Microstructures of YBa1.85Eu0.15Cu3O7-delta superconducting films grown on SrTiO3 and YSZ substrates

A detailed atomic scale microstructure analysis of Eu-doped YBa1.85Eu0.15Cu3O7-delta (YEBCO) thin films with 100 nm in thickness has been carried out by a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Interesting regular-like arranged network of nanoscale undulations is observed on the surface of YEBCO film on (0 0 1) SrTiO3 substrate. TEM image clearly indicates that the film is always c-axis oriented, but lots of natural precipitates of Y2O3 are involved both at the interface and deep in the film. Desirable size and number density of Y2O3 are thought to be important for acting as efficient flux pinning centers. In the case of YEBCO film on (0 0 1) yttrium stabilized ZrO2 (YSZ) substrate, few cracks and outgrowths appear due to much larger lattice mismatch and dissimilar crystal structure between the film and substrate, but surface quality is still much better compared to the parent YBaCu3O7-delta film. Besides, highly textured BaZrO3 layer at the interface and alpha-axis grains with small dimensions in the film are formed. Interface stability of two kinds of films studied, namely YEBCO/STO and YEBCO/YSZ, is also assessed comprehensively by first principle calculations. (C) 2010 Elsevier B.V. All rights reserved