FORMATION OF EDGE DISLOCATIONS IN THIN EPITAXIAL YBCO FILMS

Transmission electron microscopy (TEM) of thin YBa2Cu3O7-delta (YBCO) films on different single-crystalline substrates revealed (by Moire pa tterns) edge dislocations having non-superconducting cores normal to t he substrate. The dislocations are in small-angle boundaries with the average density as high as 10(11)cm(-2). An extremely high density of dislocations is thought to be the cause of the high critical current d ensity in YBCO epitaxial films. The mechanism for dislocation formatio n is considered in the framework of a computer model. Computer modelin g provided the details of the dislocation arrangement either in domain boundaries or in twist boundaries, depending on the angle of the in-p lane misorientation between film and substrate lattices, The model is found to be in good agreement with experimental data on dislocations i n YBCO superconducting films.