Threading dislocations in Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 epitaxial films grown on (001) LaAlO3 substrate

The microstructures of Ba0.7Sr0.3TiO3/La0.7Sr0.3MnO3 (BST/LSMO) thin films epitaxially grown on (001) LaAlO3 substrate by pulsed laser deposition were investigated by transmission electron microscopy (TEM) and related techniques. Both cross-sectional and plan-view TEM specimens were studied. The predominant defects in the films are a high density of threading dislocations (TDs) perpendicular or quasi-perpendicular to the substrate surface. Diffraction contrast and high-resolution transmission electron microscopy (HRTEM) techniques reveal that the TDs are mostly pure-edge-type with Burgers vectors b=<100> or <110>. There are a few TDs of screw character, and convergent beam electron diffraction (CBED) analysis shows the screw component of their Burgers vectors is ±[001]. The formation mechanisms of the TDs are discussed.