Electron Optical Studies of Barium Titanate Single Crystal Films

Abstract

Thin single crystal films of barium titanate prepared by chemical thinning of single crystal plates are studied by transmission electron microscopy and electron diffraction. The films as thin as 1000 Å are found to have the same lattice parameters as the bulk crystals, giving no evidence for the existence of the anomalous surface layer proposed by Känzig et al. The surface of barium titanate is found to change substantially when heated above 500°C in air and vacuo, invalidating their evidence for an unusually high Curie temperature of their anomalous surface layer. Ferroelectric 90° and 180° domains are observed by electron microscopy. The contrast of 90° domains is simple diffraction contrast. The contrast of 180° domains is due to the failure of Friedel's law, which is known to be possible to take place in electron diffraction by dynamical diffraction effect. Dislocations, tracks of fission fragments from uranium and their interaction with domains are observed.