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 (1 0 0) 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 °C 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.