Characterization of YBa_2Cu_3O_<7-x> Co-planar Josephson Junctions Using Focused Ion Beam(Special Issue on Superconductive Electron Devices and Their Applications)

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YBa_2Cu_3O_<7-δ> co-planar Josephson junctions by Focused Ion Beam were characterized by changing the thickness of YBa_2Cu_3O_<7-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 I_cR_n product from 0.1mV to 0.5mV at 4.2K, 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 240nm), 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 incrased with the film thickness.
社団法人電子情報通信学会の論文
1998-10-25