The structures of inverted nano-domains in LiNbO3 crystals were investigated using atomic force microscopy combined with piezoresponse force microscopy and atomic force acoustic microscopy. The acoustic and atomic force microscopy topographic images reflected in domain structures with polarization orientation revealed that unexpected antiparallel domains randomly exist in inverted nanodomains in congruent LiNbO3 but not in near-stoichiometric one. The Gibbs free energy change ∆G associating with the internal field Eint in congruent LiNbO3 was considered. It was proposed that non-stoichiometric defects, which caused Eint during polarization reversal, played a key role in the formation of antiparallel domains in congruent LiNbO3 crystals.

Effect of Nonstoichiometric Defects on Antiparallel Domain Formation in LiNbO3. X.Liu, K.Kitamura, K.Terabe, H.Zeng, Q.Yin: Applied Physics Letters, 2007, 91[23], 232913