Effect of nonstoichiometric defects on antiparallel domain formation in LiNbO3

The structures of inverted nanodomains in LiNbO(3) crystals were investigated using atomic force microscopy (AFM) combined with piezoresponse force microscopy and atomic force acoustic microscopy. The acoustic and AFM topographic images reflected in domain structures with polarization orientation revealed that unexpected antiparallel domains randomly exist in inverted nanodomains in congruent LiNbO(3) but not in near-stoichiometric one. The Gibbs free energy change Delta G associating with the internal field E(int) in congruent LiNbO(3) was discussed. We propose that nonstoichiometric defects, which caused E(int) during polarization reversal, play a key role in formation of antiparallel domains in congruent LiNbO(3) crystals. (c) 2007 American Institute of Physics.