Preparation and characterization of a-axis oriented NdBa2Cu3O7-delta/PrBa2(Cu,Co)(3)O7-delta/NdBa2Cu3O7-delta planar junctions

We report on well characterized a-axis trilayers made of NdBa2Cu3O7-delta a nd PrBa2(Cu,Co)(3)O7-delta films with smooth surface morphology and high cr ystallinity. The thin films were grown on (100) SrTiO3 substrates by rf + d e hybrid sputtering. X-ray diffraction and Rutherford backscattering spectr ometry analyses provided evidence of well-equilibrated and relaxed crystal. Planar junctions were fabricated from these a-axis oriented NdBa2Cu2O7-del ta/PrBa2 (Cu,Co)(3)O7-delta/NdBa2Cu3O7-delta trilayers. The current-voltage characteristics exhibited Josephson current. Well developed Shapiro steps for 7-20 GHz microwave irradiation were observed. The dependence of the max imum amplitude of the Josephson current under applied magnetic field made e vident spatial variations of the critical current over the PrBa2(Cu,Co)(3)O 7-delta barrier layer. The current-voltage characteristics were qualitative ly consistent with the resistively-shunted-junction model. (C) 2000 Elsevie r Science B.V. All rights reserved.