Growth of YBa₂Cu₃O_7-δ on co implanted substrates

We have studied films of YBa₂Cu₃O_7-δ (YBCO) grown on SrTiO₃ substrates, which were implanted with high doses of Co (1 X 10¹⁶-5 X 10¹⁷ ions/cm² at 100 keV). The indirect modification of YBCO by local ion implantation of Co into the substrate is investigated to evaluate the feasibility of a new planar technology for the fabrication of Josephson junctions. The modified YBCO might become a barrier region of a Josephson junction. We found a strong diffusion of the implanted Co ions out of the substrates into the YBCO films during the deposition process, forming YBa₂Cu_3-xCo_xO_7-δ. Our EDX and SNMS analyses show that the Co concentration x is homogeneous across the films. YBa₂Cu_3-xCo_xO_7-δ is well known to be an excellent barrier material for SNS-type Josephson junctions. Using a 1.4 μm thick photoresist mask, we have locally implanted Co into the substrates to study the lateral diffusion of Co into the YBCO film above the non-implanted region. We performed EDX analysis on cross-sectional TEM samples and found strong lateral diffusion of Co from the implanted substrate within the YBCO film located above the non-implanted region.