Formation of edge dislocations in thin epitaxial YBCO films

Transmission electron microscopy (TEM) of thin YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) films on different single-crystalline substrates revealed (by Moire patterns) edge dislocations having non-superconducting cores normal to the substrate. The dislocations are in small-angle boundaries with the average density as high as 10/sup 11/ cm/sup -2/. An extremely high density of dislocations is thought to be the cause of the high critical current density in YBCO epitaxial films. The mechanism for dislocation formation is considered in the framework of a computer model. Computer modeling provided the details of the dislocation arrangement either in domain boundaries or in twist boundaries, depending on the angle of the in-plane misorientation between film and substrate lattices. The model is found to be in goad agreement with experimental data on dislocations in YBCO superconducting films.