A transmission electron microscopy study of dislocation substructures in PLD-grown epitaxial films of (Ba,Sr)TiO 3 on (001) LaAlO 3

Epitaxial Ba 0.6Sr 0.4TiO 3 films were grown onto (001) LaAlO 3 by pulsed-laser deposition, and the dislocation structures of the films were investigated using transmission electron microscopy. Misfit dislocations with a periodicity of about 7 nm and Burgers vectors b = a〈100〉 were observed at the interface. High densities of threading dislocations was present in the films with Burgers vector b = a〈100〉. The observations reveal that threading dislocations are not generated as the result of half-loop climb from the deposit surface as proposed previously, but are instead formed when misfit dislocations are forced away from the interface during island coalescence.