Diffraction contrast analysis of 90° and 180° ferroelectric domain structures of PbTiO₃thin films

The ferroelectric domain structure of a PbTiO3 thin film on (100) SrTiO3 has been investigated by transmission electron microscopy (TEM). Two types of a-domain were found: one extended through the film to the surface and another comprised small a-domains confined within the film. Dark-field TEM (DFTEM) observation revealed that 180° domains formed near the substrate and stopped their growth 100 nm away from the substrate. The DFTEM observation also revealed that 90° domain boundaries had head-to-tail structures. To confirm the polarization direction obtained by experiments, diffracted intensities under a two-beam condition were simulated using the extended Darwin–Howie–Whelan equations. On the basis of the obtained results, a ferroelectric domain structure model of PbTiO3 thin films on SrTiO3 is proposed.