Role of misfit dislocations in ferroelectric thin films CH031

We present a systematic study on the nanoscale chemistry around misfit dislocations (MDs) in ferroelectric thin films, to attribute their effects on the reported degradation of physical properties.[1] The quality of the interface was examined using High Resolution Transmission Electron Microscopy (HRTEM) investigations, acquired on the following model heterostructures -(a) PbZr _0.52Ti_0.48O₃ (PZT 52/48) with a very large misfit, and hence high density of dislocations, (b) an excellent lattice-matched PbZr_0.20Ti_0.80O₃ | (PZT 20/80) and (c) BaTiO₃ (BTO). All three films were deposited on SrRuO₃ buffered | SrTiO₃. We map the chemical changes across the interfaces, around the MDs via Energy Dispersive X-Ray Spectroscopy (EDS) and Energy-Filtered TEM (EFTEM). In the case for an interface with high density of MDs there is a significant mixing of chemical species; particularly Pb from the PZT is found in the electrode layer. Hence, the severe lattice distortion at the core of the dislocations have a profound impact on the local chemistry; by changing electronic structure as well as chemical species at the atomic interface. We postulate that these local chemical changes drastically affect important physical properties such as, the polarization, piezoelectric and the dielectric response.