Inductance Investigation of YBa2Cu3O7−δ Nano-Slit SQUIDs Fabricated With a Focused Helium Ion Beam

Focused helium ion beam material modification is ideally suited for the fabrication of YBa2Cu3O7-δ (YBCO) Josephson junctions and superconducting feature sizes down to the nanoscale. We report the fabrication and measurement of YBCO nano-slit SQUIDs and study how scaling the dimensions of the SQUID body and electrodes influences the electrical properties. Sixteen nano-slit SQUIDs with different width and length were fabricated from a single-layer 25-nm-thick YBCO film. The experimental results yield an estimation of the sheet inductance to be ~4 pH/□ and a penetration depth of ~180 nm. The temperature dependence of the inductance agree well with an impurity scattering model, indicating that the TC of the film was ~82 K, and the ratio between geometric inductance and kinetic inductance at 0 K was ~0.8. These results provide solid basis for the design of high-performance, high-TC micro-SQUID magnetometers.