Polarity determination of ferroelectric LiNbO3 crystals and BiFeO3 thin films by the convergent beam electron diffraction technique

The applicability of various convergent beam electron diffraction (CBED) methods to the polarity determination of LiNbO3 crystals in the space group R3c was examined. We show that the method of zone-axis CBED combined with dynamical simulation is applicable to the polarity determination of LiNbO3. The effects of the zone axis, the specimen thickness and the displacement of the homopolar atom on the polarity determination were studied. This method was also successfully applied to the polarity determination of a multiferroic BiFeO3 film deposited on a (111)Pt/TiO2/SiO2/Si substrate by pulsed laser deposition. It shows that about 30% of the grains in the BiFeO3 film are grown along the positive polar direction.