Growth of YBa 2Cu 3O 7−δ on Co implanted substrates

Abstract

We have studied films of YBa 2Cu 3O 7−δ (YBCO) grown on SrTiO 3 substrates, which were implanted with high doses of Co (1 × 10 16-5 × 10 17 ions/cm 2 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 YBa 2Cu 3− x Co x O 7−δ. Our EDX and SNMS analyses show that the Co concentration x is homogeneous across the films. YBa 2Cu 3− x Co x O 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.