Misfit strain relaxations of (101)-oriented ferroelectric PbTiO 3 /(La, Sr)(Al, Ta)O 3 thin film systems

High-index ferroelectric thin films show excellent dielectricity, piezoelectricity and switching behaviors. Understanding the misfit strain relaxation behavior may prove beneficial to gaining insights into the high-quality growth of high-index ferroelectric films. In this study, ferroelectric PbTiO 3 thin films were deposited on the (101)-oriented (La, Sr)(Al, Ta)O 3 substrate by pulsed laser deposition and were investigated using (scanning) transmission electron microscopy. Two types of misfit dislocations with line directions of 〈111〉 and [010] were found at the interface. The 〈111〉 dislocation exhibited Burgers vectors of a [011] or $a\left[ {0\bar{1}1} \right]$ , while the [010] dislocation featured Burgers vectors of $a\left[ {\bar{1}01} \right]$ . The former might be generated by gliding, and the latter by climbing. We propose that the misfit strain relaxation in this film system basically results from the formation of dislocations and the residual misfit strain is relaxed via the formation of 90° ac domains.