Co-planar Josephson Junction Using Nonsuperconductive YBaCuO Formed on Very Locally Damaged Substrate by FIB

Yunnghee KIM  Yoshihisa SOUTOME  Hiroshi KIMURA  Yoichi OKABE  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E78-C   No.5   pp.471-475
Publication Date: 1995/05/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Superconducting Electronics and Its Applications)
Category: Three terminal devices and Josephson Junctions
Keyword: 
YBaCuO,  Josephson junction,  Planar junction,  Shapiro steps,  Focused Ion Beam,  

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Summary: 
A YBaCuO-Nonsuperconductive YBaCuO-YBaCuO coplanar Josephson junction has been fabricated, using Nonsuperconductive YBaCuO thin film deposited on an MgO(100) substrate with intentional and very local damage which was created by Focused Ion Beam. The YBaCuO grown on the damaged section of the substrate turned out to be non-superconductor, due to implanted Ga ions and the change in the crystal quality, facilitating formation of an S-N-S junction. We found the important fact that the critical current density decreased exponentially with inverse of the junction length which was changed from 0.2 to 1 µm, and that Ga ion was detected in the thin films of the junctions, and that the thin films of the junctions were formed by a mixture of an amorphous, a polycrystal and a crystal, which is confirmed by Transmission Electron Diffraction. And the damaged substrate gave rise to Ga segregation and the mixed crystal, which played an very important role to form the normal metallic YBCO thin film of the Josephson junction. All these facts are related with the S-N-S junctions.