Preparation of CeO2\SrTiO3 bilayers as a barrier material for SIS Josephson junctions

CeO2, SrTiO3 (STO) and CeO20\STO as barrier materials were deposited on c-axis-oriented EuBa2Cu3O7-delta (EBCO) films with T-c endpoints (T-ce) above 90 K, and the effects on the superconducting properties of the lower-layer EBCO were examined. For several 100-Angstrom -thick CeO2 Sputter depositions, the EBCO did not deteriorate, but the CeO2 film contained many pinholes. On the other hand, a 50-Angstrom -thick STO deteriorated an EBCO film to T-ce = 52 K. When a CeO2\STO multi-barrier was deposited, the deterioration of EBCO was reduced, and the generation of pinholes was suppressed. Activated oxygen plasma treatment was effective for the recovery of EBCO covered by a CeO2\STO multibarrier. In the differential characteristics of an I-V curve from a junction with a CeO2 (50 Angstrom)\STO (200 Angstrom) multibarrier, a gap structure was observed. (C) 2001 Elsevier Science B.V. All rights reserved.