Fabrication of superconducting d-wave dot embedded in an s-wave matrix

When a d-wave superconducting dot (d-dot) is embedded in an s-wave superconductor matrix, a half flux quantum vortex is expected to appear spontaneously at four corners of the d-dot without applying an external magnetic field. First, we have prepared c-axis oriented YBa2Cu3O7 (d-wave superconductor) thin films by pulsed-laser ablation deposition on c-axis oriented SrTiO3 single-crystal substrates. We have fabricated resist-coated YBa2Cu3O7 square islands by using an electron beam lithography and an electron cyclotron resonance etching. Then, we have deposited Pb (s-wave superconductor) film on the fabricated YBa2Cu3O7 thin film, and removed extra Pb and resist films on the YBa2Cu3O7 islands by a lift-off technique. Magnetic field distribution on superconducting d-dot has been measured by using a SQUID microscope in zero fields.