INTERFACE FABRICATION OF YBA2CU3OY RAMP-EDGE JUNCTION WITH PRBA2(CU1-XCOX)(3)O-Y BARRIER LAYER IN ENHANCED OXIDIZING ATMOSPHERE

Thin film growth and fabrication process for YBa2Cu3Oy/PrBa2(Cu1-xCox) (3)O-y/YBa2Cu3Oy ramp-edge type junctions have been studied. Preferabl e conditions to maintain a stable ramp surface were investigated by co mparative measurements of the surface morphology of ramp-edge structur es of epitaxial bilayers of SrTiO3/YBa2Cu3Oy annealed at various condi tions of temperature and oxygen partial pressures. The stability of th e ramp-edge surfaces was discussed in terms of the equilibrium reactio n of YBa2Cu3Oy, and the degradation of surfaces by damages through the fabrication process was concluded to be the main factor for the decom position at high temperatures. A two-step etching technique and anneal ing with atomic oxygen activated by microwave enabled the ramp surface s to be maintained quite stable even at the deposition temperature of barrier layers. The ramp surface of YBa2Cu3Oy annealed under 4 X 10(14 ) cm(-2) s(-1) activated oxygen flux gave no evidence of decomposition at 800 degrees C except for a slight decrease in thickness in the YBa 2Cu3Oy layer. In ECR (electron cyclotron resonance)-processed junction s, resistively shunted junction (RSJ) type current-voltage characteris tics were observed and the magnetic field dependence of the critical c urrent showed a Fraunhofer pattern. (C) 1998 Elsevier Science B.V. All rights reserved.