RHEED study of modified barrier for c-axis oriented YBaCuO trilayer junctions

We have studied a formation process of the modified barrier for YBaCuO trilayer junctions by using reflection high-energy electron diffraction (RHEED). c-axis oriented YBaCuO films were prepared on (100) oriented MgO substrates by using a co-evaporation method with pure O-3 vapor. The modified barriers were formed by an Ar plasma bombardment with an acceleration voltage of 1 kV and by a subsequent annealing with various gas conditions. The film surface exhibited a hallo pattern after Ar plasma bombardment at room temperature. As the film was annealed at 400, 600 and 710 degreesC under the vacuum condition, the RHEED pattern was drastically changed to weak spots, clear spots with a streak pattern, and a spotty pattern. The film annealed in the ozone vapor condition, on the other hand, showed a streak pattern. (C) 2002 Elsevier Science B.V. All rights reserved.