A TEM study of microstructures of YBa2Cu3O7−x thin films deposited on LaAlO3 by laser ablation

Abstract

The microstructures of YBa₂Cu₃O_7−x thin films deposited by laser ablation on single crystal (001) LaAlO₃ substrates have been investigated. The orientation of the YBa₂Cu₃O_7−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, and, and-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.