Structural Studies of YBCO Ramp Josephson Junctions for Rapid Single Flux Quantum Circuits

Ramp-type Josephson junctions with barrier layers of Ga doped PrBa2Cu3O7-δhave been investigated using scanning and transmission electron microscopy. The microstructures have been correlated to the ramp geometry. The junctions exhibited low excess current. This is believed to be due to the uniform thickness of barrier layer deposited on the ion-milled edges. The uniformity of the barrier is presumed to be a result of the smooth ramp, which promoted uniform nucleation and epitaxial growth.