DocumentCode :
1542748
Title :
Laser trimming of Y-Ba-Cu-O step-edge Josephson junctions
Author :
Adam, R. ; Kula, W. ; Sobolewski, R. ; Murduck, J.M. ; Petriette-Hall, C.
Author_Institution :
Dept. of Electr. Eng., Rochester Univ., NY, USA
Volume :
7
Issue :
2
fYear :
1997
fDate :
6/1/1997 12:00:00 AM
Firstpage :
2997
Lastpage :
3000
Abstract :
We report our studies on the laser-induced permanent changes in electrical transport of YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) step-edge Josephson junctions. The junctions were fabricated from 200-nm-thick YBCO films deposited by laser ablation onto 300-nm-high steps etched in LaAlO/sub 3/ substrates. Laser annealing was performed in-situ by illuminating the junctions at 50 K with a focused Ar-ion laser beam of the intensity up to 10/sup 5/ W/cm/sup 2/. Under optimal irradiation, we observed up to 50% increase of the junction critical current. The modified critical currents were stable and did not change with time or during the helium-to-room-temperature thermal cycling. The annealed junctions exhibited RSJ-like current-voltage characteristics and an enhancement of the I/sub c/R/sub n/ product of up to 50%. The I/sub c/(B) characteristics of the illuminated junctions showed up to 10% shift of the first minima, indicating changes in the junction-barrier area. The I/sub c/(B) simulations, based on the Yanson model of large junction-barrier fluctuations, demonstrated that laser treatment improved barrier homogeneity. We believe that upon laser irradiation, photo-assisted thermal oxygen reordering takes place in the vicinity of the junction barrier, consequently leading to grain boundaries with increased oxygen content and improved junction dc characteristics. An illumination power exceeding 10/sup 5/ W/cm/sup 2/ resulted in oxygen out-diffusion from the junction area and loss of the Josephson-like properties.
Keywords :
Josephson effect; barium compounds; high-temperature superconductors; laser beam annealing; yttrium compounds; LaAlO/sub 3/; LaAlO/sub 3/ substrate; RSJ model; YBCO film; YBa/sub 2/Cu/sub 3/O/sub 7/; Yanson model; barrier fluctuations; critical current; current-voltage characteristics; electrical transport; focused Ar-ion laser beam; grain boundary; laser ablation; laser annealing; laser trimming; normal resistance; oxygen out-diffusion; step-edge Josephson junction; thermal cycling; Annealing; Critical current; Current-voltage characteristics; Etching; Josephson junctions; Laser ablation; Laser beams; Laser modes; Laser transitions; Yttrium barium copper oxide;
fLanguage :
English
Journal_Title :
Applied Superconductivity, IEEE Transactions on
Publisher :
ieee
ISSN :
1051-8223
Type :
jour
DOI :
10.1109/77.621952
Filename :
621952
Link To Document :
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