Characterization of YBa2Cu3O7-x Co-planar Josephson Junctions Using Focused Ion Beam

Yoshihisa SOUTOME  Hidehiro SHIGA  Yoichi OKABE  

IEICE TRANSACTIONS on Electronics   Vol.E81-C   No.10   pp.1538-1543
Publication Date: 1998/10/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Low- and High-Temperature Superconductive Electron Devices and Their Applications)
Category: High-Tc Junction Technology
focused ion beam,  co-planar Josephson junction,  

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YBa2Cu3O7-δ co-planar Josephson junctions by Focused Ion Beam were characterized by changing the thickness of YBa2Cu3O7-δ films. The junctions had the thickness dependence of the characteristics. The characteristics were dominantly divided into two types. One had the I-V curve of a flux-flow junction and a weak magnetic response. The other had the I-V curve of RSJ, the IcRn product from 0. 1 mV to 0. 5 mV at 4. 2 K, and a good magnetic response. The critical current density of the junctions increased exponentially with increasing film thickness. From the observation of the junction surface, the junction length was decreased with increasing film thickness by the horizontal growth of the normally grown YBaCuO. In the thicker film (above 240 nm), the microshorts of the normally grown YBaCuO on the abnormally grown YBaCuO area were observed. It is considered that the main part of Josephson current for the junctions changes from the abnormally grown YBaCuO to microshorts when increased with the film thickness.