Title :
Overdamped NbN junctions with Nb/AlOx/Nb multilayered barriers
Author :
Akaike, Hiroyuki ; Iwai, Takao ; Ninomiya, Yasunori ; Nakamura, Kentaro ; Fujimaki, Akira ; Hayakawa, Hisao
Author_Institution :
Dept. of Quantum Eng., Nagoya Univ., Japan
fDate :
3/1/2001 12:00:00 AM
Abstract :
This paper describes electrical characteristics of NbN junctions with Nb/Al2O3-Al/(Nb) multilayered barriers. The junctions show overdamped behavior at 10 K because of Nb working as a normal layer, which enables us to use them as basic elements in single flux quantum (SFQ) circuits. The junctions, with critical current densities Jc´s up to 3.4 kA/cm2 and characteristic voltages Vc´s up to 0.20 mV, were obtained by changing the film thicknesses of lower and upper Nb layers and the Al oxidation conditions when using a conventional batch-type sputtering system. The run-to-run variations of Jc and Vc were the maximum-to-minimum spreads of ±32% and ±4.3%, respectively. On the other hand, a Vc of 0.70 mV and a Jc of 13 kA/cm2 were obtained for the junction fabricated by the ultrahigh-vacuum sputtering system. These results show that NbN/Nb/AlOx/Nb/NbN junctions have high potential and can be applicable to high performance 10 K SFQ circuits
Keywords :
alumina; aluminium; critical current density (superconductivity); niobium; niobium compounds; sputtered coatings; superconducting logic circuits; superconducting superlattices; type II superconductors; 0.2 mV; 0.7 mV; 10 K; Al oxidation conditions; Nb/Al2O3-Al/Nb multilayered barriers; Nb/AlOx/Nb multilayered barriers; NbN-Nb-Al2O3-Al-Nb-NbN; NbN/Nb/AlOx/Nb/NbN junctions; SFQ circuits; batch-type sputtering system; characteristic voltages; critical current densities; electrical characteristics; film thickness; normal layer; overdamped NbN junctions; single flux quantum circuits; ultrahigh-vacuum sputtering system; Artificial intelligence; Controllability; Critical current density; Integrated circuit reliability; Magnetic circuits; Niobium; Oxidation; Reproducibility of results; Sputtering; Virtual colonoscopy;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
