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Conference on Precision Electromagnetic Measurements

Development and investigation of Nb-Al-oxide-Nb Josephson junction arrays [voltage standard application]

A.F. Bochanov, V.D. Gelikonova, Alexander M. Klushin, P.A. Shisharin, I. Ya. Krasnopolin

Published Dec 17, 2002• 0 citations
Publisher

Abstract

An array of 3072 Josephson junctions Nb-AlO/sub x/-Nb is developed at IEM "KVARZ". Some preliminary results of an investigation of I-V curves under microwave irradiation in the 70 GHz frequency band are given. Zero current quantized voltage steps are displayed up to 450 mV with an amplitude >100 /spl mu/A. An improvement of the fabrication process, which is in progress, will enable to increase quantized voltage steps region up to 1 V.>

DOI
10.1109/cpem.1994.333440

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Development and investigation of Nb-Al-oxide-Nb Josephson Junction arrays

A.F. Bochanov, V.D. Gelikonova, Alexander M. Klushin

An array of 3072 Josephson junctions Nb - AlO{sub x} - Nb is developed at IEM {open_quotes}KVARZ{close_quotes}. Some preliminary results of an investigation of IV curves under microwave irradiation in the 70 GHz frequency band are given. Zero current quantized voltage steps are displayed up to 450 mV with an amplitude > 100 {mu}A. An improvement of the fabrication process, which is in progress, will enable to increase quantized voltage steps region up to IV.

•Dec 31, 1994•0 citations

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A computer-controlled Josephson voltage standard has been developed comprising the hybrid integration of a planar oscillator and a Josephson series array. A 10 GHz voltage controlled oscillator has been frequency-stabilized to a reference frequency by a phase-locked loop. A series array has been designed and fabricated in Nb/Al/sub 2/O/sub 3//Nb technology. To obtain quantized voltage steps with a drive frequency of 10 GHz, the critical current density of the Junctions is reduced to below 2 A/cm/sup 2/ by variation of the oxidation parameters. The hybrid integration of a Josephson circuit with a planar MESFET oscillator produced quantized voltage steps up to 980 mV with a step width of 2 /spl mu/A.

IEEE Transactions on Instrumentation and Measurement•Apr 1, 1997•1 citation

Development of 10-v josephson series arrays

Se Il Park, Hyun Kwon Hong

Developed a new fabrication process for 10-V Josephson junction series arrays (JJAs). A plasma nitridation process is employed for reducing the microwave attenuation in the Josephson microstripline. Improvements of microwave attenuation are about 2 dB for test arrays of 2000, 3000, and 4000 Josephson junctions in a single stripline. We obtained stable quantized voltage steps up to 12 V at 76.4 and 86.8 GHz with step amplitudes of more than 5 /spl mu/A and stability times of more than 5 min. The circuits used 14 648 junctions arranged in 8 parallel paths.

IEEE Transactions on Instrumentation and Measurement•Apr 1, 2003•3 citations

1 V programmable voltage standards based on SNIS Josephson junction series arrays

V. Lacquaniti, Natascia De Leo, Matteo Fretto +3 more

Binary-divided 1 V arrays were fabricated for programmable Josephson voltage standards in close cooperation between INRIM and PTB. The arrays, consisting of 8192 overdamped Nb/Al-AlO(x)Nb SNIS Josephson junctions, were successfully operated at microwave frequencies around 70 GHz. While the characteristic voltage of the junctions ranged from 0.25 to 0.6 mV, the current margins were larger than 1 mA for the Shapiro step n = 1. In addition, flat Shapiro steps of higher order (n = 3 and 4) were generated at increased microwave power levels due to the large characteristic voltage, demonstrating the small parameter spread of the SNIS junctions. Operation at temperatures up to 6-7 K has also been verified, measuring quantized voltages up to 1.25 V on the n = 1 step.

Superconductor Science and Technology•Jan 27, 2011•37 citations
An array of 3072 Josephson junctions Nb-AlO/sub x/-Nb is developed at IEM "KVARZ". Some preliminary results of an investigation of I-V curves under microwave irradiation in the 70 GHz frequency band are given. Zero current quantized voltage steps are displayed up to 450 mV with an amplitude >100 /spl mu/A. An improvement of the fabrication process, which is in progress, will enable to increase quantized voltage steps region up to 1 V.>
Stacked Josephson junction arrays located at the rf current antinodes of a superconducting microstripline resonator were investigated. The circuits were designed to obtain highly accurate voltages at cm-waveband microwave driving and low rf-power level. Nb-Al/AlO/sub x/-Nb Josephson junctions with tunneling area of 60 /spl mu/m/spl times/300 /spl mu/m and critical current density up to 7 A/cm/sup 2/ were used. We compared the average voltages of the rf induced maximal current steps in arrays with up to three junctions per stack. Quantized current steps up to 300 mV were observed under microwave irradiation at frequency of 19.20 GHz in circuits with 384 three-junction stacks. The dynamics of stacked tunnel junctions in the presence of rf-currents will be discussed with respect to application as voltage standards.
A computer-controlled Josephson voltage standard has been developed comprising the hybrid integration of a planar oscillator and a Josephson series array. A 10 GHz voltage controlled oscillator has been frequency-stabilized to a reference frequency by a phase-locked loop. A series array has been designed and fabricated in Nb/Al/sub 2/O/sub 3//Nb technology. To obtain quantized voltage steps with a drive frequency of 10 GHz, the critical current density of the Junctions is reduced to below 2 A/cm/sup 2/ by variation of the oxidation parameters. The hybrid integration of a Josephson circuit with a planar MESFET oscillator produced quantized voltage steps up to 980 mV with a step width of 2 /spl mu/A.
Developed a new fabrication process for 10-V Josephson junction series arrays (JJAs). A plasma nitridation process is employed for reducing the microwave attenuation in the Josephson microstripline. Improvements of microwave attenuation are about 2 dB for test arrays of 2000, 3000, and 4000 Josephson junctions in a single stripline. We obtained stable quantized voltage steps up to 12 V at 76.4 and 86.8 GHz with step amplitudes of more than 5 /spl mu/A and stability times of more than 5 min. The circuits used 14 648 junctions arranged in 8 parallel paths.
Binary-divided 1 V arrays were fabricated for programmable Josephson voltage standards in close cooperation between INRIM and PTB. The arrays, consisting of 8192 overdamped Nb/Al-AlO(x)Nb SNIS Josephson junctions, were successfully operated at microwave frequencies around 70 GHz. While the characteristic voltage of the junctions ranged from 0.25 to 0.6 mV, the current margins were larger than 1 mA for the Shapiro step n = 1. In addition, flat Shapiro steps of higher order (n = 3 and 4) were generated at increased microwave power levels due to the large characteristic voltage, demonstrating the small parameter spread of the SNIS junctions. Operation at temperatures up to 6-7 K has also been verified, measuring quantized voltages up to 1.25 V on the n = 1 step.