephson Junction Arrays for the Pulse-Driven AC Josephson Voltage Standard

Oliver Kieler, Ruediger Wendisch, Rolf-Werner Gerdau +3 more

We developed a fabrication process to establish large arrays of up to 5-stacked Josephson junctions for the Josephson Arbitrary Waveform Synthesizer (JAWS). SNS-type Josephson junctions with NbxSi1-xbarriers are used for this application. By modifying our standard window process, e.g. to add a CMP (chemical mechanical polishing) and an ALD (atomic layer deposition) step, the yield of this process was increased. An output voltage of 1 V RMS could be achieved by using 4 JAWS arrays in series with a total number of 60,000 5-stacked junctions. The investigation of the current-voltage characteristics (IVC) showed an interesting and potentially useful feature. The required pulse amplitude per junction for getting the maximum Shapiro step width reduces for higher junction stacks. We found that the pulse power linearly reduces with the square of the junction number in the array. The origin of this effect might be a strong neighbour-neighbour interaction of the junctions, which are closely arranged within the stacked configuration. This might generate a strong self-synchronization of the junctions.

IEEE Transactions on Applied Superconductivity•Feb 20, 2021•18 citations

Towards a 1 V Josephson Arbitrary Waveform Synthesizer

Oliver Kieler, Ralf Behr, Ruediger Wendisch +3 more

The establishment at PTB of an AC Josephson voltage standard (Josephson Arbitrary Waveform Synthesizer- JAWS) based on pulse-driven Josephson arrays is focused on achieving an output voltage of at least 1 Vrms which is required for many metrology applications. In this paper, we approached this goal by increasing the number of active junctions in two ways. Firstly, we fabricated arrays containing triple-stacked SNS-type Josephson junctions with NbxSi1-xas barrier material. We obtained current operation margins of about 0.2 mA with arrays of up to 9000 Josephson junctions at an rms voltage of 355 mV. Secondly, we used a new 8-channel ternary pulse pattern generator (PPG) to bias up to 8 arrays connected in series. An output voltage of VRMS= 1006 mV(VPP= 2.845 V) was achieved by using 8 arrays (arranged on 4 separate chips) with 63000 junctions in total. Higher harmonics are suppressed by at least -116 dBc. The fabrication process and the experimental setup will be described, as well as experimental results that are leading towards our 1 V goal.

IEEE Transactions on Applied Superconductivity•Nov 10, 2014•97 citations

Josephson Series Arrays for Programmable 10-V SINIS Josephson Voltage Standards and for Josephson Arbitrary Waveform Synthesizers Based on SNS Junctions

J. Kohlmann, F. Muller, Oliver Kieler +4 more

Programmable Josephson voltage standards for output voltages up to 10 V have been realized. Binary-divided series arrays consisting of 69 632 overdamped SINIS Josephson junctions have been fabricated using reliable Nb-Al/Al2O3technology (S: superconductor, I: insulator, N: normal metal). Series arrays of about 1000 SNS Josephson junctions were realized as lumped arrays for applications in the Josephson arbitrary waveform synthesizer (JAWS). We suggest a novel scheme for combining the higher voltages generated by the binary-divided arrays with the frequency spectral characteristics of the JAWS, in order to optimize the frequency spectrum of the generated ac voltages

IEEE Transactions on Instrumentation and Measurement•Mar 16, 2007•32 citations

Cryocooler Operation of a Pulse-Driven AC Josephson Voltage Standard at PTB

Oliver Kieler, Thomas Scheller, J. Kohlmann

The PTB Josephson Arbitrary Waveform Synthesizer (JAWS) enables the generation of arbitrary waveforms up to voltages of 70 mVRMS (199 mVPP) using two Josephson arrays in series containing 4000 Josephson junctions each. The SNS-like double-stacked junctions are based on NbxSi1-x as barrier material. While the JAWS system is typically operated using a Dewar with liquid helium, the operation in a closed-cycle pulse-tube cryocooler at temperatures around 4.2 K range was here investigated and successfully demonstrated. For this purpose a special designed cryoprobe was used to provide high quality pulses to the Josephson arrays.

