Abstract
We developed a new structure of 45o bi-epitaxial grain boundary junction, i.e. YBCO(780oC)/YSZ and YBCO(780 oC)/YBCO(600 oC)/YSZ. The simple structure has many fabrication benefits, such as controlling the thickness of the step and having an visual endpoint detection for dry etching .It also avoids several drawbacks of the previous structure, for example the presence of a small amount of 45o in-plane rotation of YBCO on MgO, which might cause the junction to be shorted with a large but spurious JC . Besides, the most novel characteristic is the homo-material bi-epitaxy without using the buffer layer and seed layer of heterogeneous material, such as CeO2, YSZ,or MgO layer. The new process is demonstrated to yield better junction quality and higher the critical current density, both are beneficial for many Josephson-junction devices, including SQUID.