Transmission electron microscopy studies of superconducting Y-Ba-Cu-O films prepared by laser deposition

The polycrystalline structure of pulsed-laser deposited Y-Ba-Cu-O thin films was studied using transmission electron microscopy. Many grains of the superconducting films on (001) SrTiO3 substrates had the c axis normal to the surface, while grains on (110) facets had their c axis oriented preferentially along the interface. Observation of an amorphous layer of thickness ∼6 nm at some oriented grain-substrate interfaces suggests that the amorphous layer is formed subsequent to the formation of the crystalline structures. Surface ridges were found to facilitate the formation of triple points where the grain boundaries between nonepitaxial grains were pinned.