World Journal of Condensed Matter Physics•Jan 1, 2013•28 citations
Series arrays of overdamped Josephson junctions compose the basis of AC Josephson voltage standards. Presently, an advanced technology is based on Josephson junctions consisting of an NbxSi1-xbarrier. Using junction stacks containing five Josephson junctions, series arrays of 15,000 junctions have been successfully fabricated at PTB for the pulse-driven Josephson Arbitrary Waveform Synthesizer (JAWS). The operation of eight arrays simultaneously enable spectrally pure waveforms with output voltages above 1 V to be synthesized.
Overdamped Josephson junctions for AC voltage standards are realized with NbxSi1-xbarrier junctions at PTB. The characteristic parameters of the junctions can be tuned over a wide range by adjusting the Nb content and the thickness of the barrier. For the pulse-driven Josephson Arbitrary Waveform Synthesizer (JAWS), series arrays of up to 15,000 Josephson junctions have been fabricated using junction stacks containing five Josephson junctions. In addition, two types of on-chip power dividers have been investigated at PTB, namely Wilkinson and serial-parallel power dividers, respectively. These developments aim for further increasing the number of Josephson junctions on a single chip and thus for increasing the output voltage.
We developed a fabrication process to establish large arrays of up to 5-stacked Josephson junctions for the Josephson Arbitrary Waveform Synthesizer (JAWS). SNS-type Josephson junctions with NbxSi1-xbarriers are used for this application. By modifying our standard window process, e.g. to add a CMP (chemical mechanical polishing) and an ALD (atomic layer deposition) step, the yield of this process was increased. An output voltage of 1 V RMS could be achieved by using 4 JAWS arrays in series with a total number of 60,000 5-stacked junctions. The investigation of the current-voltage characteristics (IVC) showed an interesting and potentially useful feature. The required pulse amplitude per junction for getting the maximum Shapiro step width reduces for higher junction stacks. We found that the pulse power linearly reduces with the square of the junction number in the array. The origin of this effect might be a strong neighbour-neighbour interaction of the junctions, which are closely arranged within the stacked configuration. This might generate a strong self-synchronization of the junctions.
The establishment at PTB of an AC Josephson voltage standard (Josephson Arbitrary Waveform Synthesizer- JAWS) based on pulse-driven Josephson arrays is focused on achieving an output voltage of at least 1 Vrms which is required for many metrology applications. In this paper, we approached this goal by increasing the number of active junctions in two ways. Firstly, we fabricated arrays containing triple-stacked SNS-type Josephson junctions with NbxSi1-xas barrier material. We obtained current operation margins of about 0.2 mA with arrays of up to 9000 Josephson junctions at an rms voltage of 355 mV. Secondly, we used a new 8-channel ternary pulse pattern generator (PPG) to bias up to 8 arrays connected in series. An output voltage of VRMS= 1006 mV(VPP= 2.845 V) was achieved by using 8 arrays (arranged on 4 separate chips) with 63000 junctions in total. Higher harmonics are suppressed by at least -116 dBc. The fabrication process and the experimental setup will be described, as well as experimental results that are leading towards our 1 V goal.
Programmable Josephson voltage standards for output voltages up to 10 V have been realized. Binary-divided series arrays consisting of 69 632 overdamped SINIS Josephson junctions have been fabricated using reliable Nb-Al/Al2O3technology (S: superconductor, I: insulator, N: normal metal). Series arrays of about 1000 SNS Josephson junctions were realized as lumped arrays for applications in the Josephson arbitrary waveform synthesizer (JAWS). We suggest a novel scheme for combining the higher voltages generated by the binary-divided arrays with the frequency spectral characteristics of the JAWS, in order to optimize the frequency spectrum of the generated ac voltages
The PTB Josephson Arbitrary Waveform Synthesizer (JAWS) enables the generation of arbitrary waveforms up to voltages of 70 mVRMS (199 mVPP) using two Josephson arrays in series containing 4000 Josephson junctions each. The SNS-like double-stacked junctions are based on NbxSi1-x as barrier material. While the JAWS system is typically operated using a Dewar with liquid helium, the operation in a closed-cycle pulse-tube cryocooler at temperatures around 4.2 K range was here investigated and successfully demonstrated. For this purpose a special designed cryoprobe was used to provide high quality pulses to the Josephson arrays.