Integrated High-Temperature Superconductor Radio-Frequency Superconducting Quantum Interference Device Covered with Superconducting Thin Films in Flip-Chip Configuration

摘要

We developed integrated high-temperature superconductor (HTS) rf superconducting quantum interference devices (SQUIDs) with various hole shapes on bicrystal SrTiO_3 substrates. Single-layer YBa_2Cu_3O_(7_x) thin-film technology and bicrystal Josephson junctions were employed to take advantage of a simple fabrication process. The HTS rf SQUID with a hole of 800 x 50 μm~2 had the lowest inductance and showed the best noise characteristics among the tested SQUIDs. The 1/f noise profile of the HTS rf SQUID, which was covered with HTS thin films on the grain boundary and/or the slit of the SQUID in a flip-chip configuration, was dramatically improved in a frequency range of less than 100 Hz.