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

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

Published Dec 31, 1994• 0 citations
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Abstract

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.

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Journal of Applied Physics•Oct 15, 1990•64 citations
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.
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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.
We have developed a new fabrication process for integrated Nb/Al/sub 2/O/sub 3//Nb Josephson series arrays using the selective niobium anodization process (SNAP), the image reversal technique (IRT) and lift-off. To avoid chaotic behavior, the critical current of the array was decreased by post-fabrication annealing or the in situ multilayer oxidation process. In the frequency range 70-100 GHz, the array containing 2520 junctions produced stable quantized voltage steps up to 2 V with step widths of 40-100 /spl mu/A and stability times of more than 4 h.>