Ferroelectric domain structure of discrete PbTiO3 nanograins

The domain structure of discrete PbTiO3 nanograins deposited on a platinized substrate by chemical solution deposition was investigated by piezoresponse force microscopy. It was found that the as-grown domain structures transformed from symmetric lamellar multidomains to asymmetric two domains (a–a domains) as the grain size decreased from 200 to 40 nm. Nanograins smaller than 60 nm exhibited a metastable domain state (curved domain walls and asymmetric domains), indicating the contribution of inhomogeneous elastic field to the equilibrium domain structures. When the grain size was further decreased to 20 nm, the piezoresponse image could not elucidate its single domain unambiguously due to the resolution limit. Nevertheless, it was determined that the grain size of monodomain was less than 40 nm.