Ferroelectric 90° domain structure in a thin film of BaTiO3 fine ceramics observed by 300kV electron holography

We observed 90° ferroelectric domain structure in a thin film of BaTiO3 by 300kV electron holography, especially paying attention to beam-induced influence on the polarization and diffraction effect. The beam-induced influence was minimized by recording holograms on high-resolution films at low electron-optical magnification. As for the diffraction effect, we chose such an orientation of the specimen as to minimize the corresponding amplitude contrast. Furthermore, to minimize any phase shifts that are not intrinsic to ferroelectricity, such as the mean-inner potential of the material or the electron-beam-induced charging under the illumination condition, we calculated the difference between phase images taken below and above the Curie temperature of the material to obtain a consistent value for the spontaneous polarization.