YBa2Cu3O7-x grain boundary Josephson junctions with a MgO seed layer

A YBa2Cu3O7-x artificial grain boundary Josephson junction was fabricated on to a (110) SrTiO3 substrate employing a MgO seed layer. YBa2Cu3O7-x grows mainly oriented (103) on SrTi03 and (001) on the seed layer. An artificial 4 5° a or b axis tilt or twist boundary can occur according to the orientation of the MgO edge with respect to the (001) in plane direction of the substrate. Josephson junctions of good quality and excellent reproducibility were obtained in microbridges patterned across the grain boundary. Typical features of the phenomenology of high critical temperature superconductor (HTCS) Josephson junction were observed. The maximum value of the kRN product is of the order of 2-3 millivolts at T=4.2 K and of the order of 50 μV at T=77 K respectively. The modulation of the critical current with the external applies magnetic field confirms the Josephson nature of the current in the weak link. © 1997 IEEE.