Microstructural study in heteroepitaxial YBa/sub 2/Cu/sub 3/O/sub 7//Nd/sub 2/CuO/sub 4/ multi-layers by using electron microscopy

Neodymium copper oxide Nd/sub 2/CuO/sub 4/ (NCO) has been applied as a buffer material to improve the epitaxy of YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) thin films on reactive substrates and as a potential barrier to construct multi-layer junctions. The microstructures and interfaces in heteroepitaxial Nd/sub 2/CuO/sub 4//YBCO multi-layer have been characterized by using an electron microscopy. Cross-sectional images obtained on a transmission electron microscopy (TEM) revealed an atomically sharp boundary between layers, underlining the excellent compatibility of NCO with YBCO. No chemical reaction occurred between film and substrate. It was found that all layers grow highly epitaxially with their c-axis perpendicular to the substrate surface. On the other hand, various defects such as mis-oriented grains and stacking faults were found near the interfaces.