TEM Study of La-Doped ErBCO Layer Deposited on Ramp-Surfaces

We have fabricated high-Tc SQUIDs consisting of ramp-edge-type Josephson junctions and oxide multilayer structures. Preparation of a superconducting layer with c-axis orientation on ramp-surfaces is one of key issues. We report transmission electron microscope (TEM) study of the La0.1Er0.95Ba1.95Cu3Oy (L1ErBCO) layer prepared by a pulsed laser deposition (PLD) method on ramp-surfaces made of SrSnO3 (SSO) and SmBa2Cu3Oy (SmBCO). Inclusion of grains with aaxis orientation was seen in L1ErBCO on SSO. After observation of various samples, we found a tendency that the number of a- oriented grains was reduced by depositing L1ErBCO on shallower ramps. On the other hand, successful growth of the layer with c-axis orientation was observed in the L1ErBCO layer on the SmBCO ramp, suggesting that the SmBCO promoted the c-axis growth of L1ErBCO. Electron diffraction indicated that in-plane orientation was also achieved for the L1ErBCO grains on SmBCO.