YBa2Cu3O7-delta trilayer junction with nm thick PrGaO3 barrier

We have established a deposition process of high quality a axis oriented YBa2Cu3O7-delta (a-YBCO) and insulating epitaxial PrGaO3 (PGO) films to fabricate a-YBCO/PGO(2.0-3.2 nm)/a-YBCO trilayer junction. The precipitate formation on the bottom a-YBCO was greatly suppressed by the atomic layer modification of the substrate surface with a wet etching and successive atomic layer epitaxy of SrO and BaO atomic layers prior to the YBCO deposition. Crack formation and residual stress in the film due to the thermal expansion mismatch along c axis of YBCO could be eliminated by inserting a buffer layer of-a-YBCO deposited with changing the substrate temperature from 580 to 735 degrees C. The junctions showed a clear hysteresis with its current jump as large as 30%, together with the Fraunhofer diffraction. (C) 1997 American Institute of Physics.