A TEM STUDY OF MICROSTRUCTURES OF YBA2CU3O7-X THIN-FILMS DEPOSITED ON LAA1O3 BY LASER ABLATION

The microstructures of YBa2Cu3O7-x thin films deposited by laser ablation on single crystal (001) LaAlO3 substrates have been investigated. The orientation of the YBa2Cu3O7-x layer next to the interface is found to be completely c-perpendicular, with a high degree of epitaxy between the film and the substrate. Misfit dislocations, with a periodic spacing of around 13 nm, are present at the interface. Two distinct interfacial structures are seen in these films. At a film thickness of around 400 nm, nucleation of c-parallel grains occurs, leading to a switchover from a c-perpendicular to a c-parallel microstructure. Amorphous particulates, ejected from the target during processing, lead to the formation of misoriented grains, giving rise to high-angle grain boundaries in the film.