Transmission electron microscopy study of Ag contacts to a- and c-axis oriented YBa2Cu3O7 thin films

Abstract

The interface atomic structure of in situ sputter deposited silver contacts to a- and c-axis oriented thin films of YBa2Cu3O7 (YBCO) was investigated with cross-section transmission electron microscopy (TEM). A structurally disordered interface layer, approximately 25 Å thick, was found for Ag contacts to c-axis oriented films. Electron diffraction analysis provides clear evidence for loss of the 11.7 Å lattice periodicity along the YBCO c-axis in this zone. No such disordered interface layer could be identified in TEM images of Ag contacts to a-axis oriented films. These findings may have important bearing on fabrication of high Tc proximity coupled superconductor/normal metal/superconductor Josephson devices.