A series of YBa2Cu3O7-δ films with various thicknesses was deposited onto YAlO3 (001). The use of X-ray diffraction analysis and transmission electron microscopic imaging revealed the presence of a preferential direction for the alignment of twin boundaries in samples of more than a certain thickness. The thinner films were found to be bi-directionally twinned. Even the thicker samples had only a minor fraction of their volume occupied by domains whose orientation was consistent with the alignment of twin boundaries perpendicular to the main one. The alignment of twin boundaries in the thicker samples was associated with the presence of cracks that ran perpendicularly to them, and were probably caused by them. It was suggested that the stress release which was induced by the cracks inhibited the domain rearrangement that led to bi-directional twinning in thinner films.

On the Possibility of Growing Unidirectionally Twinned YBa2Cu3O7-δ Thin Films on YAlO3. J.J.Robles, A.Bartasyte, H.P.Ng, A.Abrutis, F.Weiss: Physica C, 2003, 400[1-2], 36-42