Title :
Fabrication of YBaCuO/nonsuperconductive-YBaCuO/YBaCuO co-planar Josephson junction by focused ion beam
Author :
Soutome, Y. ; Yunn Ghee Gheem ; Okabe, Y.
Author_Institution :
Res. Center for Adv. Sci. & Technol., Tokyo Univ., Japan
fDate :
6/1/1995 12:00:00 AM
Abstract :
A thin film of YBa/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) grown on an MgO substrate damaged by a focused ion beam loses superconductivity due to abnormal growth. We have fabricated a YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// co-planar Josephson junction whose coupling region is nonsuperconductive YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grown on an MgO substrate damaged locally by focused ion beam scanning. The I-V characteristic of the junction behaves like a flux flow type. At temperatures from 4.2 K to 60 K, Shapiro steps were observed for the junctions in which the length of the coupling region was from 0.2 /spl mu/m to 1 /spl mu/m. The highest I/sub c/R/sub n/ product of the junction was 5.0 mV. The critical current density decreased exponentially with the junction length. It is considered that nonsuperconductive YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// grown on the damaged substrate works as a normal layer in an S-N-S junction. Also the junction responded to the magnetic field and behaved like an asymmetric dc-SQUID.<>
Keywords :
Josephson effect; barium compounds; critical current density (superconductivity); flux flow; focused ion beam technology; high-temperature superconductors; ion beam applications; superconducting device testing; superconducting junction devices; yttrium compounds; 0.2 to 1 mum; 4.2 to 60 K; I/sub c/R/sub n/ product; MgO; MgO substrate; S-N-S junction; Shapiro steps; YBa/sub 2/Cu/sub 3/O/sub 7/; YBa/sub 2/Cu/sub 3/O/sub 7/(-/spl delta/) thin film; YBaCuO/nonsuperconductive-YBaCuO/YBaCuO; asymmetric dc-SQUID; coplanar Josephson junction; coupling region length; critical current density; damaged substrate; flux flow type I-V characteristics; focused ion beam fabrication; focused ion beam scanning; magnetic field modulation; microwave irradiation; normal layer; Critical current density; Fabrication; Ion beams; Josephson junctions; Optical coupling; Substrates; Superconducting thin films; Superconductivity; Temperature; Yttrium barium copper oxide;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
