A Transmission Electron Microscopy Study of Dislocation Substructures in PLD-grown Epitaxial Films of (Ba,Sr)TiO_3 on (001) LaAlO_3

摘要

Epitaxial Ba_(0.6)Sr_(0.4)TiO_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.