Microstructure of epitaxial YBa2Cu3O7−x thin films grown on LaAlO3 (001)

We report a microstructural investigation of the epitaxial growth of YBa2Cu3O7−x (YBCO) thin films on LaAlO3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c axis normal to the surface) and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35–200 nm thick. In 35 nm YBCO films annealed at 850 °C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy.