Investigation of a Heteroepitaxial YBCO/SrTiO3/YBCO Film

Abstract

The quest for high Tc superconductors like YBa2Cu3O7 for electronic use has been approached by growing heteroepitaxial thin films of YBa2Cu3O7 (YBCO) PrBa2Cu3O7 (PBCO). Films with the structure YBCO/SrTiO3/YBCO (or PBCO- /SrTiO3/YBCO) were grown by laser ablation on a heated single crystalline SrTiO3 substrate. The films were characterised electrically and were then prepared for an investigation in a transmission electron microscope (TEM). The growth rate of YBCO was found to be three times as fast as for the SrTiO3 under the given conditions. The film was well aligned with the substrate except for the outgrowths. Possibly three different forms of outgrowths were found. The outgrowths were characterised by high resolution TEM and electron diffraction. Most of the outgrowths were crystalline while the preliminary investigation suggest that the nucleus of the outgrowths are some amorphous contamination. For thin SrTiO3 layers (≈100nm) most of the outgrowths which nucleated in the lower YBCO layer caused even bigger problems in the upper YBCO layer. The indication by electrical measurement of a bad quality upper YBCO layer and possible short circuit of the two YBCO layers were confirmed by the TEM micrographs.