SURFACE CRYSTALLOGRAPHIC STRUCTURE COMPATIBILITY BETWEEN SUBSTRATES AND HIGH T(C) (YBCO) THIN-FILMS

A review and some case studies on the interatomic distances of candidate substrates in comparison to the high T(c) superconductor (HTSC) phase YBa2Cu3O7-delta (YBCO) is presented, in an attempt to enhance the basis for substrate selection for YBCO film epitaxy. This preliminary study was carried out by examining a variety of interatomic distances in the structure rather than merely matching the lattice parameters. Interatomic structure matching planes of selected YBCO orientations in contact with substrates were identified. The surface termination of the substrate was found to be a crucial parameter in determining the oriented or epitaxial growth. Possible composition dependence of the orientation of the films at the nucleation stage was also anticipated depending on the comparison. Several currently most commonly used substrates are discussed in some detail.